Current Issue : July - September Volume : 2013 Issue Number : 3 Articles : 4 Articles
We present experimental evaluations of human-induced perturbations on received-signal-strength-(RSS-) based ranging measurements\r\nfor cooperative mobile positioning. To the best of our knowledge, this work is the first attempt to gain insight and understand\r\nthe impact of both body loss and hand grip on the RSS for enhancing proximity measurements among neighbouring devices\r\nin cooperative scenarios. Our main contribution is represented by experimental investigations. Analysis of the errors introduced\r\nin the distance estimation using path-loss-based methods has been carried out. Moreover, the exploitation of human-induced\r\nperturbations for enhancing the final positioning accuracy through cooperative schemes has been assessed. It has been proved that\r\nthe effect of cooperation is very limited if human factors are not taken into account when performing experimental activities....
Autonomous Navigation Systems used in missiles and other high dynamic platforms are mostly dependent on the Global\r\nPositioning System (GPS). GPS users face limitations in terms of missile high dynamics and signal interference. Receiver�s tracking\r\nloops bandwidth requirements to avoid these problems are conflicting. The paper presents a novel signal frequency and phase\r\ntracking algorithm for very high dynamic conditions, which mitigates the conflicting choice of bandwidths and reduces tracking\r\nloop measurement noise. It exploits the flexibility of fuzzy control systems for directly generating the required Numerically\r\nControlled Oscillator (NCO) tuning frequency using phase and frequency discriminators information and is labeled Fuzzy\r\nFrequency Phase Lock Loop (FFPLL). Because Fuzzy Systems can be computationally demanding and an InertialNavigation System\r\n(INS) is often onboard the vehicle, an assisted INS Doppler version has been designed and is also proposed. Assessment of the new\r\nGPS tracking method is performed with both simulated and experimental data under jamming conditions.Themain enhancements\r\nof the proposed system consist in reduced processing time, improved tracking continuity and faster reacquisition time....
Indoor navigation is challenging due to unavailability of satellites-based signals indoors. Inertial Navigation Systems (INSs) may be\r\nused as standalone navigation indoors. However, INS suffers from growing drifts without bounds due to error accumulation. On\r\nthe other side, the IEEE 802.11 WLAN (WiFi) is widely adopted which prompted many researchers to use it to provide positioning\r\nindoors using fingerprinting. However, due to WiFi signal noise and multipath errors indoors, WiFi positioning is scattered and\r\nnoisy. To benefit from both WiFi and inertial systems, in this paper, two major techniques are applied. First, a low-cost Reduced\r\nInertial Sensors System (RISS) is integrated with WiFi to smooth the noisy scattered WiFi positioning and reduce RISS drifts.\r\nSecond, a fast feature reduction technique is applied to fingerprinting to identify the WiFi access points with highest discrepancy\r\npower to be used for positioning. The RISS/WiFi system is implemented using a fast version of Mixture Particle Filter for state\r\nestimation as nonlinear non-Gaussian filtering algorithm. Real experiments showed that drifts of RISS are greatly reduced and\r\nthe scattered noisy WiFi positioning is significantly smoothed. The proposed system provides smooth indoor positioning of 1m\r\naccuracy 70% of the time outperforming each system individually....
This paper presents a ranging receiver architecture able to timestamp IEEE 802.11bWireless LAN signals with sub-100 picosecond\r\nprecision enabling time-based range measurements. Starting from the signal model, the performance of the proposed architecture\r\nis assessed in terms of statistical bounds when perturbed by zero-mean additive white Gaussian noise (AWGN) as well as in case\r\nof multipath propagation. Results of the proposed architecture, implemented in a Field Programmable Gate Array-(FPGA-) based\r\nprototype, are presented for different environments. For AWGN channels, the prototype system is able to attain an accuracy of\r\n1.2 cm while the ranging accuracy degrades in dynamic multipath scenarios to about 0.6m for 80% of the measurements due to\r\nthe limited bandwidth of the signal....
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