Methods for Obtaining CIR Based on IFFT in MIMO-OFDMA Mobile Communication Systems

This paper mainly focus on methods for obtaining the CIR by performing the IFFT of CFR, which are heuristic or direct to improve channel estimation and tracking in MIMO- OFDMA systems. When FUSC mode is used, pilot signal are uniformaly inserted into the carrier sets during preamble and the FFT size over pilots spacing is an integer in mobile WiMAX. Therefore, it is possible to obtain CPR based on IFFT of CFR In this paper, we propose two methods involved in IFFT to get CIR, and the size of FFT used by method-1 is smaller than that done by method-2 however, method-1 has to consider the problem about the offset of pilot carriers.