The most significant obstacle to multi-hop communications in wireless sensor networks is high link error rate. Thus, an efficient hop-by-hop reliability support scheme is highly required. In this paper, we identify the characteristics of two typical communication patterns in wireless sensor networks and address the problems of previous end-to-end sequence based hop-byhop error recovery protocols, which cannot work properly with route change events and have a scalability problem with multiple

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... ders. We propose a new hopby-hop reliability support scheme named HRS. It uses hop-by-hop sequence numbers for hop-by-hop error recovery and operates in two separate modes depending on communication patterns. Through ns-2 based simulations, we show that both modes of HRS outperform the existing protocols in most metrics.