Frequency-domain equalization for OFDMA-based multiuser MIMO systems with improper modulation schemes

Pei Xiao,Colin Cowan,Branka Vucetic,Yi Wu,Anthony Fagan,Zihuai Lin

doi:10.1186/1687-6180-2011-73

Abstract

In this paper, we propose a novel transceiver structure for orthogonal frequency division multiple access-based uplink multiuser multiple-input multiple-output systems. The numerical results show that the proposed frequency-domain equalization schemes significantly outperform conventional linear minimum mean square error-based equalizers in terms of bit error rate performance with moderate increase in computational complexity.

Highlights

Multiple-input multiple-output (MIMO) techniques in combination with orthogonal frequency division multiple access (OFDMA) have been commonly used by most of the 4G air-interfaces, e.g., WiMAX, long-term evolution, IEEE 802.20, Wireless broadband, etc
The pseudo-autocorrelation function is usually not considered and is implicitly assumed to be zero. While this is the optimal strategy when dealing with proper complex random processes [11], it turns out to be sub-optimal in situations where the transmitted signals and/or interference are improper complex random processes, for which the pseudo-autocorrelation function is non-vanishing, and the performance of a linear receiver can be improved by the use of widely linear processing (WLP) [12]
Our simulation results reveal that the proposed scheme has superior bit error rate (BER) performance compared to the ones with the conventional Frequency-domain equalization (FDE)

Summary

Introduction

Multiple-input multiple-output (MIMO) techniques in combination with orthogonal frequency division multiple access (OFDMA) have been commonly used by most of the 4G air-interfaces, e.g., WiMAX, long-term evolution, IEEE 802.20, Wireless broadband, etc. The pseudo-autocorrelation function is usually not considered and is implicitly assumed to be zero While this is the optimal strategy when dealing with proper complex random processes [11], it turns out to be sub-optimal in situations where the transmitted signals and/or interference are improper complex random processes, for which the pseudo-autocorrelation function is non-vanishing, and the performance of a linear receiver can be improved by the use of widely linear processing (WLP) [12]. Arises when transmitting symbols with improper modulation formats (e.g., ASK and OQPSK) over complex channels It was shown in Schreier et al [10] that the performance gain of WLP compared to conventional processing in terms of mean square error can be as large as a factor of 2. The pseudo-autocorrelation Crr and pseudo-cross-correlation C *rs are implicitly assumed to be zero, leading to sub-optimal solutions

FDE converges to the conventional FDE since

For Ψ

Number of flops

Conclusion