The Algorithm Of Distributed Power Control Based On SIR Balance

CDMA technology is the main technology in the third generation mobile communication systems. It uses different spreading spectrum code words to distinguish users, which requires the spreading spectrum code has a strong correlation. But, in fact the spreading spectrum code can’t guarantee fully orthogonal, so the interference between users can not completely disappear, so that the CDMA system is an interference limited system. At the same time the user who is near the base station has a high power and the user who is far from the base station has a low power, so the near use will make a great interference to the far one. That is the near-far effect in the CDMA system. Power control is the key technology to rid the near-far effect and multi-access interference, so it is worth us to do further research. This paper mainly studies and analysis the power control algorithm based on SIR balancing in CDMA system.Firstly, This paper introduces the CDMA system and the traditional power control algorithm using in it. And a simulation study is made about the classical algorithm:DPC(Distributed Power Control), FDPC(Fully Distributed Power Control), PPC(Parameter Power Control), and finding that the power floated large in the iterative process, so that there is a great waste in the power resources, what’s more, the algorithms converge slowly. With the proposing of non-cooperative power control game, using game theory to solve the power control problem become another development direction of the power control algorithm. After the study of NPG and NPGP algorithm proposed by David Goodman and so on, we find that the algorithms’convergence power is large and it is unfair to the far users.Secondly, to reduce the shortcomings of the above algorithms, this paper considers the interference between users and the SINR error to give a improved cost function. And we proved that the algorithm with the new cost function has a uniqueness NASH equilibrium point. The simulation shows that the algorithm has been greatly improved in fairness and the convergence rate is faster than before, the convergence power is also reduced.Finally, with the rapid development of multimedia data services, the uses’QoS can’t be met by only using power control technology. However, the rate control technology is also an important technology to the system. So to join the rate control with the improved algorithm is considered by us, and we also give the performance of the new algorithm through the simulation.