Patent Description:
In the new <NUM> standard, the system and architecture for <NUM> and various state machines are described. One example of a "state machine" is the connection management state model or CM-state model, described in 3GPP TS <NUM>. Generally, connection management includes functions for establishing and releasing signaling connections between a UE and core network node. For <NUM>, this core network node is called an Access and Mobility Management Function (AMF). A signaling connection over an N1 interface (between a UE and AMF) is used to enable Non-Access-Stratum (NAS) signaling exchange between the UE and the core network. It comprises both the AN (Access Node) signaling connection between the UE and the AN, and an N2 connection, between the AN and the AMF.

In the <NUM> architecture, there are two CM-states defined, CM-IDLE and CM-CONNECTED. A UE in CM-IDLE has no NAS signaling connection established over N1 to the AMF and in this CM-state, the UE performs cell selection/reselection and PLMN selection. In addition, there is no AN signaling connection or N2/N3 connections for a UE in idle state. If the UE is registered to the network and in CM-IDLE, it may listen to and respond to paging messages from the network. This means that in CM-IDLE the UE is still reachable. If initiated by user/UE, the UE may also perform a service request procedure.

A UE in CM-CONNECTED is a UE that has established an AN signaling connection between the UE and the AN has entered the RRC_CONNECTED state over 3GPP access. Over this connection, the UE can transmit an initial NAS message (for example, a service request) and this message initiates the transition from CM-IDLE to CM-CONNECTED in the AMF. It is also realized that CM-CONNECTED uses an N2 connection, between the AN and the AMF. The reception of an initial N2 message (e.g., N2 Initial UE message) initiates the transition for AMF from CM-IDLE to the CM-CONNECTED state.

In the CM-CONNECTED state, the UE can transmit data, and is ready to enter CM-IDLE, whenever the AN signaling connection is released. The AMF enters CM-IDLE whenever the logical N1 signaling connection and the N3 user plane connection are released.

Similar to the AMF, there is also a state model in the AN, the access network, which is described in detail in the <NUM> RRC specifications. Although, "gNB" generally refers to the access network node, other node types are contemplated, including ng-eNB and an eNB node types. The term "gNB" shall thus be considered as merely an example. From the AS (Access Stratum) perspective, UEs can either be in the RRC_CONNECTED, RRC_INACTIVE or RRC_IDLE states. The mapping between the different state machines, the one in the AN and the one in AMF, is such that CM-CONNECTED can map to either RRC_CONNECTED or RRC_INACTIVE - while CM-IDLE always maps to RRC_IDLE.

A UE is either in RRC_CONNECTED state or in RRC_INACTIVE state when an RRC connection has been established. If this is not the case, i.e. no RRC connection is established, the UE is in RRC_IDLE state. These different states are further described in 3GPP TS <NUM>.

In RRC_IDLE, the UE is configured to listen to a paging channel at certain occasions and it performs cell (re)selection procedures and listen to system information. In RRC_INACTIVE, the UE is also listening to paging channel and does cell (re)selection procedures, but in addition, it also maintains a configuration and the configuration is also kept on the network side, such that when needed (e.g., when data arrives to the UE), it doesn't require a complete setup procedure to start transmitting data.

In RRC_CONNECTED, there is transfer of data to or from the UE and the network controls the mobility. This means that the network controls when the UE should handover to other cells. In connected, the UE still monitors the paging channel and it monitors control channels that are associated with whether there is data for the UE or not. It provides channel quality and feedback information to the network and it performs neighbouring cell measurement and reports these measurements to the network.

When a UE is in CM-CONNECTED and RRC_INACTIVE the following applies:.

The AMF, based on network configuration may provide assistance information to the NG-RAN, to assist the NG-RAN's decision whether the UE can be sent to RRC inactive state. RRC inactive assistance information can, for example, include:.

The RRC inactive assistance information mentioned above is provided by the AMF during N2 activation with the (new) serving NG-RAN node (i.e. during Registration, Service Request, handover) to assist the NG-RAN's decision whether the UE can be sent to an RRC inactive state. The RRC inactive state is part of RRC state machine, and it is up to the RAN to determine the conditions to enter the RRC inactive state. If any of the parameters included in the RRC inactive assistance information changes as the result of NAS procedure, the AMF shall update the RRC inactive assistance information to the NG-RAN node.

The state of the N2 and N3 reference points are not changed by the UE entering CM-CONNECTED with RRC inactive state. A UE in RRC inactive state is aware of the RAN Notification area (RNA).

A UE in the RRC_INACTIVE state can be configured with an RNA (RAN-based Notification Area), where:.

There are several different alternatives on how the RNA can be configured:.

In CM-IDLE, it is the core network that is in charge of UE reachability and the core network does this through configuring a CN registration area that is defined by a set of Tracking Areas (TA)'s. The UE is configured with the CN registration area through a list of Tracking Area Identifiers, TAI's, and this CN Registration area is referred to as "TAI-list".

At transition into CM-CONNECTED with RRC inactive state, the NG-RAN configures the UE with a periodic RAN Notification Area Update timer taking into account the value of the Periodic Registration Update timer value indicated in the RRC Inactive Assistance Information, and uses a guard timer with a value longer than the RAN Notification Area Update timer value provided to the UE.

If the periodic RAN Notification Area Update guard timer expires in RAN, the RAN can initiate the AN Release procedure as specified in TS <NUM> [<NUM>].

When the UE is in CM-CONNECTED with RRC inactive state, the UE performs PLMN selection procedures as defined in TS <NUM> [<NUM>] for CM-IDLE.

When the UE is CM-CONNECTED with RRC Inactive state, the UE may resume the RRC connection due to:.

When Resuming, UE will include an identifier to the network that will inform the network node about where the UE context describing the specifics of the UE, e.g., bearers, tracking area, slices, security credentials/keys, and so forth) such that resuming will bring the UE to an RRC_CONNECTED configuration similar to when it was resumed. The Identifier pointing to the UE Context is called I-RNTI, Inactive Radio Network Temporary Identifier. In connection to when the UE is suspended, i.e., it is transitioned from RRC_CONNECTED to RRC_INACTIVE, it is provided with an I-RNTI from the network. The network allocates an I-RNTI when transitioning UE to RRC_INACTIVE and the I-RNTI is used to identify the UE context, i.e., as an identifier of the details stored about the UE in the network while in RRC_INACTIVE.

Much of the behaviour in RRC_INACTIVE is tightly coupled with the ability to connect a radio network to the <NUM> core network or to connect it to an AMF. Even though there is no new state in the AMF (it is still only CM CONNECTED and CM IDLE) there is still a need for the AMF to know (e.g., to provide the assistance information).

Further, as it is possible to connect the LTE/EUTRA radio network to an AMF or to the <NUM> core network, all the procedures that are specified for the new radio (NR) should also apply for when the long term evolution (LTE) radio access is connected to 5GC (<NUM> core network). Thus, there is a need to adapt the procedures, such as the RRC protocols, to the LTE radio protocols.

In an LTE standard, there is a procedure for suspending the UE defined in <NUM>, which was introduced in Release <NUM>. This is applicable for when LTE connects to EPC, with an MME node directly connected to the eNB, to the core network defined for E-UTRA, as described, e.g., in 3GPP TS <NUM>, including NAS procedures described in 3GPP TS <NUM>. In a way this suspend procedure applicable for nodes connecting to EPC shares some similarities with RRC_INACTIVE in that the AS context is stored such that a UE can send a resume request and information from last session can be retrieved and doesn't have to be signaled again. In another and very important way, it is not the same as RRC_INACTIVE, as the core network is in a state corresponding to CM-IDLE, i.e., it does not consider the UE connected. This means that it is the core network that does the paging when a UE is suspended in a cell that connects to EPC.

The way to indicate to the UE that it shall be suspended in EPC is to send a release message with a suspend indication, which is modeled as a cause value that means the UE goes to suspend. The specification for this message is described further in 3GPP TS <NUM>. It can be noted from the specification that there is a specific release cause defined to suspend the UE such that it can later on be resumed and AS information is stored. This is indicated as "rrc-Suspend-v1320". If the UE is suspended, there is also a resumeldentity included, which the UE can include if it wants to resume and allow the network to retrieve information about the UE. Document <NPL>, discloses a method to release a wireless connection.

The examples described in the present disclosure can be used to improve signalling relating to suspending a UE, resulting in lower overhead, power savings, and improved efficiency. Other advantages may be readily apparent to one having skill in the art. Certain embodiments may have none, some, or all of the recited advantages. Advantageous embodiments of the invention are given in the sub-claims.

In a number of ways, the suspend procedure for LTE is similar to what is going to be introduced for NR and for connecting to the new network with an AMF node. In the case of transitioning to RRC_INACTIVE, there is also a suspend procedure needed, to signal to the UE that it should enter an RRC_INACTIVE state. In NR, for a release message with a suspend indication, there is no release cause included. The inclusion of a suspend configuration in itself could indicate to the UE that the release message means release-to-RRC_INACTIVE. Without the suspend configuration, the release message means Release to RRC_IDLE. In some examples, the suspend configuration is indicated by a field such as RRC-InactiveConfig or suspendConf.

In NR, there is no legacy to consider. This means that a suspend in NR is always a suspend to RRC_INACTIVE. This makes it possible to go thin on distinguishing different cause values. When a corresponding suspend mechanism should be introduced in LTE when connecting to 5GC, which is an existing message, there are advantages in clearly differentiating between the different suspend to an idle state (RRC_IDLE, which is already supported in LTE) and suspend to an inactive state (RRC_INACTIVE), which is new for LTE.

In addition to the above, it is also desired in NR to consider a situation when a release message only should include information that is new, i.e., that is changed from previous signaling (i.e., delta signaling of the RRC release message or at least the suspend configuration). In this situation there may be a confusion in what the suspend configuration in the release message means. For example, if a release message without any suspend configuration indication is received by a UE, it would be ambiguous whether the UE shall release to an idle state, or would it mean that it is a suspend to an inactive with no changes in the suspend configuration.

There currently exist certain challenge(s). In more detail, there is a need to be able to differentiate between suspend to an idle state and suspend to an inactive state when a release message is used to suspend UE. This is particularly important for LTE, as in LTE, there are two different suspend mechanisms.

For NR and for LTE connected to 5GC, there is also a need to distinguish between a release message that suspend a UE to RRC_INACTIVE with no changes in suspendConfig and a release message that suspends a UE to RRC_IDLE.

Certain aspects of the present disclosure and their embodiments may provide solutions to these or other challenges.

In one aspect, a release cause value is included in the RRC release message in LTE to indicate to a UE that the release is due to transition to RRC_INACTIVE. The indication can be implicit or explicit to enable the UE to distinguish between a suspension to an idle state or to an inactive state. Different embodiments describe the different types of indications, for example the presence of one or two specific parameters only relevant for a given state like inactive, etc. Although we say this is about LTE the fundamental aspect that can be applicable to any RAT (like NR) is the distinction between is the suspend to idle (LTE Release <NUM> solution) or suspend to inactive, where some actions performed are common, but some are specific for each solution.

In another aspect, a release cause included in the RRC message when the suspend to inactive is signaled in LTE RRC Connection Release message is different than the release cause used for suspending an LTE UE to idle. UE actions upon suspending may be distinguished based on that indication. For example, when suspending to inactive the UE apply some exclusive parameters such as RAN paging configuration, RNA update configurations, periodic RNA timer, etc..

In another aspect, the release cause included is implicit, i.e., by including a new identifier value in suspendConfig that is valid for release to RRC_INACTIVE.

In another aspect, a release cause is included also in the release message when signaled in NR, such that it can allow for not including suspendConfig unless there are changes to the configuration that are to be signaled.

In another aspect, including an explicit or implicit identifier will allow delta-signaling of RRC_INACTIVE-related information that would otherwise not be possible, if there weren't a release cause.

In another aspect, the AS and NAS layers in the UE interact so that the release cause distinguishing the UE to enter RRC_IDLE or RRC_INACTIVE is provided from the lower layers to the upper layers upon the reception of the RRC Release message so that the upper layers can perform an unambiguous transition from a connected state to an idle state or, in the case of the indication to enter an inactive state, to remain in a connected state from an upper layer perspective.

There are, proposed herein, various embodiments which address one or more of the issues disclosed herein, and may provide one or more of the following technical advantage(s).

In some embodiments, the techniques described herein allow for both differentiation of suspend in LTE connecting to both EPC and 5GC. In some embodiments, the techniques described herein allow for indicating to a UE if the release message is a release to RRC_INACTIVE or a release to RRC_IDLE.

Moreover, by including a release cause also in NR, the techniques allow delta-signaling of the configuration parameters that are applicable for RRC_INACTIVE state. The release cause offers the advantage of not including new suspendConfig values where the values are not changed, and thus includes signal parameters in the suspendConfig only when they are changed. This will save in signaling, resulting in lower overhead, power savings, and improved efficiency, among other things.

<FIG> is a flow diagram illustrating an example method for transitioning a user equipment to an RRC_INACTIVE state. For example, the method illustrates signaling in NR connected to 5GC, according to some embodiments.

Step <NUM>, the UE receives a release message from the network. In this example the UE is in RRC_CONNECTED and is about to be released. The reasons for releasing a UE in RRC_CONNECTED can vary. It can for example be due to inactivity, or due to that there is no more data to send and/or receive.

In step <NUM>, the UE reads and interprets the release message. If there is an indication in the release message that the release refers to a suspend to RRC_INACTIVE, then the UE proceeds to step <NUM>. That indication can be a release-cause 'suspend'. If, on the other hand, the release message does not include such an indication (e.g. include another release cause instead), the release message is not about Release to RRC_INACTIVE, but it is rather sent for other purposes, this is illustrated in the figure as <NUM>. In some examples, the release is to RRC_IDLE but there could also be other situations when a release message may mean something different. In this embodiment, focus is on whether the indication to RRC_INACTIVE is included.

The indication helps the UE to apply delta signalling to the suspend configuration. If that indication does not exist, the absence of the suspend configuration field could be interpreted as an indication from the network to move the UE to RRC_IDLE. However, based on that indication, the UE knows that the absence of the suspend configuration field means that the UE can apply delta signalling to a previously stored suspend configuration. In other words, the UE can enter RRC_INACTIVE and use the stored suspend configuration when entering RRC_INACTIVE.

If included, in step <NUM>, the UE checks for a new suspendConfig and reads any new potential suspendConfig information that relates to how the UE should behave/be configured in RRC_INACTIVE state.

If suspendConfig information is included, the UE replaces any stored suspendConfig information. For any suspendConfig information not included in the release message, if a UE has a stored version of this information, that is used and applied in the RRC_INACTIVE state. In step <NUM>, UE transitions to RRC_INACTIVE.

It should be noted that these are not all steps that are relevant to make for a UE when transitioning to RRC_INACTIVE. For example, there are aspects related to that the lower level protocols of the UE / UE Access Stratum should communicate with higher layer protocols / UE NON-Access Stratum, that are not illustrated.

The description is applicable in various settings and may include additional signaling.

<FIG> is a flow diagram illustrating an example method for transitioning a user equipment to an RRC_INACTIVE state, including an additional cause value indication. For example, the method illustrates signaling in LTE connected to 5GC, according to some embodiments.

Illustrating a situation when a UE is using LTE as radio network or any radio network where there could be different solutions to suspend the UE, such as the Release-<NUM> solution (suspend to RRC_IDLE) or the Release-<NUM> solution (Suspend to RRC_INACTIVE). The radio network node can connect to either EPC (an MME + Serving Gateway) or a <NUM> Core Network (to an AMF + a User Plane Function) or both.

In the situation an LTE UE is receiving an RRC Release message <NUM>, it can first, in step <NUM> consider if the Release message includes an RRC Inactive Indication (which can be implemented as a release cause e.g. 'suspend-inactive'). If this is not the case, it can consider whether there is an indication to suspend to IDLE, this is step <NUM>. In the figure, it is illustrated as a v1320 cause value, but this cause value may be equally applicable also to other standard versions than standard release <NUM>. In this situation, it may be called suspend cause v15 or suspend cause b16 or anything else. It is noted that this is a suspend to idle rather than a suspend to inactive, which was what was determined in step <NUM>. If there is no suspend indication to IDLE either, then it is concluded in step <NUM>. This may mean that the UE is released to IDLE without any need to save any AS. If there was a suspend-to-IDLE indication in step <NUM>, then in step <NUM>, the UE releases to IDLE and stores the AS configuration according to what is standardized for this procedure.

If the release to inactive indication in step <NUM> was included, then this indication would, in a similar way as for <FIG> and NR, mean that the UE should check for a new suspendConfig and read any new potential suspendConfig information that relates to how the UE should behave / be configured in RRC INACTIVE state in step <NUM>. In step <NUM>, the UE transitions to RRC_ INACTIVE.

In connection to both example procedures above, it has been stated in step <NUM>/<NUM> that the UE should check the release message to determine if it includes a suspend to RRC_INACTIVE indication. Examples of the indication are discussed in further detail below.

In one aspect of the present disclosure, the suspend-to-RRC_INACTIVE indication is a cause value included in the RRC signaling.

Taking the signaling specified for LTE as example, the suspend to RRC_INACTIVE may be added to a set of already existing release cause values or to include a completely different set of ReleaseCauses for LTE, to use in release messages, when a UE is connected to 5GC. In other examples, there could be situations when a UE that connects to 5GC actually has two different suspend mechanisms available for selection.

In some examples, the ReleaseCause-<NUM> is a <NUM>-bit field, (<NUM> values) but it can of course be of different size. Similarly, for NR connected to 5GC, a release cause may be included similar to LTE connected to 5GC. It should be noted that in both cases above, both for NR and for LTE, there can of course be other cause values. The technique is applicable to presence of suspend causes, both in situations where there are other causes or not.

An alternative way of indicating a release to RRC_INACTIVE can, according to another aspect of the present disclosure, be based on presence or absence of the suspend configuration information. A suspend configuration informs the UE how to configure/Behave in RRC_INACTIVE state and can both be called different things and it can include more or less fields. In some examples, the suspend configuration includes resumeldentity, pagingCycle, ran-NotificationArealnfo, periodic-RNAU-timer, and nextHopChainingCount information elements. A paging cycle is a repetition frequency indicating time instances when the UE shall listen for pages from the network. The suspend configuration, in this example, further includes the RNA area and a timer for periodic updates of RNAU. The suspend configuration, in this example, also includes an NCC NextHopChaining count value which is a security-related parameter.

One way of indicating to suspend to RRC_INACTIVE is to include the resumeldentity in the suspend configuration message. A criteria in e.g., <NUM>/<NUM> above would then be that if the resumeldentity is included, it is a suspend to RRC_INACTIVE. If the resumeldentity is not included, and the suspend configuration is either empty or not present in the release message, then it is a release to RRC_IDLE, or it is a suspend to RRC_IDLE or it is at least not release to RRC_INACTIVE.

According to one aspect of the present disclosure, there is thus then only one information element that is mandatory if the suspend configuration is included in the release message and that is the resumeldentity. This means that the rest of the information elements (e.g., pagingCycle, ran-NotificationArealnfo, periodic-RNAU-timer, and nextHopChainingCount) could be optionally included. If they are not included, it could be possible to allow the UE to use previously received information for any of these information elements without the need to signal them again.

It should be noted that both options can be equally applicable both for LTE and NR when performing transitions to RRC_INACTIVE and when such transition is signaled or triggered by a release message, as described above.

In some examples, if an RRC release message (e.g., RRCRelease) includes a suspend configuration field (e.g., suspendConfig, RRC-lnactiveConfig), the user equipment stores the following parameters of the suspend configuration: resumeldentity, nextHopChainingCount, PagingCycle and ran-NotificationArealnfo information, if these are not already stored. Delta signalling is applied to resumeldentity, nextHopChainingCount, PagingCycle and ran-NotificationArealnfo, if they are stored. If the RRC release message does not include the suspend configuration filed, the user equipment uses the values stored at the UE for the following parameters of the suspend configuration: resumeldentity, nextHopChainingCount, PagingCycle and ran-NotificationArealnfo.

<FIG> is a flow diagram illustrating an example method performed by a user equipment for transitioning to an inactive state or an idle state.

At step <NUM>, user equipment that is operating in a connected state receives an RRC release message. In the present example, the connected state is the RRC_CONNECTED state.

At step <NUM>, the user equipment determines, based on an indication in the RRC release message, whether to suspend the user equipment to an inactive state or an idle state, the indication comprising a presence or absence a suspend configuration field in the RRC release message. In the present example, the inactive state is the RRC_INACTIVE state and the idle state is the RRC_IDLE state.

In some examples, the indication to suspend the user equipment to the inactive state includes the presence of a suspend configuration field in the RRC release message and the indication to suspend the user equipment to the idle state comprises the absence of a suspend configuration field in the RRC release message. The suspend configuration field may be, for example, suspendConf or RRC-InactiveConfig. In some examples, the suspend configuration field indicates a configuration corresponding to the inactive state.

At step <NUM>, responsive to determining that the indication is to suspend to an inactive state, the user equipment transitions to the inactive state. For example, the transitioning of the user equipment to the inactive state may be performed during a connection of the user equipment to a <NUM> core network from a long term evolution (LTE) network.

In some examples, the user equipment applies delta signaling corresponding to a suspend configuration indicated by the suspend configuration field, where the delta signaling includes receiving changed suspend configuration information indicated by the suspend configuration field and accessing unchanged suspend configuration information from previously stored suspend configuration information on the user equipment. In some examples, the suspend configuration includes RAN Notification Area (RNA) information, and delta signalling is applied to update this RNA information in the suspend configuration.

<FIG> is a flow diagram illustrating an example method performed by a network node for transitioning a user equipment to an inactive state or an idle state, according to some examples.

At step <NUM>, a network node provides an RRC release message to a user equipment that is operating in a connected state. In the present example, the connected state is the RRC_CONNECTED state.

At step <NUM>, the network node triggers, based on an indication in the RRC release message, a suspension of the user equipment to an inactive state or an idle state, the indication comprising a presence or absence a suspend configuration field in the RRC release message. In the present example, the inactive state is the RRC_INACTIVE state and the idle state is the RRC_IDLE state.

At step <NUM>, the network node causes, responsive to the indication being to suspend to an inactive state, the user equipment to transition to the inactive state. For example, the transitioning of the user equipment to the inactive state may be performed during a connection of the user equipment to a <NUM> core network from a long term evolution (LTE) network.

In some examples, the user equipment applies delta signaling corresponding to a suspend configuration indicated by the suspend configuration field, where the delta signaling includes providing changed suspend configuration information indicated by the suspend configuration field, wherein the user equipment accesses unchanged suspend configuration information from previously stored suspend configuration information on the user equipment. In some examples, the suspend configuration includes RAN Notification Area (RNA) information, and delta signalling is applied to update this RNA information in the suspend configuration.

<FIG> is a block diagram illustrating an example wireless network. Although the subject matter described herein may be implemented in any appropriate type of system using any suitable components, the embodiments disclosed herein are described in relation to a wireless network, such as the example wireless network illustrated in <FIG>. For simplicity, the wireless network of <FIG> only depicts network <NUM>, network nodes <NUM> and 560b, and WDs <NUM>, 510b, and 510c. In practice, a wireless network may further include any additional elements suitable to support communication between wireless devices or between a wireless device and another communication device, such as a landline telephone, a service provider, or any other network node or end device. Of the illustrated components, network node <NUM> and wireless device (WD) <NUM> are depicted with additional detail. The wireless network may provide communication and other types of services to one or more wireless devices to facilitate the wireless devices' access to and/or use of the services provided by, or via, the wireless network.

As used herein, wireless device (WD) refers to a device capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other wireless devices. Unless otherwise noted, the term WD may be used interchangeably herein with user equipment (UE). Communicating wirelessly may involve transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information through air. In some embodiments, a WD may be configured to transmit and/or receive information without direct human interaction. For instance, a WD may be designed to transmit information to a network on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the network. Examples of a WD include, but are not limited to, a smart phone, a mobile phone, a cell phone, a voice over IP (VoIP) phone, a wireless local loop phone, a desktop computer, a personal digital assistant (PDA), a wireless cameras, a gaming console or device, a music storage device, a playback appliance, a wearable terminal device, a wireless endpoint, a mobile station, a tablet, a laptop, a laptop-embedded equipment (LEE), a laptop-mounted equipment (LME), a smart device, a wireless customer-premise equipment (CPE). a vehicle-mounted wireless terminal device, etc.. A WD may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-everything (V2X) and may in this case be referred to as a D2D communication device. As yet another specific example, in an Internet of Things (IoT) scenario, a WD may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another WD and/or a network node. The WD may in this case be a machine-to-machine (M2M) device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the WD may be a UE implementing the 3GPP narrow band internet of things (NB-loT) standard. Particular examples of such machines or devices are sensors, metering devices such as power meters, industrial machinery, or home or personal appliances (e.g. refrigerators, televisions, etc.) personal wearables (e.g., watches, fitness trackers, etc.). In other scenarios, a WD may represent a vehicle or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation. A WD as described above may represent the endpoint of a wireless connection, in which case the device may be referred to as a wireless terminal. Furthermore, a WD as described above may be mobile, in which case it may also be referred to as a mobile device or a mobile terminal.

Claim 1:
A method performed by a user equipment, UE, the method comprising:
receiving (<NUM>) a radio resource control, RRC, release message, while operating in a connected state, the RRC release message only including information that is changed from a previous signalling, i.e. delta signalling of a suspend configuration of the RRC release message;
determining (<NUM>), based on an indication in the RRC release message, to suspend the UE to an inactive state when the indication comprises a suspend configuration field;
applying the delta signalling corresponding to the suspend configuration indicated by the suspend configuration field, wherein applying the delta signalling includes:
receiving the changed suspend configuration information indicated by the suspend configuration field; and
accessing unchanged suspend configuration information from previously stored suspend configuration information on the UE; and
transitioning (<NUM>) the UE to the inactive state, responsive to the determining to suspend the UE to the inactive state.