Extending 5G to narrow spectrum allocations

Since its introduction, 5G New Radio has been a great success story, especially in the consumer markets. It offers low communication latency, high reliability, flexibility, and efficiency that further enable 5G networks to be used for mission critical applications. Currently, there are specialized networks serving industry verticals that would benefit from the 5G NR properties. Key use cases include communications for critical infrastructure such as railways, smart electrical power distribution grids, and public safety. These networks often use dedicated spectrum allocations that are narrower than the original minimum operating bandwidth of 5G NR. In this paper, we describe how new flexibility is being introduced into the 5G NR design as part of 5G Advanced to allow operation in these dedicated spectrum allocations with bandwidths between about 3 and 5 MHz. As a use case study, we focus on railway communications, and study the coexistence of the Global System for Mobile Communications Railway and Future Railway Mobile Communication System, FRMCS, based on NR during the decade-long migration period when both networks will have to be operational in parallel to ensure full serviceability of both old and new rolling stock. We discuss the changes required for the NR control channels and signaling and study the effect of the changes on the system performance via simulations.