Interference cancellation methods for SC-FDE systems with insufficient cyclic prefix

Abstract

The critical problem for high speed data transmission is the time dispersive channel which causes the interference among consecutive transmitted symbols, known as inter-symbols interference (ISI). A well-known approach to mitigate ISI is the channel equalization that can compensate the channel distortion. In single carrier (SC) digital communication systems, various time domain equalizers (TDEs) have been generally used for the ISI mitigation. However, the computational complexity per symbol rises linearly with the length of ISI. Their implementation for the broadband systems is limited. Another solution is the frequency domain equalization. Frequency domain equalizers (FDEs) do not require the computational complexity in proportion to the ISI span, but the bandwidth efficiency decreases since redundant symbols, called the guard interval, are appended to transmitted signals. To achieve the low complexity and the high bandwidth efficiency simultaneously, FDEs with insufficient GI can be adopted. When insufficient GI is appended, several interferences degrade the performance. Thus, we propose iterative receiver structures for SC-FDE systems with insufficient GI to reduce the effects of the interferences. The first method is based on the iterative CP reconstruction method. Previous CP reconstruction methods make all missing parts with the estimated symbols at every iteration, but they cause the ambiguity when the equalization coefficients are updated and improve the performance little. However in the proposed method, reliable soft symbols are chosen, and then the parts of insufficient CP are made using them. This approach removes the ambiguity to calculate updated coefficients and outperforms the previous the CP reconstruction methods. Another proposed approach is to compensate the insufficient GI part with following blocks. Since the head symbols of blocks have the symbols for previous blocks that can be used for all GI parts. The insuefficient GI parts are...