1. ATM Fundamentals ýLearn the basics of ATM
2. Communication Tutorials from the University of New Hampshire Interoperability Lab ýThis site delivers a host of communication design tutorials. Topics include MPLS, Gigabit Ethernet/10 Gigabit Ethernet, WLANs, IP, ATM, ADSL, DOCSIS, and more
3. DWDM Overview ýA look at how DWDM works and why itýs important
4. DWDM Tutorial ýCienaýs look at the inner workings of DWDM
5. Gigabit Ethernet Overview -10 Gigabit Ethernet Allianceýs look at Gigabit Ethernet technology
6. Next-Gen Backplanes Overview ýSite providing technical overviews of some hot new backplane architectures
7. Optical Switching Tutorial ýTechnical look at optical switching
8. Resilient Packet Ring RPR White Paper ýTake a close look at the emerging RPR spec
9. SONET Tutorial ýTechnical overview of the Sonet specifications
Source:www.commsdesign.com/centers/optical_tutorials.html
Thursday, October 29, 2009
Wednesday, October 28, 2009
Optical Networking
What Is Optical Networking?
As the name suggests, optical networks form a class of networks where optical, rather than electronic, components are the building blocks of the network. Compared to metallic cable, fiber optic systems offer greater bandwidths, lower attenuation, and no crosstalk or electrical interference. Those advantages have led to the dramatic growth of fiber optic systems worldwide. Today, nearly all long-haul telecommunications depend on the use of optical networks for their large capacity and robust performance.
Standards
Standards for fiber optic cable and other optical components have been developed over the last 20 years primarily by the American National Standards Institute (ANSI) and the International Telecommunications Union (ITU). Standards for fiber optic transmission have been developed initially in North America under the name Synchronous Optical Network (SONET) and later by the ITU using the name Synchronous Digital Hierarchy (SDH).
Historical Milestones
* 1958: Discovery of laser
* Mid-60s: Demonstration of guided wave optics
* 1970: Production of low-loss fibers, which made long-distance optical transmission possible
* 1970: Invention of semiconductor laser diode, which made highly refined optical transceivers possible
* 70s-80s: Use of fiber in telephony: SONET/SDH standards from ITU
* Mid-80s: LANs/MANs: broadcast-and-select architectures
* 1988: First trans-Atlantic optical fiber laid
* Late-80s: Development of EDFA (optical amplifier), which greatly alleviated distance limitations
* Mid/late-90s: DWDM systems explode
* Late-90s: Intelligent Optical networks
* 20?? Soliton transmission with optical TDM
Optical Networking: Why?
The “traditional" networks consist, for the most part, of a collection of electronic switches interconnected by point-to-point optical fiber links, which can span local, metropolitan, or wide area networks. To accommodate continually increasing demand for bandwidth and flexibility, such networks are being enhanced by adding more fibers and switches, increasing the bit rate per fiber, and upgrading the switches' size, throughput and functionality. Such enhancements eventually lead to very large and complex networks that are difficult and expensive to construct, operate and maintain. Recent and emerging advances in optical technology promise revolutionary all-optical networks capable of providing improved economy, flexibility and robustness while still capable of making use of the large existing fiber base.
Principles and Operation
An optical fiber is a cylindrical waveguide made of two transparent materials each with a different index of refraction. The two materials, usually high-quality glass, are arranged concentrically to form an inner core and an outer cladding. Different entry angles of the light source result in multiple modes of wave propagation. Propagation can be restricted to a single mode by using a small-diameter core.
The choice between single-mode and multimode fiber depends on the desired repeater spacing or transmission rate; single mode is the preferred choice for long-haul or high data-rate systems. The earliest form of multimode fiber was the step-index, where the core has a uniform index of refraction and the concentric cladding also has a uniform but lower index. In this case the propagation velocity within the core is constant, so that rays traveling a longer path arrive behind rays traveling a shorter path, thus producing pulse spreading, or dispersion. These dispersive effects may be remedied by constructing a fiber whose refractive index increases toward the axis, with a resulting refractive index profile that is parabolic. With a graded-index fiber, rays that travel longer paths have greater velocity than rays traveling the shorter paths due to decreasing refractive index with radial distance. The various modes then tend to have the same arrival time, such that dispersion is minimized and greater bandwidths become possible for multimode fibers.
Within the spectrum available in a fiber optic system, there are three low-loss windows, at wavelengths of approximately 850, 1300, and 1550 nm. Early applications of fiber optics for communications applications were based on the short-wavelength band of roughly 800 to 860 nm. Operation in the longer-wavelength bands, particularly at 1300 and 1550 nm, is attractive because of improved attenuation and dispersion characteristics at these wavelengths. Typically today the shorter-wavelength band is used for short-haul, low data rate systems, and the longer-wavelength bands are applied to long-haul, high data rate systems. Special fibers have been developed that shift the minimum dispersion to about 1550 nm to take advantage of lower attenuation as well as minimum dispersion. These fibers are called dispersion-shifted fibers, and are important to single-mode fiber applications.
Low-data rate, short-haul fiber optic systems tend toward multimode cable, LED transmitters, and PIN diode receivers. High-data rate, long-haul systems tend toward single-mode cable, laser diode transmitters, and avalanche photodiode receivers. Latest generation fiber optic systems have introduced innovations that have significantly improved the bandwidth and repeater spacing possible. Coherent detection via either homodyne or heterodyne techniques allows much greater bandwidths to be realized. Several wavelengths can be transmitted simultaneously in wavelength-division multiplexing, analogous to frequency-division multiplexing used in telephony. Optical amplifiers are now available that eliminate electronics and instead use specially doped fiber or semiconductor laser devices. The use of optical amplifiers will allow a fiber optic system to be upgraded in bit rate without replacement of the repeaters. Optical amplifiers have also been used to achieve ultra-long distances via soliton transmission, which is the transmission of an idealized pulse without loss of pulse shape.
Types of Optical Networks
Optical networks may be classified in several ways. Opaque optical networks include optical-electronic-optical (OEO) conversion, while in all-optical networks each connection is totally optical (or transparent) except at the end nodes.
Optical networks may be single wavelength or multiple-wavelengths (WDM). The use of SONET/SDH with a single carrier is a typical example of an opaque, single-wavelength optical network.
Finally, optical networks may be passive or active. A passive optical network (PON) is an all-optical network that utilizes only passive optical components, e.g., fibers, directional couplers, star couplers, wavelength routers, wavelength multiplexers, and filters. The intended applications are fiber-in-the-loop (local loop) and fiber-to-the-home (FTTH). The optical signaling formats in PONs can employ wavelength-division multiplexing (WDM), subcarrier multiplexing, time-division multiplexing (TDM) or any combination of these. An active all-optical network (AON) enables each of a large number of optical WDM channels (wavelengths) to propagate from source to destination over long distances and high bit rates without optical-to-electronic format conversion within the network.
Optical Network Architecture
There are two standard optical architectures, linear and ring, both of which can provide network protection and restoration of services. SONET rings are the most widely deployed architecture. They can be thought of linear networks folded back to create a loop or ring. But unlike linear architectures, rings are designed to guarantee automatic restoration of services when cable or nodes fails, by use of loops around the failed component. Because of this automatic protection against failures, these rings are called self-healing. There are several SONET ring architectures that depend on the number of fibers, transmission direction, and level of switching protection.
Originally developed in the United States, the SONET standard was adopted by the ITU-T but renamed as the Synchronous Digital Hierarchy (SDH). These standards provide a complete set of specifications to allow national and international connections at various levels. Optical interfaces are defined that provide a universal fiber interface and permit mid-span interconnection of different vendor equipment. A standardized signal structure allows any existing hierarchical rates (for example, DS-1, DS-3, E-1, and E-3) to be accommodated. Overhead within the SONET signals facilitate synchronization, add and drop multiplexing, electronic switching, performance monitoring and network management of the composite and tributary signals. The SONET hierarchy is built on synchronous multiplexing of a basic SONET rate of 51.84 Mb/s, so that higher SONET rates are simply N x 51.84 Mb/s. The basic signal structure provides sufficient flexibility to carry a variety of lower-level rates within the 51.84 Mb/s signal.
Optical Networking vis-à-vis Other Technologies
* Size and Weight: Since individual optic fibers are typically only 125 μm in diameter, a multiple fiber cable can be made that is much smaller than corresponding metallic cables.
* Bandwidth: Fiber optic cables have bandwidths that can be orders of magnitude greater than metallic cable. Low data rate systems can be eas¬ily upgraded to higher rate systems without the need to replace the fibers. Upgrading can be achieved by changing light sources (LED to laser), improving the modulation technique, improving the receiver, or using wavelength division multiplexing.
* Repeater spacing: With low-loss fiber optic cable, the distance between repeaters can be significantly greater than in metallic cable systems. More¬over, losses in optical fibers are independent of bandwidth, whereas with coaxial or twisted pair cable the losses increase with bandwidth. Thus this advantage in repeater spacing increases with the system’s bandwidth.
* Electrical isolation: Fiber optic cable is electrically nonconducting, which eliminates all electrical problems that now beset metallic cable. Fiber optic systems are immune to power surges, lightning induced currents, ground loops, and short circuits. Fibers are not susceptible to electro¬magnetic interference from power lines, radio signals, adjacent cable sys¬tems, or other electromagnetic sources.
* Crosstalk: Because there is no optical coupling from one fiber to another within a cable, fiber optic systems are free from crosstalk. In metallic cable systems, by contrast, crosstalk is a common problem and is often the limiting factor in performance.
* Environment: Properly designed fiber optic systems are relatively unaf¬fected by adverse temperature and moisture conditions and therefore have application to underwater cable. For metallic cable, however, mois¬ture is a constant problem particularly in underground (buried) applica¬tions, resulting in short circuits, increased attenuation, corrosion, and increased crosstalk.
* Reliability: The reliability of optical fibers, optical drivers, and optical receivers has reached the point where the limiting factor is usually the associated electronics circuitry.
* Cost: The numerous advantages listed here for fiber optic systems have resulted in dramatic growth in their application with attendant reductions in cost due to technological improvements and sales volume.
* Frequency allocations: Fiber (and metallic) cable systems do not require frequency allocations from an already crowded frequency spectrum. Moreover, cable systems do not have the terrain clearance, multipath fading, and interference problems common to radio systems.
Business Implications and Applications
Today fiber optic systems are much more cost effective than metallic cable, satellite, and radio for long haul, high bit rate applications. Fiber optic cable is also expected eventually to overtake metallic cable in short haul applications, includ¬ing metro facilities and local networks. One final cost factor in favor of fiber optics is the choice of material, namly silicon, which of course is one of the earth's most abundant elements, versus copper, which may someday be in short supply, or the radio spectrum, which is already in short supply.
Source: www.eogogics.com/talkgogics/tutorials/optical-networking
As the name suggests, optical networks form a class of networks where optical, rather than electronic, components are the building blocks of the network. Compared to metallic cable, fiber optic systems offer greater bandwidths, lower attenuation, and no crosstalk or electrical interference. Those advantages have led to the dramatic growth of fiber optic systems worldwide. Today, nearly all long-haul telecommunications depend on the use of optical networks for their large capacity and robust performance.
Standards
Standards for fiber optic cable and other optical components have been developed over the last 20 years primarily by the American National Standards Institute (ANSI) and the International Telecommunications Union (ITU). Standards for fiber optic transmission have been developed initially in North America under the name Synchronous Optical Network (SONET) and later by the ITU using the name Synchronous Digital Hierarchy (SDH).
Historical Milestones
* 1958: Discovery of laser
* Mid-60s: Demonstration of guided wave optics
* 1970: Production of low-loss fibers, which made long-distance optical transmission possible
* 1970: Invention of semiconductor laser diode, which made highly refined optical transceivers possible
* 70s-80s: Use of fiber in telephony: SONET/SDH standards from ITU
* Mid-80s: LANs/MANs: broadcast-and-select architectures
* 1988: First trans-Atlantic optical fiber laid
* Late-80s: Development of EDFA (optical amplifier), which greatly alleviated distance limitations
* Mid/late-90s: DWDM systems explode
* Late-90s: Intelligent Optical networks
* 20?? Soliton transmission with optical TDM
Optical Networking: Why?
The “traditional" networks consist, for the most part, of a collection of electronic switches interconnected by point-to-point optical fiber links, which can span local, metropolitan, or wide area networks. To accommodate continually increasing demand for bandwidth and flexibility, such networks are being enhanced by adding more fibers and switches, increasing the bit rate per fiber, and upgrading the switches' size, throughput and functionality. Such enhancements eventually lead to very large and complex networks that are difficult and expensive to construct, operate and maintain. Recent and emerging advances in optical technology promise revolutionary all-optical networks capable of providing improved economy, flexibility and robustness while still capable of making use of the large existing fiber base.
Principles and Operation
An optical fiber is a cylindrical waveguide made of two transparent materials each with a different index of refraction. The two materials, usually high-quality glass, are arranged concentrically to form an inner core and an outer cladding. Different entry angles of the light source result in multiple modes of wave propagation. Propagation can be restricted to a single mode by using a small-diameter core.
The choice between single-mode and multimode fiber depends on the desired repeater spacing or transmission rate; single mode is the preferred choice for long-haul or high data-rate systems. The earliest form of multimode fiber was the step-index, where the core has a uniform index of refraction and the concentric cladding also has a uniform but lower index. In this case the propagation velocity within the core is constant, so that rays traveling a longer path arrive behind rays traveling a shorter path, thus producing pulse spreading, or dispersion. These dispersive effects may be remedied by constructing a fiber whose refractive index increases toward the axis, with a resulting refractive index profile that is parabolic. With a graded-index fiber, rays that travel longer paths have greater velocity than rays traveling the shorter paths due to decreasing refractive index with radial distance. The various modes then tend to have the same arrival time, such that dispersion is minimized and greater bandwidths become possible for multimode fibers.
Within the spectrum available in a fiber optic system, there are three low-loss windows, at wavelengths of approximately 850, 1300, and 1550 nm. Early applications of fiber optics for communications applications were based on the short-wavelength band of roughly 800 to 860 nm. Operation in the longer-wavelength bands, particularly at 1300 and 1550 nm, is attractive because of improved attenuation and dispersion characteristics at these wavelengths. Typically today the shorter-wavelength band is used for short-haul, low data rate systems, and the longer-wavelength bands are applied to long-haul, high data rate systems. Special fibers have been developed that shift the minimum dispersion to about 1550 nm to take advantage of lower attenuation as well as minimum dispersion. These fibers are called dispersion-shifted fibers, and are important to single-mode fiber applications.
Low-data rate, short-haul fiber optic systems tend toward multimode cable, LED transmitters, and PIN diode receivers. High-data rate, long-haul systems tend toward single-mode cable, laser diode transmitters, and avalanche photodiode receivers. Latest generation fiber optic systems have introduced innovations that have significantly improved the bandwidth and repeater spacing possible. Coherent detection via either homodyne or heterodyne techniques allows much greater bandwidths to be realized. Several wavelengths can be transmitted simultaneously in wavelength-division multiplexing, analogous to frequency-division multiplexing used in telephony. Optical amplifiers are now available that eliminate electronics and instead use specially doped fiber or semiconductor laser devices. The use of optical amplifiers will allow a fiber optic system to be upgraded in bit rate without replacement of the repeaters. Optical amplifiers have also been used to achieve ultra-long distances via soliton transmission, which is the transmission of an idealized pulse without loss of pulse shape.
Types of Optical Networks
Optical networks may be classified in several ways. Opaque optical networks include optical-electronic-optical (OEO) conversion, while in all-optical networks each connection is totally optical (or transparent) except at the end nodes.
Optical networks may be single wavelength or multiple-wavelengths (WDM). The use of SONET/SDH with a single carrier is a typical example of an opaque, single-wavelength optical network.
Finally, optical networks may be passive or active. A passive optical network (PON) is an all-optical network that utilizes only passive optical components, e.g., fibers, directional couplers, star couplers, wavelength routers, wavelength multiplexers, and filters. The intended applications are fiber-in-the-loop (local loop) and fiber-to-the-home (FTTH). The optical signaling formats in PONs can employ wavelength-division multiplexing (WDM), subcarrier multiplexing, time-division multiplexing (TDM) or any combination of these. An active all-optical network (AON) enables each of a large number of optical WDM channels (wavelengths) to propagate from source to destination over long distances and high bit rates without optical-to-electronic format conversion within the network.
Optical Network Architecture
There are two standard optical architectures, linear and ring, both of which can provide network protection and restoration of services. SONET rings are the most widely deployed architecture. They can be thought of linear networks folded back to create a loop or ring. But unlike linear architectures, rings are designed to guarantee automatic restoration of services when cable or nodes fails, by use of loops around the failed component. Because of this automatic protection against failures, these rings are called self-healing. There are several SONET ring architectures that depend on the number of fibers, transmission direction, and level of switching protection.
Originally developed in the United States, the SONET standard was adopted by the ITU-T but renamed as the Synchronous Digital Hierarchy (SDH). These standards provide a complete set of specifications to allow national and international connections at various levels. Optical interfaces are defined that provide a universal fiber interface and permit mid-span interconnection of different vendor equipment. A standardized signal structure allows any existing hierarchical rates (for example, DS-1, DS-3, E-1, and E-3) to be accommodated. Overhead within the SONET signals facilitate synchronization, add and drop multiplexing, electronic switching, performance monitoring and network management of the composite and tributary signals. The SONET hierarchy is built on synchronous multiplexing of a basic SONET rate of 51.84 Mb/s, so that higher SONET rates are simply N x 51.84 Mb/s. The basic signal structure provides sufficient flexibility to carry a variety of lower-level rates within the 51.84 Mb/s signal.
Optical Networking vis-à-vis Other Technologies
* Size and Weight: Since individual optic fibers are typically only 125 μm in diameter, a multiple fiber cable can be made that is much smaller than corresponding metallic cables.
* Bandwidth: Fiber optic cables have bandwidths that can be orders of magnitude greater than metallic cable. Low data rate systems can be eas¬ily upgraded to higher rate systems without the need to replace the fibers. Upgrading can be achieved by changing light sources (LED to laser), improving the modulation technique, improving the receiver, or using wavelength division multiplexing.
* Repeater spacing: With low-loss fiber optic cable, the distance between repeaters can be significantly greater than in metallic cable systems. More¬over, losses in optical fibers are independent of bandwidth, whereas with coaxial or twisted pair cable the losses increase with bandwidth. Thus this advantage in repeater spacing increases with the system’s bandwidth.
* Electrical isolation: Fiber optic cable is electrically nonconducting, which eliminates all electrical problems that now beset metallic cable. Fiber optic systems are immune to power surges, lightning induced currents, ground loops, and short circuits. Fibers are not susceptible to electro¬magnetic interference from power lines, radio signals, adjacent cable sys¬tems, or other electromagnetic sources.
* Crosstalk: Because there is no optical coupling from one fiber to another within a cable, fiber optic systems are free from crosstalk. In metallic cable systems, by contrast, crosstalk is a common problem and is often the limiting factor in performance.
* Environment: Properly designed fiber optic systems are relatively unaf¬fected by adverse temperature and moisture conditions and therefore have application to underwater cable. For metallic cable, however, mois¬ture is a constant problem particularly in underground (buried) applica¬tions, resulting in short circuits, increased attenuation, corrosion, and increased crosstalk.
* Reliability: The reliability of optical fibers, optical drivers, and optical receivers has reached the point where the limiting factor is usually the associated electronics circuitry.
* Cost: The numerous advantages listed here for fiber optic systems have resulted in dramatic growth in their application with attendant reductions in cost due to technological improvements and sales volume.
* Frequency allocations: Fiber (and metallic) cable systems do not require frequency allocations from an already crowded frequency spectrum. Moreover, cable systems do not have the terrain clearance, multipath fading, and interference problems common to radio systems.
Business Implications and Applications
Today fiber optic systems are much more cost effective than metallic cable, satellite, and radio for long haul, high bit rate applications. Fiber optic cable is also expected eventually to overtake metallic cable in short haul applications, includ¬ing metro facilities and local networks. One final cost factor in favor of fiber optics is the choice of material, namly silicon, which of course is one of the earth's most abundant elements, versus copper, which may someday be in short supply, or the radio spectrum, which is already in short supply.
Source: www.eogogics.com/talkgogics/tutorials/optical-networking
Tuesday, October 27, 2009
Research topics
Research topics
alphaWorks is known for launching emerging technologies. With these research topics, we are providing a collection of resources – technology downloads, demos, articles, and resources – to help build awareness and understanding about an emerging topic.
RSS Feeds
Research topicsCollaborative Development Environments: In software development, a Collaborative Development Environment (CDE) allows developers and stakeholders to share ideas and knowledge, and work together toward a common task. With the launch of this latest Research topic, alphaWorks focuses on the services model and CDEs which allow engineers to solve problems online.
RFID: RFID (Radio Frequency Identification) is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags or transponders.
Cell Broadband Engine technology: Learn more about Cell BE, a breakthrough microprocessor with unique capabilities for applications requiring video, 3D graphics, or high-performance computation for imaging, security, visualization, healthcare, surveillance and more.
Accessibility: Accessibility technologies put information and technology within reach of the general population with the goal of creating end-to-end accessibility for all users.
Visualization: Visualization technologies transform information into a visual form enabling the viewer to easily understand the information using interactive graphics and visual design.
Semantics: New semantic information-management schemes enable companies to make better use of their information. Learn how semantics technology can help your development efforts.
Source:www.alphaworks.ibm.com/topics
alphaWorks is known for launching emerging technologies. With these research topics, we are providing a collection of resources – technology downloads, demos, articles, and resources – to help build awareness and understanding about an emerging topic.
RSS Feeds
Research topicsCollaborative Development Environments: In software development, a Collaborative Development Environment (CDE) allows developers and stakeholders to share ideas and knowledge, and work together toward a common task. With the launch of this latest Research topic, alphaWorks focuses on the services model and CDEs which allow engineers to solve problems online.
RFID: RFID (Radio Frequency Identification) is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags or transponders.
Cell Broadband Engine technology: Learn more about Cell BE, a breakthrough microprocessor with unique capabilities for applications requiring video, 3D graphics, or high-performance computation for imaging, security, visualization, healthcare, surveillance and more.
Accessibility: Accessibility technologies put information and technology within reach of the general population with the goal of creating end-to-end accessibility for all users.
Visualization: Visualization technologies transform information into a visual form enabling the viewer to easily understand the information using interactive graphics and visual design.
Semantics: New semantic information-management schemes enable companies to make better use of their information. Learn how semantics technology can help your development efforts.
Source:www.alphaworks.ibm.com/topics
Research Topics List
JPL's charter is to conduct robotic space missions for NASA, to explore our own and neighboring planetary systems, understand the origin and evolution of the universe and make critical measurements to understand our home planet and help protect it.
We do this by developing integrated capabilities in engineering, science and technology, in a unique environment that strives for excellence in any of the three areas. To be successful in our ability to implement missions for NASA, we foster research in those areas of space-based science that establish our leadership in the science community and those technologies that allow the innovations that are crucial to maintaining our competitive edge.
Our science, technology and engineering research covers many areas of planetary, astrophysics and Earth science, both as basic research leading to new observations and mission concepts, as well as research based on the data acquired by JPL flight projects.
Our technology research covers areas ranging from robotic systems, a range of in-situ and remote sensing instruments, deep space communications and navigation, information systems, precision flying and planetary protection and survivability.
Earth Sciences
Earth scientists at JPL conduct research to characterize and understand the atmosphere, land, and oceans on our home planet to make better predictions of future changes.
Planetary Sciences
Planetary scientists work to improve our understanding of the planets, satellites and smaller bodies in the solar system.
Astrophysics & Space Sciences
Astrophysics and space science research efforts at JPL are charged with studying the physics and origins of our galaxy, and ultimately our universe.
Exploration & Observational Systems
JPL has continued to achieve its historical level of success by developing and applying increasingly advanced technologies to support mission science objectives.
Software & Computing Systems
JPL is dedicated to meeting best practice standards when developing mission software and computing systems to support the next generation of missions.
Source:scienceandtechnology.jpl.nasa.gov/research/ResearchTopics/
We do this by developing integrated capabilities in engineering, science and technology, in a unique environment that strives for excellence in any of the three areas. To be successful in our ability to implement missions for NASA, we foster research in those areas of space-based science that establish our leadership in the science community and those technologies that allow the innovations that are crucial to maintaining our competitive edge.
Our science, technology and engineering research covers many areas of planetary, astrophysics and Earth science, both as basic research leading to new observations and mission concepts, as well as research based on the data acquired by JPL flight projects.
Our technology research covers areas ranging from robotic systems, a range of in-situ and remote sensing instruments, deep space communications and navigation, information systems, precision flying and planetary protection and survivability.
Earth Sciences
Earth scientists at JPL conduct research to characterize and understand the atmosphere, land, and oceans on our home planet to make better predictions of future changes.
Planetary Sciences
Planetary scientists work to improve our understanding of the planets, satellites and smaller bodies in the solar system.
Astrophysics & Space Sciences
Astrophysics and space science research efforts at JPL are charged with studying the physics and origins of our galaxy, and ultimately our universe.
Exploration & Observational Systems
JPL has continued to achieve its historical level of success by developing and applying increasingly advanced technologies to support mission science objectives.
Software & Computing Systems
JPL is dedicated to meeting best practice standards when developing mission software and computing systems to support the next generation of missions.
Source:scienceandtechnology.jpl.nasa.gov/research/ResearchTopics/
CDMA
Code Division Multiple Access (CDMA) is a radically new concept in wireless communications. It has gained widespread international acceptance by cellular radio system operators as an upgrade that will dramatically increase both their system capacity and the service quality. It has likewise been chosen for deployment by the majority of the winners of the United States Personal Communications System spectrum auctions. It may seem, however, mysterious for those who aren't familiar with it. This site is provided in an effort to dispel some of the mystery and to disseminate at least a basic level of knowledge about the technology.
CDMA is a form of spread-spectrum , a family of digital communication techniques that have been used in military applications for many years. The core principle of spread spectrum is the use of noise-like carrier waves, and, as the name implies, bandwidths much wider than that required for simple point-to-point communication at the same data rate. Originally there were two motivations: either to resist enemy efforts to jam the communications (anti-jam, or AJ), or to hide the fact that communication was even taking place, sometimes called low probability of intercept (LPI). It has a history that goes back to the early days of World War II.
The use of CDMA for civilian mobile radio applications is novel. It was proposed theoretically in the late 1940's, but the practical application in the civilian marketplace did not take place until 40 years later. Commercial applications became possible because of two evolutionary developments. One was the availability of very low cost, high density digital integrated circuits, which reduce the size, weight, and cost of the subscriber stations to an acceptably low level. The other was the realization that optimal multiple access communication requires that all user stations regulate their transmitter powers to the lowest that will achieve adequate signal quality.
CDMA changes the nature of the subscriber station from a predominately analog device to a predominately digital device. Old-fashioned radio receivers separate stations or channels by filtering in the frequency domain. CDMA receivers do not eliminate analog processing entirely, but they separate communication channels by means of a pseudo-random modulation that is applied and removed in the digital domain, not on the basis of frequency. Multiple users occupy the same frequency band. This universal frequency reuse is not fortuitous. On the contrary, it is crucial to the very high spectral efficiency that is the hallmark of CDMA. Other discussions in these pages show why this is true.
CDMA is altering the face of cellular and PCS communication by:
Dramatically improving the telephone traffic capacity
Dramatically improving the voice quality and eliminating the audible effects of multipath fading
Reducing the incidence of dropped calls due to handoff failures
Providing reliable transport mechanism for data communications, such as facsimile and internet traffic
Reducing the number of sites needed to support any given amount of traffic
Simplifying site selection
Reducing deployment and operating costs because fewer cell sites are needed
Reducing average transmitted power
Reducing interference to other electronic devices
Reducing potential health risks
Commercially introduced in 1995, CDMA quickly became one of the world's fastest-growing wireless technologies. In 1999, the International Telecommunications Union selected CDMA as the industry standard for new "third-generation" (3G) wireless systems. Many leading wireless carriers are now building or upgrading to 3G CDMA networks in order to provide more capacity for voice traffic, along with high-speed data capabilities.
CDMA is a form of Direct Sequence Spread Spectrum communications. In general, Spread Spectrum communications is distinguished by three key elements:
1. The signal occupies a bandwidth much greater than that which is necessary to send the information. This results in many benefits, such as immunity to interference and jamming and multi-user access, which we'll discuss later on.
2. The bandwidth is spread by means of a code which is independent of the data. The independence of the code distinguishes this from standard modulation schemes in which the data modulation will always spread the spectrum somewhat.
3. The receiver synchronizes to the code to recover the data. The use of an independent code and synchronous reception allows multiple users to access the same frequency band at the same time.
In order to protect the signal, the code used is pseudo-random. It appears random, but is actually deterministic, so that the receiver can reconstruct the code for synchronous detection. This pseudo-random code is also called pseudo-noise (PN).
There are three ways to spread the bandwidth of the signal:
Frequency hopping. The signal is rapidly switched between different frequencies within the hopping bandwidth pseudo-randomly, and the receiver knows before hand where to find the signal at any given time.
Time hopping. The signal is transmitted in short bursts pseudo-randomly, and the receiver knows beforehand when to expect the burst.
Direct sequence. The digital data is directly coded at a much higher frequency. The code is generated pseudo-randomly, the receiver knows how to generate the same code, and correlates the received signal with that code to extract the data.
How spread spectrum works:
Spread Spectrum uses wide band, noise-like signals. Because Spread Spectrum signals are noise-like, they are hard to detect. Spread Spectrum signals are also hard to Intercept or demodulate. Further, Spread Spectrum signals are harder to jam (interfere with) than narrowband signals. These Low Probability of Intercept (LPI) and anti-jam (AJ) features are why the military has used Spread Spectrum for so many years. Spread signals are intentionally made to be much wider band than the information they are carrying to make them more noise-like.
Spread Spectrum signals use fast codes that run many times the information bandwidth or data rate. These special "Spreading" codes are called "Pseudo Random" or "Pseudo Noise" codes. They are called "Pseudo" because they are not real gaussian noise.
Spread Spectrum transmitters use similar transmit power levels to narrow band transmitters. Because Spread Spectrum signals are so wide, they transmit at a much lower spectral power density, measured in Watts per Hertz, than narrowband transmitters. This lower transmitted power density characteristic gives spread signals a big plus. Spread and narrow band signals can occupy the same band, with little or no interference. This capability is the main reason for all the interest in Spread Spectrum today.
CDMA / Spread Spectrum Resources:
Introduction to CDMA
ABCs of Spread Sprectum
CDMA Technology
CDMA Basics
Overview of CDMA
CDMA vs TDMA
Comparision between GSM IS-95
Book: Spread Spectrum: Hedy Lamarr and the mobile phone
CDMA Discussion Forum
Source: www.telecomspace.com/cdma.html
CDMA is a form of spread-spectrum , a family of digital communication techniques that have been used in military applications for many years. The core principle of spread spectrum is the use of noise-like carrier waves, and, as the name implies, bandwidths much wider than that required for simple point-to-point communication at the same data rate. Originally there were two motivations: either to resist enemy efforts to jam the communications (anti-jam, or AJ), or to hide the fact that communication was even taking place, sometimes called low probability of intercept (LPI). It has a history that goes back to the early days of World War II.
The use of CDMA for civilian mobile radio applications is novel. It was proposed theoretically in the late 1940's, but the practical application in the civilian marketplace did not take place until 40 years later. Commercial applications became possible because of two evolutionary developments. One was the availability of very low cost, high density digital integrated circuits, which reduce the size, weight, and cost of the subscriber stations to an acceptably low level. The other was the realization that optimal multiple access communication requires that all user stations regulate their transmitter powers to the lowest that will achieve adequate signal quality.
CDMA changes the nature of the subscriber station from a predominately analog device to a predominately digital device. Old-fashioned radio receivers separate stations or channels by filtering in the frequency domain. CDMA receivers do not eliminate analog processing entirely, but they separate communication channels by means of a pseudo-random modulation that is applied and removed in the digital domain, not on the basis of frequency. Multiple users occupy the same frequency band. This universal frequency reuse is not fortuitous. On the contrary, it is crucial to the very high spectral efficiency that is the hallmark of CDMA. Other discussions in these pages show why this is true.
CDMA is altering the face of cellular and PCS communication by:
Dramatically improving the telephone traffic capacity
Dramatically improving the voice quality and eliminating the audible effects of multipath fading
Reducing the incidence of dropped calls due to handoff failures
Providing reliable transport mechanism for data communications, such as facsimile and internet traffic
Reducing the number of sites needed to support any given amount of traffic
Simplifying site selection
Reducing deployment and operating costs because fewer cell sites are needed
Reducing average transmitted power
Reducing interference to other electronic devices
Reducing potential health risks
Commercially introduced in 1995, CDMA quickly became one of the world's fastest-growing wireless technologies. In 1999, the International Telecommunications Union selected CDMA as the industry standard for new "third-generation" (3G) wireless systems. Many leading wireless carriers are now building or upgrading to 3G CDMA networks in order to provide more capacity for voice traffic, along with high-speed data capabilities.
CDMA is a form of Direct Sequence Spread Spectrum communications. In general, Spread Spectrum communications is distinguished by three key elements:
1. The signal occupies a bandwidth much greater than that which is necessary to send the information. This results in many benefits, such as immunity to interference and jamming and multi-user access, which we'll discuss later on.
2. The bandwidth is spread by means of a code which is independent of the data. The independence of the code distinguishes this from standard modulation schemes in which the data modulation will always spread the spectrum somewhat.
3. The receiver synchronizes to the code to recover the data. The use of an independent code and synchronous reception allows multiple users to access the same frequency band at the same time.
In order to protect the signal, the code used is pseudo-random. It appears random, but is actually deterministic, so that the receiver can reconstruct the code for synchronous detection. This pseudo-random code is also called pseudo-noise (PN).
There are three ways to spread the bandwidth of the signal:
Frequency hopping. The signal is rapidly switched between different frequencies within the hopping bandwidth pseudo-randomly, and the receiver knows before hand where to find the signal at any given time.
Time hopping. The signal is transmitted in short bursts pseudo-randomly, and the receiver knows beforehand when to expect the burst.
Direct sequence. The digital data is directly coded at a much higher frequency. The code is generated pseudo-randomly, the receiver knows how to generate the same code, and correlates the received signal with that code to extract the data.
How spread spectrum works:
Spread Spectrum uses wide band, noise-like signals. Because Spread Spectrum signals are noise-like, they are hard to detect. Spread Spectrum signals are also hard to Intercept or demodulate. Further, Spread Spectrum signals are harder to jam (interfere with) than narrowband signals. These Low Probability of Intercept (LPI) and anti-jam (AJ) features are why the military has used Spread Spectrum for so many years. Spread signals are intentionally made to be much wider band than the information they are carrying to make them more noise-like.
Spread Spectrum signals use fast codes that run many times the information bandwidth or data rate. These special "Spreading" codes are called "Pseudo Random" or "Pseudo Noise" codes. They are called "Pseudo" because they are not real gaussian noise.
Spread Spectrum transmitters use similar transmit power levels to narrow band transmitters. Because Spread Spectrum signals are so wide, they transmit at a much lower spectral power density, measured in Watts per Hertz, than narrowband transmitters. This lower transmitted power density characteristic gives spread signals a big plus. Spread and narrow band signals can occupy the same band, with little or no interference. This capability is the main reason for all the interest in Spread Spectrum today.
CDMA / Spread Spectrum Resources:
Introduction to CDMA
ABCs of Spread Sprectum
CDMA Technology
CDMA Basics
Overview of CDMA
CDMA vs TDMA
Comparision between GSM IS-95
Book: Spread Spectrum: Hedy Lamarr and the mobile phone
CDMA Discussion Forum
Source: www.telecomspace.com/cdma.html
Telecommunications Glossary
Select the first letter of the word from the list below to jump to appropriate section of the glossary. If the term you are looking for starts with a digit or symbol, choose the '#' link. Many terms contain Hyperlinks to appropriate sites.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #
A
Acoustic Coupler
This is a special cradle in which you place the handset of a phone. This is connected to a modem, and the modem accesses the phone line through this coupler. Modern modems connect directly to the phone line.
Analogue
Analogue refers to signals that can represent an infinite range of numbers, as opposed to digital which can only be distinct whole numbers. Analogue data often comes from measurements, like a sine wave. The sound a modem makes over the phone is analog since it can be any of a number of different frequencies. The fixed-line networks usually transfer analogue data and fax. The GSM networks are Digital.
ANSI
ANSI graphics is a set of cursor control codes which originated on the VT100 smart terminal. Many BBS's use these codes to help improve the sending of characters to communications programs. It uses the escape character, followed by other characters, which allows movement of the cursor on the screen, a change of color, and more.
Archie
A program and database which locates files on the Internet.
ARPANET
From ARPA (Advanced Research Projects Agency) and network. An early experimental network.
ASCII
American Standard Code of Information Interchange. It uses 7 bits to represent all uppercase and lowercase characters, as well as numbers, punctuation marks, and other characters. ASCII often uses 8 bits in the form of bytes and ignores the first bit.
ASCII transfer
When a text file is sent directly as it is, without any special codes.
Asynchronous Transmission
Transmission method in which the intervals between transmitted characters may be unequal of length. Transmission is controlled by start and stop bits at the beginning and end of each character. This way, if there is line noise, the modem can find out right away where the next byte should start. [See Synchronous communication].
AT command
Any instructions sent to a modem that begin with "AT". See also Hayes AT command set.
AT command set
See Hayes AT command set.
Attention characters
The letters "AT", which get the modem's attention that you are about to send it a command. [See also Hayes AT command set].
Auto Reliable
The ability of a modem to be able to communicate both with modems that do have error-control and/or data compression, and those that do not.
B
Bandwidth
The difference between the upper and lower limits of a band. A range of radio, audio, or other frequencies. Since it is so limited, a modem must carefully change data into sounds that "fit" within this range. Similar to frequency spectrum. Bandwidth of a voice channel is 3000Hz-300Hz which equals 2700Hz. Telephone lines have a bandwidth from 300 hertz to 3400 hertz.
BASIC
Beginners All-purpose Symbolic Instruction Code. It is a programming language. It is called symbolic because it allows programmers to use symbols to represent numbers and information. In algebra, these symbols are called variables.
Balun
Balanced/unbalanced. A device which connects a balanced (two-wire) line, such as a phone line, to an unbalanced (coaxial) line, like cable. The two-wire line is called balanced because the currents in each wire are equal and in opposite directions.
Baud
A term referring to the speed at which modems communicate. Technically, it is the number of changes in an electronic signal per second. Since the number of changes used to be the same as the number of bits sent or received per second, bps and baud are often used interchangeably. However, there is a difference, which is very often confused. For example, many 1200bps modems were advertised as 1200 baud, even though they operate at 600 baud. They send out 2 bits 600 times a second, which means that it is 600 baud. However, since it is so often misunderstood, you can assume that when you see "baud" it means bits per second, unless it is stated otherwise. The term comes from the scientist J. M. E. Baudot. [See also bps].
BFT
Binary File Transfer
Billion Rand
What it costs to start a cellular network
Bit
A Binary digIT. It is a number in base 2 (binary), which means that it can only be a 0 or a 1. It is used in the expres-sion `bits per second'. [See also byte].
bps
Bits Per Second. The transmission speed of most modems is measured in baud or bps. Bps is literally the number of bits sent by the modem every second. [See also baud].
Block size
When used with either error control or data compression protocols, refers to the number of characters to be sent at one time. If error control is used, the codes are sent immediately following this block. Typical block sizes are 64, 128, 192, or 256 characters. Small block sizes are better when the line quality is bad (such as for long distance calls), while large block sizes are better during good connections (such as for local calls).
byte
A group of 8 bits. It usually represents one character.
C
CCITT
Consultative Committee International on Telephones and Telegraphy. Used to set standards for modems. Replaced by the ITU.
Card Services
DOS and Windows 3.1x users must have Card Services enabled to use their computer's PCMCIA slot(s). Card Services simply allows DOS/Windows 3.1 to see and set up the computer's PCMCIA slot. They will automatically allocate a Communications Port (COM 1 to 5) when the Option modem is plugged in. The Option modem can then be accessed by communications programs via the Windows 95-assigned COM port. Windows 95 users DO NOT need to install Card Service as it is built into Windows 95. Notebook users using DOS/Windows 3.1 usually have the Card Services software bundled with their purchase. Option modems come packaged with a PC Card Installation disk that has an install program for these Card Services. You can however download it here.
Carrier Detect
The information as to whether or not the modem senses a carrier, like a fixed-line dialling tone or a data/fax services enabled on a GSM subscription.
CIS
Card Information Services. A PCMCIA setup protocol.
Carrier Detect Threshold
A way of measuring how well a modem can detect valid data over noisy phone lines. It is measured in negative dBm's (decibel-milliwatts). The bigger the number (the more negative) the better. For example,45 dBm is better than40 dBm.
CLIP
Caller Line ID Presentation. A code that is sent over the phone lines in some areas when a person makes a phone call. This code includes the phone number of the person making the call. Some modems are able to understand this signal, and let you know who is calling you before you answer the phone.
CLIR
Caller Line ID Restriction. The ability to block someone who you're calling from seeing your number.
CDPR
Cellular Digital Packet Radio
Cell
The receiver/transmitter a GSM phone connects to; the equivalent of the base station of a cordless phone. A cell can support a number of simultaneous calls.
Checksum
A number that represents a larger group of numbers in order to check for errors in data transmission. It is commonly used when downloading a program, as well as in error control protocols. The checksum is the result of a mathematical equation, such as adding all the numbers in a block together (although it is usually more complex than that).
Chip Set
A group of important IC chips on a modem (or other computer peripheral) that are all made by the same manufacturer. While there are many companies that make modems, there are only a few that make the chips for them. Because the chip manufacturer is making the chips for many companies, they produce more chips, and the price of the chips is lower than if each company produced their own. This decreases the price of the modems on the market.
CDMA
Code Divison Multiple Access. A digital cellular technique invented by Qualcomm.
CMOS
Complementary Metal Oxide Semiconductor. A chip which uses small amounts of electricity. It is used typically on battery-powered computers and to save configuration information on other computers when they are turned off.
Communications program
A program that controls a modem, and has features that allow the user to do such things as upload, download, etc. It is similar to a terminal program but more sophisticated. An example is Trumpet WinSock for connecting to the Internet, and Windows HyperTerminal.
Compatible
When one object can work just like another. Although the term is usually used with computers, it is often used with modems. Many modems are compatible with other popular modems.
Compress
To make data take up less space. Archiving programs do this, which means that files will take less time to transfer with modems. Many modems now have the ability to automatically compress the information they send and receive. [See also archive, data compression].
CODEC
COmpressor/DECompressor, the chip inside every digital GSM cellphone that allows the cellphone to tranmsit voice data at high efficiency and speed across the GSM cellular network. The CODEC will trip redundant voice data like when neither party is talking allowing more effcient use of scarse bandwidth.
CEPT
Conference of European Post and Telecommunications, the European telecommunications authority.
Cracker
From hacker and safe cracker. A hacker who breaks into computers
CTS
Clear To Send. This is when the modem lets the other computer know that it can send information to the other computer. [See also Flow Control, Return To Send].
CTS/RTS
The method of flow control that uses the CTS and RTS signals. It is built into the hardware, not software. [See also CTS, RTS, flow control].
D
DAA
Data Access Arrangement. A device used to connect modems to the switched telephone network.
Data over GSM
Send digital data over the digital GSM networks. Click here for a tutorial on data and fax transmission over GSM.
DCE
Data Circuit Terminating Equipment. Sets up and maintains a data connection link over a communications medium. For example, a modem.
Data Compression
Some modems have the capability to 'squash' data so that it takes up less space. When another modem (that also has this capability) receives the data, it 'unsquashes' the data to its original form. By using data compression, a modem can send information faster. It's a lot like shorthand--all the information is still there, but it takes less space and is quicker. [See also MNP-5, V.42bis].
.
Data Transmission rate
The speed at which data travels. For example, data may be sent at 115,200bps. Same as transmission rate, transmission speed, data rate. [See also bps].
dBm
Decibel refers to one milliwatt. This is used to measure certain levels, such as transmit level.
DSA
Data Services Adapter, an alternative interface to PCMCIA for connecting to a fax or data terminal. The Siemens S1 uses a DSA
Digital
A system using discrete numbers to represent data. In computer systems, these are the numbers 0 and 1 (for binary). [See also Analogue].
DSR
Data Set Ready. This indicates that the modem is on, and ready to accept input from the computer (either commands or data to be sent over the phone line)
DTE
Data Terminal Equipment. This is computer equipment which is not directly responsible for communicating, for example, the computer itself and printers. [See also DCE].
DTMF
Dual Tone Multi-Frequency. This is used in tone dialing. It is a method where 2 distinct tones are sent for each digit dialed.
DTR
Data Terminal Ready. The DTR signal is sent from the computer to the modem, to let the modem know that the computer is ready to communicate.
E
EDI
Electronic Data Interchange. Commonly transferred by Internet or X.400 networks
EEPROM
Electrically Erasable Programmable Read-Only Memory
EFF
Electronic Frontier Foundation. An organization promoting civil rights in cyberspace. It is leading the fight against the US government's Clipper Chip.
Error Correction
Error Correction. The ability of a modem to notice errors in transmission, and to resend incorrect data. [See also MNP 1-4, LAPM, V.42].
ETSI
European Telecommunications Standards Institute.
ECFP
European Conference on Computers, Freedom, and Privacy.
E-mail
Electronic mail. Messages that are sent to individual people. You choose who to send the message to and only that person receives the message.
ESPRIT
European Strategic Program for Research in Information Technologies.
Error
When there is line noise and one or more characters are changed. This is especially noticeable when downloading or uploading a program. In this case the error must be detected, and the data must be re-sent.
F
FAQ
Frequently Asked Questions.
Firewall
Computer security that attemps to keep crackers out.
Flame
To write emotional remarks on electronic mail.
Flow control
A method of controlling when information is sent. One method is Xon/Xoff, where a BBS will send information until your computer sends an Xoff (CTRL-S). It will resume sending information when you send an Xon. [See also Xon/Xoff, CTS/RTS].
Full Duplex
A channel providing simultaneous transmission in both directions.
G
GMSK
The method of modulation used by GSM is Gaussian Minimum Shift Keying (GMSK), with a BT value of 0.3 at a gross data rate of 270 kb/s.
Group III FAX
The standard controlling fax communication.
GSM
GSM originally stood for Groupe Speciale Mobile but has been anglicised to Global System for Mobile Communications, an international digital cellular standard. South Africa was one of the first to implement Phase 2 of GSM.
Click here for a brief history of GSM.
H
Half Duplex
A channel which signals in both directions, but not simultaneously.
Handover
What occurs when a cell phone used in a car moves out of the range of one cell and needs to connect to the next available cell. The preceding cell then hands over the connection to the stronger cell.
Hayes AT command set
This is the set of commands used to operate Hayes modems and Hayes compatible modems. Almost all of the commands start with AT.
Hayes compatible
Any modem which operates in the same way as the modems developed by Hayes.
Hertz
A unit of frequency, which equals cycles per second.
I
Interactive Manual
A Windows-based modem control and diagnostic program bundled free with each Option 2-in-1 modem. Here you can alter all Hayes AT commands using icons! Just click on the appropriate icon, and the Interactive Manual will instantly alter the modem's settings. You can also change the modem's settings to conform to the PTT specifications of different countries.
ISO
The International Standards Organisation, the body responsible for setting world technical standards. It is based in Geneva, Switzerland.
ITU
International Telecommunications Union, based in Geneva, Switzerland.
IWU
InterWorking Unit. This is the network "modem" where all the digital to analogue (and visa versa) conversions take place within the digital GSM networks
J
K
L
Lotus
Famous for the Lotus 1-2-3 spreadsheet of the 1980's, and more recently for it's Notes Groupware system. Bought by IBM in 1995.
M
Microsoft
The world's largest developer and publisher of software based in Redmond, Seattle, USA. Headed by William (Bill) Gates, the richest (non-royal) person on this planet.
Modulation
A process whereby a signal is transformed from its original form into a signal that is more suitable for transmission over the medium between transmitter and receiver.
Mosaic
A GUI (Graphical User Interface) for accessing the hypertext WWW (World Wide Web) on the Internet.
MNP
Microcom Networking Protocol. Error control and data compression techniques, created by Microcom, that many newer modems use. They are built into the modem, unlike software error correction in file transfer protocols. There are different MNP levels. Levels 1-4 are error control protocols, and level 5 is a data compression protocol that can compress data to about 50% of its original size. A modem with MNP-5 also has MNP-4. MNP 1-4 is also included in the ITU V.42 error correction system.
MNP normal mode
This is the more common mode used with modems that have MNP capability, where the speed from the computer to the modem can be higher than the connection between the modem and the remote modem. This mode uses buffering to prevent lost data.
MoU
Memorandum of Understanding, the GSM body that overseas GSM standards and implementation around the world. It comprises operators and some manufacturers.
Modem
A MOdulator DEModulator computer peripheral which allows a computer to communicate over telephone lines. This is the heart of computer telecommunications. The main factor that differentiates modems is their speed, measured in bps. Analogue modems talk to one another by converting digital info from the computer into tones called PSK’s. An ordinary analogue modem cannot be physically connected to a GSM phone because networks will not carry PSK tones.
N
NCAIR
National Center for Automated Information Research.
Network Operators
The folks who install and maintain GSM cellular networks. Click here to see a list of GSM operators around the world. Click here to see the South African network operators.
Non-Transparent Cellular Data
Non Transparent phones use a special error correction technique called RLP. Transparent phones data not incorprate the RLP error corerction techniqure and their data MIGHT be corrupted.
O
P
PABX
Private Branch Exchange. This is the telephone system that many offices have, allowing extensions for each telephone, and a connection to the main telephone system.
Parity Bit
Most modems have the capability to send an extra bit for every byte sent, which is used to help sense errors. This is called the parity bit. It can be set to no parity, mark parity, space parity, odd parity or even parity. Most BBS's do not use a parity bit. [See also 8-N-1].
PC Cards
Previously known as PCMCIA cards, these are credit card devices used in notebooks and desktop readers for inter alia, data/fax, storage, GPS puposes.
PCMCIA
A credit card sized card that generally plugs into a notebook computer. It conforms to the Personal Computer Memory Card International Association spec. Now known as PC Cards.
PSK
Phase Shift Keying. In this method of modulation/demodulation, there are two frequencies used (usually 1200 hertz and 2400 hertz). There are 4 different phase angles (0, 90, 180, and 270 degrees), representing dibits 00, 01, 10, and 11. This is usually used for 1200bps transmission. Note that the baud rate using PSK is really 1/2 of the bps rate, since 2 bits are sent at a time instead of one. [See also modulation].
PSTN
Public Switched Telephone Network. This is the regular phone lines that just about everybody uses.
Phreaker
Aperson who spends a lot of time trying to find out as much as possible about the telephone company [like South Africa's TELKOM], and how it works. They often try to find out ways to make long distance calls for free. Some steal calls from telephone credit card users, some steal calls from the phone company directly, and others don't make "free" long distance calls. They are sometimes confused with hackers.
PKZIP
The program which will create an archive with the extension "ZIP". It is one of the most popular archive programs.
Pulse dialing
A method that some phones use to dial numbers. It involves a series of "clicks." Most modems support this type of dialing, which is the only type available in some remote areas. The other method of dialing is tone dialing.
Q
R
RLP
Radio Link Protocol
Non-transparent data uses a special ensure robust GSM-specific error correction technique called RLP for transmission. Both MTN and Vodacom GSM networks support both techniques.
RPE-LPE
Regular Pulse Excitation - Long Term Prediction, the speech coding used by GSM
RACE
Research and Development in Advanced Communication in Europe.
Reset
A modem can be reset. This will change any options (such as parity and speed) to the values that they have when the modem is first used. This can be useful if you change some values for the modem and aren't sure what they do, and then you find that the modem won't work. Resetting the modem will fix everything for you. With Option modems, this is the ATZ command.
RJ-11
This is a normal phone jack. The older South African plugs have a 3-prong connector. All Option modems sold in South Africa have this RJ-11-to-3-prong adapters.
RTS
Request To Send. This is when the computer tells the modem that it wants to send information to the other computer. It is only used in half duplex mode. [See also flow control, CTS].
S
Serial Transmission
A method of transmitting data in which bits are sent sequentially.
SIG
Special Interest Group. The GSM MoU has many SIGS.
SIM
Subscriber Identity Module. This is a Smart Card installed in every GSM handset. Within the GSM application the three primary roles of the SIM are access control to the network (authentication & ciphering), service personalisation (SMS, advice of charge, etc.), network branding and advertising (graphics printed on SIM card). The new generation of Phase 2+ SIMs will enable services such as virtual cash, mobile banking, ticket reservations etc.
SMS
Short Message Service will display a pager-like 160 character message in the LCD panel on the phone. Your phone must support SMS.
Streaming
When data is sent continuously, without waiting to make sure there are no errors. Transparent mode on GSM is an example of a streaming method faster than non-transparent mode, but unreliable.
T
T1
Trunk 1. A heavy duty telephone line.
T3
Trunk 3. A telephone trunk line.
TDMA
Time Division Multiple Access, the magical technique used by the digital GSM network to squeeze more calls onto one channel by dividing a calling channel into a few "discontinuous" pieces.
Telecommunication(s)
This word has no precise definition, but is frequently used. Its definition ranges from "any form of communication over a distance" to "any communication by electric means" to "two computers 'talking' to each other via modems." Methods of communications that probably are considered telecommunications: telephones, cellphones, TV's and fax machines. The word is used both in singular and plural.
Telecommuting
The idea of company employees working from home, rather than their office. At home, they can communicate with the office (and other entities) by modem or voice calls.
Telkom (South Africa)
Telkom is the parastatal fixed-line network operator in South Africa. Option modems are approved for use on the telkom network and 25 other networks around the world.
TELNET
A program which lets you access other computer systems through Internet.
Terminal Emulation
When a communications program can simulate the operations of a smart terminal.
Tone Dialing
This is a method that a phone or modem can use to dial a phone number. It uses one audible tone per digit to be dialed.
Transmit Level
The "loudness" level of the sound leaving a modem to go over the phone lines. It is measured indBm's. It should be different at different frequencies, since certain frequencies have more loss over the phone line than others.
Transparent Data Transmission
A method of transmission in which the transmission medium will not recognize control characters or initiate any control function. Transparent-based phones do not utilise any error correction. Thus the data sent and received MIGHT be corrupted unless a greater than two-bar cellphone signal is used (South African conditions). Non-transparent data uses a special ensure robust GSM-specific error correction technique called RLP for transmission. Both MTN and Vodacom GSM networks support both techniques.
U
UART
Universal Asynchronous Receiver/Transmitter. This is a device in a computer or modem that will change serial data (the way data comes in over the phone line) to parallel, and vice versa. [See also serial, parallel, 16550 UART, 8250 UART, 16450, 16550 UART].
V
V.17
The ITU standard for fax transmission at 14,400bps.
V.21
The international standard, created by ITU, that controls transmission at 300bps.
V.22
The international standard for transmission at 1200bps, created by ITU.
V.22bis
The international standard, created by ITU, that controls data transmission at 2400bps.
V.23
The ITU protocol for transmission of 1200bps one way, 75bps the other way.
V.24
This, combined with V.28 is the ITU standard equivalent to EIA's RS-232C standard. V.24/V.28 has 25 pins, just like the original RS-232C standard.
V.28
Part of V.24.
V.29
The ITU standard for 9600bps half-duplex communications.
V.32
The international standard controlling transmission at 9600bps. It was created by ITU. It has provisions for fallback, if the line is too noisy.
V.32bis
The international standard for 14,400 bps modems, ratified by the ITU.
V.34
The international standard for 28,800 bps modems, ratified by the ITU.
V.42
A standard error control system created by ITU that is in use on many 9600bps modems and some 2400bps modems. It includes LAPM, as well as MNP 2-4.
V.42 compatible
This is a modem that follows all the V.42 specifications, except for LAPM error control (instead it uses MNP).
V.42 compliant
This is a modem which follows all the V.42 specifications, and uses LAPM error control if possible. Otherwise, it will go to MNP error control.
V.42bis
A ITU standard for data compression. It can compress data with about a 3:1 compression ratio, although it can compressup to 4:1 given the right conditions. Any modem with V.42bis also has V.42 error control. [See also Data Compression].
W
W3
World Wide Web
WWW
World Wide Web. A hypertext system set up on the Internet.
Waffle
A DOS program to perform UUCICO.
Winsock
A Windows subroutine library that provides access to the Internet TCP/IP.
WINSOCK.DLL
The actual file containing Winsock.
X
X.25
This is a packet-switching protocol developed by ITU. It is used to carry large amounts of data at fast speeds over leased phone lines.
X.32
This is ITU's 1984 update of X.25, also known as X.25 dialup.
X.400
This is the ITU standard protocol for a global system for the exchange of electronic mail.
X.500
The ITU standard for a directory of the users of the X.400 system.
Xmodem
A file transfer protocol developed by Ward Christensen around 1977. It is fairly slow by today's standards, but was the first widespread file transfer protocol. It uses blocks of 128 bytes, and after each block is sent, it sends a 1 byte checksum to check for errors. If an error is encountered, the block will be re-sent. Almost every communications program offers this protocol.
Xmodem/CRC
The same as Xmodem, but it has a 16-bit CRC instead of the checksum, which makes it more reliable (it catches more errors).
Xmodem-1K
This is similar to Xmodem/CRC, except it uses blocks of 1024 bytes, rather than 128. It is faster than Xmodem, since it needs to stop less often to check for errors. This is sometimes incorrectly called Ymodem. [See also protocol, Xmodem, Ymodem].
Xoff
The CTRL-S character. This is often used to pause information that is being sent. The information will be continued when an CTRL-Q is received. [See also flow control, Xon].
Xon
The CTRL-Q character. This will sometimes continue paused information.
Xon/Xoff
The flow control method using the Xon and Xoff characters. It is built into the software, not the hardware.
Y
Z
ZIP
The file extension which refers to archives that were created by the program PKZIP. You need the program PKUNZIP to get the files out of the archive.
Zmodem
A file transfer protocol which is known for its speed, as well as the ability to transfer information about the files which it sends. It has crash recovery and auto-download features, and can use a 32 bit CRC, which makes it almost error-free.
#
8-N-1
The most common modem format. "8N1" describes the way that your computer and the remote are connected. The first digit is normally 7 or 8, the number of data bits. The second character is a letter describing the parity (N for None, M for Mark, S for Space, O for Odd, and E for Even). The last number is the number of stop bits. Data is sent as follows: Start bit (0) 7 or 8 bits of data (parity bit, if used) stop bit (1) (gap bits, if used)
10BASE-T
An ethernet connection that uses UTP (unshielded twisted-pair) wiring.
16550 UART
This is the UART used with most newer computers and high speed modems. There are several variations, but they all include one main feature: they include buffering, so that if data comes in or is sent faster than the computer/modem can accept it, the UART will hold the data (up to 16 bytes) until the computer/modem is ready for it.
Source: www.cellular.co.za/glossary.htm
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #
A
Acoustic Coupler
This is a special cradle in which you place the handset of a phone. This is connected to a modem, and the modem accesses the phone line through this coupler. Modern modems connect directly to the phone line.
Analogue
Analogue refers to signals that can represent an infinite range of numbers, as opposed to digital which can only be distinct whole numbers. Analogue data often comes from measurements, like a sine wave. The sound a modem makes over the phone is analog since it can be any of a number of different frequencies. The fixed-line networks usually transfer analogue data and fax. The GSM networks are Digital.
ANSI
ANSI graphics is a set of cursor control codes which originated on the VT100 smart terminal. Many BBS's use these codes to help improve the sending of characters to communications programs. It uses the escape character, followed by other characters, which allows movement of the cursor on the screen, a change of color, and more.
Archie
A program and database which locates files on the Internet.
ARPANET
From ARPA (Advanced Research Projects Agency) and network. An early experimental network.
ASCII
American Standard Code of Information Interchange. It uses 7 bits to represent all uppercase and lowercase characters, as well as numbers, punctuation marks, and other characters. ASCII often uses 8 bits in the form of bytes and ignores the first bit.
ASCII transfer
When a text file is sent directly as it is, without any special codes.
Asynchronous Transmission
Transmission method in which the intervals between transmitted characters may be unequal of length. Transmission is controlled by start and stop bits at the beginning and end of each character. This way, if there is line noise, the modem can find out right away where the next byte should start. [See Synchronous communication].
AT command
Any instructions sent to a modem that begin with "AT". See also Hayes AT command set.
AT command set
See Hayes AT command set.
Attention characters
The letters "AT", which get the modem's attention that you are about to send it a command. [See also Hayes AT command set].
Auto Reliable
The ability of a modem to be able to communicate both with modems that do have error-control and/or data compression, and those that do not.
B
Bandwidth
The difference between the upper and lower limits of a band. A range of radio, audio, or other frequencies. Since it is so limited, a modem must carefully change data into sounds that "fit" within this range. Similar to frequency spectrum. Bandwidth of a voice channel is 3000Hz-300Hz which equals 2700Hz. Telephone lines have a bandwidth from 300 hertz to 3400 hertz.
BASIC
Beginners All-purpose Symbolic Instruction Code. It is a programming language. It is called symbolic because it allows programmers to use symbols to represent numbers and information. In algebra, these symbols are called variables.
Balun
Balanced/unbalanced. A device which connects a balanced (two-wire) line, such as a phone line, to an unbalanced (coaxial) line, like cable. The two-wire line is called balanced because the currents in each wire are equal and in opposite directions.
Baud
A term referring to the speed at which modems communicate. Technically, it is the number of changes in an electronic signal per second. Since the number of changes used to be the same as the number of bits sent or received per second, bps and baud are often used interchangeably. However, there is a difference, which is very often confused. For example, many 1200bps modems were advertised as 1200 baud, even though they operate at 600 baud. They send out 2 bits 600 times a second, which means that it is 600 baud. However, since it is so often misunderstood, you can assume that when you see "baud" it means bits per second, unless it is stated otherwise. The term comes from the scientist J. M. E. Baudot. [See also bps].
BFT
Binary File Transfer
Billion Rand
What it costs to start a cellular network
Bit
A Binary digIT. It is a number in base 2 (binary), which means that it can only be a 0 or a 1. It is used in the expres-sion `bits per second'. [See also byte].
bps
Bits Per Second. The transmission speed of most modems is measured in baud or bps. Bps is literally the number of bits sent by the modem every second. [See also baud].
Block size
When used with either error control or data compression protocols, refers to the number of characters to be sent at one time. If error control is used, the codes are sent immediately following this block. Typical block sizes are 64, 128, 192, or 256 characters. Small block sizes are better when the line quality is bad (such as for long distance calls), while large block sizes are better during good connections (such as for local calls).
byte
A group of 8 bits. It usually represents one character.
C
CCITT
Consultative Committee International on Telephones and Telegraphy. Used to set standards for modems. Replaced by the ITU.
Card Services
DOS and Windows 3.1x users must have Card Services enabled to use their computer's PCMCIA slot(s). Card Services simply allows DOS/Windows 3.1 to see and set up the computer's PCMCIA slot. They will automatically allocate a Communications Port (COM 1 to 5) when the Option modem is plugged in. The Option modem can then be accessed by communications programs via the Windows 95-assigned COM port. Windows 95 users DO NOT need to install Card Service as it is built into Windows 95. Notebook users using DOS/Windows 3.1 usually have the Card Services software bundled with their purchase. Option modems come packaged with a PC Card Installation disk that has an install program for these Card Services. You can however download it here.
Carrier Detect
The information as to whether or not the modem senses a carrier, like a fixed-line dialling tone or a data/fax services enabled on a GSM subscription.
CIS
Card Information Services. A PCMCIA setup protocol.
Carrier Detect Threshold
A way of measuring how well a modem can detect valid data over noisy phone lines. It is measured in negative dBm's (decibel-milliwatts). The bigger the number (the more negative) the better. For example,45 dBm is better than40 dBm.
CLIP
Caller Line ID Presentation. A code that is sent over the phone lines in some areas when a person makes a phone call. This code includes the phone number of the person making the call. Some modems are able to understand this signal, and let you know who is calling you before you answer the phone.
CLIR
Caller Line ID Restriction. The ability to block someone who you're calling from seeing your number.
CDPR
Cellular Digital Packet Radio
Cell
The receiver/transmitter a GSM phone connects to; the equivalent of the base station of a cordless phone. A cell can support a number of simultaneous calls.
Checksum
A number that represents a larger group of numbers in order to check for errors in data transmission. It is commonly used when downloading a program, as well as in error control protocols. The checksum is the result of a mathematical equation, such as adding all the numbers in a block together (although it is usually more complex than that).
Chip Set
A group of important IC chips on a modem (or other computer peripheral) that are all made by the same manufacturer. While there are many companies that make modems, there are only a few that make the chips for them. Because the chip manufacturer is making the chips for many companies, they produce more chips, and the price of the chips is lower than if each company produced their own. This decreases the price of the modems on the market.
CDMA
Code Divison Multiple Access. A digital cellular technique invented by Qualcomm.
CMOS
Complementary Metal Oxide Semiconductor. A chip which uses small amounts of electricity. It is used typically on battery-powered computers and to save configuration information on other computers when they are turned off.
Communications program
A program that controls a modem, and has features that allow the user to do such things as upload, download, etc. It is similar to a terminal program but more sophisticated. An example is Trumpet WinSock for connecting to the Internet, and Windows HyperTerminal.
Compatible
When one object can work just like another. Although the term is usually used with computers, it is often used with modems. Many modems are compatible with other popular modems.
Compress
To make data take up less space. Archiving programs do this, which means that files will take less time to transfer with modems. Many modems now have the ability to automatically compress the information they send and receive. [See also archive, data compression].
CODEC
COmpressor/DECompressor, the chip inside every digital GSM cellphone that allows the cellphone to tranmsit voice data at high efficiency and speed across the GSM cellular network. The CODEC will trip redundant voice data like when neither party is talking allowing more effcient use of scarse bandwidth.
CEPT
Conference of European Post and Telecommunications, the European telecommunications authority.
Cracker
From hacker and safe cracker. A hacker who breaks into computers
CTS
Clear To Send. This is when the modem lets the other computer know that it can send information to the other computer. [See also Flow Control, Return To Send].
CTS/RTS
The method of flow control that uses the CTS and RTS signals. It is built into the hardware, not software. [See also CTS, RTS, flow control].
D
DAA
Data Access Arrangement. A device used to connect modems to the switched telephone network.
Data over GSM
Send digital data over the digital GSM networks. Click here for a tutorial on data and fax transmission over GSM.
DCE
Data Circuit Terminating Equipment. Sets up and maintains a data connection link over a communications medium. For example, a modem.
Data Compression
Some modems have the capability to 'squash' data so that it takes up less space. When another modem (that also has this capability) receives the data, it 'unsquashes' the data to its original form. By using data compression, a modem can send information faster. It's a lot like shorthand--all the information is still there, but it takes less space and is quicker. [See also MNP-5, V.42bis].
.
Data Transmission rate
The speed at which data travels. For example, data may be sent at 115,200bps. Same as transmission rate, transmission speed, data rate. [See also bps].
dBm
Decibel refers to one milliwatt. This is used to measure certain levels, such as transmit level.
DSA
Data Services Adapter, an alternative interface to PCMCIA for connecting to a fax or data terminal. The Siemens S1 uses a DSA
Digital
A system using discrete numbers to represent data. In computer systems, these are the numbers 0 and 1 (for binary). [See also Analogue].
DSR
Data Set Ready. This indicates that the modem is on, and ready to accept input from the computer (either commands or data to be sent over the phone line)
DTE
Data Terminal Equipment. This is computer equipment which is not directly responsible for communicating, for example, the computer itself and printers. [See also DCE].
DTMF
Dual Tone Multi-Frequency. This is used in tone dialing. It is a method where 2 distinct tones are sent for each digit dialed.
DTR
Data Terminal Ready. The DTR signal is sent from the computer to the modem, to let the modem know that the computer is ready to communicate.
E
EDI
Electronic Data Interchange. Commonly transferred by Internet or X.400 networks
EEPROM
Electrically Erasable Programmable Read-Only Memory
EFF
Electronic Frontier Foundation. An organization promoting civil rights in cyberspace. It is leading the fight against the US government's Clipper Chip.
Error Correction
Error Correction. The ability of a modem to notice errors in transmission, and to resend incorrect data. [See also MNP 1-4, LAPM, V.42].
ETSI
European Telecommunications Standards Institute.
ECFP
European Conference on Computers, Freedom, and Privacy.
Electronic mail. Messages that are sent to individual people. You choose who to send the message to and only that person receives the message.
ESPRIT
European Strategic Program for Research in Information Technologies.
Error
When there is line noise and one or more characters are changed. This is especially noticeable when downloading or uploading a program. In this case the error must be detected, and the data must be re-sent.
F
FAQ
Frequently Asked Questions.
Firewall
Computer security that attemps to keep crackers out.
Flame
To write emotional remarks on electronic mail.
Flow control
A method of controlling when information is sent. One method is Xon/Xoff, where a BBS will send information until your computer sends an Xoff (CTRL-S). It will resume sending information when you send an Xon. [See also Xon/Xoff, CTS/RTS].
Full Duplex
A channel providing simultaneous transmission in both directions.
G
GMSK
The method of modulation used by GSM is Gaussian Minimum Shift Keying (GMSK), with a BT value of 0.3 at a gross data rate of 270 kb/s.
Group III FAX
The standard controlling fax communication.
GSM
GSM originally stood for Groupe Speciale Mobile but has been anglicised to Global System for Mobile Communications, an international digital cellular standard. South Africa was one of the first to implement Phase 2 of GSM.
Click here for a brief history of GSM.
H
Half Duplex
A channel which signals in both directions, but not simultaneously.
Handover
What occurs when a cell phone used in a car moves out of the range of one cell and needs to connect to the next available cell. The preceding cell then hands over the connection to the stronger cell.
Hayes AT command set
This is the set of commands used to operate Hayes modems and Hayes compatible modems. Almost all of the commands start with AT.
Hayes compatible
Any modem which operates in the same way as the modems developed by Hayes.
Hertz
A unit of frequency, which equals cycles per second.
I
Interactive Manual
A Windows-based modem control and diagnostic program bundled free with each Option 2-in-1 modem. Here you can alter all Hayes AT commands using icons! Just click on the appropriate icon, and the Interactive Manual will instantly alter the modem's settings. You can also change the modem's settings to conform to the PTT specifications of different countries.
ISO
The International Standards Organisation, the body responsible for setting world technical standards. It is based in Geneva, Switzerland.
ITU
International Telecommunications Union, based in Geneva, Switzerland.
IWU
InterWorking Unit. This is the network "modem" where all the digital to analogue (and visa versa) conversions take place within the digital GSM networks
J
K
L
Lotus
Famous for the Lotus 1-2-3 spreadsheet of the 1980's, and more recently for it's Notes Groupware system. Bought by IBM in 1995.
M
Microsoft
The world's largest developer and publisher of software based in Redmond, Seattle, USA. Headed by William (Bill) Gates, the richest (non-royal) person on this planet.
Modulation
A process whereby a signal is transformed from its original form into a signal that is more suitable for transmission over the medium between transmitter and receiver.
Mosaic
A GUI (Graphical User Interface) for accessing the hypertext WWW (World Wide Web) on the Internet.
MNP
Microcom Networking Protocol. Error control and data compression techniques, created by Microcom, that many newer modems use. They are built into the modem, unlike software error correction in file transfer protocols. There are different MNP levels. Levels 1-4 are error control protocols, and level 5 is a data compression protocol that can compress data to about 50% of its original size. A modem with MNP-5 also has MNP-4. MNP 1-4 is also included in the ITU V.42 error correction system.
MNP normal mode
This is the more common mode used with modems that have MNP capability, where the speed from the computer to the modem can be higher than the connection between the modem and the remote modem. This mode uses buffering to prevent lost data.
MoU
Memorandum of Understanding, the GSM body that overseas GSM standards and implementation around the world. It comprises operators and some manufacturers.
Modem
A MOdulator DEModulator computer peripheral which allows a computer to communicate over telephone lines. This is the heart of computer telecommunications. The main factor that differentiates modems is their speed, measured in bps. Analogue modems talk to one another by converting digital info from the computer into tones called PSK’s. An ordinary analogue modem cannot be physically connected to a GSM phone because networks will not carry PSK tones.
N
NCAIR
National Center for Automated Information Research.
Network Operators
The folks who install and maintain GSM cellular networks. Click here to see a list of GSM operators around the world. Click here to see the South African network operators.
Non-Transparent Cellular Data
Non Transparent phones use a special error correction technique called RLP. Transparent phones data not incorprate the RLP error corerction techniqure and their data MIGHT be corrupted.
O
P
PABX
Private Branch Exchange. This is the telephone system that many offices have, allowing extensions for each telephone, and a connection to the main telephone system.
Parity Bit
Most modems have the capability to send an extra bit for every byte sent, which is used to help sense errors. This is called the parity bit. It can be set to no parity, mark parity, space parity, odd parity or even parity. Most BBS's do not use a parity bit. [See also 8-N-1].
PC Cards
Previously known as PCMCIA cards, these are credit card devices used in notebooks and desktop readers for inter alia, data/fax, storage, GPS puposes.
PCMCIA
A credit card sized card that generally plugs into a notebook computer. It conforms to the Personal Computer Memory Card International Association spec. Now known as PC Cards.
PSK
Phase Shift Keying. In this method of modulation/demodulation, there are two frequencies used (usually 1200 hertz and 2400 hertz). There are 4 different phase angles (0, 90, 180, and 270 degrees), representing dibits 00, 01, 10, and 11. This is usually used for 1200bps transmission. Note that the baud rate using PSK is really 1/2 of the bps rate, since 2 bits are sent at a time instead of one. [See also modulation].
PSTN
Public Switched Telephone Network. This is the regular phone lines that just about everybody uses.
Phreaker
Aperson who spends a lot of time trying to find out as much as possible about the telephone company [like South Africa's TELKOM], and how it works. They often try to find out ways to make long distance calls for free. Some steal calls from telephone credit card users, some steal calls from the phone company directly, and others don't make "free" long distance calls. They are sometimes confused with hackers.
PKZIP
The program which will create an archive with the extension "ZIP". It is one of the most popular archive programs.
Pulse dialing
A method that some phones use to dial numbers. It involves a series of "clicks." Most modems support this type of dialing, which is the only type available in some remote areas. The other method of dialing is tone dialing.
Q
R
RLP
Radio Link Protocol
Non-transparent data uses a special ensure robust GSM-specific error correction technique called RLP for transmission. Both MTN and Vodacom GSM networks support both techniques.
RPE-LPE
Regular Pulse Excitation - Long Term Prediction, the speech coding used by GSM
RACE
Research and Development in Advanced Communication in Europe.
Reset
A modem can be reset. This will change any options (such as parity and speed) to the values that they have when the modem is first used. This can be useful if you change some values for the modem and aren't sure what they do, and then you find that the modem won't work. Resetting the modem will fix everything for you. With Option modems, this is the ATZ command.
RJ-11
This is a normal phone jack. The older South African plugs have a 3-prong connector. All Option modems sold in South Africa have this RJ-11-to-3-prong adapters.
RTS
Request To Send. This is when the computer tells the modem that it wants to send information to the other computer. It is only used in half duplex mode. [See also flow control, CTS].
S
Serial Transmission
A method of transmitting data in which bits are sent sequentially.
SIG
Special Interest Group. The GSM MoU has many SIGS.
SIM
Subscriber Identity Module. This is a Smart Card installed in every GSM handset. Within the GSM application the three primary roles of the SIM are access control to the network (authentication & ciphering), service personalisation (SMS, advice of charge, etc.), network branding and advertising (graphics printed on SIM card). The new generation of Phase 2+ SIMs will enable services such as virtual cash, mobile banking, ticket reservations etc.
SMS
Short Message Service will display a pager-like 160 character message in the LCD panel on the phone. Your phone must support SMS.
Streaming
When data is sent continuously, without waiting to make sure there are no errors. Transparent mode on GSM is an example of a streaming method faster than non-transparent mode, but unreliable.
T
T1
Trunk 1. A heavy duty telephone line.
T3
Trunk 3. A telephone trunk line.
TDMA
Time Division Multiple Access, the magical technique used by the digital GSM network to squeeze more calls onto one channel by dividing a calling channel into a few "discontinuous" pieces.
Telecommunication(s)
This word has no precise definition, but is frequently used. Its definition ranges from "any form of communication over a distance" to "any communication by electric means" to "two computers 'talking' to each other via modems." Methods of communications that probably are considered telecommunications: telephones, cellphones, TV's and fax machines. The word is used both in singular and plural.
Telecommuting
The idea of company employees working from home, rather than their office. At home, they can communicate with the office (and other entities) by modem or voice calls.
Telkom (South Africa)
Telkom is the parastatal fixed-line network operator in South Africa. Option modems are approved for use on the telkom network and 25 other networks around the world.
TELNET
A program which lets you access other computer systems through Internet.
Terminal Emulation
When a communications program can simulate the operations of a smart terminal.
Tone Dialing
This is a method that a phone or modem can use to dial a phone number. It uses one audible tone per digit to be dialed.
Transmit Level
The "loudness" level of the sound leaving a modem to go over the phone lines. It is measured indBm's. It should be different at different frequencies, since certain frequencies have more loss over the phone line than others.
Transparent Data Transmission
A method of transmission in which the transmission medium will not recognize control characters or initiate any control function. Transparent-based phones do not utilise any error correction. Thus the data sent and received MIGHT be corrupted unless a greater than two-bar cellphone signal is used (South African conditions). Non-transparent data uses a special ensure robust GSM-specific error correction technique called RLP for transmission. Both MTN and Vodacom GSM networks support both techniques.
U
UART
Universal Asynchronous Receiver/Transmitter. This is a device in a computer or modem that will change serial data (the way data comes in over the phone line) to parallel, and vice versa. [See also serial, parallel, 16550 UART, 8250 UART, 16450, 16550 UART].
V
V.17
The ITU standard for fax transmission at 14,400bps.
V.21
The international standard, created by ITU, that controls transmission at 300bps.
V.22
The international standard for transmission at 1200bps, created by ITU.
V.22bis
The international standard, created by ITU, that controls data transmission at 2400bps.
V.23
The ITU protocol for transmission of 1200bps one way, 75bps the other way.
V.24
This, combined with V.28 is the ITU standard equivalent to EIA's RS-232C standard. V.24/V.28 has 25 pins, just like the original RS-232C standard.
V.28
Part of V.24.
V.29
The ITU standard for 9600bps half-duplex communications.
V.32
The international standard controlling transmission at 9600bps. It was created by ITU. It has provisions for fallback, if the line is too noisy.
V.32bis
The international standard for 14,400 bps modems, ratified by the ITU.
V.34
The international standard for 28,800 bps modems, ratified by the ITU.
V.42
A standard error control system created by ITU that is in use on many 9600bps modems and some 2400bps modems. It includes LAPM, as well as MNP 2-4.
V.42 compatible
This is a modem that follows all the V.42 specifications, except for LAPM error control (instead it uses MNP).
V.42 compliant
This is a modem which follows all the V.42 specifications, and uses LAPM error control if possible. Otherwise, it will go to MNP error control.
V.42bis
A ITU standard for data compression. It can compress data with about a 3:1 compression ratio, although it can compressup to 4:1 given the right conditions. Any modem with V.42bis also has V.42 error control. [See also Data Compression].
W
W3
World Wide Web
WWW
World Wide Web. A hypertext system set up on the Internet.
Waffle
A DOS program to perform UUCICO.
Winsock
A Windows subroutine library that provides access to the Internet TCP/IP.
WINSOCK.DLL
The actual file containing Winsock.
X
X.25
This is a packet-switching protocol developed by ITU. It is used to carry large amounts of data at fast speeds over leased phone lines.
X.32
This is ITU's 1984 update of X.25, also known as X.25 dialup.
X.400
This is the ITU standard protocol for a global system for the exchange of electronic mail.
X.500
The ITU standard for a directory of the users of the X.400 system.
Xmodem
A file transfer protocol developed by Ward Christensen around 1977. It is fairly slow by today's standards, but was the first widespread file transfer protocol. It uses blocks of 128 bytes, and after each block is sent, it sends a 1 byte checksum to check for errors. If an error is encountered, the block will be re-sent. Almost every communications program offers this protocol.
Xmodem/CRC
The same as Xmodem, but it has a 16-bit CRC instead of the checksum, which makes it more reliable (it catches more errors).
Xmodem-1K
This is similar to Xmodem/CRC, except it uses blocks of 1024 bytes, rather than 128. It is faster than Xmodem, since it needs to stop less often to check for errors. This is sometimes incorrectly called Ymodem. [See also protocol, Xmodem, Ymodem].
Xoff
The CTRL-S character. This is often used to pause information that is being sent. The information will be continued when an CTRL-Q is received. [See also flow control, Xon].
Xon
The CTRL-Q character. This will sometimes continue paused information.
Xon/Xoff
The flow control method using the Xon and Xoff characters. It is built into the software, not the hardware.
Y
Z
ZIP
The file extension which refers to archives that were created by the program PKZIP. You need the program PKUNZIP to get the files out of the archive.
Zmodem
A file transfer protocol which is known for its speed, as well as the ability to transfer information about the files which it sends. It has crash recovery and auto-download features, and can use a 32 bit CRC, which makes it almost error-free.
#
8-N-1
The most common modem format. "8N1" describes the way that your computer and the remote are connected. The first digit is normally 7 or 8, the number of data bits. The second character is a letter describing the parity (N for None, M for Mark, S for Space, O for Odd, and E for Even). The last number is the number of stop bits. Data is sent as follows: Start bit (0) 7 or 8 bits of data (parity bit, if used) stop bit (1) (gap bits, if used)
10BASE-T
An ethernet connection that uses UTP (unshielded twisted-pair) wiring.
16550 UART
This is the UART used with most newer computers and high speed modems. There are several variations, but they all include one main feature: they include buffering, so that if data comes in or is sent faster than the computer/modem can accept it, the UART will hold the data (up to 16 bytes) until the computer/modem is ready for it.
Source: www.cellular.co.za/glossary.htm
Monday, October 26, 2009
Huawei, ZTE racing ahead in Optical Network market
TT Correspondent | New Delhi | 26 Oct 2009
Chinese vendors Huawei and ZTE are seen leading the global market for Optical Networks with Alcatel-Lucent and NEC making the list of top four firms.
ZTE claims that its market share for Q2 2009 is 16.1 % while four-quarter market share is 12 %.
The optical network market in Asia-Pacific region grew by 24 % on a yoy comparison. Ovum estimates the market to scale past $ 5.8 billion by year-end. China and India will contribute the most to this market. In Q2 2009, the revenues reached $ 3.8 billion with ZTE witnessing the highest qoq revenues increase at 213 %.
The EMEA region saw sales drop to $ 4.84 billion in Q2 2009 mainly because of the ongoing economic crisis in Western Europe.
Source:www.telecomtiger.com/Technology_fullstory.aspx?passfrom=Technology&storyid=7491§ion=S210
Chinese vendors Huawei and ZTE are seen leading the global market for Optical Networks with Alcatel-Lucent and NEC making the list of top four firms.
ZTE claims that its market share for Q2 2009 is 16.1 % while four-quarter market share is 12 %.
The optical network market in Asia-Pacific region grew by 24 % on a yoy comparison. Ovum estimates the market to scale past $ 5.8 billion by year-end. China and India will contribute the most to this market. In Q2 2009, the revenues reached $ 3.8 billion with ZTE witnessing the highest qoq revenues increase at 213 %.
The EMEA region saw sales drop to $ 4.84 billion in Q2 2009 mainly because of the ongoing economic crisis in Western Europe.
Source:www.telecomtiger.com/Technology_fullstory.aspx?passfrom=Technology&storyid=7491§ion=S210
BSNL bestows Amara Raja with ‘Best Telecom Equipment Manufacturer’ award for VRLA Batteries
TT Correspondent | Bangalore | 26 Oct 2009
Amara Raja Batteries Ltd bagged BSNL’s ‘Best Telecom equipment Manufacturer’ award for its VRLA batteries.
VRLA batteries today provide critical back up power for the telecom networks including remote mobile transmission stations spread across the length and breadth of India.
S. Vijayanand, SBU Head – Industrial Batteries, Amara Raja, “It is a great honour to win this recognition from BSNL. This award not just sets the benchmark but also inspires us to continue our focus on research and customer service to better serve our customers. We are proud to have partnered BSNL with our VRLA battery technology with the “ready to install and use” feature which has enabling faster roll out of mobile network infrastructure. Batteries continue to play a critical role in keeping the uptime of telecom networks near 100%. As the rural network expands bringing more and more remote locations into the connectivity grid, batteries will gain more importance from this perspective.”
Jay Galla, Managing Director, responding to the award thanked BSNL for bestowing the recognition. Recollecting the initial experience of pioneering the VRLA technology in India Mr. Galla commented, “We are privileged to receive this recognition from BSNL. When we introduced VRLA technology to India in the early 90s, it was clearly generations ahead of the battery technology used in the country at that time. During our early efforts in establishing VRLA technology, the Department of Telecommunications showed great vision in adopting the new generation battery technology and encouraged us with their support.
Source:www.telecomtiger.com/Corporate_fullstory.aspx?passfrom=corporate&storyid=7495&flag=1§ion=S162
Amara Raja Batteries Ltd bagged BSNL’s ‘Best Telecom equipment Manufacturer’ award for its VRLA batteries.
VRLA batteries today provide critical back up power for the telecom networks including remote mobile transmission stations spread across the length and breadth of India.
S. Vijayanand, SBU Head – Industrial Batteries, Amara Raja, “It is a great honour to win this recognition from BSNL. This award not just sets the benchmark but also inspires us to continue our focus on research and customer service to better serve our customers. We are proud to have partnered BSNL with our VRLA battery technology with the “ready to install and use” feature which has enabling faster roll out of mobile network infrastructure. Batteries continue to play a critical role in keeping the uptime of telecom networks near 100%. As the rural network expands bringing more and more remote locations into the connectivity grid, batteries will gain more importance from this perspective.”
Jay Galla, Managing Director, responding to the award thanked BSNL for bestowing the recognition. Recollecting the initial experience of pioneering the VRLA technology in India Mr. Galla commented, “We are privileged to receive this recognition from BSNL. When we introduced VRLA technology to India in the early 90s, it was clearly generations ahead of the battery technology used in the country at that time. During our early efforts in establishing VRLA technology, the Department of Telecommunications showed great vision in adopting the new generation battery technology and encouraged us with their support.
Source:www.telecomtiger.com/Corporate_fullstory.aspx?passfrom=corporate&storyid=7495&flag=1§ion=S162
In a quad play world, wireless nets hold the key
Mike Jude/Frost & Sullivan | October 22, 2009
Almost everyone is familiar with the term "triple play," that is, voice, video and data services offered by a single service provider. The notion originated with cable operators that found they had the capability to deliver multiple discrete services over the same cable network. This capability was quickly matched by telephone carriers that were able to provide voice and data over the same copper plant and video through partnerships with satellite service providers. Recently, some telecom carriers also started offering IPTV over the same DSL-based connections.
Now the stakes have been raised. The new bar is defined by the "quadruple play," or voice, video, data and wireless services. Adding wireless to the service bundle increases the value of the total bundled offering and provides the consumer with a single bill for all of their communications services. What many operators have forgotten, however, is that the point of service bundling is not the convenience of getting a single bill. If that were the case, consumers would be willing to pay more for bundled services. The fact that they aren't, and that service bundles are following the same price-to-cost curve as discrete services, is an indication that simple bundling is not really a high-value pursuit.
Perceived value is based on the perceived utility of the service being offered. Simple bundling and single billing do not necessarily add to utility; they simply make consumption more convenient. High-value service bundling is what's needed, and this is where service integration comes in.
Service integration, or services that are independent of the delivery network, is becoming the high-value offering for network operators. This trend is described in the new Stratecast report, Triple Play or Triple Loss: Service Packaging Forecast and Strategic Analysis. Where simple bundling provides discrete services, most of which are confined to individual networks, integrated services live across the delivery networks.
One example serves to illustrate: Mediafriends, a network service software provider, has technology that allows text messaging to appear on a wireless device, a PC and a video display. In this environment, text messaging is a highly integrated service accessible to consumers regardless of which device they may be using or which network is actually delivering the service.
Source:www.telecomasia.net/content/quad-play-world-wireless-nets-hold-key
Almost everyone is familiar with the term "triple play," that is, voice, video and data services offered by a single service provider. The notion originated with cable operators that found they had the capability to deliver multiple discrete services over the same cable network. This capability was quickly matched by telephone carriers that were able to provide voice and data over the same copper plant and video through partnerships with satellite service providers. Recently, some telecom carriers also started offering IPTV over the same DSL-based connections.
Now the stakes have been raised. The new bar is defined by the "quadruple play," or voice, video, data and wireless services. Adding wireless to the service bundle increases the value of the total bundled offering and provides the consumer with a single bill for all of their communications services. What many operators have forgotten, however, is that the point of service bundling is not the convenience of getting a single bill. If that were the case, consumers would be willing to pay more for bundled services. The fact that they aren't, and that service bundles are following the same price-to-cost curve as discrete services, is an indication that simple bundling is not really a high-value pursuit.
Perceived value is based on the perceived utility of the service being offered. Simple bundling and single billing do not necessarily add to utility; they simply make consumption more convenient. High-value service bundling is what's needed, and this is where service integration comes in.
Service integration, or services that are independent of the delivery network, is becoming the high-value offering for network operators. This trend is described in the new Stratecast report, Triple Play or Triple Loss: Service Packaging Forecast and Strategic Analysis. Where simple bundling provides discrete services, most of which are confined to individual networks, integrated services live across the delivery networks.
One example serves to illustrate: Mediafriends, a network service software provider, has technology that allows text messaging to appear on a wireless device, a PC and a video display. In this environment, text messaging is a highly integrated service accessible to consumers regardless of which device they may be using or which network is actually delivering the service.
Source:www.telecomasia.net/content/quad-play-world-wireless-nets-hold-key
Microsoft net falls 18% but beats views
By Jerry A. DiColo and Jessica Hodgson, Dow Jones Newswires
Friday 23 October 2009
Shares boosted by strong demand for Windows, Xbox video game system.
Microsoft Corp.'s fiscal first-quarter earnings fell 18%, but strong presales of the company's new Windows 7 operating system and better-than-expected overall results added to the growing optimism about a consumer-driven technology recovery.
The news Friday sent Microsoft shares to their highest level since June 2008.
The results, a quarter after Microsoft's first fiscal year of declining sales as a public company, showed strong expectations for the just-launched Windows 7, demonstrated high demand for Microsoft's Xbox videogames and underscored that rigorous cost controls during the downturn had paid off.
One negative note in a broadly upbeat earnings statement: business spending on PCs, the engine of Microsoft's revenue and profit growth, has yet to make a comeback.
"Our strong performance is primarily as a result of two factors: consumer demand for Windows and Xbox, and excellent cost controls," Chris Liddell, Microsoft's chief financial officer, said on a conference call with analysts.
Microsoft reduced its full-year operating expense estimate by $300 million to $26.2 billion.
"2009 may well have been the bottom of the economic reset," he said, cautioning that there is still precious little evidence of a broader recovery in business PC sales.
Liddell said he expected sales of Windows 7 to consumers to be "very strong," but "the big variable in terms of rebound is going to be the strength and speed of the business PC rebound."
Microsoft's overall revenue declined for the third consecutive quarter, underscoring how the recession is still taking a toll on almost every part of its business. The company posted the first quarterly revenue decline in its 23-year history as a public company in April.
Despite the cautious tones, investors welcomed the results, pushing Microsoft's stock up as much as 10.4% to $29.35. The stock, in midday trading, was recently up 7.1% to $28.47.
"This is a strong endorsement of consumer recovery and also points to the stabilization of the Windows business," said Katherine Egbert, analyst with Jefferies & Co.
The slump in global PC sales and broad economic weakness have battered Microsoft's results over the past year, compounding already weakened demand for the unpopular Windows Vista operating system. On Thursday, the company moved to recharge revenue ...
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growth with the launch of Windows 7, its next-generation operating system.
After seeing revenue drops across all five of its businesses in the June quarter, Microsoft saw growth in the September quarter in its server and tools division, up 0.5%, while its entertainment unit remained roughly flat with last year.
Revenue for its Windows unit, Microsoft's largest division, dropped 39% from last year, and earnings for the division fell 52%; however, after stripping out the impact of the deferred revenue from the launch of Windows 7, revenue declined by around 4%, beating analysts' expectations.
"The stability in their Windows business for the first time in a year, and obviously the fact that they are able to defer a lot more Windows revenue going forward, bodes very well," Broadpoint AmTech analyst Yun Kim said."It was the first time in a year that it came in in line with consensus."
The deferred revenue from pre-sales of Windows 7 totaled $1.47 billion, exceeding Microsoft's estimate of about $1.2 billion. With deferred revenue, earnings would have been 52 cents a share.
For the quarter ended Sept. 30, Microsoft reported earnings of $3.57 billion, or 40 cents a share, down from $4.37 billion, or 48 cents a share, a year earlier. Revenue declined 14% to $12.92 billion. Analysts polled by Thomson Reuters had expected earnings of 32 cents a share on revenue of $12.37 billion.
In online services, a small but important division that includes Bing.com, revenue decreased 5.8% to $490 million, slightly below consensus estimates.
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Source:www.totaltele.com/view.aspx?ID=450109&Page=1
France OKs legislation to cut Internet to illegal downloaders
From AFP
Friday 23 October 2009
First warning letters to persistent file-sharers to be sent next year.
France will send out the first warnings to digital pirates early next year after passing tough legislation allowing for Internet access to be cut for those who illegally download movies and music, a minister said.
The Constitutional Court passed the law Thursday to the joy of President Nicolas Sarkozy and anger of Internet libertarians in France and other countries which are considering copying the French example.
Culture Minister Frederic Mitterrand said the members of a watchdog to oversee application of the digital clampdown would be named in November and the first warnings would go out "from the start of 2010."
Click here to find out more!The law sets up an agency that will send out an e-mail warning to people found to be illegally downloading films or music. A written warning is sent if a second offense is registered in six months and after a third, a judge will be able to order a one-year Internet rights suspension or a fine.
Mitterrand called the law an "innovative and educational mechanism to prevent piracy."
Sarkozy said:"France now has a very innovative system to protect the rights of authors, artists and their partners in the Internet universe."
But in a reference to complaints about the restrictions, the French president said all sides had to work to make sure "there is a civilized Internet."
France's Society of Drama Authors and Composers welcomed the new digital protection and said the government should now consider making search engines pay towards "the financing of creation."
But opponents say it won't prevent illegal file-sharing and that cutting Internet access is unfair because of the commercial and now political importance of having the Worldwide Web.
Reporters Without Borders, a media watchdog, said the law was "a serious blow to freedom of expression on the Internet."
It said access to the Internet was a "fundamental right at the basis of our democracy: the right of access to information. They will have to be extremely vigilant in the way this law is applied," the group said in a statement.
La Quadrature Du Net, a group that had campaigned against the law, called it "legally and technically absurd."
The Socialist Party had referred the law to the Constitutional ...
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Court but the left was also divided with many artists traditionally following the party but also supporting the right wing government's move. The court had blocked the law once but this time only rejected an article which allowed for damages to be claimed from digital pirates.
The U.K. is considering a similar law to France and the European Commission said Thursday it was now looking at Europe-wide regulation for trans-national Internet trade. In a study released Thursday, it raised the possibility of copyright legislation to work alongside national laws and also talks of "alternative forms of remuneration" for authors such as a tax on Internet access.
It estimates the cultural and creative market has an annual turnover of more than EUR650 billion and employs about 3% of the EU's working population.
Click here to find out more!Viviane Reding, EU commissioner for the information society and media, said it would be a "priority" to put in place a legal framework to boost digital trade within the internal frontiers while "guaranteeing" the protection of authors rights and offering a "just remuneration" for creators.
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Source:www.totaltele.com/view.aspx?C=0&ID=450116
Thursday, October 22, 2009
fiber optics
A technology that uses glass (or plastic) threads (fibers) to transmit data. A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves.
Fiber optics has several advantages over traditional metal communications lines:
- Fiber optic cables are less susceptible than metal cables to interference.
- Data can be transmitted digitally (the natural form for computer data) rather than analogically.
The main disadvantage of fiber optics is that the cables are expensive to install. In addition, they are more fragile than wire and are difficult to splice.
Fiber optics is a particularly popular technology for local-area networks. In addition, telephone companies are steadily replacing traditional telephone lines with fiber optic cables. In the future, almost all communications will employ fiber optics.
Source:www.webopedia.com/TERM/F/fiber_optics.htm
Wednesday, October 21, 2009
packet switching
Refers to protocols in which messages are divided into packets before they are sent. Each packet is then transmitted individually and can even follow different routes to its destination. Once all the packets forming a message arrive at the destination, they are recompiled into the original message.
Most modern Wide Area Network (WAN) protocols, including TCP/IP, X.25, and Frame Relay, are based on packet-switching technologies. In contrast, normal telephone service is based on a circuit-switching technology, in which a dedicated line is allocated for transmission between two parties. Circuit-switching is ideal when data must be transmitted quickly and must arrive in the same order in which it's sent. This is the case with most real-time data, such as live audio and video. Packet switching is more efficient and robust for data that can withstand some delays in transmission, such as e-mail messages and Web pages.
A new technology, ATM, attempts to combine the best of both worlds -- the guaranteed delivery of circuit-switched networks and the robustness and efficiency of packet-switching networks.
Source:www.webopedia.com/TERM/p/packet_switching.html
Tuesday, October 20, 2009
Telecommunication Glossary
This reference table is provided for your use, so that you may further understand many of the features and benefits provided by CommWorld Northwest and Toshiba Phone Systems.
ACD (Automatic Call Distributor) - a system that handles incoming call traffic, sending calls to the first available station within predefined groups. If all stations are busy then a recorded message is played and the call is put in queue until a station becomes available.
Analog - a transmission method using continuous electrical signals, varying in amplitude or frequency in response to changes of sound, light, position, etc. impressed on a transducer in the sending unit. The opposite of analog is DIGITAL.
Architecture - the arrangement and design orchestrating the interaction of different elements of a complex communications system. (See also OPEN ARCHITECTURE)
Asynchronous - A transmission method in which information is transferred one discrete character at a time and is delineated by a start and stop indicator at the beginning and end of the character. The opposite of asynchronous is SYNCHRONOUS transmission.
ATM (Asynchronous transfer mode) - Not the money machine! This is an international CCITT standard for high-speed [broadband] packet-switched networks that operates at digital transmission speeds above 1.544 Mbps. This communications protocol specifies how diverse kinds of traffic are transformed into standardized packets which can be managed uniformly within the network.
Attendant - an operator of a PBX console or telephone switchboard.
Bandwidth - The relative range of frequencies that can be passed without distortion by a transmission medium. Greater bandwidths mean a higher information carrying capacity of the transmission circuit. Bandwidth, usually measured in Hertz, is assessed as the number of bits that can be transferred per second.
B channel - Message-bearing 64 Kbps digital channel specified in the ISDN standards. B channels are used for digital transmission of high speed data and video.
Bell Atlantic - One of seven regional bell operation companies (RBOC's) that assumed ownership of the Bell operating companies following AT&T's breakup.
Bell System - Prior to Jan. 1, 1984, an aggregate term for AT&T encompassing 24 Bell operating companies providing local exchange phone service, the AT&T Long Lines Division providing long distance connections, an equipment manufacturing arm known as Western Electric, and a research and development arm known as Bell Laboratories. The Bell System was broken up by the AT&T divestiture.
B-ISDN (Broadband integrated services digital network) - An evolving CCITT international standard for the second generation of integrated services digital networks. Broadband ISDN services will be carried on fiber-optic networks that employ packet switching in a standardized fashion to integrate voice, data, monochrome, and color facsimile images and one-way and two-way monochrome and color video for local and long distance transmission.
Bit - The smallest unit of digital information utilized by electronic or optical information processing, storage, or transmission systems. Bit is short for binary digit. Binary technology is based on the representation of data with 0's and 1's, whose combinations form a protocol medium for all data transmission.
Byte - The smallest unit of information that a computer system can locate within its data storage or memory. A byte consists of eight bits and represents an amount of information roughly equivalent to a single printed or typewritten character.
Call Forwarding - A feature permitting the user to program a phone to ring at an alternate location; call forwarding may be in effect at all times or just when a particular phone is busy or doesn't answer.
Call Hold - A feature allowing the user to put one caller on hold while other calls are made or answered.
Call Park - A feature allowing a call for a busy extension to be put into a hold-like state until someone at that extension or another extension becomes free to answer it. The call is brought out of "park" by dialing a special code.
Call Transfer - A feature allowing a call to be transferred to another phone
Call Waiting - A feature that provides audible or visual indicators to let a single-line-phone user know that she has another call waiting for her.
Caller ID - A telephone company service allowing the subscriber to view the phone number and/or name of the calling party on a display device before answering the phone. Caller ID usually requires some kind of hardware phone interface to provide the displayed information.
Camp-on - In PBX and hybrid environments, a method of putting an incoming or outgoing call intended for a busy extension or line into a hold-like state where it remains until a line becomes available.
Card - A flat piece of rigid material bearing electronic components and the printed circuitry that interconnects them. Cards typically have one point where connections to other cards or components are made.
CCITT (Consultative Committee on International Telegraph and Telephone - the principle international standards-writing body for digital telecom networks (ISDN).
CO (Central Office) - A facility of a telecommunications common carrier where calls are switched. In local area exchanges, central offices switch calls within and between the 10,000-line exchange groups that can be addressed uniquely by the area code and first three digits of a phone number.
Closed System - A computer or communications system whose technical specifications are withheld from distributors, users and other third parties. Closed systems are available only from the manufacturer and its authorized dealers; cloning of closed systems is not tolerated. Buyers of a closed system are limited to the applications programs that the system manufacturer chooses to develop or support. Also known as a proprietary system.
Codec (Coder/Decoder) - a device that transforms analog input into a digitally coded output and transforms digital signals into analog output. They are most commonly found in videoconferencing systems because of videoconferencing's intensive ISDN usage.
Common Carrier - A government-regulated private company offering telecommunications services or communications facilities to the general public.
Conference Call - A telephone call among three or more parties. The sound quality of conference calls is typically degraded by a loss of sound over the telephone lines unless bridged and amplified before re-transmission.
Data Compression - Techniques to reduce the amount of computer memory space or transmission resources required to handle a given quantity of data usually achieved through the application of mathematic algorithms to the data transformation process.
dB - Abbreviation for decibel. The decibel is the standard unit of measure for expressing the amount of signal power gained or lost in the course of a transmission.
D Channel - The signaling and data transmission channel (specified in ISDN standards) used to transmit network control signals for setting up phone calls.
Dedicated Line - A communications circuit or channel provided for the exclusive use of a particular subscriber - also known as a private line.
DID (Direct Inward Dialing) - When a call is received over the DID circuit it is preceded by a packet of information containing the number that was dialed. The on premises phone system decodes this information and routes the call to the extension that has been programmed to coincide with the number dialed. The benefit to the consumer is a pooled access group for incoming calls so that dedicated lines are not required to provide numerous individual telephones with direct access availability.
Digital Switch - Equipment used to set up pathways between users for transmission of digital signals.
DTMF (Dual Tone Multi Frequency Signaling) - Most commonly associated with AT&T's Touch-Tone trade name.
Duplex - Simultaneous transmission in both directions, sometimes referred to as full duplex to differentiate it from half duplex, which is alternating transmission in each direction. Transmission in only one direction is called simplex transmission.
800 Service - A telecommunications service for businesses that allows calls to be made to a specific location at no charge to the calling party. Use of the "800" service access code denotes that calls are to be billed to the receiving party.
Encoder/Decoder - A device used to transform signals from an originating terminal into groups of digital pulses representing letters, numerals, or specific symbols, and transform incoming digital pulses into the form required by the receiving terminal.
Ethernet - A popular local area data communications network, originally developed by Xerox Corp., which accepts transmissions from computers and terminals.
Facilities - Transmission lines, switches and other physical components used to provide telephone service.
Fax - A method of transmitting graphics or text documents over a telecommunications facility. The image is scanned at the transmitter and reconstructed at the receiver to be duplicated on paper.
Fiber Optics - Technology based on thin filaments of glass or other transparent materials used as the medium for transmitting coded light pulses that represent data, image and sound. Fiber optic technology offers extremely high transmission speeds.
Full Duplex - A communications system or channel capable of simultaneous transmission in two directions. See Duplex.
Gateway - A network element interconnecting two otherwise incompatible networks, network nodes, subnetworks or devices.
Half Duplex - A communications channel allowing alternating transmission in two directions, but not in both directions simultaneously.
Hybrid - A combination of two or more technologies or a multiline business telephone system combining the manual line selection of a key system and the automatic line selection of a PBX system.
Interconnect - A company or vendor selling customer premises equipment, generally PBXs and other types of office telephone systems. An interconnect company is typically an independent distributor of products from more than one manufacturer.
ISDN (Integrated Services Digital Network) - Switched network providing end - to -end digital connectivity for simultaneous transmission of voice and/or data over multiple multiplexed communications channels and employing transmission and out-of-band signaling protocols that conform to internationally defined standards.
IVR (Interactive Voice Response) - A generic term for transaction systems allowing phone callers to use an ordinary tone-dialing telephone to interact with a computer through speech or dialed instructions. Each response by the caller triggers another recorded message until the transaction is completed.
Key Telephone System - A multiline telephone system offering a limited range of features; key systems are popular among smaller businesses as their main telephone system. They are also found in large businesses as a form of extension to their big primary phone system. Key systems are characterized by manual selection of outgoing lines, their small size, and relatively low price.
LAN (Local Area Network) - A transmission network encompassing a limited area, such as a single building or several buildings in close proximity; widely used to link personal computers so that they can share information and peripheral devices.
LED (Light-Emitting Diode) - A semiconductor light source that emits light in the optical frequency band or the infrared frequency band.
Local Loop - The communications channel, usually a physical line, between the subscriber's location and his local central office. Also known as the subscriber loop.
Loop Start - A method of demanding dial tone from the central office by completing an electrical pathway between the outbound and return conductors of a telephone line. Loop start is employed by single-line telephone instruments, for example.
Measured Service - Term generally associated with providing local telephone service on a usage-sensitive basis with calls priced on the basis of two or more of the following usage elements: distance, duration, frequency, and time of day. It is the opposite of flat rate pricing.
Message Rate - A form of usage-sensitive pricing for local telephone service where usage charges are figured by counting the calls and multiplying the number of calls made by the established per-call charge. An alternative to flat-rate and measured pricing.
Modem (Modulator-Demodulator ) - An electronic device that allows computers to communicate over standard telephone lines. It transforms digital signal into analog signal and transmits to another modem which then reconstructs the digital signal from the analog signal.
Multiplexed Channel - A communications channel capable of serving several devices, or users, at once
Multiplexing - An electronic or optical process that combines a large number of lower-speed transmission lines into one high-speed line by splitting the total available bandwidth of the high-speed line into narrower bands (frequency division), or by allotting a common channel to several different transmitting devices, one at a time in sequence (time division). Multiplexing devices are widely employed in networks to improve efficiency by concentrating traffic.
Mux - An abbreviated form of the word multiplexer.
Network - Any system designed to provide one or more access paths for communications between users at different geographic locations that may include designs for voice, data, facsimile images and/or video images.
Network Architecture - A set of design principles defining the protocol, functions and logical components of a network and how they should perform.
Network Interface - The physical point in a telephone subscriber's home or place of business where the telephone devices and/or inside wiring of the subscriber are connected to the transmission lines of the local telephone service provider.
OEM (Original Equipment Manufacturer) - The manufacturer of equipment that is resold by another vendor who usually substitute their name for that of the manufacturer on the product.
Off-Hook - A telephone set in use - the handset is removed from its cradle, thus sending an electrical signal to the central office that a circuit needs to be opened.
Off-Line - The condition where a terminal or device capable of active connection with the facilities of a computer or communications network is in the disconnected or idle state.
1A2 - Widely-used type of electromechanical key system that were introduced by the Bell System in 1938 and reached their technological peak in the mid-1960's.
On-Hook - The normal state of the phone in which the handset rests in the cradle and the circuit to the central office conducts no electrical signal.
On-Line - The condition where a terminal or device capable of active connection with the facilities of a communications network or computer is in the active or connected state; a unit functioning under the continual control of a computer.
Open Standard - A computer or communications standard whose technical specifications are readily available to equipment manufacturers and other parties that want to incorporate the standard into their products or systems.
Open System - A computer or communications system whose technical specifications are readily available to distributors, users and other third parties that want to add value to the system by developing their own customized versions for use or resale. Open systems are widely cloned.
Operating System - A special program in the communications CPU or computer that controls the integration of operating devices and enables the running of specific applications software - which is software developed to perform specific jobs.
Packet - a group of binary digits switched as a whole - for instance, a file transfer over a packet switched network would require many steps. These steps are: 1) the data file would be broken down into smaller "packets" of information 2) each packet of information is assigned a code that enables it to be sent to the correct location and, once at that location, for the network to reassemble the packets of information into their original form.
Packet Switched Network - A digital data transmission network that uses packet switching technology.
Packet Switching - a digital data transmission method that divides messages and files into standard-size pieces - called packets - that are switched across networks individually and then reassembled at their destination.
Paging - A service designed to deliver numeric or alphanumeric messaging to a person whose location is uncertain - paging services make use of radio communications.
PBX (Private Branch Exchange) - A device, installed on the customer's premises, that enables switching of multiple incoming and outgoing lines between multiple internal phones. In addition, the typical PBX provides for the selection of outside lines per user defined criteria.
Port - An interface location on a computer or communications system that provides a point of access for peripheral equipment, such as printers, voice mail, C.O. Lines, etc.
POTS Lines (Plain Old Telephone Service Lines) - Basic telephone lines whose primary purpose is the transmission of human speech.
Private Line - A telephone line that is linked directly to a user and is used exclusively by that user.
Private Network - A network that is designed for use exclusively by a person or organization and usually does not have points of access from users external to the company.
Programming Language - A group of symbols that represent to the computer a set of statements or directions giving the computer or communications system detailed instructions about what operations it is to perform.
Proprietary System - See closed system.
Protocol - A format or set of rules and conventions that control the format and relative timing of message transmission between two points on a computer network.
Public Switched Network - A switching system that provides switching and transmission facilities to many customers.
Queue - A "holding room" for data or voice communications that are waiting to be processed by either the system or human intervention.
RBOC (Regional Bell Operating Corporation) - One of seven regional companies created by the AT&T divestiture to take over ownership and operation of the Bell companies within their region.
Real Time - A transmission or data processing operational mode in which the data is entered in an interactive (two-way communicating) session; an application where response to input is fast enough to affect later data input.
Redundancy - Having back-up systems available to provide continuous service in the case of a failure in the main system
Remote Access - Sending and receiving data to and from a computer through communications links such as phone lines.
Remote Call Forwarding - Similar to call forwarding. Calls from a local telephone number can be forwarded to long distance number (in another city for example) without the caller be charged for long distance fees.
Serial Transmission - Sending pulses (information) one right after another. The opposite would be a parallel transmission.
SMDR (Station Message Detail Reporting) - Information recorded by a computer attached to the phone system, providing cost accounting information such as the number of calls, both local and long distance, made from an extension during a certain time period.
Speed Dial - A feature on PBX phones allowing users to dial programmed numbers by simply pressing one button (or entering a two or three digit code).
Station - Simply another word for telephone. For example, the telephone station may be one of many extensions on a PBX system.
Station Hunting - A feature allowing an incoming call to a busy phone to be routed to the next idle phone in a pre-determined group of phones.
Switched Line - A circuit which is routed through a circuit switched network.
Switching - Connecting the caller to the called party.
Synchronous Transmission - Transmissions of data at a fixed rate, eliminating the need for start and stop bits, because the receiver and transmitter work at the same rate.
TCP/IP (Transmission Control Protocol/Internet Program) - Protocols linking dissimilar computers across networks. TCP/IP was developed by the Department of Defense
TDMA (Time Division Multiple Access) - Multiple conversations are separated by dividing bandwidths into finite frequencies., where each call is assigned a transmission timeslot.
Telecommunications - Process of converting sounds and data into electrical impulses that can be transmitted (See Telephony).
Telecommuting - Using a communications link to perform work, rather than actually commuting to an office to do work.
Teleconference - A conference which links people by audio and/or video through telecommunications.
Telemarketing -Using the telephone as a primary means of initiating and making sales of products or services.
Telephony - The process of converting sounds into electrical impulses for transmission over a connecting medium such as wires, fiber optics or microwave.
Terminal - The point of connection between a telephone line and an operative device. Also, sometimes terminal refers to the operative device, such as a computer terminal.
Tie Line - A telephone line which is dedicated to connecting two points and which requires a minimum human intervention to achieve communication.
Token Ring -A method of controlling which of several work stations in a Local Area Network is transmitting at a particular time.
Toll Restriction - A method of controlling which employees, if any, have access to telephone lines for which a toll may be charged to the employer.
T-1 - A digital transmission link capable of handling 1.544 Mega bits per second.
Trunk - The line of communication between switching systems.
T-3 - 28 T-1 lines (See T-1).
Turnkey - A ready-to-go telephone system installed by the vendor, including both hardware and software.
Twin-Axial Cable - Two commonly insulated conductors, covered by a metallic shield and enclosed in a cable sheath.
Twisted Pair - Two copper wires twisted around each other. The twists vary in length and reduce induction.
Videoconferencing - Video teleconferencing (See teleconferencing).
Voice Digitization - Coverting analog signals (voice) into binary bits for storage and transmission.
Voice Response - A computer allowing users interaction via touchtone telephone. Users navaigate the system with the help of digitally read menus.
WAN (Wide Area Network) - A network that extends LANs to other LANs, typically over a wide geographical area using communications lines provided by a common-carrier.
Source:commworldnw.tripod.com/Glossary.html
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