The performance of Medium access control (MAC) protocol has an immediate and fundamental impact on the overall effciency of the ad hoc network. Thus, the transmission scheduling policy employedby schedule-based MAC protocol is a key design problem in ad hoc networks. However, many of the existingtopology-transparent schedule-based MAC protocols employ transmission scheduling policies are not well-suited tocope with the dynamically changing network conditions.Following the TSMA (Time spread multiple access) protocol, we propose an Optimal time spread multiple access(OTSMA) scheduling policy that is based on an optimalparameter setting mechanism and a hybrid channel access strategy. According to the current network topologyand traffc load, our proposed OTSMA scheduling policycan control each node to utilize its assigned slots and itsnon-assigned slots effectively. Simulation results show thatour proposed OTSMA scheduling policy gives better performance than the existing topology-transparent schedulebased policies.