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MIMO OFDM receivers for Systems with IQ imbalances | IEEE Journals & Magazine | IEEE Xplore

MIMO OFDM receivers for Systems with IQ imbalances


Abstract:

Orthogonal frequency division multiplexing (OFDM) is a widely recognized modulation scheme for high data rate communications. However, the implementation of OFDM-based sy...Show More

Abstract:

Orthogonal frequency division multiplexing (OFDM) is a widely recognized modulation scheme for high data rate communications. However, the implementation of OFDM-based systems suffers from in-phase and quadrature-phase (IQ) imbalances in the front-end analog processing. Such imbalances are caused by the analog processing of the received radio frequency (RF) signal, and they cannot be efficiently or entirely eliminated in the analog domain. The resulting IQ distortion limits the achievable operating SNR at the receiver and, consequently, the achievable data rates. The issue of IQ imbalances is even more severe at higher SNR and higher carrier frequencies. In this paper, the effect of IQ imbalances on multi-input multioutput (MIMO) OFDM systems is studied, and a framework for combating such distortions through digital signal processing is developed. An input-output relation governing MIMO OFDM systems is derived. The framework is used to design receiver algorithms with compensation for IQ imbalances. It is shown that the complexity of the system at the receiver grows from dimension (n/sub R//spl times/n/sub T/) for ideal IQ branches to (2n/sub R//spl times/2n/sub T/) in the presence of IQ imbalances. However, by exploiting the structure of space-time block codes along with the distortion models, one can obtain efficient receivers that are robust to IQ imbalances. Simulation results show significant improvement in the achievable BER of the proposed MIMO receivers for space-time block-coded OFDM systems in the presence of IQ imbalances.
Published in: IEEE Transactions on Signal Processing ( Volume: 53, Issue: 9, September 2005)
Page(s): 3583 - 3596
Date of Publication: 30 September 2005

ISSN Information:


I. Introduction

Orthogonal frequency division multiplexing (OFDM) is a widely adopted modulation technique for high-speed wireless communications. The OFDM-based physical layer has been chosen for several standards, such as the IEEE 802.11a wireless local area network (WLAN) in the 5-GHz band, the IEEE 802.11g wireless local area network (WLAN) in the 2.4 GHz band, and the European digital video broadcasting system (DVB-T). It is also under consideration as the high rate alternate physical layer to the draft IEEE P802.15.3 wireless personal area network (WPAN), the IEEE 802.20 mobile broadband wireless access (MBWA), and the IEEE 802.16 wireless metropolitan area networks (WirelessMAN). Considering the large demand for such systems, a low-cost, low-power, and fully integrated implementation of these standards is a challenge for the future high-speed wireless networks.

References

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