Research On Capacity Analysis And Noise Reduction Technology In PLC System

Power line communication (PLC) is widely used to transfer information via distributed power lines. Since the communicating price is significantly cut down, the power line communication has now attracted increasing concerts in recent years. However, as power line is not originally designed for transmitting signal, there are several side-effects when power line is used as the communication media, such as multipath effect, signal attenuation, impulsive noises, etc. These side-effects surely result in power line communication system can not achieve a high capacity and reliability. In order to solve these problems, we study the capacity of PLC channel and results are obtained as follow:(1) A power line channel model is established in the circumstance of attendance of the impulsive noise. By introducing Middleton’s Class A noise model, the distribution of channel noise is analyzed and the capacity of PLC channel is derived. Simulation results show that the capacity of PLC channel is related to the distribution of noise.(2) To promote the capacity of a PLC channel, the multiple-input and multiple-output (MIMO) power line channel model is proposed based on the three-phase power lines. The capacity of MIMO channel is analyzed by using singular value decomposition under the influence of impulsive noise. Furtherly, the quasi maximizing sum-rate precoding algorithm is introduced to improve the sum-rate. Simulation results show that the capacity of MIMO power line channel is much better than that of the traditional power line channel. When channel nosie is high impulsive, the proposed precoding algorithm can improve the PLC system performance.(3) To reduce the bit error rate (BER) in a power line communication system caused by implusive noise, an improved impulsive noise reduction method is proposed based on the partial transmission sequence method. The transmission signal is preprocessed by partial selection sequence method and then setting the threshold to reduce the impulsive noise. Simulation results show the peformaneces of the signal-to-noise ratio and the BER can be improved by using the proposed impulsive noise reduction method.