| Technology-driven, needs traction and market-orientation are the main driving forces to promote the development of new technologies. cdma2000 is one of the three mainstreams in 3G, and cdma2000 1x EV-DO is mainly responsible for high-speed data transmission of the cdma2000 1x system. The rate control mechanism is a key technology of cdma2000 1x EV-DO. This mechanism greatly improves system stability and reverse capacity which can meet the demands for users'data services. At present, the 1x EV-DO technology has begun to enter the commercial application stage, and there are still three main problems in the prior literatures on the reverse link rate control algorithm. Firstly, there is not an applicable theory analysis model for rate control algorithms, so designing a new algorithm is of great difficulty. Secondly, the flexibility of the existing algorithms is not too high to adapt the fluctuation of the system load. Thirdly, the allocation of channel resources is not reasonable which affects the system efficiency.Based on these problems, this dissertation would focus the research on the reverse link rate control algorithms in 1x EV-DO. Based on the analysis of the rate control mechanism and existing algorithms, this dissertation presents a reverse link rate closed-loop control analyzing model, by which the research and rate control algorithm's design could be carried out. And then, two modified rate control algorithms are proposed in the framework of the analysis model. Main work and contributions of this dissertation are outlined as follows:1. A closed-loop control model was proposed to analyze the rate control mechanism effectively and guide the design of the optimal rate control strategy. By using the discrete time control theory, the rate control blocks for both the base station and the terminals have been designed to construct the closed-loop control model. Thereafter, the reasonable range of open-loop transfer function gain to maintain the system stability was got by the root locus design. System stability and response time were validated by configuring different weighting factors in terminals'rate control blocks, and then an optimal rate control strategy was obtained. This analysis model provided a highly efficient and flexible model for the rate control algorithms'design, ananlysis and verification.2. A probability adaptive rate control algorithm was proposed to solve the poor flexibility of the rate transition probability in the traditional algorithm. This algorithm introduced the sliding windows mechanism, and according to the statistical states of reverse activity bits, the terminals could change the rate transition probability flexibly to adapt the fluctuation of the system load more accurately. Simulation results showed that this algorithm not only evidently improved the performance of system throughput and outage probability, but also made a better trade-off between them.3. A rate control algorithm based on the channel quality for the reverse link was proposed to solve the unreasonable allocation of channel resources which affected the system efficiency. In this algorithm, the active terminals were classified by the pilot power, and the weighting factors were introduced to allocate the T2P flows flexibly. In this case, the terminals with good reverse channel quality are able to get more data transmission space, while the terminals with poor reverse channel quality can avoid the system instability which is caused by the increasing transmission power. Simulation results showed that the new algorithm had higher system throughput, lower ATs'transmission power and system load than the existing algorithms. |
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