Research On Coexistence Interference Between TD-LTE And LTE FDD Systems

LTE supports two duplex modes: TD-LTE and LTE FDD. As FDD licensing and China Tower Corp are established, the coexistence of two LTE systems is likely to occur. When two LTE systems coexist in adjacent frequency bands, the interference issue will appear, which will lower the overall system performance, even disable the system operation. Therefore, it is of practical significance for us to research the coexistence interference. In this paper, we utilize simulation and filed test respectively to investigate the coexistence problem of two LTE systems.Interference simulation part adopts the method of Monte Carlo simulation. This paper simulates the influence of the system performance using MATLAB from different system Parameter Settings, such as different location offsets of base station, power control sets, system bandwidths and frequency sets. Meanwhile, the improvement of the system performance by adopting the technique of beam-forming and inter-cell interference coordination mechanism is also investigated. the simulation results of different scenarios show the variation of system throughput, then we analyze the reason and put forward some suggestions of avoiding interference; It also comes to a conclusion that adopting beam-forming technology and inter cell interference coordination mechanism can significantly reduce the isolation requirements.In filed testing, China Mobile`s F-band TD-LTE system is selected as the victim system, and China Telecom`s LTE FDD(1.8GHz) is selected as the aggressive system. It is chosen as a criterion that a single RB uplifting over 0.8dB to indicates the interference. At first, it troubleshoots the physical isolation of all sites, then, it troubleshoots the sources of interference. The opening and closing experiment is operated as the final step, collecting the KPI indicators of victim system and the change of background noise. From the statistics, the KPI of all sectors appears minor fluctuations during the Telecom FDD system opening and closing experiment, and doesn`t affect the normal business of CMCC. This paper also analyzes the impact of different frequency isolation and bandwidth setting on the background noise of victim system, which proves the results of simulation. Finally, we recommend the space design principles and the interference criteria, providing a reference for proceeding project.