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cell

cell definition - telecom

In asynchronous transfer mode (ATM) and Switched Multimegabit Data Service (SMDS) networks, a small protocol data unit (PDU) comprising 53 octets.The ATM cell consists of a header of 5 octets and payload of 48 octets.The small cell size offers the advantage of effectively supporting any type of data, including voice, fax, text, image, video, and multimedia, whether compressed or uncompressed and whether real-time or non-real-time. The fixed cell size offers the advantage of predictability, unlike the variable-length frames associated with services such as X.25, frame relay, and Ethernet, or the variablelength packets associated with the Internet Protocol (IP).This level of predictability yields much improved access control and congestion control. See also ATM, compression, Ethernet, frame relay, header, IP, non-real-time, packet, payload, PDU, real-time, SMDS, and X.25.
In radio systems, a relatively small geographical area of coverage determined by factors such as frequency band, power level, and line of sight (LOS).The formal concept of radio cells dates back to 1947, when Bell Telephone engineers developed a radio system concept that included numerous, low-power transmit/receive antennas positioned throughout a metropolitan area. This sort of architecture served to increase the effective subscriber capacity of radio systems by breaking the area of coverage into cells, or smaller areas of coverage. Thereby, each frequency band could be reused in nonadjacent cells. Additionally, the cells can be split, or subdivided, further as the traffic demands of the system increase. In the context of radio telephony, including cellular telephony, cells can be characterized as falling into three broad descriptive categories, as illustrated in Figure C-2.

Webster's New World Telecom Dictionary Copyright © 2008 by Wiley Publishing, Inc., Indianapolis, Indiana.
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