Underground Downlink Cable Transmission System Simulation And Transmitter Implementation

Orthogonal frequency division multiplexing(OFDM)is a multi-carrier modulation technology with many advantages.The application of OFDM technology in cable transmission system can greatly improve the transmission efficiency of logging cable.Digital signal processor(DSP)is widely used in various communication systems because of its fast signal processing speed.The main work of this paper is to simulate the cable-based OFDM transmission system on MATLAB platform and verify the feasibility of the system,then design the transmitting prototype based on the simulation results and implement the transmitting prototype based on the TMS320C6748 hardware platform.This paper focuses on the hardware implementation of the prototype and the software algorithm used in the system simulation.The hardware design is based on the measured channel spectrum of the cable,and the bandwidth of the upstream and downstream system is reasonably allocated.And the process of RS coding,QAM modulation,IFFT,cyclic prefix addition,training sequence generation and addition used in transmitter are implemented by C language.On the software simulation,the whole system model is simulated.And for the system key technology algorithms such as QAM modulation,equalization technology,channel estimation,timing synchronization,etc.,different methods and different signal-to-noise ratio are compared to determine the system simulation scheme with the lowest bit error rate.Software and hardware demodulation are performed on the output data of the transmitting prototype to verify the data demodulation and correctness of the data structure of the transmitting prototype.Finally,the paper summarizes the improvement in the design.