Improving Throughput by Multi-Cell Coordinated Vertical Plane Beam Control with Pre-Coding

Cellular mobile communication systems reuse the same frequency channel in geographically distant areas to improve the spectrum efficiency. However, co-channel interference among cells remains a critical issue. Mitigating co-channel interference leads to a further improvement in spectrum efficiency. One technique for mitigating co-channel interference is antenna beam tilting, which controls the vertical plane beam of base station antennas. In cellular mobile communication systems, antenna beam tilting is generally used by setting fixed beams at each base station. If the vertical plane beam pattern is changed dynamically for each mobile station, it is possible to significantly improve the SINR (Signal- to-Interference plus Noise Ratio), which drastically improves the spectrum efficiency. We propose here a vertical plane beam control method that uses pre-coding; the vertical plane beam pattern for each mobile station is easily set by controlling the phase of the baseband signal. The proposed method can be easily implemented with little or no modification of the antenna configuration at the base station. This system is effective for improving not only cell edge capacity but also overall cell capacity at the same time. A computer simulation shows that the spectrum efficiency of the proposed system is approximately twice that of conventional antenna beam tilting.