Unnecessary Handover Minimization in Two-Tier Heterogeneous Networks

Ultra-dense deployment of small cells (SC) can be foreseen in 5G network under the coverage area of the macrocell (MC). A mobile user equipment (UE) should be able to discover adjacent SCs to perform the handover (HO). This process can be done by frequent neighbour cell scanning. However, extensive scanning for every SC in a dense deployment scenario is a resource wasting strategy, which results in a power dissipation of the UE battery and also lowers the throughput gain. This also means that a high number of SCs would be available for the UE to HO to. Hence, the probability of unnecessary HO will increase and in turn degrade the UE's quality of service (QoS). This paper aims to minimize unnecessary HOs in two tier heterogeneous network with dense deployment of SCs. In the proposed method, we utilise the actual distance between the UE and the SCs and the UE angle of movement to construct a shortened candidate list which helps in reducing the signal overhead of scanning and the number of unnecessary HOs. UE's movement velocity threshold based on average human walking speed is used to control the HO to the SC. Simulation results show that the proposed algorithm outperformed the conventional HO method with reduced unnecessary HOs and increased throughput for the network particularly for medium to high speed UEs resulting in good UE QoS.