Bi-layered mobility for NG-RAN
Improved techniques of intra and inter distributed unit mobility include determining, by a user equipment served by a source cell, whether a target cell belongs to the same distributed unit as the source cell based on information sent by the central unit (control plane) after a connection with the network node has been established. The information sent by the network node includes, for each cell, a group identifier identifying the distributed unit with which that cell is associated. When measurement data provided by the user equipment indicates readiness for a serving cell change to a target cell, the user equipment uses the group identifier to determine whether the target cell belongs to the same distributed unit as the source cell (intra-distributed unit mobility scenario) or a different distributed unit as the source cell (inter-distributed unit mobility scenario).
1 . An apparatus, comprising:
at least one processor; and
at least one memory including computer program code;
the at least one memory and the computer program code configured to cause the apparatus at least to:
receive, by a first distributed unit of a network node, measurement data from a user equipment served by a source cell associated with the first distributed unit, the network node also including a second distributed unit and a central unit;
in response to (i) determining conditions for a serving cell change of the user equipment from the source cell to a target cell have been satisfied based on the measurement data and (ii) the target cell is also associated with the first distributed unit,
perform, by the first distributed unit, the serving cell change of the user equipment from the source cell to the target cell; and
in response to (i) determining conditions for a serving cell change from the source cell to the target cell have been satisfied based on the measurement data and (ii) the target cell is associated with the second distributed unit, transmit the measurement data to the central unit so that the central unit may perform the serving cell change.
2 . The apparatus as in claim 1 , wherein the at least one memory and the computer program code are further configured to cause the apparatus at least to:
receive, from the central unit, mapping data representing a mapping between a plurality of physical cell identifiers and a plurality of physical cell group identifiers, each of the plurality of physical cell identifiers identifying a respective cell of a plurality of cells associated with at least first and second distributed units, each of the physical cell group identifiers identifying a respective group of one or more cells from at least the first distributed unit or the second distributed unit, and
determine whether the target cell is served by the first distributed unit based on the mappings between (i) the physical cell identifiers identifying the source cell and the target cell and (ii) the physical cell group identifiers identifying the first distributed unit and the second distributed unit.
3 . The apparatus as in claim 2 , wherein the at least one memory and the computer program code are further configured to cause the apparatus at least to:
transmit, to the central unit, cell data representing a plurality of physical cell identifiers; and
receive, from the central unit, the mapping data, the mapping data being based on the cell data.
4 . The apparatus as in claim 2 , wherein the mapping data is received during one of an F1 setup or a central unit configuration update procedure.
5 . The apparatus as in claim 1 , wherein the measurement data includes layer 1 measurement data from layer 1 measurements of a reference signal received power and layer 3 measurement data from layer 3 measurements of the reference signal received power.
6 . The apparatus as in claim 5 , wherein the layer 1 measurement data is received via a media access control interface.
7 . The apparatus as in claim 5 , wherein, in response to the target cell being served by the second distributed unit, transmit the layer 3 measurement data to the central unit.
8 . The apparatus as in claim 7 , wherein the layer 3 measurement data is transmitted to the central unit via a radio resource control protocol.
9 . The apparatus as in claim 5 , wherein, in response to the target cell being served by the first distributed unit, not transmit any portion of the measurement data to the central unit.
10 . An apparatus, comprising:
at least one processor; and
at least one memory including computer program code;
the at least one memory and the computer program code configured to cause the apparatus at least to:
transmit, to a first distributed unit of a network node from a user equipment, measurement data taken from a source cell serving the user equipment and a target cell, the source cell being associated with the first distributed unit, the network node also including a second distributed unit and a central unit;
in response to the measurement data indicating a serving cell change to the target cell and the target cell is associated with the first distributed unit, receive a serving cell change command from the first distributed unit; and
in response to the measurement data indicating a serving cell change to the target cell and the target cell is associated with the second distributed unit, receive a serving cell change command from the central unit.
11 . The apparatus as in claim 10 , wherein the at least one memory and the computer program code are further configured to cause the apparatus at least to:
receive, from the central unit, mapping data representing a mapping between a plurality of physical cell identifiers and a plurality of physical cell group identifiers, each of the plurality of physical cell identifiers identifying a respective cell of a plurality of cells associated with at least first and second distributed units, each of the physical cell group identifiers identifying a respective group of one or more cells from at least the first distributed unit or the second distributed unit.
12 . The apparatus as in claim 11 , wherein the mapping data is received during a radio resource control reconfiguration.
13 . The apparatus as in claim 10 , wherein the measurement data includes layer 1 measurement data from layer 1 measurements of a reference signal received power and layer 3 measurement data from layer 3 measurements of the reference signal received power.
14 . The apparatus as in claim 13 , wherein the at least one memory and the computer program code configured to transmit the measurement data is further configured to cause the apparatus at least to:
in response to the measurement data indicating a serving cell change to the target cell and the target cell is associated with the first distributed unit, transmit the layer 1 measurement data to the first distributed unit via a media access control interface.
15 . The apparatus as in claim 13 , wherein the at least one memory and the computer program code configured to transmit the measurement data is further configured to cause the apparatus at least to:
in response to the measurement data indicating a serving cell change to the target cell and the target cell is associated with the second distributed unit transmit the layer 3 measurement data to the central unit via a radio resource control reconfiguration procedure.