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Spatiotemporal Focusing of Phase Compensation and Time Reversal in Ultrawideband Systems With Limited Rate Feedback | IEEE Journals & Magazine | IEEE Xplore

Spatiotemporal Focusing of Phase Compensation and Time Reversal in Ultrawideband Systems With Limited Rate Feedback


Abstract:

We investigate the performance of phase compensation (PC) and time reversal pre-equalizers in multipath indoor channels when a quantized version of the channel state info...Show More

Abstract:

We investigate the performance of phase compensation (PC) and time reversal pre-equalizers in multipath indoor channels when a quantized version of the channel state information (CSI) is available at the transmitter side. We conduct a comprehensive experimental study to assess their spatial and temporal focusing as a function of the number of quantization levels over the frequency band of 2-12 GHz. To characterize multipath compression performance, root-mean-square (RMS) delay spread and peak-to-average power ratio (PAPR) are calculated for different numbers of quantization levels. Bit error rate (BER) curves have been simulated for data rates in the range of 125-4000 Mb/s based on the measured channel responses. To assess spatial focusing, we investigate the decay of the received response peak power as we move away from the intended receiver. Our study suggests that for the same feedback rate, PC has considerably superior performance in suppressing multipath dispersions and focusing the transmitted energy at the intended receiver.
Published in: IEEE Transactions on Vehicular Technology ( Volume: 65, Issue: 4, April 2016)
Page(s): 1998 - 2006
Date of Publication: 07 April 2015

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I. Introduction

Ultrawideband (UWB) is a radio technology for future wireless communication, radar, and imaging systems [1], [2]. Although this technology offers several unique advantages such as multipath immunity, high data rate, and strong antijamming ability [3], there are a number of practical challenges, which are topics of current research. One key challenge is the increased multipath dispersion, which results because of the fine temporal resolution [4]. Although such challenges have been investigated to some extent, they have not been fully explored in connection with transmit beamforming techniques in realistic multipath environments [5]– [11]. Beamforming is a transmission technique that can be employed to combat the multipath dispersion and provide temporal and spatial focusing at the target receiver. The temporal compression leads to an improved signal-to-noise ratio (SNR), which reduces the intersymbol interference in high-speed wireless communications [5], [11]. On the other hand, spatial focusing means that the received power decreases away from the target location, leading to lower probabilities of intercept by an eavesdropper or interuser interference in a secure multiuser communication channel [7], [12]– [14]. Due to this spatiotemporal focusing, the receiver complexity is shifted to the transmitter side, and a simpler receiver's structure can be employed to capture the received energies. As an example, time reversal (TR) [15]– [17] is one of the well-known beamformers in which the flipped version of the channel impulse response is used as a prematched filter. When the time-reversed signal is transmitted back through the same channel, multipath components arrive constructively aligned at the target receiver at a particular time.

References

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