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Energy efficiency is a requirement when designing a MAC protocol for wireless sensor networks. To reduce needless energy use, most MAC protocols exploit the duty cycling technique, in which the radio frequently turns on and off in each operational cycle. Among those protocols, the multi-hop MAC protocol routing enhanced MAC (RMAC) enables multi-hop transmission to minimize the latency burden, which is the main disadvantage of duty cycling. In each cycle, when nodes are awake, RMAC can exploit the cross-layer information to initialize the multi-hop flow and the data packet transmission is scheduled in the subsequent sleep period. This technique, however, introduces the long listening period problem in which nodes have to keep the radio on even when no flow data is scheduled. We propose a solution to solve that problem by adding a short period after the synchronized process. In this period, we use carrier sensing as a binary signal, which lets the nodes know the traffic status of the network. After the period, nodes go to the sleep state when no data exists in the network; otherwise nodes operate similarly to the RMAC's basic scheme. Simulations showed that our solution can improve energy efficiency while only slightly increasing latency.