Soft Metric Assisted Mobility Robustness Optimization in LTE Networks

Mobility Robustness Optimization (MRO) is a use-case of Self-Organizing Networks (SON) for LTE that aims to optimize handover performance automatically. Conventional MRO algorithms tune handover parameters based on counts of handover failures and handover events. The algorithm requires many handovers per cell pair (e.g. 1000) to trigger a reliable adjustment. Thus it can result in a slow adaptation to changes that improve or deteriorate handover performance, such as network loading or UE speed. In this paper, we propose a new MRO algorithm taking into account soft metrics, such as handover command transmission time, derived both from failed and successful handovers. The proposed algorithm provides a faster reaction and lower failure rate than the conventional method, with no deterioration in the handover count.