Research On The Channel Estimation Technology In WCDMA Systems

With the development of wireless communication technology, high-quality transmission becomes the focus of modern communication. Channel estimation is one of the most important techniques in WCDMA mobile communication systems. The channel estimation is the key part of coherent demodulation of RAKE receiver. Its performance has a direct effect on the BER performance of system. How to estimate channel parameters accurately to the best of one's abilities is a very important way to improve the system performance.The channel estimation techniques of WCDMA communication systems are discussed in some depth and broadness in this dissertation. It carries out a consolidate and comprehensive analysis of the channel estimation error and possible methods to reduce the error. Especially it presented an adaptive channel estimation scheme. The main content include:Firstly, the frame structure of physical channel concerned with channel estimation in WCDMA system is presented. The transmitter model, channel model and detailed receiver structure are also described. These are fundamentals of the channel estimation. Following that, the whole data demodulation process, the nature of channel estimation error and the system performance in multi-paths Rayleigh fading channel are deduced. Simultaneously we analyze how the power ratio of pilot channel to data channel affects system performance.Secondly, an adaptive LMS channel estimation algorithm is proposed on the basis of the traditional algorithms in this paper, and simulation results shows the superiority of the improved algorithm. Such a theory based on adaptive channel estimation algorithm could be applied to mobile station in a low-speed, high-speed and mixed-rate under various circumstances.Furthermore,this paper also proposes a new frame structure for the channel estimation algorithm and analyses its performance deeply in the fifth part. Compared with the performance of conventional frame structure, we can know that this new algorithm has the larger advantages than before, to maintain the performance at a considerable circumstances and greatly enhances the utilization of bandwidth.Finally,many channel estimation methods are simulated and analyzed in the paper. Simulation results demonstrate that the adaptive schemes and new frame structure are very attractive.