A Blackout Aware Handover Mechanism for Ultra Dense Networks

Article Type

Research Article

Publication Title

Journal of Network and Systems Management


In macrocell to small cell switching, the handover decision is deferred until A3 event occurs, i.e., the reference signal received power (RSRP) from serving macro cell falls below a predefined threshold. Since, RSRP can not measure the user perceived throughput precisely, the data rate perceived from the macrocell may fall below the requested data rate prior to handover. We refer to this period as black‘out period. In ultra dense network (UDN) scenario, mobile terminals (MTs) usually prefer to remain connected to the macrocells as the transmitting powers of macrocells are much higher than small cells. As a result, the MTs cannot utilize the offloading capacity of the small cells in hotspot areas predominantly. This makes the problem of blackout period more severe. The existing handover mechanisms cannot deal with the blackout period adequately. In this work, we propose a handover decision metric namely service goodness which is computed based on precise throughput estimation. Such throughput estimation considers medium access control (MAC) scheduling details as well as the fluctuation of interference level in UDN scenario. Simulation results confirm that our proposed service goodness based handover algorithm outperforms the existing handover mechanisms. Furthermore, to minimize the duration of blackout period, we also propose a soft handover technique (SHT) which combines the data rates received from multiple access networks using dual connectivity support. The superiority of SHT over semisoft handover has been established through Markov model based analysis and simulation.



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