Performance evaluation of handover in LTE-Advanced systems with pico cell Range Expansion

Cell Range Expansion (CRE) combined with Inter-Cell Interference Coordination (ICIC) in Heterogeneous Networks (HetNet) is a promising technique to enhance the utilization of the resource in pico cells. CRE increases the number of the UE sets connected to pico cells (pico UEs) by changing the trigger timing of the handover (HO). However, inappropriate trigger timing of HO increases HO failures and inefficient HOs, thereby degrading HO performance. HO performance directly affects the continuity of the communication service. Hence, not only the utilization of the resource in pico cells but HO performance should be taken into consideration when CRE is adopted. In this paper, we evaluate the effect of CRE on HO performance through system level simulations, and clarify the application range of CRE. As an example, we examine the CRE bias values which keep the HO failure rate to under 1% and the Ping-Pong HO rate to under about 1%. It is shown that the applicable CRE bias values range from 0 dB to 6 dB, which is smaller than the applicable CRE bias values reported by the conventional studies which range from 0 dB to 9 dB. We also show that the CRE bias values over 6 dB result in high HO failure rates over 5%. Therefore, CRE should be adopted with consideration of HO performance in order to keep good HO performance.