Dynamic control of anchor carrier for dual-connectivity service

A cellular system comprising:

• a first access node;
• and
• a second access node,
• wherein the cellular system is configured to serve a plurality of user equipment devices (UEs) with dual connectivity, wherein each UE is served concurrently by the first access node on a respective first connection according to a first radio access technology (RAT) and by the second access node on a respective second connection according to a second RAT, wherein all of the UE's respective first connections have a first carrier as anchor carrier for the dual connectivity,
• wherein the cellular system is configured to detect, during the serving, that load on the first carrier is at least predefined threshold high, and
• wherein the cellular system is configured to respond to the detecting by (i) selecting one or more of the UEs based on each of the selected one or more UEs being within uplink range of the first access node on a second carrier higher in frequency than the first carrier and (ii) for each selected UE, reconfiguring the UE's respective first connection from having the first carrier as the anchor carrier for the dual connectivity to instead having the second carrier as the anchor carrier for dual connectivity.