The rapid growth and innovation of the various mobile communication technologies have caused a change in the paradigm of Internet access. In next-generation mobile system, which is also known as fifth-generation (5G) network, all user connections are expected to be heterogeneous in nature. Hence, an intelligent mobility management mechanism is essential to satisfy the requirements of lower latency, less power consumptions, and last but not least, possible uninterrupted ongoing session when a user equipment (UE) moves across network boundaries.On the other hand, device-to-device (D2D) communication has been proposed as a promising technology to boost the network performance in 5G. The issue related to mobility management for D2D communication in 5G heterogeneous network environments has attracted attention from academic society. In this paper, we leverage on IEEE 802.21 Media Independent Service (MIS) and propose a new framework, enhanced version of IEEE 802.21 MIS that supports D2D communication (E-MIS-D2D) to enhance D2D mobility experience over heterogeneous networks. Moreover, a load-aware mode selection algorithm is proposed for selecting the best target mode. Through extensive simulation studies, we validate that the proposed method outperforms the existing methods in terms of packet loss ratio, average throughput, latency, bandwidth usage, and load rate of Evolved Node B (eNB).
KEYWORDSdevice-to-device, heterogeneous networks, load-aware, media independent service, mobility management
INTRODUCTIONThe improved multimedia availability and the rapid development of smart devices have resulted in the explosive growth of mobile traffic that constantly challenge inherently limited network resources in currently available IMT-Advanced/4G networks. According to an Ericson Mobility Report 2017, mobile subscriptions will rise to 9.12 billion by year 2023. 1 To handle such explosive growth of traffic volume, the quest for the 5G mobile communication standards has been going on actively recently, and one of the major focuses of this quest is to obtain a device-centric network architecture. 2 D2D communication with its nature of proximity-based service and enhancements on network capacity and spectrum efficiency has been viewed as a key component in 5G. By using D2D communication, one device enables to communicate with another device directly without the supports from a major infrastructure. However, the implementation of D2D communications faces a number of challenges. One big issue is the mobility management problem caused by D2D communications when a user in D2D pair moves across network boundaries, especially in heterogeneous network scenarios. Mobility management for any wireless communication systems has been regarded as the high-priority issue. However, the research on mobility management for D2D communication is in an early stage so far, and it is still an open question.In this paper, we focus on the IEEE 802.21 specified MIS 3 and point out ways to enhance the mobility experience of D2D communication users in he...