Power Efficient Hybrid Channel Access Scheduling in Wireless Multihop Networks

Hybrid Activation Multiple Access (HAMA) is a synchronous medium access protocol that maximizes the chance of link activations using code-division schemes. However, in HAMA there are two situations when a node´s radio could rest (i.e., stay in sleep mode) without any other implications to the protocol itself. Nodes stay in idle when yielding (i.e., Yield state) to potential hidden terminals, or when there is no packet to be transmitted when they have a chance to do so. By switching the node´s radio to a sleep state whenever possible, one can expect to not only save energy but also take advantage of the battery capacity recovery effect (due to the battery relaxation phenomena). However, when performing performance evaluation through simulations, one must adopt a more realistic battery model to account for the battery capacity recovery effect. In this work, we propose a new variant of HAMA, named Power Efficient Hybrid Activation Multiple Access (PHAMA), which takes advantage of wasted time slots for power saving and battery capacity recovery. To get an accurate estimate of the battery capacity gains, we adopt the Rakhmatov-Vrudhula battery model. Extensive simulation results show that PHAMA provides simple ways to extend the network lifetime compared to the original HAMA protocol.