A policy based conflict resolution mechanism for MLB and MRO in LTE self-optimizing networks

Mobility Load Balancing (MLB) and Mobility Robustness Optimization (MRO) are two major SON (Self-Organizing Network) use cases specified for LTE (Long Term Evolution) by 3GPP (3rd Generation Partnership Project). MRO targets at optimizing the handover (HO) performance of the network by adjusting the HO point. Whereas, MLB reduces the congestion in traffic hotspots by advancing HOs from overloaded hotspot cells to less loaded neighbor cells. However, MLB degrades HO performance of the network because advanced HOs lead to worse SINR (Signal-to-Interference plus Noise Ratio) conditions with the target cells as compared to the original HO point. Hence, MLB can trigger MRO to optimize the HO performance and MRO can in turn trigger MLB to adjust the HO point for advanced HOs. Resultantly, MLB and MRO working in parallel can lead to oscillations. In this paper we present a policy based mechanism, termed as MLB-Static, which exploits users' mobility state to minimize the impact of MLB on HO performance and hence prevents oscillations. The simulation results, for a hexagonal LTE macro cellular deployment, show that MLB-Static has negligible impact on HO performance of the network as compared to conventional MLB while the gain of conventional MLB is preserved by MLB-Static.