Study On The Model With Multivariates Of Downlink Beamforming, Power Control And Resource Allocation For Multi-rate CDMA System

Wide-band direct-sequence code-division multiple-access (DS-CDMA) is a promising radio access technique for third-generation mobile communication systems due to its flexibility to support a variety of voice, video, and data services. These services will require higher data rates and higher received signal power levels, thus creating larger interference between users. The interference levels have to be reduced effectively in order to obtain high system capacity. Spatial-division multiple access (SDMA), by which a plurality of antenna elements are equipped at the base station in order to receive and transmit data information from and to the desired user, has been proposed as an effective technique to suppress interferences. The main operations in SDMA include uplink beamforming and downlink beamforming. Uplink beamforming consists of uplink beamforming weight generation, and uplink signal demultiplexing; downlink beamforming includes downlink beamforming weight generation and downlink signal multiplexing. Theoretically, in both links, the associated link channel responses are of critical importance in order to generate the relevant beamforming weights.Power control and data rate allocation are two fundamental techniques for providing reliable transmission over a time-varying channel. In very general terms, power control balances received powers of all users so that no user creates excessive interference to other users in the system. The aim of power control is to assign users with transmitter power levels so as to minimize the interference users create to each other while having a certain quality of service which is defined in terms of the signal to interference ratio (SIR). Even though power control is adopted in IS-95 and third generation systems, it was shown in some reference that adaptive rate allocation with constant transmission power provides larger system throughput than adaptive power control with constant data rate.On the other hand, joint beamforming and power control can further increase uplink capacity of DS-CDMA systems. At present, power-based power control scheme and maximal-ratio combining (MRC) beamforming criterion are developed; while signal-to-interference ratio (SIR)-based power control and minimum mean-sequence-error (MMSE) beamforming criterion are proposed. Both methods can dramatically improve the whole system capacity as compared with single antenna case. In practice, it is also desirable to increase downlink capacity in order to improve the whole system capacity. In particular, downlink performance is even more important for the next-generation communication systems in which wireless internet, video-on-demand, and multimedia services are to be required.According to the above content, the problem of joint downlink beamforming, power control and dynamic data rate allocation for multi-rate DS-CDMA mobile radio is formulated in Chapter 3. Mathematical analysis and computer simulations are given to study how the data rate allocation affects the total transmitted power, and the relation of soft target SIR thresholds and data rate allocation. We draw the conclusion that user has to sacrifice its target SIR threshold to obtain more resource from the system. With that conclusion, a new optimal data rate allocation algorithm is proposed by using all users' soft target SIR thresholds and spatial correlation information. Then this rate allocation algorithm is introduced to V-UBPCT algorithm, combined with downlink beamforming and power control to present a modified V-UBPCT algorithm. For simplicity, the steps and mathematical formation of IVPW algorithm are proposed. Computer simulation results show that the optimal data rate allocation approach is superior to the scheme with uniform rate allocation, and the higher rate user would affect the outage of the lower rate user. Thus, it is necessary to limit the number of the higher rate users. Therefore, the new approach is well applicable in future wireless internet services; and in fact, it provides the base station an efficient method of h...