Spreading gain control in random access direct-sequence spread spectrum data networks

In this paper, we consider a time-slotted DS-SSMA network consisting of a single radio access point and a finite number of mobile wireless terminals. The terminals generate `bursty' packet data and transmit in a random access fashion over a common broadband channel to the access point using different spreading codes. As in narrowband ALOHA systems, the performance of random access spread spectrum networks can be severely hampered due to saturation effects caused by inherent bistable behavior. We study the affect of dynamic spreading gain control on the stability and throughput properties of the network. We provide an optimal algorithm and establish a necessary and sufficient condition under which the algorithm eliminates bistability. If the condition holds, then the resulting operating point is the best possible; otherwise, the two resulting stability points are, in some sense, the best possible. In either case, the algorithm achieves high throughput.