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Multichannel Multipoint Distribution Service
Additional recommended knowledge
Multichannel multipoint distribution service, also known as MMDS or 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. MMDS is used in the United States and other countries, including Canada, Mexico, Iceland, Ireland, Brazil, Barbados, Australia, Nigeria, Pakistan, Sri Lanka, Thailand, Uruguay and India usually in sparsely populated rural areas, where laying cables is not economically viable.
The MMDS band uses microwave frequencies from 2 GHz to 3 GHz in range. Reception of MMDS-delivered television signals is done with a special rooftop microwave antenna and a set-top box for the television receiving the signals. The antenna usually has an integrated down-converter to transmit the signals at frequencies compatible with terrestrial TV tuners down on the coax (much like on satellite dishes where the signals are converted down to frequencies more compatible with standard TV coaxial cabling), some larger antennas utilise an external down-converter. The receiver box is very similar in appearance to an analog cable television receiver box.
The MMDS band is separated into eleven "channels" which are auctioned off like other bands. The idea was that entities could own several channels and multiplex several television and radio channels onto each channel using digital technology. Each "channel" was capable of 10 Mbit/s, exclusive of any forward error correction technology that is required for this type of technology.
MMDS and DOCSIS+
LMDS and MMDS 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 MMDS by encrypting traffic flows between the broadband wireless modem and the WMTS (Wireless Modem Termination System) located in the base station of the providers network using Triple DES.
DOCSIS+ reduces theft-of-service vulnerabilities under MMDS by requiring that the WMTS enforce encryption, and by employing an authenticated client/server key-management protocol in which the WMTS controls distribution of keying material to broadband wireless modems.
LMDS and MMDS wireless modems utilize the DOCSIS+ key-management protocol to obtain authorization and traffic encryption material from a WMTS, and to support periodic reauthorization and key refresh. The key-management protocol uses X.509 digital certificates, RSA public key encryption, and Triple DES encryption to secure key exchanges between the wireless modem and the WMTS.
MMDS provides significantly greater range than LMDS.
MMDS may be obsoleted by the newer 802.16 WiMAX standard which is due in 2004.
MMDS is sometimes expanded to Multipoint Microwave Distribution System or Multi-channel Multi-point Distribution System. All three phrases refer to the same technology. MMDS Parabolic antenna MMDS Yagi antenna MMDS Parabolic antenna
In the United States the Only Wireless cable service,based out of Texas, was a company called heartland,they had broadcasts in the Midwest and used microwave dishes for reception.
In certain areas, MMDS is being deployed for use as wireless high-speed internet access, mostly in rural areas where other types of high-speed internet are either unavailable (such as cable or DSL) or prohibitively expensive (such as satellite internet). In Canada, Look Communications offers digital television and wireless bi-directional high speed internet from its MMDS transmitters situated in Ontario and Quebec. Range can be up to 25 km from transmitting towers for its bi-directional internet service. They offer 3 Mbit/s for download (from tower) modulated in QAM and 200 kbit/s for upload (from the tower installed in your home) modulated in QPSK. Similar companies are providing MMDS wireless internet in the United States as well, with CommSpeed being a major vendor in the US market for MMDS-based internet.
In Ireland, Chorus and NTL Ireland both offer separate MMDS services in many regions. Chorus still broadcast 11-channel analogue MMDS in some areas, though with their recent acquisition by Liberty Global Europe (along with NTL Ireland), it is quite likely their systems will be merged and after suitable upgrading the analogue services will be dropped and be replaced by the DVB-C systems used elsewhere.
In Iceland, 365 Broadcast Media offers digital MMDS television services using DVB-T technology alongside a few analog channels.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Multichannel_Multipoint_Distribution_Service". A list of authors is available in Wikipedia.|