Group Allocation Multiple Access with Collision Detection

The Group Allocation Multiple Access with Collision Detection (GAMA/CD) protocol for scheduling variable-length packet transmissions in a local area network is speciied and analyzed. GAMA/CD provides the advantages of both TDMA and CSMA/CD by maintaining a dynamically-sized cycle that varies in length depending on the network load; each cycle is composed of a contention period and a group-transmission period. During the contention period, a station with one or more packets to send competes for membership in the transmission group. Once a member of the transmission group, a station is able to send data without collision during each cycle; as long as a station has data to send, it maintains its position in the group. This can be viewed as either allowing stations to \share the oor" in an organized manner, or as establishing frames that are not synchronized on a slot-basis and vary their length dynamically based on demand. Both the throughput and the delay of GAMA/CD are presented and analyzed. To validate our analysis, the results of both models are compared to the throughput and delay produced by a simulation of GAMA/CD.