M.A. Bacallado

Universidad de Las Palmas de Gran Canaria, Las Palmas, Canary Islands, Spain

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Publications (7)2.76 Total impact

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    ABSTRACT: This paper introduces new techniques for improving the security level of the wireless optical systems. In this way, we are going to use modulation schemes based on spread spectrum theory. These techniques had been developed for military applications in order to obtain reliable and secure communications, so they seem to be a good candidate for our systems. Spread spectrum systems perform a data encryption in the modulation process, and they are able to work in presence of high level interference and intentional jamming signals. On the other hand, these schemes can be also applied to optical barriers and perimeter control systems, because the spread spectrum signal improves the robustness and invulnerability of the security barriers
    Security Technology, 2005. CCST '05. 39th Annual 2005 International Carnahan Conference on; 11/2005
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    ABSTRACT: In this paper, the design and experimental testing of a direct-sequence spread spectrum (DSSS) system for wireless infrared LAN is presented. This method improves the wireless IR communications performances against multipath propagation and narrowband interference. We have implemented a IR-DSSS prototype with 100 MHz code frequency and 6 Mbps bit rate. We have also studied the effects of both Gaussian and sinusoidal signal conformation over wireless optical DSSS systems. These results show that these techniques reduce the adjacent-channel interference without loss of process gain or substantial reductions of BER vs. S/N performances. We also present some results about a simplified synchronization structure to be used on reduced-cost domestic equipment. These systems are suitable for different applications at low and medium rates, especially for in-house.
    IEEE Transactions on Consumer Electronics 06/2004; · 1.09 Impact Factor
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    ABSTRACT: In this paper, the design and experimental testing of a direct-sequence spread spectrum (DSSS) system for wireless indoor infrared network is presented. This method improves the wireless IR communications performances against multipath propagation and narrowband interference. We have implemented an IR-DSSS prototype with 100 MHz code frequency and about 6 Mbps bit rate. We also present some results on a simplified synchronization structure so as to be used on reduced-cost domestic equipment. These systems are suitable for different applications at low and medium rates, especially for in-house communications between domestic appliances.
    Control, Communications and Signal Processing, 2004. First International Symposium on; 02/2004
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    ABSTRACT: In this Letter the effect of using pulse conformation techniques over a DSSS wireless optical system is explored. The performances of both Gaussian and sinusoidal conformation over the spread and code signal are compared. As a pattern of comparison, the side-lobe elimination for adjacent-channel interference reduction, the process gain, and the BER versus signal to narrow-band interference ratio have been considered. Simulation results and prototype testing are given so as to illustrate the results obtained with this technique. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 360–364, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10462
    Microwave and Optical Technology Letters 07/2002; 34(5):360 - 364. · 0.59 Impact Factor
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    ABSTRACT: The design and experimental characterization of a wireless infrared fast frequency hopping spread spectrum (WIR-FFH-SS) system is presented. The use of spread spectrum techniques on wireless infrared indoor communications reduces the effect of interference present in the infrared channel. It also improves the system performance versus multipath propagation. The use of FH-SS techniques allow the use of code division multiple access (CDMA) strategies for sharing the channel. We have developed and tested a prototype with a bit rate of 1 Mb/s, but it can be easily raised to 4 Mb/s. We also present some results on a simplified synchronization structure for use with reduced-cost domestic equipment. These systems are suitable for different applications at low and medium rates
    IEEE Transactions on Consumer Electronics 03/2002; · 1.09 Impact Factor
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    ABSTRACT: RESUMEN En este trabajo se analizan los efectos de la aplicación de técnicas de conformación de pulsos a sistemas ópticos no guiados que utilizan una modulación de espectro ensanchado por secuencia directa. Las técnicas de conformación propuestas se basan en esquemas digitales sencillos y robustos y con un coste muy inferior al de otras soluciones que utilizan dispositivos DSP para el procesado de la señal.
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    ABSTRACT: In this paper, the application of synchronous Fast Frequency-Hopping techniques to indoor wireless optical communications is presented. These techniques will be used for CDMA scenarios in order to simplify the receiver structure and the co-user interference. INTRODUCCIÓN El modelo empleado en este artículo sería el de una habitación con un emisor principal, que además de encargarse de la sincronización, envíe una réplica del reloj de código pseudoaleatorio junto con señales capaces de facilitar la adquisición en los múltiples receptores. Estos receptores utilizarían estas señales para la sincronización en recepción además de para la generación de sus propios códigos. Este tipo de disposición sería la empleada en sistemas domóticos en el interior de viviendas para el control de electrodomésticos. Se trata pues de un entorno expuesto tanto a la propagación multitrayecto como al efecto de interferencias de banda estrecha como puede ser la iluminación artificial. Las ventajas que presentan este tipo de técnicas en cuanto a mejoras del comportamiento frente al efecto de la propagación multitrayectoria, así como la gran resistencia que ofrecen a las interferencias de banda estrecha, los hacen idóneos para este tipo de aplicaciones. El objetivo es el desarrollo de la comunicación de varios canales simultáneos de datos o incluso sonido o vídeo. El principal inconveniente de este tipo de sistemas de espectro ensanchado es, precisamente, la recuperación del sincronismo (Adquisición y Seguimiento [2]). En este trabajo se propone la inclusión de un piloto a la frecuencia de chip que facilita el sincronismo del sistema. Además, si este piloto consiste en una portadora a la frecuencia del reloj de chip ,modulada en fase por una señal con información sobre el principio y final de una secuencia de código completa, se simplifican en gran medida los trabajos de recuperación de sincronismo en el receptor. 1. DISEÑO DEL SISTEMA Se trata de un sistema de espectro ensanchado Fast Frequency Hopping con detección no coherente con una tasa de transmisión de 1Mbps. Y una de chip de 3Mbps.