Code acquisition in DS-CDMA systems optimization and DSP implementation.

摘要

Code synchronisation is as an attempt to synchronise the receiver clock to the transmitter clock. The process of acquiring the timing information of the transmitted spread spectrum signal is essential to the implementation of any form of spread spectrum technique. The overall system performance is dictated by the code acquisition subsystem since other subsystems rely on a successful code Acquisition.; In CDMA systems, the signal to interference plus noise ratio at the receiver depends on the chip pulse shape used in spreading the user signals. The performance of the acquisition system was extended using the Improved Gaussian approximation which gives a better account of the effect of interference on the CDMA system.; The threshold should be set above the noise level, thus an estimate of this figure is required by the detector. Under stable channel conditions the threshold can be fixed but in dynamic channel conditions, where interference is present, adaptive threshold schemes should be used. It is necessary to design an acquisition threshold with its value being set according the effective SINR. A modified threshold setting system is proposed for the Hybrid search scheme. A modified threshold setting scheme was proposed for the Hybrid Search scheme.; Implementation of the algorithms was also carried out on a Texas TMS320C6713.