PRIORITIZED CONFLICT-RESOLUTION ON MULTIPLE-ACCESS BROADCAST NETWORKS- ALGORITHMS AND PERFORMANCE

In a multiple access broadcast network all network nodes share a singl e shared communication channel, and there is the possibility of a coll ision when two or more nodes transmit at overlapping times. A prioriti zed conflict resolution algorithm is one in which, when a collision oc curs, all colliding messages are retransmitted according to their prio rity. We first propose PCR-CMS, A prioritized conflict resolution algo rithm using control minislots. The protocol requires each station to t ransmit its message in the data slot, and place a pulse in one of the control minislots to indicate the priority associated with tire messag e. By using some small additional overhead for control minislots, PCR- CMS is able to successfully transmit each message with a linear delay with respect to the number of messages transmitted during its waiting time, as shown from simulation result. We next study and compare the p erformance of two existing algorithms, PCR (Prioritized Conflict Resol ution) and DPCR Dynamic Prioritized Conflict Resolution), which no not assume control minislots on the channel. Experimental results show th at DPCR performs better than PCR both in terms of saturating throughpu t and average delay. The advantage of DPCR is even more significant at high offered load in which it is able to transmit high priority messa ges quickly while keeping the average delay of all messages lower than that of PCR. Prioritized conflict resolution algorithms studied here can be useful for multimedia communications in LANs or wireless networ ks. When various sources of traffic share the same channel, by assigni ng high priority to real-time traffic, both DPCR and PCR-CMS ensure th at real-time messages are transmitted quickly with very little conflic ting delay.