Methods and apparatuses for configuring radio terminal with numerology of second RAT via first RAT

1. A second radio access network (RAN) node to be used in a radio communication system that supports a first Radio Access Technology (RAT) and a second RAT, the second RAN node being associated with the second RAT, the second RAN node comprising:

a memory; and

at least one processor coupled to the memory and configured to:

notify a first RAN node associated with the first RAT of a reference numerology that is included in multiple numerologies supported by the second RAT, in a setup procedure of an inter-RAN node interface between the first RAN node and the second RAN node; and

send a radio resource configuration of the second RAT to a radio terminal via the first RAN node, wherein

the radio resource configuration indicates at least one numerology different from the reference numerology.

2. The second RAN node according to claim 1 , wherein each numerology includes at least one of subcarrier spacing, system bandwidth, a Transmission Time Interval length, subframe duration, slot duration, the number of slots per subframe, a Cyclic prefix length, symbol duration, and the number of symbols per subframe.

3. The second RAN node according to claim 1 , wherein the at least one processor is configured to generate the radio resource configuration for dual connectivity that uses the first RAT as a primary RAT and the second RAT as a secondary RAT.

4. The second RAN node according to claim 3 , wherein the at least one processor is configured to receive a radio bearer setup request from the first RAN node, select at least one numerology according to requirements for a radio bearer of the second RAT indicated by the radio bearer setup request, and include in the radio resource configuration an information element explicitly or implicitly indicating the selected at least one numerology.

5. The second RAN node according to claim 1 , wherein the at least one processor is configured to generate the radio resource configuration for an Inter-RAT handover of the radio terminal from the first RAT to the second RAT.

6. The second RAN node according to claim 1 , wherein the reference numerology defines a reference subframe configuration for a carrier that the second RAT supports.

7. The second RAN node according to claim 6 , wherein the at least one processor is configured to send to the radio terminal, via the first RAN node, a measurement configuration of at least one cell provided by the second RAN node on the carrier according to the reference numerology.

8. A first radio access network (RAN) node to be used in a radio communication system that supports a first Radio Access Technology (RAT) and a second RAT, the first RAN node being associated with the first RAT, the first RAN node comprising:

a memory; and

at least one processor coupled to the memory and configured to;

receive a reference numerology that is included in multiple numerologies supported by the second RAT, from a second RAN node associated with the second RAT, in a setup procedure of an inter-RAN node interface between the first RAN node and the second RAN node;

receive a radio resource configuration of the second RAT from the second RAN node; and

send the radio resource configuration to a radio terminal, wherein

the radio resource configuration indicates at least one numerology different from the reference numerology.

9. The first RAN node according to claim 8 , wherein the reference numerology defines a reference subframe configuration for a carrier that the second RAT supports.

10. The first RAN node according to claim 9 , wherein the at least one processor is configured to send, to the radio terminal, a measurement configuration of at least one cell provided by the second RAN node on the carrier according to the reference numerology.

11. A radio terminal to be used in a radio communication system that supports a first Radio Access Technology (RAT) and a second RAT, the radio terminal comprising:

at least one wireless transceiver configured to communicate with a first radio access network (RAN) node associated with the first RAT and communicate with a second RAN node associated with the second RAT; and

at least one processor configured to receive a radio resource configuration of the second RAT from the second RAN node via the first RAN node, wherein

a reference numerology that is included in multiple numerologies supported by the second RAT is sent from the second RAN node to the first RAN node in a setup procedure of an inter-RAN node interface between the first RAN node and the second RAN node, and

the radio resource configuration indicates at least one numerology different from the reference numerology.

12. The radio terminal according to claim 11 , wherein each numerology includes at least one of subcarrier spacing, system bandwidth, a Transmission Time Interval length, subframe duration, slot duration, the number of slots per subframe, a Cyclic prefix length, symbol duration, and the number of symbols per subframe.

13. The radio terminal according to claim 11 , wherein the at least one processor is configured to receive the radio resource configuration for dual connectivity that uses the first RAT as a primary RAT and the second RAT as a secondary RAT.

14. The radio terminal according to claim 11 , wherein the at least one processor is configured to receive the radio resource configuration for an Inter-RAT handover of the radio terminal from the first RAT to the second RAT.

15. The radio terminal according to claim 11 , wherein the reference numerology defines a reference subframe configuration for a carrier that the second RAT supports.

16. A method for a second radio access network (RAN) node used in a radio communication system that supports a first Radio Access Technology (RAT) and a second RAT, the second RAN node being associated with the second RAT, the method comprising:

notifying a first RAN node associated with the first RAT of a reference numerology that is included in multiple numerologies supported by the second RAT, in a setup procedure of an inter-RAN node interface between the first RAN node and the second RAN node; and

sending a radio resource configuration of the second RAT to a radio terminal via the first RAN node, wherein

the radio resource configuration explicitly or implicitly indicates at least one numerology different from the reference numerology.

17. A method for a first radio access network (RAN) node used in a radio communication system that supports a first Radio Access Technology (RAT) and a second RAT, the first RAN node being associated with the first RAT, the method comprising:

receiving a reference numerology that is included in multiple numerologies supported by the second RAT, from a second RAN node associated with the second RAT, in a setup procedure of an inter-RAN node interface between the first RAN node and the second RAN node;

receiving a radio resource configuration of the second RAT from the second RAN node; and

sending the radio resource configuration to a radio terminal, wherein

the radio resource configuration indicates at least one numerology different from the reference numerology.

18. A method for a radio terminal used in a radio communication system that supports a first Radio Access Technology (RAT) and a second RAT, the method comprising:

receiving a radio resource configuration of the second RAT from a second radio access network (RAN) node associated with the second RAT via a first RAN node associated with the first RAT, wherein

a reference numerology that is included in multiple numerologies supported by the second RAT is sent from the second RAN node to the first RAN node in a setup procedure of an inter-RAN node interface between the first RAN node and the second RAN node, and

the radio resource configuration indicates at least one numerology different from the reference numerology.