Unslotted ALOHA in high speed bidirectional bus networks

The authors study the performance of the unslotted ALOHA multiple access protocol in a high speed bidirectional bus network. For point-to-point communications, its maximum throughput is known to be independent of the ratio of end-to-end propagation delay to packet transmission time. For broadcast communications, it is shown that, if the offered load density is uniform along the bus, the maximum throughput achievable by a station depends on its location along the bus. To achieve a uniform throughput density, the offered load density has to vary along the bus. The optimal profile for the offered load density is derived. In any case, the maximum throughput degrades with the ratio of end-to-end propagation delay to packet transmission time