The Research On Power Control Technique In TD-SCDMA System

Power Control is one of the keys technologies of cellular mobile communication. In the process of communication, mobile and base station should both adjust the transmission power real-time and dynamic, in order to improve system performance and reduce the co-interferences between users. TD-SCDMA (Time-Division Synchronous Code Division Multiple Access) is the homemade 3G standard in China and has accepted by International Telecommunication Union. Because of the TDD (Time Division Dual) modes, it uses the same carrier frequency in both uplink and downlink, this makes synchronization and the relational interference has become the main problem of the system. Due to the"near-far effect", the capacity of system is limited by the interference between mobile and base station. Based on the estimation of received signal strength and signal-to-interference ratio, changing transmit power to compensate the path loss and fading in wireless channel, accordingly keeping QoS. How to solve the interference problem effectively is the key problem to commercialize this system, this makes power control particularly important.In this paper, power control technique that adapted to TD-SCDMA system has been investigated. A brief introduction of the development, characteristic and key technologies of TD-SCDMA system, and a description of the research background of power control in CDMA system and the research status and research significance in this paper. A brief introduction of the basic method for power control, a description of power control techniques adapted to TD-SCDMA system.A improved based on SIR (Signal Interference Ratio) measure closed-loop second-order distributed power control algorithm is suggested and a general form is giving at the same time. Applying iterative method for power updating, this algorithm uses both current power level and previous power level to adjust transmission power. Through the analyses of simulation and computational experiments that carried out, we has found that in same spreading condition, the proposed power control algorithm has faster convergence and better system capacity.An Optimization of adaptive power control and multi-user detection joint algorithm is described, this used the multi-user detection technology of TD-SCDMA system. After the analyses of simulation that carried out, a significant improvement can be found, when comparing with based on SIR balance power control and traditional ZF-BLE (Zero Forcing Block Linear Equalizer) multi-user detection power control. It can effectively reduce the system transmit power. According to TD-SCDMA system rarely uses multi-user detection alone, an analysis and discussion of the effect on the power control algorithm combining smart antenna technology.