| This paper includes six chapters. These sections from chapter two to chapter five are the most important parts, which are main work.In chapter one, the origin and definition of 3G are introduced firstly. Then, the main aim of air interface of IMT-2000 is given. According to the main aim, the characteristics of 3G are analyzed. At present, WCDMA, cdma2000 and TD-SCDMA have held the leading position in all of air interface standards adopted by ITU. The key technologies of radio resource management in 3G are presented in the second section of this chapter, which are handoff, power control, call admission control, load control and packet scheduling. The research significance and the structure arrangement of this paper are given in the end of this chapter.In chapter two, the author firstly discusses the function and significance of load control, and analyzes the research situation of load control at present. Then, a dynamic distribution scheme of traffic load in WCDMA system proposed by author is presented in detail. The main idea of this scheme is that the central base station periodically adjusts the power of pilot signal in down link according to the total interference suffered in uplink so that mobile station is able to hand off between central cell and surrounding cells smoothly according to intensity of the pilot signal from each base stations. The scheme realizes the dynamic distribution of traffic load. The results of simulation indicate that this scheme can get good performance compared the scheme in which the power of pilot signal is invariable. At the same time, system model, simulation parameters and statistical graphs are given in this chapter.Hierarchical cell structure is the effective method in the future mobile communication system, which can increase the system capacity. In chapter three, combining the characteristic of hierarchical cell structure the author proposes a call admission control policy applied in hierarchical cell structure CDMA system. System timely deals with the call requests according to the interference level of local cell and adjacent cells, which can ensure the communication quality of dialing users. Two typical services including voice and data are considered. The priority of handoff call is higher than that of new call. The result of computer simulation indicates that this policy reduces effectively the handoff block probability.The key parameters in soft handoff control are discussed and analyzed in the fourth chapter. In the soft handoff control policy adopted by WCDMA system, T_ADD, T_DROP and T_REPLACE take very role. In this chapter, the relationship between the three key parameters and block probability and dropping probability is discussed. At the same time, calculate is completed by the radio system design tool Cellular Engineering 4.0 from Lucent Co. Velocity estimation of mobile stations is analyzed in the fifth chapter. Estimating the movement velocity of mobile station has very important significance in the future mobile communication network. In this chapter, the author introduces the main methods of velocity estimation and analyzes the advantages and shortcomings of them. In the end of this chapter, the problems of velocity estimation faced in CDMA system are discussed.The sixth chapter is the last section of this paper. The author summarizes the total research work in this chapter and describes the beautiful future of human brought out by the development of mobile communication technology. |
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