Extending the lifetime of multi hop ad hoc networks by managing the use of relay nodes

Multi hop ad hoc networks rely on the cooperation between nodes to relay information between a source and destination. Depending on their location, some nodes may be better placed than others to offer a relay function and this may lead to early exhaustion of the battery energy of these nodes. To address this problem, this paper investigates the use of a battery capacity threshold to protect overused nodes and maximise the lifetime of the network. The network lifetime is evaluated as a function of the threshold level using a 25 node network model. The results of the model show that if the threshold level is high, this leads to route blockage. Conversely if the threshold is too low then the more heavily used nodes will rapidly exhaust the battery capacity. The optimum threshold level is found to be approximately 30% of the maximum battery capacity, giving an improvement in the network lifetime of about 78%.