Multi-carrier Cell Structures with Vertical and Horizontal Sector Offset using Static Beamforming

Macrocellular networks with frequency reuse across cells suffer from high interference at the cell boundaries, resulting in a very uneven distribution of user throughput. Recently it has been shown that for multi-carrier networks a horizontal angular offset configuration for the second carrier can significantly improve the performance and call drop rate of the network. In this paper this concept is extended to the vertical dimension by providing additional cells with higher downtilt while retaining the naturally resulting interference avoidance properties. Simulations for UMTS HSDPA show that with the additional cell layer with vertical downtilt can increase the average user throughput by 126% and the throughput of the worst 5th percentile by 205%, compared to a traditional 3 sector macrocell configuration. It is shown that the proposed cell configuration also outperforms conventional 6 sector configurations with the same number of antennas and cells per site. In addition, it is shown that the addition of the second cell layer does not significantly increase the handover failure rates over conventional cell configurations. The concept scales well to higher sectorizations.