User-centric Mobility Management Based on Virtual Cell in Ultra-Dense Networks

With the trend of network densification for providing high data rate, many problems including frequent measurement, intolerable handover failure (HOF) rate must be reckoned with in Ultra-Dense Networks (UDNs). Moreover, dense deployment of small cells implies that paging has a low probability to be successful in the first attempt, which increases the signaling overhead in the Core Network (CN). To solve this problem, a novel handover scheme using Virtual Cell (VC) design based on local anchor is proposed for senseless moving in UDNs, thus building a virtualized network. The local anchor cell controls the working procedure of corresponding VC and anchors the handover within a VC and between VCs. Besides, split bearers are applied for local anchor-based architecture. Moreover, Virtual Physical Cell ID (VPCI) and Virtual Reference Signal (VRS) for VC design are given in our scheme. The VPCI assignment is based on the locally available information like Physical Cell ID (PCI). We take intra-cluster (intra-VC) and inter-cluster (inter-VC) handover process into consideration. Simulation based performance analysis showed spectral efficiency gains up to 11% and a handover failure reduction by more than 50% when compared to handover in traditional LTE system.