Dual handover triggers to improve QoE for indoor and outdoor mobility

The use of mobile data is rapidly increasing along with the popularity of smartphones and tablets. The use of indoor data, especially, is expected to be further increased. Indoor cell evolved Node Bs (eNBs) are being installed and they are expected to increase the areas overlaid by indoor and outdoor cells to offload indoor mobile data. We confirmed increases in the handover (HO) failure rates from our analysis of field measurements due to rapid drops in communication quality when user equipment (UE) moved through the doors of a building. If HO failure occurred, the quality of experience (QoE) for real-time applications, e.g., voice over Internet protocol (VoIP) and streaming, degraded due to service interruptions and rebuffering. Thus, it was important to reduce the HO failure rates and disconnection times due to HO failure. We propose a scheme of dual HO triggers that improves the performance of HO from/to an indoor cell while maintaining that of HO between outdoor cells. The proposed scheme introduces events to UE measurement reports to detect rapid drops in communication quality in addition to conventional events that are optimized to the HO between outdoor cells. LTE simulations confirmed that the new HO trigger prevented UE from going out-of-synchronization before the completion of the HO process. The simulation results indicated that the proposed scheme improved indoor-cell-related QoE. More specifically, the number of dropped calls reduced by 87%, the number of service interruptions for VoIP reduced by 92%, and the HO failure rate reduced by 23 points. Moreover, the proposed scheme also improved outdoor-cell-related QoE. In short, it significantly improved QoE by reducing HO failure rates in indoor and outdoor cell environments.