Performance Of PDSCH Channel And HARQ For Broadband Wireless Trunking System

In recent years, in order to meet efficient user interaction of information. Broadband trunking system is becoming the inevitable choice. Long Term Evolution system is a new generation of broadband multimedia cluster system, which is based on Time Division Long Term Evolution technology. Therefore, our country makes the research on broadband trunking system based on TD-LTE technology as the primary work, and devotes a lot of funding support.Physical Downlink Shared Channel is one of the most important data transmission channel in TD-LTE. This thesis mainly introduces the PDSCH design steps which we are responsible for in the projects, including the design of the PDSCH transmitter and receiver. In addition, in order to verify the performance of the MATLAB algorithms about PDSCH, we use the communication simulation software SYSTEMVUE provided by the Agilent Technologies to compare the related performance. The complete PDSCH link is both built in software SYSTEMVUE and MATLAB. The final simulation results show that the PDSCH transmitter’s function of each module are identical in the two simulation software. At the same time, the performance of the receiver is also compared and the relevant performance curve is made. The final results show that, the designed algorithms, with a high degree of accuracy and reliability, will lay the important foundation for the research project.On the other hand, the thesis mainly studies the Hybrid Automatic Repeat reQuest technology in the broadband wireless trucking system based on TD-LTE technology. The HARQ mechanism aims to realize very fast retransmission. So it plays a very important role in the modern communication system. The basic concepts and the related processes of HARQ technology in the TD-LTE system are explicitly introduced in this thesis. Among them, the research on the downlink HARQ technology and the HARQ general feedback schemes such as HARQ Bundling and HARQ Multiplexing are been researched. There is also room for improvement of the HARQ feedback schemes especially HARQ bundling technology in the throughput performance. So three kinds of improved feedback schemes are proposed based on rateless codes technology to make better performance.The first proposed scheme is based on SBDRC(Systematic Binary Deterministic Rateless Codes) technology, which introduces the system encoding and decoding processes in HARQ retransmission. Compared with the general HARQ feedback strategy, this scheme outperforms 0.5~0.6d B in the throughput performance. When lots of transmission packets are in error, this scheme has better performance than the other two. Because of the complex coding and decoding and the large matrix are involved, the improved scheme to reduce the complexity is proposed based on the first one. It doesn’t need to handle and store the large matrix, and greatly reduces the complexity. Compared with the traditional HARQ feedback strategy, this scheme has 0.4~0.5dB improvement in the throughput performance. At the same time, the third kind of innovate scheme is also proposed based on the second one. It further reduces the complexity by using mathematical statistical properties. And compared with the traditional HARQ feedback strategy, it enhances about 0.5dB in the throughput performance. Therefore, when there is a small amounts of error packets, the third kind of improved HARQ feedback scheme is a good tradeoff between performance and calculation complexity.