Analysis of handover failures in HetNets with layer-3 filtering

Handover is one of the most critical functions in a cellular network and it supports the mobility of user equipments (UEs) across multiple cells. It is usually based on signal measurements from candidate base stations and filtering the signal measurements becomes necessary due to channel imperfections. In LTE, handover measurements are filtered using layer 3 (L3) filters in the UE, whereby the UE checks for the handover entry condition at discrete sampling instants of the L3 filter. The selection of sampling period becomes crucial in improving the handover performance of the network. Therefore, it is necessary to understand the trade-offs related to the sampling period of an L3 filter. The goal of this paper is to derive the handover failure (HF) expression as a function of L3 sampling periods in LTE. A geometric handover model is used for derivations and all analytical expressions are verified through simulations.