Joint Power Control In Cdma Communication Systems

In CDMA systems, users create interference to each other to the extent of the correlation between their codes and the ratio of their received powers. Consequently, near-far effects in which strong users with higher received powers can overwhelm the communication quality of the weak users with lower received powers must be mitigated.Power control and multiuser detection are two key technique to cope with the multiple access interference and near-far effect in CDMA mobile cellular communication systems, Power control is a resource allocation technique that balances the received powers of the users so that no one user creates excessive interference. Even when perfect power control is applied, the interference can be further suppressed by multiuser detection. Similarly, even when optimal linear multiuser receivers are used to maximize the signal to interference ratio, power control can be used to further diminish the near-far effect.In this paper, we survey the research on combined power control and multiuser detection in CDMA system. First all, some basic concept reviewed. Then the ideal combined power control and multiuser detection is introduced and take a new joint power control algorithm method based on cost function. Tests show that on condition that the total transmitted power in the CDMA system is given, user can obtain a high SIR and the capacity of the system can be also improved with the proposed algorithm.