Studies On The Resource Allocation Optimal Algorithms For CDMA-based Wideband Access System

The next-generation mobile communication systems are expected to provide wideband transmission for mobiles and support multiple services. In order to make the most of the wireless resources to guarantee the quality of service, optimal resource allocations are needed. Due to the fading and time varing characteristics of the wireless channel, it is very troublesome to guarantee the transmission quality in wireless resource allocation. In this dissertation, we investigate in depth the optimal allocation of the various system resources including subchannel, power and transmission rate.First, a multicarrier DS-CDMA system model for wideband access is proposed, according to the characteristic of wireless channels, the subchannel allocation is investigated in forward links of the multicarrier DS-CDMA system. Based on the criterion of maximizing the total average signal to interference plus noise ratio (SINR), the optimal subchannel allocation strategy is obtained in theory when random signature sequences are used. For its implementation, an iterative algorithm is proposed, which is similar to the water filling principle. By using the proposed algorithm, we obtain significant improvement on the performance of the system, and the transmission quality can be guaranteed. On the other hand, the information about the allocation result is required at the mobile for data receiving. In order to make the mobile know its subchannel allocation result, a blind maximum-likelihood subchannel detection algorithm is proposed, which can improve the system efficiency and has been proved to be feasible in practice. Secondly, we present a new transmit diversity scheme with adaptive power allocation in which two antennas are employed at the transmitter, and the effect of the channel estimation error on its performance is also analyzed. Theoretical analysis and simulation results indicate that the new scheme has a considerable performance gain and is robust to the estimate bias of channel fading parameters.Finally, to support multiple services, an adaptive rate allocation scheme associated with GPS aided power control is proposed for the data traffic through fading channels in the DS-CDMA system. The performances of the system over different channels are investigated. It has been shown that the proposed scheme can support multiple rate transmission and is very robust to the offset of the power control.In a word, the resource allocation algorithms proposed in this dissertation are very helpful in the improvements of the performance, capacity and stability of the system.