Cluster-based semi-asynchronous power-saving protocols for multi-hop ad hoc networks

Existing power-saving (PS) protocols for mobile ad hoc networks (MANETs) can be categorized into synchronous and asynchronous ones. The synchronous PS protocol cannot be applied to a multi-hop MANET, because it can cause three problems: clock synchronization; neighbor discovery; network partitioning. Although asynchronous solutions are attractive, the cost is high compared to synchronous protocols. Hosts in asynchronous protocols need to keep awake for a longer time, so as to discover asynchronous PS neighbors. Besides, a broadcast message has to be sent multiple times if a sending host´s neighbors wake up asynchronously. To conquer the deficiency of asynchronous PS protocols, we propose several cluster-based semi-asynchronous PS protocols for multi-hop MANETs. The basic idea is to cluster neighboring hosts such that synchronous PS protocols can be adopted within individual clusters, conserving a lot of energy. Two asynchronous schemes are provided in the inter-cluster level, including SNR-probability-based and location-based schemes. Simulation results show that the proposed semi-asynchronous approaches outperform the asynchronous PS protocols when applied to a multi-hop MANET.