Research On Massive Access Control Mechanisms For Smart Grid

Smart Grid can improve energy efficiency,the safety and reliability of power supply,and achieve storage and remote control,so it is the shape of grid to come.The communication mode in Smart Grid is Machine to Machine communication.Generally,M2 M uses LTE technology as the wireless communication mode for the good communication performance of LTE.But if we apply LTE to M2 M directly,there are many problems need to be solved,and the most serious problem is the access overload.Because a distinct feature of M2 M is having massive communication terminals and it’s a common situation that many UE apply to access simultaneously.And this will lead to access overload easily and cause system performance degradation and even system crash.So,this thesis focus on the LTE random access control mechanisms.Firstly,this thesis outlines the Smart Grid communication and introduces the significance and the current status of studying massive access control mechanisms.The basic random access procedure,the corresponding mathematical model,the popular flow models and recent access control mechanisms are also introduced.The access overload problem is also analysed by simulations.Secondly,this thesis thoroughly studies the Access Class Barring(ACB)mechanism and its basic principle,analyses the drawbacks of the fixed control factor ACB and summarizes the current research direction of ACB.According to the difference of the method of load estimation,two self-adaption estimations ACB: qualitative estimation and quantitative estimation are proposed.By simulations,both of the two methods can obtain high access success probability and the quantitative estimation performs better in access delay.Finally,this thesis thoroughly studies the class-based access control mechanisms.Because of the variety of terminals and their different communications requirments,we grade the traffics according to the difference of their requirments of access delay.Aiming at the class-based UE,this thesis proposes a preamble-split access control mechanism and get the suitable grouping method by theoretical derivation in order to guarantee the first access of high-class UE.According to simulation results,the mechanism can can provide class-based access service,and ensure the high access success probability of all the UE.