The Research Of Transmit Diversity And Space-Time Codes In WCDMA

With the fast development of mobile communications and emerging services,the demands for the limited frequency resource are booming. To develop highly efficient coding,modulation and signal processing technologies is becoming the most necessary measure to realize these demands. The newly developing transmit diversity and space-time codes are just one of the most important schemes to improve wireless spectrum efficiency.This thesis focuses on transmit diversity and space-time coding techniques and their implements to the 3rd generation (3G) mobile communication systems especially in WCDMA. The main contents are as follow:Chapter 1 is an introduction of the application background of transmit diversity and 3G standards,and also presents the proposed transmit diversity schemes in WCDMA and cdma2000 briefly.Chapter 2 describes the characteristics of wireless channel,presents vector channel model for wideband CDMA systems,and emphasizes on the characteristics of indoor wireless channel.Chapter 3 presents the primary idea of transmit diversity first,then its system structure and mammetical model in details. The history of transmit diversity technique and general categories are reviewed. Finally,the concept of space-time codes and encoding design criteria are discussed here.Chapter 4 describles space-time block codes thoroughly. First we introduce it by presenting the classic 2Tx scheme proposed by Alamouti. Then the orthognal designes for space-time block codes are explored,the detailed analysis of the performance is presented. The link level simulations are performed in the last part.Chapter 5 describes the principles of closed-loop transmit diversity firstly. The analysis of the performance and its comparison to Space Time Transmit Diversity (STTD) are presented in this chapter. The link level simulations are performed. Finally we discuss the effects of feedback delay and feedback error on the performance.In Chapter 6,we presents a novel transmit diversity scheme - Space-Time Variable Correlation (STVC). Firstly,multiple-antenna transmission system is introduced,and then theAbstractprinciples and mathematical model for STVC is presented. The theoretical and simulation performance of STVC are given here. Also some further key application problems are discussed.Chapter 7 introduces the other two space-time codes besides Space-Time Block Codes -Space-Time Trellis Codes and Space-Time Layered Codes.In Chapter 8,the research work is summarized;the existing problems are pointed out. In the meanwhile,the developments of transmit diversity and space-time coding techniques in the future are prospected.