Interference Suppression Capability Of Faster Than Symbol Rate Sampling And Frequency Domain Oversampling
The performance of faster than symbol rate (FTSR) sampled minimum mean square error (MMSE) equalizers, which is generally considered as a remedy to time or phase errors, is explicitly analyzed accounting for practical channel conditions and pulse shaping filter. The concept of FTSR sampling is applied to the cyclic prefix (CP) based MMSE equalization. The performance of this equalizer is evaluated in regard to mutual information and error rate. It is semi-analytically proven that FTSR sampling provides an increase in mutual information. This motivates the fact that there is a potential gain that can be exploited by FTSR sampling for CP based MMSE equalization. The complexity increase due to FTSR sampling is compensated by a low complexity CP based MMSE equalizer implementation. FTSR sampling is studied to exploit additional degrees of freedom (DoF) of excess bandwidth for the sake of interference suppression in multiuser communication. Spatial domain interpretation is employed to assess the effectiveness of FTSR sampling such that multiple receptions are considered as virtual antennas. The capacity analysis reveals that FTSR technique achieves extra (DoF) proportional to any excess bandwidth being used provided that multipath channel taps are not equally spaced, which is a physical reality. The impact is further quantified by a FTSR sampled MMSE detector and a practical iterative receiver based on FTSR sampling. A counterpart of FTSR sampling in time domain is the frequency domain oversampling (FDO), which is investigated to improve the error performance of MMSE SC-FDE for multipath channels. The impact of FDO is analyzed in regard to the outage probability.
Prof. Dr. Ali Özgür Yılmaz