Apparatuses and methods for enhancement of cell reconnection for client nodes in non-terrestrial networks
Example embodiments provide signaling between a network node and a client node in non-terrestrial network which enables optimizing energy consumption of the client node. The client node may adapt its power saving mode duration to end at a suitable time for transmission based on information about transmission opportunities computed by the network node. The network nodes may be moving network nodes that operate at altitude, such as satellites. Apparatuses, methods, and computer programs are disclosed.
1 . A client node, comprising:
at least one processor; and
at least one memory including computer program code;
the at least one memory and the computer program code being configured to, with the at least one processor, cause the client node at least to:
based on a regular transmission pattern of the client node, determine at least one scheduled transmission time comprising a next transmission time of the client node, a next transmission time window of the client node, or a transmission time interval of the client node for sending data;
send, prior to the client node entering a power saving mode, an inquiry to a network node for transmission opportunities, wherein the network node is a base station in a non-terrestrial network (NTN) hosted on a moving platform, and wherein the inquiry comprises an indication of the at least one scheduled transmission time of the client node;
receive, from the network node, information calculated by the network node based on a static location of the client node and ephemeris data of moving network nodes, the information comprising an indication of at least one transmission opportunity based on the at least one scheduled transmission time of the client node and assisting parameters associated with the at least one transmission opportunity for reconnection after the power saving mode without performing cell reselection, wherein the ephemeris data comprises predicted orbital positions and velocities of the moving network nodes, wherein the assisting parameters comprise:
a physical cell identity of a new cell to connect to after the power saving mode,
a time of availability of the network node, wherein the time of availability of the network node comprises an indication of a time for the transmission by the client node or a time slot for the transmission by the client node,
random access control channel opportunities, and
a random access control channel preamble;
store the assisting parameters for use upon exiting the power saving mode; and
based on the at least one transmission opportunity and the assisting parameters, adjust a duration of the power saving mode of the client node by extending the duration to align a wake-up time of the client node with a transmission opportunity that is later than the at least one scheduled transmission time, wherein the transmission opportunity is with a new satellite different from a satellite with which the client node was previously connected.
2 . The client node of claim 1 , wherein the indication of the at least one transmission opportunity is further based on a predicted period of network availability for the static location of the client node in a sparse satellite deployment, and wherein the assisting parameters further comprise at least one of a timing compensation offset or a doppler compensation offset for connecting to the new cell of the new satellite.
3 . The client node of claim 1 , wherein the information received from the network node in response to the inquiry further comprises a schedule of a plurality of transmission opportunities of the client node, each of the plurality of transmission opportunities corresponding to one of a plurality of future scheduled transmission times of the client node, and
wherein the client node is further configured to: enter the power saving mode between each of the plurality of scheduled transmission times without sending a subsequent inquiry; and place a random-access memory (RAM) of the client node into a minimum power state sufficient to retain the data during the power saving mode.
4 . A base station in a non-terrestrial network (NTN) hosted on a a low-earth-orbit satellite hosting a gNB, the base station comprising:
at least one processor; and
at least one memory including computer program code;
the at least one memory and the computer program code being configured to, with the at least one processor, cause the base station at least to:
receive, from a client node prior to the client node entering a power saving mode, an inquiry for transmission opportunities, the inquiry indicating at least one scheduled transmission time of the client node, wherein the at least one scheduled transmission time comprises a next transmission time of the client node, a next transmission time window of the client node, or a transmission time interval of the client node for sending data, and wherein the at least one scheduled transmission time is determined based on a regular transmission pattern of the client node;
predict orbital movement of the low-earth-orbit satellite relative to a surface location on Earth of the client node;
based on a static location of the client node and ephemeris data of moving network nodes, compute at least one transmission opportunity and assisting parameters associated with the at least one transmission opportunity for reconnection of the client node after the power saving mode; and
send, to the client node, information comprising an indication of the at least one transmission opportunity and the assisting parameters, wherein the at least one transmission opportunity is reserved for the client node to an exclusion of other client nodes, wherein the at least one transmission opportunity is for a time later than the at least one scheduled transmission time and is with a new satellite different from a satellite with which the client node was previously connected upon entering the power saving mode, wherein the information enables the client node to reconnect without performing cell reselection, and wherein the assisting parameters comprise:
a physical cell identity of a new cell to connect to after the power saving mode,
a time of availability of a network node, wherein the time of availability of the network node comprises an indication of a time for the transmission by the client node or a time slot for the transmission by the client node,
random access control channel opportunities, and
a random access control channel preamble.
5 . The base station of claim 4 , wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the base station to:
reserve the at least one transmission opportunity to the client node.