Application techniques of interference canceller to high frequency band wireless system utilizing multi-ary modulation

摘要

Wireless link systems have been investigated as the base station network in the future mobile communication system. They would utilize high frequency band and multi-ary modulation scheme due to system requirements of high capacity. An interference canceller (IC) is one of effective methods to enhance the system frequency utilization efficiency. In such system, however, performances of the IC are severely degraded by the frequency offset between the desired and the interference signals since the frequency offset is extremely large in the high frequency band. Moreover, the signal constellation ambiguity occurs frequently and it impairs IC performances severely when multi-ary modulations are utilized. This paper proposes two methods to address aforementioned problems. One method estimates and compensates the frequency offset by adjusting the frequency of the desired signal to that of the interference signal. The other method controls the transmission power or the phase of the desired signal in order to avoid the signal constellation ambiguity. Simulation results show that the proposed methods effectively suppress the frequency offset and the signal constellation ambiguity and that the IC effectively performs by the proposed methods even in utilizing the high frequency signal and multi-ary modulation.