A. Ayala

Error analysis of the simulated impulse response on indoor wireless optical channels using a Monte Carlo-based ray-tracing algorithm

This work describes a method to determine the error in a Monte Carlo-based ray-tracing algorithm used to compute the impulse response on indoor wireless optical channels. The algorithm, which accounts for multiple reflections of any order on irregularly shaped furnished rooms with diffuse and specular reflectors, allows for their analysis. Equations that estimate algorithm-produced error are given. We also report several simulation results concerning the error estimation which verify the reliability of the equations.

Application of PICs and Microcontrollers in the Measurement and Control of Parameters in Industry

This paper describes the use of microcontrollers in low-cost control applications. The main feature of the system is the use of programmable integrated circuits (PICs) to perform direct control processes within a plant. In this work, a control model based on distributed functions in levels is proposed to increase control task efficiency. With reference to a previous model, an efficient and simple control system is suggested for industrial applications. The designed system distributes its supervisory and control tasks in different units using commercial microcontroller devices. The results obtained with the previous system are described, which let us check the reliability and flexibility of the proposed model. Finally, several operational alternatives for the developed system are suggested.

Comparison of Monte Carlo ray-tracing and photon-tracing methods for calculation of the impulse response on indoor wireless optical channels

We present a comparison between the modified Monte Carlo algorithm (MMCA) and a recently proposed ray-tracing algorithm named as photon-tracing algorithm. Both methods are compared exhaustively according to error analysis and computational costs. We show that the new photon-tracing method offers a solution with a slightly greater error but requiring from considerable less computing time. Moreover, from a practical point of view, the solutions obtained with both algorithms are approximately equivalent, demonstrating the goodness of the new photon-tracing method.

Comparison of Three Non-Imaging Angle-Diversity Receivers as Input Sensors of Nodes for Indoor Infrared Wireless Sensor Networks: Theory and Simulation

In general, the use of angle-diversity receivers makes it possible to reduce the impact of ambient light noise, path loss and multipath distortion, in part by exploiting the fact that they often receive the desired signal from different directions. Angle-diversity detection can be performed using a composite receiver with multiple detector elements looking in different directions. These are called non-imaging angle-diversity receivers. In this paper, a comparison of three non-imaging angle-diversity receivers as input sensors of nodes for an indoor infrared (IR) wireless sensor network is presented. The receivers considered are the conventional angle-diversity receiver (CDR), the sectored angle-diversity receiver (SDR), and the self-orienting receiver (SOR), which have been proposed or studied by research groups in Spain. To this end, the effective signal-collection area of the three receivers is modelled and a Monte-Carlo-based ray-tracing algorithm is implemented which allows us to investigate the effect on the signal to noise ratio and main IR channel parameters, such as path loss and rms delay spread, of using the three receivers in conjunction with different combination techniques in IR links operating at low bit rates. Based on the results of the simulations, we show that the use of a conventional angle-diversity receiver in conjunction with the equal-gain combining technique provides the solution with the best signal to noise ratio, the lowest computational capacity and the lowest transmitted power requirements, which comprise the main limitations for sensor nodes in an indoor infrared wireless sensor network.

Laboratory experiment on the use of pulse code modulation to transmit audio digitally

In this paper we present a practical laboratory experiment intended for undergraduate and graduate Electronic Engineering courses on Digital Communications Systems. The main objective of the experiment is to design and implement the electronics of a baseband system that uses pulse code modulation (PCM) to transmit audio signals digitally.

Multi-user THSS system for visible light links

In this paper, a system based on time-hopping spread spectrum techniques for indoor visible light communications is studied via simulation. A 2-PPM modulation scheme is selected because it yields good results in wireless optical communications. Furthermore, the system allows for selecting the number of pulses per symbol to be transmitted and makes use of an optimum maximum-likelihood receiver for A WGN channels with the ability to choose between hard- or soft-decision decoding. The system designed allows for comparing the performance based on the computation of the bit error rate as a function of the pulse energy to noise power spectral density ratio, for different configurations in single-user and multi-user environments.

Multi-user THSS system for indoor wireless optical communications with angle-diversity detection

In this paper, an infrared wireless communications system based on THSS techniques employing angle-diversity detection is studied via simulation. Although the system is designed to operate at infrared wavelengths, it can also be used for Visible Light Communications (VLC). Time-Hopping codification is based on splitting the symbol period into several short slots. In order to specify which slots are used to transmit and which are not, the use of maximum length sequences is considered. The remaining time slots can be used by other users so as to provide the system with multiple access capabilities. In this paper, a 2-PPM modulation scheme is selected because it yields good results in infrared systems as well as in VLC. Furthermore, the THSS system allows for selecting the number of pulses per symbol to be transmitted and makes use of an optimum maximum-likelihood receiver for AWGN channels with the ability to choose between hard or soft decision decoding. The system designed allows for comparing the performance based on the computation of the bit error rate (BER) as a function of the pulse energy to noise power spectral density ratio, for different configurations in single-user and multi-user environments. The results show a significant enhancement when angle-diversity receivers are used as compared to employing receivers using a single-element detector with a wide field of view (FOV). In this paper, two angle-diversity structures are compared: conventional and sectored receivers. Although the sectored receiver exhibits better BER than the conventional receiver, its implementation is more complex.