Research And Implementation On Protocols Of Data Link Layer For Broadband PLC Networks

A broadband PLC network is a kind of network established by taking PLC equipments as network nodes.With its superiority of low communication cost and convenient connectivity,it is universally applied in data acquisition,industrial control and other fields.This thesis selects the broadband PLC networks data link layer protocols based on IEEE1901.1 as the research object,which has a wide spectrum and high-speed communication rate.This thesis first introduces the research background and current situation of broadband PLC networks data link layer protocols,describes the application scenarios and characteristics of broadband PLC networks,introduces the key mechanism of IEEE1901.1 broadband PLC networks data link layer protocols standard,and describes the serial port communication,multi thread and other technologies used in the implementation process of broadband PLC networks data link layer protocols.Next,aiming at the problem of slot waste caused by beacon slot allocation method in broadband PLC networks data link layer protocols,a beacon slot allocation method based on node layer number is proposed.According to neighbor table and slot allocation information,the time to enter CSMA slot in advance is calculated,which reduces the waste of beacon slot and improves channel utilization;Aiming at the problem of excessive control overhead caused by invalid slot allocation information in beacon frame broadcast by nodes that have entered the networks,an efficient beacon frame broadcast mechanism based on topology information is proposed,which reduces the networks control overhead by deleting slot allocation information of nodes that are not greater than their own level numbers and non-descendant nodes that are larger than their own level numbers and within the range of two hops.Then,the implementation of broadband PLC networks data link layer protocols are divided into serial communication module,beacon frame processing module,access request frame processing module,access reply confirmation frame processing module,channel access module,CRC module and routing module,According to the operation process of each module,the specific design and implementation are carried out.The data link layer protocols of broadband PLC networks are developed by using C language under Linux operating system,and the beacon slot allocation based on node level number and efficient beacon frame broadcast mechanism based on topology information are realized.A test platform is built based on the test topology to test the function and performance of broadband PLC networks data link layer protocols,Through the test,it is found that the function of broadband PLC networks data link layer protocols meets the expected design and development requirements;Through the performance comparison,it is shown that the improved mechanism can effectively reduce the average end-to-end round-trip delay,improve the channel utilization and reduce the control overhead.Finally,the work content of this thesis and the problems to be solved in the future are summarized.