Power Control In Cdma Network And Spread Spectrum Synchronization Method In The Research And Implementation

CDMA has been the high-technological communication means in moderm information times.The synchronization technology and power control are the most common-use techonolgies in CDMA.Whether the system works reliably or not sensibly depends on the performance of the synchronization and Power control.As a result,its very important to discuss this problem.The synchronization technology include PN code acquisition,tracking,carrier recovery.I studied three PN acquisition schemes:serial acquisition scheme,matched filter technique, Partial Matched Filters combined with Fast Fourier Transfor (PMF-FFT).and presented structures,performance analysis.Espically,builded the simulation models by SIMULINK and presented the simulation results for PMF-FFT.Through thoroughly studying and contrasting I knew that PMF-FFT method can reduce two dimensional search of code phase-Doppler frequency to one dimensional.。In this paper, the effects of PMF-FFT on the performance of PN code acquisition are discussed.The relationshiop between conherent combining loss,PMF size and Doppler frequency shift is derived.Simulation results shouw that the PMF-FFT estimate the Doppler frequency shift whil acquire the PN code.Power Control is key technique in CDMA systems.It can combat near-far effect,reduce multiple acces interference and improve the system capacity.A power control scheme for the downlink in CDMA systems is proposed in this paper. Five downlink power control algorithms have been studied and evaluate in this work.The Modified Adaptive Step SIR-based Power control(M-ASPC) has been proposed. It has been shown that M-ASPC mitigate oscillations observed at low outage probabilities and have rapidly convergence.so it is the optimal power control scheme.Finally, introduced the hardware implementation platform.The designs for modules written by VDHL language and simulation results are given through parts of the core modules.