A Study on OFDM Adaptive Array by the Multiple Control with Pre-and Post-FFT

Abstract

In OFDM transmission systems, the delayed waves beyond the guard interval and the co-channel interference waves cause Inter-Symbol Interference (ISI) and Co-channel Interference (CCI) respectively. These waves degrade the transmission performance. The Post-FFT array can constrain the interference wave in the guard interval, and multipath waves with the high correlation between the antenna. However, when it is going to obtain a diversity profit by extending an element interval, the delayed waves beyond the guard interval and interference waves receives with different symbol timing become low correlation waves. As a result, the system requires increasing the number of elements . In this paper, the proposed system divides an element of the Post-FFT array with a large element interval into the subarray which consists of two or more elements with a still narrower element interval. The proposed system can obtain the diversity gain using the compound control, and can remove a long delayed waves and an asynchronous interference waves. In order to clarify the validity of the proposal system, the basic characteristic was analyzed by the computer simulation.