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Here, we propose a mathematical model and a calibration procedure for a PSD (position sensitive device) sensor equipped with an optical system, to enable accurate measurement of the angle of arrival of one or more beams of light emitted by infrared (IR) transmitters located at distances of between 4 and 6 m. To achieve this objective, it was necessary to characterize the intrinsic parameters that model the system and obtain their values. This first approach was based on a pin-hole model, to which system nonlinearities were added, and this was used to model the points obtained with the nA currents provided by the PSD. In addition, we analyzed the main sources of error, including PSD sensor signal noise, gain factor imbalances and PSD sensor distortion. The results indicated that the proposed model and method provided satisfactory calibration and yielded precise parameter values, enabling accurate measurement of the angle of arrival with a low degree of error, as evidenced by the experimental results.

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This paper focuses on optimal sensor deployment for indoor localization with a multi-objective evolutionary algorithm. Our goal is to obtain an algorithm to deploy sensors taking the number of sensors, accuracy and coverage into account. Contrary to most works in the literature, we consider the presence of obstacles in the region of interest (ROI) that can cause occlusions between the target and some sensors. In addition, we aim to obtain all of the Pareto optimal solutions regarding the number of sensors, coverage and accuracy. To deal with a variable number of sensors, we add speciation and structural mutations to the well-known non-dominated sorting genetic algorithm (NSGA-II). Speciation allows one to keep the evolution of sensor sets under control and to apply genetic operators to them so that they compete with other sets of the same size. We show some case studies of the sensor placement of an infrared range-difference indoor positioning system with a fairly complex model of the error of the measurements. The results obtained by our algorithm are compared to sensor placement patterns obtained with random deployment to highlight the relevance of using such a deployment algorithm.

A new measuring architecture for phase-based in frared ranging applied to indoor positioning is presented. The motivation to develop this proposal was to reduce the critical effect of multipath interferences on the differential distances estimated by the ranging system. The multipath mitigation feature of the proposed system is based on applying a spread spectrum modulation on the emitted signal so that the line-of sight component reaching the receivers can be discriminated from the non-line-of-sight components by applying a selective coherent demodulation. An overview of the system architecture is provided, together with the first approach to the model of the demodulation process and its validation. The conclusions obtained from the study of the proposal are used to provide preliminary results of the mitigation capabilities of the system, and to analyze the key issues involved in its implementation. The results show that the effectiveness of the proposal is strongly related with the infrared link bandwidth. Mitigation levels above 50% for multipath 4.5 meters longer than the direct path are reached if the infrared link bandwidth is higher than 200 MHz.