MMDS (Multichannel Multipoint Distribution Service) - TACS

Multichannel Multipoint Distribution Service (MMDS), formerly known as Broadband Radio Service (BRS) and also known as Wireless Cable, is a wireless telecommunications technology, used for general-purpose broadband networking or, more commonly, as an alternative method of cable television programming reception. It is most commonly used in sparsely populated rural areas, where laying cables is not economically viable.

The BRS band uses microwave frequencies from 2.3 GHz to 2.5 GHz. Reception of BRS-delivered television and data signals is done with a rooftop microwave antenna. The antenna is attached to a down-converter or transceiver to receive and transmit the microwave signal and convert them to frequencies compatible with standard TV tuners (much like on satellite dishes where the signals are converted down to frequencies more compatible with standard TV coaxial cabling), some antennas use an integrated down-converter or transceiver. Digital TV channels can then be decoded with a standard cable set-top box or directly for TVs with integrated digital tuners. Internet data can be received with a standard DOCSIS Cable Modem connected to the same antenna and transceiver.

The MMDS band is separated into 33 6 MHz "channels" (31 in USA) which may be licensed to cable companies offering service in different areas of a country. The concept was to allow entities to own several channels and multiplex several television, radio, and later Internet data onto each channel using digital technology. Just like with Digital Cable channels, each channel is capable of 30.34 Mbit/s with 64QAM modulation, and 42.88 Mbit/s with 256QAM modulation. Due to forward error correction and other overhead, actual throughput is around 27 Mbit/s for 64QAM and 38 Mbit/s for 256QAM.

The newer BRS Band Plan makes changes to channel size and licensing in order to accommodate new WIMAX TDD fixed and mobile equipment, and reallocated frequencies from 2150–2162 MHz to the AWS band. These changes may not be compatible with the frequencies and channel sizes required for operating traditional MMDS or DOCSIS based equipment.

Local Multipoint Distribution Service (LMDS) and BRS have adapted the DOCSIS (Data Over Cable Service Interface Specification) from the cable modem world. The version of DOCSIS modified for wireless broadband is known as DOCSIS+.

Data-transport security is accomplished under BRS by encrypting traffic flows between the broadband wireless modem and the WMTS (Wireless Modem Termination System) located in the base station of the provider's network using Triple DES.

MMDS provided significantly greater range than LMDS.

MMDS may be obsoleted by the newer 802.16 WiMAX standard approved since 2004.

MMDS was sometimes expanded to Multipoint Microwave Distribution System or Multi-channel Multi-point Distribution System. All three phrases refer to the same technology (Wiki).

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