Spread spectrum slotted ALOHA packet radio networks with near- perfect multi-packet capture

Abstract

This dissertation considers spread spectrum slotted ALOHA packet radio networks employing direct sequence spread spectrum signaling, discrete time of arrival randomization, an optimum delay capture mechanism, and multiple central receivers. The primary objective of this research is to develop a stable, high-performance packet radio network that enables interactive packet communications among a large number of mobile radios by providing the receiver systems with sufficient multiple access and multi-packet capture capabilities. Advantages of spread spectrum slotted ALOHA packet radio systems with optimum delay capture and multi-packet reception capabilities are discussed. The emphasis of this research is on a delay capture-type channel shared by ground radio random access users. The conventional spread spectrum packet radio system with delay capture is first reviewed in depth with added interpretations. Exact capture probability expressions for new delay capture models are derived and incorporated into the subsequent performance analysis to investigate the dynamic behavior of the proposed packet radio network in a capture-type channel. For moderate values of the capture ratio, Q, and a moderate number of central receivers, the realization of a single-hop system with a near-perfect, multi-packet capture capability appears to be feasible. Consequently, the system capacity is significantly increased while maintaining stability. For the two-hop networks, spread spectrum slotted ALOHA packet radio using optimum delay capture makes possible substantial improvement in throughput and delay even with a large packet transmission rate from a repeater to the central station and with a large number of repeaters. With a large successful transmission rate of packets to a repeater, the two-hop throughput monotonically increases without degradation, giving a stabilizing effect on the system. The impact of the capture effect on the performance of single and two-hop packet radio networks is extensively exploited through several performance analysis techniques (Markov, equilibrium contour, and S-G analyses). This research has several implications. First, an optimum delay capture model has been developed and analyzed...