Regarding the duplex modes used in the deployed WiMAX
networks, backbone network features long transmission
distance and large bandwidth. Therefore, FDD (Frequency
Division Duplex), which can mitigate delay problem and use
double RF resources for sending and receiving respectively to
acquire higher transmission capacity [3][4], is more desirable
than TDD (Time Division Duplex), which uses the same RF
band to send and receive data. Though data transmission by
wider unlicensed band is more likely to be interfered,
fortunately most of base stations in backbone network are
located in suburb or mountainous areas where few
applications of unlicensed bands will be launched. Thus, the
RF interference for backbone network will be minimized.