Study of congestion control using AODV and signal strength by avoiding link failure in MANET

Routing in MANET is challenging due to its mobility feature. The main reasons of link failures are mobility, interference and congestion. Mobility means each node is free to move within its transmission range. Interference occurs due to collision and hidden node. Hidden node means two nodes out of each other´s radio range, simultaneously try to transmit data to an intermediate node, which is in radio range of both the sending nodes. None of the sending nodes will be aware of the other node´s transmission, causing a collision to occur at the intermediate node. Hidden node interference problem can be solved by using the RTS-CTS handshake method of 802.11 MAC. Signal strength is considered as cross layer interaction parameter. Received signal strength is taken from physical layer and is checked at MAC layer whether it is above certain threshold. If it is above threshold then link is strong, otherwise weak link, which can cause route failure. When a route is likely to fail due to weak signal strength of a node, it will find alternate path. AODV has better congestion avoidance mechanisms. This paper addresses four signal strength based congestion control mechanisms AODV, Reliable AODV, MAODV, CLS_AODV.