Wideband Cdma Mobile Communications, High-performance Receiver And Power Control Technology,

Due to the advantages of high capacity, interference resistance, soft handover, convenience of access, wideband code-division multiple-access (CDMA) has become main standard of the third generation mobile communication systems. Some key techniques are studied in this dissertation that consists of several parts as follows.In this dissertation, the mathematical model of mobile fading channel is analyzed, the corresponding structure for realization is given the channel impulse response and Doppler power spectrum are described in detail. In terms of the channel characteristic parameters, the relation between them are disclosed, furthermore, the channel is classified according to the relation.Based on the deep study on the effects of averaging filter channel estimation and muti-slot weighted averaging(WMSA) on WCDMA link performance, a channel estimation method based on pilot with polynomial fitting is proposed for high mobile speed environment in this dissertation. Results show that link performance decreases as mobile speed increases, the optimal number of the slots in the processing window is equal to the polynomial order, the polynomial order should be increased as the mobile speed increases, and for a mobile speed of 3 to 250 km/h the polynomial of order 3 is a good trade-off between link performance and algorithm complexity. Results also show that WMSA is better under low mobile speed environment, while the proposed algorithm is obviously better than WMSA when mobile speed is higher than 100 km/h at a price of higher complexity. The link performance reached by using the proposed algorithm will be superior to those of linear interpolation and Gaussian interpolation.A serial multipath interference cancellation technique based on pilot is proposed in this dissertation. The analytical and simulation results show that this technique can improve the performance of RAKE receiver over multipath fading channel. The RAKE with SMPIC has simple structure without using other users?spreading waveforms or the correlation characteristics between different spreading waveforms. Especially, it is suitable for mobile terminal with constrained complexity, and for the application environment in which multiuser detection (MUD) technique is difficult to use.A link level power control algorithm based on SIR measurement and a balanced distributed power control (BDPC) algorithm at system level are proposed in this dissertation. Results show that SIR measurement using pilot symbols of control channel is effective. Due to the role ofIIcoding, interleaving and power control, for a certain bit error rate (BER), the required E1j[0 increases slowly as the channel fading increases. The optimal power control step depends on the Doppler frequency. Therefore, to obtain best link performance, the power control step should be changed dynamically as the change of the channel. When the transmission error probability is less than 1111, the error hardly affects the link performance. Compared to conventional distributed power control (DPC) algorithms, BDPC algorithm needs no global exchange information and can compute the normalization factors that are necessary to keep the transmitted power in reasonable dynamical range. Although fully DPC (FDPC) also needs no global exchange information, the transmitted power in FDPC will be decreased to zero due to the convergence. However, BDPC can keep the transmitted powering in reasonable dynamical range and doesn affect the speed of convergence; it can be applied in practice.