Research On Mobility Managements For The 5^th Generation Networks

With the 5th generation network becoming more heterogeneous and densly deployed, the convergence and interworking of various technologies and services is seen as the target of network evolution.Meanwhile, the architecture of mobility managements is facing with breakthrough innovations and no longer limited to the single moving UE-fixed eNB communication mode. Moving service provider and dynamic communication mode are becoming the critical extensions of mobility managements. Therefore, this thesis focuses on the mobility managements for the 5G networks and the main research content are summarized as follows:In ultra dense and heterogeneous networks, the handover shows worse performance in terms of handover failure rate and ping-pong handover rate. Therefore, we propose a Device-to-Device (D2D) assisted handover enhancements solution to cope with the problems. First, we model the network deployment, channel state, Macro-Pico-Macro Ping-Pong (MPM PP) handover and Pico to Macro Handover Failure(P2M HOF) based on the stochastic geometry. We then make theoretical analyses on the enhancements of MPM PP rate and P2M HOF rate.Furthermore, we propose the detailed implementation methods for the proposed solution, including the relay UE selection, trigger event for UE-to-Network Relay and enhanced handover signaling. Finally,simulations verify that the MPM PP rate and P2M HOF rate in mobility managements can be decreased simultaneously by the proposed scheme.Towards the various communication mode in 5G network and the demand of mobility management development at the User Equipment(UE), we make theoretical analyses on D2D mode transition in moving D2D enabled cellular networks. First, we model the network deployment,received signals and user movement based on the stochastic geometry.We deduced that the D2D communication range can be well represented by biased circles with varying radius. Besides, a tractable analytical framework considering both absolute movement and relative movement for mode selection in moving D2D scenarios is presented. Under the proposed model, closedform expressions of D2D mode transition rate and D2D mode residence time are derived, which are key parameters for moving D2D mode selection performance. These analytical results can provide fundamental supports for further proximity service enhancements.Moving Relays (MRs) have been proposed as a promising technology to improve the coverage performance of vehicular users.However, how MRs can influence non-vehicular users is not yet studied.Therefore, in this thesis, we make statistical analyses on the coverage performance of non-vehicular users in the MR enabled cellular networks.We develop an analytical framework for analyzing downlink signal-to-interference ratio (SINR) under the presence of MRs. Under the proposed framework, tractable expressions for coverage probability of nonvehicular users connecting to MRs and Macro Base Stations (MBSs)are derived respectively. These analytical results show that non-vehicular users can improve their coverage performance by handover to moving relays for communications.In summary, this thesis studies the mobility management technology for the UE, network and mobile relay scenarios respectively. The research results can provide fundamental supports for mobility management evolution of 5G networks.