Frequency-domain PTEQ for MIMO OFDM-CDMA in doubly selective channels

The multi-input multi-output technique offers significant increases in data throughput and link range without additional bandwidth or transmit power. We propose frequency-domain per-tone equalizers for MIMO OFDM-CDMA over doubly selective channels. We consider the most general case, where the cyclic prefix (CP) is smaller than channel delay spread than, which leads to inter-block interference (IBI). IBI in concurrent with the Doppler Effect spoils the orthogonality between subcarriers and, hence, leads to severe inter-carrier interference (ICI). Owing to the fact, the time varying finite impulse response (TV-FIR) channel shortening filter optimizes the performance over all subcarriers in a joint mode; it doesn´t have a satisfied performance. An ideal frequency-domain per-tone equalizer (PTEQ) is then obtained by changing the TV-FIR operation to the frequency domain.