Research On Self-Healing Technology Of LTE-Advanced System

The standardization body3rd Generation Partnership Project(3GPP) began to put forward the concept of SON (Self-Organizing Network) in the Release8.The target of SON function is to decrease human involvement in the network planning and operation and maintain, reduce the cost of the construction and operation of network, and which hopes to bring users better business experience.SON functions consist of Self-Configuration, Self-Optimization and Self-Healing, and the corresponding use cases are developed in the agreement. Cell outage scenario is one of use cases of self-healing. In the scenario, when there is a loss of total radio services in the outage cell, all the UEs cannot establish or maintain all the Radio Bearers (RBs) via that particular cell. For example, all the Cell Center Users (CCU) and Cell Edge Users (CEU) cannot establish the RRC connection in the outage cell. There are multiple causes for a cell outage, e.g., hardware and software failures (radio board failure, channel processing implementation error, etc.), external failures such as power supply or network connectivity failures, or even erroneous configuration. It’s the task of Self-Healing to timely detect the cell outage and trigger appropriate compensation method in terms of an adaptation of one or more control parameters in surrounding cells, in line with the operator-formulated policy regarding the trade-off of local and regional performance effects. The article is one part of the major projects of the National Science and Technology, and its subject is to make in-depth research in the network self-healing aspect.The main research contents and innovation points are depicted as follows:The in-depth analysis of the impact of the radio antenna parameters (e.g. remote electrical downtilt, beam forming) on cell coverage are conducted, and an cell coverage compensation based on automatic adjustment of the downtilt of the surrounding cells was proposed.The adjustment of downtilt has a direct influence on the coverage of cell. The radius of cell becomes larger with the decrease of the antenna’s downtilt, and vice versa, the coverage will be smaller. First fix the quality threshold of reference signal, and the centralized SON network architecture will be used. We applied GA (Genetic Algorithm) in the adjustment the downtilt of compensating cells based on certain operator strategy. The operator strategy generally refers to how to make a tradeoff between coverage and capacity.Assuming coverage has been received, a users’access and RB’s allocation scheme was proposed. LTE system allocates resource based on RB (Resource Block), and which represents a different time-frequency resources, when the adjacent cells allocate the same RB to users, which result in ICI(Inter-Cell interference), we can apply the scheme to reduce the ICI to a low level. The simulation results show that this scheme can reduce ICI and improve the network throughput effectively.