Measurement of Inter-Frequency Small Cell in Heterogeneous Networks

Inter-frequency small cell deployments on hotspot locations are seen as a potential solution to offload macro user traffic to small cells. In order to discover inter-frequency small cells, macro user equipments (UE) are required to perform gap-assisted measurement. The currently existing short measurement periods can increase offloading, but at low UE speeds, it leads to unnecessarily measurement to scan neighbor cells and results in waste of UE battery. Long measurement periods are discussed in 3GPP to reduce UE power consumption. However, due to long measurement periods and consequently delayed cell discovery, inter-frequency mobility and offloading performance are degraded, especially at UE high speeds. In this paper, it is shown using simulation that mobility performance and the small cell dwelling time are degraded at high UE speeds when adopting the long measurement periods. Based the simulation results, it is proposed that applying the long measurement period is effective for low mobility UE to reduce the UE power consumption while keeping the acceptable handover failure rate and the offloading performance.