TV - MMDS - Inglês

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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, Australia, Nigeria, Pakistan, Sri Lanka, and India usually in sparsely populated rural areas, where laying cables is not economically viable.

Technology

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.

Current Status

In the United States the Wireless Cable services never materialized, in large part due to investment scams by popular radio talk-show hosts, and the fact that ATSC digital television would fill the needs envisioned for MMDS. Starting in 2006, MMDS frequencies in the 2110-2155 MHz range are being re-allocated for the Advanced Wireless Services. Bidding for this new spectrum by the FCC started on August 9, 2006, effectively killing MMDS and Wireless Cable in the United States.

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 Sri Lanka, Comet Cable (Ruhuna Multivision) offers analogue MMDS television services. The company currently provides 18 channels, though Comet Cable will lose these frequencies with the introduction of WiMAX services.

In Iceland, 365 Broadcast Media offers digital MMDS television services using DVB-T technology alongside a few analog channels.