Short-range radio systems are used for many purposes for telemetry, remote control and games, as well as for communications. Communications uses include cordless telephony, radio local area networks (RLANs), radio fixed access and microcellular systems. For some of these applications, very low powers are used, with poor and poorly located antennas where the user only expects the range to be of the order of a few metres. For example, for remote car door locks, the user will expect to point the transmitter towards the car and probably has some understanding of the need to provide a near line-of-sight path. For such appli cations there seems to be very little requirement to attempt to provide good propagation models. For RLANs and other indoor applications there will be a need for some kind of generic modelling of the effects of the room size and shape, obstructions in the room, the construction materials and the penetration through walls and floors. For high-speed data transmission, it may also be necessary to model the multipath time spreads. But for outdoor microcellular systems and similar applications it will be necessary to model propagation at distances ranging out to a kilometre or so, where the longer-range area coverage prediction methods may take over. 1 km is the dividing distance used by the ITU-R in its Recommendations between short-range and longer-range prediction methods. However, the above considerations mainly apply to VHF and UHF systems, where although the distances are short the propagation is in the far-field regime and the usual propagation techniques are applicable. Another interpretation of short range would be to consider paths within the near field regime around the transmitting antenna. This is mainly of significance at lower frequencies.

Inspec keywords: radiowave propagation; transmitting antennas

Other keywords: UHF systems; high-speed data transmission; propagation techniques; RLAN; short-range propagation; microcellular systems; cordless telephony; short-range radio systems; radio fixed access; radio local area networks; indoor applications; transmitting antenna; ITU-R; VHF systems; remote control; telemetry

Subjects: Radiowave propagation