Digital Beamforming in Wireless Communications
Digital Beamforming in Wireless Communications
Modeling of code acquisition process in CDMA networks-asynchronous systems
IEEE Journal on Selected Areas in Communications
Two-dimensional code acquisition in time and angular domains
IEEE Journal on Selected Areas in Communications
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In this paper we propose and study two methods for improving two-dimensionalcode acquisition performance in scenarios with nonuniform spatialdistributions of interference. The schemes exploit the fact that integrationtimes and threshold settings are adaptively set for each angular cellaccording to the level of spatial interference prevailing in that cell. Modelsfor the schemes are first developed. Closed-form mean acquisition times arethen computed to allow performance comparisons. Acquisition performance isanalytically evaluated for different spatial distributions of interference.A system with fixed integration time and a fixed threshold is used as areference. It is found that the adaptive integration time scheme is able tofully compensate for the loss of performance caused by the nonuniformdistribution of interference. Furthermore, the mean acquisition times can bereduced by a factor of as much as two, even in environments characterized bysevere distributions of interference, e.g., a high power peak of interferenceconfined to a given angular direction. The adaptive threshold method alsoperforms better than the reference case but provides moderate performancegains.