| With the rapid development of modern technologies, mobile communication systemis exerting more and more important effect. Nowadays the technologies of3G have beenapplied commercially, and the research for next-generation mobile communication, i.e.,beyond-3G (B3G) system is in the ascendant. B3G system will be an all-sided evolutionof access technologies, network architecture and system performance, thus the radioresource management (RRM) of B3G system has attracted lots of attention and becomea valuable research topic. The main challenges of mobile communication system lie inintrafrequency interference, intermodulation interference,“near-far” effect, and also themulti-path fading and shadowing introduced by the complex wireless propogationenvironments. The proper and effective power control algorithm can be implemented toreduce the transmitting power and thus improve system capacity while guaranteeingQoS to meet user’s requirements. From the viewpoint of system architecture, schemesand algorithms, this dissertation focuses on the research of power control technologies inCDMA-based and next-generation mobile systems.Firstly, this dissertation studies the service factor-based joint power controlalgorithm in fast fading environments. Several real-time and non-real-time services froma collection of IP data are provided by3G and next-generation mobile system, with theimportant statistical property of bursty transmission, so the interference in mobilesystem may fluctuate dramatically. The characteristics of burst-mode traffic can beutilized to make power control algorithm perform better. To combat against fast fadinggenerated by fast movement of mobile terminals, the method by increasing powercontrol rate to trace fast fading will introduce lots of signaling overhead. In our proposedjoint power control algorithm, the mobile terminal can adjust service activity factor toadapt to channel fading conditions, which can be predicted by the p-step linear predictormodel. The data packets are buffered firstly, and then transmitted in the periods ofshallow channel fading. The proposed algorithm can improve the tracking performance of power control, decrease the transmitting power level of mobile terminal, and thusreduce the co-channel interference within the cell. The system capacity is increased andQoS is improved as a result. The adjustments of transimitting power of mobile terminalsare computed based on the common network resources, and the goal to allow mobileterminals to share network resources equally so as to speed up the convergence of powercontrol algorithm can be realized.Secondly, this dissertation analyzes the multi-service property in mobile system,and studies the joint power and rate control algorithm in multi-service system. Becausedifferent services have different requirements of transmitting rate, bit error rate (BER)and latency time, inappropriate rate allocation will waste the wireless resources ordegrade the QoS. This dissertation proposes the maximum throughput-based joint powerand rate control algorithm from the viewpoint of mathematics analysis. It takes theservice priority into account and allocates different rates to non-real-time services toguarantee the QoS and the minimum transmitting power of non-real-time services, andthen the saved power can be allocated to high-priority services, such as real-time ones.Consequently, the approximately maximum throughput can be achieved. Compared withthe strategy of fixed transmitting power, the algorithm can efficiently reduce thetransimitting power and multiple access interference (MAI), thus increase the systemcapacity and spectrum efficiency. When the traffic load in multi-service system is high,the proposed joint power and rate control algorithm will guarantee the total systemperformance at the cost of decreasing the QoS of low-priority services. The resourceutilization can be improved by designating different users’ transmitting rates andSIR-based power allocation. For the subsequent research, this dissertation analyzes themaximum throughput by way of mathematics analysis, and discusses the impact of ratecontrol on the throughput of multi-service mobile system.The MIMO-OFDM technology is accepted widely as one of the most promisingphysical-layer schemes for B3G system in the future. Transimitting antenna subsetselction can be thought of as a special technique of adaptive power allocation. In thisdissertation, the adaptive modulation is applied to MIMO system, and a modifiedantenna subset selction algorithm is presented with the principle of channel capacityoptimization. By combining with the adaptive bit and power allocation scheme forMIMO-OFDM system, a new adaptive bit and power allocation algorithm based on antenna subset selction is proposed in this dissertation, which can dynamically select theoptimal subset of transimitting antennas. As for OFDM system, different subchannelshave different transmitting capacity due to different fading, so efficient resourceallocation scheme is necessary to make the most of channel resources. In thisdissertation, Lagrangian multiplier method is utilized to carry out bit and powerallocation, and the remaining power is then allocated by greedy principle to get the finalresult of bit and power allocation. Compared with the existent Hughes-Hartogsalgorithm, the simulation results show that our proposed adaptive power allocationalgorithm can enhance system capacity and reduce bit error rate, and help to improve theMIMO-OFDM system. The main idea is that, antenna subset selction algorithm canselect the special subset which will contribute to the channel capacity most for all. Theproposed algorithm can achieve the good tradeoff between calculation complexity andsystem performance. |
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