Bandwidth-efficient wireless OFDM

Abstract

Due to ever-increasing bandwidth demands in future wireless service, the radio frequency band becomes more and more invaluable. In this paper, we address channel equalization for bandwidth-efficient wireless orthogonal frequency-division multiplexing (OFDM). First, we show that in order to be free of both interchannel interference and interblock interference, wireless OFDM has to occupy a bandwidth wider than the Nyquist rate and use insufficient statistics in symbol demodulation. Thus, the conventional OFDM gains computational efficiency using the discrete Fourier transform (DFT) in demodulation at the cost of low efficiency of bandwidth usage and degradation in symbol error performance. Then we consider the OFDM that achieves high efficiency of bandwidth usage, allows interchannel interference and interblock interference to exist, and uses sufficient statistics in symbol demodulation. A one-tap decision feedback equalizer (DFE) is proposed for equalization of the bandwidth efficient OFDM system. Simulation and numerical evaluation for an indoor wireless asynchronous transfer mode network are carried out. It is demonstrated that though occupying a narrower bandwidth, the one-tap DFE-based bandwidth-efficient OFDM system achieves lower symbol error rate and higher mutual information than the conventional DFT-based OFDM system. The proposed OFDM system presents a monotonically increasing symbol error rate, and convex-down achieved mutual information with respect to increasing efficiency of bandwidth usage.