A multiple access technique for cellular packet networks with admission control

We propose a code division multiple access technique for cellular packet data networks. In this technique, each user is assigned a distinct quasi-orthogonal pseudonoise (PN) sequence code for accessing the spread spectrum channel. Packet transmission is admitted to the network with explicit acknowledgement from the base station. To prevent the bistable behavior of ALOHA-type systems, the base station controls access attempts by broadcasting a busy tone when there are too many simultaneously arriving packets. We analyze the throughput, blocking probability, and average delay of the proposed system and evaluate system performance using ATM format packets. The results show the proposed approach leads to a good performance. With 33 percent of error control bits and open-loop power control, a 40 percent improvement in effective throughput over TDMA systems is possible even in the presence of Rayleigh fading.