System and method to enable multiple base reference configurations for layer 1/LAYER2 triggered mobility in a telecommunications network

1 . A system comprising:

at least one memory storing instructions; and

at least one processor configured to execute the instructions to:

receive, by a Central Unit (gNB-CU) from a serving Distributed Unit (serving gNB-DU), a first base reference configuration and an indicator indicating an association between a type and/or characteristics of a first cell and the first base reference configuration, wherein the serving gNB-DU supports the first cell having a first layer1/layer2 triggered mobility (LTM) cell configuration corresponding to the first base reference configuration, the first cell being a serving cell for a user equipment (UE), and wherein the gNB-CU maintains multiple base reference configurations associated with types and characteristics of a plurality of candidate cells;

send, by the gNB-CU during candidate cell configuration preparation, the first base reference configuration or an indication to provide a new reference configuration to a target Distributed Unit (target gNB-DU), wherein the target gNB-DU supports a second cell to be prepared as a LTM candidate cell for an LTM handover;

determine, by the target gNB-DU, whether the first base reference configuration is usable with a delta configuration to obtain a full second cell configuration for the second cell; and

based on determining that the first base reference configuration is not usable to obtain the second cell configuration, send, by the target gNB-DU to the gNB-CU, a second base reference configuration corresponding to the second cell configuration.

2 . The system as claimed in claim 1 , wherein the least one processor is further configured to execute the instructions to:

based on determining that the first base reference configuration is not usable to obtain the second cell configuration, send, by the target gNB-DU to the gNB-CU, an indicator indicating an association between a type and/or characteristics of LTM candidate cells of the target gNB-DU and the second base reference configuration,

wherein a first full cell configuration for the first cell corresponds to an association of the first base reference configuration and a first delta, and a second full cell configuration for the second cell corresponds to an association of the second base reference configuration and a second delta.

3 . The system as claimed in claim 1 , wherein the least one processor is further configured to execute the instructions to:

based on a decision to prepare an inter gNB-DU LTM candidate cell, send, by the gNB-CU, a user equipment (UE) context setup or modification request to the serving gNB-DU via an F1 interface;

based on the request, receive, by the gNB-CU, a UE context modification response from the serving gNB-DU via the F1 interface, wherein the UE context modification response comprises the first base reference configuration; and

based on the UE context setup or modification response, send, by the gNB-CU, a UE context setup request to the target gNB-DU via the F1 interface, wherein the UE context setup request comprises the first base reference configuration, and wherein the target gNB-DU derives a second full cell configuration for the second cell using a second delta and one of the first base reference configuration or the second base reference configuration.

4 . The system as claimed in claim 1 , wherein the at least one processor is further configured to execute the instructions to:

send, by the target gNB-DU, a UE context setup response to the gNB-CU via the F1 interface, wherein the UE context setup response comprises the second base reference configuration;

assign, by the gNB-CU, mappings of base reference configurations and type and/or characteristics of LTM candidate cells, the mappings comprising a mapping between the first base reference configuration and the first cell and a mapping between the second base reference configuration and the second cell; and

send, by the gNB-CU to the UE via the serving gNB-DU, a radio resource control (RRC) reconfiguration message, the RRC reconfiguration message indicating the mappings.

5 . The system as claimed in claim 4 , wherein the at least one processor is further configured to execute the instructions to:

receive, by the serving gNB-DU, an Intra-or Inter-Frequency Layer 1 (L1) measurement report from the UE;

based on the Intra-or Inter-Frequency L1 measurement report, determine, by the serving gNB-DU, to perform a serving cell change; and

send, by the serving gNB-DU, a Medium Access Control (MAC) Control Element (CE) comprising a serving cell change command to the UE indicating a change to one of the LTM candidate cells,

wherein a full LTM candidate cell configuration is obtained by the UE based on a base reference configuration and a delta configuration of the one of the LTM candidate cells, the base reference configuration being determined from the mappings included in the RRC Reconfiguration message.

6 . The system as claimed in claim 5 , wherein the at least one processor is further configured to execute the instructions to:

determine, by the gNB-CU, associations between each base reference configuration and a type of corresponding target cell(s) and/or target gNB-DU(s); and

determine, by the gNB-CU and based on the associations, an appropriate base reference configuration to send to a candidate/target gNB-DU according to a type and/or characteristics of the candidate/target gNB-DU, to prepare an inter gNB-DU LTM candidate cell hosted by the candidate/target gNB-DU.

7 . The system as claimed in claim 6 , wherein the type and/or characteristics of a LTM candidate cell comprises at least one of a cell frequency, a gNB-DU capability, a supported feature set and a cell size.

8 . A method comprising:

receiving, by a Central Unit (gNB-CU) from a serving Distributed Unit (serving gNB-DU), a first base reference configuration and an indicator indicating an association between a type and/or characteristics of a first cell and the first base reference configuration, wherein the serving gNB-DU supports the first cell having a first layer1/layer2 triggered mobility (LTM) cell configuration corresponding to the first base reference configuration, the first cell being a serving cell for a user equipment (UE), and wherein the gNB-CU maintains multiple base reference configurations associated with types and characteristics of a plurality of candidate cells;

sending, by the gNB-CU during candidate cell configuration preparation, the first base reference configuration or an indication to provide a new reference configuration to a target Distributed Unit (target gNB-DU), wherein the target gNB-DU supports a second cell to be prepared as a LTM candidate cell for an LTM handover;

determining, by the target gNB-DU, whether the first base reference configuration is usable with a delta configuration to obtain a full second cell configuration for the second cell; and

based on determining that the first base reference configuration is not usable to obtain the second cell configuration, sending, by the target gNB-DU to the gNB-CU, a second base reference configuration corresponding to the second cell configuration.

9 . The method as claimed in claim 8 , wherein the method further comprises:

based on determining that the first base reference configuration is not usable to obtain the second cell configuration, sending, by the target gNB-DU to the gNB-CU, an indicator indicating an association between a type and/or characteristics of LTM candidate cells of the target gNB-DU and the second base reference configuration,

wherein a first full cell configuration for the first cell corresponds to an association of the first base reference configuration and a first delta, and a second full cell configuration for the second cell corresponds to an association of the second base reference configuration and a second delta.

10 . The method as claimed in claim 8 , wherein the method further comprises:

based on a decision to prepare an inter gNB-DU LTM candidate cell, sending, by the gNB-CU, a user equipment (UE) context setup or modification request to the serving gNB-DU via an F1 interface;

based on the request, receiving, by the gNB-CU, a UE context modification response from the serving gNB-DU via the F1 interface, wherein the UE context modification response comprises the first base reference configuration; and

based on the UE context setup or modification response, sending, by the gNB-CU, a UE context setup request to the target gNB-DU via the F1 interface, wherein the UE context setup request comprises the first base reference configuration, and wherein the target gNB-DU derives a second full cell configuration for the second cell using a second delta and one of the first base reference configuration or the second base reference configuration.

11 . The method as claimed in claim 10 , wherein the method further comprises:

sending, by the target gNB-DU, a UE context setup response to the gNB-CU via the F1 interface, wherein the UE context setup response comprises the second base reference configuration;

assigning, by the gNB-CU, mappings of base reference configurations and type and/or characteristics of LTM candidate cells, the mappings comprising a mapping between the first base reference configuration and the first cell and a mapping between the second base reference configuration and the second cell; and

sending, by the gNB-CU to the UE via the serving gNB-DU, a radio resource control (RRC) reconfiguration message, the RRC reconfiguration message indicating the mappings.

12 . The method as claimed in claim 11 , wherein the method further comprises:

receiving, by the serving gNB-DU, an Intra-or Inter-Frequency Layer 1 (L1) measurement report from the UE;

based on the Intra-or Inter-Frequency L1 measurement report, determining, by the serving gNB-DU, to perform a serving cell change; and

sending, by the serving gNB-DU, a Medium Access Control (MAC) Control Element (CE) comprising a serving cell change command to the UE indicating a change to one of the LTM candidate cells,

wherein a full LTM candidate cell configuration is obtained by the UE based on a base reference configuration and a delta configuration of the one of the LTM candidate cells, the base reference configuration being determined from the mappings included in the RRC Reconfiguration message.

13 . The method as claimed in claim 12 , wherein the method further comprises:

determining, by the gNB-CU, associations between each base reference configuration and a type of corresponding target cell(s) and/or target gNB-DU(s); and

determining, by the gNB-CU and based on the associations, an appropriate base reference configuration to send to a candidate/target gNB-DU according to a type and/or characteristics of the candidate/target gNB-DU, to prepare an inter gNB-DU LTM candidate cell hosted by the candidate/target gNB-DU.

14 . The method as claimed in claim 13 , wherein the type and/or characteristics of a LTM candidate cell comprises at least one of a cell frequency, a gNB-DU capability, a supported feature set and a cell size.

15 . A non-transitory computer-readable recording medium having recorded thereon instructions executable by at least one processor to cause the at least one processor to perform a method comprising:

receiving, by a Central Unit (gNB-CU) from a serving Distributed Unit (serving gNB-DU), a first base reference configuration and an indicator indicating an association between a type and/or characteristics of a first cell and the first base reference configuration, wherein the serving gNB-DU supports the first cell having a first layer1/layer2 triggered mobility (LTM) cell configuration corresponding to the first base reference configuration, the first cell being a serving cell for a user equipment (UE), and wherein the gNB-CU maintains multiple base reference configurations associated with types and characteristics of a plurality of candidate cells;

sending, by the gNB-CU during candidate cell configuration preparation, the first base reference configuration or an indication to provide a new reference configuration to a target Distributed Unit (target gNB-DU), wherein the target gNB-DU supports a second cell to be prepared as a LTM candidate cell for an LTM handover;

determining, by the target gNB-DU, whether the first base reference configuration is usable with a delta configuration to obtain a full second cell configuration for the second cell; and

based on determining that the first base reference configuration is not usable to obtain the second cell configuration, sending, by the target gNB-DU to the gNB-CU, a second base reference configuration corresponding to the second cell configuration.

16 . The non-transitory computer-readable recording medium according to claim 15 ,

wherein the method further comprises:

based on determining that the first base reference configuration is not usable to obtain the second cell configuration, sending, by the target gNB-DU to the gNB-CU, an indicator indicating an association between a type and/or characteristics of LTM candidate cells of the target gNB-DU and the second base reference configuration,

wherein a first full cell configuration for the first cell corresponds to an association of the first base reference configuration and a first delta, and a second full cell configuration for the second cell corresponds to an association of the second base reference configuration and a second delta.

17 . The non-transitory computer-readable recording medium according to claim 15 ,

wherein the method further comprises:

based on a decision to prepare an inter gNB-DU LTM candidate cell, sending, by the gNB-CU, a user equipment (UE) context setup or modification request to the serving gNB-DU via an F1 interface;

based on the request, receiving, by the gNB-CU, a UE context modification response from the serving gNB-DU via the F1 interface, wherein the UE context modification response comprises the first base reference configuration; and

based on the UE context setup or modification response, sending, by the gNB-CU, a UE context setup request to the target gNB-DU via the F1 interface, wherein the UE context setup request comprises the first base reference configuration, and wherein the target gNB-DU derives a second full cell configuration for the second cell using a second delta and one of the first base reference configuration or the second base reference configuration.

18 . The non-transitory computer-readable recording medium according to claim 17 ,

wherein the method further comprises:

sending, by the target gNB-DU, a UE context setup response to the gNB-CU via the F 1 interface, wherein the UE context setup response comprises the second base reference configuration;

assigning, by the gNB-CU, mappings of base reference configurations and type and/or characteristics of LTM candidate cells, the mappings comprising a mapping between the first base reference configuration and the first cell and a mapping between the second base reference configuration and the second cell; and

sending, by the gNB-CU to the UE via the serving gNB-DU, a radio resource control (RRC) reconfiguration message, the RRC reconfiguration message indicating the mappings.

19 . The non-transitory computer-readable recording medium according to claim 18 ,

wherein the method further comprises:

receiving, by the serving gNB-DU, an Intra-or Inter-Frequency Layer 1 (L1) measurement report from the UE;

based on the Intra-or Inter-Frequency L1 measurement report, determining, by the serving gNB-DU, to perform a serving cell change; and

sending, by the serving gNB-DU, a Medium Access Control (MAC) Control Element (CE) comprising a serving cell change command to the UE indicating a change to one of the LTM candidate cells,

wherein a full LTM candidate cell configuration is obtained by the UE based on a base reference configuration and a delta configuration of the one of the LTM candidate cells, the base reference configuration being determined from the mappings included in the RRC Reconfiguration message.

20 . The non-transitory computer-readable recording medium according to claim 19 ,

wherein the method further comprises:

determining, by the gNB-CU, associations between each base reference configuration and a type of corresponding target cell(s) and/or target gNB-DU(s); and

determining, by the gNB-CU and based on the associations, an appropriate base reference configuration to send to a candidate/target gNB-DU according to a type and/or characteristics of the candidate/target gNB-DU, to prepare an inter gNB-DU LTM candidate cell hosted by the candidate/target gNB-DU.