Trial-Number Reset Mechanism at MAC Layer for Mobile Ad Hoc Networks

MANET(Mobile Ad Hoc Networks) routing protocols definitely need a route maintenance process due to frequent route breakage caused by node mobility, which takes advantage of the MAC layer’s handshaking service (RTS-CTS-DATA-ACK exchanged packet transmission is considered in this paper). Reaching the limited number of trial of packet transmission, namely retry-limit, before a reception of a corresponding ACK packet indicating a successful data transmission, is used to notify the routing protocol of a link breakage, that is, a route dis-connection. The packet, therefore, is discarded and the source is accordingly requested to perform a route recovery with producing many flooded route discovery packets. However, since a reception of a CTS packet during the MAC layer’s handshaking means an availability of route, the current number of trial used to detect a link breakage should not increase, but it should be reset to 0, instead. Furthermore, the absence of an ACK packet during a given ACK timeout after a successful reception of CTS packet should not increase the current number of trial for the same purpose. We show the performance improvement with this trial-number reset mechanism by using GloMoSim simulator with AODV routing protocol.