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Position Location by Time Reversal in Communication Networks
"... Abstract — Multipath effects are significant in urban or indoor communications. Current position location techniques such as TDOA suffer from multipath effects, which reduces the estimation accuracy. In this paper we propose time-reversal in a wireless communication network, where a mobile terminal ..."
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Abstract — Multipath effects are significant in urban or indoor communications. Current position location techniques such as TDOA suffer from multipath effects, which reduces the estimation accuracy. In this paper we propose time-reversal in a wireless communication network, where a mobile terminal wants to determine, through feedback, its own position in the request of the base station. The proposed method improves the estimation accuracy and reduces the estimation variance compared with correlation based method. We derive the closed form of the Cramer-Rao bound (CRB) on the time reversal estimation and the correlation estimation, showing that time reversal achieves a smaller CRB than the correlation method. Numerical examples are presented to illustrate the behavior of these bounds.
Article Data Communications Using Guided Elastic Waves by Time Reversal Pulse Position Modulation: Experimental Study
, 2013
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Time-Reversal Massive Multipath Effect: A Single-Antenna "Massive MIMO" Solution
"... Abstract The explosion of mobile data traffic calls for new efficient 5G technologies beyond what current 4G LTE can provide. Massive MIMO, which has shown the great potential in improving the achievable rate with a very large number of antennas, becomes a popular candidate. However, several critic ..."
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Abstract The explosion of mobile data traffic calls for new efficient 5G technologies beyond what current 4G LTE can provide. Massive MIMO, which has shown the great potential in improving the achievable rate with a very large number of antennas, becomes a popular candidate. However, several critical challenges in designing the analog front-end and coordinating the large-scale antenna array have to be carefully addressed before the massive MIMO can be actually adopted. Therefore, a natural question to ask is: does there exist a good alternative that can achieve similar system performance to massive MIMO with a simpler design? In this paper, we show that by using time-reversal approach, with a sufficiently large bandwidth, one can harvest massive multipath naturally existing in the environment to form high number of virtual antennas to achieve the desired massive MIMO effect with a single antenna. We answer the above question by analyzing the time-reversal massive multipath effect (TRMME) and the achievable rate with different signature waveforms. We also derive the corresponding asymptotic achievable rate under a massive multipath setting. Experiment result based on real channel measurements shows the approach to realize the massive multipaths in practical environment. Moreover, based on our experiment with real indoor measurement, even with only a single antenna, the time-reversal wideband system can achieve comparable performance as the massive MIMO system in terms of expected achievable rate.
Capacity, MSE and Secrecy Analysis of Linear Block Precoding for Distributed Antenna Systems in Multi-User Frequency-Selective Fading Channels
, 2011
"... Block transmission with cyclic prefix is a promising technique to realize high-speed data rates in frequency-selective fading channels. Many popular linear precoding schemes, including orthogonal frequency-division multiplexing (OFDM), single-carrier (SC) block transmission, and time-reversal (TR), ..."
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Block transmission with cyclic prefix is a promising technique to realize high-speed data rates in frequency-selective fading channels. Many popular linear precoding schemes, including orthogonal frequency-division multiplexing (OFDM), single-carrier (SC) block transmission, and time-reversal (TR), can be interpreted as such a block transmission. This paper presents a unified performance analysis that shows how the optimal precoding strategy depends on the optimization criterion such as capacity, mean-square error, and secrecy. We analyze three variants of TR methods (based on maximum-ratio combining, equal-gain combining and selective combining) and two-types of pre-equalization methods (zero-forcing and minimum mean-square error). As one application of our framework, we derive optimal precoding (i.e., OFDM with optimal power and phase control) in the presence of interference limitation for distributed antenna systems; we find that without power/phase control, OFDM does not have any capacity advantage over SC transmissions. When comparing SC and TR, we verify that for single-antenna systems in the high SNR regimes, SC has a capacity advantage; however, TR performs better in the low SNR regime. For distributed multiple-antenna systems, TR always provides higher capacity, and
Unified Analysis of Linear Block Precoding for Distributed Antenna Systems
, 2009
"... Block transmission with cyclic prefix is a promising technique to realize high-speed data rates in frequency selective fading channels. Many popular linear precoding schemes, including orthogonal frequency-division multiplexing (OFDM), single-carrier (SC) block transmission, and time-reversal (TR), ..."
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Block transmission with cyclic prefix is a promising technique to realize high-speed data rates in frequency selective fading channels. Many popular linear precoding schemes, including orthogonal frequency-division multiplexing (OFDM), single-carrier (SC) block transmission, and time-reversal (TR), can be interpreted as such a block transmission. This paper presents a unified performance analysis which shows how the optimal precoding strategy depends on the receiver type and the optimization criterion (capacity and mean-square error). We analyze three variants of TR methods (based on maximum-ratio combining, equal-gain combining and selective combining) and two-types of pre-equalization methods (zero-forcing and minimum mean-square error). As one application of our framework, we derive optimal power control for OFDM in the presence of interference limitation for distributed antenna systems; we find that without power control, OFDM does not have any capacity advantage over SC transmissions. When comparing SC and TR, we find that for single-antenna systems at high SNRs, SC has a capacity advantage; however, TR performs better in the low SNR regime. For multiple-antenna systems, TR always provides higher capacity, and the capacity of TR can approach that of optimal precoders with a number of distributed antennas.
15. SUBJECT TERMS
"... The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comm ..."
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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggesstions for reducing this burden, to Washington
SPACE-TIME REVERSAL TECHNIQUES FOR INFORMATION RETRIEVAL IN WIRELESS SENSOR NETWORKS
"... In this paper, we explore the benefits of space-time reversal (STR) techniques in the context of information retrieval in wireless sen-sor networks under the recently proposed Active Wireless Sensing (AWS) framework. In AWS, individual sensors are differentiated via their distinct space-time signatu ..."
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In this paper, we explore the benefits of space-time reversal (STR) techniques in the context of information retrieval in wireless sen-sor networks under the recently proposed Active Wireless Sensing (AWS) framework. In AWS, individual sensors are differentiated via their distinct space-time signatures and STR schemes exploit these sensor signatures. In the downlink, STR techniques are proposed to address individual sensors thus enabling sensor programming for different information retrieval or sensing modes. In the uplink, we propose an STR scheme for localizing distinct sensor responses to distinct signal space dimensions at the WIR thereby reducing in-terference between sensor transmissions. Furthermore, it does not require explicit estimation of sensor signatures at the WIR. The ben-efits of STR techniques in both scenarios are quantified analytically and illustrated with physically meaningful simulation results. 1.
