Research On Theory And Key Technologies Of Self Optimization In LTE/LTE-Advacned Self Organization Network

The explosive increasing of mobile broadband traffic pushes the speed-up of network expansion and upgrading, as well as the fast increment of operation cost. At the same time, the ARPU is decreasing gradually by the highly competition between the mobile operators. Mobile carriers have never payed so much more attention on profit earning and cost control than today. Reducing OPEX and CAPEX has become one of their core works.But the deployment of new wireless technology and network, like LTE, is necessary. Carriers must keep the competitive power among his competitors. Thus the operator must face the status of running multiple mobile networks just like2G,3G and LTE, with multiple frequency bands. So, the operation complexity and cost have to be increased, unless we use more automatic means in the usual network running and maintenance.That is why Self Organization Network (SON) comes into being. SON is defined as a set of automatic functions and control processes, which can be used by operators, without manual intervention, to manage the mobile network, raise operation efficiency and decrease operation complexity. Now SON has become one of the hottest research spots, and the important part of the standardization of LTE/LTE-Advanced.The dissertation gives a deeply and comprehensive research on the theory and key technologies of SON, especially on the self optimization technologies. We choose three topics as our main study directions:load balancing, co-optimization of load balancing and handover, dynamic wireless resource scheduling. Based on the fully analysis and study on multi-node cooperation, multi-technology coordination and multi-user co-scheduling, we proposed some creative ideas and solutions on these aspects.The main research and creative points of this dissertation are concluded as followed:1. The study of theory and technology of Load Balancing (LB) in SONIn order to reach load balance in the overall network cells as much as possible with the minimun number of handver, we study the relationship between LB and netwok flow theory. Firstly we prove that LB is a classical problem of network flow. Secondly, a novel Dynamic Minimum Cost Load Balancing (DMC-LB) algorithmn is proposed to solve the problem, which is based on shortest cost path algorithmn and is added in multiple restrictions of real mobile network. In the design of this algorithmn, the traffic character of LTE is analyzed, as well as the capacity and cost of the LB network flow graph. Then, using the rule of choosing offloading cell which has max users meeting handover condition at each step, we optimize the classic shortest cost path algorithmn. Through simplifing the path-choosing calculation, we improve the classic algorothmn’s efficiency. System simulations show that DMC-LB peforms well not only in optimization of network load distribution, but also in offloading users from heavy load cell to light load cell. DMC-LB can get the optimal solution of LB at the minimum cost of handover, while keeping the user access success ratio unworsed.2. The study of theory and technology of co-optimization of Load Balancing (LB) and Handover (HPO) in SONDue to different optimization targets, when load balancing (LB) and handover performance optimization (HPO) are executed at same time in SON, the inconsistency and conflict may occur. A novel co-optimization algorithm is proposed in this part, which can coordinate these two technologies to lift the network performance and user satisfaction concurrently. Based on the analysis of LB and HPO performances, co-satisfaction facto (CSF) is defined as the weighted sum of user satisfaction ratio and handover satisfaction ratio, which is used as index to measure the co-optimization algorithm performance. In the design of the algorithm, we analyze and propose the calculation method of offset value used in LB and hysteresis value used in HPO. Furthermore, we introduce radio link failure ratio (RLFR) as the guide line of optimization switch and direction. A LTE system level simulation platform is built to evaluate the algorithm performance. Simulation results show that the algorithm can effectively coordinate load balancing and handover optimization at the same time.3. The study of technology of wireless resource scheduling in SONThis part focuses on how to optimize the wireless resource scheduling among multi-users in LTE SON. We deeply analyze the factors which can influence the scheduling performance greatly in LTE and the possibility of adjusting key factors in scheduling algorithm according to user SINR distribution feature. A new index, user SINR dispersion degree, and a novel self optimization scheduling algorithm are proposed, which configure the maximum resource block (MaxPRB) dynamically according to the users’ SINR distribution status. A LTE system level simulation platform is built to evaluate the algorithm performance. As an improvement of classical proportional fairness scheduling algorithm, this algorithm can adjusts the single user resource scheduling granularity in one TTI by cell user density and user locations. Simulation results show the enhancement both in system throughput and user fairness.The research outputs related to this dissertation have been published or accepted as papers in institute of electrical and electronics engineers (IEEE) journals and conferences.