Energy Aware Routing(EAR)[1] was proposed by Shah and Rabaey. EAR is anenergy efficient routing for the wireless sensor networks. The primary goal ofEAR is to improve the survivability of the networks. For this, EAR occasionally

uses suboptimal paths rather than always using the optimal path. These paths are selected with the energy-based probabilities as explained above. This is intended to slow down the depletion of the energy of the nodes across networks.

As a consequence, the entire networks will have a longer lifetime than that using the algorithms such as Directed Diffusion[14]. EAR finds multiple routes, if any, from source to destination nodes. Each route is assigned a probability of being selected to transmit a packet, based on residual energy and the energy for communications at the nodes along the route.Then, based on these probabilities, one of the candidate routes is chosen in order to transmit a packet. The probability is proportional to the energy level at each node, so the route with high energy is more likely to be selected than the route with low energy level.

The operation of EAR consists of three phases. In Setup phase, a destination node initiates a route request and a routing table is built up by finding all the paths from a source to the destination and their energy cost. In Data

Communication phase, data packets are sent from the source to the destination. Each of the intermediate nodes forwards the packet to a neighboring node that is chosen randomly based on the probability computed in the setup phase.

In Route Maintenance phase, local flooding is performed to keep all the paths alive[1].