Abstract
The instant deployment without relying on an existing infrastructure makes ad hoc network model a striking choice for many dynamic situations. It is therefore an important member of the vast array of technologies supporting urban networks. Many existing MAC protocols follow synchronous model that assumes that nodes in a network have a common clock while in fact it is very difficult to synchronize clocks among nodes in a large multi-hop network. Other MAC protocols may use asynchronous or semi-asynchronous model that either consume high energy or incur long synchronization delay. This work aims to provide a MAC that supports both high energy efficiency and short synchronization delay. We propose multi-hop semi-asynchronous MAC (MS-MAC), which uses a cross-layer approach to combine the improved power saving mode (IPSM) MAC with a dominating set-based hierarchical routing scheme. The proposed MS-MAC not only synchronizes clocks of nodes within the same cluster; but also guarantees that neighboring nodes belonging to two clusters can initiate data communication within one beacon interval. While evaluating with two comparable protocols, MS-MAC has achieved the highest energy efficiency while maintaining comparable throughput and network lifetime performances.