Self-optimization of handover parameters for dynamic small-cell networks

Seamless handover is an essential feature of cellular networks. For small-cell networks, effective handover becomes particularly challenging. If some cells may be activated and deactivated dynamically, effective handover handling will become even more difficult. A key factor of good handover performance is handover timing, that is, making handover decision at a right time. If handover is executed too early or too late, users will experience temporary link disconnection, called radio link failure (RLF). Handover timing is controlled by handover parameters, which are set by the network. RLF prevention is directly related to the proper configuration of these parameters. In this paper, we propose a self-optimization scheme that adjusts the handover parameters to minimize RLFs for dynamic small-cell networks. Our scheme first detects the types of RLF and then adjusts the handover parameters according to the types of RLF. Unlike most existing schemes, our scheme adjusts both system common parameters and cell-specific parameters together. In certain situations, such as when two adjacent cells do not have sufficient coverage overlap, RLFs may not be reduced to a satisfactory level by the handover parameter adjustment alone. To deal with such a case, our scheme adjusts the cell coverage in conjunction with the handover parameter optimization. The simulation results show that the proposed scheme can virtually eliminate RLFs. Copyright (c) 2013 John Wiley & Sons, Ltd.