LMDS (Local Multipoint Distribution System)

LMDS (Local Multipoint Distribution System) is a system for broadband microwavewireless transmission direct from a local antenna to homes and businesses within a line-of-sight radius, a solution to the so-called last-mile technology problem of economically bringing high-bandwidth services to users. LMDS is an alternative to installing optical fiber all the way to the user or to adapting cable TV for broadband Internet service. Depending on the implementation, LMDS offers a bandwidth of up to 1.5 Gbpsdownstream to users and 200 Mbps upstream from the user. A more typical data rate is 38 Mbps downstream. Some services offer both downstream and upstream service (symmetrical service); others offer downstream only (asymmetrical service) with upstream being obtained using wire connections.

In addition to the investment by service providers for transmitters, users need to install transceivers costing about $125-225. However, the cost of installing LMDS is considered far lower than installing fiber optic cable or upgrading cable TV systems. The first markets for LMDS are seen as:

  • High-speed data transmission for businesses
  • Interactive television and streaming multimedia from Web sites
  • Voice service (usually as a supplement to other services)

Because LMDS requires a more expensive and possibly larger transceiver than can conveniently be packaged in a handheld device, LMDS is not viewed as a replacement for or alternative to mobile wireless technologies such as cellular and GSM. On the other hand, LMDS offers much higher data rates because of its use of a higher range of frequencies with their wider bandwidths. In general, LMDS is for fixed locations and offers higher data rates; cellular digital such as GSM is for mobile users at lower data rates (although these will increase with technologies leading up to UMTS).

LMDS uses the range of electromagnetic radiation spectrum in the vicinity of 28 GHz, with the allocated range differing slightly between the U.S., Canada, and other countries. In Europe, ETSI sponsors an equivalent technology. In Canada, it is called Local Multipoint Communication Service (LMCS). Like cellular telephone technologies, LMDS is point-to-multipoint. It is viewed as a future component in the convergence of data and telephony services. Ericsson’s LMDS system uses either EthernetATM, or T-carrier system/E-carrier system network interfaces at the user end. ATM allows the user to select and pay for varying qualities of service.