Abstract: Duty-cycle MAC protocols widely used in wireless sensor networks lead to extra end-to-end delivery latency, while the existing solutions, such as RMAC (the Routing enhanced MAC protocol)， are only applicable to light-load traffic. A new MAC protocol called HMAC is proposed, which avoids the unnecessary energy consumption caused by loss events without sacrificing the performance of packet delivery latency. By using two scheduling frames, HMAC realizes efficient multihop packet delivery in a single cycle, and ensures that bad link conditions do not impact the downstream nodes. Compared with S-MAC and RMAC, it is shown that HMAC outperforms these protocols in a heavy-load traffic scenario, with higher energy efficiency and lower delivery latency.

Key words: wireless sensor networks, medium access control, heavy traffic, loss event