A minislot access protocol for CDMA packet radio networks with positive acknowledgement

The author presents and analyzes a minislotted channel-access protocol for code-division multiple-access (CDMA) packet radio networks that provides a number of distinct advantages. First, the protocol accomplishes active acknowledgement with very high reliability, while consuming only a small fraction of overhead channel bandwidth for the positive acknowledgement transmissions. Second, the minislot architecture reduces the vulnerability of the network to intelligent jammers, who may attempt to attack the acquisition preamble selectively. This is accomplished with only a modest reduction in overall network capacity. Finally, the minislot architecture provides a mechanism by which variable-length data packets may be accommodated without significant increase in design complexity, thereby improving the efficiency of the network. This protocol is analyzed by means of a discrete-time Markov chain model, and throughput performance is derived for a wide range of potential minislot sizes. A fundamental limit on the throughput of perfect CDMA networks is derived for both slotted and unslotted channels and is a consequence of the burstiness of traffic and the random pairing of transmitters and receivers