Conventional concurrency control protocols are inapplicable in mobile broadcast environments due to a number of constraints of wireless communications. Previous studies are focused on efficient processing of read-only transactions at the mobile clients, neglecting update transactions. In this paper, we design a new protocol for processing both read-only and update mobile transactions. The protocol can detect data conflicts at an early stage at the mobile clients and resolve data conflicts flexibly using dynamic adjustment of timestamp ordering. Early data conflict detection saves processing and communication resources, while dynamic adjustment of timestamp ordering allows more schedules of transaction executions such that unnecessary transaction aborts can be avoided. We performed extensive simulation studies to evaluate the effectiveness of these two features for the performance of the new protocol. The analysis of simulation results showed that both features are effective and contribute differently to the satisfactory performance of the protocol.