The Methods Of Cell Outage Compensation In The Radio Access Network

Self-organizing network is among the hottest topics in telecommunication network research and development, eagerly awaited by network operators. The three commonly distinguished domains of self-crganisation are self-configuration, self-optimisation, and self-healing. The idea is to equip a network with the capability to automatically adapt its configuration/parameter setting to the environment. Self-organisation network functionalities are therefore receiving prominent attention in the standardization of LTE by3GPP、NGMN.Future radio access network is supposed to have SON function, and each function domain can be divided into several use cases. Cell Outage Compensation (COC) is a ues case of self-healing, which aims to minimize the network performance degradation when a cell is in outage. This is done by automatic adjustment of network parameters in order to meet the operator’s performance requirement. COC is realized by altering the radio parameter of the neighbouring cells, which means that the UEs served by neighboring cells may be affected, so it should be taken into account and tradeoff between coverage and other quality indicators. Usually, COC does work, but that it does not fully compensate for the cell in outage. At present, research on SON mainly focus on self-configuration and self-optimization, but the the self-healing technology is still in its beginning state. As such part of self-healing concept, COC is the topic of this paper.The main research contents and innovation points are depicted as follows:An automatic COC mechanism of simultaneously maximizing coverage while minimizing inter-cell interference for a cell in outage was proposed. By modeling the problem of pilot adjustment, an optimized mechanism is given, which could adjust the neighboring cells pilot power until the coverage area just touch the operator policy. As an illustration, a derivation has been presented for pilot power optimization. The simulation results show that the proposed method is more feasible in radio access network with medium and low load.Remote Electrical Tilt (RET) adjustment based method for cell outage compensation was proposed. Adjusting the antenna tilt shapes the cell footprint. For example, up tilting extends the coverage of neighboring cells. So the antenna tilt was adjusted such that the coverage is maximized given constraints on pilot quality defined in terms of cell-edge users. Simulation results show that the proposed algorithm is feasible.A method of fully compensating the outage cell by adjusting neighboring cells radio parameters was proposed. Approaching the goal of automatically compensating for all the coverage hole in the outage cell necessitates optimization of network parameters configuration. In this method, three radio parameters are adjusted:transmit power of pilot channel, antenna tilt and antenna azimuth. The problem of cell outage compensation is tackled in two steps. Firstly, we have found an optimal antenna configuration to minimize the uniform pilot power for all the neighboring cells with a simulated annealing algorithm which can search the optimal vector effectively in the solution space of possible configurations starting from an initial configuration; then we adopt the optimization algorithm by pilot power control iteration which is running on the top of existing TPC to minimize the total of nonuniform pilot power under the antenna configuration vector. Experiment results show that all the users were covered at least by one cell.A high load cell outage compensation method in LTE radio access network was proposed. For cell outage problem due to various faults in radio access network, and features that LTE has some key technology, e.g. Orthogonal Frequency Division Multiple Access (OFDMA), Automatic Modulation and Coding (AMC) and flat architecture, an distributed cell outage compensation algorithm was presented. In the presented algorithm, the parameters of cells neighboring a failed cell/cite can be automatically adjusted such that the coverage is maximized given constraints on quality defined in terms of cell-edge user SINR. Simulation results show that the proposed algorithm is able to recover a significant percentage of the users that would otherwise be dropped.