In recent years, mobile communications have experienced rapid development. There is an escalating number of research papers dealing with data dissemination, indexing and caching in mobile database systems. To the contrary, concurrency control in mobile environments has received relatively less attention. Researchers either assume that clients only execute read-only transactions or simply adopt the traditional client-server model. In this paper, we propose a timestamp-based concurrency control algorithm for broadcasting systems, which dynamically adjusts the serialization order among transactions to allow more transactions to complete without restarts. Our simulation results show that our algorithm performs significantly better than the previous strategies.