TD-HSDPA Synchronization, Adaptive Techniques And Their Optimization

With the development of the mobile communications and internet networks, there are more and more packet data services requiring high throughput and low delay. In order to satisfy these demands, HSDPA (High Speed Downlink Packet Access) technology is selected for TD-SCDMA to provide higher data transmission rate and lower transmission delay. Due to the employment of AMC (Adaptive Modulation and Coding), HARQ (Hybrid Automatic Repeat reQuest), high order modulation scheme, HSDPA can quickly adapt to the channel situation to get lager system capacity and cell data throughput. Thus, this thesis is mainly devoted to the design and implementation of TD-HSDPA vector signal software, with the emphasis on the chip synchronization, AMC, HARQ and their optimization.Firstly, this thesis analyzes in detail the TD-HSDPA wireless interface protocols and 3GPP specification, in particular, the HSDPA frame structure, channel coding, multiplexing, modulating, spreading, scrambling and filtering. Based on the overall software design and system model, the TD-HSDPA function library of signal generator software has been developed using Visual Studio 2005. Test results show that the software can be used to generate TD-HSDPA baseband signals for real systems.At TD-SCDMA receiver, chip synchronization ensures the accuracy of other receiver processing. So in the thesis, the BER effects of timing offset are computed and the acceptable range in the real systems is simulated. Then, a chip timing estimation and correction algorithm is proposed. The new algorithm can effectively implement the timing offset estimation and correction by sampling and filter weighting adjustment. Simulation results show that the proposed method has the advantages of low complexity and simple implementation for good timing synchronization performance in TD-SCDMA system under AWGN channel.Subsequently, the adaptive techniques and their optimization are investigated. Based on the analysis of the pilot-assisted AMC schemes, the throughput and FER of several adjustment algorithms are studied and compared. Simulation results show that although the throughput is slightly lower, considering better FER, the overall performance of the improved distributive adjustment algorithms remains optimal.Finally, the thesis shows how to select the limited redundancy versions to achieve the best performance, and introduces an optimized scheduling algorithm on the selection of HARQ function, together with simulation results.