Random Access For MTC In LTE Networks

Machine-type communication(MTC)is a key technology for achieving the Internet of Everything.It has high density,low mobility,short data packets,etc.And it has widely applied to mobile payment,smart metering,vehicle communication and so on,which has a promising market in the future.With the rapid development of Internet of Things technology,more machine-type communication devices(MTCDs)will be deployed in wireless cellular networks.However,the Long Term Evolution(LTE)networks,which are primitively designed for human-to-human(H2H)high speed downlink communication service,may not be able to handle a large number of bursty uplink random access requests from MTCDs.In this thesis,based on the standard random access procedure in LTE networks,we focus on the study of the serious collision problem caused by a large number of bursty random access from the perspectives of congestion control,resource allocation and collision resolution in detail.First,we introduce the network architecture and service features of machine-to-machine communication,as well as the basic concept of LTE network physical layer.Furthermore,the standard random access procedure based on LTE network is analyzed,and the problems in the random access algorithm are analyzed in detail.Sencondly,for a large number of fixed-location MTCDs bursty uplink random access scenario,we present a random access algorithm that reutilizes the idle and collided preambles to improve system resource efficiency.Based on the existing joint access class barring(ACB)and timing advance(TA)random access congestion control algorithm,the evolved node B adopts the load estimation algorithm to detect the collided preambles and merely assigns uplink resources to uncollided MTCDs.The MTCDs that did not pass the first ACB check but passed the second ACB check,utilize the reources scheduled by the idle and collided preambles.By designing the random access response format,the proposed algorithm can realize the utilization of the idle and collided preambles without increasing additional channel overhead.Theoretical analysis and simulation results manifest that our proposed algorithm notably outperforms the conventional joint ACB and TA random access algorithm in terms of four metrics: throughput,access delay,probability of preamble collision and resource efficiency.Finally,for the scene of massive delay-sensitive MTCDs random access at the same time,we propose a random access algorithm that jointly utilizes tree-splitting and TA to reduce the average delay of the device access procedure.The evolved node B adopts the treesplitting random access collision resolution algorithm to re-allocate new uplink resources for collided MTCDs in the same TA,which reduces the average access times and average delay of the device,and can provide a clear upper limit of the delay.In addition,the proposed algorithm is compared with the tree-splitting algorithm,and theoretical analysis and simulation are given to verify the accuracy of theoretical results.