Researcher On Power Control Algorithms For 3G Communication And The Engineering Realization

Power control is the key part of the wireless communication, as well as the important strategy in CDMA system, which not only adjusts transmit power of the mobile station and base station but also compensates channel fading and counteracts near-far effect. Finally maintain the high-quality communication between users.Researches are done throughout the world as well as novel approaches are being developed and conducted, the issue of power control is very important in maximizing the capacity of a CDMA system and ensuring a good quality of reception. There will always be limitations in many users a BS will be able to handle simultaneously. Due to the channel fade and the different distance between Base Stations, stronger signals may cause too much interference and block out weaker ones. Therefore, in an optimal power control scheme for a CDMA system all mobile stations (MS's) signals should arrive to the base station at equal power. Commonly used power control schemes utilizes the Signal to Interference Ratio (SIR) to design a Power Control Command (PCC) to adjust the transmit power of the MS. A significant problem is the slow SIR recovery due to deep channel fades. This paper based on Linear Quadratic Gaussian (LQG) control and Kalman filtering for channel prediction, this method designs the PCC based on the coming channel state instead of the current. This optimizes the PCC for the channel state where transmission occurs, and simulations show its advantage. Besides the qualified algorithm, some wireless traits also require a stable gain to ensure the output equal to the expected power. However, the mechanical device which constitute the carrier channel will fluctuate greatly due to the difference between batch, temperature or frequency. In the part of engineering relization, the frame of the stable loop circuit is offered, and its feasibility is provided as well.