  With wireless communication technology development, the 5G New Radio (NR) has
been proposed and developed for a decade. This advanced mobile communication
technology has more advancements, such as higher system capacity, higher
spectrum efficiency, higher data rates, and so on. In 5G, Ultra- Dense Network
(UDN) is deployed for increasing the system capacity and frequency reuse to
meet high application requirements. The architecture of 5G UDN is to realize
the dense and flexible deployment of smaller general Node B (gNB). However, the
increased capacity of applying UDN in 5G is anticipated at the cost of
increased signal interference, increased handover times, and increased handover
failures. The Time to Trigger (TTT) is one of the most important factors in
handover frequency which is deserved to be detected. Moreover, the density of
the 5G gNBs influences the handover times and performance as well. In this
work, we provide a compendium of 5G handover management. A downlink
system-level simulator for 5G handover is built and utilized to evaluate the
effect of different TTT values and densities of gNBs on the 5G handover. In
addition, different velocities of Traffic Users (TUs) have been applied to the
simulation system. From the simulation results, the handover performance has
been analyzed and optimized by applying adjustable TTT under different
densities of gNBs which will help people have a better understanding of the
selection and effect of proper TTT, UDN, and different velocities of TUs on 5G
handover performance.
