Ultra-Wideband (UWB) has a high interest in research and industry for accurate indoor positioning. This technology comprises signals with a bandwidth of at least 500 MHz at a power decay of -10dB. This large bandwidth conferes the capability of resolving multipath, penetrating through obstacles and accurate ranging. However, NLOS (Non-Line-Of-Sight) conditions produced by obstacles in indoor environments severely degrade performance, as they introduce a positive bias in ranging estimation. In this paper we present a robust UWB indoor positioning which is able to accurately operate in a highly complex indoor scenario, where NLOS condition is predominant. For that purpose, the system uses a NLOS detection algorithm based on the skewness of the estimated channel impulse response and it mitigates NLOS by using an Extended Kalman Filter. The use of this detection/mitigation algorithm shows an improvement of the RMSE in positioning about 67%.
SUMMARYIn this paper, a digital filter for the generation/correlation of binary Golay pairs of sequences of length 2 N Á 10 M Á 26 P (N, M and P are non-negative integers) is proposed. It is carried out by means of a novel Golay kernel 26 decomposition, also introduced in this paper, combined with building blocks of Golay kernels 2 and 10, presented in previous works. The proposed filter has a similar architecture to the digital filter for the generation/correlation of Golay multilevel pairs of sequences, where the parameters at intermediate stages have to be adjusted to obtain Golay binary pairs of sequences in the final stage.
This paper presents an extensive local ultrasonic positioning system for mobile robots (MRs) based on the fusion of the information from the MR internal odometer sensor and the measurements of position obtained with a set of external ultrasonic beacons that form an Ultrasonic Local Positioning System (ULPS). The extensive ULPS is formed using several single ULPS, each one of them covering a particular area of the total working area. In each single ULPS, five ultrasonic beacons are used that emit simultaneously and are detected by an ultrasonic receiver on board the MR. Direct Sequence Code Division Multiple Access (DS-CDMA) techniques have been used to avoid interferences between them. When the MR navigates on the working area, it continuously obtains its relative position thanks to the internal odometer. The cumulative errors of the odometer are corrected when the robot is on a place where the positioning data obtained with any of the single ULPS are available. The fusion of information (from odometer and ULPS) is made using an H-Infinite filter. The extensive ULPS has been built and tested experimentally.
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