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Glossary of Terms |
| Alphabetical List |
| Below is a list of terms which apply to DSL technology. |
| Access Network |
| That portion of a public switched network that con- nects access nodes to individual subscribers. The Access Network today is predominantly passive twisted pair copper wiring. |
| Access Nodes |
| Points on the edge of the Access Network that con- centrate individual access lines into a smaller number of feeder lines. Access Nodes may also perform various forms of protocol conversion. Typical Access Nodes are Digital Loop Carrier systems concentrating individual voice lines to T1 lines, cellular antenna sites, PBXs, and Optical Network Units (ONUs). |
| ADSL |
| Asymmetric Digital Subscriber Line: Modems attached to twisted pair copper wiring that transmit from 1.5 Mbps to 9 Mbps downstream (to the sub- scriber) and from 16 kbps to 800 kbps upstream, depending on line distance. |
| APON |
| ATM Passive Optical Network: a passive optical network running ATM. |
| ATM |
| Asynchronous Transfer Mode: an ultra high speed cell based data transmission protocol which may be run over ADSL |
| ATM 25 |
| ATM Forum defined 25.6Mbit/s cell based user interface based on IBM token ring network. |
| ATU-C and ATU-R |
| ADSL Transmission Unit, Central or Remote: the device at the end of an ADSL line that stands bet- ween the line and the first item of equipment in the subscriber premises or telephone switch. It may be integrated within an access node. |
| BDSL |
| Same as VSDL |
| B-ISDN |
| Broadband Integrated Digital Network: A digital net- work with ATM switching operating at data rates in excess of 1.544 or 2.048 Mbps. ATM enables transport and switching of voice, data, image, and video over the same infrastructure. |
| CATV |
| Community Access Television: also known as Cable TV. |
| Core Network |
| Combination of switching offices and transmission plant connecting switching offices together. In the U.S. local exchange Core Networks are linked by several competing Interexchange networks; in the rest of the world (now) the Core Network extends to national boundaries. |
| CPE |
| Customer Premises Equipment: that portion of the ADSL system residing within the customer's premises. |
| CSA |
| Carrier Serving Area: area served by a LEC, RBOC or telco, often using Digital Loop Carrier (DLC) technology. |
| DSLAM |
| Digital Subscriber Line Access Multiplexer: specifically, a device which takes a number of ADSL subscriber lines and concentrates these to a single ATM line. |
| DS0 |
| Digital Signal 0: 64 kbps digital representation of voice. |
| DS1 |
| Digital Signal 1: Twenty four voice channels packed into a 193 bit frame and transmitted at 1.544 Mbps. The un- framed version, or payload, is 192 bits at a rate of 1.536 Mbps. |
| DS2 |
| Digital Signal 2: Four T1 frames packed into a higher level frame transmitted at 6.312 Mbps. |
| DSL |
| Digital Subscriber Line: Modems on either end of a single twisted pair wire that delivers ISDN Basic Rate Access. |
| E1 |
| European basic multiplex rate which packs thirty voice channels into a 256 bit frame and transmitted at 2.048 Mbps. |
| Feeder Network |
| That part of a public switched network which connects access nodes to the core network. |
| FEXT |
| Far End CrossTalk: the interference occurring between two signals at the end of the lines remote from the telphone switch. |
| FTTCab |
| Fibre To The Cabinet: network architecture where an optical fiber connects the telephone switch to a street-side cabinet where the signal is converted to feed the subscriber over a twisted copper pair. |
| FTTH |
| Fibre To The Home: network where an optical fibre runs from telephone switch to the subscriber's premises or home. |
| FTTK or FTTC |
| Fiber To the Kerb: a network where an optical fiber runs from telephone switch to a kerbside distribution point close to the subscriber where it is converted to a copper pair. |
| HFC |
| Hybrid Fibre Coax: a system (usually CATV) where fibre is run to a distribution point close to the subscriber and then the signal is converted to run to the subscriber's premises over coaxial cable. |
| HDSL |
| High data rate Digital Subscribe Line: Modems on either end of one or more twisted pair wires that deliver T1 or E1 speeds. At present T1 requires two lines and E1 requires three. See SDSL for one line HDSL. |
| ISDL |
| Uses ISDN transmission technology to deliver data at 128kbps into an IDSL "modem bank" connected to a router. |
| ISP |
| Internet Service Provider: an organization offering and prov- iding Internet services to the public and having its own computer servers to provide the services offered. |
| LAN |
| Local Area Network. |
| LEC |
| Local Exchange Carrier: one of the new U.S. telephone access and service providers that have grown up with the recent U.S. deregulation of telecommunications. |
| Loop Qualification |
| The process of determining if a line (or loop) will support a specific type of DSL transmission at a given rate. |
| MPEG |
| Motion Picture Experts Group: the group that has defined the standards for compressed video transmission. |
| NAP |
| Network Access Provider: another name for the provider of net- worked telephone and associated services, usually in the U.S. |
| NEXT |
| Near End CrossTalk: the interference between pairs of lines at the telephone switch end. |
| N-ISDN |
| Narrowband ISDN: same as ISDN. |
| NSP |
| Network Service Provider: the term for an organization offering and providing value added network services on a telecommunications network. |
| NTE |
| Network Termination Equipment: the equipment at the ends of the line. |
| OC3 |
| Optical Carrier 3: an optical fibre line carrying 155mbps; a U.S. designation generally recognized throughout the telecommunications community worldwide. |
| ONU |
| Optical Network Unit: A form of Access Node that converts optical signals transmitted via fiber to electrical signals that can be transmitted via coaxial cable or twisted pair copper wiring to individual subscribers. |
| PON |
| Passive Optical Network: the usual acronym for a fibre based transmission network containing no active electronics. |
| POTS |
| Plain Old Telephone Service: the only name recognized around the world for basic analog telephone service. POTS takes the lowest 4kHz of bandwidth on twisted pair wiring. Any service sharing a line with POTS must either use frequencies above POTS or convert POTS to digital and interleave with other data signals. |
| PTT |
| The generic European name usually used to refer to state owned telephone companies. |
| RADSL |
| Rate Adaptive ADSL: a version of ADSL where the modems test the line at start up and adapt their operating speed to the fastest the line can handle. |
| RBOC |
| Regional Bell Operating Company: one of the seven U.S. Telephone companies that resulted from the break up of AT&T. |
| Splitter |
| A filter to separate ADSL signals from POTS signals to pre- vent mutual interference. |
| SDSL |
| Symmetric Digital Subscriber Line: HDSL plus POTS over a single telephone line. This name has not been adopted by a standards group, but is being discussed by ETSI. It is important to distinguish, however, as SDSL operates over POTS and would be suitable for symmetric services to premises of individual customers. |
| STS-1 |
| SONET basic transmission rate of 51.84 Mbps. |
| T-1 |
| Same as DS1. |
| Telco |
| The generic name for telephone companies throughout the world which encompasses RBOCs, LECs, and PTTs. |
| TPON |
| Telephony over Passive Optical Network: telephony using a PON as all or part of the transmission system between tele- phone switch and subscriber. |
| UDSL |
| Unidirectional HDSL as proposed by one company in Europe without much sign of interest from anyone else. |
| VADSL |
| Very high speed ADSL: same as VDSL (or a subset of VDSL, if VDSL includes symmetric mode transmission) |
| VDSL |
| Very high data rate Digital Subscriber Line: Modem for twisted-pair access operating at data rates from 12.9 to 52.8 Mbps with corres- ponding maximum reach ranging from 4500 feet to 1000 feet of 24 gauge twisted pair. |
| WAN |
| Wide Area Network: Private network facilities, usually offered by public telephone companies but increasingly available from alternative access providers (sometimes called Competitive Access Providers, or CAPs), that link business network nodes. |
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