Spatial distribution and range trade-offs for frequency-hopped spread spectrum networks using the ratio-threshold test

The authors study spatially distributed packet radio networks that employ frequency-hopping spread spectrum signaling where propagation loss is taken into account. They analyze a slotted ALOHA channel-access protocol, with Reed-Solomon error-control coding. Viterbi´s ratio-threshold technique is used to determine which symbols should be erased so that errors-and-erasures decoding can be used. Networks with terminals at random locations and at deterministic locations are considered. It is found that the performance of a generic link can be estimated based on purely geometric arguments, by studying a single statistic as a function of the link distance and the ratio threshold. The amount of computation required for the evaluation of this statistic is orders of magnitude less than that required to compute the actual codeword error probability. Results are presented on codeword error probability as a function of the threshold ratio and the link length, for three modeling assumptions on the receiver´s ability to distinguish a useful signal from noise