Research And Implementation Of LTE Physical Layer Algorithm

As a 4G+ wireless communication technology,LTE-A(LTE Advanced)is a transition to 5G and will also provide technical support for 5G,theoretical downlink peak rate reaches 1Gbps.Channel capacity and spectrum utilization have also been greatly improved compared to LTE.The physical layer,as the bottom layer of the entire protocol stack,is the basis of the wireless communication system and determines the system's transmission method and efficiency,so the main content of this paper is to study and modularize the downlink of LTE-A physical layer.The article is based on the national major science and technology project "TD-LTE-Advanced multi-mode multi-frequency terminal protocol conformance TTCN test and development" project(20142X030010257).The Log-MAP decoding algorithm of Turbo codes is deeply studied.The influence of SNR on the decoding results of Log-MAP is analyzed,and a new SNR estimation algorithm is proposed.Simulation results show that the evaluation algorithm can effectively improve the BER of the MAP algorithm.Secondly,the paper completes the modular design and implementation of the baseband processing part of the LTE-A physical layer downlink,and the XSRP hardware platform is applied to modular testing and full-process data transmission testing.The results demonstrate the effectiveness of the modular design and the reliability of the link.The system simulation parameters can be flexibly modified because of the combination of software and hardware,which may facilitate further research on the LTE-A physical layer technology.The development history and trends of wireless communication systems,and the birth and evolution of LTE is presented at the beginning.Next,the basic framework,frame structure,physical resources,and key technologies such as OFDM,MIMO,and SCFDMA of the LTE-A physical layer are introduced.A new SNR estimation algorithm is proposed,which selects different noise power calculation methods according to whether there are empty subcarriers on the received OFDM symbols,thereby overcoming the drawbacks of the Boumard and DASS algorithms and improving the bit error rate of the Log-MAP algorithm.Then,the downlink transmission and reception process of the physical layer link is designed,and the modular design of the processing steps of channel coding,rate matching,modulation and demodulation is given.Finally,XSRP hardware platform is applied to achieve the whole process of LTE-A physical layer downlink data transmission test,through the comparison of the results of MATLAB and DSP to verify the design of each module.By passing the baseband processing to the DSP and turning on the RF,complete custom data and random data transmission and reception tests are performed.The results demonstrate the effectiveness of each module and the reliability of the link.