If a WiMAX base station cannot receive a ranging signal from a WiMAX-embedded wireless terminal or if adjustment is not completed even after the WiMAX-embedded wireless terminal adjusts a parameter depending on adjusted value information for a pre-determined number of times, negotiation is performed via a heterogeneous network to establish a communication connection for upstream communication from the WiMAX-embedded wireless terminal to the WiMAX base station, and only downstream communication from the WiMAX base station to the WiMAX-embedded wireless terminal is performed via a WiMAX network.