National roaming as a fallback or default?

Mobile network operators (MNOs) in a country operate independent of each other, although inter-operator collaboration such as national roaming (NR) can offer benefits in terms of resilience, coverage, throughput, and energy efficiency. In some countries, regulations impose realization of national roaming as a fallback strategy, e.g., when an operator cannot offer sufficient coverage while the other can. However, tighter inter-operator collaboration can unlock even more opportunities. In this work, we quantify the benefits in terms of coverage, capacity, and power consumption that can be gained by national roaming as a fallback strategy and as a default strategy wherein all MNOs are operated as a single network. We use public data from national bodies in the Netherlands to study the gains for the Dutch MNOs and investigate the resilience gain also under random failures of base stations, e.g., due to hardware or software errors. Our analysis shows that all MNOs can benefit from a tight cooperation reflected in lower fraction of disconnected population, higher fraction of satisfied population, and lower power consumption for transmission. Despite not offering the same level of benefits, NR as a fallback strategy can also offer gains, in particular for MNOs with less ubiquitous network deployment. Moreover, in comparison to no cooperation, both cooperation approaches provide resilience to isolated failures and result in less severe performance degradation.