Point-to-multipoint terrestrial radio

Written on 10:55 AM by ooe

Cellular networks provide the most common form of mobile access, with radio channels being assigned to establish connections to customers requiring service. Whilst the service capability of current mobile networks is extensive, the maximum bandwidth available to an individual customer remains somewhat limited, although increasing with the introduction of 3G technologies.

Wireless local loop (WLL) is a radio alternative to twisted pair copper networks. These systems provide point-to-multipoint radio transmission from a base station to a fixed network termination. In current commercial products, an n × 32 kbit/s link is provided to each customer on demand (n is 1 or 2). Speech paths are provided over 32 kbit/s digital compressed speech channels (adaptive differential PCM, or ADPCM). Two main product groupings currently exist: the Digital European standard for Cordless Telephony (DECT) in the 800 MHz band, where the cell size is typically up to 1 km, and proprietary systems operating at high frequencies and hence larger cell radii (several km is typical). Evolution of these two classes of systems is occurring in different directions: DECT towards some limited mobility (within the same base station area), and the larger cell systems towards ISDN basic rate capability. Convergence of DECT and cellular technology (WLL for ‘home’ use, GSM for roaming away from home) is already taking place, with dual mode DECT/GSM handsets in commercial production.

A limited number of manufacturers are producing broadband (multiple 2 Mbit/s per customer) point-to-multipoint radio which is being deployed in a number of locations around the world. Just as for WLL systems, bandwidth is assigned to customers on demand, even if the capacity required changes during a period of communication over the link. However, this is a separate technology to WLL and is not an evolutionary path from it.