| This thesis investigates the performance of turbo equalizers based on interference canceller (IC) that has been implemented in the frequency domain (FD-IC), as opposed to the more typical time domain implementation (TD-IC). A computational complexity analysis shows that the FD-IC has much lower complexity when equalizing channels with long delay spreads, while still maintaining the excellent performance of the TD-IC. A novel, sub-optimal, reduced-complexity hybrid frequency/time domain interference canceller (hybrid IC), which is based on implementing part of the IC in the frequency domain (the P-filter), and part in the time domain (the q-filter), is proposed. The filter coefficients of the hybrid IC are derived according to the minimum mean squared error criterion. It is shown by means of computer simulation that turbo equalization using the hybrid IC can achieve respectable performance in terms of the bit and frame error rates, without the need for performing FFT's at each iteration, thereby providing reduced computational complexity. Although the hybrid IC is sub-optimal as compared to the FD-IC, in some cases it is shown that it can even provide slightly better performance than the FD-IC. |
