Mobility Management in Ultra-Dense Networks: Handover Skipping Techniques

Ultra-dense network deployment is a key technology for potentially achieving the capacity target of next-generation wireless communication systems. However, such a deployment results in cell proliferation and cell size decrement, leading to an increased number of handovers and limited sojourn time within a cell, which severely degrade the user's quality of service (QoS). In this paper, we propose two intelligent handover skipping techniques to overcome the high handover rates. The first technique considers a user associated with a single base station (BS) and the decision to skip a handover is based on the upcoming cell's topology; we consider three criteria: 1) the area of the cell; 2) the trajectory distance within the cell; and 3) the distance of the BS from the cell edge. The second technique exploits BS cooperation and enables a dynamic handover skipping scheme, where the skipping decision is taken based on the BSs of three consecutive cells in the user's trajectory. This technique achieves a balance between BS cooperation and single BS transmission and manages to maintain a good QoS during the skipping phase. We show that the proposed techniques reduce both the handover rate and handover cost and outperform the conventional techniques for moderate to high-velocity values.