Spectrum Aggregation for 6G: Lessons from 5G Carrier Aggregation and Dual Connectivity

Abstract

Spectrum aggregation has been a key enabler of LTE and 5G capacity growth, but it will become even more fundamental in 6G as networks expand across low bands, existing mid bands, new upper-mid/centimetric bands, and millimeter wave bands. This article examines how 5G carrier aggregation (CA) and dual connectivity (DC) inform the design of 6G spectrum aggregation. We argue that, while DC was instrumental in accelerating early non-standalone 5G deployment, it also introduced architectural fragmentation and long-term migration complexity. In contrast, CA provides a cleaner and more scalable foundation for multi-band operation in standalone 6G. Building on lessons from 5G, we advocate enhanced CA as the preferred 6G aggregation framework and point out the corresponding key enhancement directions.