Beamforming-based Coverage Control Technology For Cellular Mobile Communication Networks

In cellular mobile communication networks, the actual coverage region is the area where the received signal power and signal-to-interference and noise ratio (SINR) of the common control signals are higher than the preset thresholds respectively. Therefore, coverage control for cellular networks according to the actual propagation conditions is an important task in both network design and network operation stages.In this paper, we study the beamforming-based coverage control technology for cellular mobile communication networks.To meet the requirement of seamless coverage and low inter-cell interference in network design stage, an algorithm is proposed to obtain the optimal weight vector of array antenna. Weak-coverage area ratio (WCAR) and over-coverage area ratio (OCAR) are introduced as the metrics for evaluating coverage effect. The cellular network is divided into many sector clusters, each consisting of several adjacent sectors whose main beams point at the same area from different base stations. For every cluster, optimization problem is formulated, with the objective function of WCAR and the constraint on OCAR. Through reasonable approximations and using semi-definite relaxation method, the nonconvex problem is transformed to a convex problem. The procedure is presented to obtain optimal weight vector and corresponding WCAR and OCAR. The seamless coverage of whole network can be realized by applying the above procedure to every cluster. Simulation results validate that the formed coverage with the proposed algorithm has minimum weak-coverage area and no over-coverage area.In the network operation stage, the common control signals’ coverage quality of some region decreases as the actual propagation and season change. The algorithm of obtaining the weight vector of array antenna is proposed to improve this situation. We call the region where the coverage quality decreases as region to be optimized (RTBO). Mathematical model is established, with the objective function of maximizing the minimum SINR in RTBO and the constrains on the SINRs in the adjacent region. The nonconvex optimization problem is transformed into a convex optimization problem. An iterative algorithm is proposed so that the minimum SINR in RTBO can be maximized step by step. Simulation results show that the coverage effect of the proposed algorithm is better than those of the existing coverage control algorithms based on joint beamforming or joint antenna power adjusting.As the increase of viaducts, overpasses and high-rise buildings, the need of three-dimensional (3D) coverage increases. We propose the basic technical solution of3D coverage control with the3D beamforming of planar antenna. We focus on discussing the mathematical expressions of antenna pattern and the theory of least squares synthesis method for3D scenarios. Simulation results and discussions are given.