Multicast and broadcast services in cellular communication networks

Abstract

According to one example aspect of the present disclosure, there is provided a method comprising: receiving, by an apparatus, a message while the apparatus is in a radio resource control inactive state, wherein the message comprises: a first indication indicating that the apparatus has joined in a multicast broadcast service session, and a second indication indicating that the apparatus remains in a radio resource control inactive state, and in response to receiving the message: initiating recovery of the radio resource control connection if it is determined that the apparatus belongs to a subset of user equipments based at least on information received in the radio resource control message, and maintaining in a radio resource control inactive state if it is not determined that the apparatus belongs to the subset.

Description

Technical Field

[0001] Various example embodiments relate generally to cellular communication systems, and more particularly to multicast and broadcast services in such networks. Background Art

[0002] A multicast transmission refers to a transmission from one transmitting wireless device (such as a radio network node) to some other wireless devices (such as a user equipment UE). However, a multicast transmission is not sent to all devices within the coverage area of ​​the transmitting wireless device. On the other hand, a broadcast transmission refers to a transmission from one transmitting wireless device to all devices within the coverage area of ​​the transmitting wireless device.

[0003] Multicast and broadcast services (MBS) can be provided in various cellular communication networks, such as in cellular communication networks operating according to 5G radio access technology. 5G radio access technology may also be referred to as new radio NR access technology. The third generation partnership project 3GPP has developed 5G / NR standards, and some topics in 3GPP discussions are related to MBS. According to the discussion, it is necessary to provide improved methods, devices, and computer programs related to the use of MBS. These improvements can also be utilized in other cellular communication networks. Summary of the invention

[0004] According to some aspects, the subject matter of the independent claims is provided. Some example embodiments are defined in the dependent claims.

[0005] The independent claims define the scope of protection of various exemplary embodiments of the present invention. Exemplary embodiments and features described in this specification that do not belong to the scope of the independent claims, if any, are to be construed as examples that help understand the various exemplary embodiments of the present invention.

[0006] According to a first aspect of the present invention, there is provided an apparatus comprising at least one processing core, at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, together with the at least one processing core, enable the apparatus to at least: receive a message when the apparatus is in a radio resource control inactive state, wherein the message comprises: a first indication indicating a multicast broadcast service session that the apparatus has joined, and a second indication indicating to remain in the radio resource control inactive state; and in response to receiving the message: initiating recovery of a radio resource control connection if it is determined that the apparatus belongs to a user equipment subset based at least on information received in the radio resource control message, and remaining in the radio resource control inactive state if it is not determined that the apparatus belongs to the subset. The apparatus of the first aspect may be a user equipment or a control device configured to control its functions (possibly when installed therein).

[0007] Example embodiments of the first aspect may include at least one feature from the following bulleted list or any combination of the following features:

[0008] wherein the user device subset includes privileged user devices;

[0009] wherein the at least one memory and the computer program code are further configured to, together with the at least one processing core, cause the apparatus to at least: receive a radio resource control message, wherein the radio resource control message includes: an indication that the apparatus belongs to a user device;

[0010] Configuration of backup subsets;

[0011] wherein the at least one memory and the computer program code are further configured to, together with the at least one processing core, cause the apparatus to at least: receive a paging message during a paging occasion; and when the paging occasion is a paging occasion for a subset of user equipment, determine

[0012] Determine that the device belongs to the subset;

[0013] wherein the at least one memory and the computer program code are further configured to, together with the at least one processing core, cause the apparatus to at least:

[0014] When identifying a user device, determining that the device belongs to the subset;

[0015] wherein the message further comprises: an indication indicating whether the user equipment belonging to the subset is to initiate said restoration of the radio resource control connection in response to reception of the message;

[0016] wherein the at least one memory and the computer program code are further configured to, with the at least one processing core, cause the apparatus to at least: determine that the apparatus is to initiate said restoration of the radio resource control connection based on a parameter representing a percentage or fraction of user equipment in the subset that is to initiate said restoration of the radio resource control connection;

[0017] wherein the at least one memory and the computer program code are further configured to, together with the at least one processing core, cause the apparatus to at least:

[0018] Receive the parameter in the message;

[0019] wherein the at least one memory and the computer program code are further configured to, together with the at least one processing core, cause the apparatus to at least: upon determining that the apparatus belongs to a user

[0020] In the case of a user equipment subset, the second indication is ignored;

[0021] wherein the at least one memory and the computer program code are further configured to, together with the at least one processing core, cause the apparatus to at least: start a timer when the apparatus is moved to a radio resource control inactive state; and when the timer runs

[0022] When the device is determined to belong to the user equipment subset;

[0023] The radio resource control message is a radio resource control release message, ...

[0024] a power resource control reconfiguration message, or a radio resource control establishment message;

[0025] Wherein the apparatus is a user equipment, or a control device configured to control a function of a user equipment.

[0026] According to a second aspect of the present invention, there is provided an apparatus comprising at least one processing core, at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, together with the at least one processing core, enable the apparatus to at least: send a message to at least one user equipment when the at least one user equipment is in a radio resource control inactive state, wherein the message comprises: a first indication indicating a multicast broadcast service session that the at least one user equipment has joined, and a second indication indicating to remain in the radio resource control inactive state; and send an indication indicating a subset of user equipment to a neighboring radio network node, wherein the user equipment in the subset is to initiate recovery of a radio resource control connection in response to receiving the message. The apparatus of the second aspect may be a radio network node or a control device configured to control its functions (possibly when installed therein).

[0027] Example embodiments of the second aspect may include the following features:

[0028] • wherein the indication is sent to the neighboring wireless network when at least one user equipment is released to a radio resource control inactive state, or when radio access network paging is performed.

[0029] According to a third aspect of the present invention, a first method is provided, the first method comprising: receiving a message by a device when the device is in a radio resource control inactive state, wherein the message comprises: a first indication indicating a multicast broadcast service session that the device has joined, and a second indication indicating to remain in the radio resource control inactive state; and in response to receiving the message: initiating recovery of the radio resource control connection when the device determines that the device belongs to a user equipment subset based at least on information received in the radio resource control message, and remaining in the radio resource control inactive state when the device does not determine that the device belongs to the subset. The first method may be performed by a user equipment, or a control device configured to control its functions (possibly when installed therein).

[0030] According to a fourth aspect of the present invention, a second method is provided, the second method comprising: sending a message to at least one user equipment by a device when the at least one user equipment is in a radio resource control inactive state, wherein the message comprises: a first indication indicating a multicast broadcast service session that the at least one user equipment has joined, and a second indication indicating to remain in the radio resource control inactive state; and sending an indication indicating a subset of user equipment to a neighboring radio network node by the device, wherein the user equipment in the subset is to initiate recovery of the radio resource control connection in response to receiving the message. The second method may be performed by a radio network node or a control device configured to control its functions (possibly when installed therein).

[0031] According to a fifth aspect of the present invention, there is provided an apparatus comprising: a component for receiving a message when the apparatus is in a radio resource control inactive state, wherein the message comprises: a first indication indicating a multicast broadcast service session that the apparatus has joined, and a second indication indicating to remain in the radio resource control inactive state; and in response to receiving the message: a component for initiating recovery of a radio resource control connection when it is determined that the apparatus belongs to a user equipment subset based at least on information received in the radio resource control message, and a component for remaining in the radio resource control inactive state when it is not determined that the apparatus belongs to the subset. The apparatus of the fifth aspect may be a user equipment, or a control device configured to control its functions (possibly when installed therein).

[0032] According to a sixth aspect of the present invention, there is provided an apparatus, comprising: a component for sending a message to at least one user equipment when the at least one user equipment is in a radio resource control inactive state, wherein the message comprises: a first indication indicating a multicast broadcast service session that the at least one user equipment has joined, and a second indication indicating to remain in the radio resource control inactive state; and a component for sending an indication indicating a subset of user equipment to an adjacent radio network node, wherein the user equipment in the subset is to initiate recovery of the radio resource control connection in response to receiving the message. The apparatus of the sixth aspect may be a user equipment, or a control device configured to control its functions (possibly when installed therein).

[0033] According to a seventh aspect of the present invention, there is provided a non-transitory computer-readable medium having a computer-readable instruction set stored thereon, which, when executed by at least one processor, causes a device to at least perform a first method or a second method. According to an eighth aspect of the present invention, there is provided a computer program, which includes instructions, and when the program is executed by a device, the instructions cause the device to perform the first method or the second method. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 illustrates examples of network scenarios according to at least some example embodiments;

[0035] Figure 2 illustrates a first signaling diagram according to at least some example embodiments;

[0036] Figure 3 illustrates a second signaling diagram according to at least some example embodiments;

[0037] Figure 4 illustrates a third signaling diagram according to at least some example embodiments;

[0038] Figure 5 illustrates a fourth signaling diagram according to at least some example embodiments;

[0039] Figure 6 illustrates example apparatus capable of supporting at least some example embodiments;

[0040] Figure 7 A flow chart of a first method according to at least some example embodiments is illustrated. DETAILED DESCRIPTION

[0041] Figure 1 Examples of network scenarios are illustrated in accordance with at least some example embodiments. Figure 1In an example scenario, there may be a beam-based wireless communication system including a UE 110, a radio network node 120, and a core network element 130. The UE 110 may connect to the radio network node 120 via an air interface using beams 112 or 114 simultaneously or one at a time.

[0042] For example, UE 110 may include a smartphone, a cellular phone, a machine-to-machine (M2M) node, a machine-type communication (MTC) node, an Internet of Things (IoT) node, an automobile telemetry unit, a laptop, a tablet computer, or virtually any type of suitable wireless terminal. Figure 1 In the example system of , UE 110 may wirelessly communicate with radio network node 120, for example, via beam 112 and / or beam 114. Radio network node 120 may be considered a serving node for UE 110, and one cell of radio network node 120 may be a serving cell for UE 110.

[0043] The air interface between the UE 110 and the radio network node 120 may be configured according to a radio access technology RAT, both of which are configured to support the RAT. Examples of cellular RATs include Long Term Evolution LTE, New Radio NR (also known as fifth generation 5G radio access technology), and MulteFire.

[0044] For example, in the context of LTE, the radio network node 120 may be referred to as an eNB, while in the context of NR, the radio network node 120 may be referred to as a gNB. In some example embodiments, the radio network node 120 may be referred to as a transmission reception point (TRP), or may control multiple TRPs, which may be collocated or non-collocated. In any case, the example embodiments of the present disclosure are not limited to any particular wireless technology. Rather, the example embodiments may be utilized in any wireless communication system in which a multicast and broadcast service MBS or some other similar feature is used.

[0045] The radio network node 120 may be connected to the core network 130 via an interface 125 directly or via at least one intermediate node. The core network 130 may also be connected to another network ( Figure 1 The radio network node 120 may be coupled to the core network 130 or another core network directly or via at least one intermediate node, through which connection to other networks may be obtained, for example, via a global interconnected network.

[0046] Paging may be used to allow a network (e.g., a radio network node 120) to reach UEs (such as UE 110) in RRC_IDLE and RRC_INACTIVE states via paging messages. Alternatively or additionally, paging may be used to notify UEs in RRC_IDLE, RRC_INACTIVE, and RRC_CONNECTED states of changes in system information. In some example embodiments, the paging message may be addressed with a paging radio network temporary identifier P-RNTI on a physical downlink control channel PDCCH sent on a paging control channel PCCH. Although RRC_IDLE, RRC_INACTIVE, and RRC_CONNECTED states are used as examples in the present disclosure, these states may generally refer to any similar radio resource control idle state, radio resource control inactive state, and radio resource connected state, respectively.

[0047] For example, when the UE 110 is in the RRC_IDLE state, the UE 110 may monitor a paging channel for paging initiated by the core network CN. The CN initiated paging may include an identity of the UE 110 in the paging message. In the RRC_INACTIVE state, the UE 110 may monitor a paging channel for paging initiated by the radio access network RAN. The RAN initiated paging may include an inactive radio network temporary identifier I-RNTI. The I-RNTI may be configured by a RAN node (such as the radio network node 120) that sends the UE 110 to the RRC_INACTIVE state.

[0048] In some example embodiments of the present disclosure, UE 110 may monitor the paging occasions specified in 3GPP TS 38.304 to receive a paging message. Upon reception of the paging message, UE 110 in the RRC_IDLE state may initiate an RRC connection. Upon reception of a paging message in the RRC_INACTIVE state, if the identity of UE 110 (such as a 5G service temporary mobile subscriber identity 5G-S-TMSI ID) is not indicated in the paging message, UE 110 may initiate recovery of the RRC connection. In the event that the 5G-S-TMSI ID of UE 110 is indicated in a paging message received by UE 110 in the RRC_INACTIVE state, UE 110 may move to the RRC_IDLE state.

[0049] With respect to MBS, point-to-multipoint (PTM) transmission may be used to supply MBS services to multiple users, for example, by using the same radio framework as used for unicast transmission. An important issue associated with the use of MBS in 3GPP networks is to enable UEs in RRC_INACTIVE state to receive multicast services for the purposes of scalability and energy saving. Support and enhancements related to end-to-end MBS service delivery for a large number of UEs should be enabled, for example, by enabling the reception of MBS session data in the RRC inactive state. In addition, support for multicast reception by UEs in the RRC_INACTIVE state should be specified, and PTM configuration should be performed for UEs receiving multicast in the RRC_INACTIVE state. For example, if UE 110 is in the RRC_INACTIVE state, it should be able to apply the configuration of the multicast service in the cell to start / continue receiving the multicast service that the UE has joined.

[0050] If no data is to be sent to UE 110 for an active multicast session, the radio network node 120 may move UE 110 to an RRC_INACTIVE state. When an MBS multicast session is deactivated, the radio network node 120 may move UE 110 to an RRC idle or RRC_INACTIVE state. When a multicast session has been activated by the core network 130 or the radio network node 120 has multicast session data to deliver, a radio network node supporting MBS may use a group notification mechanism to notify UEs in RRC_IDLE or RRC_INACTIVE states. After receiving the group notification, the UE reconnects to the network. The group notification may be addressed with a P-RNTI on the PDCCH. The paging message of the group notification may include an identifier of an MBS session for a specific multicast service, such as a TMGI. The identifier of the MBS session may be used to page all UEs in RRC_IDLE and RRC_INACTIVE states that are joined to the associated MBS multicast session. That is, the UE may not be paged individually. After the UE leaves the associated multicast session, the UE may stop monitoring the group notification associated with the specific multicast session.

[0051] If a UE in RRC idle state joining an MBS multicast session resides on a radio network node that does not support MBS, the UE may be notified about activation of the multicast session or data availability through CN initiated paging, where the core network 130 may page each UE individually. On the other hand, if a UE in RRC_INACTIVE state joining an MBS multicast session resides on a radio network node that does not support MBS, the UE may be notified about data availability individually through RAN initiated paging.

[0052] In some example embodiments, the radio network node 120 may decide whether to enable multicast reception for a UE in the RRC_INACTIVE state, and the core network 130 may provide assistance information to the radio network node 120 to assist in making this selection. The assistance information may include information about whether the UE 110 belongs to a subset of UEs, such as a "privileged" category of a multicast group. If the UE 110 belongs to the subset, i.e., is a privileged UE, the radio network node 120 should ideally not send the UE 110 to the RRC_INACTIVE state, because the UE 110 should be in the RRC_CONNECTED state when receiving multicast services. For example, compared to the RRC_INACTIVE state, the UE 110 in the RRC_CONNECTED state may experience better performance because it can provide hybrid automatic repeat request HARQ feedback and channel state information CSI measurements to the radio network node 120. The radio network node 120 may then adjust the multicast transmission parameters suitable for the needs of the UE 110 and, if necessary, perform some HARQ retransmissions.

[0053] One use case for privileged UEs may be public safety. For example, an application function may provide information (e.g., privileged status, priority) about specific public safety participants in a group call. Such information may be used to identify which UEs should remain in the RRC_CONNECTED state and which UEs may be candidates for transitioning to the RRC_INACTIVE or RRC_IDLE states. These privileged UEs may be, for example, "frequent talkers" who need to remain in the RRC_CONNECTED state, or simply premium subscribers or high priority UEs.

[0054] When the multicast service is deactivated, for example by the radio network node 120, the UEs in the multicast group may be pushed to the RRC_INACTIVE state. To activate the session and move the UE back to RRC_CONNECTED, a group paging mechanism may be used, where the paging message may include a temporary mobile group identity TMGI for the multicast service.

[0055] Alternatively, the radio network node 120 may decide to keep the UE in the RRC_INACTIVE state while activating the session, and the UE may receive the multicast service while in the RRC_INACTIVE state. In this case, the radio network node 120 may perform group paging using an indication, such as a flag, that the UE in the RRC_INACTIVE state remains in the RRC_INACTIVE state but only receives notification about the session activation. Thus, even a privileged UE remains in the RRC_INACTIVE state to receive multicast transmissions and does not initiate an RRC connection to a cell of the radio network node 120, although ideally, a privileged UE should always be in the RRC_CONNECTED state.

[0056] Thus, example embodiments of the present disclosure enable UE 110 belonging to the subset (eg, privileged UEs) to trigger an RRC connection even though UE 110 will be paged via group paging including an indication that the UE remains in RRC_INACTIVE state to receive multicast services.

[0057] The paging message may include a list of identities of a subset of UEs, such as identities of privileged UEs. The paging message may be a radio paging message. The subset may include UE 110, and the radio network node 120 may send the paging message upon activation of a multicast session. UE 110 may therefore receive the paging message when it is in the RRC_INACTIVE state. The paging message may include: a first indication indicating an MBS session that UE 110 has joined, and a second indication indicating to remain in the RRC_INACTIVE state. In some example embodiments, the first indication may be the TMGI of the session, and / or the second indication may be a flag for a non-privileged UE to remain in the RRC_INACTIVE state.

[0058] Typically, the first indication and the second indication may be sent in an RRC message. The RRC message may be an RRC release message, an RRC reconfiguration message, or an RRC setup message. Using an RRC message (e.g., instead of a NAS message) to indicate UE behavior may be beneficial because the radio network node 120 may have more dynamic control over it, and additional information (such as a validity timer) may be easily added. The RRC message also enables UE-specific indications.

[0059] When paging, if the radio network node 120 decides to use RRC_INACTIVE mode multicast reception for UEs not in the subset (i.e., other UEs except the privileged UEs), the radio network node 120 may include a TMGI and a flag for the UEs not in the subset. The flag may indicate that the UEs not in the subset will remain in the RRC_INACTIVE state and start receiving the multicast service corresponding to the TMGI.

[0060] In addition, if UE 110 determines that it belongs to the subset based on the information received in the RRC release message, UE 110 can initiate the recovery of the RRC connection in response to receiving the paging message. The information received in the RRC release message may include, for example, a list of identities of a subset of UEs, such as the identities of privileged UEs. UE 110 can then determine that it belongs to the subset when its identity is in the list, and initiate the recovery of the RRC connection. However, if UE 110 determines that it does not belong to the subset, for example, when its identity is not in the list, UE 110 can remain in the RRC_INACTIVE state. The entries in the identity list of the UEs belonging to the subset can be 5G-S-TMSI, I-RNTI, or any other unique identity similarly interpreted by UE 110 and radio network node 120.

[0061] In some example embodiments, a paging message may be sent in all paging occasions for all UEs, including paging occasions for UEs in the subset (such as privileged UEs). Alternatively, the radio network node 120 may calculate a paging occasion corresponding to a subset of UEs and send one or more additional paging messages to the UEs in the subset to move the UEs in the subset to the RRC_CONNECTED state. In this case, the paging message sent to the UEs in the subset may not include a TMGI, but may include one or more identifiers of the UEs belonging to the subset. In addition, since the UEs belonging to the subset are paged individually, the transmission of a paging message including an indication of a UE that does not belong to the subset and will remain in the RRC_INACTIVE state does not need to take into account the paging occasions of the UEs belonging to the subset.

[0062] In some example embodiments, if a particular paging occasion for an MBS multicast service is for UEs in the subset, but not for other UEs, the radio network node 120 may perform paging in this case by sending a first indication indicating an MBS session without sending a second indication indicating to remain in the RRC_INACTIVE state. For example, if the paging occasion includes only privileged UEs (identified by TMGI) for a given MBS multicast service, the network may perform paging at these occasions using the TMGI without using a flag indicating to remain in RRC_INACTIVE. On the other hand, if another paging occasion for the MBS multicast service is for UEs not in the subset, but not for UEs in the subset, the radio network node 120 may perform paging at these paging occasions by sending the first indication and the second indication. For example, if the paging occasion includes non-privileged UEs, but not privileged UEs, the network may perform paging at these paging occasions using the TMGI and a flag indicating to remain in RRC_INACTIVE. In this case, accordingly, in paging occasions for both UEs in the subset and UEs not in the subset (such as privileged UEs and non-privileged UEs), both paging using TMGI together with a flag and paging using I-RNTI may be required.

[0063] In some example embodiments, UE 110 may be allowed to learn that it belongs to the subset, e.g., is a privileged UE. For example, if UE 110 receives both a group page using a TMGI and a RAN page using an I-RNTI at the same paging occasion or within a given time, the UE may know that it belongs to the subset. After learning that it belongs to the subset, UE 110 may later act accordingly, i.e., resume the RRC connection, even when receiving a group page with an indication (such as a flag) indicating that it remains in the RRC_INACTIVE state. That is, UE 110 may receive both a group page and a dedicated page in the same time slot, and in this case, UE 110 may know that it belongs to the subset, e.g., is a privileged UE, and if any actions are defined, e.g., for connected privileged UEs, the UE may act accordingly in the future.

[0064] In some example embodiments, in case of RAN paging, the radio network node 120 (such as an anchor gNB that moves the UE from the RRC_CONNECTED state to the RRC_INACTIVE state) may send a list of UEs in the subset that join the multicast service (such as privileged UEs) to other BSs in the RAN-based notification area RNA in a RAN paging message. In case of a decomposed gNB, the list of UEs in the subset may also be sent from the gNB central unit CU to the gNB distributed unit DU in an F1 paging message.

[0065] In some example embodiments, the UE in the subset may be configured with information that it is indeed in the subset. For example, a privileged UE may be configured with information that it is indeed a privileged UE, or at least configured with information that it can reconnect after receiving a paging with an indication that a UE not in the subset (such as a non-privileged UE) remains in the RRC_INACTIVE state. That is, the UE in the subset may be configured to ignore the indication indicating to remain in the RRC_INACTIVE state. The configuration may be for each UE and / or multicast service.

[0066] When the radio network node 120 moves the UE 110 from the RRC_CONNECTED state to the RRC_INACTIVE state, the radio network node 120 may indicate in the RRC reconfiguration (sent in the RRCRelease message) that the UE 110 belongs to the subset. Alternatively, the radio network node 120 may include in the RRC reconfiguration information information that the UE 110 is configured to ignore the indication indicating to remain in the RRC_INACTIVE state after receiving the paging. Thus, the UE 110 may determine that it belongs to the subset based on the information received in the RRCRelease message, and initiate the recovery of the RRC connection.

[0067] If the UE 110 has received the information when the paging message with the indication that the UE should remain in the RRC_INACTIVE state and the TMGI of the service to which the UE 110 has joined, one option is that the UE 110 receiving the configuration about being in the subset (such as the "privileged" configuration) can directly initiate RRC recovery. Another option is that in addition to the TMGI and the indication that the RRC_INACTIVE UE remains in RRC_INACTIVE, there is also third information in the paging message. The third information enables the radio network node 120 to specifically control whether the UEs in the subset (such as privileged UEs) should reconnect. If the UE 110 belonging to the subset receives the third information, it may not initiate the recovery of the RRC connection. Otherwise, the UE 110 in the subset may initiate the recovery of the RRC connection. UEs that do not belong to the subset (e.g., UEs without such privileges) can remain in the RRC_INACTIVE state in both cases. The use of the third information can be used to introduce more network control behavior, while the direct recovery of the RRC connection does not introduce new bits in the paging message.

[0068] In some example embodiments, the configuration that a UE belongs to the subset (e.g., the UE has "privileges") may be temporary. For example, after a period of time, a new "frequent talker" may appear in the multicast session, or the configuration of the UE belonging to the subset may be updated / deleted for some other reason. Like the radio network node 120, the network may not want to have the UE belong to the subset for an indefinite period of time.

[0069] Therefore, the RRC reconfiguration that moves UE 110 to the RRC_INACTIVE state may also include information about how long UE 110 may consider itself to belong to the subset. After UE 110 enters the RRC_INACTIVE state, a timer may be started, and after the timer expires, UE 110 may behave as if it no longer belongs to the subset. That is, UE 110 may start a timer when it is moved to the RRC_INACTIVE state, and determine that it belongs to the user equipment subset while the timer is running.

[0070] In some example embodiments, if UE 110 is in RRC_INACTIVE state, it may receive configuration of a multicast service in a camped cell to start / continue receiving the multicast service that UE 110 has joined. When a UE in RRC_INACTIVE state performs cell reselection, it may miss paging performed at the cell. In addition, if such paging is performed periodically by radio network node 120, UE 110 may need to wait for the next opportunity, which may introduce delays. To overcome this problem, the cell may broadcast some information about the status of the current session, for example, whether the UE can receive services in RRC_CONNECTED or RRC_INACTIVE state, whether the multicast session is active, etc.

[0071] In some example embodiments, the cell may indicate in the system information block SIB or multicast control channel MCCH message whether the UEs in the subset can reconnect for a specific TMGI. For example, the SIB / MCCH information may indicate that the UEs in the RRC_INACTIVE state that do not belong to the subset will remain in the RRC_INACTIVE state. In some example embodiments, both paging enhancement and SIB / MCCH enhancement may coexist, where paging may be used to activate MBS sessions faster and SIB / MCCH may be used for new UEs in the cell.

[0072] In some example embodiments, the cell may also indicate, for example, via SIB / MCCH, a parameter x representing a percentage of UEs in the subset that may reconnect after receiving a paging message with an indication that UEs not belonging to the subset remain in the RRC_INACTIVE state. For example, all UEs in the cell belonging to the subset may generate a random number between 1 and 100, and if the random number is less than x for UE 110, UE 110 may reconnect but otherwise remain in the RRC_INACTIVE state. Thus, UE 110 may determine to initiate resumption of the RRC connection based on a parameter representing the percentage of UEs in the subset that are to initiate said resumption of the RRC connection.

[0073] In some example embodiments, the configuration of the UE regarding belonging to the subset (regarding the handling of an indication indicating that a UE not belonging to the subset remains in an inactive state) may be received via the non-access stratum NAS. The configuration may be in a NAS registration accept message or in a NAS protocol data unit PDU session establishment / modification command. In addition, the update of the configuration from belonging to the subset to not belonging to the subset (or vice versa) may be sent via NAS in a UE configuration update message or a PDU session modification command message. For example, the update of the configuration from privileged / non-privileged to non-privileged / privileged may be sent via NAS in a UE configuration update message or a PDU session modification command message. The configuration information may be received by the UE 110 upon joining.

[0074] Figure 2 A first signaling diagram according to at least some example embodiments is illustrated. Figure 1 UE 110, radio network node 120, and core network 130. Furthermore, another radio network node 122 is shown.

[0075] At step 202, UE 110 may be in RRC_CONNECTED state in a first cell (such as cell 1 of gNB1) of radio network node 120. At step 204, UE 110 may join a multicast session identified by TMGI#1, and radio network node 120 may be configured with information that the UE belongs to the subset (e.g., is a privileged UE indicated by 5GC). The multicast session may be in a deactivated (i.e., inactive state) where no data is to be sent.

[0076] At step 206, the core network 130 (e.g., 5GC) may activate the multicast session. At step 208, the radio network node 120 may configure the multicast radio bearer MRB and other required configurations with RRC signaling for the UE 110 to receive the multicast session. At step 210, the UE 110 may receive the multicast session from the first cell of the radio network node 120.

[0077] In step 212, in a first case, the multicast session may be deactivated by the core network 130. In step 214, in a second case, the radio network node 120 may decide to move the UE 110 to the RRC_INACTIVE state because there is no data for the multicast session, i.e., no data for TMGI#1. In step 216, the radio network node 120 may send an RRC release command, which may include an indication that RNA=cell 1+cell 2. In step 218, the UE 110 may move to the RRC_INACTIVE state and camp on the first cell. In step 220, the UE 110 may continue to be in the RRC_INACTIVE state and reselect a second cell (cell 2 of gNB2) of another radio network node 122 for camping based on channel conditions.

[0078] At step 222, in a first case, a multicast session may be activated by the core network 130. At step 224, in a second case, data of the multicast session (TMGI#1) may arrive at the radio network node 120 from the core network 130. At step 226, the radio network node 120 may page during paging occasions of all UEs, including paging occasions of UEs in the subset (e.g., privileged UEs).

[0079] At step 228, the radio network node 120 may send a paging message including: a first indication indicating the MBS session that the UE 110 has joined, and a second indication indicating to remain in the RRC_INACTIVE state. For example, the paging message may include TMGI#1 and a flag for the "non-privileged" UE to remain in RRC_INACTIVE. The paging message may also include a list of UEs belonging to the subset, such as a list of privileged UE identities. When the UE 110 is camped under another radio network node 122, the radio network node 120 may not be able to obtain a response from the UE 110.

[0080] At step 230, the radio network node 120 may send a RAN paging message including a list of UEs belonging to the subset, having joined the session and whose RNA includes the second cell to another radio network node 122. At step 232, the other radio network node 122 may page during paging occasions of all UEs, including the paging occasions of the UEs in the subset.

[0081] At step 232, another radio network node 120 may send a paging message including: a first indication indicating an MBS session that UE 110 has joined, and a second indication indicating to remain in the RRC_INACTIVE state. For example, the paging message may include TMGI#1 and a flag for a "non-privileged" UE to remain in RRC_INACTIVE. The paging message may also include a list of UEs belonging to the subset, such as a list of privileged UE identities.

[0082] UE 110 may compare the identities in the list of UEs in the subset with its own identity at step 236. If UE 110's own identity is in the list, the UE may determine that it belongs to the subset and initiate resumption of the RRC connection at step 238. If UE 110's identity is not in the list, UE 110 may determine that it does not belong to the subset and remain in the RRC_INACTIVE state.

[0083] Figure 3 A second signaling diagram according to at least some example embodiments is illustrated. Figure 1 UE 110, radio network node 120 and core network 130. Furthermore, another radio network node 122 is shown. Figure 3 The steps 302-324 shown may correspond to Figure 2 Steps 202-224 are shown.

[0084] At step 326, the radio network node 120 may send a paging message including: a first indication indicating the MBS session that the UE 110 has joined, and a second indication indicating to remain in the RRC_INACTIVE state. For example, the paging message may include TMGI#1 and a flag for the "non-privileged" UE to remain in RRC_INACTIVE. The paging message may also include a list of UEs belonging to the subset, such as a list of privileged UE IDs. When the UE 110 is camped under another radio network node 122, the radio network node 120 may not be able to obtain a response from the UE 110.

[0085] Taking into account the paging occasions of the UEs belonging to the subset, it may not be necessary to send a transmission of a paging message including a second indication indicating that the UEs not belonging to the subset remain in the RRC_INACTIVE state, because these UEs can be paged separately. In step 328, the radio network node 120 may send a message including the first indication but not the second indication, for example, if the given paging occasion is for privileged UEs of a given MBS multicast service, but not for non-privileged UEs. For example, the radio network node 120 may use the TMGI for paging without a flag indicating to remain in RRC_INACTIVE. If the given paging occasion includes non-privileged UEs, but not privileged UEs, the radio network node 120 may use the TMGI and the flag indicating to remain in RRC_INACTIVE for paging in these paging occasions. In some example embodiments, at paging occasions for both privileged UEs and non-privileged UEs, both paging using the TMGI with the flag and paging using the I-RNTI may be required.

[0086] When the UE 110 is camped under another radio network node 122 , the radio network node 120 may not be able to obtain a response from the UE 110 . Figure 3 The steps 330-338 shown may correspond to Figure 2 Steps 230-238 are shown.

[0087] Figure 4 A third signaling diagram according to at least some example embodiments is illustrated. Figure 1 UE 110, radio network node 120, and core network 130. Furthermore, another radio network node 122 is shown. Figure 2 The steps 402-424 shown in FIG. 4 may correspond to Figure 2 Steps 202-224 are shown. In addition, at step 404, the UE 110 may be configured by the radio network node 120 with information that the UE 110 belongs to the subset, such as information that the UE 110 is a privileged UE.

[0088] The information may relate to handling of an indication that the UE remains in the RRC_INACTIVE state. The information may be received via NAS, for example, a NAS Registration Accept message or a NAS PDU Session Establishment / Modification command. In addition, the update of the configuration from belonging to the subset to not belonging to the subset (or vice versa) may be sent via NAS in a UE Configuration Update message or a PDU Session Modification Command message. For example, the update of the configuration from privileged / non-privileged to non-privileged / privileged may be sent via NAS in a UE Configuration Update message or a PDU Session Modification Command message. The configuration information may be received by the UE 110 upon joining.

[0089] At step 416, UE 110 may also receive an RRC release message from radio network node 120. The RRC release message may include information indicating that UE 110 belongs to the subset (e.g., is a privileged UE). In some example embodiments, another RRC message (such as an RRC reconfiguration message or an RRC setup message) may be used to configure the "privileged" information and possible timers for UE 110. Alternatively, the RRC release message may include a configuration such that, after receiving a paging with a second indication that the UE remains in RRC_INACTIVE, UE 110 may ignore the second indication and resume the RRC connection. In some example embodiments, the RRC release message may also include information about how long UE 110 may consider itself to be in the subset (e.g., as a privileged UE). In this case, at step 418, when UE 110 moves to the RRC_INACTIVE state, UE 110 may start a timer.

[0090] Figure 4 Steps 426-430 shown may correspond to Figure 3 However, the radio network node 120 may also send an indication at step 428 to instruct the UEs belonging to the subset to resume the RRC connection.

[0091] In some example embodiments, at step 432, another radio network node 120 may send a paging message including: a first indication indicating an MBS session that UE 110 has joined, and a second indication indicating to remain in the RRC_INACTIVE state. At step 434, UE 110 may check whether the timer has expired. If not, UE 110 may resume the RRC connection.

[0092] In some example embodiments, at step 436, another radio network node 120 may send a paging message including: a first indication indicating the MBS session that UE 110 has joined, and a second indication indicating to remain in the RRC_INACTIVE state. The paging message may also include an indication indicating that the UEs in the subset need to resume the RRC connection. At step 438, UE 110 may check whether the timer has expired. If not, UE 110 may resume the RRC connection. Figure 4 Step 440 shown may correspond to Figure 3 Step 338 is shown.

[0093] Figure 5 A fourth signaling diagram according to at least some example embodiments is illustrated. Figure 1UE 110, radio network node 120, and core network 130. Furthermore, another radio network node 122 is shown. Figure 5 Steps 502-518 shown may correspond to Figure 2 Steps 202-218 are shown. In addition, Figure 5 Step 516 shown may correspond to Figure 4 Step 416 is shown.

[0094] At step 520, the radio network node 120 may broadcast a message. The message may be broadcast in the SIB / MCCH and include an indication that the MBS session (e.g., TMGI#1) is in a deactivated state. At step 522, the UE 110 may monitor a broadcast channel and the radio network node 120 may broadcast that the MBS session is in a deactivated state. The UE 110 may, for example, monitor the SIB / MCCH. The UE 110 may monitor a broadcast channel for (multiple) MBS sessions and detect, for example, whether TMGI#1 is in a deactivated state. In this case, the UE 110 may not restore the RRC connection. At step 524, the UE 110 may continue to be in the RRC_INACTIVE state and reselect a second cell to camp on based on channel conditions.

[0095] At step 526, UE 110 may monitor a broadcast channel, and another radio network node 122 may broadcast that the MBS session is in a deactivated state. At step 528, UE 110 may detect that the MBS session is in a deactivated state, for example, TMGI#1 is in a deactivated state. In this case, UE 110 may not restore the RRC connection. At step 530, the MBS session may be activated. At step 532, another radio network node 122 may determine data for the MBS session. At step 534, another radio network node 122 may broadcast that the MBS session is in an active state. For example, another radio network node 122 may broadcast in SIB / MCCH that TMGI#1 is in an active state and a configuration received in an RRC_INACTIVE state. Alternatively, another radio network node 122 may broadcast an indication that UE 110 belonging to the subset (such as a privileged UE) needs to restore the RRC connection.

[0096] At step 536 , UE 110 may monitor a broadcast channel, such as SIB / MCCH, for the MBS session it has joined. UE 110 may determine that it belongs to the subset and initiate resumption of the RRC connection at step 538 .

[0097] Therefore, if the list of identities of UEs belonging to the subset is not disclosed, safer operation can be provided. In addition, at least some example embodiments can be implemented without changing the paging message, at least in the case of directly restoring the RRC connection. In addition, if new features are defined for a subset of UEs (such as privileged UEs) in the future, such UEs can be configured with this information. However, one advantage of the list is that changes from or to a subset, such as "privileged" to "normal / non-privileged", can be handled, particularly in the case where such changes occur frequently. In the case of frequent changes, the network can page UE110 to give the new configuration.

[0098] Figure 6 An example apparatus capable of supporting at least some example embodiments is illustrated. Illustrated is a device 600, which may include, for example, a UE 110 or a wireless network node 120, or a control device configured to control its functions (possibly when installed therein). A processor 610 is included in the device 600, which may include, for example, a single-core or multi-core processor, wherein a single-core processor includes one processing core and a multi-core processor includes more than one processing core. The processor 610 may generally include a control device. The processor 610 may include more than one processor. The processor 610 may be a control device. For example, the processing core may include a Cortex-A8 processing core manufactured by ARM Holdings or a Steamroller processing core produced by Advanced Micro Devices Corporation. The processor 610 may include at least one Qualcomm Snapdragon and / or Intel Atom processor. The processor 610 may include at least one application-specific integrated circuit ASIC. The processor 610 may include at least one field programmable gate array FPGA. The processor 610 may be a component for performing method steps in the device 600. The processor 610 may be configured at least in part by computer instructions to perform actions.

[0099] The processor may include, or be constructed as, a circuit system, which is configured to perform the various stages of the method according to the example embodiments described herein. As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) a pure hardware circuit implementation, such as an implementation in analog and / or digital circuitry only, and (b) a combination of hardware circuits and software, such as, where applicable: (i) a combination of (multiple) analog and / or digital hardware circuits with software / firmware, and (ii) any portion of (multiple) hardware processors with software (including (multiple) digital signal processors), software and (multiple) memories, which work together to enable a device such as a mobile phone or server to perform various functions), and (c) (multiple) hardware circuits and / or (multiple) processors, such as (multiple) microprocessors or portions of (multiple) microprocessors, which require software (e.g., firmware) to operate, but when software is not required for operation, the software may not be present.

[0100] This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or portions of a hardware circuit or processor and their accompanying software and / or firmware. For example, the term circuitry also covers a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device, if applicable to the particular claim element.

[0101] Device 600 may include memory 620. Memory 620 may include random access memory and / or permanent memory. Memory 620 may include at least one RAM chip. Memory 620 may include, for example, solid-state, magnetic, optical and / or holographic memory. Memory 620 may be at least partially accessible by processor 610. Memory 620 may be at least partially included in processor 610. Memory 620 may be a component for storing information. Memory 620 may include computer instructions that processor 610 is configured to execute. When computer instructions configured to cause processor 610 to perform certain actions are stored in memory 620, and device 600 as a whole is configured to run under the guidance of processor 610 using computer instructions from memory 620, processor 610 and / or at least one of its processing cores may be considered to be configured to perform the certain actions. Memory 620 may be at least partially included in processor 610. Memory 620 may be at least partially located outside device 600, but device 600 may access the memory.

[0102] The device 600 may include a transmitter 630. The device 600 may include a receiver 640. The transmitter 630 and the receiver 640 may be configured to transmit and receive information, respectively, according to at least one cellular or non-cellular standard. The transmitter 630 may include more than one transmitter. The receiver 640 may include more than one receiver. The transmitter 630 and / or the receiver 640 may be configured to operate according to, for example, a Global System for Mobile Communications GSM, Wideband Code Division Multiple Access WCDMA, Long Term Evolution, LTE, and / or 5G / NR standard.

[0103] The device 600 may include a near field communication NFC transceiver 650. The NFC transceiver 650 may support at least one NFC technology, such as Bluetooth, Wibree, or similar technology.

[0104] The device 600 may include a user interface UI 660. The UI 660 may include at least one of a display, a keyboard, a touch screen, a vibrator arranged to signal a user by vibrating the device 600, a speaker, and a microphone. The user may be able to operate the device 600 via the UI 660, such as accepting an incoming call, making a phone call or a video call, browsing the Internet, managing digital files stored in the memory 620 or on a cloud accessible via the transmitter 630 and the receiver 640 or via the NFC transceiver 650, and / or playing games.

[0105] The device 600 may include or be arranged to accept a user identification module 670. The user identification module 670 may include, for example, a subscriber identification module SIM card that may be installed in the device 600. The user identification module 670 may include information identifying a subscription of a user of the device 600. The user identification module 670 may include cryptographic information that may be used to verify the identity of the user of the device 600 and / or to facilitate encryption of communication information and billing of communications by the user of the device 600 via the device 600.

[0106] The processor 610 may be equipped with a transmitter that is arranged to output information from the processor 610 to other devices included in the device 600 via electrical conductors inside the device 600. Such a transmitter may include a serial bus transmitter that is arranged to output information to the memory 620 for storage therein, for example, via at least one electrical conductor. As an alternative to the serial bus, the transmitter may include a parallel bus transmitter. Similarly, the processor 610 may include a receiver that is arranged to receive information in the processor 610 from other devices included in the device 600 via electrical conductors inside the device 600. Such a receiver may include a serial bus receiver that is arranged to receive information from the receiver 640, for example, via at least one electrical conductor, for processing in the processor 610. As an alternative to the serial bus, the receiver may include a parallel bus receiver.

[0107] The device 600 may include Figure 6 Other devices not shown in the figure. For example, where the device 600 includes a smartphone, it may include at least one digital camera. Some devices 600 may include a rear camera and a front camera, wherein the rear camera may be used for digital photography and the front camera is used for video calls. The device 600 may include a fingerprint sensor that is arranged to at least partially authenticate a user of the device 600. In some example embodiments, the device 600 lacks at least one of the above devices. For example, some devices 600 may lack an NFC transceiver 650 and / or a user identification module 670.

[0108] The processor 610, the memory 620, the transmitter 630, the receiver 640, the NFC transceiver 650, the UI 660 and / or the user identification module 670 may be interconnected in a variety of different ways via electrical conductors inside the device 600. For example, each of the above devices may be individually connected to a main bus inside the device 600 to allow the devices to exchange information. However, those skilled in the art will appreciate that this is just an example, and that various ways of interconnecting at least two of the above devices may be selected according to example embodiments without departing from the scope of example embodiments.

[0109] Figure 7 1 is a flow chart of a first method according to at least some example embodiments. The apparatus of the first method may be UE 110 or a control device configured to control its functions (possibly when installed therein). That is, the steps of the first method may be performed by UE 110 or a control device configured to control its functions (possibly when installed therein).

[0110] The first method may include: at step 710, receiving a message by a device when the device is in a radio resource control inactive state, wherein the message includes: a first indication indicating a multicast broadcast service session that the device has joined, and a second indication indicating to remain in the radio resource control inactive state. The first method may also include: at step 720, in response to receiving the message: initiating recovery of the radio resource control connection if the device determines that the device belongs to a user equipment subset based on at least information received in the radio resource control message, and remaining in the radio resource control inactive state if the device does not determine that the device belongs to the subset.

[0111] It should be understood that the disclosed example embodiments are not limited to the specific structures, process steps or materials disclosed herein, but can be extended to equivalents that will be recognized by those skilled in the relevant art. It should also be understood that the terminology used herein is only used to describe specific example embodiments and is not intended to be limiting.

[0112] References throughout this specification to an exemplary embodiment or exemplary embodiments indicate that a particular feature, structure, or characteristic described in conjunction with the exemplary embodiment is included in at least one exemplary embodiment. Thus, the phrases "in an exemplary embodiment" or "in an exemplary embodiment" appearing in various places in this specification do not necessarily all refer to the same exemplary embodiment. When terms such as approximately or substantially are used to reference values, the exact value is also disclosed.

[0113] As used herein, for convenience, multiple items, structural elements, constituent elements and / or materials may be presented in a common list. However, these lists should be interpreted as each member in the list being individually identified as a separate and unique member. Therefore, any individual member in such a list should not be interpreted as the de facto equivalent of any other member in the same list simply based on its presentation in a common group (without an opposite indication). In addition, various example embodiments and examples and alternatives to its various components may be referenced herein. It should be understood that such example embodiments, examples and alternatives should not be interpreted as de facto equivalents to each other, but should be considered as separate and autonomous representations.

[0114] In an example embodiment, an apparatus such as UE 110 or radio network node 120 may include means for performing the above-described example embodiments and any combination thereof.

[0115] In an example embodiment, the computer program may be configured to produce a method according to the above example embodiments and any combination thereof. In an example embodiment, a computer program product embodied on a non-transitory computer readable medium may be configured to control a processor to perform a process including the above example embodiments and any combination thereof.

[0116] In an example embodiment, an apparatus such as UE 110 or radio network node 120 may include at least one processor and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the apparatus to perform at least the above-described example embodiments and any combination thereof.

[0117] In addition, the described features, structures or characteristics can be combined in any suitable manner in one or more example embodiments. In the foregoing description, many specific details are provided, such as examples of length, width, shape, etc., to provide a thorough understanding of the example embodiments of the present disclosure. However, those skilled in the relevant art will recognize that the present disclosure can be practiced without one or more specific details, or practiced using other methods, components, materials, etc. In other cases, in order to avoid blurring aspects of the present disclosure, known structures, materials, or operations are not shown or described in detail.

[0118] Although the above examples illustrate the principles of the exemplary embodiments in one or more specific applications, it will be apparent to those skilled in the art that many modifications may be made to the form, usage and details of implementation without departing from the principles and concepts of the present disclosure without exercising creative ability. Therefore, the present disclosure is limited only by the following claims.

[0119] In this document, the verbs "to comprise" and "to include" are used as open limitations, neither excluding nor requiring the presence of unrecited features. Unless explicitly stated otherwise, the features recited in the dependent claims may be freely combined with each other. Furthermore, it should be understood that the use of "a" or "an" (i.e., the singular) in this document does not exclude a plurality.

[0120] Industrial Applicability

[0121] At least some example embodiments find industrial application in cellular communication networks, such as 5G networks, and may also find application in other cellular communication networks in the future.

[0122] List of abbreviations

[0123] 3GPP: Third Generation Partnership Project

[0124] 5G-S-TMSI: 5G Service Temporary Mobile Subscriber Identity

[0125] BS: Base Station

[0126] CN: Core Network

[0127] CSI: Channel State Information

[0128] CU: Central Unit

[0129] DU: Distributed Unit

[0130] GSM: Global System for Mobile Communications

[0131] HARQ: Hybrid Automatic Repeat Request

[0132] IoT: Internet of Things

[0133] I-RNTI: Inactive Radio Network Temporary Identifier

[0134] LTE: Long Term Evolution

[0135] M2M: Machine to Machine

[0136] MBS: Multicast and Broadcast Service

[0137] MRB: Multicast Radio Bearer

[0138] MCCH: Multicast Control Channel

[0139] NAS: Non-Access Stratum

[0140] NFC: Near Field Communication

[0141] NR: New Radio

[0142] P-RNTI: Paging Radio Network Temporary Identifier

[0143] PCCH: Paging Control Channel

[0144] PDCCH: Physical Downlink Control Channel

[0145] PDU: Protocol Data Unit

[0146] PTM: Point-to-Multipoint

[0147] RAN: Radio Access Network

[0148] RAT: Radio Access Technology

[0149] RAN: RNA-based notification region

[0150] RRC: Radio Resource Control

[0151] SIB: System Information Block

[0152] TMGI: Temporary Mobility Group Identifier

[0153] TRP: Transmission Reception Point

[0154] UE: User Equipment

[0155] UI: User Interface

[0156] WCDMA: Wideband Code Division Multiple Access

[0157] WiMAX: Worldwide Interoperability for Microwave Access WLAN: Wireless Local Area Network

[0158] Reference numerals list

[0159] 110 User Equipment 112、114 Beam 115、125、135 interface 120、122 Base Station 130 Core Network 202-238 Figure 2 Steps in the signaling diagram 302-338 Figure 3 Steps in the signaling diagram 402-440 Figure 4 Steps in the signaling diagram 502-538 Figure 5 Steps in the signaling diagram 600-670 Figure 6 The structure of the device 710-730 Figure 7 The stages of the method

Claims

1. An apparatus comprising at least one processor; and at least one memory comprising computer program code; the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least: - receiving a message while the apparatus is in a radio resource control inactive state, wherein the message include: a first indication indicating a multicast broadcast service session that the apparatus has joined, and a second indication indicating to remain in the radio resource control inactive state; - and in response to receiving the message: initiating recovery of the radio resource control connection if it is determined that the device belongs to a subset of user equipment based at least on information received in the radio resource control message, and remaining in the radio resource control inactive state if it is not determined that the device belongs to the subset. 2 . The apparatus of claim 1 , wherein the subset of user devices comprises privileged user devices.

3. The apparatus according to claim 1 or 2, wherein the at least one memory and the computer program code are further configured to, together with the at least one processing core, cause the apparatus to at least: - receiving the radio resource control message, wherein the radio resource control message include: A configuration indicating that the apparatus belongs to the subset of user equipment.

4. The apparatus according to any one of the preceding claims, wherein the at least one memory and the computer program code are further configured to, together with the at least one processing core, cause the apparatus to at least: - receiving a paging message during a paging occasion; and - When the paging occasion is a paging occasion of the subset of user equipments, determining that the apparatus belongs to the subset.

5. The apparatus according to any one of the preceding claims, wherein the at least one memory and the computer program code are further configured to, together with the at least one processing core, cause the apparatus to at least: - When the apparatus is configured as a privileged user device, determining that the apparatus belongs to the subset.

6. The apparatus according to any one of the preceding claims, wherein the message further include: An indication indicating whether user equipment belonging to the subset is to initiate the resumption of the radio resource control connection in response to reception of the message.

7. The apparatus according to any one of the preceding claims, wherein the at least one memory and the computer program code are further configured to, together with the at least one processing core, cause the apparatus to at least: - determining that the apparatus is to initiate the resumption of the radio resource control connection based on a parameter representing a percentage or a fraction of user equipments in the subset that are to initiate the resumption of the radio resource control connection.

8. The apparatus of claim 7, wherein the at least one memory and the computer program code are further configured to, together with the at least one processing core, cause the apparatus to at least: - receiving the parameters in a broadcast message or a paging message.

9. The apparatus of any one of the preceding claims, wherein the at least one memory and the computer program code are further configured, together with the at least one processing core, such that the apparatus at least: - in case it is determined that the apparatus belongs to the subset of user equipments, ignoring the second indication.

10. The apparatus of any one of the preceding claims, wherein the at least one memory and the computer program code are further configured, together with the at least one processing core, such that the apparatus at least: - starting a timer when the device is moved to the radio resource control inactive state; and - When the timer runs, determining that the device belongs to a subset of user equipments.

11. The apparatus of any preceding claim, wherein the radio resource control message is a radio resource control release message, a radio resource control reconfiguration message, or a radio resource control setup message.

12. The apparatus according to any one of the preceding claims, wherein the apparatus is a user equipment, or a control device configured to control a function of the user equipment.

13. A method, include: - receiving, by a device while the device is in a radio resource control inactive state, a message, wherein the message comprises: a first indication indicating a multicast broadcast service session that the device has joined, and a second indication indicating to remain in the radio resource control inactive state; - and in response to receiving the message: initiating recovery of the radio resource control connection if the device determines, at least based on information received in the radio resource control message, that the device belongs to a subset of user equipment, and remaining in the radio resource control inactive state if the device does not determine that the device belongs to the subset.

14. A device, include: - means for receiving a message when the apparatus is in a radio resource control inactive state, wherein the message comprises: a first indication indicating a multicast broadcast service session that the apparatus has joined, and a second indication indicating to remain in the radio resource control inactive state; - and in response to receiving the message: means for initiating restoration of the radio resource control connection if it is determined, at least based on information received in the radio resource control message, that the apparatus belongs to a subset of user equipment, and means for maintaining the radio resource control inactive state if it is not determined that the apparatus belongs to the subset.

15. The apparatus of claim 14, wherein the subset of user devices comprises privileged user devices.

16. The device according to claim 14 or 15, further comprising: include: - means for receiving said radio resource control message, wherein said radio resource control message comprises a configuration indicating that said apparatus belongs to said subset of user equipments.

17. The device according to any one of claims 14 to 16, further comprising: include: - means for receiving a paging message during a paging occasion; as well as - means for determining that said apparatus belongs to said subset when said paging occasion is a paging occasion of said subset of user equipments.

18. The device according to any one of claims 14 to 17, further comprising: include: - means for determining that the apparatus belongs to the subset when the apparatus is configured as a privileged user device.

19. The apparatus according to any one of claims 14 to 18, wherein the message further include: An indication indicating whether user equipment belonging to the subset is to initiate the resumption of the radio resource control connection in response to reception of the message.

20. The device according to any one of claims 14 to 19, further comprising: include: - means for determining that the apparatus is to initiate said restoration of the radio resource control connection based on a parameter representing a percentage or a fraction of user equipments in said subset that are to initiate said restoration of the radio resource control connection.

21. The device according to claim 20, further comprising: include: - means for receiving said parameters in a broadcast message or a paging message.

22. The device according to any one of claims 14 to 21, further comprising: include: - means for ignoring the second indication if it is determined that the apparatus belongs to the subset of user equipments.

23. The device according to any one of claims 14 to 22, further comprising: include: - means for starting a timer when the apparatus is moved to the radio resource control inactive state; as well as - means for determining, when said timer is running, that said apparatus belongs to a subset of user equipments.

24. The apparatus according to any one of claims 14 to 23, wherein the radio resource control message is a radio resource control release message, a radio resource control reconfiguration message, or a radio resource control setup message.

25. The apparatus according to any one of claims 14 to 24, wherein the apparatus is a user equipment, or a control device configured to control a function of the user equipment.

26. A computer program comprising instructions which, when executed by an apparatus, cause the apparatus to: - receiving, by the device while the device is in a radio resource control inactive state, a message, wherein the message include: a first indication indicating a multicast broadcast service session that the apparatus has joined, and a second indication indicating to remain in the radio resource control inactive state; - and in response to receiving the message: initiating recovery of the radio resource control connection if the device determines, at least based on information received in the radio resource control message, that the device belongs to a subset of user equipment, and remaining in the radio resource control inactive state if the device does not determine that the device belongs to the subset.

27. An apparatus comprising at least one processor; and at least one memory comprising computer program code; the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to at least: - sending a message to at least one user equipment when the at least one user equipment is in a radio resource control inactive state, wherein the message include: a first indication indicating a multicast broadcast service session that the at least one user equipment has joined, and a second indication indicating to remain in the radio resource control inactive state; as well as - sending an indication to a neighbouring radio network node indicating a subset of user equipments, wherein the user equipments in the subset are to initiate restoration of a radio resource control connection in response to receiving the message.

28. The apparatus of claim 27, wherein the indication is sent to the neighboring wireless network when releasing the at least one user equipment to the radio resource control inactive state or when performing radio access network paging.

29. A method, include: - sending, by a device, a message to at least one user equipment when the at least one user equipment is in a radio resource control inactive state, wherein the message comprises: a first indication indicating a multicast broadcast service session that the at least one user equipment has joined, and a second indication indicating to remain in the radio resource control inactive state; and - sending, by the apparatus, an indication to a neighbouring radio network node indicating a subset of user equipments, wherein the user equipments in the subset are to initiate restoration of a radio resource control connection in response to receiving the message.

30. A device, include: - means for sending a message to at least one user equipment when the at least one user equipment is in a radio resource control inactive state, wherein the message comprises: a first indication indicating a multicast broadcast service session that the at least one user equipment has joined, and a second indication indicating to remain in the radio resource control inactive state; and - means for sending an indication to a neighbouring radio network node indicating a subset of user equipments, wherein said user equipments in said subset are to initiate restoration of a radio resource control connection in response to receiving said message.

31. The apparatus of claim 30, wherein the indication is sent to the neighboring wireless network when releasing the at least one user equipment to the radio resource control inactive state or when performing radio access network paging.

32. A computer program comprising instructions which, when executed by an apparatus, cause the apparatus to: - sending a message by the apparatus to the at least one user equipment when the at least one user equipment is in a radio resource control inactive state, wherein the message include: a first indication indicating a multicast broadcast service session that the at least one user equipment has joined, and a second indication indicating to remain in the radio resource control inactive state; as well as - sending, by the apparatus, an indication to a neighbouring radio network node indicating a subset of user equipments, wherein the user equipments in the subset are to initiate restoration of a radio resource control connection in response to receiving the message.

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