As mobile wireless networks increase in popularity and pervasiveness, using internet ubiquitously is not a dream. The integration of Worldwide Interoperability for Microwave Access (WiMAX) and Wireless fidelity (WiFi) technologies seems to be a feasible option for better and cheaper wireless coverage extension. WiFi is already widely deployed in highly developed cities. Its weakness is short coverage, and no guarantee of quality of service (QoS). WiMAX multi-hop relay networks that employ relay stations are expected to extend coverage and reduce the cost of deployment in the near future. This hybrid network can take advantage of the benefits of both technologies to provide ubiquitous services with high QoS. In order to improve the bandwidth utilization and reduce the interference in heterogeneous wireless networks, this work applies genetic algorithm-based resource management techniques to manage the precious bandwidth resource in the heterogeneous wireless networks with minimal human intervention. The simulation results show that our scheme is effective in terms of performance metrics, including dropping probability of handoff calls, new call blocking probability, and bandwidth utilization.