PERFORMANCE EVALUATION OF A RELIABLE MULTICAST PROTOCOL IN MULTI-ACCESS WIRELESS LANs

Abstract

In the wireless networks scarce bandwidth and mobility require that multicasting protocols be robust, simple, and energy conserving. A major challenge lies in adapting multicast communication to environment where mobility is unlimited and failures are frequent. Wireless LANs are multi-access channels which are basically extension to the fixed network LANs and provide mobility to the users in the limited range. The unicast mechanism works fine with the IEEE 802.11 specifications but in multicasting, the acknowledgement explosion problem occurs as it's the common channel. In such a system, common channel imposes mutually, exclusive transmission of data. Here First issue is the problem of the sender acquiring the multi-access channel for multicast transmission. Second, is reliable multicast. For implementing in wireless LAN, the ARQ-based approaches are examined. New approach involves the election of one of the multicast group members (receivers) as a "leader" or representative for the purpose of sending feedback to the sender. For reliable multicast; on erroneous reception of a packet, the leader does not send an acknowledgment, prompting a retransmission. On erroneous reception of the packet at receivers other than the leader, the negative acknowledgments from these receivers to collide with the acknowledgment from the leader, thus destroying the acknowledgment and prompting the sender to retransmit the packet. In this dissertation the performance of a Reliable Multicasting Protocol for Wireless LANs is evaluated. I have implemented a discrete event simulator in C++ taking exhaustive lossy conditions into consideration. All the control message losses are also taken into consideration. The simulation results are validated with the data given by Reliable Multicast Protocol by Kim. The results are showing better average access period than the Random Leader Based Protocol. Based on the insight from the simulation results, we can predict that RMP works better even in case of higher probability of loss of messages in the channel.