Dect architecture proposal for a construction site

A construction site is an specific environment where important propagation related issues have to be considered. In particular an important problem concerns the coverage of buildings under construction and therefore continuously changing. The deployment of a DECT system in such scenarios can not be carried out as usually, by means of DECT base stations linked by cables. Another specific problem is that no measures can be done prior to decide the best place for the antennas since initially the building does not exist. In this paper a way to solve both problems is proposed through a specific system architecture, a propagation model and a combination of software with a CAD tool.Peer ReviewedPostprint (published version

Performance of two branch space and polarization diversity at 900 MHz

This work summarizes the results of a measurement campaign undertaken to evaluate the performance of two branch space and polarization diversity schemes at 900 MHz in different environments (urban, suburban, rural flat and rural hilly). A total number of 783 runs were made covering these sites and using different transmitter antennas (vertical polarized roof-top antenna, handheld randomly inclined) at differents speeds (walking, by car at 30 up to 80 km/h). Comparison between the two types of diversity schemes have been made through calculation of the statistics of mean received signal level, diversity gain, incremental diversity gain and envelope cross-correlationPeer ReviewedPostprint (published version

Chip level simulation of the downlink in UTRA-FDD

The specifications of UMTS Terrestrial Radio Access (UTRA) for the physical layer of the downlink make use of orthogonal variable spreading factor (OVSF) codes to preserve the orthogonality between downlink channels of different rates and spreading factors. This technique minimises the downlink intra-cell interference. In order to control the inter-cell interference, every base station multiplies the global downlink signal with a cell specific Gold code (scrambling code). Then, while the inter-cell interference may be modelled using the Gaussian hypothesis (that is: replacing the real interference with a Gaussian noise of the same power), the intra-cell interference requires detailed chip level simulations. In this paper we present results of a chip level simulation of the downlink UTRA physical layer. The objective is to evaluate the raw (uncoded) mean bit error rate (BER) of the system in a realistic environment and conditions. Then, by knowing the BER requirements of the different services, one can easily obtain the maximum capacity in terms of simultaneous connections at any combination of bit rates.Peer ReviewedPostprint (published version

Frequency planning optimisation in real mobile networks

Due to the annual increase of cellular subscribers, there is a growing interest by the network operators, in how to deploy the network infrastructure to achieve maximum capacity. A key point is the channel or frequency assignment, which implies efficiently assigning frequencies from a limited set, to each cell, while satisfying the electromagnetic compatibility constraints.Peer ReviewedPostprint (published version

Average power prediction in microcells

A propagation model to estimate the average received power in an urban microcell environment has been developed. This model can be used both in line of sight (LOS) and non line of sight (NLOS) conditions in any regular or irregular microcell structure.Peer ReviewedPostprint (published version

Aprendizaje basado en proyectos: cómo empezar ya

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Machine learning techniques applied to multiband spectrum sensing in cognitive radios

This research received funding of the Mexican National Council of Science and Technology (CONACYT), Grant (no. 490180). Also, this work was supported by the Program for Professional Development Teacher (PRODEP).In this work, three specific machine learning techniques (neural networks, expectation maximization and k-means) are applied to a multiband spectrum sensing technique for cognitive radios. All of them have been used as a classifier using the approximation coefficients from a Multiresolution Analysis in order to detect presence of one or multiple primary users in a wideband spectrum. Methods were tested on simulated and real signals showing a good performance. The results presented of these three methods are effective options for detecting primary user transmission on the multiband spectrum. These methodologies work for 99% of cases under simulated signals of SNR higher than 0 dB and are feasible in the case of real signalsPeer ReviewedPostprint (published version

Cancelación del ruido AM en sistemas de transmisión coherentes por fibra óptica: receptor balanceado

In this work the authors have studied the AM noise influence over coherent transmission systems employing heterodyne-type detection. A dual-detector optical heterodyne receiver is also studied in arder to eliminate the LO noise. Finally a comparison between the two schemes has been done.Peer ReviewedPostprint (published version

Laser noise impact in the design of an heterodyne optical PSK receiver

An evaluation of the performance of a coherent optical receiver for binary PSK (phase-shift keying) is carried out. Both AM and FM noise due to transmitter and local oscillator semiconductor lasers have been taken into account. The nonlinear dependence between the phase noise variance and the laser linewidth is considered. A heterodyne receiver is studied in terms of its output SNR (signal-to-noise ratio), taking into account AM noise and both thermal and shot noises. The required SNR to achieve a BER (bit error rate) of 10-9 is studied, considering the FM noise in both semiconductor lasers. The importance of taking into account the effects of AM and FM noise in the investigation of the receiver sensitivity in a binary PSK coherent optical system is demonstrated. An accurate evaluation of the penalty in the sensitivity due to the laser quantum noise is obtained. It is shown that the AM noise due to the laser working as local oscillator degrades the expected SNRPeer ReviewedPostprint (published version

Software tool for optimising indoor/outdoor coverage in a construction site

A system architecture, an empirical propagation model, and a software combined with a CAD tool, have been designed to offer mobile communication services to construction sites. Results have been validated by measurements.Peer ReviewedPostprint (published version