A computer-simulation study of user access in a universal digital portable communications system is described. An access algorithm consisting of relative power channel-ranking followed by data error detection is evaluated and compared to an optimal reference in a co-channel interference environment. For typical propagation conditions and radio configurations, it was found that an access algorithm based on the ranking of system channels by relative power provides a viable means of channel selection for the portable radio. It was found that the multiple-block data error check improved transmission quality in a co-channel interference environment, approaching the optimum with respect to the 99% statistical reliability criterion.>

Macroscopic diversity is a technique that can facilitate high quality and ubiquitous communications between low-power portable radiotelephones and data terminals, and radio base stations (ports) that are connected to the local network. It uses radio signals from several base stations to mitigate the effect of shadow fading, a variation of signal strength over space created by the presence of buildings, foliage, and terrain variations. With a path loss exponent of four and a shadow fading standard deviation of 10 dB, four-branch macroscopic diversity results in a 13 dB improvement in signal strength and a 15 dB improvement in signal to cochannel interference ratio for high user capacity interference-limited operation. (Both figures are for 99 percent statistical coverge of the service area.) The improvement in signal to cochannel interference ratio is equivalent to a factor-of-five savings of spectrum.