Adaptive low-rank channel estimation for multi-band OFDM ultra-wideband communications
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RESEARCH
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Adaptive low-rank channel estimation for multiband OFDM ultra-wideband communications Chia-Chang Hu* and Shih-Chang Lee
Abstract In this paper, an adaptive channel estimation scheme based on the reduced-rank (RR) Wiener filtering (WF) technique is proposed for multi-band (MB) orthogonal frequency division multiplexing (OFDM) ultra-wideband (UWB) communication systems in multipath fading channels. This RR-WF-based algorithm employs an adaptive fuzzy-inference-controlled (FIC) filter rank. Additionally, a comparative investigation into various channel estimation schemes is presented as well for MB-OFDM UWB communication systems. As a consequence, the FIC RR-WF channel estimation algorithm is capable of producing the bit-error-rate (BER) performance similar to that of the full-rank WF channel estimator and superior than those of other interpolation-based channel estimation schemes. Keywords: channel estimation, MB-OFDM, ultra-wideband (UWB), Wiener filter
1. Introduction Ultra-wideband (UWB) wireless systems have generated considerable interest as an indoor short-distance highdata-rate transmission in wireless communications over the past few years. A number of promising advantages, such as low power consumption, low cost, low complexity, noise-like signal, resistant to dense multipath and jamming, and excellent time-domain resolution, have made UWB systems perfectly suitable for personal computing (PC), consumer electronics (CE), mobile applications, and home entertainment networks. Applications of UWB radio techniques to short-range wireless communications, such as sensor networks and wireless personal area networks (WPANs), are currently being explored [1]. Two competing UWB technologies for physical layer (PHY) of the WPANs are investigated by the IEEE 802.15.3a standards task group (TG3a) [2]. One is the direct-sequence (DS) UWB link scheme and the other is the multi-band (MB) orthogonal frequency division multiplexing (OFDM) UWB system. The MB-OFDM UWB communication systems [3] have recently drawn extensive attention due to potential for providing high data rate under a low transmission power. The MB-OFDM developed by the WiMedia Alliance [4] is the first UWB radio transmission technology * Correspondence: [email protected] Department of Communications Engineering, National Chung Cheng University 168 University Road, Min-Hsiung, Chia-Yi 621, Taiwan
to obtain international standardization. This promising wireless-connectivity technique increases successfully both the traffic capacity and the frequency diversity. In MB-OFDM UWB wireless systems, by utilizing several types of time-frequency codes (TFCs) in the preamble part, multiple users are allowed to use the same frequency-band group simultaneously to provide frequency diversity as well as channelization and multiple-access capability among different piconets. That is the primary reason why the preamble symbols gain a high probability of being corrupted by multiple-access interference (MAI). To enhance the system performance, pilotassi
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