Effect of CDMA transmission on performance of wireless networks with stack algorithm for collision resolution

This paper evaluates the performance of a packet radio network employing code division multiple access and a stack algorithm to resolve message collisions. We investigate the effects of bandspreading assuming a fixed total system bandwidth. Although bandspreading with perfectly orthogonal signals enhances system capacity, it does not resolve the instability of ALOHA random access unless special measures are taken to control retransmission traffic. Using a stack algorithm, at small traffic loads the packet delay is minimized if no spreading is applied. At large traffic loads, perfect CDMA enhances performance, but for imperfect signal separation at the receiver, advantages of CDMA are lost. The capacity of the stack algorithm addressed here can be enhanced from 0.32 to at least 0.40 if a large spreading factor with perfect signal separation is employed