Altruistic Cooperation for Energy-Efficient Multi-Channel MAC Protocols

Recently, a new notion of cooperation was proposed to solve multi-channel coordination problems. When a transmit-receive pair wishes to initiate communication, neighboring nodes share their knowledge of channel usage. This helps to substantially reduce collisions and increases throughput significantly. However, it comes at the cost of increased energy consumption since idle nodes have to stay awake to overhear and acquire channel usage information. In fact this can be as high as 264% of a power-saving protocol without cooperation. In this paper, we propose a strategy called altruistic cooperation for cooperative multi-channel MAC protocols to conserve energy. The core idea is to introduce specialized nodes called altruists in the network whose only role is to acquire and share channel usage information. All other nodes, termed peers, go in to the sleep mode when idle. This strategy seems naive because it needs additional nodes to be deployed. In fact, it is unclear whether a desirable throughput-energy trade-off can be achieved and whether the cost of additional nodes can offset the performance gain. We perform a close study on this strategy in terms of three aspects: network deployment, cost efficiency, and system performance. Our study indicates that only a few additional nodes need to be deployed and cost efficiency is more than doubled in terms of a new metric called bit-price ratio that we propose. By using the strategy, a cooperative protocol is found to save up to 70% energy while not compromising throughput.