AbstractOrthogonal frequency division multiple access (OFDMA) is considered as one of the technologies for 4th generation (4G) due to its robustness against multi‐path environment. OFDMA also has the advantage of flexibility in resource allocation, which cannot be supported by existing duplex schemes. In this paper, we propose dynamic hybrid duplex (DHD) which will enhance the efficiency and flexibility of the OFDMA system. To establish the framework of resource allocation for the DHD, we formulate DHD resource allocation problem (DRAP) which maximizes the total users' data rate with power, rate, and subcarrier allocation constraints. A heuristic procedure is developed to solve the problem. The procedure finds the best mode and the best amount of resources allocated to downlink (DL) and uplink (UL). Simulation is performed with five scenarios to evaluate the DHD. Its results show that the proposed DHD outperforms other duplex schemes in various environments. Copyright © 2010 John Wiley & Sons, Ltd.