Design And Implementation Of Efficient Modulation Based Power Line Communications

Power line communication (PLC) uses the existing power line as transmission medium to transfer information. Compared to traditional communication techniques, it has advantages that power line covers wider and it doesn’t need to re-lay communication lines. Meanwhile, China’s smart grid also needs PLC technology to support. So how to get reliable, fast, low-cost communications on power line has great theoretical and practical value.Currently narrow band low voltage PLC generally uses Binary Phase Shift Keying (BPSK), Frequency Shift Keying (FSK), and Quadrature Phase Shift Keying (QPSK) modulation, etc. Compare to these, efficient modulations have narrower bandwidth. Moreover, by using impacting filter in its demodulator, we can convert phase transitions into amplitude compact. Coupled with impacting filter’s narrowband-pass characteristic, the efficient modulation system with impacting filter has strong anti-noise and anti-fading capability.This paper mainly researches how to use efficient modulations to realize PLC, and on the basis of ensuring reliable communication, how to reduce overall system cost as much as possible.First of all, this paper analyses and gives the models of the power line channel’s attenuation and noise characteristics which are the basis of the follow analysis and simulations.Secondly, EBPSK modulation, impacting filter and FPGA development platform are introduced. EPBSK modulator and demodulator are designed and realized in FPGA. There are serial communication, clock, modulation, bit synchronization and frame synchronization modules in this system.Thirdly, error correction codes were discussed. Several channel codes whose performance good with short length are compared via simulations. Moreover, reliability formula is deduced based on EBPSK modulation using impacting filter.Finally, M-ary Phase Position Shift Keying (MPPSK) modulation and modified MPPSK modulation are introduced. In modified MPPSK system, the demodulation scheme using max-value position searching is proposed and proved to be a better way to realize PLC than that of using EBPSK system. Based on the EBPSK system, fully digital MPPSK demodulator is implemented with lower cost. Eventually, RS coder and decoder are implemented in the system for better transmission performance.