By Ricardo Omana, Ericsson Inc.
The deployment of mobile service should be viewed as an evolution that builds on all spectrum assets, either licensed or unlicensed. Multiple-Systems Operators (MSOs) need to be able to make the best use of the performance characteristics of both 4G LTE and 5G NR technologies across all available spectrum to support their business strategies while maintaining coexistence between all the technologies deployed in the network.
In addition, the MSOs that deploy 4G LTE will need a seamless way to migrate their networks to 5G with minimum disruption to their day-to-day operations and customer experience. Spectrum sharing is one key aspect that must be considered as part of the evolution of mobile networks from LTE to 5G NR, allowing the combination of technologies and spectrum assets, as well as handling both legacy device fleet while 5G NR devices are on the rise.
The key design principles of spectrum sharing are (a) avoid inefficient spectrum utilization when there is low penetration of 5G NR devices (b) maximize LTE and 5G NR down link peak rates (c) best possible user experience everywhere (d) largest possible 5G NR footprint as well as smooth introduction of 5G NR in an existing 4G network.
This paper shall consider the fact that each spectrum band has different physical properties, meaning there are trade-offs between capacity, coverage, and latency, as well as reliability and spectral efficiency. These trade-offs need to be taken into consideration when planning 5G NR deployments, especially with regards to the MSOs service focus, whether this is enhanced Mobile Broadband, Massive IoT, Critical IoT or Fixed Wireless Access.
Today standards offer a framework of functionalities, for example, dual connectivity between LTE and 5G NR and inter-band carrier aggregation. However, there are additional opportunities for innovation when it comes to mobile spectrum and technology generations which will be examined in this paper.