Analytical Results of Field Experiment on Precoding-Based Vertical Plane Beam Control for LTE-Advanced Systems

Most current cellular mobile communication systems employ 1-cell frequency reuse to achieve high spectrum efficiency. With 1-cell frequency reuse, the co-channel interference among cells remains a critical barrier to achieving further improvements in the spectrum efficiency. Vertical plane beam control at the base station is one approach to mitigating the co-channel interference. The conventional method of vertical plane beam control, antenna beam tilting, is widely used. In antenna beam tilting, the tilt angle is generally fixed for each base station. If the vertical plane beam can be changed dynamically, it becomes possible to significantly improve the reception environment. Given this background, we have proposed precoding- based vertical plane beam control. In the proposed method, the vertical plane beam pattern for each mobile station is easily changed dynamically by just the precoding operation without changing the conventional antenna configuration drastically. To demonstrate the feasibility and performance of the proposed method, we develop a prototype system, in which the proposed scheme is implemented on an LTE- based system, and conduct a field experiment. This paper overviews the prototype system and the field experiment results. They clarify that the proposed method is effective in mitigating interference level to the neighbor cells as well as improving the desired signal level in the serving cell. We also conduct a theoretical analysis and confirm that the experimental results well match the theoretical results.