Browsing by Author "DOUDOU FATMA ZOHRA"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Acquisition adaptative série du code PN basée sur l'optimisation du seuil de détection dans des systèmes distribués CFAR pour les communications DS-CDMA
    (2016-11-03) DOUDOU FATMA ZOHRA; Encadreur: DJEBBARI ALI
    In the context of this dissertation initial synchronization (or code acquisition) of mobile communication system employing a serial search is studied when the receiver uses a multisensor data fusion in a multipath environment. Code synchronization means time synchronization of the used spreading code in the receiver. Code synchronization is an important task in mobile communication system (DS-CDMA) since no demodulation can only be operated after code acquisition. Indeed, this task consists in aligning the received code and the local code at the receiver, and is performed in two stages: initial synchronization or code acquisition and fine alignment or tracking. The aim of this thesis is to enhance the performance of the code acquisition process in a particular environment. For this purpose two adaptive acquisition schemes are proposed. Two adaptive acquisition schemes based on serial search are proposed using threshold optimization in multisensor data fusion systems for mobile communication in a frequency selective Rayleigh fading channel. Two distributed systems using adaptive detectors based on OS-CFAR (statistics ordered constant false alarm rate) and CMLD (censored mean level detector) are used. For threshold optimization, the Particle Swarm Optimization algorithm (PSO) with a linearly decreasing strategy is suggested, using two logical fusion rules to improve the serial search in a multipath environment. The acquisition and detection performances are investigated under different system parameters and channel condition, namely the number of distributed sensors, the size of the partial correlation window, the number of resolvable path and the effect of fading. The simulation results show the robustness of the distributed adaptive acquisition CMLD processor using the PSO algorithm over the scheme based on the OSCFAR. In addition, the advantage of proposed schemes over adaptive acquisition ones using one antenna is also investigated by simulation.