Research On Power Control Technology In CDMA System

The power control is one of the key technologies in code division multiple access (CDMA) communication systems. It can weaken near-far effect of the uplink, combat multi-access interference, lower the user's emitted power, economize radio resource, and improve system capacity.Recently, as a theory of game in microeconomics, game theory has been commonly used to research in power control of CDMA communication systems, especially in uplink distributed power control. During the process of the playing, all the users try to maximize each other's validity by adapting emitted power, and bring it into Nash equilibrium finally.Based on the research in power control technology of CDMA cellular communication systems, this thesis deeply studied power control technology on game theory, analyzed various power control algorithms on game theory, and analyzed the advantages and disadvantages of their properties by simulation. And then a modified power control algorithm is putting forward. The main work and innovations in the dissertation are as follows:(1) The power control technology in 3G communication systems are studied firstly, And then the power control rule, power control methods of various mechanisms, and the power control technologies which are used in the three main standards of 3G communication are studied deeply. Various factors influencing power control are studied, and all conceivable angles in improving power control technology are analyzed.(2) Game theory, several basic elements of the game, and game classification are studied. And then this part researches in the equilibrium of different class games, mainly in dynamic game, which are prepared for the improved power control algorithm.(3) The traditional power control algorithms based on theory of game are researched in. The combining mechanism of game theory and power control technology, the principle and process of the algorithms are mainly analyzed, and then according to Zhiming Yin and Sarma Gunturi algorithms. This part establishes the system model, and designs validity function realizes the algorithms and receives the standard process of power equalization through iterations. Finally, the simulated results are depicted.(4) The best three traditional power control algorithms based on game theory—Koskie-Gajic, CR-NCPCG, and Zhao Chenglin—are studied. According to standard process, by establishing the system model, completing the iteration and simulating them, this part compares the performance of these three algorithms, preparing for the improvement.(5) In this part an improved power control algorithm based on game theory is put forward.①Starting with the principle of dynamic game, this part analyzes the improvement of dynamic game on power control technology, and puts forward the solution of dynamic game. That is, sub-game perfect Nash equilibrium is superior to Nash equilibrium of static game on power control. Not only is the superiority explained theoretically, but also can be proved from Zhiming Yin.②Based on CR-NCPCG algorithm, a modified algorithm is put forward. It designed the system model, the validity function, the algorithm's principle and power iterative process. The simulated results depicts that, the performance of modified algorithm is better than the foregoing power control algorithms based on static game. It meets in various properties, economizes power resources and speed up convergence rates of the power, meet the user's requirement for SIR, and finally increasing system capacity.