Abstract
In cooperative localization systems, wireless nodes need to exchange accurate position-related information such as time-of-arrival (TOA) and angle-of-arrival (AOA), in order to obtain accurate location information. One alternative for providing accurate position-related information is to use ultra-wideband (UWB) signals. The high time resolution of UWB signals presents a potential for very accurate positioning based on TOA estimation. However, it is challenging to realize very accurate positioning systems in practical scenarios, due to both complexity/cost constraints and adverse channel conditions such as multipath propagation. In this paper, a two-step TOA estimation algorithm is proposed for UWB systems in order to provide accurate TOA estimation under practical constraints. In order to speed up the estimation process, the first step estimates a coarse TOA of the received signal based on received signal energy. Then, in the second step, the arrival time of the first signal path is estimated by considering a hypothesis testing approach. The proposed scheme uses low-rate correlation outputs and is able to perform accurate TOA estimation in reasonable time intervals. The simulation results are presented to analyze the performance of the estimator.
Highlights
Communications, positioning, and imaging systems that employ ultra-wideband (UWB) signals have drawn considerable attention [1,2,3,4,5]
In order to prevent catastrophic collisions among pulses of different users and provide robustness against multiple access interference (MAI), each information symbol is represented by a sequence of pulses; the positions of the pulses within that sequence are determined by a pseudo-random time hopping (TH) sequence specific to each user [7]
Numerical studies and simulations are performed in order to evaluate the expressions in Section 3.4, and to investigate the performance of the proposed TOA estimator over realistic IEEE 802.15.4a channel models [43, 49]
Summary
Communications, positioning, and imaging systems that employ ultra-wideband (UWB) signals have drawn considerable attention [1,2,3,4,5]. Maximum likelihood (ML) approaches to TOA estimation of UWB signals can get quite close to the theoretical limits for high signal-to-noise ratios (SNRs) [14, 15] They generally require joint optimization over a large number of unknown parameters (channel coefficients and delays for multipath components). A lowcomplexity timing offset estimation technique, called timing with dirty templates (TDT), is proposed in [23, 26,27,28], which employs “dirty templates” in order to obtain timing information based on symbol-rate samples This algorithm provides timing information at low complexity and in short time intervals, the TOA estimate obtained from the algorithm has an ambiguity equal to the extent of the noise-only region between consecutive symbols.
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