Communications using multiple radio access technologies (RAT) for a multi-mode user equipment (UE)

A method of operating a user equipment (UE), comprising:

• receiving, from a first base station using a first radio access technology (RAT), first configuration information for the UE to communicate with a second base station via a second RAT, wherein the first configuration information includes default configuration information received from the first base station using the first RAT and is further used to communicate with the second base station;
• receiving, from the first base station using the first RAT, a downlink message to enable a communication link between the UE and the second base station via the second RAT, wherein the downlink message is generated in response to a measurement report sent to the first base station based on a measurement performed by the UE to detect a service in the second RAT is available to the UE, the measurement report including an indication that the first configuration information is stored in the UE, and the downlink message includes second configuration information for the UE to communicate with the second base station via the second RAT;
• and
• establishing the communication link between the UE and the second base station using the second RAT based on a link configuration determined from the first configuration information and the second configuration information,
• wherein the second configuration information is received as a relative difference over the default configuration information, the second configuration information is of a smaller size than the default configuration information, and the second configuration information is to enable establishment of the communication link between the UE and second base station using the second RAT, and wherein the second RAT is a new radio (NR) RAT and the first RAT is different from the NR RAT.

A non-transitory computer-readable medium storing instructions that, when executed by a processor of a user equipment (UE), cause the UE to perform operations, the operations comprising:

• receiving, from a first base station using a first radio access technology (RAT), first configuration information for the UE to communicate with a second base station via a second RAT, wherein the first configuration information includes default configuration information received from the first base station using the first RAT and is further used to communicate with the second base station;
• receiving, from the first base station using the first RAT, a downlink message to enable a communication link between the UE and the second base station via the second RAT, wherein the downlink message is generated in response to a measurement report sent to the first base station based on a measurement performed by the UE to detect a service in the second RAT is available to the UE, the measurement report including an indication that the first configuration information is stored in the UE, and the downlink message includes second configuration information for the UE to communicate with the second base station via the second RAT;
• and
• establishing the communication link between the UE and the second base station using the second RAT based on a link configuration determined from the first configuration information and the second configuration information,
• wherein the second configuration information is received as a relative difference over the default configuration information, the second configuration information is of a smaller size than the default configuration information, and the second configuration information is to enable establishment of the communication link between the UE and second base station using the second RAT, and wherein the second RAT is a new radio (NR) RAT and the first RAT is different from the NR RAT.