Dual-connectivity anchor-carrier selection based on transmission-mode support

A method to select an anchor carrier for dual-connectivity service of a user equipment device (UE), wherein the dual-connectivity service includes the UE being served concurrently by a master access node (MN) over a first air-interface connection and by a secondary access node (SN) over a second air-interface connection, and wherein the MN operates on a radio access technology and provides service on multiple carriers, the method comprising:

• determining, when the UE has the first air-interface connection with the MN, that the UE is within threshold poor coverage of the MN;
• selecting one of the multiple carriers to be the anchor carrier for the dual-connectivity service of the UE;
• and
• based at least on the determining that the UE is within the threshold poor coverage of the MN, basing the selecting on a transmission mode that the MN supports using on the selected carrier and that is selected from the group consisting of (i) transmit diversity, (ii) spatial multiplexing, and (iii) beamforming, wherein the transmission mode defines a manner in which the MN would provide downlink scheduled transmission on the selected carrier.

A first access node operable to control anchor carrier configuration for dual-connectivity service of a user equipment device (UE), wherein the dual-connectivity service includes the UE being served concurrently by the first access node over a first air-interface connection and by a second access node over a second air-interface connection, wherein the first access node operates on a radio access technology and provides service on multiple carriers, the first access node comprising:

• at least one wireless communication interface including an antenna structure through which to provide coverage and service;
• a backhaul communication interface through which to engage in backhaul communication;
• and
• a controller, wherein the controller causes the first access node to carry out operations including:
• determining, when the UE has the first air-interface connection with the first access node, that the UE is within threshold poor coverage of the first access node,
• selecting one of the multiple carriers to be the anchor carrier for the dual-connectivity service of the UE,
• based at least on the determining that the UE is within the threshold poor coverage of the first access node, basing the selecting on a transmission mode that the first access node supports using on the selected carrier and that is selected from the group consisting of (i) transmit diversity, (ii) spatial multiplexing, and (iii) beamforming, wherein the transmission mode defines a manner in which the first access node would provide downlink scheduled transmission on the selected carrier, and
• causing the selected carrier to be the anchor carrier for the dual-connectivity service of the UE.