Rsearch And Implementation Of Physical Downlink Shared Channel In TD-LTE Systems

In response to the process of mobile broadband and broadband wireless,3GPP proposed and formulated the LTE standard.LTE takes MIMO and OFDM as its core technologies.Compared with the previous generation of mobile communication system,LTE has more flexible configuration,higher peak rate,smaller delay and simpler structure.LTE technology is mainly divided into LTE-TDD and LTE-FDD.In addition,TD-LTE refers to LTE technology in time division duplex mode and it is a LTE technology standard dominated by China.This thesis mainly focuses on the research and implementation of the key algorithms for PDSCH.The analysis of PDSCH involves the study of sending and receiving processes,the definition of different modules and the establishment of the link.Successfully analyzing the PDSCH is the basis for analyzing the LTE physical layer.The selection of algorithm affects the performance of channel analysis,so it is very important to study different algorithms in LTE.First,the key algorithms of the transmitter and the receiver in the LTE PDSCH downlink are studied.Transmit diversity,rate matching and resource mapping of the transmitter are mainly studied.The OFDM demodulation,channel estimation and Turbo decoding of the receiver are studied.The formulas for solution of transmit diversity under two antenna ports are deduced and the rate matching process is analyzed.Then the resource mapping process of PDSCH is explained.The common channel estimation algorithms are analyzed and compared in terms of complexity and performance,including LS,MMSE and de-noising algorithm using DFT in time domain.The constant interpolation,linear interpolation and Gaussian interpolation are simulated.The common algorithms of Turbo decoding are studied,including MAP,Log-MAP,MAX-Log-MAP and SOVA algorithms.The performance of several algorithms is compared at different iteration times,and the complexity of the algorithm is analyzed.This thesis uses matlab to simulate the downlink shared channel link and compares the block error ratio under different channels and antenna conditions.Finally,this thesis introduces the common software radio platform that is USRP+UHD.The overall framework structure is summarized.The modules of the PDSCH are introduced.In addition,some modules have been optimized.Finally using the radio platform to receive the actual air interface data and analyze the PDSCH.The test result shows that the downlink shared channel can be analyzed.