S-MAC is a MAC (Medium Access Control) protocol as specialized for the wireless sensor network in order to sacrifice transmission delay and extend the working life of the whole sensor nodes. S-MAC, which was made by modifying IEEE 802.11, reduced the energy wasted in the wireless sensor network by using a periodic listen and sleep scheduling method. The first task that the wireless sensor network using S-MAC performs is to find a neighbor node, and then choose and broadcast its own schedule. In this process, as a result of using a time selected randomly and scheduling, diversified schedules are generated. In the end, schedule clusters, which are different from one another, get to be made, and nodes on these cluster borders fail to communicate with one another due to an inconsistent listen time. In the existing paper on S-MAC, this problem is solved by placing a border node to adopt schedules which are different from one another. However, compared with other nodes, the border node consumes energy more, and its efficiency of data transmission according to the broadcast type is lower. This paper suggested a method for unifying schedules through the H-SYNC (Heartbeat-SYNC) method for solving such problem of the diversified scheduling of S-MAC, and as a result of comparing and evaluating its performance through simulation, it was found that the border node consumed energy less.