Power Saving Routing in MANET a Modified Casting to Ensure Energy Efficiency

In a typical wireless mobile ad-hoc network (MANET) using a shared communication medium, every node receives or overhears every data transmission occurring in its vicinity. However, this technique is not applicable when a power saving mechanism (PSM) such as the one specified in IEEE 802.11 is employed, where a packet advertisement period is separated from the actual data transmission period. When a node receives an advertised packet that is not destined to it, it switches to a low-power state during the data transmission period, and thus, conserves power. However, since some MANET routing protocols such as Dynamic Source Routing (DSR) collect route information via overhearing, they would suffer if they are used with the IEEE 802.11PSM. Allowing no overhearing may critically deteriorate the performance of the underlying routing protocol, while unconditional overhearing may offset the advantage of using PSM. This paper proposes a new communication mechanism, called Modified Casting or M-cast, via which a sender can specify the desired level of overhearing in addition to the intended receiver by using(Ad-hoc Ondemand Distance Vector) AODV protocol. Therefore, it is possible that only a random set of nodes overhear and collect route information for future use. M-cast improves not only the energy efficiency, but also the energy balance among the nodes, without significantly affecting the routing efficiency.