A hybrid access method in a multiple access channel

This paper considers a multiple-access communication channel with an infinite number of users. We show that if a controlled slotted Aloha protocol is used, then messages with variable length will have a negative impact on the average message delay. In order to alleviate this problem, a mixed mode (Hybrid) access method is suggested under which the channel bandwidth is split into two sub-channels, managed under different policies. Messages whose length is less than or equal to a critical value are transmitted in one sub-channel under a slotted Aloha policy. The rest of the messages are sent through a separate portion of the channel bandwidth, using a reservation protocol. We show that under this hybrid access method the average delay of a message is greatly improved.