Local Multipoint Distribution Service
Encyclopedia
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
.
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 premises, also called "fiber optics". Moreover, LMDS has been surpassed in both technological and commercial potential by the developing WiMax
standard.
for interconnection of networks such as GSM, UMTS, WiMAX
and Wi-Fi
.
Digital television
Digital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...
(DTV). It was conceived as a fixed wireless, point-to-multipoint
Point-to-multipoint
Point-to-multipoint communication is a term that is used in the telecommunications field which refers to communication which is accomplished via a specific and distinct type of one-to-many connection, providing multiple paths from a single location to multiple locations.Point-to-multipoint is often...
technology for utilization in the last mile
Last mile
The "last mile" or "last kilometer" is the final leg of delivering connectivity from a communications provider to a customer. The phrase is therefore often used by the telecommunications and cable television industries. The actual distance of this leg may be considerably more than a mile,...
.
LMDS commonly operates on microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
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
Phase-shift keying
Phase-shift keying is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal ....
or amplitude modulation
Amplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
. Distance is typically limited to about 1.5 miles (2.4 km) due to rain fade
Rain fade
Rain fade refers primarily to the absorption of a microwave radio frequency signal by atmospheric rain, snow or ice, and losses are especially prevalent at frequencies above 11 GHz. It also refers to the degradation of a signal caused by the electromagnetic interference of the leading edge of a...
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
Antenna gain
In electromagnetics, an antenna's power gain or simply gain is a key performance figure which combines the antenna's directivity and electrical efficiency. As a transmitting antenna, the figure describes how well the antenna converts input power into radio waves headed in a specified direction...
.
United States
LMDS showed great promise in the late 1990s and became known as "wireless cable" for its potential to compete with cableCable television
Cable television is a system of providing television programs to consumers via radio frequency signals transmitted to televisions through coaxial cables or digital light pulses through fixed optical fibers located on the subscriber's property, much like the over-the-air method used in traditional...
companies for provision of broadband television to the home. The Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
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
IPTV
Internet Protocol television is a system through which television services are delivered using the Internet protocol suite over a packet-switched network such as the Internet, instead of being delivered through traditional terrestrial, satellite signal, and cable television formats.IPTV services...
and fiber to the premises, also called "fiber optics". Moreover, LMDS has been surpassed in both technological and commercial potential by the developing WiMax
WiMAX
WiMAX is a communication technology for wirelessly delivering high-speed Internet service to large geographical areas. The 2005 WiMAX revision provided bit rates up to 40 Mbit/s with the 2011 update up to 1 Gbit/s for fixed stations...
standard.
Europe and worldwide
Although some operators use LMDS to provide access services, LMDS is more commonly used for high-capacity backhaulBackhaul (telecommunications)
In a hierarchical telecommunications network the backhaul portion of the network comprises the intermediate links between the core network, or backbone, of the network and the small subnetworks at the "edge" of the entire hierarchical network...
for interconnection of networks such as GSM, UMTS, WiMAX
WiMAX
WiMAX is a communication technology for wirelessly delivering high-speed Internet service to large geographical areas. The 2005 WiMAX revision provided bit rates up to 40 Mbit/s with the 2011 update up to 1 Gbit/s for fixed stations...
and Wi-Fi
Wi-Fi
Wi-Fi or Wifi, is a mechanism for wirelessly connecting electronic devices. A device enabled with Wi-Fi, such as a personal computer, video game console, smartphone, or digital audio player, can connect to the Internet via a wireless network access point. An access point has a range of about 20...
.