Throughput of DS/SS unslotted ALOHA system with channel load sensing

Throughput analysis of direct-sequence spread spectrum multiple access (DS/SSMA) unslotted ALOHA with fixed packet length is presented. As the levels of multiuser interference fluctuate during the packet transmission, we calculate the packet error probability and the throughput by considering not only the number of overlapped packets but also the amount of time overlap. On the assumption that packet generation is Poisson, the system can be thought as the M/D/∞ queue. With a Gaussian approximation of multiuser interference, we obtain the throughput as a function of the number of chips in a bit, the packet length and the offered load of the system. We also analyze the channel load sensing protocol (CLSP), and obtain the optimum threshold of the CLSP. As a result, we indicate the relation of the β-channel model with the optimum threshold