Satellite Acronyms & Definitions
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A/D Conversion - (analog-to-digital conversation) The process of converting a time-continuous analog signal to a sampled digital representation.
Adaptive - Refers to the ability of the DCLZ algorithm to "adapt" or change to accommodate differences in the type of data to be compressed.
Algorithm - Systematic means of describing a problem; a procedure for solving a problem in a finite number of steps.
Amplitude Shift Keying- A digital modulation format where information is conveyed in the amplitude of a carrier signal.
Analog - Analog refers to electronic transmission accomplished by adding signals of varying frequency or amplitude to carrier waves of a given frequency of alternating electromagnetic current. Broadcast and phone transmission have conventionally used analog technology. A modem is used to convert analog to digital information to and from your computer.
Asymmetrical links - are ideal for data based communications such as web browsing due to the limited need for uplink and the high need for downlink to display pages. Ideally, bandwidth for web browsing should be assigned to the network asymmetrically as there should be little or no need to provide and pay for the same bandwidth for inbound delivery as is needed for the outbound. Unlike terrestrial networks, with satellite links it is possible to assign bandwidth exactly as required for each direction
Automatic Repeat Request - (ARR) Protocol for dealing with data words that are corrupted by errors whereby the receiving system requests a re-transmission of the word(s) in error.
Bandwidth - The number of cycles per second expressing the difference between limiting frequencies of a band; in digital systems, the measure of the amount of information that can be processed per unit time.
BCH - A type of block coding of data words named after the inventors Bose, Chaudhuri and Hocquenghem.
BER Bit Error Rate - In a digital transmission, BER is the percentage of bits with errors divided by the total number of bits that have been transmitted, received or processed over a given time period. The rate is typically expressed as 10 to the negative power. For example, four erroneous bits out of 100,000 bits transmitted would be expressed as 4 x 10 -5, or the expression 3 x 10 -6 would indicate that three bits were in error out of 1,000,000 transmitted. BER is the digital equivalent to signal-to-noise ratio in an analog system.
BERT Bit Error Rate Test - a procedure or device that measures the bit error rate of a transmission.
Block Codes - A code with a fixed number of bytes.
Broadband - Describing transmission equipment and media that can support a wide range of electromagnetic frequencies; typically, the technology of Cable Antenna Television transmissions, as applied to data communications, that employs coaxial cable as the transmission medium and radio frequency carrier signals in the 50- to 500- MHz range; any communication channel with bandwidth greater than that of a voice-grade telecommunications channel; sometimes used synonymously with wideband.
Buffer - A temporary storage space in a computer system or subsystem; especially one that accepts data at one rate and delivers it at another (to coordinate subsystems that process data at different rates).
Byte - Digital word containing eight information bits (1's or 0's).
CDMA code division multiple access - CDMA is a digital spread-spectrum modulation technique used mainly with personal communications devices such as mobile phones. CDMA digitizes the conversation and tags it with a special frequency code. The data is then scattered across the frequency band in a pseudorandom pattern. The receiving device is instructed to decipher only the data corresponding to a particular code to reconstruct the signal.
Channel Efficiency - In error correction, the ratio of the input information divided by the transmitted information plus code.
Coaxial Cable - A popular transmission medium usually consisting of one central wire conductor (two, for twin axial cable) surrounded by a dielectric insulator and encased in either a wire mesh or an extruded metal sheathing; coaxial cable comes in many varieties, depending on the degree of EMI shielding afforded and voltages and frequencies accommodated; common Community Antenna Television (Cable Antenna Television) transmission cable, typically supporting RF frequencies from 50 to about 500 MHz; also called coax.
Code Division Multiple Access - (CDMA) Method of combining multiple users on a given channel bandwidth using unique spreading codes, or hopping patterns to distinguish and given user.
Code Rate - In error correction, the ratio of information divided by information plus redundancy. Codes with a high code rate are desirable because they efficiently use the available channel for information transmission.
Codec - Semiconductor device containing both an encoder and a decoder. In communications engineering, the term codec is used in reference to integrated circuits, or chips that perform data conversion. In this context, the term is an acronym for "coder/decoder".
Coding Gain - In communications engineering, coding gain refers to the improvement in decibels (dB) that a particular code offers over other option. An improvement in coding gain can provide the designer with options such as reducing transmission power or bandwidth.
Compression Ratio - The ratio of the number of original data bytes to the number of compressed data bytes.
Compression - Any of several techniques that reduce the number of bits required to represent information in data transmission or storage (thus conserving bandwidth and/or memory), in which the original form of the information can be reconstructed; also called "compaction".
Continuous Phase Frequency Shift Keying - (CPFSK) Digital modulation format where information is conveyed in the frequency of a carrier signal ensuring that the phase is continuous between symbol transitions.
D/A Conversion - (digital-to-analog conversation) The process of converting a discrete time digital representation of a waveform to a continuous analog voltage equivalent.
D-TDMA deterministic time division multiple access this technology simply takes TDMA and adds the ability to prioritize types of traffic. This will allow voice and video to be prioritized above data transfers to make the best use of the bandwidth. This technology is used in digital-advanced mobile phone system (D-AMPS) and Global System for Mobile communications (GSM). Packets are transmitted based on priorities established within the router which allow for VoIP and video teleconferencing to transmit first since they are real-time traffic.
DAMA - Demand Assignment Multiple Access -- DAMA is a technique of Satellite resource manipulation that allows many users on a Satellite to share a limited assignment of transponder capacity. As one user connects to the transponder they draw from a common "pool". When that user disconnects the transponder space returns to the pool for other users to access.
Data Coding - Operating on data with an algorithm to accomplish encryption, error correction, compression, or some other feature.
dBc - The level of a signal in dB relative to a wanted carrier signal level.
dBm - The level of a signal in dB relative to 1 m W (0 dBm).
DBS - Direct Broadcast Satellite is a video programming or data delivery service which is delivered via satellite directly to the end-user. An example is DircTV or Echostar.
DC - (Data Compression) A method to encode data by eliminating redundancy. May be implemented in hardware or software.
Density - A measure of how much data is stored in a given area or linear sequence (track) on a specific medium. Density may be measured in Bits per inch or millimeter, in tracks per inch or millimeter, or in bits per square inch or millimeter.
DES - (Data Encryption Standard) A Scheme approved by the National Bureau of Standards that encrypts data for security purposes. DES is the data-communications encryption standard specified by Federal Information Processing Systems (FIPS) Publication 46.
Differential Phase Shift Keying - (DPSK) Digital modulation format where information is conveyed in phase difference of a carrier signal between consecutive symbols.
Differentially Encoded Phase Shift Keying - (DEPSK) Digital modulation format where data is pre-coded to convey information in the change of state between consecutive bits, to overcome the phase ambiguity problem with coherent phase shift keying.
Digital Audio Broadcasting - (DAB) The generic name given to the new generation of radio transmission using digitally encoded audio waveforms.
DVB Digital Video Broadcast This is an all digital as the name indicates, and was originally designed for broadcast video and has been modified to allow various types of traffic.
DVB-S - Digital Video Broadcast via satellite
DVB-C - Digital Video Broadcast via cable
DVB-RCS Digital Video Broadcast, Return Channel via Satellite
Encoding/Decoding - The process of organizing information into a particular format and then reconverting it for use; for pulse-code-modulated voice transmission, the generation of digital signals to represent quantified samples, and the subsequent reverse process.
Ethernet A popular local area network design, the product of Xerox Corp., characterized by 10 Mbps baseband transmission over a shielded coaxial cable and employing CSMA/CD as the access control mechanism; standardized by the IEEE as specification IEEE 802.3; referring to the Ethernet design or as a compatible with Ethernet.
FDMA frequency division multiple access allocates a single channel to one user at a time, if the transmission path deteriorates, the controller switches the system to another channel. Although technically simple to implement, FDMA is wasteful of bandwidth and cannot handle alternate forms of a data, only voice transmissions. This is the basic technology used in cellular phones and is also used in the total access communication systems (TACS).
FEC Forward Error Correction It is a powerful technique for improving the performance of error-prone channels found in communication systems. It is a system of error control for data transmission where the receiving device has the capability to detect and correct any character or code block that contains fewer then a predetermined number of symbols in error. It is intended to improve the capacity of a channel by adding some carefully designed redundant information to the data being transmitted through the channel.
Fiber Optic Transmission technology in which modulated light wave signals., generated by laser or LED, are propagated along a typically glass or plastic medium, and then demodulated to electrical signals by a light-sensitive receiver.
FTDMA frequency time division multiple access The FTDMA features a unique and patented two-dimensional satellite access scheme, which combines the TDMA slotted ALOHA and FDMA techniques. Remote terminals burst in randomly-selected frequency channels at each transmission. Occasional high traffic sites are automatically off-loaded from the shared resources and have dedicated frequency channels allotted to them upstream communications are transmitted using a patented, proprietary technology Frequency/Time Division Multiple Access, or FTDMA. Downstream transmissions, however, use the industry standard Digital Video Broadcast (DVB) carrier.
FSK (Frequency Shift Keying) - Digital modulation format where information is conveyed in the frequency of a carrier signal.
FTP - File Transfer Protocol - A very common method of moving files between two Internet sites. FTP is a special way to login to another Internet site for the purposes of retrieving and/or sending files. There are many Internet sites that have established publicly accessible repositories of material that can be obtained using FTP, by logging in using the account name anonymous, thus these sites are called anonymous ftp servers.
GMSK (Gaussian Minimum Shift Keying) - Digital modulation format where information is conveyed in the frequency of a carrier signal, where the incoming data is first shaped with a Gaussian low-pass filter.
GSM - (Global System for Mobile Communication) - A cellular radio standard using digital GMSK modulation.
G.711 - Describes the 64-kbps PCM voice coding technique. In G.711, encoded voice is already in the correct format for digital voice delivery in the PSTN or through PBXs. Described in the ITU-T standard in its G-series recommendations.
G.723 - Audio (Voice) Compression Protocol reducing the required bandwidth per call, per direction to 8 kbps using adaptive multi-rate wideband.
G.729 - Audio (Voice) Compression Protocol reducing the required bandwidth per call, per direction to 12 kbps using conjugate-structure algebraic-code-excited linear-predication.
Geostationary Orbit circular orbits that are orientated in the plane of the earths equator. The satellite appears stationary.
H.323 - is a protocol for the transmission of real-time audio, video and data information over packet switching-based networks. Such networks include IP-based (including the Internet), Internet packet exchange-based local area networks, enterprise networks and metropolitan and wide area networks. H.323 can also be applied to multipoint-multimedia communications. The technology provides a vast array of services which means it can be used in consumer, business and entertainment applications. H.323 is an essential element in ensuring that the compatibility of the mobile multimedia applications and services will be introduced with the implementation of third generation wireless technologies.
Headers - Blocks of data written at the beginning of cartridges or files that contain specific identification information.
HTPC - Hyper Turbo Product Code is a TPC with an added parity correction code dimension.
HTTP - HyperText Transfer Protocol - The protocol for moving hypertext files across the Internet. Requires a HTTP client program on one end, and an HTTP server program on the other end. HTTP is the most important protocol used in the World Wide Web.
Information Transport - Transferring electronic information or data via electronic, photonic, or any other mans. May be point to point or network, one or two way, also referred to as "communications" or "telecommunications" (same as data transport).
IP - Internet Protocol - is the most basic protocol to communicate on the Internet. An IP number is a numerical address consisting of four numbers separated by periods. Each IP address uniquely identifies a certain computer on the Internet. The domain name is used to make using them easier.
LAN - (Local Area Network) - A network of interconnected workstations sharing the resources of a single processor or server within a relatively small geographic area.
Latency - In a network, latency, a synonym for delay, is an expression of how much time it takes for a packet of data to get from one designated point to another. In some usages latency is measured by sending a packet that will be returned back to the sender and thus the round-trip time is considered the latency.
LNA Lowe Noise Amplifier Special type of amplifier used in communication systems to amplify very weak signals captured by an antenna.
LNB - Low Noise Block take a block or band of relatively high frequencies and convert them to similar signals carried at much lower frequencies (intermediate frequency or IF. These lower frequencies travel through cables with much less attenuation of the signal, so there is much more signal left on the satellite receiver end of the cable. The low noise part means that special electronic engineering techniques are used so that the signal has less noise (unwanted signals) on the output than would be possible with less stringent engineering. If low noise engineering techniques were not used, the sound and picture of satellite would be very low quality if it could be received at all.
LNC Low Noise Converter converters the incoming signal from the satellite (3.6 to 4.2 GHz in the c-band and 10.700 to 12.750 in ku-band) into a lower frequency (900 to 2150 MHz).
Lossless - Characteristic of data compression algorithms such that when compressed data is decompressed, it is identical to the form it had prior to compression.
Lossy - Characteristic of data compression algorithms in which compressed data may not decompress exactly to its original form. Lossy compression is typically capable of very high compression performance, and is used primarily on data which may be slightly changed without significant effect.
MCPC Multi Channel per Carrier This is a byproduct of SCPC combined with TDM (Time division Multiple) voice/data multiplexing that operates in a star configuration
Mesh Topology devices are connected with many redundant interconnections between network nodes. In a true mesh topology every node has a connection to every other node in the network. T he topology of a network whose components are all connected directly to every other component A group of nodes sharing a large number of interconnections, where the interconnections are graphically represented with lines, can be visualized as a mesh.
Minimum Shift Keying - (MSK) - Digital modulation format where information is conveyed in the frequency of a carrier signal with modulation index equal to half the symbol period.
Modulation the transmission of a signal by using it to vary a carrier wave, changing the carriers amplitude or frequency or phase. The process in which electrical encoding or modulation is used to format the information according to the transmission medium.
OC-3 - A telecommunications standard for data rate speeds of 155 Mbits/second.
ON-OFF Keying - (OOK) - Digital modulation format where information is conveyed by switching on and off a carrier signal.
Point to Multipoint - a connection consisting of a central connection endpoint and other peripheral connection endpoints and in which data originating from the central connection endpoint are received by all other connection endpoints and data originating from the peripheral connection endpoints is received only by the central connection endpoint.
Point to point This service requires the incorporation of an earth station as the HUB with connection to needed services. It incorporates various sites with a VSAT to communicate with the HUB.
PSK - Phase-Shift Key - It's a form of phase modulation for digital signals, where the bits are quantified by various phase changes. It involves changing the phase of transmitted waveform instead of the frequency, these finite phase changes representing digital data. In its simplest form, a phase-modulated waveform can be generated by using the digital data to switch between two signals of equal frequency but opposing phase.
QoS Quality of Service - QoS is the set of techniques to manage network resources. QoS enables you to provide better service to certain flows. This is done by either raising the priority of a flow or limiting the priority of another flow.
QPSK Quaternary Phase-Shift Key is a more elaborate form of PSK. Each pair of bits of the incoming sequence causes a change in the carrier phase between four possible states. The carrier undergoes four changes in phase (four symbols) and can thus represent 2 binary bits of data per symbol. Although this may seem insignificant initially, a modulation scheme has now been supposed that enables a carrier to transmit 2 bits of information instead of 1, thus effectively doubling the bandwidth of the carrier.
Quadrature Amplitude Modulation - (QAM) - Digital modulation format where information is conveyed in the amplitude and phase of a carrier signal.
Redundancy - Extra bytes added to data that allows error detection and correction to occur; having backup equipment to ensure the minimal interruption.
RF - Radio Frequency
RS - Reed Solomon Codes are block-based error correcting codes with a wide range of applications in digital communications and storage. These codes are used to correct errors in many systems including storage devices, wireless or mobile communications, satellite communications, digital television, DVB, high-speed modems such as ADSL. The Reed-Solomon encoder takes a block of digital data and adds extra redundant bits. Errors occur during transmission or storage for a number of reasons (for example noise or interference, scratches). The Reed-Solomon decoder processes each block and attempts to correct errors and recover the original data. The number and type of errors that can be corrected depends on the characteristics of the code.
RS-Viterbi - Reed-Solomon/Viterbi coding technology
RTP - Real-time transport protocol - The Internet-standard protocol for the transport of real-time data, including audio and video. RTP is used in virtually all voice-over-IP architectures, for videoconferencing, media-on-demand, and other applications. A thin protocol, it supports content identification, timing reconstruction, and detection of lost packets.
RX - Short for receive
SAP - This protocol is used on NetWare networks to advertise available network services. For example, a NetWare server uses SAP to let other computers know that it's offering up some shared files. This also stands for "Standard Accounting Program," a program on which some large businesses run their accounting.
SCPC Single Channel Per Carrier
S/N ratio - Signal-to-noise ratio
SOHO Small Office, Home Office
SSL - Secured Sockets Layer - a protocol that transmits your communications over the Internet in an encrypted form. SSL ensures that the information is sent, unchanged, only to the server you intended to send it to. Online shopping sites frequently use SSL technology to safeguard your credit card information.
Star Topology - Network designed in the shape of a star, where all end points are connected to one central switching device, or hub. Star networks are easier to manage than ring topology but are slower because every message must pass through the central point.
SER - (Symbol Error Rate) - The probability of receiving a symbol in error (not to be confused with BER)
Symmetrical - or full duplex is for two way communications such as voice or any real time data.
TCC - Turbo Convolutional Codes
TPC Turbo Product Codes These codes have performance approaching the theoretical limit for any error correction code. TPC uses block codes solving multiple steps simultaneously, thereby achieving high data throughput in hardware. They do not suffer from the error floor at low BERs that have been attributed to other codes.
TCP/IP Transmission Control Protocol/Internet Protocol - the suite of communications protocols used to connect hosts on the Internet. TCP/IP uses several protocols, the two main ones being TCP and IPP. TCP/IP is built into the UNIX operating system and is used by the Internet, making it the de facto standard for transmitting data over networks. Even network operating systems that have their own protocols, such as Netware, also support TCP/IP
TDMA time division multiple access is digital transmission technology that allows a number of users to access a single radio-frequency (RF) channel without interference by allocating unique time slots to each user within each channel. Each caller is assigned a specific time slot for transmission.
TX - Short for Transmit
UNIXฎ - Operating system originally designed by AT&T for communicating multi-user, 32-bt minicomputers; has come into wide commercial acceptance because of its predominance in academia and its programming versatility. AT&T System V Version 3 and Berkeley System Development Version 4.3 are currently popular.
VAN - (Value Added Network) - A network whose services go beyond simple switching.
Viterbi Encoding/Decoding is widely used for satellite and other noisy communication channels. There are two important components of a channel using Viterbi encoding: the Viterbi encoder (at the transmitter) and Viterbi Decoder (at the receiver). A Viterbi encoder includes extra information in the transmitted signal to reduce the probability of errors in the received signal that may be corrupted by noise.
VoIP - Voice over Internet Protocol - A technology for transmitting voice, such as ordinary telephone calls, over packet-switched data networks. Also called IP telephony.
VPN - Virtual Private Network - Network scheme in which portions of a network are connected via Internet, but information sent across the Internet is encrypted. The result is a "virtual network" which is also part of a larger network entity. This allows users to privately share private information over a public infrastructure. VPNs are often used to connect offices.
VSAT Very Small Aperture Terminal to receive/transmit terminals installed at dispersed sites connected to a central hub via satellite using small diameter antenna dishes (0.6 to 3.8 meters).
Wideband - A system in which multiple channels access a medium (usually coaxial cable) that has a large bandwidth, greater than that of a voice-grade channel; typically offers higher-speed data-transmission capability. Also see broadband.