Research On Key Technology Of Downlink Based On WCDMA Systems Of Ground And Satellite

Currently, WCDMA technology has become a widely used and standardized protocol. As a commercial communication technology, WCDMA technology is developing rapidly and quickly occupied the global market; as a military communications technology, WCDMA systems for satellite communications systems meet the US military worldwide communications capabilities.This topic is WCDMA downlink receiver simulation and design of terrestrial and satellite systems. Key technology of the WCDMA downlink receiver system is primarily synchronization module design, that cell search synchronization between a mobile station and a base station when a mobile station is powered on, and synchronization and diversity of the RAKE receiver when a mobile station receive and modulate the signal.First, we study the WCDMA physical layer protocol standards. The structure and application of transport channel and physical channel in standard protocol about the downlink is described in detail. Spread spectrum modulation techniques associated with the physical channel and coding and multiplexing techniques associated transmission channel are described and analyzed.Secondly, we study wireless channels and physical channels of the terrestrial and satellite systems. Multipath propagation effects, the Doppler effect and small-scale wireless propagation channel fading model are analyzed. The parameters and WCDMA standard of terrestrial systems and satellite systems about the physical channel were compared.Again, this article describes procedure and principle of WCDMA cell search in the terrestrial and satellite systems. Relevant preambles of cell search were introduced, and synchronous analysis of the three-step cell search algorithm is described in detail. We describe matched filtering process of implementation in slot synchronization of cell search in the first step, the fast Hadamard transform(FHT) about the process of frame synchronization algorithm compared with the direct filtering method in the second step, and the threshold algorithm the cell synchronization process based on CFAR probability in the step. We establish WCDMA downlink simulation platform of a cell search in terrestrial and satellite systems, and analyze detection performance and acquisition performance of the cell search.Finally, this paper analyzes the principle and block diagram of downlink RAKE receiver in WCDMA terrestrial systems and satellite systems technology, and proposes applicable RAKE receiver scheme adapting land and satellite communications environment. Pilot modes, system models of terrestrial and satellite systems for a simple analysis are illustrated. The key technologies of the RAKE receiver are analyzed: multipath search, channel estimation and maximum ratio combining technology. Finally, the RAKE receiver parameters in terrestrial and satellite systems specific are described. Two receiver structures of different environmental parameters are given in terrestrial and satellite systems, and the performance of the two systems were analyzed and compared.