Research And Implementation Of Key Technologies For Downlink Channels In Broadband Cognitive Communication System

In recent years,the quick growth of the information industry has proposed higher requirements for the performance of mobile communications,so that the Long Term Evolution(LTE)mobile communications system has always received great attention from the communications industry.5G network,as a new infrastructure strongly advocated by the country,is also closely related to LTE.This paper refers to the LTE physical layer protocol to research and implement the key technologies of the downlink channel of the broadband cognitive communication system.Using Matlab to Build a physical downlink shared channel(PDSCH)floating-point simulation link,study its performance and provide a performance reference for digital signal processor(DSP)Downlink implementation.Based on the Texas Instruments TMS 320C6670 multi-core DSP chip,the implementation of the fixed-point link of the broadband cognitive communication system is implemented,which is about 0.5dB different from the Matlab floating-point link performance,which verifies the correctness of the DSP fixed-point link implementation.Based on the frequency-domain energy detection algorithm,the interference detection performance of interference in the presence of LTE signals is analyzed.The data transmission interface scheme and data cache scheme between the physical layer and other layers are designed,and the timing analysis and optimization of the multi-core implementation processing flow are performed.Finally,a video call stepby-step test was conducted to check the correctness and completeness of the broadband cognitive communication system.This thesis conducts research on the physical layer protocol of the LTE-based broadband cognitive communication system,and analyzes its time-frequency domain resources and downlink key channels in detail.Designing the overall process of Matlab simulation link of PDSCH evolved NodeB(eNB)and User Equipment(UE)based on the protocol,which the transmission mode is designed for single-port,transmit diversity and space division multiplex.The performance simulation of the simulated link under different modulation and transmission modes under the Gaussian channel and Rayleigh channel provides a performance reference for the correctness of the DSP fixed-point link.This paper focuses on the downlink implementation of DSP-based broadband cognitive communication systems.This paper analyzes the DSP platform AMC-2C6670 and the multi-core chip TMS 320C6670,and studies and analyzes the co-processing of the DSP fixed-point link implemented in the broadband cognitive communication system,including the bit rate coprocessors,viterbi coprocessor and so on.Based on the DSP chip,the paper completes the overall process design and modular processing of the system's downlink sender and receiver,and focuses on the PDSCH module process planning and related algorithms.This paper completes system downlink performance test and compares with the corresponding Matlab floating-point,the conclusion is obtained that the downlink of the broadband cognitive communication system based on DSP is correct.Based on the frequency-domain energy algorithm,the paper simulates and analyzes the interference detection performance of single-tone,multi-tone,and narrow-band interference in the presence of PDSCH signals.This paper analyzes common interference types and interference detection algorithms,analyzes and studies the Forward Consecutive Mean Excision(FCME)and compares the performance with the Continuous Mean Excision(CME)and analysis their advantages and disadvantages.The performance of FCME and CME is basically the same when the interference is high,but the performance of FCME is slightly better than CME when the interference is low.The paper build models of single-tone,multi-tone and narrow-band interference and simulates and analyzes the interference detection performance in the presence of PDSCH signals.Compared with noise,the statistical characteristics of PDSCH signals are closer to the interference signals.Therefore the introduction of PDSCH signals will deteriorate the interference detection performance.Finally,the influence of the frame accumulation number on the interference detection performance in the frequency domain energy algorithm is analyzed.The larger the frame accumulation number,the better the interference detection performance.The paper plans and achieves the data transmission interface between the physical layer,the MAC layer and the FPGA of the broadband cognitive communication system,and researches the data cache and overload processing between the layers.The thesis designs and implements the switching of various state information at the physical layer,and completes the overall process from acquiring system information to processing business data.The paper also performs timing analysis and optimization of DSP multicore processing,compares and analyzes the processing time of dual-core and triple-core processes on the eNB,and optimizes the processing time of quad-core processes on the UE,so that the time each core processes each frame is less than 1ms.Finally,the thesis verifies the integrity and correctness of the broadband cognitive communication system designed in this paper through the step-by-step test of the video call.The access of the video call server proves that the communication system link designed in this paper is complete and correct.At the end of the paper,the work and contributions of this paper are summarized,and the next steps and research directions of the broadband cognitive communication system downlink are proposed.