Research On Rake Receiver For WCDMA System

The RAKE receiver is one of the key techniques of code-division multiple-access(CDMA) spreading spectrum communication. It has many advantages, which areoptimum combination of multi-path in the time domain, better suppressing multi-pathfading and MAI. The thesis studies on the acquisition of spreading code,Signal-to-Noise Rate estimation, channel estimation, and space-time RAKE receivingtechnologies applying on RAKE receiver for wide-band code-division multiple-access(WCDMA) system.At the very beginning,this thesis focuses on the technology about Diversity Reception and describes a type of implementing method for the RAKE receiver from the theory. Next some researches on the Physical Layer of WCDMA have been made and also gives the architecture of the WCDMA RAKE receiver.Based on the research on methods of removing of the effects of Doppler frequency offset for spreading code acquisition, on the basis Algorithm of Tradition Spreading Code Acquisition, this paper brings up the Algorithm of Differential Correlation Spreading Code Acquisition, and some comparisons between the two Algorithms have been give.The SNR estimation is the key part of multi-path searching, code tracking and power control for the CDMA system. The pilot symbol-assisted SNR estimation and an algorithm for blind SNR estimation based in high-order moments have been discussed, also the results of computer simulation show some comparisons among the Algorithms.The channel estimation should be completed before multi-path combined for RAKE receivers. It is the guarantee for correct multi-path combine. Based on the research of the pilots aided channel estimation and multi-slot weighted average channel estimation, channel estimation based on Doppler frequency estimation for WCDMA systems is proposed. Simulation results show that the channel parameters can be accurately estimated and system performance is consequently improved.