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WiMAX-WLAN gateway (WWG) in heterogeneous WiMAX networks were configured to aggregate and route traffic from WiMAX and WLAN mobile stations (MSs) that is out of coverage with base station (BS) and access point, respectively. However, previous studies on bandwidth request (BR) mechanism at WWG are carried out using either polling or bandwidth reservation for best effort (BE) services. These studies suffer from low spectral efficiency with WiMAX network and cause unfairness to WiMAX MSs while contention based BR is carried out from WiMAX MS to BS (via WWG). To overcome these limitations, we suggest three variants of contention based bandwidth request namely message based BR, CDMA or code based BR and heterogeneous BR. Simulations validate the proposed mechanisms in terms of throughput, connection delay and queuing delay. It is inferred that with heterogeneous BR, the network throughput is improved by 11.21%, the connection delay at WWG is reduced by 5.85%, the queuing delay at WWG is reduced by 9.47%, the MAC delay at WLAN MS is reduced by 9.09% and the average access delay at WiMAX MS is reduced by 62.12% compared to message and CDMA based BR.