Methods, systems, and processing nodes for ensuring uplink service for wireless devices capable of uplink split mode in EN-DC using both 4G LTE and 5G NR RATs, by selecting serving access nodes that are also capable of uplink split mode and/or coupled to large quantities of antenna elements relative to other potential serving access nodes. In particular, such serving access nodes are selected for wireless devices that exhibit one or more of a low power headroom, a high uplink buffer, or a high mobility.