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.
The BRS band uses microwave frequencies from 2.5 GHz to 2.7 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 turners (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.
CelPlan implemented the full extent of the FCC regulations for MMDS in a product called CellFCCTM.
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) is a broadband wireless access technology originally designed for digital television transmission (DTV). It was conceived as a fixed wireless, point-to-multipoint technology for utilization in the last mile. LMDS commonly operates on microwave frequencies across the 26 GHz and 29 GHz bands. In the United States, frequencies from 31.0 through 31.3 GHz are also considered LMDS frequencies.
Throughput capacity and reliable distance of the link depends on common radio link constraints and the modulation method used – either phase-shift keying or amplitude modulation. Distance is typically limited to about 1.5 miles (2.4 km) due to rain fade attenuation constraints. Deployment links of up to 5 miles (8 km) from the base station are possible in some circumstances such as in point-to-point systems that can reach slightly farther distances due to increased antenna gain.
LMDS showed great promise in the late 1990s and became known as “wireless cable” for its potential to compete with cable companies for provision of broadband television to the home. The Federal Communications Commission auctioned spectrum for LMDS in 1998 and 1999.
Despite its early potential and the hype that surrounded the technology, LMDS was slow to find commercial traction. Many equipment and technology vendors simply abandoned their LMDS product portfolios.
Industry observers believe that the window for LMDS has closed with newer technologies replacing it. Major telecommunications companies have been aggressive about deploying alternative technologies such as IPTV and fiber to the preimises, also called “fiber optics”. Moreover, LMDS has been surpassed in both technological and commercial potential by LTE and WiMAX standards.
Although some operators use LMDS to provide access services, LMDS is more commonly used for high-capacity backhaul for interconnection of networks such as GSM, UMTS, WiMAX and Wi-Fi.
