Yunjung Yi

A novel handover scheme to support small-cell users in a HetNet environment

Deployment of small cells is one of the most efficient solutions to improve the energy efficiency in mobile communication networks. However, small cell topology has a disadvantage such as frequent handovers of mobile user equipments (UEs). To solve this handover problem for small-cell users in a HetNet environment, we propose a novel handover scheme utilizing a cooperation-based cell clustering scheme for reducing handover overhead in core network (CN) and also signaling overhead among small cells. When a UE in active mode moves randomly, we can significantly reduce the handover ratio through the proposed scheme, compared with that of the conventional schemes. In particular, if the UE speed is 3 km/h, this ratio is approximately 0.07.

Design of a multi-variable QoE function based on the remaining battery energy

Recently, study on designing a new metric to express quality of experience (QoE) has attracted attention since user satisfaction may be different according to the types of served traffic. The utility function for various traffic has been studied for many years and most of the previous work focused on the utility functions with respect to a single performance metric such as throughput. However, multiple performance metrics may affect user satisfaction according to user properties or situations. One of critical factors that affect the sensitivity of user satisfaction is the remaining battery energy. In this paper, we investigate the characteristics of the user satisfaction with respect to throughput and energy efficiency considering the remaining battery energy. Based on the characteristics, we design a multi-variable QoE function based on the unified utility, especially, considering users remaining battery energy and verify the feasibility of the proposed multi-variable QoE function through numerical results.