Research On Multi Channel Access And Hybrid Communication Mechanism For Power Line Communications

Low voltage power line carrier communication has problems like complicated network topology and hostile communication environment.Leading to low reliability of power line communication and limited communication distance,which limits the scale development of power line communication technology.In this paper,the medium access control protocol and the cross-band communication of low voltage power line communication are studied from the point of view of improving the reliability of power line communication and increasing the communication range.Firstly,this paper analyzes the current development of power line communication technology and summarizes the protocols and standards of narrowband communication and broadband communication respectively.On the basis of comparing and discussing the medium access control protocol in each communication standard,this paper puts forward the existing protocol problem s.Secondly,the characteristics of low voltage power line network are studied,and the frequency attenuation effect,multipath effect and noise characteristic of power line are analyzed from the aspects of low voltage power line network structure and transmission characteristics.The possibility of cross-band communication is discussed with the relevant measured data,breaking the constraints of conventional broadband communications and narrowband communications.Then,the existing low voltage power line media access control protocols are summarized,and the advantages and disadvantages of each protoco l are analyzed.On this basis,a new medium access control protocol design requirement for large-scale power line network is proposed,which is characterized by being able to adapt to large-scale network application.In the case of expanding the network size,new protocol can still maintain a high transmission efficiency and ensure high network throughput.At the same time,solve the exposed terminal and hidden terminal problems to a certain extent.Next,we design a new media access control protocol based on time period,which can effectively reduce the probability of collision between nodes and ensure the transmission efficiency of the network by means of periodic access mechanism,priority resolution mechanism and random back-off contention.The simulation results show that the proposed new medium access control protocol is more stable and efficient in large-scale network conditions,compared to the conventional protocols.Finally,a digital front end based on equivalent complex baseband and transceiver window is designed to realize cross-band communication.At the same time,a frequency identification method based on preamble sequence is designed to realize the channel recognition and frequency selection of power line communication node.Select OMNe T++ patform to simulate performance,the simulation results show that in the multi-frequency communication network,the rate of node access is improved obviously,which is of great significance to improve the reliability of power line carrier communication.