Reseach Of TD-LTE Downlink And Implement Of Service De-Mapping On Picochip DSP

In order to maintain competitiveness of 3G within the next decade,the Third Generation Partnership Project(3GPP)organization passed the 3G long term evolution (LTE)scheme in the end of 2004. The fundamental targets for LTE are increased data rates,reduced latency,improved system capacity and coverage as well as reduced operator costs. Currently,LTE has been widespread concerned by all telecommunication operators, so the LTE technology research is of great significance. In the LTE product development process, reducing development time, lowering cost and power of baseband processor is the industry's focus. Picochip multicore DSP is a development platform that is cost-effective, easy to use and has low power-performance ratio.In this thesis, TD-LTE downlink has been studied, including the signal processing principles and methods of sender and receiver. Service De-Mapping is researched thorouphly based on the analysis of the theory of downlink. In order to better analyze the performance of the reseiver,a downlink simulation platform is set up.For different HARQ retransmission scheme, the simulation results conclude that Incremental Redundancy HARQ retransmission scheme is superior to Chase Combined HARQ retransmission scheme, but has a higher complexity.Finally, the thesis focuses on implement of the Service De-Mapping on picochip multicore DSP platform. LTE has higher requirement on peak rates and latency. Therefore, how to make better use of parallel processing feature and designing flexibility of picochip DSP to increase processing speed and reduce latency is concerned.Service De-Mapping includes HARQ Combining, Rate De-Matching, Channel Decoding, CRC Check and so on. HARQ Combining module reduced latency through the method of independently reading and writing SDRAM.The difficulty of Rate De-Matching is how to design a loop buffer and the interleaver in order to save resources and achieve the rate requirements.Through a comparison of several designs, the final adoption of ping-pong mechanism achieved good results. The designing of CRC Check module focus on fast CRC calculation and how to calculate TB CRC and CB CRC simultaneously to generate ACK/NACK flag. Finally, each submodule and Service De-Mapping module were tested.The results show that the module works steadily and has good performance.