Cell Search Algorithm For Wcdma Systems

WCDMA is one of the most competitive standards of 3rd generation mobile communication system. The technique of the synchronization is one of the keys of the communication system so much emphasis is laid on the design of the Cell Search algorithm. This paper is focused on the design and the implementation of the Cell Search algorithm in WCDMA. We divide the paper into five chapters.Chapter 2 gives a general description of technique specifications of physical layer in WCDMA We both describe the content in WCDMA physical layer and the content that is connected to it so that we can get a more clear vision about the physical layer of in WCDMA Chapter 3 describes the characteristics of the mobile channels and the techniques to simulate them. Jakes' method and the revised method are carefully considered in this chapter. Chapter 4 describes our research work on the Cell Search algorithm in WCDMA. To be more clear we divide the chapter into 2 parts according to the 2 problems we will encounter. The first is how to get the scram code and time quickly. The second is how to estimate the large frequency error. In our research work we draw the following 6 conclusions.We can get better performance if we use different length in chips for accumulation for different frequency error. The false alarm probability should be very small for the algorithm. We derive an expression to calculate it.Coherent combination can get better performance in the step2 algorithm in low Ior/Ioc however Coherent combination can not get much gain if Ior/Ioc is more than -3db. Soft decoding can achieve better performance. In realistic channels the average cell search time is no less than 100ms in any algorithm if we use the pipelined cell search process.High time spread will degrade the performance of the algorithm however the dopplor spread will benefit the performance. When talking about the second question we use the Newton iteration method and differential frequency estimation method to tackle it.Chapter 5 describes the method to implement the algorithm. We will lay great emphasis on the problems we will encounter and how to solve them. What's more we describe the soft decoding method more specifically.