Multiple-capture performance of DS-SS packet radio systems with common spreading code

Abstract

The author presents a multiple-capture model for the centralised spread-spectrum (SS) packet radio systems in which each user is assigned common direct-sequence (DS) spreading code for packet transmission. Basic equations for the multiple-capture probability and throughput performance are derived at the central receiver. At the link-level, two key design parameters in common spreading code systems are evaluated, namely, the expected number of packets captured at the receiver and the allowable number of simultaneous transmissions that are supportable at a specified data bit-error rate and probability of packet capture. Using the block oriented systems simulator (BOSS), simulations were carried out for the central receivers with coherent, differential, and envelope header detection, and results from the simulations are compared with theoretical evaluations of the multiple-capture probability. It is shown, for a threshold approximation to the probability of data packet success, that the multiple-capture model significantly improves system throughput.