Research Of Interference Coordination And Load Balancing In Three Dimensional Mimo System

MIMO (Multi-Input Multi-Output) is one of the key technologies of Long Term Evolution (LTE) system and LTE-Advanced system, which is able to improve data transmitting rate and spectrum resources utilization. Traditional two dimensional MIMO (2D MIMO) only utilize the horizontal dimension, while three dimensional MIMO (3D MIMO) can be achieved through using active antenna system (AAS). Three dimensional MIMO can utilize the vertical dimension as well as the horizontal dimension. Therefore, the spatial degrees of freedom of MIMO are increased. Such technologies as three dimensional beamforming and vertical sectorization can be realized. Research of interference coordination and load balancing in three dimensional MIMO system is significant to further improving users’ received signal to interference and noise ratio (SINR) and system’s spectrum resources utilization. The main work and results are as follows:Firstly, by means of researching the latest proposals and papers, this article proposed a three dimensional channel modelling method based on the existing two dimensional channel modelling method. Then the channel model is added to the OPNET LTE-Advanced system level simulation platform, and the performance of coordinated multi-point (CoMP) transmission in heterogeneous scenario is evaluated. Simulation results demonstrate that CoMP in three dimensional MIMO system can achieve a higher gain in cell average throughput and cell edge throughput than that in two dimensional MIMO system.Secondly, the interference coordination in three dimensional MIMO system is studied, and an interference coordination algorithm combined with multiple downtilts and fractional frequency reuse is proposed, which is proved to be effective to improve users’SINR and system’s spectrum resources utilization. Besides, a method of interference coordination by coordinated transmission of inner and outer sector in vertical sectorization is proposed, which can turn interference signal to useful signal for boundary users. Simulation results demonstrate that the propsed method can improve the system’s perfomance.Lastly, a load balancing algorithm by adaptively adjusting antenna downtilts is proposed. The coverage of one base station can be controled by adjusting its downtilt, and coordinatedly adjusting multiple base stations’downtilts can achieve load balancing. System level simulation results prove that the proposed algorithm can balance the load effectively and increase the system’s average spectrum utilization.In summary, these research work and results have important guidance significance and reference value to theoretical research and perfomance evaluation on three dimensional channel modelling and three dimensional MIMO system.