Technical Field

The present disclosure relates to a connection resume procedure in a cellular communications system.

Background

1. Fifth Generation (5G) System (5GS)

The Third Generation Partnership Project (3GPP) 5GS is currently being developed. The 5GS includes a Next Generation Radio Access Network (NG-RAN) and a 5G Core (5GC). Some aspects of the 5GS that are relevant to the present disclosure are described below.

1.1. Radio Resource Control (RRC) Inactive State

As described in 3GPP Technical Specification (TS) 38.300 V16.0.0, the RRC inactivate state (RRC_IN ACTIVE) is a state where a User Equipment (UE) remains in Connection Management Connected (CM-CONNECTED) state and can move within an area configured by the NG-RAN, which is referred to as the Radio Access Network (RAN) Notification Area (RNA), without notifying the NG-RAN. The last serving New Radio (NR) base station (gNB) node keeps the UE context and the UE-associated Next Generation (NG) connection with the serving Access and Mobility Management Function (AMF) and User Plane Function (UPF) in the 5GC.

1.2. RAN Paging to Path Switch

When the last serving gNB detects an incoming downlink data transfer or downlink NG Access Point (AP) signaling for a UE in RRC_INACTIVE, a RAN paging is initiated. The last serving gNB can try to reach the UE by sending RRC Paging messages in NR cells under its control as well as XnAP RAN PAGING messages towards all the other gNBs included in the RNA (neighbor gNB(s)).

At reception of an XnAP RAN PAGING message, the neighbor gNBs attempt to find the UE by sending RRC Paging messages to all the controlled NR cells. If the UE is found in a gNB other than the last serving gNB, i.e. one of the neighbor gNBs, then that gNB (referred to as the target gNB) receives an RRC Resume attempt from the UE. The target gNB where the UE is responding to the RRC paging tries to fetch the UE Context from the last serving gNB via an XnAP Retrieve UE Context procedure.

If the XnAP Retrieve UE Context procedure is successful (i.e., if the target gNB receives the UE Context from the last serving gNB), the target gNB can request a path switch towards the 5GC and the release of the UE Context in the last serving gNB.

1.3. RRC Release with Redirect

In response to the RRC Resume attempt of an incoming UE, the target gNB may choose to perform Release with Redirect to a selected NR or Evolved Universal Terrestrial Radio Access Network (E-UTRAN) frequency by sending an RRCRelease message to the UE and include in the RRCRelease message the redirectedCarrierlnfo field, which contains a configuration indicating a target frequency where the UE is to perform cell selection upon entering RRC_IDLE or RRC_INACTIVE state. As an example, this behavior can be triggered if the NR cell of the target gNB is not able to provide the requested service (e.g., a mobile terminated voice call) while other candidate NR/E-UTRAN frequencies exist.

In the described scenario, the target network may either transition the UE to RRC_INACTIVE (e.g., if redirection is towards an NR frequency) or RRC_IDLE (e.g., if redirection is towards another Radio Access Technology (RAT), like Long Term Evolution (LTE).

An example signaling flow for RAN Paging followed by RRC Release with Redirect is shown in Figure 1. As illustrated, the last serving gNB sends an XnAP RAN PAGING message to the gNB (step 100). The gNB sends an RRC Paging message to the UE (step 102). The UE responds with an RRCResumeRequest/Requestl message (step 104). The gNB (i.e., the target gNB) sends an XnAP RETRIEVE UE CONTEXT REQUEST to the last serving gNB (step 106). The last serving gNB responds with an XnAP RETRIEVE UE CONTEXT RESPONSE (step 108). In response, the target gNB sends an NGAP PATH SWITCH REQUEST to the AMF (step 110), and the AMF responds with an NGAP PATH SWITCH REQUEST ACKNOWLEDGE (step 112). The target gNB sends an RRCRelease with Redirect to the UE (step 114) and an XnAP UE CONTEXT RELEASE to the last serving gNB (step 116).

As described in Figure 1, four messages are required after the RRC Resume attempt before the RRC Release with Redirect can be sent. These four messages are: • XnAP: RETRIEVE UE CONTEXT REQUEST,

• XnAP: RETRIEVE UE CONTEXT RESPONSE,

• NGAP: PATH SWITCH REQUEST, and

• NGAP: PATH SWITCH REQUEST ACKNOWLEDGE.

The delay introduced by the steps above can be described as: RTT_UeCtxtFetch + RTT_PathSwitch, where:

• RTT_UeCtxtFetch is the delay for UE Context fetch over Xn (steps 106 and 108), and

• RTT_PathSwitch is the delay for Path Switch over NG (steps 110 and 112).

Note that in case of UE Resume attempt in the last serving gNB, XnAP RAN PAGING as well as steps 106-112 are not needed and no extra delay is introduced.

In the scenario where the target gNB transitions the UE to RRC_INACTIVE, the target gNB gets a fresh Next Hop (NH) Chaining Count (NCC), NH pair (denoted herein as "{NCC, NH} pair") before sending the RRCRelease message to the UE. After the target gNB receives a fresh {NCC, NH} pair in the NGAP PATH SWITCH REQUEST ACKNOWLEDGE message from the AMF, the target gNB sets the value of NCC in the RRCRelease message to the NCC value of the received fresh {NCC, NH} pair.

1.4. RAN Paging followed by completion of the RRC Resume in Target gNB

In the scenario described in this section, the target gNB decides to serve the UE and continues the RRC Resume procedure as shown in Figure 2. In this case, the NGAP Path Switch procedure is performed after reception of RRCResumeComplete. In particular, as illustrated in Figure 2, the last serving gNB sends an XnAP RAN PAGING message to the gNB (step 200). The gNB sends an RRC Paging message to the UE (step 202). The UE responds with an RRCResumeRequest/Requestl message (step 204). The gNB (i.e., the target gNB) sends an XnAP RETRIEVE UE CONTEXT REQUEST to the last serving gNB (step 206). The last serving gNB responds with an XnAP RETRIEVE UE CONTEXT RESPONSE(step 208). The target gNB sends an RRCResume message to the UE (step 210), and the UE responds with an RRCResumeComplete message (step 212). The target gNB sends an NGAP PATH SWITCH REQUEST to the AMF (step 214), and the AMF responds with an NGAP PATH SWITCH REQUEST ACKNOWLEDGE (step 216). The target gNB sends an XnAP UE CONTEXT RELEASE to the last serving gNB (step 218). Note that, in this scenario where the target gNB transitions the UE to RRC_CONNECTED, the target gNB does not need to include a fresh NCC in the RRCResume message towards to UE and no NGAP Path Switch procedure is required before the target gNB sends RRCResume.

1.4.1. RRCRelease

The RRCRelease message is used to command the release of an RRC connection or the suspension of the RRC connection. The Signaling Radio Bearer (SRB) for the RRCRelease message is SRB1. The Radio Link Control (RLC) Service Access Point (RLC- SAP) is Acknowledgment Mode (AM). The logical channel is Dedicated Control Channel (DCCH), and direction is from the network to the UE. The following definition of the RRCRelease message is from the 3GPP specifications:

RRCRelease message

— ASNlSTART

— TAG-RRCRELEASE-START

RRCRelease ::= SEQUENCE { rrc-Transaction]!dentifier RRC- Transactionldentifier, criticalExtensions CHOICE { rrcRelease RRCRelease-IEs, criticalExtensionsFuture SEQUENCE {}

}

}

RRCRelease-IEs ::= SEQUENCE { redirectedCarrierInfo RedirectedCarrierlnfo

OPTIONAL, Need N celIReselectionPriorities CelIReselectionPriorities OPTIONAL, — Need R suspendConfig SuspendConfig OPTIONAL, — Need R deprioritisationReq SEQUENCE { deprioritisationType ENUMERATED {frequency, nr}, deprioritisationTimer ENUMERATED {min5 minlO, mini5, min30}

}

OPTIONAL, — Need N lateNonCriticalExtension OCTET STRING

OPTIONAL, nonCriticalExtension RRCRelease-vl540-

IEs OPTIONAL

}

RRCRelease-vl540-IEs ::= SEQUENCE { waitTime RejectWaitTime

OPTIONAL, — Need N nonCriticalExtension SEQUENCE {}

OPTIONAL

}

RedirectedCarrierlnfo :: ^: CHOICE { nr CarrierlnfoNR, eutra RedirectedCarrierlnfo-

EUTRA,

}

RedirectedCarrierlnfo-EUTRA :: SEQUENCE { eutraFrequency ARFCN-ValueEUTRA, _ cnType _ ENUMERATED

{ epc , fiveGC }

OPTIONAL — Need N

I

CarrierlnfoNR ::= SEQUENCE { carrierFreq ARFCN-ValueNR, ssbSubcarrierSpacing SubcarrierSpacing, smtc SSB-MTC

OPTIONAL, — Need S

}

SuspendConfig ::= SEQUENCE { fulll-RNTI I-RNTI-Value, shortI-RNTI ShortI-RNTI-Value, ran-PagingCycle PagingCycle, ran-NotificationArealnfo RAN-

NotificationArealnfo

OPTIONAL, — Need M 1380 PeriodicRNAU-TimerValue

OPTIONAL, — Need R nextHopChainingCount NextHopChainingCount,

}

PeriodicRNAU-TimerValue ::= ENUMERATED { min5, minlO, min20, min30, min60, minl20, min360, min720}

CellReselectionPriorities : SEQUENCE { freqPriorityListEUTRA FreqPriorityListEUTRA OPTIONAL, — Need M freqPriorityListNR FreqPriorityListNR OPTIONAL, — Need M

1320 ENUMERATED {min5, minlO, min20, min30, min60, minl20, minl80, sparel} OPTIONAL, -- Need R

}

PagingCycle ::= ENUMERATED {rf32, rf64, rf128, rf256}

FreqPriorityListEUTRA ::= SEQUENCE (SIZE

(1..maxFreq)) OF FreqPriorityEUTRA

FreqPriorityListNR ::= SEQUENCE (SIZE

(1..maxFreq)) OF FreqPriorityNR

FreqPriorityEUTRA ::= SEQUENCE { carrierFreq ARFCN-ValueEUTRA, cellReselectionPriority

CellReselectionPriority, cellReselectionSubPriority CellReselectionSubPriority OPTIONAL — Need R

}

FreqPriorityNR ::= SEQUENCE { carrierFreq ARFCN-ValueNR, cellReselectionPriority

CellReselectionPriority, cellReselectionSubPriority CellReselectionSubPriority OPTIONAL — Need R

}

RAN-NotificationArealnfo ::= CHOICE { cellList PLMN-RAN-AreaCellList, ran-AreaConfigList PLMN-RAN- AreaConfigList,

}

PLMN-RAN-AreaCellList ::= SEQUENCE (SIZE (1.. maxPLMNIdentities) ) OF PLMN-RAN AreaCell

PLMN-RAN-AreaCell ::= SEQUENCE { plmn-Identity PLMN-Identity OPTIONAL, — Need S ran-AreaCells SEQUENCE (SIZE (1..32)) OF Cellldentity }

PLMN-RAN-AreaConfigList ::= SEQUENCE (SIZE

(1..maxPLMNIdentities)) OF PLMN RAN-AreaConfig

PLMN-RAN-AreaConfig ::= SEQUENCE { plmn-Identity PLMN-Identity OPTIONAL, — Need S ran-Area SEQUENCE (SIZE (1..16))

OF RAN-AreaConfig

}

RAN-AreaConfig ::= SEQUENCE { trackingAreaCode TrackingAreaCode, ran-AreaCodeList SEQUENCE (SIZE (1..32)) OF RAN-AreaCode OPTIONAL -- Need R

}

— TAG-RRCRELEASE-STOP

— ASN1STOP

1.5. RRC Paging

In NR, the RRC paging procedure allows the network to reach UEs in RRC_IDLE and in RRC_INACTIVE state. The NG-RAN can trigger this procedure by transmitting the RRC paging message at the UE's Paging Occasion (PO). Figure 3 illustrates the paging process. As illustrated, the gNB sends an RRC Paging message to the UE (step 300).

The RRC Paging message is used for the notification of one or more UEs. The RLC-SAP for the RRC Paging message is Transparent Mode (TM), the logical channel for the RRC Paging message is the Paging Control Channel (PCCH), and the direction of the RRC Paging message is from the network to the UE. The following definition of the RRC Paging message is from the 3GPP specifications:

1.6. RAN Paging

The RAN Paging is realized with the XnAP RAN PAGING message sent by a first NG-RAN node (NG-RAN nodei) to a second NG-RAN node (NG-RAN node2) to page a UE. The following table from the 3GPP specifications provides the details of this message.

1.6.1. NGAP PATH SWITCH REQUEST

The NGAP PATH SWITCH REQUEST message is sent by the NG-RAN node to inform the AMF of the new serving NG-RAN node and to transfer some NG User Plane Traffic (NG-U) downlink tunnel termination point(s) to the Session Management Function (SMF) via the AMF for one or multiple Protocol Data Unit (PDU) session resources. This message is sent from the NG-RAN node to the AMF. Tables from the 3GPP specifications that provide the details of this message are provided below.

1.6.2. NGAP PATH SWITCH REQUEST ACKNOWLEDGE

The NGAP PATH SWITCH REQUEST ACKNOWLEDGE message is sent by the AMF to inform the NG-RAN node that the path switch has been successfully completed in the 5GC. Tables from the 3GPP specifications that provide the details about this message are provided below.

1.6.3. XnAP RETRIEVE UE CONTEXT REQUEST The XnAP RETRIEVE UE CONTEXT REQUEST message is sent by the new NG-

RAN node to request the old NG-RAN node to transfer the UE Context to the new NG- RAN node. A table from the 3GPP specifications that defines the details of this message is provided below.

1.6.4. XnAP RETRIEVE UE CONTEXT RESPONSE

The XnAP RETRIEVE UE CONTEXT RESPONSE message is sent by the old NG- RAN node to transfer the UE context to the new NG-RAN node. A table from the 3GPP specifications that defines the details of this message is provided below.

2. Problems with Existing Solutions

In the scenario described above in Section 1.3, the problem with the existing solution is the unnecessary delay between the RRC Resume Request and Release with Redirect when the UE tries to Resume in a target gNB that does not have the UE Context. In the scenario described above in Section 1.4, the problem with the existing solution is the unnecessary delay between the RRC Resume Request and RRC Resume Complete.

As such, there is a need for systems and methods for reducing or avoiding the aforementioned delays.

Systems and methods are disclosed herein for providing faster Radio Resource Control (RRC) from an inactive state. In one embodiment, a method for Radio Access Network (RAN) paging in a cellular communications system comprises, at a source base station, sending one or more RAN paging messages to one or more potential target base stations, respectively, for a resume of a connection of a particular User Equipment (UE). Each of the one or more RAN paging messages comprises UE context information for the particular UE. The method further comprises, at a target base station from among the one or more potential target base stations, receiving the RAN paging message from the source base station where the RAN paging message comprises the UE context information for the particular UE and storing the UE context information comprised in the RAN paging message received from the source base station. The method further comprises, at the target base station, sending a RRC Paging message to the particular UE and receiving a resume request from the particular UE. The method further comprises, at the target base station responsive to receiving the resume request from the particular UE, obtaining the stored UE context information for the particular UE and performing one or more actions related to a resume or a release procedure for resuming or releasing the connection of the particular UE based on the stored UE context information for the particular UE. By providing the UE context information to the potential target base stations in the respective RAN paging messages, the action(s) related to a resume or a release procedure can be performed more quickly than otherwise possible.

In another embodiment, a method of operation of a first base station for RAN paging in a cellular communications system comprises sending one or more RAN paging messages to one or more potential target base stations, respectively, for a resume of a connection of a particular UE, wherein each of the one or more RAN paging messages comprises UE context information for the particular UE. In some embodiments, the particular UE is in an inactive state, and the first base station is a last serving base station of the particular UE prior to entering the inactive state.

In some embodiments, the UE context information comprised in each of the one or more RAN paging messages is all or a subset of a UE Access Stratum (AS) context of the particular UE stored by the first base station.

In some embodiments, the UE context information comprised in each of the one or more RAN paging messages comprises: (a) one or more encryption or security keys associated with the particular UE, (b) a Robust Header Compression (ROHC) state of the particular UE, (c) a Radio Network Temporary Identifier (RNTI) for the particular UE in a source primary cell of the UE prior to the particular UE entering inactive state, (d) a cell identity of a source primary cell of the UE prior to the particular UE entering inactive state, (e) a physical cell identity of a source primary cell of the UE prior to the particular UE entering inactive state, (f) information regarding one or more Radio Access Technology (RAT) related UE capabilities of the particular UE, (g) one or more parameters configured for the particular UE, or (h) any combination of two or more of (a)-(g).

In some embodiments, the method further comprises sending, to a core network node, a request to prepare a path switch for each of the one or more potential target base stations. In some embodiments, the request to prepare the path switch for each of the one or more potential target base stations triggers, for each potential target base station from among the one or more potential target base stations, creation of a user plane path between the particular UE and the potential target base station. In some embodiments, the core network node is an Access and Mobility Management Function (AMF). In some embodiments, the request to prepare the path switch for each of the one or more potential target base stations comprises one or more indicators associated to the one or more potential target base stations, respectively. In some embodiments, each of the one or more RAN paging messages further comprises the indicator associated to the respective one of the one or more potential target base stations.

Corresponding embodiments of a first base station for RAN paging for a cellular communications system are also disclosed. The first base station is adapted to send one or more RAN paging messages to one or more potential target base stations, respectively, for a resume of a connection of a particular UE, wherein each of the one or more RAN paging messages comprises UE context information for the particular UE.

In some embodiments, the first base station comprises a network interface and processing circuitry associated with the network interface. The processing circuitry is configured to cause the first base station to send the one or more RAN paging messages to the one or more potential target base stations, respectively.

In another embodiment, a method of operation of a target base station for RAN paging in a cellular communications system comprises receiving a RAN paging message from a source base station for a resume of a connection of a particular UE, wherein the RAN paging message comprises UE context information for the particular UE. The method further comprises storing the UE context information comprised in the RAN paging message received from the source base station, sending a RRC paging message to the particular UE, and receiving a resume request from the particular UE. The method further comprises, responsive to receiving the resume request from the particular UE, obtaining the stored UE context information for the particular UE and performing one or more actions related to a resume procedure for resuming the connection of the particular UE based on the stored UE context information for the particular UE.

In some embodiments, the particular UE is in an inactive state, and the source base station is a last serving base station of the particular UE prior to entering the inactive state.

In some embodiments, the UE context information comprised in the RAN paging message received from the source base station is all or a subset of a UE AS context of the particular UE stored by the source base station.

In some embodiments, the UE context information comprised in the RAN paging message received from the source base station comprises: (a) one or more encryption or security keys associated with the particular UE, (b) a ROHC state of the particular UE, (c) a RNTI for the particular UE in a source primary cell of the UE prior to the particular UE entering inactive state, (d) a cell identity of a source primary cell of the UE prior to the particular UE entering inactive state, (e) a physical cell identity of a source primary cell of the UE prior to the particular UE entering inactive state, (f) information regarding one or more RAT related UE capabilities of the particular UE, (g) one or more parameters configured for the particular UE, or (h) any combination of two or more of

(a)-(g).

In some embodiments, performing the one or more actions related to a resume procedure for resuming the connection of the particular UE based on the stored UE context information for the particular UE comprises generating a release message with redirect to be sent to the particular UE based on the stored UE context information and sending the release message with redirect to the particular UE. In some embodiments, generating the release message with redirect to be sent to the particular UE based on the stored UE context information comprises encrypting the release message with redirect based on one or more encryption or security keys comprised in the stored UE context information. In some embodiments, generating the release message with redirect to be sent to the particular UE based on the stored UE context information comprises including, in the release message, one or more changes to corresponding configurations stored by the particular UE.

In some embodiments, performing the one or more actions related to a resume procedure for resuming the connection of the particular UE based on the stored UE context information for the particular UE comprises providing the particular UE with a Next Hop (NH) Chaining Count (NCC) field based on the stored UE context information.

In some embodiments, performing the one or more actions related to a resume procedure for resuming the connection of the particular UE based on the stored UE context information for the particular UE comprises generating a resume message to be sent to the particular UE based on the stored UE context information and sending the resume message to the particular UE. In some embodiments, generating the resume message to be sent to the particular UE based on the stored UE context information comprises encrypting the resume message based on one or more encryption or security keys comprised in the stored UE context information.

Corresponding embodiments of a target base station are also disclosed. In one embodiment, a target base station for RAN paging for a cellular communications system is adapted to receive a RAN paging message from a source base station for a resume of a connection of a particular UE, wherein the RAN paging message comprises UE context information for the particular UE. The target base station is further adapted to store the UE context information comprised in the RAN paging message received from the source base station, send a RRC paging message to the particular UE, and receive a resume request from the particular UE. The target base station is further adapted to, responsive to receiving the resume request from the particular UE, obtain the stored UE context information for the particular UE and perform one or more actions related to a resume procedure for resuming the connection of the particular UE based on the stored UE context information for the particular UE.

In some embodiments, the target base station comprises a network interface and processing circuitry associated with the network interface. The processing circuitry is configured to cause the target base station to receive the RAN paging message from the source base station, store the UE context information comprised in the RAN paging message received from the source base station, send the RRC paging message to the particular UE, and receive the resume request from the particular UE. The processing circuitry is further configured to cause the target base station to, responsive to receiving the resume request from the particular UE, obtain the stored UE context information for the particular UE and perform the one or more actions related to a resume procedure for resuming the connection of the particular UE based on the stored UE context information for the particular UE.

The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

Figure 1 is a signaling flow for the existing solution for Radio Access Network (RAN) paging followed by Radio Resource Control (RRC) release with redirect;

Figure 2 is a signaling flow for the existing solution for RAN paging followed by completion of the RRC resume in the target base station;

Figure 3 is a signaling flow for RRC paging in a New Radio (NR) network;

Figure 4 illustrates one example of a cellular communications system in which embodiments of the present disclosure may be implemented;

Figures 5 and 6 are example representations of the cellular communications network of Figure 4 in which the cellular communications system is a Fifth Generation (5G) System (5GS); Figure 7 illustrates a process for RAN paging followed by either resume or release with redirect having reduced delay in accordance with embodiments of the present disclosure;

Figure 8 illustrates how overall delay is reduced for RAN paging followed by release with redirect in accordance with an embodiment of the present disclosure;

Figure 9 illustrates a process for RAN paging followed by release with redirect in accordance with an embodiment of the present disclosure;

Figure 10 illustrates how overall delay is reduced for RAN paging followed by release with redirect and suspend configuration in accordance with another embodiment of the present disclosure;

Figure 11 illustrates a process for RAN paging followed by release with redirect and suspend configuration in accordance with another embodiment of the present disclosure;

Figure 12 illustrates how overall delay is reduced for RAN paging followed by resume completion in accordance with an embodiment of the present disclosure;

Figure 13 illustrates a process for RAN paging followed by resume completion in accordance with an embodiment of the present disclosure;

Figure 14 illustrates one example procedure in which a target base station for a resume can obtain stored User Equipment (UE) context information in accordance with an embodiment of the present disclosure;

Figures 15A and 15B illustrate another embodiment of the present disclosure in which a target base station sends a resume to the UE with an anticipated UE context at target node and, in addition, path switch preparation is done early to further decrease delay;

Figures 16A and 16B illustrate the conventional solution for resume without anticipated UE context and without path switch preparation for comparison with the embodiment of Figures 15A and 15B;

Figures 17A and 17B illustrate another embodiment of the present disclosure in which a target base station sends a resume to the UE with an anticipated UE context at the target node and, in addition, path switch preparation is done early to further decrease delay;

Figure 18 is a schematic block diagram of a network node according to some embodiments of the present disclosure; Figure 19 is a schematic block diagram that illustrates a virtualized embodiment of the network node of Figure 18 according to some embodiments of the present disclosure;

Figure 20 is a schematic block diagram of the network node of Figure 18 according to some other embodiments of the present disclosure;

Figure 21 is a schematic block diagram of a UE according to some embodiments of the present disclosure; and

Figure 22 is a schematic block diagram of the UE of Figure 21 according to some other embodiments of the present disclosure.

The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure.

Radio Node: As used herein, a "radio node" is either a radio access node or a wireless communication device.

Radio Access Node: As used herein, a "radio access node" or "radio network node" or "radio access network node" is any node in a Radio Access Network (RAN) of a cellular communications network that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high-power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), a relay node, a network node that implements part of the functionality of a base station or a network node that implements a gNB Distributed Unit (gNB-DU)) or a network node that implements part of the functionality of some other type of radio access node. Core Network Node: As used herein, a "core network node" is any type of node in a core network or any node that implements a core network function. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P-GW), a Service Capability Exposure Function (SCEF), a Flome Subscriber Server (HSS), or the like. Some other examples of a core network node include a node implementing an Access and Mobility Function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), an Authentication Server Function (AUSF), a Network Slice Selection Function (NSSF), a Network Exposure Function (NEF), a Network Function (NF) Repository Function (NRF), a Policy Control Function (PCF), a Unified Data Management (UDM), or the like.

Communication Device: As used herein, a "communication device" is any type of device that has access to an access network. Some examples of a communication device include, but are not limited to: mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or Personal Computer (PC). The communication device may be a portable, hand-held, computer-comprised, or vehicle- mounted mobile device, enabled to communicate voice and/or data via a wireless or wireline connection.

Wireless Communication Device: One type of communication device is a wireless communication device, which may be any type of wireless device that has access to (i.e., is served by) a wireless network (e.g., a cellular network). Some examples of a wireless communication device include, but are not limited to: a User Equipment device (UE) in a 3GPP network, a Machine Type Communication (MTC) device, and an Internet of Things (IoT) device. Such wireless communication devices may be, or may be integrated into, a mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or PC. The wireless communication device may be a portable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data via a wireless connection.

Network Node: As used herein, a "network node" is any node that is either part of the RAN or the core network of a cellular communications network/ system. Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system.

Note that, in the description herein, reference may be made to the term "cell"; however, particularly with respect to 5G NR concepts, beams may be used instead of cells and, as such, it is important to note that the concepts described herein are equally applicable to both cells and beams.

Systems and methods are disclosed herein for reducing delays during a resume procedure in a cellular communications system (e.g., a Radio Resource Control (RRC) procedure, e.g., in a 3GPP 5G System (5GS)). In this regard, embodiments of a method performed at a source network node (e.g., a last serving gNB) for RAN paging and corresponding embodiments of a source network node are disclosed. In one embodiment, upon reception of incoming downlink data or downlink signaling for an UE in an inactive state (e.g., RRC_INACTIVE state), the source network node sends a RAN paging message (e.g., XnAP RAN PAGING message) including a UE context (e.g., UE Access Stratum (AS) context) of the UE to at least one neighboring network node (e.g., at least one of the gNBs in a configured RAN Notification Area (RNA) for the UE). In this manner, the UE context becomes known in the network node receiving the RAN paging message.

In one embodiment, the source network node sends a RAN paging message including the UE context to all neighboring network nodes (e.g., all gNBs within the configured RNA for the UE). In this manner, the UE context is thereby made known in all potential target network nodes (e.g., all potential target gNBs) before a resume request (e.g., a RRC Resume Request or RRC Resume Requestl) is received.

In another embodiment, the source network node sends the RAN paging message including the UE context only towards one or more target network nodes (e.g., one or more target gNBs in the RNA) that are known to be able to serve a resume request from the UE. The UE context is thereby known in the target network node where the resume request message (e.g., RRC Resume Request or RRC Resume Requestl message) is received.

In another embodiment, the source network node sends a RAN paging message including the UE context only towards one or more network nodes (e.g., one or more gNBs in the RNA) where the UE is more likely to camp on, e.g., according to an estimated probability. The UE context is thereby known in the target network node (e.g., the target gNB) where the resume request message (e.g., RRC Resume Request or RRC Resume Requestl message) is received.

Embodiments of a method performed at a target network node (e.g., a target gNB) for RAN paging and corresponding embodiments of a target network node are also disclosed. In one embodiment, the target network node receives a RAN paging message from a source network node (e.g., last serving gNB) including a UE context (e.g., UE AS context) of a UE. The target network node sends a RRC paging message (e.g., RRC Paging message) to the UE according to the received RAN paging message and a paging configuration of the UE. The target network node then determines whether it receives a resume request message (e.g., an RRCResumeRequest or an RRCResumeRequestl message) from the UE (i.e., if the UE responds to the RRC paging message). If the target network node determines that it has received a resume request message from the UE, the target network node performs one or more resume procedure related actions based on the UE context contained in the RAN paging message received from the source network node.

For example, in one embodiment, the target network node determines whether the target network node is going to release and redirect a corresponding connection (e.g., RRC connection) of the UE to another frequency, Radio Access Technology (RAT), or cell where inactive state is not supported. In one embodiment, if the target network node determines that it is going to release and redirect the connection of the UE to another frequency, RAT, or cell where inactive state is not supported, the target network node prepares a release message (e.g., an RRCRelease message) that is built based on the UE context received in the RAN paging message from the source network node. For example, in one embodiment, the target network node encrypts and integrity protects the release message using new security keys derived based on a security context in the UE Context (e.g., KgNB (i.e., a security key used in NG-RNA, see, e.g., TS 33.501 (Key for NG-RAN)), Next Flop Chaining Count (NCC), etc.), skips the triggering of a path switch as the release message does not need to include a suspend configuration, and/or releases the UE context received in the RAN paging message.

In one embodiment, the target network node determines that it is going to release and redirect the connection of the UE to another frequency supporting inactive state (i.e., where the UE is able to resume), and the target network node prepares a release message (e.g., an RRCRelease message) that is built based on the UE context received in the RAN paging message from the source network node. For example, the target network node may encrypt and integrity protect the release message using new security keys derived based on the security context in the UE context (e.g., KgNB, NCC, etc.), and include in the release message the redirectedCarrierlnfo Information Element (IE) to indicate the target frequency and the suspendConfig IE, including the NCC retrieved via the path switch and possibly using a delta signaling on corresponding configurations the UE has stored to be used as part of the resume procedure on the target frequency.

In one embodiment, if the target network node determines that it is going to resume the connection of the UE (e.g., if the service(s) being requested by the UE is(are) supported by the target network node and/or the frequency or cell and the UE is transitioned to connected state (e.g., RRC CONNECTED), the target network node prepares a resume message (e.g., an RRCResume message) that is built based on the UE context received in the RAN paging message from the source network node. For example, the target radio node encrypts and integrity protects the resume message using new security keys derived based on the security context in the UE context (e.g., KgNB, NCC, etc.).

Note that after successful transition from the inactive state to the connected state, the target network node performs a path switch procedure (e.g., with an associated AMF), e.g., according to the legacy path switch procedure. This applies for the following sequence: RRC Resume Request -> RRC Resume -> RRC Resume Complete (see, e.g., Figure 12).

In one embodiment, in case the target network node opts for sending a release message with redirect to a frequency, cell, or RAT where the UE cannot be configured as inactive, the steps 106-112 shown in Figure 1 can be avoided and the overall delay is reduced.

In case the target network node opts for sending a release message with redirect to a frequency, cell, or RAT where the UE can be configured as inactive, steps 106 and 108 shown in Figure 1 can be avoided and the overall delay is reduced. In case the target network node opts for continuing the resume procedure (e.g., RRC Connection Resume procedure) and path switch preparation is done, steps 206 and 208 shown in Figure 2 can be avoided and the overall delay is reduced.

In addition, some other embodiments of a method for RAN paging performed at a source network node (e.g., a last serving gNB), a target network node (e.g., a target gNB), and a core network (e.g., a 5G Core (5GC) or Evolved Packet Core (EPC)). The last serving source network node sends a request to prepare a path switch (e.g., in a new message, e.g. "PATH SWITCH PREPARATION REQUEST") towards a core network node or function (e.g., an AMF) indicating a list of potential target network nodes C'TargetList" or "gNBTargetList") per UE where the UE may resume. In other words, the list of potential target network nodes is a list of network nodes where the UE is likely to resume. The source network node also provides a target marker mapped to a list of potential target network node(s) to both the core network node/function and the target network nodes together with the UE context. The core network/function prepares the paths towards the list of potential target network nodes (e.g., gNB-ri, gNBT2, ..., gNBTi\i). As soon as the actual target network node receives a resume request message (e.g., RRCResumeRequest or RRCResumeRequestl message) from the UE, the actual target network node first verifies an identity of the UE and then it responds to the UE with a resume message (e.g., an RRCResume message). Note that the UE Context has already been received by the actual target network node from the source network node via a message and is available at the actual target network node. Downlink data flow can also start faster than in the existing solution because resources are already allocated towards the actual target network node and the path (user plane) is ready to be switched when the UE contacts the network. As can be seen in Figures 15A and 15B (described below in detail), as soon as the UE resumes in the target network node, an indication, e.g. a ping message conveying Target Marker (target network node), is sent to a corresponding user plane function (e.g., UPF) through user plane and the path switch execution is triggered towards the target network node matching the Target Marker (target network node). Upon reception of the indication from the target network node, downlink data can flow to the UE. The list of other sessions established for the remaining potential target network nodes advertised in the path switch preparation are released. Embodiments of the present disclosure may provide one or more technical advantages. For example, in the context of a 5GS as an example, embodiments disclosed herein decrease the delay to serve an RRC_INACTIVE UE when RNA covers multiple gNBs and XnAP RAN PAGING is needed to reach the UE in case of downlink data or downlink signaling towards the UE. The XnAP RAN PAGING message is modified to accommodate the UE context and avoid (or alternatively to reduce) the need for XnAP Retrieve UE Context and Next Generation (NG) Access Point (AP) Path Switch Request procedures.

As another example, again in the context of a 5GS as an example, embodiments disclosed herein may allow a faster resume for UEs in RRC_INACTIVE states compared to the existing solution. In addition, the performance of RRC_INACTIVE UEs is improved by means of an earlier reception of downlink data or downlink signaling for the UE or a quicker trigger of release with redirect to other NR/Evolved Universal Terrestrial Radio Access Network (E-UTRAN) frequencies, depending upon the decision of target gNB for resume.

Figure 4 illustrates one example of a cellular communications system 400 in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications system 400 is a 5GS including a NG-RAN and a 5GC. In this example, the NG-RAN includes base stations 402-1 and 402-2, which in the 5GS are referred to as gNBs (i.e., NR base stations) or ng-eNBs (i.e., LTE RAN nodes connected to the 5GC), controlling corresponding (macro) cells 404-1 and 404-2. The base stations 402-1 and 402-2 are generally referred to herein collectively as base stations 402 and individually as base station 402. Likewise, the (macro) cells 404-1 and 404-2 are generally referred to herein collectively as (macro) cells 404 and individually as (macro) cell 404. The RAN may also include a number of low power nodes 406-1 through 406-4 controlling corresponding small cells 408-1 through 408-4. The low power nodes 406-1 through 406-4 can be small base stations (such as pico or femto base stations) or Remote Radio Heads (RRHs), or the like. Notably, while not illustrated, one or more of the small cells 408-1 through 408-4 may alternatively be provided by the base stations 402. The low power nodes 406-1 through 406-4 are generally referred to herein collectively as low power nodes 406 and individually as low power node 406. Likewise, the small cells 408-1 through 408-4 are generally referred to herein collectively as small cells 408 and individually as small cell 408. The cellular communications system 400 also includes a core network 410, which in the 5GS is referred to as the 5GC. The base stations 402 (and optionally the low power nodes 406) are connected to the core network 410.

The base stations 402 and the low power nodes 406 provide service to wireless communication devices 412-1 through 412-5 in the corresponding cells 404 and 408. The wireless communication devices 412-1 through 412-5 are generally referred to herein collectively as wireless communication devices 412 and individually as wireless communication device 412. In the following description, the wireless communication devices 412 are oftentimes UEs, but the present disclosure is not limited thereto. As such, the wireless communication devices 412 are sometimes referred to herein as UEs 412.

Figure 5 illustrates a wireless communication system represented as a 5G network architecture composed of core NFs, where interaction between any two NFs is represented by a point-to-point reference point/interface. Figure 5 can be viewed as one particular implementation of the system 400 of Figure 4.

Seen from the access side the 5G network architecture shown in Figure 5 comprises a plurality of UEs 412 connected to either a RAN 402 or an Access Network (AN) as well as an AMF 500. Typically, the R(AN) 402 comprises base stations, e.g. such as eNBs or gNBs or similar. Seen from the core network side, the 5G core NFs shown in Figure 5 include a NSSF 502, an AUSF 504, a UDM 506, the AMF 500, a SMF 508, a PCF 510, and an Application Function (AF) 512.

Reference point representations of the 5G network architecture are used to develop detailed call flows in the normative standardization. The N1 reference point is defined to carry signaling between the UE 412 and AMF 500. The reference points for connecting between the AN 402 and AMF 500 and between the AN 402 and UPF 514 are defined as N2 and N3, respectively. There is a reference point, Nil, between the AMF 500 and SMF 508, which implies that the SMF 508 is at least partly controlled by the AMF 500. N4 is used by the SMF 508 and UPF 514 so that the UPF 514 can be set using the control signal generated by the SMF 508, and the UPF 514 can report its state to the SMF 508. N9 is the reference point for the connection between different UPFs 514, and N14 is the reference point connecting between different AMFs 500, respectively. N15 and N7 are defined since the PCF 510 applies policy to the AMF 500 and SMF 508, respectively. N12 is required for the AMF 500 to perform authentication of the UE 412. N8 and N10 are defined because the subscription data of the UE 412 is required for the AMF 500 and SMF 508.

The 5GC network aims at separating user plane and control plane. The user plane carries user traffic while the control plane carries signaling in the network. In Figure 5, the UPF 514 is in the user plane and all other NFs, i.e., the AMF 500, SMF 508, PCF 510, AF 512, NSSF 502, AUSF 504, and UDM 506, are in the control plane. Separating the user and control planes guarantees each plane resource to be scaled independently. It also allows UPFs to be deployed separately from control plane functions in a distributed fashion. In this architecture, UPFs may be deployed very close to UEs to shorten the Round Trip Time (RTT) between UEs and data network for some applications requiring low latency.

The core 5G network architecture is composed of modularized functions. For example, the AMF 500 and SMF 508 are independent functions in the control plane. Separated AMF 500 and SMF 508 allow independent evolution and scaling. Other control plane functions like the PCF 510 and AUSF 504 can be separated as shown in Figure 5. Modularized function design enables the 5GC network to support various services flexibly.

Each NF interacts with another NF directly. It is possible to use intermediate functions to route messages from one NF to another NF. In the control plane, a set of interactions between two NFs is defined as service so that its reuse is possible. This service enables support for modularity. The user plane supports interactions such as forwarding operations between different UPFs.

Figure 6 illustrates a 5G network architecture using service-based interfaces between the NFs in the control plane, instead of the point-to-point reference points/interfaces used in the 5G network architecture of Figure 5. Flowever, the NFs described above with reference to Figure 5 correspond to the NFs shown in Figure 6. The service(s) etc. that a NF provides to other authorized NFs can be exposed to the authorized NFs through the service-based interface. In Figure 6 the service based interfaces are indicated by the letter "N" followed by the name of the NF, e.g. Namf for the service based interface of the AMF 500 and Nsmf for the service based interface of the SMF 508, etc. The NEF 600 and the NRF 602 in Figure 6 are not shown in Figure 5 discussed above. Flowever, it should be clarified that all NFs depicted in Figure 5 can interact with the NEF 600 and the NRF 602 of Figure 6 as necessary, though not explicitly indicated in Figure 5.

Some properties of the NFs shown in Figures 5 and 6 may be described in the following manner. The AMF 500 provides UE-based authentication, authorization, mobility management, etc. A UE 412 even using multiple access technologies is basically connected to a single AMF 500 because the AMF 500 is independent of the access technologies. The SMF 508 is responsible for session management and allocates Internet Protocol (IP) addresses to UEs. It also selects and controls the UPF 514 for data transfer. If a UE 412 has multiple sessions, different SMFs 508 may be allocated to each session to manage them individually and possibly provide different functionalities per session. The AF 512 provides information on the packet flow to the PCF 510 responsible for policy control in order to support Quality of Service (QoS). Based on the information, the PCF 510 determines policies about mobility and session management to make the AMF 500 and SMF 508 operate properly. The AUSF 504 supports authentication function for UEs or similar and thus stores data for authentication of UEs or similar while the UDM 506 stores subscription data of the UE 412. The Data Network (DN), not part of the 5GC network, provides Internet access or operator services and similar.

An NF may be implemented either as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g., a cloud infrastructure.

Now, a description of some example embodiments of the present disclosure will be provided. Embodiments described herein provide a faster resume procedure (e.g., RRC resume procedure) procedure for UEs in inactive state (e.g., RRC_INACTIVE UEs), e.g. in case of RNA covering multiple radio access nodes (e.g., multiple gNBs) when RAN paging (e.g., XnAP RAN PAGING) is needed to reach the UE 412. In this regard, Figure 7 illustrates the operation of a UE 412, a first base station 402-S, and one or more additional radio access nodes 402-T1 through 402-TN for RAN paging that provides a faster resume compared to conventional solutions, in accordance with embodiments of the present disclosure. Notably, the first base station 402-S is a last serving radio access node of the UE 412 and, as such, the first base station 402-S is also referred to herein as the "last serving base station 402-S," a "source network node 402-S," or a "source base station 402-S." The one or more additional radio access nodes 402-T1 through 402-TN are (potential) target radio access nodes for resuming a connection of the UE 412 and, as such, the one or more additional radio access nodes 402-T1 through 402-TN are also referred to herein as (potential) "target radio access nodes 402-T1 through 402-TN," (potential) "target radio access nodes 402-T1 through 402-TN," or (potential) "target network nodes 402-T1 through 402-TN." Also note that optional steps and aspects of the process of Figure 7 are represented by dashed lines/boxes.

As illustrated, upon reception of incoming downlink data or downlink signaling for the UE 412, which is in an inactive state (e.g., RRC_INACTIVE state), the last serving base station 402-S sends a RAN paging message (e.g., XnAP RAN PAGING message) including a UE context of the UE 412 to the one or more (potential) target radio access nodes 402-T1 through 402-TN (steps 700-1 through 700-N). The one or more (potential) target radio access nodes 402-T1 through 402-TN store the received UE context (steps 702-1 through 702-N). For example, the one or more (potential) target radio access nodes 402-T1 through 402-TN include at least one of the gNBs in a configured RNA for the UE 412. In this manner, the UE context becomes known in the one or more (potential) target radio access nodes 402-T1 through 402-TN upon receiving the RAN paging message from the last serving base station 402-S. The UE context is all or some subset of the information contained in a UE AS context of the UE 412. In one embodiment, the UE context includes the information needed in the legacy solution in the source gNB to perform the security checks when an XnAP "Retrieve UE Context" procedure is attempted. This includes the Inactive Radio Network Temporary Identifier (I-RNTI), the cell identity of the source primary cell used by the UE before entering inactive state, the UE 5G AS security context containing the current K _RR ant ,the K _Q NB or the Next Flop (NFI). The UE context further includes at least part of the information that the source gNB returns to the target gNB in a legacy solution as part of the XnAP "RETRIEVE UE CONTEXT RESPONSE", such as: the UE 5G security capabilities, the User Plane (UP) security policy, the UP security activation status with the corresponding Protocol Data Unit (PDU) session Identity(s) (ID(s)), and the ciphering and integrity algorithms used by the UE with the source cell. For example, in one embodiment, the UE context contained in the RAN paging message includes: one or more encryption or security keys (e.g., KgNB, K _RRC mt), a Robust Fleader Compression (ROFIC) state of the UE 412, a Cell Radio Network Temporary Identifier (C-RNTI) used for the UE 412 in a source Primary Cell (PCell) of the UE 412, a cell identity and a physical cell identity of the source PCell of the UE 412, information regarding one or more RAT related UE capabilities of the UE 412, and/or other parameters (e.g., all other parameters) configured for the UE 412 except for the ones within ReconfigurationWithSync and servingCellConfigCommonSIB).

In one embodiment, the last serving base station 402-S sends a RAN paging message including the UE context to all neighboring network nodes (e.g., all gNBs within the configured RNA for the UE 412). In other words, the one or more (potential) target radio access nodes 402-T1 through 402-TN include all neighboring radio access nodes (e.g., all gNBs within the configured RNA for the UE 412). In this manner, the UE context is made known in all potential target radio access node(s) 402-T1 through 402-TN (e.g., all potential target gNBs) before a resume request (e.g., a RRC Resume Request or RRC Resume Requestl) is received from the UE 412.

In another embodiment, the one or more (potential) target radio access nodes 402-T1 through 402-TN to which the last serving base station 402-S sends the RAN paging message including the UE context are some subset of all known (e.g., neighboring) radio access nodes (e.g., one or more target gNBs in the configured RNA of the UE 412) that are known to be able to serve a resume request from the UE 412. The UE context is thereby known in the one or more (potential) target radio access nodes 402-T1 through 402-TN where the resume request message (e.g., RRC Resume Request or RRC Resume Requestl message) may be received.

In another embodiment, the one or more (potential) target radio access nodes 402-T1 through 402-TN to which the last serving base station 402-S sends the RAN paging message including the UE context are some subset of all known radio access nodes (e.g., one or more gNBs in the configured RNA of the UE 412) where the UE is likely to camp on, e.g., according to an estimated probability. The UE context is thereby known in the one or more (potential) target radio access nodes 402-T1 through 402-TN where the resume request message (e.g., RRC Resume Request or RRC Resume Requestl message) may be received.

At the one or more (potential) target radio access nodes 402-T1 through 402-TN, the one or more (potential) target radio access nodes 402-T1 through 402-TN receive and store the RAN paging message including the UE context of the UE 412 (steps 700-1 through 700-N and steps 702-1 through 702-N). Responsive to receiving the RAN paging message from the last serving base station 402-S, each of the one or more (potential) target radio access nodes 402-T1 through 402-TN sends a RRC paging message (e.g., RRC Paging message) to the UE 412 according to the received RAN paging message and a paging configuration of the UE 412 (steps 704-1 through 704-N). Note that, in this example, the UE 412 receives the RRC paging message from the (potential) target base station 402-T1, but not from the (potential) target base station 402-TN.

The UE 412 sends a resume request message to, in this example, the (potential) target base station 402-T1 (step 706). In this example, the (potential) target base station 402-T1 receives the resume request message from the UE 412 and, as such, the (potential) target base station 402-T1 becomes the actual target base station 402-T1 for the resume. In response to receiving the resume request from the UE 412, the target base station 402-T1 obtains the stored UE context information for the UE 412 (step 708) and performs one or more resume or release related procedure actions based on the UE context contained in the RAN paging message received from the last serving base station 402-S (step 710).

In regard to the one or more actions performed in step 710, in one embodiment, the target radio access node 402-T1 has determined that it has received a resume request from the UE 412 and, in response, determines that it is going to release and redirect a corresponding connection (e.g., RRC connection) of the UE 412 to another frequency, RAT, or cell where inactive state is not supported. In one embodiment, if the target radio access node 402-T1 determines that it is going to release and redirect the connection of the UE 412 to another frequency, RAT, or cell where inactive state is not supported, the target radio access node 402-T1 prepares a release message (e.g., an RRCRelease message) that is built based on the UE context received in the RAN paging message from the last serving base station 402-S. For example, in one embodiment, the target radio access node 402-T1 encrypts and integrity protects a release message using new security keys derived based on a security context in the UE Context (e.g., KgNB, NCC, etc.), skips the triggering of a path switch as the release message does not need to include a suspend configuration, and/or release the UE context received in the RAN paging message.

In one embodiment, if the target radio access node 402-T1 determines that it is going to release and redirect the connection of the UE 412 to another frequency supporting inactive state (i.e., where the UE 412 is able to resume), the target radio access node 402-T1 prepares a release message (e.g., an RRCRelease message) that is built based on the UE context received in the RAN paging message from the last serving base station 402-S. For example, the target radio access node 402-T1 may encrypt and integrity protect the release message using new security keys derived based on the security context in the UE context (e.g., KgNB, NCC, etc.), include in the release message the redirectedCarrierlnfo IE to indicate the target frequency and the suspendConfig IE, including the NCC retrieved via the path switch and possibly using a delta signaling on corresponding configurations the UE 412 has stored to be used as part of the resume procedure on the target frequency. The target radio access node 402-T1 sends the release message to the last serving base station 402-S.

In one embodiment, if the target radio access node 402-T1 determines that it is going to resume the connection of the UE 412 (e.g., if the service(s) being requested by the UE is(are) supported by the target network node and/or the frequency or cell and the UE is transitioned to connected state (e.g., RRC CONNECTED), the target radio access node 402-T1 prepares a resume message (e.g., an RRCResume message) that is built based on the UE context received in the RAN paging message from the last serving base station 402-S. For example, the target radio access node 402-T1 encrypts and integrity protects the resume message using new security keys derived based on the security context in the UE context (e.g., KgNB, NCC, etc.).

In one embodiment, in case the target radio access node 402-T1 opts for sending a release message with redirect to a frequency, cell, or RAT where the UE cannot be configured as inactive, steps 106-112 shown in Figure 1 can be avoided and the overall delay is reduced, as illustrated in the example of Figure 8. An example of resulting procedure with RAN paging followed by faster release and redirect for 5GS is illustrated in Figure 9. In the example of Figure 9, the last serving base station 402-S is a last serving gNB, and the target base station 402-T1 is a target gNB. As illustrated, the last serving gNB sends an XnAP RAN PAGING message including the UE context of the UE 412 to the target gNB (step 900). The target gNB sends an RRC paging message to the UE 412 (step 902). The UE responds to the target gNB with an RRCResumeRequest or RRCRequestRequestl message (step 904). Since the target gNB already has the UE context of the UE 412 (as a result of receiving and storing the UE context in step 900), the target gNB does not need to retrieve the UE context from the last serving gNB after receiving the RRCResumeRequest or RRCResumeRequestl message from the UE 412. The target gNB then determines that it is to send a release message with redirect to a frequency, RAT, or cell where the UE 412 is not able to be inactive, and the target gNB sends an RRCRelease message with redirect to the UE 412 (step 906). In addition, the target gNB sends an XnAP UE CONTEXT RELEASE message to the last serving gNB (step 908).

In case the target radio access node 402-T1 opts for sending a release message with a redirect to a frequency, cell, or RAT where the UE can be configured as inactive, steps 106 and 108 of Figure 1 can be avoided as shown in Figure 10. An example of resulting procedure with RAN paging followed by faster release and redirect for 5GS is illustrated in Figure 11 (also including a suspend configuration). In the example of Figure 11, the last serving base station 402-S is a last serving gNB, and the target base station 402-T1 is a target gNB. As illustrated, the last serving gNB sends an XnAP RAN PAGING message including the UE context of the UE 412 to the target gNB (step 1100). The target gNB sends an RRC paging message to the UE 412 (step 1102). The UE responds to the target gNB with an RRCResumeRequest or RRCRequestRequestl message (step 1104). Since the target gNB already has the UE context of the UE 412 (as a result of receiving and storing the UE context in step 1100), the target gNB does not need to retrieve the UE context from the last serving gNB after receiving the RRCResumeRequest or RRCResumeRequestl message from the UE 412. The target gNB then determines that it is to send a release message with redirect to a frequency, RAT, or cell where the UE is able to be inactive. In response thereto, the target gNB sends a path switch request to an associated AMF (step 1106), receives a path switch request acknowledge from the AMF (step 1108), and sends an RRCRelease message with redirect to the UE 412 (step 1110). Here, the RRCRelease message includes a redirectedCarrierlnfo IE and a suspendConfig IE. In addition, the target gNB sends an XnAP UE context release message to the last serving gNB (step 1112).

In case the target radio access nodes 402-T1 opts for continuing the resume procedure (e.g., the RRC Connection Resume procedure) and no path switch preparation is done, steps 206 and 208 shown in Figure 2 can be avoided and the overall delay is reduced, as illustrated in the example of Figure 12. An example of the resulting procedure with RAN paging followed by faster successful RRC resume without path switch preparation for 5GS is illustrated in Figure 13. In the example of Figure 13, the last serving base station 402-S is a last serving gNB, and the target base station 402-T1 is a target gNB. As illustrated, the last serving gNB sends an XnAP RAN PAGING message including the UE context of the UE 412 to the target gNB (step 1300). The target gNB sends an RRC paging message to the UE 412 (step 1302). The UE responds to the target gNB with an RRCResumeRequest or RRCRequestRequestl message (step 1304). Since the target gNB already has the UE context of the UE 412 (as a result of receiving and storing the UE context in step 900), the target gNB does not need to retrieve the UE context from the last serving gNB after receiving the RRCResumeRequest or RRCResumeRequestl message from the UE 412. The target gNB then determines that it is to resume the connection of the UE 412 (without path switch preparation), and sends an RRCResume message to the UE 412 (step 1306).

The UE 412 sends an RRCResumeComplete message back to the target gNB (step 1308). In addition, the target gNB sends an NGAP PATH SWITCH REQUEST to the appropriate AMF (step 1310), receives an NGAP PATH SWITCH REQUEST ACKNOWLEDGE from the AMF (step 1312), and sends an XnAP UE CONTEXT RELEASE message to the last serving gNB (step 1314).

In case the target radio access node(s) 402-T1 opts for continuing the resume procedure (e.g., RRC Connection Resume procedure) and path switch preparation is done, steps 206 and 208 shown in Figure 2 can be avoided and the path switch procedure can be executed in parallel with the completion of the resume. The resume procedure delay is reduced and the overall time to serve the UE is reduced. Note that a more detailed description of the resume procedure with path switch preparation is provided below, e.g., in association with the description of Figures 15A and 15B.

In one example embodiment, the RAN paging message received by the target radio access node(s) 402-T1 or target gNB from the last serving base station 402-S or last serving gNB is an extended version of the XnAP RAN PAGING message. Further, in one embodiment, the extended version of XnAP RAN PAGING message contains relevant UE context information of the RRC_INACTIVE UE (i.e., UE 412). For example, this relevant UE context information includes at least the I-RNTI and at least (but not limited to) the current KgNB and K _RRCi nt keys, the ROHC state, the C-RNTI used in the source PCell, the cellldentity and the physical cell identity of the source PCell, the RAT related UE Capability, and all other parameters configured except for the ones within ReconfigurationWithSync and servingCellConfigCommonSIB. At reception of the extended XnAP RAN PAGING message, a potential target gNB for resuming the connection of the UE 412 becomes aware of the identity of the UE context (e.g., via I-RNTI) and the KgN _B /NH included in current UE 5G AS security context. In one embodiment, the target gNB receiving the RRCResumeRequest uses the ResumeMAC-I/shortResumeMAC-I together with the Physical Cell Identity (PCI) and the target Absolute Radio Frequency Channel Number (ARFCN) -DL used for the resume attempt to validate the request and derive the new security key KNG-RAN* and the NCC associated to the KNG-RAN*.

In one embodiment, the modified XnAP RAN PAGING message is sent to all the potential target gNBs in the configured RNA of the UE 412. In another embodiment, the last serving gNB sends the modified XnAP RAN PAGING only to a subset of all the potential target gNBs in the configured RNA of the UE 412. The selection of the target gNBs can be based on one or more criteria. A non-exhaustive list of some examples of the criteria that may be used for this selection is:

• service preference,

• service capability,

• configuration management data, and/or

• probability that the UE is camping on a gNB.

Notably, a base station 402 (e.g., a gNB) as described herein can play two different roles with respect to the ownership of a UE Context. In particular, either the base station 402 stores the UE context for a UE(s) 412 that it releases to inactive state (i.e., the base station 402 operates as a last serving radio access node or last serving gNB) or the base station 402 stores the UE context for a UE(s) 412 that another base station 402 released to inactive state (i.e., the base station 402 operates as a potential target radio access node or potential target gNB). One base station 402 can play the two roles at the same time, and a UE context can be classified according to the role of the base station 402. A UE context is classified as "owned" by a base station 402 when the base station 402 is the last serving node of the respective UE 412. A UE Context is classified as "hosted" by a base station 402 when the base station 402 receives the UE context from another node via a respective RAN paging message. The content of a "hosted" UE context can contain all or a subset of the information contained in a corresponding "owned" UE context. This classification of the UE Contexts stored in one base station 402 can be used to optimize the retrieval of a UE context when an RRCResumeRequest/Requestl is received.

In some embodiments, when improving the release with redirect scenario, the target radio access node(s) 402-T1 or target gNB searches a set of stored UE contexts for a matching UE context for the UE 412 from which it has received a resume request. The set of stored UE contexts includes UE contexts received from other network nodes within corresponding RAN paging messages in accordance with the embodiments described herein. UE context information can be hosted, owned, or stored hosted UE Context in another radio access node. Note that "stored hosted" UE Context refers to a UE Context that the target radio access node(s) 402-T1 receives from another node (i.e., is hosted) and is stored by the target radio access node(s) 402-T1. In one embodiment, upon receiving a resume request from the UE 412, the target radio access node(s) 402-T1 searches for the UE context of the UE 412 as follows. Note that, in this example, the resume request includes an I-RNTI of the UE 412, where the I-RNTI includes a node identifier that identifies a last serving gNB of the UE 412. In addition, the UE context received by the target radio access node 402-T1 in the RAN paging message from the last serving radio access node 402-S includes the I-RNTI of the UE 412. Thus, the search for the UE context of the UE 412 from which the resume request is received can be as follows:

1. The target radio access node 402-T1 checks whether the node identifier in the I- RNTI included in the resume request matches the node identifier of the target radio access node 402-T1. If so, the target radio access node 402-T1 is also the last serving radio access node 402-S, in which case the embodiments disclosed herein do not apply and the target radio access node 402-T1 has the UE context as a result of it being the last serving radio access node 402-S of the UE 412.

2. (If there is no match in step 1), the target radio access node 402-T1 checks whether any UE context information received in the corresponding XnAP RAN PAGING message is stored for the UE 412, e.g., based on the I-RNTI of the UE 412. If so, this stored UE context information is retrieved from storage and used by the target radio access node 402-T1 as described herein.

3. (If there is no match in step 2), the target radio access node 402-T1 retrieves the UE context of the UE 412 from another node where the UE context is stored (e.g., from the last serving radio access node 402-S in the case where the corresponding RAN paging message did not include UE context information for the UE 412).

If there are sufficient resources available, the target radio access node 402-T1 may perform steps 1-3 above in parallel. This is expensive, since at the time the UE 412 resumes at the target radio access node 402-T1, only the information provided up to and including the resume message (e.g., the RRCResumeRequest or RRCResumeRequestl message) has been received. This only provides limited information about the urgency for the access. For some special cases such as high priority access and emergency call, this could be addressed. For network initiated signaling, the radio access node cannot understand the urgency for the access. Figure 14 shows how this could be improved. As illustrated in Figure 14, the latest serving base station 402-S (denoted in Figure 14 as"gNBs") initiates the RAN paging procedure to the target base station 402-T1 (denoted in Figure 14 as "gNB-r") and provides any information needed for the gNB _T to take the desired action as described herein (step 1400). The gNB _T decides to store the information received in 1400 (step 1402). The gNB _T pages the UE 412 and provides an indicator (Context ind) that indicates that the UE context corresponding to this page is stored in the gNB _T (step 1404). The UE 412 responds to the page in the RRCResumeRequest message and includes the indicator Context ind (step 1406). If the received RRCResumeRequest message contains the Context ind, the corresponding stored UE Context is obtained from storage (steps 1408 and 1410). The gNB _T releases the UE 412 incorporating any information needed as explained herein (e.g. release with redirect) (step 1412). From Figure 14, it can be seen that the gNB _T knows already when it receives the RRC Resume Request message if any UE related context information is stored in the node. If no such information is stored, the gNB _T does not perform step 1408, which reduces latency and/or signaling load.

Figures 15A and 15B illustrate another embodiment of the present disclosure in which the target base station 402-T1 sends a release with redirect to the UE 412 and, in addition, path switch preparation is done early to further decrease delay. The example embodiment of Figures 15A and 15B is for 5G and, as such, the last serving base station 402-S is denoted as a source gNB 402-S and the target base station 402-T1 is denoted as a target gNB 402-Tl. Flowever, this embodiment is not limited to 5G. The last serving gNB 402-S sends a request to prepare a path switch (e.g., in a new message, e.g. "PATH SWITCH PREPARATION REQUEST") towards the AMF 500 (step 1500). This request indicates a list of potential target gNBs "gNBTargetList" (gNB-ri, gNB _T 2, gNB™) where the UE 412 may resume, i.e., the list of gNBs where the UE 412 is most likely to resume. Note that the list of potential target gNBs is UE- specific. The last serving gNB 402-S also provides a TargetMarker (gNB-ri, gNB _T 2,..., gNB™) that is mapped to the list of potential target gNBs to both the AMF 500 and the potential target gNBs together with the UE Context in the RAN paging message (step 1502). The AMF 500 triggers the preparation of a path towards the list of potential target gNBs (gNB-ri, gNBT2, ..., gNB™) (steps 1504-1514).

The target gNB 402-T1 sends a RRC paging message to the UE 412 (step 1516). As soon as the target gNB 402-T1 receives the

RRC:RRCResumeRequest/RRCResumeRequestl message (step 1518), the target gNB 402-T1 first verifies the UE identity (step 1520) and then it sends a path switch execution indication to the appropriate UPF(s) (step 1522) and responds to the UE 412 with an RRC:RRCResume message (step 1524). Note that the UE Context has already been received from the last serving gNB 402-S via the XnAP RAN PAGING message in step 1502 and is available at the target gNB 402-T1. Downlink data flow can also start faster than in the existing solution because resources are already allocated towards the target gNB 402-T1 and the path (user plane) is ready to be switched when the UE 412 contacts the network. As can be seen in Figure 15A, as soon as the UE 412 resumes in the target gNB 402-T1, the path switch execution indication, e.g. a ping message conveying Target Marker (gNB-ri), is sent to the UPF 514 through the user plane, and the path switch execution is triggered towards the target gNB 402-T1 matching the Target Marker (gNB-ri) (again see step 1522). In response to the path switch execution indication, the path switch is completed (steps 1526, 1528, 1532, and 1534). The list of other sessions established for the remaining gNBs advertised in the path switch preparation for the other gNBs in the Target Marker (gNB _T 2, gNB _T 3, ..., gNB™) are released (step 1530). Upon reception of the indication from the target gNB 402-T1 at the UPF(s), downlink data can flow to the UE 412 once the UE 412 sends a resume complete message to the target gNB 402-T1 (steps 1536 and 1538). In regard to Figures 15A and 15B, note that the steps in Block A can be executed in parallel with the steps in Block B. The steps in Blocks B, C, and D can be executed in parallel. The steps in Block C are executed after the steps in Block A.

Figures 16A and 16B illustrate the existing solution in 3GPP TS 23.502 for comparison to the proposed solution of Figures 15A and 15B. The details of the steps are not described here. It is enough to point out that in this existing solution, the path switch is not initiated until after the target gNB receives the resume request from the UE. As such, it can be seen that the proposed solution of Figures 15A and 15B provide a substantial reduction in the delay between the target gNB receiving the resume request and sending the resume message to the UE.

In another embodiment, either the SMF 508 or AMF 500 steers the decision to switch the user plane towards the prepared path and the release of the remaining prepared sessions. Upon reception of an indication from the target gNB 402-T1 through the user plane from the target gNB 402-T1, the UPF 514 reports the Target Marker (gNB-ri) to the SMF 508 via the N4 Session Report message. The SMF 508 triggers the UPF 514 to switch to the reported prepared path labeled as Target Marker (gNB-ri) via the N4 Session Report Acknowledgement (ACK) message.

In another embodiment, the target gNB 402-T1 provides the Target marker (gNB-ri) through the control plane to the AMF 500 followed by the SMF 508 to the UPF 514. The UPF 514 triggers the switch to the already prepared path towards the target gNB 402-T1 labeled as Target Marker (gNB-ri). The UPF 514 also triggers the release of the list of remaining prepared sessions labeled as Target Marker (gNB _T 2, gNB _T 3, ..., gNB™) via N4 Session Modification Request message. The proposed solution in this embodiment is depicted in Figures 17A and 17B.

As illustrated in Figures 17A and 17B, the last serving gNB 402-S sends a request to prepare a path switch (e.g., in a new message, e.g. "PATFI SWITCFI PREPARATION REQUEST") towards the AMF 500 (step 1700). This request indicates a list of potential target gNBs "gNBTargetList" (gNB-ri, gNB _T 2, ..., gNB™) where the UE 412 may resume, i.e., the list of gNBs where the UE 412 is most likely to resume. Note that the list of potential target gNBs is UE-specific. The last serving gNB 402-S also provides a TargetMarker (gNB-ri, gNB _T 2,..., gNB™) that is mapped to the list of potential target gNBs to both the AMF 500 and the potential target gNBs together with the UE Context in the RAN paging message (step 1702). The AMF 500 triggers the preparation of a path towards the list of potential target gNBs (gNB-ri, gNBT2, ..., gNBTi\i) (steps 1704- 1714).

The target gNB 402-T1 sends a RRC paging message to the UE 412 (step 1716). As soon as the target gNB 402-T1 receives the

RRC:RRCResumeRequest/RRCResumeRequestl message (step 1718), the target gNB 402-T1 first verifies the UE identity (step 1720) and then it sends a path switch execution indication to the AMF 500 (step 1722) and responds to the UE 412 with an RRC:RRCResume message (step 1724). Note that the UE Context has already been received from the last serving gNB 402-S via the XnAP: RAN PAGING message in step 1702 and is available at the target gNB 402-T1. As can be seen in Figure 17A, as soon as the UE 412 resumes in the target gNB 402-T1, the path switch execution indication, e.g. a ping message conveying Target Marker (gNB-ri), is sent to the AMF 500, and the AMF 500 forwards the path switch execution to the SMF 508 (step 1726). The SMF 508 then sends an NR session modification request to the UPF 514, where this request includes the Target Marker (gNB-ri) (step 1728). In this manner, the path switch is triggered towards the target gNB 402-T1 matching the Target Marker (gNB-ri). The UPF 514 sends a N4 Session Modification Response to the SMF 508 (step 1730) and sends an end marker message to the last serving gNB 402-S (step 1732), which then forwards data to the target gNB 402-T1 (step 1734). In addition, the SMF 508 sends a session release request to the UPF(s) 514 for the list of other sessions established for the remaining gNBs advertised in the path switch preparation for the other gNBs in the Target Marker (gNBT2, gNBT3, ..., gNBTi\i) (step 1736). The UPF(s) 514 then releases these other sessions and sends a response to the SMF 508 (step 1738). Downlink data flow (1740) can also start faster than in the existing solution because resources are already allocated towards the target gNB 402-T1 and the path (user plane) is ready to be switched when the UE 412 contacts the network. Actual data can ready the UE 412 only after the target gNB 402-T1 receives an RRC Resume Complete from the UE 412 (step 1742).

One example implementation of the RAN paging message sent from the last serving base station 402-S to the one or more (potential) target radio access nodes 402-T1 through 402-TN in the 3GPP specifications is as follows (with new aspects in bold underlined text). XnAP RAN PAGING

This message is sent by the NG-RAN nodei to NG-RAN node2 to page a UE. Direction: NG-RAN nodei ® NG-RAN node2.

9.2.3.xxUE Context Information in RAN Paging

This IE contains the UE context information.

Figure 18 is a schematic block diagram of a network node 1800 according to some embodiments of the present disclosure. The network node 1800 may be, for example, a base station 402 or 406 or a network node that implements a core NF(s).

As illustrated, network node 1800 includes a control system 1802 that includes one or more processors 1804 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like), memory 1806, and a network interface 1808. The one or more processors 1804 are also referred to herein as processing circuitry. In addition, if the network node 1800 is a radio access node, the network node 1800 includes one or more radio units 1810 that each includes one or more transmitters 1812 and one or more receivers 1814 coupled to one or more antennas 1816. The radio units 1810 may be referred to or be part of radio interface circuitry. In some embodiments, the radio unit(s) 1810 is external to the control system 1802 and connected to the control system 1802 via, e.g., a wired connection (e.g., an optical cable). Flowever, in some other embodiments, the radio unit(s) 1810 and potentially the antenna(s) 1816 are integrated together with the control system 1802. The one or more processors 1804 operate to provide one or more functions of a network node 1800 as described herein (e.g., one or more functions of a last serving base station 402-S, one or more functions of a (potential) target base station 402-T1, one or more functions of an AMF, one or more functions of an SMF, or one or more functions of a UPF, as described herein). In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 1806 and executed by the one or more processors 1804.

Figure 19 is a schematic block diagram that illustrates a virtualized embodiment of the network node 1800 according to some embodiments of the present disclosure. This discussion is equally applicable to other types of network nodes. Further, other types of network nodes may have similar virtualized architectures.

As used herein, a "virtualized" network node is an implementation of the network node 1800 in which at least a portion of the functionality of the network node 1800 is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, in this example, the network node 1800 includes one or more processing nodes 1900 coupled to or included as part of a network(s) 1902. Each processing node 1900 includes one or more processors 1904 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 1906, and a network interface 1908. If the network node 1800 is a radio access node, the network node 1800 may include the control system 1802 that includes the one or more processors 1804 (e.g., CPUs, ASICs, FPGAs, and/or the like), the memory 1806, and the network interface 1808 and the one or more radio units 1810 that each includes the one or more transmitters 1812 and the one or more receivers 1814 coupled to the one or more antennas 1816, as described above. The control system 1802 is connected to the radio unit(s) 1810 via, for example, an optical cable or the like. If present, the control system 1802 is connected to the one or more processing nodes 1900 coupled to or included as part of the network(s) 1902 via the network interface 1808.

In this example, functions 1910 of the network node 1800 described herein (e.g., one or more functions of a last serving base station 402-S, one or more functions of a (potential) target base station 402-T1, one or more functions of an AMF, one or more functions of an SMF, or one or more functions of a UPF, as described herein) are implemented at the one or more processing nodes 1900 or distributed across the control system 1802 and the one or more processing nodes 1900 in any desired manner. In some particular embodiments, some or all of the functions 1910 of the network node 1800 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 1900. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) 1900 and the control system 1802 is used in order to carry out at least some of the desired functions 1910. Notably, in some embodiments, the control system 1802 may not be included, in which case the radio unit(s) 1810 communicate directly with the processing node(s) 1900 via an appropriate network interface(s).

In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the network node 1800 or a node (e.g., a processing node 1900) implementing one or more of the functions 1910 of the network node 1800 in a virtual environment according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

Figure 20 is a schematic block diagram of the network node 1800 according to some other embodiments of the present disclosure. The network node 1800 includes one or more modules 2000, each of which is implemented in software. The module(s) 2000 provide the functionality of the network node 1800 described herein (e.g., one or more functions of a last serving base station 402-S, one or more functions of a (potential) target base station 402-T1, one or more functions of an AMF, one or more functions of an SMF, or one or more functions of a UPF, as described herein). This discussion is equally applicable to the processing node 1900 of Figure 19 where the modules 2000 may be implemented at one of the processing nodes 1900 or distributed across multiple processing nodes 1900 and/or distributed across the processing node(s) 1900 and the control system 1802.

Figure 21 is a schematic block diagram of a UE 2100 according to some embodiments of the present disclosure. As illustrated, the UE 2100 includes one or more processors 2102 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 2104, and one or more transceivers 2106 each including one or more transmitters 2108 and one or more receivers 2110 coupled to one or more antennas 2112. The transceiver(s) 2106 includes radio-front end circuitry connected to the antenna(s) 2112 that is configured to condition signals communicated between the antenna(s) 2112 and the processor(s) 2102, as will be appreciated by on of ordinary skill in the art. The processors 2102 are also referred to herein as processing circuitry. The transceivers 2106 are also referred to herein as radio circuitry. In some embodiments, the functionality of the UE 2100 described above may be fully or partially implemented in software that is, e.g., stored in the memory 2104 and executed by the processor(s) 2102. Note that the UE 2100 may include additional components not illustrated in Figure 21 such as, e.g., one or more user interface components (e.g., an input/output interface including a display, buttons, a touch screen, a microphone, a speaker(s), and/or the like and/or any other components for allowing input of information into the UE 2100 and/or allowing output of information from the UE 2100), a power supply (e.g., a battery and associated power circuitry), etc.

In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the UE 2100 according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

Figure 22 is a schematic block diagram of the UE 2100 according to some other embodiments of the present disclosure. The UE 2100 includes one or more modules 2200, each of which is implemented in software. The module(s) 2200 provide the functionality of the UE 2100 described herein.

Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure.

While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.).

At least some of the following abbreviations may be used in this disclosure. If there is an inconsistency between abbreviations, preference should be given to how it is used above. If listed multiple times below, the first listing should be preferred over any subsequent listing(s).

• 3GPP Third Generation Partnership Project

• 5G Fifth Generation

• 5GC Fifth Generation Core

• 5GS Fifth Generation System

• ACK Acknowledgement

• AF Application Function

• AM Acknowledged Mode

• AMF Access and Mobility Management Function

• AN Access Network

• AP Access Point

• ARFCN Absolute Radio Frequency Channel Number

• AS Access Stratum

• ASIC Application Specific Integrated Circuit

• AUSF Authentication Server Function

• CPU Central Processing Unit

• C-RNTI Cell Radio Network Temporary Identifier • DCCH Dedicated Control Channel

• DN Data Network

• DSP Digital Signal Processor

• eNB Enhanced or Evolved Node B

• EPC Evolved Packet Core

• E-UTRAN Evolved Universal Terrestrial Radio Access Network

• FPGA Field Programmable Gate Array

• gNB New Radio Base Station

• gNB-DU New Radio Base Station Distributed Unit

• HSS Flome Subscriber Server

• ID Identity

• IE Information Element

• IoT Internet of Things

• IP Internet Protocol

• I-RNTI Inactive Radio Network Temporary Identifier

• KgNB Key gNB

• LTE Long Term Evolution

• MME Mobility Management Entity

• MTC Machine Type Communication

• NCC Next Hop Chaining Count

• NEF Network Exposure Function

• NF Network Function

• NG The interface between the gNB and the 5GC

• NG-RAN Next Generation Radio Access Network

• NG-U The user plane part of NG

• NH Next Hop

• NR New Radio

• NRF Network Function Repository Function

• NSSF Network Slice Selection Function

• PC Personal Computer

• PCCH Paging Control Channel

• PCell Primary Cell

• PCF Policy Control Function PCI Physical Cell Identity

PDU Protocol Data Unit

P-GW Packet Data Network Gateway

PO Paging Occasion

QoS Quality of Service

RAM Random Access Memory

RAN Radio Access Network

RAT Radio Access Technology

RLC Radio Link Control

RNA Radio Access Network Notification Area

RNTI Radio Network Temporary Identifier

ROHC Robust Header Compression

ROM Read Only Memory

RRC Radio Resource Control

RRH Remote Radio Head

RTT Round Trip Time

SAP Service Access Point

SCEF Service Capability Exposure Function

SMF Session Management Function

SRB Signaling Radio Bearer

TM Transparent Mode

TS Technical Specification

UDM Unified Data Management

UE User Equipment

UP User Plane

UPF User Plane Function

Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.