On the Capacity of Slotted ALOHA Networks and Some Design Problems

Packet switching over broadcast channels with random access schemes is of current interest for local distribution system and for satellite channels. This mode of operation is useful when the communicating devices are mobile and when the ratio of the peak to average data rate requirement of each device is high. Such systems have been analyzed for the case in which all communicating devices are within an effective transmission range of each other; either directly or through the satellite. In this paper, we address broadcast networks in which originating devices cannot directly reach the destination receiver. Thus, devices are introduced which receive these packets and repeat them to the destination. The capacity (maximum throughput) of such systems is determined, and design problems related to the number of repeating devices and the usefulness of directional antennas are resolved.