Research And Implementation Of Downlink Physical Channel In Broadband Trunked Communication System

The Long Term Evolution as a quasi-4G has been highly concerned by the communications industry since its inception.Based on the TDD-LTE physical layer protocol,this paper studies the transmission process and key technologies of the downlink physical channel of B-trunc system.This paper implements the fixed-point implementation of the physical layer transceiver channel on TI's TMS320C6670 multicore DSP chip,designs the data transmission interface scheme between the physical layer and upper layer,realizes the preliminary system level joint debugging test between the uplink and downlink and the upper layer.This paper deeply studies the TDD-LTE physical layer protocol,and detailed analysis of some messages involved in the communication process between the eNodeB and the terminal(include Master Information Block,System Information),based on the time-frequency resources occupied by the downlink physical channel we design the transceiving process of the physical channel carrying the typical message.This paper studies the key modules in each channel processing flow,and builds float-fixedlinks of control channel and service channel based on MATLAB platform.The performance of PDCCH and PDSCH under typical parameters is tested and analyzed under Gauss channel and Rayleigh channel.In addition,the paper simulates and analyzes the performance of two channel under the condition of synchronous residual delay and frequency residual,and verifies that the system performance should be maintained within the acceptable range for time synchronization and frequency synchronization accuracy requirements.The paper builds a dual DSP test system based on LTE standard 20 M bandwidth broadband trunking communication system on TMS320C6670 multi-core DSP chip platform,tests the performance of fixed-point link,compared with the floating-point link,it is verified that the performance loss introduced during the implementation of the fixed-point link did not exceed 0.5 dB,in addition,the performance of the fixedpoint link delay and frequency offset residuals is tested and analyzed.This paper also studies the coprocessor of DSP.The BCP is used to implement the modules of base station side such as CRC addition,channel coding,rate matching and modulation processing.The VCP2 is used to implement the decoding of PDCCH.The generation of OFDM symbols of the base station side and user side is implement by using the FFTC.The paper analyzes the transmission characteristics of various messages,designs and implements the switching schemes on the user side,and the test results meet the requirements.Based on the standard LTE resource structure,this paper studies the characteristics of time-frequency resources of different bandwidths,analyzes the characteristics of DSP resources,and implements the single DSP 8M testing system for police communication systems for the special requirements of police communication systems,tests time complexity of the system,and the test results meets the system requirements.This paper designs the data transmission scheme between the physical layer and the MAC layer in the downlink system of the trunking communication private network,and uses the Gigabit Ethernet port on the DSP chip to perform parameter and data interaction.Furthermore,the interactive connectivity between the physical layer and the MAC layer is tested and verified for correctness.