Design And Simulation Of Power Control Schemes Based On Multi-objective Optimization

With the rapid development and in-depth application of wireless communications, the needs of mobile communications are growing fast. Nowadays, the3G communication systems which are based on the technology of code division multiple access (CDMA) have been widely applied, but deep research on key technologies in CDMA systems need to be continued. In CDMA systems, near and far effect, multi-access interference and shading effect impact the quality of communications seriously, and then result in the decrease of system capacity. As one of the key technologies in CDMA systems, power control can cope with these problems effectively. The application of power control technologies, on one hand weakens the influence of various fading in communication environment because of power compensation, and on the other hand, terminals’transmit powers should be at the lowest levels which can satisfy the SINR requirements for different users. In this way, the users can reduce the battery power consumption, and at the same time decrease the interference to other users, so that the system capacity could be improved and the terminals’batteries could last for much more time.This thesis studies the power control schemes in CDMA systems, and proposes a scheme which solves the power control problems by combining the multi-objective technology with genetic algorithm after the detailed analysis on the existing research results. This thesis considers CDMA systems only, firstly aiming at minimize the power consumption when quality of service (QoS) must be guaranteed. It proposes a new power control algorithm to realize the optimal allocation of power in the system. Users’ transmit powers are coordinated according to the users’ locations and QoS requirements. Then after the research on the power control problems in multi-service CDMA systems, a joint power control algorithm called MMGPC is proposed also using multi-objective technology and the genetic algorithm. This algorithm is aiming at the coordination of three contradictory objectives, which are data rate guarantee for different services, outage probability minimization and power consumption minimization.In order to prove the feasibility and effectiveness of the two proposed algorithms, this thesis performs simulations by Matlab. The results show that the two proposed algorithms based on the multi-objective technology and the genetic algorithm can lower the total transmit power consumption a lot and decrease outage probability compared with the traditional power control algorithms, thus more users can access the system, that is to say the capacity of the system is increased.