Canceling Interferences for High Data Rate Time Reversal MIMO UWB System: A Precoding Approach
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Research Article Canceling Interferences for High Data Rate Time Reversal MIMO UWB System: A Precoding Approach Taotao Wang and Tiejun Lv School of Information and Communication Engineering, Beijing University of Posts and Telecommunications (BUPT), Beijing 100876, China Correspondence should be addressed to Tiejun Lv, [email protected] Received 3 December 2010; Accepted 9 February 2011 Academic Editor: Sangarapillai Lambotharan Copyright © 2011 T. Wang and T. Lv. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. An ultra-high data rate time reversal (TR) multiple-input multiple-output (MIMO) ultra-wideband (UWB) communication system with space-time precoding is proposed. When the symbol duration is set to approach the duration of UWB monocycles, the data rate is close to the limit, resulting in the severe intersymbol interference (ISI). The zero-forcing (ZF) criterion-based spacetime precoding presented in this paper eliminates both ISI and multistream interference (MSI) caused by spatial multiplexing at the sampling time. With less demand for the degree of freedom (the number of antennas) than other existing schemes, the proposed scheme enables the data rate to reach the order of Gbps without losing bit error rate (BER) performance. Since TR signal preprocessing and the proposed precoding both require the channel state information (CSI), a simple but effective channel estimation algorithm is also proposed to evaluate the impact of channel estimation on the proposed scheme.
1. Introduction Ultra-wideband (UWB) impulse radio communications, as a promising candidate for location-aware indoor communications, wireless sensor networks (WSN) and wireless personal area network (WPAN), has received significant attention in both academia and industry in recent years [1, 2]. The most attractive feature of UWB is its potential to offer great capacity in theory as compared with the narrowband systems. However, the conventional UWB system shows much lower data rate than expectation. This is because capturing the energy of dense multipath channel [3] and combating severe intersymbol interference (ISI) caused by large maximum excess delay of the channel [4] will increase receiver complexity which limits both detection performance and data rate under the condition that receivers with high complexity are not preferred in UWB short-range applications. To reduce receiver complexity, noncoherent scheme is developed to bypass the complicated treatments on UWB channel, whereas the deterioration of detection performance and the reduction of data rate are inevitable [5]. On the other hand, the system complexity can be shifted
from the receiver to the transmitter, where the power and computation resources are generally enough to implement signal processing. Since preprocessing the signal before transmission may cope with the deteriorating effects of the channel, the receiver
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