Subblock Processing for Frequency-Domain Turbo Equalization Under Fast Fading Environments

Frequency-domain equalization (FDE) has been studied for suppressing inter-symbol interference (ISI) due to frequency selective fading in single carrier systems. When a high- mobility terminal is assumed in the system, channel transition within an FFT block cannot be ignored. Then, the ISI reduction performance of FDE degrades since cyclicity of the channel matrix is lost. To solve this problem, a method of dividing the received data block into multiple subblocks has been proposed. In the paper, the subblock processing is applied to frequency-domain turbo equalization (FDTE). The results of numerical analysis show a remarkable improvement by the proposed method. Specifically, the FDTE with two-subblock processing can decrease the block error rate floor to less than 0.001 when the maximum Doppler frequency normalized by the block length is 0.4.