Precoded Spectrally Efficient FDM system

Abstract

Spectrally Efficient Frequency Division Multiplexing (SEFDM) system proposes enhanced spectrum utilization in contrast to Orthogonal Frequency Division Multiplexing system (OFDM). Spectral efficiency is increased by relaxing the orthogonality condition while maintaining the same transmission rate per individual channel, hence, for the same bandwidth allocation SEFDM offers higher throughput than OFDM. However, the loss of orthogonality necessitates complex algorithms for the recovery of the signal. In this work, we propose a precoding strategy that greatly simplifies the detection of the signal. The strategy facilitates simpler detection for the same bandwidth savings as an equivalent uncoded SEFDM system. The strategy is based on localizing the effects of the lost orthogonality in a portion of the transmitted symbols. Detection of the preserved channels is a simple zero forcing (ZF) estimator and the rest of the symbols can be detected using complex detectors such as the maximum likelihood (ML) detector. Simple architecture of the precoded SEFDM system based on IDFT/DFT blocks for transmission and reception is proposed. Extensive numerical investigations in AWGN channel confirmed favorable bit error rate (BER) performance of the new system with a much reduced complexity.