WO2025201711A1

WO2025201711A1 - Reacquiring system information

Info

Publication number: WO2025201711A1
Application number: PCT/EP2025/053016
Authority: WO
Inventors: Navin Hathiramani; Karri Markus Ranta-Aho
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2024-03-28
Filing date: 2025-02-06
Publication date: 2025-10-02
Anticipated expiration: 2026-09-28

Abstract

Disclosed is a method comprising determining that a cell is applying or will be transitioning to an energy-saving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and based on the determination, reacquiring system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

Description

REACQUIRING SYSTEM INFORMATION

TECHNICAL FIELD

The following example embodiments relate to wireless communication.

BACKGROUND

As energy resources are limited, it is desirable to improve the energy efficiency of wireless communication networks.

SUMMARY

The scope of protection sought for various example embodiments is set out by the claims. The example embodiments and features, if any, described in this specification that do not fall under the scope of the claims are to be interpreted as examples useful for understanding various embodiments.

According to a first aspect, there is provided a user equipment comprising: means for determining a first measurement configuration indicating a first set of signals for measuring a first cell controlled by an access node, wherein the first set of signals comprises at least a synchronization signal block of the first cell; means for determining a second measurement configuration indicating a second set of signals for measuring the first cell controlled by the access node, wherein the second set of signals comprises at least one signal of a second cell different from the first cell; means for determining whether to apply the first measurement configuration or the second measurement configuration for measuring the first cell, wherein the determination is based at least on an availability of the synchronization signal block of the first cell; and means for performing, based on the determination of whether to apply the first measurement configuration or the second measurement configuration, one or more measurements of the first cell, wherein the one or more measurements are performed in an idle mode or in an inactive mode.

According to a second aspect, there is provided the user equipment of the first aspect, wherein the first cell and the second cell are co-located. According to a third aspect, there is provided the user equipment of any of the first or second aspects, wherein the first cell is associated with a first radio access technology, and the second cell is associated with a second radio access technology different from the first radio access technology, and wherein the at least one signal of the second cell comprises at least one of: a synchronization signal block of the second cell, a channel state information reference signal of the second cell, or a tracking reference signal of the second cell.

According to a fourth aspect, there is provided the user equipment of any of the first to third aspects, wherein the second measurement configuration further comprises an identifier of the second cell, and quasi-colocation information between one or more signals of the first cell and the at least one signal of the second cell.

According to a fifth aspect, there is provided the user equipment of any of the first to fourth aspects, further comprising means for selecting the second cell from a list of candidate cells comprised in the second measurement configuration, wherein the selection is based on at least one of: a priority order of the candidate cells, or measurements of the candidate cells.

According to a sixth aspect, there is provided the user equipment of any of the first to fifth aspects, wherein the second measurement configuration further comprises a power offset to be applied for the second cell relative to the first cell, wherein the means for performing the one or more measurements of the first cell are configured to apply the power offset to one or more measurements obtained from the at least one signal of the second cell, based on determining to apply the second measurement configuration.

According to a seventh aspect, there is provided the user equipment of any of the first to sixth aspects, further comprising means for determining a correction factor to be applied to the one or more measurements of the first cell when applying the second measurement configuration, wherein the determination of the correction factor is based on measurements of the first cell and the second cell; and means for applying the correction factor to the one or more measurements of the first cell performed according to the second measurement configuration, based on determining to apply the second measurement configuration.

According to an eighth aspect, there is provided the user equipment of any of the first to seventh aspects, further comprising means for receiving, from the access node, an indication indicating to use the second set of signals for measuring the first cell; and means for reacquiring, based on receiving the indication, system information of the first cell, regardless of whether a validity timer of previously acquired system information of the first cell has expired.

According to a ninth aspect, there is provided the user equipment of any of the first to seventh aspects, further comprising means for determining whether the synchronization signal block of the first cell has not been detected for a period of time larger than an expected periodicity of the synchronization signal block of the first cell, wherein the means for determining whether to apply the first measurement configuration or the second measurement configuration are configured to make the determination based at least on the determination of whether the synchronization signal block of the first cell has not been detected for the period of time larger than the expected periodicity of the synchronization signal block of the first cell.

According to a tenth aspect, there is provided the user equipment of the ninth aspect, further comprising means for determining whether one or more other signals of the first cell are detected, the one or more other signals being comprised in the second set of signals and being different from the synchronization signal block of the first cell, wherein the means for determining whether to apply the first measurement configuration or the second measurement configuration are configured to make the determination based further on the determination of whether the one or more other signals of the first cell are detected.

According to an eleventh aspect, there is provided the user equipment of any of the ninth to tenth aspects, further comprising means for determining whether the at least one signal of the second cell is detected, wherein the means for determining whether to apply the first measurement configuration or the second measurement configuration are configured to make the determination based further on the determination of whether the at least one signal of the second cell is detected.

According to a twelfth aspect, there is provided the user equipment of any of the first to eleventh aspects, further comprising means for evaluating, based on determining to apply the second measurement configuration, one or more cell reselection criteria based on the second set of signals, wherein the one or more cell reselection criteria are associated with the first cell; and means for performing a cell reselection from the first cell based on the evaluation.

According to a thirteenth aspect, there is provided the user equipment of any of the first to eleventh aspects, further comprising means for detecting, based on determining to apply the second measurement configuration, that the second set of signals are not measurable or that system information for the first cell is no longer valid; and means for performing a cell reselection from the first cell based on detecting that the second set of signals are not measurable or that the system information for the first cell is no longer valid.

According to a fourteenth aspect, there is provided an access node comprising: means for generating a second measurement configuration indicating a second set of signals for measuring a first cell controlled by the access node, wherein the second set of signals comprises at least one signal of a second cell different from the first cell; and means for transmitting the second measurement configuration to a user equipment pre-configured with a first measurement configuration indicating a first set of signals for measuring the first cell controlled by the access node, wherein the first set of signals comprises at least a synchronization signal block of the first cell.

According to a fifteenth aspect, there is provided the access node of the fourteenth aspect, further comprising means for determining, based on a predetermined condition being met, to stop transmitting the synchronization signal block of the first cell; and means for transmitting, to the user equipment, based on determining to stop the transmission of the synchronization signal block of the first cell, an indication indicating to use the second set of signals for measuring the first cell; and means for stopping the transmission of the synchronization signal block of the first cell after transmitting the indication.

According to a sixteenth aspect, there is provided a method performed by a user equipment, the method comprising: determining a first measurement configuration indicating a first set of signals for measuring a first cell controlled by an access node, wherein the first set of signals comprises at least a synchronization signal block of the first cell; determining a second measurement configuration indicating a second set of signals for measuring the first cell controlled by the access node, wherein the second set of signals comprises at least one signal of a second cell different from the first cell; determining whether to apply the first measurement configuration or the second measurement configuration for measuring the first cell, wherein the determination is based at least on an availability of the synchronization signal block of the first cell; and performing, based on the determination of whether to apply the first measurement configuration or the second measurement configuration, one or more measurements of the first cell, wherein the one or more measurements are performed in an idle mode or in an inactive mode.

According to a seventeenth aspect, there is provided a method performed by an access node, the method comprising: generating a second measurement configuration indicating a second set of signals for measuring a first cell controlled by the access node, wherein the second set of signals comprises at least one signal of a second cell different from the first cell; and transmitting the second measurement configuration to a user equipment pre-configured with a first measurement configuration indicating a first set of signals for measuring the first cell controlled by the access node, wherein the first set of signals comprises at least a synchronization signal block of the first cell.

According to an eighteenth aspect, there is provided a non-transitory computer readable medium comprising program instructions which, when executed by a user equipment cause the user equipment to perform at least the following: determining a first measurement configuration indicating a first set of signals for measuring a first cell controlled by an access node, wherein the first set of signals comprises at least a synchronization signal block of the first cell; determining a second measurement configuration indicating a second set of signals for measuring the first cell controlled by the access node, wherein the second set of signals comprises at least one signal of a second cell different from the first cell; determining whether to apply the first measurement configuration or the second measurement configuration for measuring the first cell, wherein the determination is based at least on an availability of the synchronization signal block of the first cell; and performing, based on the determination of whether to apply the first measurement configuration or the second measurement configuration, one or more measurements of the first cell, wherein the one or more measurements are performed in an idle mode or in an inactive mode.

According to a nineteenth aspect, there is provided a non-transitory computer readable medium comprising program instructions which, when executed by an access node, cause the access node to perform at least the following: generating a second measurement configuration indicating a second set of signals for measuring a first cell controlled by the access node, wherein the second set of signals comprises at least one signal of a second cell different from the first cell; and transmitting the second measurement configuration to a user equipment preconfigured with a first measurement configuration indicating a first set of signals for measuring the first cell controlled by the access node, wherein the first set of signals comprises at least a synchronization signal block of the first cell.

According to a twentieth aspect, there is provided a computer program comprising instructions which, when executed by a user equipment, cause the user equipment to perform at least the following: determining a first measurement configuration indicating a first set of signals for measuring a first cell controlled by an access node, wherein the first set of signals comprises at least a synchronization signal block of the first cell; determining a second measurement configuration indicating a second set of signals for measuring the first cell controlled by the access node, wherein the second set of signals comprises at least one signal of a second cell different from the first cell; determining whether to apply the first measurement configuration or the second measurement configuration for measuring the first cell, wherein the determination is based at least on an availability of the synchronization signal block of the first cell; and performing, based on the determination of whether to apply the first measurement configuration or the second measurement configuration, one or more measurements of the first cell, wherein the one or more measurements are performed in an idle mode or in an inactive mode.

According to a twenty-first aspect, there is provided a computer program comprising instructions which, when executed by an access node, cause the access node to perform at least the following: generating a second measurement configuration indicating a second set of signals for measuring a first cell controlled by the access node, wherein the second set of signals comprises at least one signal of a second cell different from the first cell; and transmitting the second measurement configuration to a user equipment pre-configured with a first measurement configuration indicating a first set of signals for measuring the first cell controlled by the access node, wherein the first set of signals comprises at least a synchronization signal block of the first cell.

According to a twenty-second aspect, there is provided a computer readable medium comprising program instructions which, when executed by a user equipment, cause the user equipment to perform at least the following: determining a first measurement configuration indicating a first set of signals for measuring a first cell controlled by an access node, wherein the first set of signals comprises at least a synchronization signal block of the first cell; determining a second measurement configuration indicating a second set of signals for measuring the first cell controlled by the access node, wherein the second set of signals comprises at least one signal of a second cell different from the first cell; determining whether to apply the first measurement configuration or the second measurement configuration for measuring the first cell, wherein the determination is based at least on an availability of the synchronization signal block of the first cell; and performing, based on the determination of whether to apply the first measurement configuration or the second measurement configuration, one or more measurements of the first cell, wherein the one or more measurements are performed in an idle mode or in an inactive mode.

According to a twenty-third aspect, there is provided a computer readable medium comprising program instructions which, when executed by an access node, cause the access node to perform at least the following: generating a second measurement configuration indicating a second set of signals for measuring a first cell controlled by the access node, wherein the second set of signals comprises at least one signal of a second cell different from the first cell; and transmitting the second measurement configuration to a user equipment preconfigured with a first measurement configuration indicating a first set of signals for measuring the first cell controlled by the access node, wherein the first set of signals comprises at least a synchronization signal block of the first cell.

According to a twenty-fourth aspect, there is provided a user equipment comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to: determine a first measurement configuration indicating a first set of signals for measuring a first cell controlled by an access node, wherein the first set of signals comprises at least a synchronization signal block of the first cell; determine a second measurement configuration indicating a second set of signals for measuring the first cell controlled by the access node, wherein the second set of signals comprises at least one signal of a second cell different from the first cell; determine whether to apply the first measurement configuration or the second measurement configuration for measuring the first cell, wherein the determination is based at least on an availability of the synchronization signal block of the first cell; and perform, based on the determination of whether to apply the first measurement configuration or the second measurement configuration, one or more measurements of the first cell, wherein the one or more measurements are performed in an idle mode or in an inactive mode.

According to a twenty-fifth aspect, there is provided an access node comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the access node at least to: generating a second measurement configuration indicating a second set of signals for measuring a first cell controlled by the access node, wherein the second set of signals comprises at least one signal of a second cell different from the first cell; and transmitting the second measurement configuration to a user equipment preconfigured with a first measurement configuration indicating a first set of signals for measuring the first cell controlled by the access node, wherein the first set of signals comprises at least a synchronization signal block of the first cell.

According to a twenty-sixth aspect, there is provided a user equipment comprising: means for determining that a cell is applying or will be transitioning to an energy-saving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and means for reacquiring, based on the determination, system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

According to a twenty-seventh aspect, there is provided the user equipment of the twenty-sixth aspect, wherein the means for reacquiring the system information of the cell are configured to reacquire the system information before the expiration of the validity timer.

According to a twenty-eighth aspect, there is provided the user equipment of any of the twenty-sixth to twenty-seventh aspects, further comprising means for resetting the validity timer based on reacquiring the system information.

According to a twenty-ninth aspect, there is provided the user equipment of any of the twenty-sixth to twenty-eighth aspects, further comprising means for receiving, from an access node controlling the cell, an indication indicating that the cell will be transitioning to the energy-saving mode, wherein the means for determining that the cell is applying or will be transitioning to the energy-saving mode are configured to make the determination based on the indication.

According to a thirtieth aspect, there is provided the user equipment of the twenty-ninth aspect, wherein the indication indicates a time when the cell will be transitioning to the energy-saving mode, wherein the means for reacquiring the system information are configured to initiate the reacquisition of the system information before the time when the cell will be transitioning to the energy-saving mode.

According to a thirty-first aspect, there is provided the user equipment of any of the twenty-ninth to thirtieth aspects, wherein the indication indicates a time threshold within which the system information is to be reacquired, the time threshold being relative to the expiration of the validity timer, wherein the means for reacquiring the system information are configured to reacquire the system information based on determining that a remaining time to the expiration of the validity timer is less than the time threshold, the remaining time being higher than zero.

According to a thirty-second aspect, there is provided the user equipment of any of the twenty-sixth to twenty-eighth aspects, further comprising means for detecting an on-demand system information block transmission of the cell, wherein the on-demand system information block transmission indicates that the cell is applying the energy-saving mode, wherein the means for determining that the cell is applying or will be transitioning to the energy-saving mode are configured to make the determination based on the detection.

According to a thirty-third aspect, there is provided the user equipment of any of the twenty-sixth to twenty-eighth aspects, wherein the means for determining that the cell is applying or will be transitioning to the energy-saving mode are configured to make the determination based on historical data of the cell, the historical data indicating a pattern of the cell potentially transitioning to the energy-saving mode. According to a thirty-fourth aspect, there is provided the user equipment of any of the twenty-sixth to thirty-third aspects, wherein the cell comprises a serving cell of the user equipment, or a neighbor cell of the serving cell.

According to a thirty-fifth aspect, there is provided an access node comprising: means for determining, based on a predetermined condition being met, to transition a cell controlled by the access node to an energy-saving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and means for transmitting, to one or more user equipments, based on determining to transition the cell to the energy-saving mode, an indication indicating that the cell is applying or will be transitioning to the energy-saving mode, wherein the indication indicates the one or more user equipments to reacquire system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

According to a thirty-sixth aspect, there is provided the access node of the thirty-fifth aspect, wherein the indication indicates a time when the cell will be transitioning to the energy-saving mode.

According to a thirty-seventh aspect, there is provided the access node of any of the thirty-fifth to thirty-sixth aspects, wherein the indication indicates a time threshold within which the system information is to be reacquired, the time threshold being relative to the expiration of the validity timer.

According to a thirty-eighth aspect, there is provided the access node of any of the thirty-fifth to thirty-seventh aspects, wherein the predetermined condition is related to a load of the cell.

According to a thirty-ninth aspect, there is provided a method performed by a user equipment, the method comprising: determining that a cell is applying or will be transitioning to an energy-saving mode, wherein the energysaving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and based on the determination, reacquiring system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

According to a fortieth aspect, there is provided a method performed by an access node, the method comprising: determining, based on a predetermined condition being met, to transition a cell controlled by the access node to an energysaving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and, based on determining to transition the cell to the energy-saving mode, transmit, to one or more user equipments, an indication indicating that the cell is applying or will be transitioning to the energy-saving mode, wherein the indication indicates the one or more user equipments to reacquire system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

According to a forty-first aspect, there is provided a non-transitory computer readable medium comprising program instructions which, when executed by a user equipment, cause the user equipment to perform at least the following: determining that a cell is applying or will be transitioning to an energysaving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and based on the determination, reacquiring system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired. According to a forty-second aspect, there is provided a non-transitory computer readable medium comprising program instructions which, when executed by an access node, cause the access node to perform at least the following: determining, based on a predetermined condition being met, to transition a cell controlled by the access node to an energy-saving mode, wherein the energysaving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and, based on determining to transition the cell to the energy-saving mode, transmit, to one or more user equipments, an indication indicating that the cell is applying or will be transitioning to the energy-saving mode, wherein the indication indicates the one or more user equipments to reacquire system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

According to a forty-third aspect, there is provided a computer program comprising instructions which, when executed by a user equipment, cause the user equipment to perform at least the following: determining that a cell is applying or will be transitioning to an energy-saving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and based on the determination, reacquiring system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

According to a forty-fourth aspect, there is provided a computer program comprising instructions which, when executed by an access node, cause the access node to perform at least the following: determining, based on a predetermined condition being met, to transition a cell controlled by the access node to an energy-saving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and, based on determining to transition the cell to the energysaving mode, transmit, to one or more user equipments, an indication indicating that the cell is applying or will be transitioning to the energy-saving mode, wherein the indication indicates the one or more user equipments to reacquire system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

According to a forty-fifth aspect, there is provided a computer readable medium comprising program instructions which, when executed by a user equipment, cause the user equipment to perform at least the following: determining that a cell is applying or will be transitioning to an energy-saving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and based on the determination, reacquiring system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

According to a forty-sixth aspect, there is provided a computer readable medium comprising program instructions which, when executed by an access node, cause the access node to perform at least the following: determining, based on a predetermined condition being met, to transition a cell controlled by the access node to an energy-saving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and, based on determining to transition the cell to the energysaving mode, transmit, to one or more user equipments, an indication indicating that the cell is applying or will be transitioning to the energy-saving mode, wherein the indication indicates the one or more user equipments to reacquire system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

According to a forty-seventh aspect, there is provided a user equipment comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to: determine that a cell is applying or will be transitioning to an energy-saving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and based on the determination, reacquire system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

According to a forty-eighth aspect, there is provided an access node comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the access node at least to: determine, based on a predetermined condition being met, to transition a cell controlled by the access node to an energy-saving mode, wherein the energysaving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and, based on determining to transition the cell to the energy-saving mode, transmit, to one or more user equipments, an indication indicating that the cell is applying or will be transitioning to the energy-saving mode, wherein the indication indicates the one or more user equipments to reacquire system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired. BRIEF DESCRIPTION OF THE DRAWINGS

In the following, various example embodiments will be described in greater detail with reference to the accompanying drawings, in which

FIG. 1A illustrates an example of a wireless communication network;

FIG. IB illustrates an example of a system;

FIG. 2 illustrates a signal flow diagram;

FIG. 3 illustrates an example of a configuration of a second set of signals;

FIG. 4 illustrates a flow chart;

FIG. 5 illustrates a flow chart;

FIG. 6 illustrates a flow chart;

FIG. 7 illustrates a flow chart;

FIG. 8 illustrates a flow chart;

FIG. 9 illustrates a flow chart;

FIG. 10 illustrates an example of an apparatus; and

FIG. 11 illustrates an example of an apparatus.

DETAILED DESCRIPTION

The following embodiments are exemplifying. Although the specification may refer to “an”, “one”, or “some” embodiment(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment(s), or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments within the scope of the claims. Furthermore, the words "comprising" and "including" should be understood as not limiting the described embodiments to consist of only those features that have been mentioned, and such embodiments may also contain features that have not been specifically mentioned. Reference numbers, in the description and/or in the claims, serve to illustrate the embodiments with reference to the drawings, without limiting the embodiments to these examples only.

Some example embodiments described herein may be implemented in a wireless communication network comprising a radio access network based on one or more of the following radio access technologies (RATs): global system for mobile communications (GSM) or any other second generation (2G) radio access technology, universal mobile telecommunication system (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), long term evolution (LTE), LTE-Advanced, fourth generation (4G), fifth generation (5G), 5G new radio (NR), 5G-Advanced (i.e., 3GPP NR Rel-18 and beyond), or sixth generation (6G). Some examples of radio access networks include the universal mobile telecommunications system (UMTS) radio access network (UTRAN), the evolved universal terrestrial radio access network (E-UTRA), or the next generation radio access network (NG-RAN). The wireless communication network may further comprise a core network, and some example embodiments may also be applied to network functions of the core network.

It should be noted that the embodiments are not restricted to the wireless communication network given as an example, but a person skilled in the art may also apply the solution to other wireless communication networks or systems provided with necessary properties. For example, some example embodiments may also be applied to a communication system based on IEEE 802.11 specifications, or a communication system based on IEEE 802.15 specifications. IEEE is an abbreviation for the Institute of Electrical and Electronics Engineers.

FIG. 1A depicts an example of a simplified wireless communication network showing some physical and logical entities. The connections shown in FIG. 1A may be physical connections or logical connections. It is apparent to a person skilled in the art that the wireless communication network may also comprise other physical and logical entities than those shown in FIG. 1A.

The example embodiments described herein are not, however, restricted to the wireless communication network given as an example but a person skilled in the art may apply the example embodiments described herein to other wireless communication networks provided with necessary properties.

The example wireless communication network shown in FIG. 1A includes a radio access network (RAN) and a core network 110. FIG. 1A shows user equipment (UE) 100, 102 configured to be in a wireless connection on one or more communication channels in a radio cell with an access node 104 of a radio access network.

The access node 104 may comprise a computing device configured to control the radio resources of the access node 104 and to be in a wireless connection with one or more UEs 100, 102. The access node 104 may also be referred to as a base station, a base transceiver station (BTS), an access point, a cell site, a network node, a radio access network node, or a RAN node. In this description, the terms “access node” and “radio access network node” may be used interchangeably.

The access node 104 may be, for example, an evolved NodeB (abbreviated as eNB or eNodeB), or a next generation evolved NodeB (abbreviated as ng-eNB), or a next generation NodeB (abbreviated as gNB or gNodeB), providing the radio cell. The access node 104 may include or be coupled to transceivers. From the transceivers of the access node 104, a connection may be provided to an antenna unit that establishes a bi-directional radio link to one or more UEs 100, 102. The antenna unit may comprise an antenna or antenna element, or a plurality of antennas or antenna elements.

The wireless connection (e.g., radio link) from a UE 100, 102 to the access node 104 may be called uplink (UL) or reverse link, and the wireless connection (e.g., radio link) from the access node 104 to the UE 100, 102 may be called downlink (DL) or forward link. A UE 100 may also communicate directly with another UE 102, and vice versa, via a wireless connection generally referred to as a sidelink (SL). It should be appreciated that the access node 104 or its functionalities may be implemented by using any node, host, server, access point or other entity suitable for providing such functionalities.

The radio access network may comprise more than one access node 104, in which case the access nodes may also be configured to communicate with one another over wired or wireless links. These links between access nodes may be used for sending and receiving control plane signaling and also for routing data from one access node to another access node. The access node 104 may further be connected to a core network (CN) 110. The core network 110 may comprise an evolved packet core (EPC) network and/or a 5^th generation core network (5GC). The EPC may comprise network entities, such as a serving gateway (S-GW for routing and forwarding data packets), a packet data network gateway (P-GW) for providing connectivity of UEs to external packet data networks, and/or a mobility management entity (MME). The 5GC may comprise one or more network functions, such as at least one of: a user plane function (UPF), an access and mobility management function (AMF), a location management function (LMF), and/or a session management function (SMF).

The core network 110 may also be able to communicate with one or more external networks 113, such as a public switched telephone network or the Internet, or utilize services provided by them. For example, in 5G wireless communication networks, the UPF of the core network 110 may be configured to communicate with an external data network via an N6 interface. In LTE wireless communication networks, the P-GW of the core network 110 may be configured to communicate with an external data network.

It should also be understood that the distribution of functions between core network operations and access node operations may differ in future wireless communication networks compared to that of the LTE or 5G, or even be nonexistent.

The illustrated UE 100, 102 is one type of an apparatus to which resources on the air interface may be allocated and assigned. The UE 100, 102 may also be called a wireless communication device, a subscriber unit, a mobile station, a remote terminal, an access terminal, a user terminal, a terminal device, or a user device, just to mention but a few names. The UE 100, 102 may be a computing device operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of computing devices: a mobile phone, a smartphone, a personal digital assistant (PDA), a handset, a computing device comprising a wireless modem (e.g., an alarm or measurement device, etc.), a laptop computer, a desktop computer, a tablet, a game console, a notebook, a multimedia device, a reduced capability (RedCap) device, a wearable device (e.g., a watch, earphones or eyeglasses) with radio parts, a sensor comprising a wireless modem, or a computing device comprising a wireless modem integrated in a vehicle.

It should be appreciated that the UE 100, 102 may also be a nearly exclusive uplink-only device, of which an example may be a camera or video camera loading images or video clips to a network. The UE 100, 102 may also be a device having capability to operate in an Internet of Things (loT) network, which is a scenario in which objects may be provided with the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction.

The wireless communication network may also be able to support the usage of cloud services. For example, at least part of core network operations may be carried out as a cloud service (this is depicted in FIG. 1A by “cloud” 114). The UE 100, 102 may also utilize the cloud 114. In some applications, the computation for a given UE may be carried out in the cloud 114 or in another UE.

The wireless communication network may also comprise a central control entity, such as a network management system (NMS), or the like. The NMS is a centralized suite of software and hardware used to monitor, control, and administer the network infrastructure. The NMS is responsible for a wide range of tasks such as fault management, configuration management, security management, performance management, and accounting management. The NMS enables network operators to efficiently manage and optimize network resources, ensuring that the network delivers high performance, reliability, and security.

5G enables using multiple-input and multiple-output (M1M0) antennas in the access node 104 and/or the UE 100, 102, many more base stations or access nodes than an LTE network (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and/or spectrum available. 5G wireless communication networks may support a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine-type applications, such as (massive) machine-type communications (mMTC), including vehicular safety, different sensors and real-time control.

In 5G wireless communication networks, access nodes and/or UEs may have multiple radio interfaces, such as below 6 gigahertz (GHz), centimeter wave (cmWave) and millimeter wave (mmWave), and also being integrable with legacy radio access technologies, such as LTE. Integration with LTE may be implemented, for example, as a system, where macro coverage may be provided by LTE, and 5G radio interface access may come from small cells by aggregation to LTE. In other words, a 5G wireless communication network may support both inter-RAT operability (such as interoperability between LTE and 5G) and inter-Rl operability (inter-radio interface operability, such as between below 6GHz, cmWave, and mmWave).

5G wireless communication networks may also apply network slicing, in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same physical infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

In one embodiment, an access node 104 may comprise: a radio unit (RU) 103 comprising a radio transceiver (TRX), i.e., a transmitter (Tx) and a receiver (Rx); one or more distributed units (DUs) 105 that may be used for the so-called Layer 1 (LI) processing and real-time Layer 2 (L2) processing; and a central unit (CU) 108 (also known as a centralized unit) that may be used for non-real-time L2 and Layer 3 (L3) processing. The CU 108 may be connected to the one or more DUs 105 for example via an Fl interface. Such an embodiment of the access node 104 may enable the centralization of CUs relative to the cell sites and DUs, whereas DUs may be more distributed and may even remain at cell sites. The CU and DU together may also be referred to as baseband or a baseband unit (BBU). The CU and DU may also be comprised in a radio access point (RAP).

The CU 108 may be a logical node hosting radio resource control (RRC), service data adaptation protocol (SDAP) and/or packet data convergence protocol (PDCP), of the NR protocol stack for an access node 104. The CU 108 may comprise a control plane (CU-CP), which may be a logical node hosting the RRC and the control plane part of the PDCP protocol of the NR protocol stack for the access node 104. The CU 108 may further comprise a user plane (CU-UP), which may be a logical node hosting the user plane part of the PDCP protocol and the SDAP protocol of the CU for the access node 104.

The DU 105 may be a logical node hosting radio link control (RLC), medium access control (MAC) and/or physical (PHY) layers of the NR protocol stack for the access node 104. The operations of the DU 105 may be at least partly controlled by the CU 108. It should also be understood that the distribution of functions between the DU 105 and the CU 108 may vary depending on the implementation.

Cloud computing systems may also be used to provide the CU 108 and/or DU 105. A CU provided by a cloud computing system may be referred to as a virtualized CU (vCU). In addition to the vCU, there may also be a virtualized DU (vDU) provided by a cloud computing system. Furthermore, there may also be a combination, where the DU may be implemented on so-called bare metal solutions, for example application-specific integrated circuit (ASIC) or customer-specific standard product (CSSP) system-on-a-chip (SoC).

Edge cloud may be brought into the radio access network by utilizing network function virtualization (NFV) and software defined networking (SDN). Using edge cloud may mean access node operations to be carried out, at least partly, in a computing system operationally coupled to a remote radio head (RRH) or a radio unit (RU) 103 of an access node 104. It is also possible that access node operations may be performed on a distributed computing system or a cloud computing system located at the access node 104. Application of cloud RAN architecture enables RAN real-time functions being carried out at the radio access network (e.g., in a DU 105), and non-real-time functions being carried out in a centralized manner (e.g., in a CU 108).

5G (or new radio, NR) wireless communication networks may support multiple hierarchies, where multi-access edge computing (MEC) servers may be placed between the core network 110 and the access node 104. It should be appreciated that MEC may be applied in LTE wireless communication networks as well.

A 5G wireless communication network (“5G network”) may also comprise a non-terrestrial communication network, such as a satellite communication network, to enhance or complement the coverage of the 5G radio access network. For example, satellite communication may support the transfer of data between the 5G radio access network and the core network 110, enabling more extensive network coverage. Possible use cases may include: providing service continuity for machine-to-machine (M2M) or Internet of Things (loT) devices or for passengers on board of vehicles, or ensuring service availability for critical communications, and future railway, maritime, or aeronautical communications. Satellite communication may utilize geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (i.e., systems in which hundreds of (nano)satellites are deployed). A given satellite 106 in the mega-constellation may cover several satellite-enabled network entities that create on-ground cells. The on-ground cells may be created through an on-ground relay access node or by an access node located on-ground or in a satellite.

It is obvious for a person skilled in the art that the access node 104 depicted in FIG. 1A is just an example of a part of a radio access network, and in practice the radio access network may comprise a plurality of access nodes 104, the UEs 100, 102 may have access to a plurality of radio cells, and the radio access network may also comprise other apparatuses, such as physical layer relay access nodes or other entities. At least one of the access nodes may be a Home eNodeB or a Home gNodeB. A Home gNodeB or a Home eNodeB is a type of access node that may be used to provide indoor coverage inside a home, office, or other indoor environment.

Additionally, in a geographical area of a radio access network, a plurality of different kinds of radio cells as well as a plurality of radio cells may be provided. Radio cells may be macro cells (or umbrella cells) which may be large cells having a diameter of up to tens of kilometers, or smaller cells such as micro-, femto- or picocells. The access node(s) 104 of FIG. 1A may provide any kind of these cells. A cellular radio network may be implemented as a multilayer access networks including several kinds of radio cells. In multilayer access networks, one access node may provide one kind of a radio cell or radio cells, and thus a plurality of access nodes may be needed to provide such a multilayer access network.

For fulfilling the need for improving performance of radio access networks, the concept of “plug-and-play” access nodes may be introduced. A radio access network, which may be able to use “plug-and-play” access nodes, may include, in addition to Home eNodeBs or Home gNodeBs, a Home Node B gateway (HNB-GW) (not shown in FIG. 1A). An HNB-GW, which may be installed within an operator’s radio access network, may aggregate traffic from a large number of Home eNodeBs or Home gNodeBs back to a core network 110 of the operator.

6G wireless communication networks are expected to adopt flexible decentralized and/or distributed computing systems and architecture and ubiquitous computing, with local spectrum licensing, spectrum sharing, infrastructure sharing, and intelligent automated management underpinned by mobile edge computing, artificial intelligence, short-packet communication and blockchain technologies. Key features of 6G may include intelligent connected management and control functions, programmability, integrated sensing and communication, reduction of energy footprint, trustworthy infrastructure, scalability and affordability. In addition to these, 6G is also targeting new use cases covering the integration of localization and sensing capabilities into system definition to unifying user experience across physical and digital worlds.

FIG. IB illustrates an example of a wireless communication system, to which some example embodiments may be applied. FIG. IB may be understood to depict a part of the wireless communication network of FIG. 1A, but with greater accuracy with respect to carrier aggregation (CA) and cell (re)selection.

Referring to FIG. IB, the access node 104 may provide a group of cells comprising a primary cell (PCell) 121 and one or more secondary cells (SCells) 122. The PCell 121 is a cell operating on a primary frequency that may be used for initial access. An SCell 122 is a cell, operating on a secondary frequency, which may be configured once an RRC connection is established, and which may be used to provide additional radio resources.

Carrier aggregation refers to a technology that enables the UE 100 to simultaneously utilize multiple frequency bands or carriers to transmit and receive data. In carrier aggregation, two or more carriers operating on different frequency bands may be aggregated together to create a wider "virtual" channel. For example, carrier aggregation may involve combining the resources of the PCell 121 and the one or more SCells 122 to create a wider virtual channel. The UE 100 may treat this virtual channel as a single high-capacity connection. This allows the UE 100 to receive and transmit data across multiple frequency bands, effectively increasing the available bandwidth and data rates.

When the UE 100 switches to idle (RRCJDLE) or inactive (RRCJNACT1VE) mode, the network (e.g., the access node 104) may configure the UE 100 (e.g., through RRC Release or cell broadcast information) to perform cell reselection measurements, i.e., to evaluate the signal strength, signal quality, and/or other network parameters of its serving cell and neighboring cells.

With cell (re)selection, the UE 100 searches for a suitable cell of the selected public land mobile network (PLMN) or selected stand-alone non-public network (SNPN), chooses that cell to provide available services, and monitors its control channel. This procedure is defined as "camping on the cell". If the UE 100 finds a more suitable cell than its current serving cell, according to the cell reselection criteria, the UE 100 reselects onto that cell and camps on it. For example, cell reselection may be based on measurements and evaluations of signal strength, quality, and/or other parameters of the current serving cell 121 and one or more neighboring cells 122, 131, 132. The UE 100 may autonomously make the decision to re-select a different cell in idle (RRCJDLE) mode, or if the UE 100 experiences a radio link failure.

For example, as the UE 100 is moving out of the coverage of the serving cell 121, the UE 100 may perform a cell reselection to switch from the serving cell 121 of the source access node 104 to a different cell 131 provided by a target access node 104A. Prior to connecting to the cell 131 of the target access node 104A, the UE may perform inter-frequency measurements on one or more cells 132 of the target access node 104A, while in the idle or inactive mode. Upon switching to connected mode with the serving cell 131 of the target access node 104A, the UE 100 may report the inter-frequency measurements to the access node 104A or 104 to help the target access node 104A to decide which SCell(s) 132 to add for the UE 100 for carrier aggregation.

The measurements of the serving cell performed by the UE may be based on the synchronization signal block (SSB) of the serving cell. The SSB is a signal that may be used for synchronization and cell identification purposes. For example, the UE may measure the synchronization signal reference signal received power (SS-RSRP) and/or the synchronization signal reference signal received quality (SS-RSRQ). SS-RSRP is a metric for the power of the secondary synchronization signal included in the SSB. SS-RSRQ is a metric for the signal quality of the secondary synchronization signal included in the SSB.

As energy resources are limited, it is desirable to improve the energy efficiency of wireless communication networks. Some techniques for enabling energy savings may include, for example, SSB-less cells, SSB on demand, system information block type 1 (S1B1) on demand etc.

An SSB-less cell means that the cell may transition to a mode where it stops broadcasting SSB based on a predetermined condition being met. This can contribute to reducing the energy consumption of the network, and therefore make the network more sustainable.

SSB on demand means that the access node 104 may stop periodic transmissions of the SSB of the cell, but a UE 100, 102 may request the access node 104 to transmit the SSB of the cell when it is needed.

S1B1 on demand means that the access node 104 may stop periodic transmissions of S1B1 of the cell, but a UE 100, 102 may request the access node 104 to transmit the S1B1 of the cell when it is needed (e.g., by transmitting a wakeup signal from the UE 100, 102 to the access node 104).

Given that networks are dimensioned for peak load, and that the number of hours that cells are at peak load may be relatively low, there is a large amount of time where the cells are at low or medium loads. These periods of times, when the cell load is low, are an opportunity for network energy savings. Networks can employ load balancing techniques and potentially turn off cells or leverage other energy saving features. One such feature could be SSB-less cell. While this is being enabled for SCells, an SCell may also act as a PCell, unless its employing supplementary downlink spectrum.

Since SCells may serve as PCells, for load balancing, for example when dealing with UL load in the absence of UL CA, it is challenging to utilize SSB-less SCells without the ability to leverage SSB-less PCells.

The absence of the SSB may require alternative mechanisms for tasks such as cell detection, synchronization, and system information acquisition. Therefore, to enable SSB-less PCell, there is a need for a mechanism to enable the UE to synchronize in time and frequency to the cell without the SSB of the cell.

The current specifications require a UE in RRC idle mode to perform measurements of SS-RSRP and/or SS-RSRQ of the SSB of the serving cell and compare the results to the measurements performed on candidate cells’ SSB for potential cell reselection.

Some example embodiments may provide a framework for a UE to camp on a serving cell, which may transition to SSB-less mode. This framework enables the UE to perform measurements of its serving cell (first cell), based on measuring at least one signal of a second cell, allowing the UE to proceed with established cell (re)selection procedures.

Instead of a serving cell in SSB-less mode, the framework may also be applied for measurements of one or more neighbor cells in SSB-less mode by providing a measurement configuration for one or more neighbor cells.

Lack of SSB in a cell means that the UE camping on the cell is unable to perform DL synchronization and cell reselection (for cell reselection, the UE needs to measure the SS-RSRP and/or SS-RSRQ of the serving cell and compare it with other cells on which reselection is possible). In some example embodiments, a second measurement configuration is provided, which includes at least one signal of the second cell, and possibly one or more (e.g., non-SSB) assistance signals of the SSB-less cell. For example, an assistance signal such as a tracking reference signal of the SSB-less cell can be used for DL synchronization. The at least one signal of the second cell may be used by the UE to determine whether to perform cell reselection.

In addition to SSB-less cells, the framework may also be applied to a cell with infrequent SSB transmission. As a non-limiting example, the infrequent SSB transmission may mean that the SSB is transmitted every 1000 milliseconds instead of every 20 milliseconds. In this case, the UE may measure the at least one signal of the second cell, when no SSB of the first cell is present, and then measure the SSB of the first cell every 1000 milliseconds for fine-tuning.

The example embodiments described herein may enable the use of SSB- less cells as serving cells for idle and inactive mode. Furthermore, some example embodiments may allow camping on a cell that is in an SSB-less (energy saving) mode by using another cell’s signals for serving cell measurements. Also, UE requirements in terms of having a measurable signal for timing, automatic gain control and frequency synchronization can be met without expecting major improvements in chipsets (e.g., hold times). Additionally, RRC setup time need not be impacted, given that a UE can initiate a transition to connected mode on an SSB- less cell. Without the possibility for a UE to camp on an SSB-less cell in idle or inactive mode, all the transitions to connected mode would require initial access to be performed via the second cell with SSB transmissions, and the second cell then could redirect the traffic as needed. Moreover, reacquisition of system information prior to validity time expiry before a cell goes into SSB-less mode enables higher network energy savings and enables the UE to reselect to other SSB-less cells.

Some example embodiments are described below using principles and terminology of 5G and 6G radio access technology without limiting the example embodiments to 5G and 6G radio access technology, however.

FIG. 2 illustrates a signal flow diagram according to an example embodiment.

Referring to FIG. 2, at 201, a UE 100 switches to an idle (RRCJDLE) mode or inactive (RRC JNACT1VE) mode. The UE 100 may be camping on a first cell 121 controlled by an access node 104. In other words, the first cell 121 may be the serving cell of the UE 100. Alternatively, the first cell 121 may be a neighbor cell of the serving cell of the UE 100. The first cell 121 is operating with periodic SSB transmissions.

At 202, the UE 100 determines a first measurement configuration indicating a first set of signals for measuring the first cell 121 controlled by the access node 104, wherein the first set of signals comprises at least a synchronization signal block of the first cell 121.

The determination may be based on a preconfigured set of signals (i.e., the first set of signals) for measurements of serving cells and/or a configuration received from the access node 104.

The first measurement configuration may have a default option predetermined in the specifications and variations provided to the UE in RRC connected mode, for example via RRC release. For example, the first set of signals to be measured may be hard-coded or pre-configured to the UE 100 according to specifications. The cell reselection criteria, such frequency layer priorities, SS- RSRP threshold, and/or SS-RSRQ threshold, may be received from the access node 104 in a configuration after the cell acquisition.

For example, the first set of signals may comprise at least one of: the synchronization signal block of the first cell, a channel state information reference signal (CS1-RS) of the first cell, or a tracking reference signal of the first cell.

At 203, the access node 104 transmits or broadcasts the synchronization signal block of the first cell 121.

At 204, the UE 100 performs one or more measurements (e.g., SS-RSRP and SS-RSRQ) of the first cell 121 based on the first set of signals according to the first measurement configuration, in order to determine when it needs to perform a cell (re)selection procedure. The UE 100 may use the first set of signals and the first measurement configuration to perform measurements of the first cell 121, unless the UE 100 determines that the first cell 121 has transitioned into SSB-less mode. At 205, the access node 104 generates a second measurement configuration indicating a second set of signals for measuring the first cell 121 controlled by the access node 104, wherein the second set of signals comprises at least one signal of a second cell 122 different from the first cell 121. The access node 104 transmits the second measurement configuration to the UE 100, which is pre-configured with or storing the first measurement configuration. For example, the access node 104 may transmit the second measurement configuration via system information of the first cell, or via dedicated RRC signaling (e.g., during RRC release). The UE 100 receives the second measurement configuration (e.g., via the system information or the dedicated RRC signaling).

The second measurement configuration enables the UE 100 to measure the first cell 121, when the first cell 121 is in SSB-less operation. When the first cell 121 is in SSB-less operation, the UE 100 may still need to maintain time and frequency synchronization with the first cell 121 and perform measurements of the first cell 121 for cell (re)selection. The second measurement configuration may indicate, for example, the periodicity and density of a given signal in the second set of signals.

The first cell 121 and the second cell 122 may be co-located (i.e., located at the same physical location), so that the at least one signal of the second cell 122 has a path loss correlation with the SSB of the first cell 121. For example, the first cell 121 and the second cell 122 may be controlled by the same access node 104 and share the same radio unit 103.

Alternatively, the first cell 121 and the second cell 122 may not be colocated. For example, in an indoor scenario or in a stadium, an offset of pathloss (or some other predetermined characteristic) between the first cell 121 (e.g., in the middle of the room or stadium) and the second cell 122 (e.g., around the stadium) may be sufficiently deterministic.

The at least one signal of the second cell 122 may comprise at least one of: a synchronization signal block of the second cell 122, a channel state information reference signal of the second cell 122, or a tracking reference signal of the second cell 122. In addition to the at least one signal of the second cell 122, the second set of signals may comprise one or more signals of the first cell (other than the SSB configuration of the first cell). In other words, the first set of signals and the second set of signals may partially overlap. For example, in addition to the at least one signal of the second cell 122, the second set of signals may comprise at least one of: the channel state information reference signal of the first cell 121, or the tracking reference signal of the first cell 121. The at least one signal of the second cell 122 may be transmitted on a different carrier frequency than the first set of signals of the first cell 121. The second set of signals may also comprise the synchronization signal block of the first cell 121, but with a longer periodicity compared to the expected periodicity indicated in the first measurement configuration.

The first cell 121 may be associated with a first radio access technology, and the second cell 122 may be associated with a second radio access technology different from the first radio access technology. For example, the first set of signals of the first cell may comprise at least one of: a 6G SSB, a 6G CSI-RS, or a 6G tracking reference signal, and the at least one signal of the second cell 122 may comprise at least one of: a 5G SSB, a 5G CSI-RS, or a 5G tracking reference signal.

For example, the first cell 121 and the second cell 122 may be part of a multi-RAT spectrum sharing (MRSS) deployment, where the first cell 121 is a 6G MRSS cell, and the second cell is a 5G MRSS cell.

Alternatively, the first cell 121 and the second cell 122 may be associated with the same radio access technology.

The first cell 121 and the second cell 122 may be intra-frequency cells operating on the same carrier frequency. As an example, the first cell 121 may be a 6G cell on one carrier frequency, and the second cell 122 may be a 5G or 6G cell on another carrier frequency.

Alternatively, the first cell 121 and the second cell 122 may be interfrequency cells operating on different carrier frequencies.

The second measurement configuration may further comprise an identifier, such as a physical cell identity (PCI), of the second cell 122, and quasicolocation (QCL) information between one or more signals of the first cell 121 and the at least one signal of the second cell 122. QCL refers to a certain relationship between different signals or channels. One interpretation of quasi-colocation is that the propagation channel of a physical channel has some correlation in the frequency domain or time or spatial domain with that of some reference signal. This means that at least some characteristics of the signal propagation are similar for both the physical channel and the reference signal. QCL implies that some information transmitted over one antenna port can be used to infer properties of the channel for another transmission over another antenna port. That is, when a reference signal is transmitted by one antenna port of the first cell 121, and another reference signal is transmitted on the second cell 122, it is possible to infer some properties of the channel of cell transmission based on the transmission of the first cell 121 based on a QCL relationship.

Alternatively, the second measurement configuration may comprise a list of candidate cells, i.e., a list of identifiers (e.g., PCls) of cells that may act as the second cell. As an example, the list of cells may be a prioritized list, meaning that the UE 100 should attempt to use the candidate cell with the highest priority as the second cell before attempting a candidate cell with a lower priority. In other words, the UE 100 should attempt to find an available (measurable and suitable) candidate cell with the highest possible priority.

The second measurement configuration may further comprise a power offset to be applied for the second cell 122 relative to the first cell 121. In case the second measurement configuration comprises the list of candidate cells, the second measurement configuration may comprise a power offset to be applied for each of the listed candidate cells. With the power offset, the UE 100 can adjust the measurements of the first cell 121 based on the measurements of the second cell 122.

At 206, the access node 104 determines, based on a predetermined condition being met (e.g., a load of the first cell 121 being below a threshold), to stop transmitting the synchronization signal block of the first cell 121 (i.e., to switch to SSB-less mode). For example, the predetermined condition may be based on the load of the first cell 121 (e.g., to switch to SSB-less mode when the load is low or below a threshold). It should be noted that, at 206, the access node 104 may not yet actually switch the first cell 121 to the SSB-less mode, but it just intends to do so and initiates procedures to operate in SSB-less mode.

At 207, based on determining to stop transmitting the synchronization signal block of the first cell 121, the access node 104 may transmit, to the UE 100, an indication or notification indicating to use the second set of signals for measuring the first cell 121. In other words, the indication indicates that the first cell 121 intends to transition to the SSB-less mode soon. The UE 100 may receive the indication.

This indication may be provided explicitly or implicitly. An example of an implicit indication would be via the first cell 121 suspending SSB transmissions and initiating the transmission of an assistance signal (e.g., tracking reference signal), which may be part of the second set of signals indicated in the second measurement configuration. The UE 100 may detect the absence of the SSB along with the presence of the assistance signal to determine that the first cell 121 has switched to SSB-less mode.

The explicit indication may be transmitted by the access node 104 via a groupcast, multicast or broadcast signal, such as the master information block (M1B) or system information block (SIB) or group common physical downlink control channel (PDCCH) of the first cell 121 transitioning into the SSB-less mode. Alternatively, the indication may be provided on another cell than the first cell 121.

The indication may also indicate when the UE 100 should start using the second set of signals. For example, the indication may indicate a point in time in the future when the UE 100 should start using the second set of signals (e.g., at the same time when the first cell 121 is transitioned to the SSB-less mode). Alternatively, the indication may indicate the UE 100 to start using the second set of signals immediately upon receiving the indication.

The access node 104 may change the value tag information element for the first cell 121 (which is transitioning to the SSB-less mode), even when there are no changes in the SIBs, thus forcing the UE 100 to reacquire the SIBs and restarting their validity timers. This may be beneficial for longer sleep periods for the SSB- less mode, minimizing the probability of having to exit the sleep state to provide SIBs to the UE 100.

At 208, based on receiving the indication (or detecting the changed value tag), the UE 100 reacquires system information of the first cell 121 before the access node 104 stops transmitting the SSB of the first cell 121, regardless of whether a validity timer of previously acquired system information of the first cell 121 has expired. The UE 100 may reset the validity timer upon reacquiring the system information of the first cell 121.

In other words, if the UE 100 receives the above indication, the UE 100 attempts to acquire the most recent SIBs of the first cell 121, even if their validity timer has not expired, and prioritizes its storage.

The reacquisition of the system information may be further subject to the time-to-expiry of the currently valid system information, l.e., if the time-to- expiry is less than a threshold, the UE may reacquire or refresh the system information and reset the validity timer(s). The threshold may be, for example, provided on the first cell 121 via broadcast information or specified in the specifications.

At 209, the access node 104 stops the transmission of the synchronization signal block of the first cell 121 after transmitting the indication (and after the UE 100 has reacquired the system information). In other words, the first cell 121 is transitioned to the SSB-less mode.

At 210, the UE 100 determines whether to apply the first measurement configuration or the second measurement configuration for measuring the first cell 121, wherein the determination is based at least on an availability of the synchronization signal block of the first cell 121. In other words, the UE 100 may determine whether the first cell 121 is operating in the SSB-less mode.

For example, based on receiving the indication, the UE 100 may determine to apply the second measurement configuration for measuring the first cell 121. In other words, based on receiving the indication, the UE 100 may determine that the first cell 121 is operating in the SSB-less mode. As an alternative to the indication, the UE 100 itself may determine whether the synchronization signal block of the first cell 121 has not been detected for a period of time larger than an expected periodicity of the synchronization signal block of the first cell 121. In this case, the determination of whether to apply the first measurement configuration or the second measurement configuration may be based at least on the determination of whether the synchronization signal block of the first cell 121 has not been detected for the period of time larger than the expected periodicity of the synchronization signal block of the first cell 121. In other words, if the synchronization signal block of the first cell 121 has not been detected for the period of time larger than the expected periodicity, then the UE 100 may determine to apply the second measurement configuration.

The UE 100 may further determine whether one or more other (e.g., non-SSB) signals of the first cell 121 are detected, the one or more other signals being comprised in the second set of signals and being different (or having a different periodicity) from the synchronization signal block of the first cell 121. The determination of whether to apply the first measurement configuration or the second measurement configuration may be based further on the determination of whether the one or more other signals of the first cell 121 are detected.

The UE 100 may further determine whether the at least one signal of the second cell 122 is detected, wherein the determination of whether to apply the first measurement configuration or the second measurement configuration may be based further on the determination of whether the at least one signal of the second cell 122 is detected.

For example, the UE 100 may determine to apply the second measurement configuration, if the UE 100 has not detected the SSB of the first cell 121 for the period of time larger than the expected periodicity, and the UE 100 has detected the one or more other signals of the first cell 121, and/or the UE 100 has detected the at least one signal of the second cell 122. In other words, the UE 100 may determine to apply the second measurement configuration, if the SSB of the first cell 121 is not available (with the expected periodicity), but the second set of signals is available. At 211, the UE 100 selects the second cell 122 from a list of candidate cells comprised in the second measurement configuration, wherein the selection is based on at least one of: a priority order of the candidate cells, or measurements of the candidate cells (e.g., selecting the candidate cell with the highest SS-RSRP and/or SS-RSRQ value).

At 212, the UE 100 may optionally determine a correction factor to be applied to one or more measurements of the first cell 121 when applying the second measurement configuration, wherein the determination of the correction factor is based on measurements of the first cell 121 and the second cell 122. The measurements used for determining the correction factor may be based on an SSB or any other signal of the first cell 121 and the second cell 122.

In other words, the UE 100 may utilize its own measurements to compensate and improve accuracy of the one or more measurements of the first cell 121 that are based on the second measurement configuration. For example, the correction factor may be used to correct for propagation differences between the first cell 121 and the second cell 122, which are not deterministic. The correction factor may be used as an alternative or together with the power offset that may be indicated in the second measurement configuration.

At 213, the access node 104 may transmit one or more other (e.g., non- SSB) signals of the first cell 121, which may be included in the second set of signals.

At 214, the access node 104 transmits the at least one signal of the second cell 122, which is included in the second set of signals.

At 215, based on determining to apply the second measurement configuration, the UE 100 performs one or more measurements of the first cell 121 according to the second measurement configuration, wherein the one or more measurements are performed in the idle mode or in the inactive mode.

In case the second measurement configuration indicated the power offset, then the UE 100 may perform the one or more measurements of the first cell 121 by applying the power offset to one or more measurements obtained from the at least one signal of the second cell 122, based on determining to apply the second measurement configuration. For example, if the measured RSRP for the SSB of the second cell is -110 decibel-milliwatts, then the power offset may be added to the measurement (-110 decibel-milliwatts + power offset) for determining the measurement of the first cell 121. When the first cell 121 and the second cell 122 are co-located and intra-frequency or inter-frequency cells, the power offset may be applied to account for at least one of: propagation differences due to frequency, equivalent isotropic radiated power (E1RP) differences between the cells, and/or possible corrections for differences in beam patterns of the cells.

When applying the second measurement configuration, the UE 100 may perform the one or more measurements of the first cell 121 with assistance from one or more measurements of the second cell 122 (i.e., based on the at least one signal of the second cell 122). For example, the UE 100 may measure the reference signal received power (RSRP) of the at least one signal of the second cell 122, and apply the power offset to the RSRP of the second cell 122 to obtain an RSRP measurement of the first cell 121.

Alternatively, or additionally, the UE 100 may apply the correction factor (from 212) to the one or more measurements of the first cell 121 performed according to the second measurement configuration. For example, the UE 100 may measure the at least one signal of the second cell 122 (denoted as M_cell2), measure the one or more other signals of the first cell 121 (denoted as M_celll), and determine the RSRP of the first cell 121 for example as:

M_cell2 * alpha + M_celll * beta + preconfigured offset where the preconfigured offset is the power offset that may be provided in the second measurement configuration, and alpha and beta are weighting factors (i.e., parts of the correction factor) that may be provided in the second measurement configuration and/or determined by the UE 100 (at 212) based on measurement data (e.g., SSB measurements) of the first cell 121 (or its frequency) in relation to measurements (e.g., SSB measurements) of the second cell 122 (or its frequency).

At 216, based on determining to apply the second measurement configuration, the UE 100 may evaluate one or more cell reselection criteria based on the second set of signals (i.e., based on measurements of the second set of signals), wherein the one or more cell reselection criteria are associated with the first cell 121. In other words, when applying the second measurement configuration, the UE 100 may perform cell (re)selection based on the same criteria as if the measurements of the first cell 121 were performed on the first set of signals. The UE 100 may or may not perform a cell reselection from the first cell 121 based on the evaluation.

Alternatively, the UE 100 may perform cell (re)selection if the first cell 121 enters an unknown state. A known cell state may be based on at least one of: the UE has valid timing and frequency measurement of the second cell 122 and the first cell 121; the second cell 122 remains detectable and specific cell identification of the second cell 122 maps to the preconfigured value provided in the second measurement configuration; all the signals defined in the second set of signals remain detectable; and the UE 100 has a valid version of the system information of the first cell 121 (i.e., the validity timer has not expired).

For example, based on determining to apply the second measurement configuration (or when applying the second measurement configuration), the UE 100 may detect that the second set of signals are not measurable or that system information for the first cell 121 is no longer valid. The UE 100 may perform a cell reselection from the first cell 121 based on detecting that the second set of signals are not measurable or that the system information for the first cell 121 is no longer valid.

In another embodiment, the second set of signals may be used by the UE 100 only for time and frequency synchronization purposes, not for measurement.

FIG. 3 illustrates an example of a configuration of the second set of signals for SSB-less operation. In this example, it can be observed that when the first cell (cell 1) 121 initiates operation in SSB-less mode at 300, it suspends transmission of SSB 311 and starts transmissions of an assistance signal 312 for the UE 100. This assistance signal may be, for example, a specific configuration of a tracking reference signal of the first cell 121. In this example, the second set of signals, which the UE 100 may use to perform measurements of the first cell 121 in the SSB-less mode, may comprise the tracking reference signal 312 of the first cell 121 and the SSB 321 of the second cell (cell 2) 122. In addition to the second set of signals, the second measurement configuration may indicate the power offset (or power differences) between transmissions of the first cell 121 and transmissions of the second cell 122, and/or an identifier (e.g., PCI) of the second cell 122 and QCL information between signals of the first cell 121 and the second cell 122. As described above, the first cell 121 and the second cell 122 may be based on the same or different RAT and operate on the same or different carrier frequency.

A UE attempting to perform cell reselection to the SSB-less cell (e.g., the first cell 121) may perform the measurements of the SSB-less cell based on the second set of signals. The UE may receive the measurement configuration for the SSB-less cell (e.g., the first cell 121) from its serving cell.

It may be challenging for a UE to select a cell (e.g., the first cell 121) that is in SSB-less mode. The cell may be operating in SSB-less mode because of low network load, and there should be other cells to which the UE can synchronize as well. If it is required to be able to perform cell selection to an SSB-less cell, a minimum configuration of the assistance signal 312 of the SSB-less cell maybe preconfigured in the specifications. For example, the specifications may specify a default periodicity, coding and time and frequency patterns of this assistance signal 312.

FIG. 4 illustrates a flow chart according to an example embodiment of a method for determining the measurement configuration to be applied. The method of FIG. 4 may be performed by an apparatus 1000 depicted in FIG. 10. For example, the apparatus 1000 may be, or comprise, or be comprised in, a user equipment (UE) 100, 102.

Referring to FIG. 4, in block 401, the apparatus 1000 determines or obtains a first measurement configuration indicating a first set of signals for measuring a first cell 121 controlled by an access node 104, wherein the first set of signals comprises at least a synchronization signal block 311 of the first cell 121. For example, the apparatus 1000 may receive the first measurement configuration from the access node 104. As another example, the first set of signals may be predefined (e.g., preconfigured or hardcoded) at the apparatus 1000 for serving cell measurements, and the apparatus 1000 may determine the first measurement configuration based on the pre-defined first set of signals and/or a configuration received from the access node 104.

In block 402, the apparatus 1000 determines or obtains a second measurement configuration indicating a second set of signals for measuring the first cell 121 controlled by the access node 104, wherein the second set of signals comprises at least one signal 321 of a second cell 122 different from the first cell 121. For example, the second measurement configuration may be received from the access node 104. As another example, the second set of signals may be predefined (e.g., preconfigured or hardcoded) at the apparatus 1000, and the apparatus 1000 may determine the second measurement configuration based on the pre-defined second set of signals and/or a configuration received from the access node 104.

In block 403, the apparatus 1000 determines whether to apply the first measurement configuration or the second measurement configuration for measuring the first cell 121, wherein the determination is based at least on an availability of the synchronization signal block 311 of the first cell 121.

In block 404, the apparatus 1000 performs, based on the determination of whether to apply the first measurement configuration or the second measurement configuration, one or more measurements of the first cell 121, wherein the one or more measurements are performed in an idle mode or in an inactive mode.

The first cell 121 and the second cell 122 may be co-located.

The first cell 121 may be associated with a first radio access technology, and the second cell 122 may be associated with a second radio access technology different from the first radio access technology.

The at least one signal 321 of the second cell may comprise at least one of: a synchronization signal block of the second cell 122, a channel state information reference signal of the second cell 122, or a tracking reference signal of the second cell 122. The second measurement configuration may further comprise an identifier of the second cell 122, and quasi-colocation information between one or more signals 312 of the first cell 121 and the at least one signal 321 of the second cell 122.

The apparatus 1000 may select the second cell 122 from a list of candidate cells that may be comprised in the second measurement configuration. The selection may be based on at least one of: a priority order of the candidate cells, or measurements of the candidate cells.

The second measurement configuration may further comprise a power offset to be applied for the second cell 122 relative to the first cell 121. The apparatus 1000 may perform the one or more measurements of the first cell 121 by applying the power offset to one or more measurements obtained from the at least one signal 321 of the second cell 122, based on determining to apply the second measurement configuration.

The apparatus 1000 may determine a correction factor to be applied to the one or more measurements of the first cell 121 when applying the second measurement configuration, wherein the determination of the correction factor may be based on measurements of the first cell 121 and the second cell 122. Based on determining to apply the second measurement configuration, the apparatus 1000 may apply the correction factor to the one or more measurements of the first cell 121 performed according to the second measurement configuration.

The apparatus 1000 may receive, from the access node 104, an indication indicating to use the second set of signals for measuring the first cell 121; and based on receiving the indication, reacquire system information of the first cell 121, regardless of whether a validity timer of previously acquired system information of the first cell 121 has expired. In this case, the determination of whether to apply the first measurement configuration or the second measurement configuration may comprise determining to apply the second measurement configuration, based on receiving the indication.

Alternatively, the apparatus 1000 may determine whether the synchronization signal block 311 of the first cell 121 has not been detected for a period of time larger than an expected periodicity of the synchronization signal block 311 of the first cell 121. The determination of whether to apply the first measurement configuration or the second measurement configuration may be based at least on the determination of whether the synchronization signal block 311 of the first cell 121 has notbeen detected for the period of time larger than the expected periodicity of the synchronization signal block 311 of the first cell 121.

Based on determining to apply the second measurement configuration, the apparatus 1000 may evaluate one or more cell reselection criteria based on the second set of signals, wherein the one or more cell reselection criteria are associated with the first cell 121; and perform a cell reselection from the first cell 121 based on the evaluation.

Based on determining to apply the second measurement configuration, the apparatus 1000 may detect that the second set of signals are not measurable or that system information for the first cell 121 is no longer valid; and perform a cell reselection from the first cell 121 based on detecting that the second set of signals are not measurable or that the system information for the first cell 121 is no longer valid.

FIG. 5 illustrates a flow chart according to an example embodiment of a method for determining the measurement configuration to be applied. The method of FIG. 5 may be performed by an apparatus 1000 depicted in FIG. 10. For example, the apparatus 1000 may be, or comprise, or be comprised in, a user equipment (UE) 100, 102.

Referring to FIG. 5, in block 501, the apparatus 1000 determines a first measurement configuration indicating a first set of signals for measuring a first cell 121 controlled by an access node 104, wherein the first set of signals comprises at least a synchronization signal block 311 of the first cell 121. In other words, the apparatus 1000 may be preconfigured with the first measurement configuration.

In block 502, the apparatus 1000 performs one or more measurements of the first cell 121 based on the first set of signals according to the first measurement configuration. In block 503, the apparatus 1000 receives, from the access node 104, a second measurement configuration indicating a second set of signals for measuring the first cell 121 controlled by the access node 104, wherein the second set of signals comprises at least one signal 321 of a second cell 122 different from the first cell 121.

In block 504, the apparatus 1000 receives, from the access node 104, an indication indicating to use the second set of signals for measuring the first cell 121.

In block 505, based on receiving the indication, the apparatus 1000 reacquires system information of the first cell 121, regardless of whether a validity timer of previously acquired system information of the first cell 121 has expired.

In block 506, based on receiving the indication, the apparatus 1000 determines to apply the second measurement configuration.

In block 507, the apparatus 1000 performs, based on the determination of whether to apply the first measurement configuration or the second measurement configuration, one or more measurements of the first cell 121, wherein the one or more measurements are performed in an idle mode or in an inactive mode.

FIG. 6 illustrates a flow chart according to an example embodiment of a method for determining the measurement configuration to be applied. The method of FIG. 6 may be performed by an apparatus 1000 depicted in FIG. 10. For example, the apparatus 1000 may be, or comprise, or be comprised in, a user equipment (UE) 100, 102.

Referring to FIG. 6, in block 601, the apparatus 1000 determines a first measurement configuration indicating a first set of signals for measuring a first cell 121 controlled by an access node 104, wherein the first set of signals comprises at least a synchronization signal block 311 of the first cell 121.

In block 602, the apparatus 1000 receives, from the access node 104, a second measurement configuration indicating a second set of signals for measuring the first cell 121 controlled by the access node 104, wherein the second set of signals comprises at least one signal 321 of a second cell 122 different from the first cell 121. In block 603, the apparatus 1000 determines whether the synchronization signal block 311 of the first cell 121 has not been detected for a period of time larger than an expected periodicity of the synchronization signal block 311 of the first cell 121.

In block 604, the apparatus 1000 determines whether one or more other signals 312 of the first cell 121 are detected, the one or more other signals being comprised in the second set of signals and being different from the synchronization signal block 311 of the first cell 121.

In block 605, the apparatus 1000 determines whether the at least one signal 321 of the second cell 122 is detected.

In block 606, the apparatus 1000 determines to apply the second measurement configuration, based on determining that the synchronization signal block 311 of the first cell 121 has not been detected for the period of time larger than the expected periodicity of the synchronization signal block 311 of the first cell (block 603: no), and based on determining that the one or more other signals 312 of the first cell 121 are detected (block 604: yes), and based on determining that the at least one signal 321 of the second cell 122 is detected (block 605: yes). In other words, the apparatus 1000 determines to apply the second measurement configuration, if the SSB 311 of the first cell 121 has not been detected, and if the second set of signals has been detected.

Otherwise, in block 607, the apparatus 1000 may determine to apply the first measurement configuration, based on determining that the synchronization signal block 311 of the first cell 121 has been detected according to the expected periodicity (block 603: yes), or based on determining that the one or more other signals 312 of the first cell 121 are not detected (block 604: no), or based on determining that the at least one signal 321 of the second cell 122 is not detected (block 605: no).

In block 608, the apparatus 1000 performs one or more measurements of the first cell 121 by applying the second measurement configuration (following block 606) or by applying the first measurement configuration (following block 607), wherein the one or more measurements are performed in an idle mode or in an inactive mode.

FIG. 7 illustrates a flow chart according to an example embodiment of a method for providing a measurement configuration to a user equipment 100, 102. The method of FIG. 7 may be performed by an apparatus 1100 depicted in FIG. 11. For example, the apparatus 1100 may be, or comprise, or be comprised in, an access node 104 of a radio access network.

Referring to FIG. 7, in block 701, the apparatus 1100 generates a second measurement configuration indicating a second set of signals for measuring a first cell 121 controlled by the access node 104, wherein the second set of signals comprises at least one signal 321 of a second cell 122 different from the first cell 121.

In block 702, the apparatus 1100 transmits the second measurement configuration to a user equipment 100, 102 pre-configured with or storing a first measurement configuration indicating a first set of signals for measuring the first cell 121 controlled by the access node 104, wherein the first set of signals comprises at least a synchronization signal block 311 of the first cell 121.

For example, the pre-configuration of the first measurement configuration may mean that the user equipment 100, 102 has previously determined the first measurement configuration based on the first set of signals that may be pre-defined (e.g., preconfigured or hardcoded) at the user equipment 100, 102, and/or based on a configuration transmitted by the access node 104 to the user equipment 100, 102.

As another example, the pre-configuration of the first measurement configuration may mean that the access node 104 has previously transmitted the first measurement configuration to the user equipment 100, 102.

In an embodiment, the apparatus 1100 further generates the first measurement configuration indicating the first set of signals for measuring the first cell 121. The apparatus 1100 may transmit the first measurement configuration to the user equipment 100, 102. The apparatus 1100 may determine, based on a predetermined condition being met, to stop transmitting the synchronization signal block 311 of the first cell 121. Based on determining to stop the transmission of the synchronization signal block 311 of the first cell 121, the apparatus 1100 may transmit, to the user equipment 100, 102, an indication indicating to use the second set of signals for measuring the first cell 121. The apparatus 1100 may stop the transmission of the synchronization signal block 311 of the first cell 121 after transmitting the indication.

The first cell 121 and the second cell 122 may be co-located. The first cell 121 and the second cell 122 may both be controlled by the access node 104.

The at least one signal 321 of the second cell may comprise at least one of: a synchronization signal block 311 of the second cell 122, a channel state information reference signal of the second cell 122, or a tracking reference signal of the second cell 122.

The second measurement configuration may further comprise an identifier of the second cell 122, and quasi-colocation information between one or more signals 312 of the first cell 121 and the at least one signal 321 of the second cell 122.

Alternatively, or additionally, the second measurement configuration may comprise of a list of candidate cells for the second cell 122 in a priority order.

The second measurement configuration may further comprise a power offset to be applied for the second cell 122 relative to the first cell 121.

FIG. 8 illustrates a flow chart according to an example embodiment of a method for reacquiring system information. The method of FIG. 8 may be performed by an apparatus 1000 depicted in FIG. 10. For example, the apparatus 1000 may be, or comprise, or be comprised in, a user equipment (UE) 100, 102.

Referring to FIG. 8, in block 801, the apparatus 1000 determines that a cell 121 is applying or will be transitioning to an energy-saving mode, wherein the energy-saving mode comprises that a (periodic) transmission of one or more system information blocks of the cell 121 is stopped, or that a transmission periodicity of the one or more system information blocks of the cell 121 is increased. The apparatus 1000 may be in an idle (RRCJDLE) mode or in an inactive (RRCJNACT1VE) mode during the determination.

For example, the energy-saving mode may refer to SSB-less cell, SSB on demand, or S1B1 on demand. In the case of an SSB-less cell, there is no transmission of a master information block, and therefore also no transmission of S1B1 or other system information blocks.

The cell 121 may comprise a serving cell of the apparatus 1000, or a neighbor cell of the serving cell.

System information blocks (SIBs) are messages that are broadcasted by the network (e.g., the access node 104) to keep UEs updated about various parameters of the network. These parameters may include, for example, cell selection, cell reselection, power control, discontinuous reception (DRX) parameters, etc.

In block 802, based on the determination, the apparatus 1000 reacquires system information of the cell 121 from the one or more system information blocks before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell 121 has expired. The apparatus 1000 may be in the idle (RRCJDLE) mode or in the inactive (RRCJNACT1VE) mode during the reacquisition of the system information.

The apparatus 1000 may reacquire the system information of the cell 121 before the expiration of the validity timer.

In block 803, the apparatus 1000 may reset the validity timer based on reacquiring the system information.

In one example embodiment, the apparatus 1000 may receive, from an access node 104 controlling the cell 121, an indication indicating that the cell 121 will be transitioning to the energy-saving mode, wherein the determination of block 801 may be based on the indication. The indication may indicate a time when the cell 121 will be transitioning to the energy-saving mode. The apparatus 1000 may initiate the reacquisition of the system information before the time when the cell 121 will be transitioning to the energy-saving mode.

Alternatively, or additionally, the indication may indicate a time threshold within which the system information is to be reacquired, the time threshold being relative to the expiration of the validity timer. The apparatus 1000 may reacquire the system information based on determining that a remaining time to the expiration of the validity timer is less than the time threshold, the remaining time being higher than zero. In other words, if the validity timer is going to expire soon, then the apparatus 1000 may reacquire the system information, even if the validity timer has not actually expired yet. However, the apparatus 1000 does not need to reacquire the system information, if the remaining time to the expiration of the validity timer is above the threshold (e.g., if the apparatus 1000 just recently acquired the system information, and thus the validity timer is not going to expire soon). This may help to save energy at the apparatus 1000.

In another example embodiment, the apparatus 1000 may detect an on- demand system information block transmission (e.g., S1B1 on demand) of the cell 121, wherein the on-demand system information block transmission (implicitly) indicates that the cell 121 is applying the energy-saving mode. In this case, the apparatus 1000 may reacquire the system information from the detected on- demand system information block transmission. The on-demand system information block transmission may be transmitted from the access node 104 controlling the cell 121. For example, another user equipment may have requested the access node 104 to transmit the on-demand system information block transmission. The determination of block 801 may be based on detecting the on- demand system information block transmission.

In another example embodiment, the determination of block 801 may be based on historical data of the cell 121, the historical data indicating a pattern of the cell 121 being in the energy-saving mode or potentially transitioning to the energy-saving mode. For example, the historical data may indicate a certain time of the day when the cell 121 has historically transitioned to the energy-saving mode.

In an example embodiment, there is provided a method performed by an apparatus 1000 or a user equipment 100, 102, the method comprising: receiving, from an access node 104 controlling a serving cell 121 of the user equipment 100, 102, an indication indicating that a transmission of a synchronization signal block will be stopped on the serving cell 121; and based on receiving the indication, reacquiring system information of the serving cell 121 before the transmission of the synchronization signal block is stopped, regardless of whether a validity timer of previously acquired system information of the serving cell 121 has expired. The indication may indicate a time when the transmission of the synchronization signal block will be stopped, wherein the apparatus 1000 or the user equipment 100, 102 may reacquire the system information before the time when the transmission of the synchronization signal block will be stopped. The indication may indicate a time threshold for reacquiring the system information, wherein the apparatus 1000 or the user equipment 100, 102 may reacquire the system information based on determining that a remaining time to the expiration of the validity timer is less than the time threshold. The apparatus 1000 or the user equipment 100, 102 may reset the validity timer based on reacquiring the system information.

FIG. 9 illustrates a flow chart according to an example embodiment of a method for indicating one or more user equipments 100, 102 to reacquire system information. The method of FIG. 9 may be performed by an apparatus 1100 depicted in FIG. 11. For example, the apparatus 1100 may be, or comprise, or be comprised in, an access node 104 of a radio access network.

Referring to FIG. 9, in block 901, the apparatus 1100 determines, based on a predetermined condition being met, to transition a cell 121 controlled by the apparatus 1100 or the access node 104 to an energy-saving mode, wherein the energy-saving mode comprises that a (periodic) transmission of one or more system information blocks of the cell 121 is stopped, or that a transmission periodicity of the one or more system information blocks of the cell 121 is increased.

The predetermined condition may be related to a load of the cell 121. For example, the apparatus 1100 may determine to transition the cell to the energy-saving mode, if he load the cell 121 is below a threshold.

In block 902, based on determining to transition the cell 121 to the energy-saving mode, the apparatus 1100 transmits, to one or more user equipments 100, 102, an indication indicating that the cell 121 is applying or will be transitioning to the energy-saving mode.

The indication indicates the one or more user equipments 100, 102 to reacquire system information of the cell 121 before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired at the one or more user equipments 100, 102.

It is possible that the transmission of the one or more system information blocks of the cell 121 continues for a brief moment after the cell 121 transitions to the energy-saving mode.

The indication may be an explicit indication or an implicit indication. An on-demand system information block transmission is one example of an implicit indication of the cell 121 being in the energy-saving mode or transitioning to the energy-saving mode.

The indication may indicate a time when the cell 121 will be transitioning to the energy-saving mode.

Alternatively, or additionally, the indication may indicate a time threshold within which the system information is to be reacquired, the time threshold being relative to the expiration of the validity timer.

In an example embodiment, there is provided a method performed by an apparatus 1100 or an access node 104 of a radio access network, the method comprising: determining, based on a predetermined condition being met, to stop transmitting a synchronization signal block of a serving cell 121 of one or more user equipments 100, 102; and, based on determining to stop the transmission of the synchronization signal block of the serving cell 121, transmitting, to the one or more user equipments 100, 102, an indication indicating that the transmission of the synchronization signal block will be stopped on the serving cell 121 controlled by the access node 104. The predetermined condition may be related to a load of the serving cell 121. The indication may indicate a time when the transmission of the synchronization signal block will be stopped. The indication may indicate the one or more user equipments 100, 102 to reacquire system information of the serving cell 121 before the transmission of the synchronization signal block is stopped, regardless of whether a validity timer of previously acquired system information of the serving cell 121 has expired. The indication may indicate a time threshold for reacquiring the system information based on a remaining time to the expiration of the validity timer being less than the time threshold.

The blocks, related functions, and information exchanges (messages) described above by means of FIGS. 2 and 4 to 9 are in no absolute chronological order, and some of them may be performed simultaneously or in an order differing from the described one. Other functions can also be executed between them or within them, and other information may be sent, and/or other rules applied. Some of the blocks or part of the blocks or one or more pieces of information can also be left out or replaced by a corresponding block or part of the block or one or more pieces of information.

As used herein, “at least one of the following: <a list of two or more elements>” and “at least one of <a list of two or more elements>” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

FIG. 10 illustrates an example of an apparatus 1000 comprising means for performing one or more of the example embodiments (e.g., the method of FIG. 4, 5, 6 or 8) described above. For example, the apparatus 1000 may be an apparatus such as, or comprising, or comprised in, a user equipment (UE) 100, 102.

The apparatus 1000 may comprise a circuitry or a chipset applicable for realizing one or more of the example embodiments described above. For example, the apparatus 1000 may comprise at least one processor 1010. The at least one processor 1010 interprets instructions (e.g., computer program instructions) and processes data. The at least one processor 1010 may comprise one or more programmable processors. The at least one processor 1010 may comprise programmable hardware with embedded firmware and may, alternatively or additionally, comprise one or more application-specific integrated circuits (ASICs).

The at least one processor 1010 is coupled to at least one memory 1020. The at least one processor is configured to read and write data to and from the at least one memory 1020. The at least one memory 1020 may comprise one or more memory units. The memory units may be volatile or non-volatile. It is to be noted that there may be one or more units of non-volatile memory and one or more units of volatile memory or, alternatively, one or more units of non-volatile memory, or, alternatively, one or more units of volatile memory. Volatile memory may be for example random-access memory (RAM), dynamic random-access memory (DRAM) or synchronous dynamic random-access memory (SDRAM). Non-volatile memory may be for example read-only memory (ROM), programmable read-only memory (PROM), electronically erasable programmable read-only memory (EEPROM), flash memory, optical storage or magnetic storage. In general, memories may be referred to as non-transitory computer readable media. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM). The at least one memory 1020 stores computer readable instructions that are executed by the at least one processor 1010 to perform one or more of the example embodiments described above. For example, non-volatile memory stores the computer readable instructions, and the at least one processor 1010 executes the instructions using volatile memory for temporary storage of data and/or instructions. The computer readable instructions may refer to computer program code.

The computer readable instructions may have been pre-stored to the at least one memory 1020 or, alternatively or additionally, they may be received, by the apparatus, via an electromagnetic carrier signal and/or may be copied from a physical entity such as a computer program product. Execution of the computer readable instructions by the at least one processor 1010 causes the apparatus 1000 to perform one or more of the example embodiments described above. That is, the at least one processor and the at least one memory storing the instructions may provide the means for providing or causing the performance of any of the methods and/or blocks described above.

In the context of this document, a “memory” or “computer-readable media” or “computer-readable medium” may be any non-transitory media or medium or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

The apparatus 1000 may further comprise, or be connected to, an input unit 1030. The input unit 1030 may comprise one or more interfaces for receiving input. The one or more interfaces may comprise for example one or more temperature, motion and/or orientation sensors, one or more cameras, one or more accelerometers, one or more microphones, one or more buttons and/or one or more touch detection units. Further, the input unit 1030 may comprise an interface to which external devices may connect to.

The apparatus 1000 may also comprise an output unit 1040. The output unit may comprise or be connected to one or more displays capable of rendering visual content, such as a light emitting diode (LED) display, a liquid crystal display (LCD) and/or a liquid crystal on silicon (LCoS) display. The output unit 1040 may further comprise one or more audio outputs. The one or more audio outputs may be for example loudspeakers.

The apparatus 1000 further comprises a connectivity unit 1050. The connectivity unit 1050 enables wireless connectivity to one or more external devices. The connectivity unit 1050 comprises at least one transmitter and at least one receiver that may be integrated to the apparatus 1000 or that the apparatus 1000 may be connected to. The at least one transmitter comprises at least one transmission antenna, and the at least one receiver comprises at least one receiving antenna. The connectivity unit 1050 may comprise an integrated circuit or a set of integrated circuits that provide the wireless communication capability for the apparatus 1000. Alternatively, the wireless connectivity may be a hardwired application-specific integrated circuit (ASIC). The connectivity unit 1050 may also provide means for performing at least some of the blocks or functions of one or more example embodiments described above. The connectivity unit 1050 may comprise one or more components, such as: power amplifier, digital front end (DFE), analog-to-digital converter (ADC), digital-to-analog converter (DAC), frequency converter, (de) modulator, and/or encoder/decoder circuitries, controlled by the corresponding controlling units.

It is to be noted that the apparatus 1000 may further comprise various components not illustrated in FIG. 10. The various components may be hardware components and/or software components.

FIG. 11 illustrates an example of an apparatus 1100 comprising means for performing one or more of the example embodiments (e.g., the method of FIG. 7 or 9) described above. For example, the apparatus 1100 may be an apparatus such as, or comprising, or comprised in, an access node 104 of a radio access network.

The apparatus 1100 may comprise, for example, a circuitry or a chipset applicable for realizing one or more of the example embodiments described above. The apparatus 1100 may be an electronic device comprising one or more electronic circuitries. The apparatus 1100 may comprise a communication control circuitry 1110 such as at least one processor, and at least one memory 1120 storing instructions 1122 which, when executed by the at least one processor, cause the apparatus 1100 to carry out one or more of the example embodiments described above. Such instructions 1122 may, for example, include computer program code (software). The at least one processor and the at least one memory storing the instructions may provide the means for providing or causing the performance of any of the methods and/or blocks described above.

The processor is coupled to the memory 1120. The processor is configured to read and write data to and from the memory 1120. The memory 1120 may comprise one or more memory units. The memory units may be volatile or non-volatile. It is to be noted that there may be one or more units of non-volatile memory and one or more units of volatile memory or, alternatively, one or more units of non-volatile memory, or, alternatively, one or more units of volatile memory. Volatile memory may be for example random-access memory (RAM), dynamic random-access memory (DRAM) or synchronous dynamic random-access memory (SDRAM). Non-volatile memory may be for example read-only memory (ROM), programmable read-only memory (PROM), electronically erasable programmable read-only memory (EEPROM), flash memory, optical storage or magnetic storage. In general, memories may be referred to as non-transitory computer readable media. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM). The memory 1120 stores computer readable instructions that are executed by the processor. For example, non-volatile memory stores the computer readable instructions, and the processor executes the instructions using volatile memory for temporary storage of data and/or instructions.

The computer readable instructions may have been pre-stored to the memory 1120 or, alternatively or additionally, they may be received, by the apparatus, via an electromagnetic carrier signal and/or may be copied from a physical entity such as a computer program product. Execution of the computer readable instructions causes the apparatus 1100 to perform one or more of the functionalities described above.

The memory 1120 may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and/or removable memory. The memory may comprise a configuration database for storing configuration data, such as a current neighbour cell list, and, in some example embodiments, structures of frames used in the detected neighbour cells. The apparatus 1100 may further comprise or be connected to a communication interface 1130, such as a radio unit, comprising hardware and/or software for realizing communication connectivity with one or more wireless communication devices according to one or more communication protocols. The communication interface 1130 comprises at least one transmitter (Tx) and at least one receiver (Rx) that may be integrated to the apparatus 1100 or that the apparatus 1100 may be connected to. The communication interface 1130 may provide means for performing some of the blocks and/or functions (e.g., transmitting and receiving) for one or more example embodiments described above. The communication interface 1130 may comprise one or more components, such as: power amplifier, digital front end (DFE), analog-to-digital converter (ADC), digital-to-analog converter (DAC), frequency converter, (de) modulator, and/or encoder/decoder circuitries, controlled by the corresponding controlling units.

The communication interface 1130 provides the apparatus with radio communication capabilities to communicate in the wireless communication network. The communication interface may, for example, provide a radio interface to one or more UEs 100, 102. The apparatus 1100 may further comprise or be connected to another interface towards a core network 110, such as the network coordinator apparatus or AMF, and/or to the access nodes of the wireless communication network.

The apparatus 1100 may further comprise a scheduler 1140 that is configured to allocate radio resources. The scheduler 1140 may be configured along with the communication control circuitry 1110 or it may be separately configured.

It is to be noted that the apparatus 1100 may further comprise various components not illustrated in FIG. 11. The various components may be hardware components and/or software components.

As used in this application, the term “circuitry” may refer to one or more or all of the following: a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry); and b) combinations of hardware circuits and software, such as (as applicable): i) a combination of analog and/or digital hardware circuit(s) with software/firmware and ii) any portions of hardware processor(s) with software (including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone, to perform various functions); and c) hardware circuit(s) and/or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (for example firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

The techniques and methods described herein may be implemented by various means. For example, these techniques may be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or combinations thereof. For a hardware implementation, the apparatus(es) of example embodiments may be implemented within one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), graphics processing units (GPUs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. For firmware or software, the implementation can be carried out through modules of at least one chipset (for example procedures, functions, and so on) that perform the functions described herein. The software codes maybe stored in a memory unit and executed by processors. The memory unit may be implemented within the processor or externally to the processor. In the latter case, it can be communicatively coupled to the processor via various means, as is known in the art. Additionally, the components of the systems described herein may be rearranged and/or complemented by additional components in order to facilitate the achievements of the various aspects, etc., described with regard thereto, and they are not limited to the precise configurations set forth in the given figures, as will be appreciated by one skilled in the art.

It will be obvious to a person skilled in the art that, as technology advances, the inventive concept may be implemented in various ways within the scope of the claims. The embodiments are not limited to the example embodiments described above, but may vary within the scope of the claims. Therefore, all words and expressions should be interpreted broadly, and they are intended to illustrate, not to restrict, the embodiments.

Claims

1. A user equipment comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to: determine that a cell is applying or will be transitioning to an energysaving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and based on the determination, reacquire system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

2. The user equipment of claim 1, wherein the user equipment is caused to reacquire the system information of the cell before the expiration of the validity timer.

3. The user equipment of any preceding claim, further being caused to: reset the validity timer based on reacquiring the system information.

4. The user equipment of any preceding claim, further being caused to: receive, from an access node controlling the cell, an indication indicating that the cell will be transitioning to the energy-saving mode, wherein the determination is based on the indication.

5. The user equipment of claim 4, wherein the indication indicates a time when the cell will be transitioning to the energy-saving mode, wherein the user equipment is caused to initiate the reacquisition of the system information before the time when the cell will be transitioning to the energy-saving mode.

6. The user equipment of any of claims 4 to 5, wherein the indication indicates a time threshold within which the system information is to be reacquired, the time threshold being relative to the expiration of the validity timer, wherein the user equipment is caused to reacquire the system information based on determining that a remaining time to the expiration of the validity timer is less than the time threshold, the remaining time being higher than zero.

7. The user equipment of any of claims 1 to 3, further being caused to: detect an on-demand system information block transmission of the cell, wherein the on-demand system information block transmission indicates that the cell is applying the energy-saving mode, wherein the determination is based on the detection.

8. The user equipment of any of claims 1 to 3, wherein the determination is based on historical data of the cell, the historical data indicating a pattern of the cell potentially transitioning to the energy-saving mode.

9. The user equipment of any preceding claim, wherein the cell comprises a serving cell of the user equipment, or a neighbor cell of the serving cell.

10. An access node comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the access node at least to: determine, based on a predetermined condition being met, to transition a cell controlled by the access node to an energy-saving mode, wherein the energysaving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and, based on determining to transition the cell to the energy-saving mode, transmit, to one or more user equipments, an indication indicating that the cell is applying or will be transitioning to the energy-saving mode, wherein the indication indicates the one or more user equipments to reacquire system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

11. The access node of claim 10, wherein the indication indicates a time when the cell will be transitioning to the energy-saving mode.

12. The access node of any of claims 10 to 11, wherein the indication indicates a time threshold within which the system information is to be reacquired, the time threshold being relative to the expiration of the validity timer.

13. The access node of any of claims 10 to 12, wherein the predetermined condition is related to a load of the cell.

14. A method performed by a user equipment, the method comprising: determining that a cell is applying or will be transitioning to an energysaving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and based on the determination, reacquiring system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

15. A method performed by an access node, the method comprising: determining, based on a predetermined condition being met, to transition a cell controlled by the access node to an energy-saving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and, based on determining to transition the cell to the energy-saving mode, transmitting, to one or more user equipments, an indication indicating that the cell is applying or will be transitioning to the energy-saving mode, wherein the indication indicates the one or more user equipments to reacquire system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

16. A non-transitory computer readable medium comprising program instructions which, when executed by a user equipment, cause the user equipment to perform at least the following: determining that a cell is applying or will be transitioning to an energysaving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and based on the determination, reacquiring system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.

17. A non-transitory computer readable medium comprising program instructions which, when executed by an access node, cause the access node to perform at least the following: determining, based on a predetermined condition being met, to transition a cell controlled by the access node to an energy-saving mode, wherein the energy-saving mode comprises that a transmission of one or more system information blocks of the cell is stopped, or that a transmission periodicity of the one or more system information blocks of the cell is increased; and, based on determining to transition the cell to the energy-saving mode, transmitting, to one or more user equipments, an indication indicating that the cell is applying or will be transitioning to the energy-saving mode, wherein the indication indicates the one or more user equipments to reacquire system information of the cell before the transmission of the one or more system information blocks is stopped or before the transmission periodicity is increased, regardless of whether a validity timer of previously acquired system information of the cell has expired.