Two-stage frequency-domain oversampling receivers for cyclic prefix orthogonal frequency-division multiplexing systems

Orthogonal frequency-division multiplexing (OFDM) is a widely adopted technique in most wireless applications. It has been shown that zero padded OFDM (ZP-OFDM) with frequency-domain oversampling (FDO) can exhibit better performance than cyclic prefix OFDM (CP-OFDM) if the whole OFDM symbol is oversampled in the frequency domain. In this study, the authors propose a novel FDO-based scheme for CP-OFDM, which consists of two stages. First, the conventional CP-OFDM receiver is adopted to estimate the transmitted data and channel information. Second, the received symbol is reconstructed to reduce inter-symbol interference and oversampled in the frequency domain. The proposed scheme combines FDO and symbol reconstruction together, which enables the minimum mean square error (MMSE) and zero forcing (ZF) equalisers to exploit the channel information in high-dimensional non-orthogonal subcarrier domain and thus significantly suppress the interference on multipath channels. Simulation results show that the proposed FDO-MMSE CP-OFDM receiver can achieve much better bit error rate performance than the traditional CP-OFDM receiver and is comparable to the ZP-OFDM receiver with FDO.