Uplink Power Control Algorithm Research In Wcdma System

WCDMA has become one of the three main standards of the third generation mobile communication technology. It adoptes many key techniques such as spreading, Rake receiver, soft handover, power control, high efficiency channel coding and so on. Among these techniques power control is the most important one and it is the key factor for system realization. Because WCDMA system is a self-interference system, interference between users will influence system capacity and system stability. Power control technique can gurantee the communication quality at the least transmit power. So it can reduce interference between users, improve system capacity, avoid system collapse and improve mobile's battery life.WCDMA system has adopted open loop power control and close loop power control techniques. Open loop power control can provide the initial transmit power during the connection between UE and NodeB. And close loop power control can adjust the transmit power quickly when the propagation environment changes.Firstly, open loop power control technique is introduced. It includes the methods that how to decide the initial transmit power and how to decide the power offset between the control channels and data channels.Secondly, inner loop power control (ILPC) algorithm is proposed. There are two main algorithms that ILPC usually adopts. SIR estimation plays a very important role in ILPC. Traditional SIR estimation algorithm is introduced and derivation is derived to prove that the traditional algorithm is biased. So the unbiased algorithm is proposed based on the traditional one.Lastly, outer loop power control (OLPC) algorithm is introduced. There are three facts that the traditional OLPC algorithm based on block error rate (BLER) can't accomplish well. SIRTarget convergence speed is not quite quick during these three situations: initial connection, from bad propagation environment to good propagation environment and windup. The better algorithms are proposed to improve SIRTarget convergence speed in these three imperfect sides. And improved algorithm can increase system capacity and reduce mobile transmit power.