Power Line Carrier Communication System Based On LWT-OFDM

The signal modulation transmission model for Power Line Communication（PLC）systems often uses Orthogonal Frequency Division Multiplexing（OFDM）based on the Fast Fourier Transform（FFT）.Due to the complex channel environment and strong noise interference,the FFT-based OFDM system is susceptible to interference between subcarriers,resulting in poor transmission reliability,low communication efficiency and a high Peak to Average Power Ratio（PAPR）.To this end,the thesis applies the Lifting Wavelet Transform（LWT）to the implementation of OFDM and the design and development of a PLC system based on a high-performance ARM processor to improve the communication performance of the PLC system.The main work of the thesis includes:1.the power line channel transmission characteristics and noise features are analysed,and the overall research and design plan is determined by combining the functional requirements and technical index requirements.The system is designed and developed according to the G3-PLC standard;LWT is used instead of FFT for OFDM implementation to improve reliability,efficiency and reduce the peak-to-average ratio;the system is implemented in hardware and software based on a high-performance ARM processor.2.Based on the study of LWT principles and characteristics,the design of the system signal transmission model and processing algorithm is carried out.The LWT is used for OFDM modulation/demodulation,and its good orthogonality is used to reduce inter-subcarrier interference and form an LWT-OFDM system to effectively improve reliability;the LWT characteristics are combined with Cyclic Prefix（CP）to reduce the use of cyclic prefixes to improve transmission efficiency;Integralization of the LWT helps to facilitate the improvement of system implementation efficiency.Based on the system performance simulation analysis,the reliability and PAPR performance are further optimized by combining multi-layer LWT transformation,RS coding and limiting filtering.3.Based on the theoretical research and algorithm design,the system hardware and software design and development is carried out using the STM32H series ARM processor as the core.The hardware module includes the core processing unit circuit,the output/input filter circuit for modulation/demodulation and the coupling circuit.The software development implements the RS coding of the transmitted data,LWT-OFDM modulation and symbol synchronization of the received data,RS decoding and LWT-OFDM demodulation.A PLC experimental system based on LWT-OFDM has been established,and the functions and communication performance have been tested and analysed.The experimental results show that:the implementation of OFDM based on LWT improves the reliability of the system,reduces the signal-to-noise ratio required for RS error correction processing threshold BER by 5.5d B,and in combination with RS coding,there is a performance gain of about 9.2d B at a BER of 10^-3;the combined application of LWT and limiting filtering reduces the peak-to-average ratio performance of the system by about 3.3d B;the integralization of LWT improves the system transmission rate and implementation efficiency.