Thursday, August 7, 2008

Local Multipoint Distribution System (LMDS)

Definition and Overview

Local multipoint distribution system (LMDS) is the broadband wireless technology used to deliver voice, data, Internet, and video services in the 25-GHz and higher spectrum (depending on licensing).

As a result of the propagation characteristics of signals in this frequency range, LMDS systems use a cellular-like network architecture, though services provided are fixed, not mobile. In the United States, 1.3 MHz of bandwidth (27.5 B 28.35 GHz, 29.1 B 29.25 GHz, 31.075 B 31.225 GHz, 31 B 31.075 GHz, and 31.225 B 31.3 GHz) has been allocated for LMDS to deliver broadband services in a point-to-point or point-to-multipoint configuration to residential and commercial customers. This tutorial details the underlying technology inherent in offering voice, data, Internet, and video services over LMDS through integration with the wireline environment.

The acronym LMDS is derived from the following:

* L (local)—denotes that propagation characteristics of signals in this frequency range limit the potential coverage area of a single cell site; ongoing field trials conducted in metropolitan centers place the range of an LMDS transmitter at up to 5 miles
* M (multipoint)—indicates that signals are transmitted in a point-to-multipoint or broadcast method; the wireless return path, from subscriber to the base station, is a point-to-point transmission
* D (distribution)—refers to the distribution of signals, which may consist of simultaneous voice, data, Internet, and video traffic
* S (service)—implies the subscriber nature of the relationship between the operator and the customer; the services offered through an LMDS network are entirely dependent on the operator's choice of business

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