Adaptive step control of LMS-based Interference Cancellation for WMAN ICS radio repeater

The use of repeater for the support of high data rate data transmission and the extension of cell coverage is imperative for the Wibro system, which is based on the IEEE 802.16e standardization. Generally, if the separation between transmitting and receiving antennas is not sufficient, the oscillation of repeater and the interference due to the feedback signals from original transmitted signal may be occurred. Hence, the Interference Cancellation System (ICS) should be implemented as the important part of the repeater system for the mobile cellular systems in order to eliminate an unwanted signals from the corrupted signals in the receiver. In this paper, we propose an adaptive techniques for the LMS-based interference cancellation methods by changing the step size according to the variation of channel environment in order to improve the performance degradation which is occurred by using the fixed step size approach. Simulation results show that the proposed scheme attains a little lower BER performance and much faster convergence speed compared to the conventional LMS-based interference cancellation techniques. The proposed scheme can be applied to other OFDM-based cellular systems and also be expected to achieve a similar performance improvement to IMT-advanced system, which is called as the next generation mobile communication standards.