User device and network node for wireless communication network, and operation methods therefor

1 . A user device comprising:

at least one processor; and

at least one memory comprising a computer program code;

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the user device at least to:

(a) receive a Wake-Up Signal (WUS) Beacon Occasion (WBO) configuration for a current Tracking Area (TA), the current TA comprising a set of intra-frequency cells each having an ID, and the WBO configuration comprising:

a periodicity of a WBO;

a set of time-multiplexed WUS beacons within the WBO, each WUS beacon of the set of WUS beacons having a cell-specific time offset within the WBO; and

a mapping table that maps each of the cell-specific time offsets to cell-specific information comprising at least the ID of one cell of the set of intra-frequency cells of the current TA;

(b) while the user device is in a sleep state in the current TA in which a wake-up signal receiver remains active and a primary transceiver is deactivated, the sleep state comprising RRC_IDLE or RRC_INACTIVE, monitor a reception (RX) level and/or RX quality of each WUS beacon of the set of WUS beacons in the current TA; and

(c) based on the monitoring in (b): (i) determine that the user device is within the current TA when at least one WUS beacon identified by the mapping table as belonging to the current TA satisfies an RX level and/or RX quality threshold and, upon said determination, maintain the sleep state, select a WUS beacon for tracking, and switch to a different WUS beacon identified by the mapping table as belonging to the current TA when its RX level and/or RX quality exceeds that of a currently tracked WUS beacon; and

(ii) determine that the user device is outside the current TA when no WUS beacon identified by the mapping table as belonging to the current TA satisfies the RX level and/or RX quality threshold, and, in response, initiate operations to acquire a WBO configuration for a new TA.

2 . The user device of claim 1 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the user device to:

determine that the RX level monitored for each WUS beacon of the set of WUS beacons in the current TA is less than a threshold, and/or the RX quality monitored for each WUS beacon of the set of WUS beacons in the current TA is less than a threshold;

based on said determination, detect that the user device is outside the current TA; and

perform operations (a)-(c) for a new TA comprising a set of intra-frequency cells each having an ID.

3 . The user device of claim 2 , wherein the WBO for the new TA is time shifted and/or frequency shifted from the WBO for the current TA.

4 . The user device of claim 1 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the user device to: receive, in operation (a), a cell-optimized WBO configuration comprising:

at least one WUS beacon of the set of WUS beacons in the WBO configuration for the current TA; and

at least one WUS beacon of a set of WUS beacons in a WBO configuration for at least one other TA, the at least one WUS beacon of the set of WUS beacons in the WBO configuration for each of the at least one other TA being time shifted from the at least one WUS beacon of the set of WUS beacons in the WBO configuration for the current TA;

monitor, before operations (b) and (c), a RX level and/or RX quality of each WUS beacon in the cell-optimized WBO configuration when the user device is in the sleep state; and

based on the monitored RX level and/or RX quality of each WUS beacon in the cell-optimized WBO configuration, decide whether to switch between different WUS beacons in the cell-optimized WBO configuration or to perform operations (b) and (c).

5 . The user device of claim 1 , wherein the mapping table further maps each of the cell-specific time offsets to an indicator of a cell-specific frequency and/or cell-specific frequency range to be used by the user device to search for a synchronization signal.

6 . The user device of claim 5 , wherein the indicator of the cell-specific frequency and/or cell-specific frequency range is configured as a Global Synchronization Channel Number (GSCN).

7 . The user device of claim 1 , wherein the WBO configuration further comprises, for the set of WUS beacons:

an allocated subcarrier;

a symbol offset, a slot offset and a frame offset;

a symbol duration, a slot duration and a frame duration; and

a frame periodicity.

8 . A network node comprising:

at least one processor; and

at least one memory comprising a computer program code;

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the network node at least to:

(a) define a Wake-Up Signal (WUS) Beacon Occasion (WBO) configuration for a current Tracking Area (TA) of a user device, the current TA comprising a set of intra-frequency cells each having an ID, and the WBO configuration comprising:

a periodicity of a WBO;

a set of WUS beacons within the WBO, each WUS beacon of the set of WUS beacons having a cell-specific time offset within the WBO; and

a mapping table that maps each of the cell-specific time offsets to the ID of one cell of the set of intra-frequency cells of the current TA; and

(b) transmit the WBO configuration to the user device,

wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the network node to:

define, in operation (a), a cell-optimized WBO configuration comprising:

at least one WUS beacon of the set of WUS beacons in the WBO configuration for the current TA; and

at least one WUS beacon of the set of WUS beacons in a WBO configuration for at least one other TA, the at least one WUS beacon of the set of WUS beacons in the WBO configuration for each of the at least one other TA being time shifted from the at least one WUS beacon of the set of WUS beacons in the WBO configuration for the current TA; and transmit, in operation (b), the cell-optimized WBO configuration to the user device,

wherein the mapping table further maps each of the cell-specific time offsets to an indicator of a cell-specific frequency and/or cell-specific frequency range to be used by the user device to search for a synchronization signal,

wherein the indicator of the cell-specific frequency and/or cell-specific frequency range is configured as a Global Synchronization Channel Number (GSCN),

wherein the WBO configuration further comprises, for the set of WUS beacons:

an allocated subcarrier;

a symbol offset, a slot offset and a frame offset;

a symbol duration, a slot duration and a frame duration; and

a frame periodicity

wherein the set of WUS beacons within the WBO are transmitted on a same frequency and in mutually non-overlapping time positions within the WBO

wherein the mapping table specifies, for each intra-occasion beacon index, a corresponding cell ID,

wherein the network node transmits the WBO configuration as system information (SIB) and/or via dedicated RRC signaling, and

wherein WBOs associated with different TAs of a same Registration Area are defined such that their time windows are non-overlapping and/or frequency-shifted with respect to one another.

9 . A method for operating a user device, comprising:

(a) receiving a Wake-Up Signal (WUS) Beacon Occasion (WBO) configuration for a current Tracking Area (TA), the current TA comprising a set of intra-frequency cells each having an ID, and the WBO configuration comprising:

a periodicity of a WBO;

a set of time-multiplexed WUS beacons within the WBO, each WUS beacon of the set of WUS beacons having a cell-specific time offset within the WBO; and

a mapping table that maps each of the cell-specific time offsets to cell-specific information comprising at least the ID of one cell of the set of intra-frequency cells of the current TA;

(b) while the user device is in a sleep state in the current TA in which a wake-up signal receiver remains active and a primary transceiver is deactivated, the sleep state comprising RRC_IDLE or RRC_INACTIVE, monitoring a reception (RX) level and/or RX quality of each WUS beacon of the set of WUS beacons in the current TA; and

(c)) based on the monitoring in (b): (i) determining that the user device is within the current TA when at least one WUS beacon identified by the mapping table as belonging to the current TA satisfies an RX level and/or RX quality threshold, and, upon said determination, maintaining the sleep state, selecting a WUS beacon for tracking, and switching to a different WUS beacon identified by the mapping table as belonging to the current TA when its RX level and/or RX quality exceeds that of a currently tracked WUS beacon; and (ii) determining that the user device is outside the current TA when no WUS beacon identified by the mapping table as belonging to the current TA satisfies the RX level and/or RX quality threshold, and, in response, initiating operations to acquire a WBO configuration for a new TA.

10 . The method of claim 9 , wherein monitoring in (b) comprises monitoring within a time window during the WBO without changing a receiver frequency, and wherein the set of WUS beacons within the WBO are transmitted on a same frequency in mutually non-overlapping time positions to avoid intra-TA interference while the user device monitors in the sleep state.

11 . The method of claim 9 , wherein switching to a different WUS beacon comprises maintaining the primary transceiver deactivated and selecting the different WUS beacon whose RX level and/or RX quality is better than that of a currently used WUS beacon without changing a receiver frequency during the WBO.

12 . The method of claim 9 , wherein determining that the user device is outside the current TA comprises determining that the user device is no longer able to receive any WUS beacon with a sufficient RX level and/or RX quality within the configured WBO and, in response, turning on a primary transceiver, obtaining a WBO configuration for a new TA via broadcast system information or dedicated signaling, and thereafter returning the user device to a sleep state.

13 . The method of claim 9 , wherein the user device uses the mapping table that maps each WUS beacon's cell-specific time offset to a cell ID to identify whether a WUS beacon belongs to the current TA when performing the determinations in (c), and, when the user device is unable to detect a WUS beacon of the current TA, attempts to find a WUS beacon belonging to a WBO configuration associated with a neighboring TA of a same Registration Area using mapping tables for different TAs.

14 . The method of claim 9 , wherein the user device deactivates a wake-up signal receiver between WBO periods and, when timing alignment is maintained, sleeps for multiple WBO periods before re-activating to monitor a subsequent WBO.

15 . The method of claim 9 , wherein the user device determines a time position of each WUS beacon from a symbol offset, a slot offset, and a frame offset in the WBO configuration and schedules monitoring accordingly.

16 . The method of claim 9 , wherein the user device retrieves, from the mapping table, an indicator of a cell-specific frequency and/or cell-specific frequency range configured as a Global Synchronization Channel Number (GSCN) and searches for a synchronization signal based on the indicator.