Transmit antenna subset selection for high-rate MIMO-OFDM systems in the presence of nonlinear power amplifiers
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RESEARCH
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Transmit antenna subset selection for high-rate MIMO-OFDM systems in the presence of nonlinear power amplifiers Ngoc Phuc Le*, Farzad Safaei and Le Chung Tran
Abstract The deployment of antenna subset selection on a per-subcarrier basis in MIMO-OFDM systems could improve the system performance and/or increase data rates. This paper investigates this technique for the MIMO-OFDM systems suffering nonlinear distortions due to high-power amplifiers. At first, some problems pertaining to the implementation of the conventional per-subcarrier antenna selection approach, including power imbalance across transmit antennas and noncausality of antenna selection criteria, are identified. Next, an optimal selection scheme is devised by means of linear optimization to overcome those drawbacks. This scheme optimally allocates data subcarriers under a constraint that all antennas have the same number of data symbols. The formulated optimization problem to realize the constrained scheme could be applied to the systems with an arbitrary number of multiplexed data streams and with different antenna selection criteria. Finally, a reduced complexity strategy that requires smaller feedback information and lower computational effort for solving the optimization problem is developed. The efficacy of the constrained antenna selection approach over the conventional selection approach is analyzed directly in nonlinear fading channels. Simulation results demonstrate that a significant improvement in terms of error performance could be achieved in the proposed system with a constrained selection compared to its counterpart. Keywords: Antenna subset selection; MIMO-OFDM UWB systems; Nonlinear power amplifier; Power balancing; Linear optimization
1 Introduction Recent years have seen a great demand for very fast data speeds in wireless multimedia applications. One of the most attractive techniques that could deliver high-rate transmission is multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) [1]. The major benefits of this technique resulting from OFDM include high spectral efficiency and robustness against intersymbol interference (ISI) in multipath fading channels [1]. Simultaneously, an increased capacity and/or diversity gain could be achieved with MIMO [2,3]. Among various MIMO schemes, antenna selection appears to be promising for OFDM wireless systems. This is mainly due to low-cost implementation and small amount of feedback information required, in comparison with other precoding methods [4]. In addition, this scheme is shown to * Correspondence: [email protected] School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Wollongong, New South Wales 2522, Australia
be effective in equivalent isotropic radiated power (EIRP)restricted systems, such as ultra-wideband (UWB) [5,6]. Many research works have considered the application of antenna selection in OFDM systems, e.g., in [7-13]. In general, they can be categorized into two approaches: bulk select
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