Improving data transmission reliability and throughput in wireless sensor networks.

Improving data transmission throughput is a challenging task in wireless sensor networks. The lossy nature of wireless communication and rapidly changing environment had caused tremendous problems in transmitting data packets between sensor nodes. Our key objective here is to maximize the overall transmission throughput. Before investigating various approaches to accomplish our goal, we start with an extensive study of how radio signals behave in complex environments where obstructions and reflections occur. To achieve the same goal, we then design and implement a MAC layer overlay which consists of channel access scheduling and lost packet retransmission. The channel access scheduling mechanism is designed based on a hierarchical tree structure where each intermediate node collects data from multiple sources and forwards them to its parent at higher level. The lost packet recovery can retransmit lost packets without reliance on any acknowledgments. We evaluate our protocol on both Mica2 and Tmote sensor testbed, which shows that the data transmission throughput can be significantly improved.