| IMT-Advanced has higher data rate, wider range of services and applications, and higher quality of mobile services compared to conventional systems. In order to meet the requirements of IMT-Advanced system, a series of key technologies have been proposed to enhance the spectrum efficiency and system performance, including multiple antennas, spectrum aggregation, multiple access, relay and so on. To verify whether the IMT-Advanced candidate technologies meet the ITU minimum requirements, it is an urgent need to have a unified, scientific and effective evaluation method, and also a public simulation platform to simulate a variety of technologies for comparison and verification, which provides technical support for the third-party assessment.This thesis is supported by National Key Project under Grant "Simulation platforms of IMT-Advanced key technologies". The main work of this thesis includes the design and implementation of IMT-Advanced downlink multi-user system-level simulation platform and specific system performance assessment.First, the IMT-Advanced evaluation methodology and the related assessment process is studied, the framework design of the multi-user system-level simulation platform and function module division was completed with detailed implementation description of each module. Moreover,3GPP LTE-A is taken for example to show the steps of consistency calibration procedure of the simulation platform.Second, the complexity of IMT-Advanced system simulation is analyzed. The analysis results indicate that the storage and reading harddisc file data caused by of a large number of simulation links occupies a large amount of simulation time, therefore simulation efficiency is a bottleneck constraining the evaluation of key technologies. For this problem, a series of optimization and improvement strategies are presented from the two aspects of the memory mechanism and simulation models. Comparison result of performance before and after the optimization show that efficient memory management mechanism and a reasonable simulation model simplification can increase the simulation speed of about 10 times.Then the assessment differences of the TDD and FDD system are analyzed from the aspects of frame structure, spectrum deployment, CSI feedback, HARQ mechanism and control channel overhead. The pre-coding techniques, CSI measurement and feedback, and HARQ process of TD-LTE-Advanced system are studied. The performance of TD-LTE-Advanced system with multi-antenna technology is evaluated under the four main scenarios of ITU and comparative analysis with the LTE Release 8 is given. Assessment results indicate that SU-MIMO with 4×2 antenna configuration could satisfy ITU needs in the scenarios of InH and RMa, but not in the scenarios of UMi and UMa. The MU-MIMO with 4×2 and 8×2 antenna configuration could meet the needs of all the scenarios, and its performance can be further improved by optimizing pre-coding and user grouping schemes. Therefore, it is necessary to introduce more advanced multi-antenna technology to further improve performance in urban environments, so as to meet the system needs in system capacity, coverage and other aspects.Finally, a summary of this thesis is given, pointing out the further research directions in system evaluation, such as the new simulation modeling and evaluation methods required by heterogeneous network convergence and 60GHz short-range wireless communications for future mobile communication technologies. |
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