Abstract
Widely linear (WL) minimum mean square error (MMSE) channel estimation scheme have been proposed for multiband orthogonal frequency division multiplexing ultra-wideband (MB-OFDM UWB) systems dealing with non-circular signals. This WLMMSE channel estimation scheme provides significant performance gain, but it presents a high computational complexity compared with the linear one. In this paper, we derive an adaptive WLMMSE channel estimation scheme that significantly reduces the computational complexity. The complexity reduction is done in two stages. The first stage consists of a real evaluation of the WLMMSE channel estimator and the second stage follows with a reduced-rank filtering based on the singular value decomposition (SVD). Computational complexity evaluation shows that the proposed low-rank real-valued WLMMSE channel estimator has computation cost comparable with the linear MMSE. Additionally, simulations of the bit error rate (BER) performance show comparable performance with the WLMMSE channel estimator especially at high signal-to-noise ratio (SNR).
Highlights
Over the past few years, ultra-wideband (UWB) has been promised as an efficient technology for future wireless short-range high data rate communication [1]
The simulation results of the proposed scheme for code division multiple access (CDMA) interference suppression show a performance significantly better than existing schemes and close to the optimal fullrank minimum mean square error (MMSE)
The results have shown that the proposed technique improves the performance of the TD-SCDMA system with low-rank processing and low computation complexity
Summary
Over the past few years, ultra-wideband (UWB) has been promised as an efficient technology for future wireless short-range high data rate communication [1]. Li et al have proposed a low-complexity channel estimator developed by first averaging the overlap-added (OLA) received preamble symbols within the same band and applying time-domain least squares method followed by the discrete Fourier transform [9]. The discrete-time UWB channel is modeled as a Nh-tap finite-impulse-response (FIR) filter whose channel frequency response (CFR) of the lth OFDM symbol on its corresponding sub-band is given by: HðlÞ 1⁄4 1⁄2Hðl; 0Þ; Hðl; 1Þ; ...; Hðl; NIFFT−1ÞT ð4Þ where (⋅)T denotes the transposition operation. Since the proposed MB-OFDM UWB system is dealing with non-circular signals, it requires widely linear processing to take into account all the second-order statistics of the channel conditions and the received signal. 3.2 WLMMSE estimator We denote the widely linear estimator of the augmented transfer function of channel ⌣H by: Hb WLMMSE 1⁄4 ⌣A ⌣Y ð10Þ
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