(A) new medium access control protocol for multicast service in mobile Ad Hoc networks

Abstract

The previous approach to the multicast problem for ad hoc networks is to resolve at networks layer. As a result, there are many multicast routing protocols based on multicast delivery structure in mobile ad hoc networks. In mobile ad hoc networks, one important issue is how to increase channel utilization while accounting for hidden-terminals. In case of unicast traffic, IEEE 802.11 MAC uses a collision avoidance scheme with RTS/CTS/ACK to resolve hidden terminal problem. In case of broadcast packets in IEEE 802.11, the sending node executes collision avoidance and then transmits broadcast data. But there are no specific solutions for reliable multicast data transmission in mobile ad hoc networks. For multicast traffic in ad hoc networks, we must consider hidden terminals, channel noise, frame length and mutual coexistence with traditional ad hoc unicast MAC scheme (RTS/CTS/ACK). In this thesis, we propose two kinds of new medium access control schemes combining RTS/CTS/ACK with scheduling property to avoid collision by including the additional information in the RTS message for multicast service. One is a scheme minimizing unicast traffic throughput degradation by the multicast traffic and the other is a scheme maximizing multicast traffic throughput. We demonstrate the advantage of our new medium access control protocols based on multicast in ad hoc networks through analysis and simulations. Proposed schemes, together with the extra benefits such as power saving and the achievement of higher channel utilization than CSMA or multiple unicast, show the ways to support multicast service in mobile ad hoc networks coexisting with previous unicast and broadcast medium access control scheme.