Theoretical analysis and compensation for the joint effects of HPA nonlinearity and RF crosstalk in VBLAST MIMO-OFDM systems over Rayleigh fading channel

Ridha Bouallegue,Oussama B Belkacem,Maha Cherif Dakhli,Rafik Zayani

doi:10.1186/1687-1499-2014-61

Ridha Bouallegue, Oussama B Belkacem + Show 2 more

Open Access

https://doi.org/10.1186/1687-1499-2014-61

Copy DOI

Abstract

In this paper, we investigate the joint effects of nonlinear distortions due to high-power amplifier (HPA) and radio-frequency (RF) crosstalk on the performance of a multiple-input multiple-output-orthogonal frequency division multiplexing (MIMO-OFDM) system. The performance of the vertical bell laboratories layered space-time (VBLAST) MIMO-OFDM system, in terms of bit error rate (BER) and system capacity, is derived and evaluated for a Rayleigh flat fading channel. In the performance analysis, M-ary quadrature amplitude modulation (M-QAM) is considered and the joint effects of nonlinear HPA distortions and RF crosstalk are studied. Theoretical results and comparisons are provided for several system parameters, such as the input back-off (IBO) and crosstalk intensity. It is shown that the results obtained from the theoretical study are very close to the ones obtained from the simulation. Indeed, we introduce a nonlinear distortion cancellation (NDC) technique to estimate and mitigate nonlinear distortions and crosstalk effects jointly.

Highlights

The combination of multiple-input multiple-output (MIMO) and orthogonal frequency division multiplexing (OFDM) guarantees high performance with high data rates in 4G broadband wireless communications [1]
4.1.2 Nonlinear MIMO-OFDM system The analysis presented is based on the assumption that the distortion caused by the high-power amplifier (HPA) can be modeled as additive Gaussian noise, whose variance depends on the input signal and the nonlinearity HPA characteristics
New closed-form pdf signal-tonoise ratios are derived in order to develop theoretical expressions of the average bit error rate (BER) in different scenarios: nonlinear MIMO-OFDM system and nonlinear MIMOOFDM system with crosstalk

Summary

Introduction

The combination of multiple-input multiple-output (MIMO) and orthogonal frequency division multiplexing (OFDM) guarantees high performance with high data rates in 4G broadband wireless communications [1]. OFDM combats frequency-selective fading effectively by dividing a wideband frequency-selective fading channel into parallel narrowband flat fading subchannels, while MIMO systems increase the data rate significantly over single-input single-output (SISO) systems by employing multiple transmit and receive antennas. Crosstalk or coupling effect is the result of the interference between the signals of different paths, and it affects the quality of the transmitted signal and degrades the system performance. This type of crosstalk can be linear or nonlinear as explained in [2], where the authors discussed the difference between linear MIMO crosstalk, which is relatively benign since it is being corrected by the MIMO equalizer, and nonlinear crosstalk that is generated before the HPA. HPA nonlinearity in SISO-OFDM systems was investigated in [3], where the output at the HPA is expressed as the summation of the input signal multiplied by a complex scale factor, and an additive Gaussian noise which is uncorrelated with the input signal

Objectives

Results

Conclusion