PATENT DOCUMENT

Publication Number: US-11871291-B2
Application Number: US-201816976646-A
Country: US
Kind Code: B2

Title: Data forwarding tunnel establishment between two user plane functions in fifth generation

Abstract:
This disclosure describes systems, methods, and devices related to data forwarding tunnel establishment between two user plane functions in fifth generation (5G). A device may determine an association of an access and mobility management function (AMF) with a first radio access network (RAN). The device may identify a handover request message received from the first RAN via the AMF. The device may identify a request to establish an indirect data forwarding associated with the handover, wherein the request is received from the first RAN via the AMF. The device may cause to send a response addressed to the AMF indicating that the indirect data forwarding is established.

Claims:
What is claimed is: 
     
       1. A device, comprising a processor configured to implement a session management function (SMF), wherein the processor is configured to:
 determine an association of an access and mobility management function (AMF) with a first radio access network (RAN); 
 identify a handover request message received from the first RAN via the AMF, wherein the handover request message indicates one or more quality of service (QoS) flows; 
 identify a request to establish an indirect data forwarding associated with a handover, wherein the request is received from the first RAN via the AMF; 
 cause transmission of a first create indirect data forwarding tunnel request message to a source user plane function (UPF); 
 cause transmission of a second create indirect data forwarding tunnel request message to a target UPF; 
 cause transmission of a modification request message to a protocol data unit (PDU) session anchor (PSA), wherein the modification request message includes a target UPF Internet protocol (IP) address and a tunnel endpoint identification (TEID), the TEID being associated with the indirect data forwarding; and 
 cause transmission of a response addressed to the AMF indicating that the indirect data forwarding is established for the one or more QoS flows. 
 
     
     
       2. The device of  claim 1 , wherein the processor is further configured to:
 identify a create indirect data forwarding tunnel response from the source UPF. 
 
     
     
       3. The device of  claim 1 , wherein the processor is further configured to:
 identify a handover complete notification received from the AMF; and 
 cause transmission of a handover complete acknowledgment addressed to the AMF. 
 
     
     
       4. The device of  claim 1 , wherein the first RAN is a source RAN associated with the handover, and wherein the processor is further configured to determine a target RAN associated with the handover. 
     
     
       5. The device of  claim 4 , wherein the processor is further configured to determine that the source UPF is associated with the source RAN and the target UPF is associated with the target RAN. 
     
     
       6. The device of  claim 1 , wherein the processor is further configured to discontinue employment of the indirect data forwarding. 
     
     
       7. The device of  claim 1 , wherein the indirect data forwarding includes forwarding data from the first RAN to the second RAN via the source UPF and the target UPF. 
     
     
       8. The device of  claim 1 , wherein the first create indirect data forwarding tunnel request message includes an internet protocol (IP) address of the source UPF and an IP address of the target UPF. 
     
     
       9. The device of  claim 8 , wherein the first create indirect data forwarding tunnel request message further includes a TEID for data forwarding. 
     
     
       10. The device of  claim 1 , wherein the handover request message indicates a need for N2 based handover and a reason for N2 based handover; and
 wherein the reason for N2 based handover comprises one of: a lack of an Xn interface between the first RAN and a second RAN, or a lack of IP connectivity between the second RAN and the source UPF. 
 
     
     
       11. A method comprising, with one or more processors implementing a session management function (SMF) of a device,
 determining an association of an access and mobility management function (AMF) with a first radio access network (RAN); 
 identifying a handover request messages received from the first RAN via the AMF, wherein the handover request message indicates one or more quality of service (QoS) flows; 
 identifying a request to establish an indirect data forwarding associated with a handover, wherein the request is received from the first RAN via the AMF; 
 causing transmission of a first create indirect data forwarding tunnel request message to a source user plane function (UPF); 
 causing transmission of a second create indirect data forwarding tunnel request message to a target UPF; 
 causing transmission of a modification request message to a PDU session anchor (PSA), wherein the modification request message includes a target UPF internet protocol (IP) address and a tunnel endpoint identification (TEID), the TEID being associated with the indirect data forwarding; and 
 causing transmission of a response addressed to the AMF indicating that the indirect data forwarding is established for the one or more QoS flows. 
 
     
     
       12. The method of  claim 11 , wherein the SMF is communicatively coupled to the source UPF and the target UPF, and wherein the source UPF and the target UPF are associated with the handover. 
     
     
       13. The method of  claim 11 , wherein the handover request message further includes a protocol data unit (PDU) session ID and a target ID, wherein the target ID is associated with a target RAN. 
     
     
       14. The method of  claim 11 , further comprising:
 identifying a create indirect data forwarding tunnel response from the source UPF. 
 
     
     
       15. The method of  claim 11 , further comprising:
 identifying a handover complete notification received from the AMF; and 
 causing to send a handover complete acknowledgment to the AMF. 
 
     
     
       16. The method of  claim 11 , further comprising:
 determining a target RAN associated with the handover, and wherein the first RAN is a source RAN associated with the handover. 
 
     
     
       17. The method of  claim 11 , further comprising:
 identifying a session establishment response message received from the target UPF. 
 
     
     
       18. The method of  claim 11 , further comprising:
 deleting the indirect data forwarding tunnel to the target UPF. 
 
     
     
       19. An apparatus comprising means to perform a method as claimed in  claim 11 . 
     
     
       20. A non-transitory computer readable medium, having computer-executable instructions stored thereon that, when executed by a processor, cause the processor to implement a session management function (SMF), wherein the instructions comprise instructions that cause the processor to:
 determine an association of an access and mobility management function (AMF) with a first radio access network (RAN); 
 identify a handover request message received from the first RAN via the AMF; 
 identify a request to establish an indirect data forwarding tunnel associated with a handover, wherein the request is received from the AMF; 
 in response to the request to establish the indirect data forwarding tunnel:
 cause transmission of a first create indirect data forwarding tunnel request message to a source user plane function (UPF); 
 cause transmission of a second create indirect data forwarding tunnel request message to a target UPF; 
 
 cause transmission of a modification request message to a protocol data unit (PDU) session anchor (PSA), wherein the modification request message includes a target UPF internet protocol (IP) address and a tunnel endpoint identification (TEID), the TEID being associated with the indirect data forwarding; and 
 cause transmission of a response addressed to the AMF indicating that the indirect data forwarding is established. 
 
     
     
       21. The non-transitory computer readable medium of  claim 20 , wherein the SMF is communicatively coupled to the source UPF and the target UPF, and wherein the source UPF and the target UPF are associated with the handover. 
     
     
       22. The non-transitory computer readable medium of  claim 20 , wherein the handover request message includes a PDU session ID and a target ID wherein the target ID is associated with a target RAN. 
     
     
       23. The non-transitory computer readable medium of  claim 20 , wherein the instructions further comprise instructions that cause the processor to:
 identify a create indirect data forwarding tunnel response from the source UPF.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of U.S. Provisional Application No. 62/541,589, filed Aug. 4, 2017, the disclosure of which is incorporated herein by reference as if set forth in full. 
    
    
     TECHNICAL FIELD 
     This disclosure generally relates to systems, methods, and devices for wireless communications and, more particularly, to data forwarding tunnel establishment between two user plane functions in fifth generation (5G). 
     BACKGROUND 
     Wireless mobile communication technology uses various standards and protocols to transmit data between a base station and a wireless mobile device. Wireless communication system standards and protocols can include the 3rd Generation Partnership Project (3GPP) long-term evolution (LTE); the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard, which is commonly known to industry groups as worldwide interoperability for microwave access (WiMAX); and the IEEE 802.11 standard for wireless local area networks (WLANs), which is commonly known to industry groups as Wi-Fi. In 3GPP radio access networks (RANs) in LTE systems, the base station can include a RAN node, such as an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (also commonly denoted as evolved Node B, enhanced Node B, eNodeB, or eNB), and/or a Radio Network Controller (RNC) in an E-UTRAN, which communicate with a wireless communication device, known as user equipment (UE). In fifth generation (5G) wireless RANs, RAN nodes can include a 5G Node (e.g., 5G eNB or gNB). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    depicts a diagram illustrating an N2 based handover with user plane function (UPF) relocation procedure, in accordance with one or more example embodiments of the present disclosure. 
         FIG.  2    depicts an architecture of a system, in accordance with one or more example embodiments of the present disclosure. 
         FIG.  3    depicts an architecture of a system, in accordance with one or more example embodiments of the present disclosure. 
         FIG.  4    illustrates a flow diagram of an illustrative process for a data forwarding tunnel establishment system, in accordance with one or more example embodiments of the present disclosure. 
         FIG.  5    illustrates a flow diagram of an illustrative process for a data forwarding tunnel establishment system, in accordance with one or more example embodiments of the present disclosure. 
         FIG.  6    illustrates example components of a device, in accordance with one or more example embodiments of the present disclosure. 
         FIG.  7    illustrates example interfaces of baseband circuitry, in accordance with one or more example embodiments of the present disclosure. 
         FIG.  8    is an illustration of a control plane protocol stack, in accordance with one or more example embodiments of the present disclosure. 
         FIG.  9    is an illustration of a user plane protocol stack, in accordance with one or more example embodiments of the present disclosure. 
         FIG.  10    illustrates components of a core network, in accordance with one or more example embodiments of the present disclosure. 
         FIG.  11    is a block diagram illustrating components of a system to support network function virtualization (NFV), in accordance with one or more example embodiments of the present disclosure. 
         FIG.  12    is a block diagram illustrating one or more components, in accordance with one or more example embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description refers to the accompanying drawings. The same reference numbers may be used in different drawings to identify the same or similar elements. In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular structures, architectures, interfaces, techniques, etc. in order to provide a thorough understanding of the various aspects of various embodiments. However, it will be apparent to those skilled in the art having the benefit of the present disclosure that the various aspects of the various embodiments may be practiced in other examples that depart from these specific details. In certain instances, descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the various embodiments with unnecessary detail. For the purposes of the present document, the phrase “A or B” means (A), (B), or (A and B). 
     Due to user equipment (UE) mobility, if an Xn interface between two fifth generation (5G) radio access network (RAN) nodes (e.g., next generation nodeBs (gNBs) and the like) is not available, the gNB may initiate N2 based handover by involving the Access and Mobility Function (AMF) and Session Management Function (SMF). During this procedure, the user plane function (UPF) (UL CL) will be relocated, the data forwarding tunnel between the source UPF and target UPF is needed for the purpose of lossless data. Currently, this data forwarding tunnel in the according procedure between the two UPFs does not exist, and there is no agreed-to solution to establish the data forwarding tunnel between the source RAN and target UPF. 
     In one or more embodiments, a data forwarding tunnel establishment system may introduce a mechanism for establishing an indirect data forwarding tunnel between a source RAN and a target RAN during handover. During a handover procedure, if the downlink data is not forwarded from the source RAN to the target RAN, the downlink data, or portions of downlink data will be lost, which could also end the handover procedure. 
     In one or more embodiments, a device (e.g., a UE) may be connected to a 5G network. When the UE moves around and needs to handover from a source RAN to a target RAN, some downlink data may sent to the source RAN after the UE has left the source RAN. Therefore, if no data forwarding tunnel exists between the source RAN and the target RAN, then the downlink data forwarded to the source RAN will be lost causing data integrity issues. 
     In one or more embodiments, a data forwarding tunnel establishment system may apply to scenarios where a source RAN and a target RAN in a handover procedure that do not have a direct connection between them to allow for direct downlink data forward. In that case, an indirect data forwarding may be needed. 
     In one or more embodiments, a data forwarding tunnel establishment system may facilitate that a source RAN needs to determine when an indirect forwarding is needed between the source UPF and target UPF. The source RAN node may decide to initiate an N2-based handover to the target RAN node due to e.g., no Xn connectivity to the target RAN node or the target RAN has no IP connectivity with source UPF based on its configuration or Xn based handover preparation failure due to target RAN informing that there is no IP connectivity between target RAN and source UPF. The source RAN node sends a Handover Required message (Target ID, Source to Target transparent container, SM N2 info list including PDU session IDs, reason for N2 based handover (e.g., no Xn interface between the source RAN and target RAN, no IP connectivity between target RAN and source UPF), indicating whether indirect data forwarding tunnel is needed between the source UPF and target UPF) to the access &amp; mobility management Function (AMF). 
     In one or more embodiments, a data forwarding tunnel establishment system may facilitate that when SMF receives the Create Indirect Data Forwarding Tunnel Request message from AMF, it will establish the indirect data forwarding tunnel between the source UPF and target UPF for the purpose of forwarding downlink data with no loss. 
     In one or more embodiments, a data forwarding tunnel establishment system may facilitate that when SMF was notified about the completion of handover, it will delete the indirect data forwarding tunnel between the source UPF and target UPF. 
     In one or more embodiments, a data forwarding tunnel establishment system may facilitate that the SMF may notify source RAN node to release the UE context. 
     In one or more embodiments, a data forwarding tunnel establishment system may facilitate that the SMF may delete the User Plane connection between the source RAN node and the source UPF. 
     In one or more embodiments, a data forwarding tunnel establishment system may include in the Handover Required message, source RAN node needs to inform AMF about the reason (e.g., no Xn interface between the source RAN and target RAN, no IP connectivity between target RAN and source UPF) for N2 based handover and indication of whether indirect data forwarding tunnel is needed between the source UPF and target UPF. 
     In one or more embodiments, by configuration, if the SMF knows the source RAN nodes cannot communicate with the target UPF, it will establish the temporary data forwarding tunnel between the source UPF and target UPF. 
     For edge computing cases, if the target UPF can serve the application function (AF), this tunnel can be released after data forwarding for a period of time; otherwise, the data forwarding tunnel will be maintained until the UE moves to a new target UPF which can serve the AF. The embodiments discussed herein may benefit the enabling of end to end edge computing solution in 5G systems by guaranteeing data integrity during UE mobility. 
       FIG.  1    depicts a diagram illustrating an N2 based handover with user plane function (UPF) relocation procedure, in accordance with one or more example embodiments of the present disclosure. 
     Referring to  FIG.  1   , there is shown a UE  102  involved in a handover from a Source RAN  104  to a Target RAN  106 . Further, there is shown an AMF  108 , an SMF  110 , a Source UPF  112 , a Target UPF  114 , and a UPF session anchor (PSA)  116 . 
     It should be noted that when edge computing is supported, the Source UPF  112  may be the source uplink classifier and the Target UPF  114  may be the target uplink classifier, the PDU session anchor (PSA) may be the local traffic offload anchor or local PDU session anchor. Uplink classifier, PSA and local traffic offload anchor are defined in current specifications. 
     The procedure of  FIG.  1    may operate as follows: 
     The Source RAN  104  node may decide to initiate an N2-based handover to the Target RAN  106  node due to, for example, no Xn connectivity to the Target RAN  106  node or the Target RAN  106  has no IP connectivity with Source UPF  112  based on its configuration or Xn based handover preparation failure due to Target RAN  106  informing that there is no IP connectivity between Target RAN  106  and Source UPF  112 . The Source RAN  104  node sends a Handover Required message  1 . The handover required message  1  may comprise, at least in part, a Target ID, a Source to Target transparent container, a session management N2 information list including PDU session IDs, a reason for N2 based handover, an indication of whether indirect data forwarding tunnel is needed between the Source UPF  112  and Target UPF  114 . The reason for N2 based handover may include, for example, no Xn interface between the Source RAN  104  and Target RAN  106 , no IP connectivity between Target RAN  106  and Source UPF  112 . 
     In one or more embodiments, the Source to Target transparent container may include RAN information created by the Source RAN  104  to be used by the Target RAN  106 , and is transparent to 3GPP 5G core network (5GCN). The SM N2 info list may include information of all PDU sessions handled by the Source RAN  104  (e.g., all existing PDU sessions with active UP connections), indicating which of those PDU session(s) are requested by the Source RAN  104  to handover. The Source RAN  104  may also include which quality of service (QoS) flows are subject to data forwarding. 
     In one or more embodiments, the AMF  108  sends a PDU Handover request message  2  (PDU session ID, Target ID) to SMF  110 . 
     In one embodiment, if the UE has moved out of the subscribed service area of the PDU session which leads to no IP connectivity between Target RAN  106  node and Source UPF  112 , the SMF  110  should be notified and SMF  110  needs to reselect the serving UPF. 
     In one or more embodiments, the AMF  108  may need to send this message to SMF  110  for each PDU session whose serving UPF&#39;s service area cannot serve the UE&#39;s Target RAN  106  node. For those PDU sessions whose serving UPF&#39;s service area can still serve the UE&#39;s Target RAN  106  node, steps  2 - 5  are not needed. 
     In one or more embodiments, at optional block  3  and based on the new location information, the SMF  110  may check if N2 Handover for the indicated PDU session can be accepted. The SMF  110  checks also the UPF selection criteria. If UE has moved out of the service area of the UPF, SMF  110  reselects a UPF for this PDU session. 
     In one or more embodiments, the SMF  110  may send a N4 Session Establishment Request  4   a  to the selected Target UPF  114 . 
     In one embodiment, if the SMF  110  selects a new intermediate UPF, Target UPF  114  (Target UPF  114 ), for the PDU session and if CN Tunnel Info is allocated by the Target UPF  114 , an N4 Session Establishment Request message is sent to the Target UPF  114 , providing Packet detection, enforcement and reporting rules to be installed on the Target UPF  114 . The PDU session anchor tunnel info for this PDU Session is also provided to the Target UPF  114 . 
     In one or more embodiments, the Target UPF  114  may respond with a N4 Session Establishment Response message  4   b  to the SMF  110 . 
     In one embodiment, the Target UPF  114  may send an N4 Session Establishment Response message to the SMF  110  with client node (CN) downlink (DL) tunnel info and uplink (UL) Tunnel info (e.g., N3 tunnel info). The SMF  110  starts a timer, to be used in step  22   a.    
     In one or more embodiments, the SMF  110  sends a PDU Handover Response (PDU session ID, SM N2 info) message  5  to the AMF  108 . The SMF  110  includes the result in SM N2 info sent, transparently for the AMF  108 , to the Target RAN  106 . If N2 handover for the PDU session is accepted the SM N2 info also includes PDU session ID, N3 UP address and Tunnel ID of UPF, and QoS parameters. 
     One or more embodiments, at block  6  the AMF  108  supervises the PDU Handover Response messages from the involved SMFs  110 . The lowest value of the Max delay indications for the PDU sessions that are candidates for handover gives the maximum time AMF  108  may wait for PDU Handover Response messages before continuing with the N2 Handover procedure. At expiry of the maximum wait time or when all PDU Handover Response messages are received, AMF  108  continues with the N2 Handover procedure (Handover Request message in step  8 ). 
     In one or more embodiments, the AMF  108  may send a Handover Request message  7  to Target RAN  106  node. The handover request message  7  may comprise a Source to Target transparent container, a mobility management (MM) N2 info, a session management (SM) N2 info list, or a reason for N2 based handover. 
     In one embodiment, the AMF  108  determines Target RAN  106  based on Target ID. The AMF  108  may allocate a globally unique temporary identifier (GUTI) valid for the UE in the AMF  108  and target tracking area identity (TAI). 
     In one embodiment, the source to Target transparent container is forwarded as received from Source RAN  104 . MM N2 info includes e.g., security information and Handover Restriction List. The SM N2 info list may include SM N2 info from Source RAN  104 . 
     In one or more embodiments, the Target RAN  106  may send a Handover Request Acknowledge Target RAN  106  message  8  to the AMF  108 . The handover Request acknowledge message  8  may comprise at least in part a Target to Source transparent container, a SM N2 response list, a PDU sessions failed to be setup list, or a Target RAN  106  SM N3 forwarding info list. 
     The Target to Source transparent container may include a UE container with an access stratum part and a NAS part. The UE container is sent transparently via AMF  108  and Source RAN  104  to the UE. 
     In one embodiment, the information provided to the Source RAN  104  also contains a list of PDU session IDs indicating PDU sessions failed to be setup and reason for failure (Target RAN  106  decision). The SM N2 response list includes, per each received SM N2 info a PDU session ID and an indication if Target RAN  106  accepted the N2 Handover request for the PDU session. For each accepted PDU session for N2 Handover, the SM N2 response includes N3 UP address and Tunnel ID of Target RAN  106  for downlink traffic on N3 (one tunnel per PDU session). The Target RAN  106  SM N3 forwarding info list includes, per each PDU session accepted by Target RAN  106  and has at least one QoS flow subject for data forwarding, N3 UP address and Tunnel ID of Target RAN  106  for receiving forwarded data if necessary. 
     In one or more embodiments, the AMF  108  sends a PDU Handover Cancel (PDU session ID) message  9  to the SMF  110 . When a PDU Handover Response message arriving too late (see step  6 ), or the PDU session with SMF  110  involvement in step  2  is not accepted by Target RAN  106 , this message is indicated to the corresponding SMF  110  allowing the SMF  110  to deallocate a possibly allocated N3 UP address and Tunnel ID of the selected UPF. A PDU session handled by that SMF  110  is considered deactivated and handover attempt is terminated for that PDU session. 
     In one or more embodiments, the AMF  108  sends a Create Indirect Data Forwarding Tunnel Request message  10  to the SMF  110  in case direct data forwarding from Source RAN  104  node to Target RAN  106  node is not possible due to one or more issues. When receiving this message, the SMF  110  knows Xn based direct data forwarding between the Source RAN  104  node and Target RAN  106  node is unavailable and will create the indirect data forwarding tunnel between the Source UPF  112  and Target UPF  114 . It should be noted that in case the Source UPF  112  has no connectivity to the Target RAN  106  and the Target UPF  114  cannot serve the AF, SMF  110  may decide to insert the Target UPF  114  (e.g., UL CL) between the Target RAN  106  and the Source UPF  112  (e.g., UL CL) in order for the locally offloaded data to be forwarded to the AF. 
     In one or more embodiments, the SMF  110  may send N4 Create Indirect Data Forwarding Tunnel Request message  11   a , which may include a Source UPF  112 &#39;s IP address and tunnel endpoint identification (TEID), for data forwarding, a UPF (PSA)&#39;s IP address and TEID for N9 interface) to the Target UPF  114  to establishment the indirect data forwarding tunnel between the Source UPF  112  and Target UPF  114 . 
     In one or more embodiments, the Target UPF  114  may respond to the SMF  110  with N4 Session Establishment Response message (e.g., message  4   b ) and Create Indirect Data Forwarding Tunnel Response message  11   b.    
     In one or more embodiments, the SMF  110  sends a Create Indirect Data Forwarding Tunnel Request message  12   a  to Source UPF  112  including the source and Target UPF  114 &#39;s User Plane IP address and TEID for data forwarding. 
     In one or more embodiments, the Source UPF responds to SMF  110  with Create Indirect Data Forwarding Tunnel Response message  12   b.    
     In one or more embodiments, the SMF  110  responds to AMF  108  with Create Indirect Data Forwarding Tunnel Response message  13 . 
     In one or more embodiments, the AMF  108  sends a Handover Command (Target to Source transparent container, SM forwarding info list) message  14  to the Source RAN  104  node. The Target to Source transparent container is forwarded as received from AMF  108 . The SM forwarding info list includes Target RAN  106  SM N3 forwarding info list for direct forwarding or Target UPF  114  SM N3 forwarding info list for indirect data forwarding. 
     In one or more embodiments, the Source RAN  104  node sends a Handover Command (UE container) message  15  to UE. UE container is sent transparently from Target RAN  106  via AMF  108  to Source RAN  104  and is provided to the UE by the Source RAN  104 . 
     In one or more embodiments, the downlink data is forwarded (e.g., directly using a direct downlink data forwarding message  16   a  or indirect downlink data forwarding message  16   b ) from the Source RAN  104  node to the Target RAN  106  node via Source UPF  112  and Target UPF  114  after this step. 
     In one or more embodiments, the UE sends a Handover Confirm message  17  to Target RAN  106  node. After the UE has successfully synchronized to the target cell, it sends a Handover Confirm message to the Target RAN  106 . Handover is by this message considered as successful by the UE. It should be noted that the uplink data is sent from the Target RAN  106  to the Target UPF  114  and the UPF (PSA). 
     In one or more embodiments, the Target RAN  106  node sends a Handover Notify message  18  to the AMF  108 . 
     In one or more embodiments, the AMF  108  sends a Handover Complete Notification message  19  to the SMF  110 . 
     In one or more embodiments, the SMF  110  sends a N4 Session Modification Request message  20   a  to UPF (PSA) including the Target UPF  114 &#39;s IP address and Tunnel Endpoint ID (TEID). UPF (PSA) will route the downlink data to Target UPF  114 . It should be noted that downlink data is sent via Target UPF  114  to Target RAN  106  node after this step. 
     In one or more embodiments, the UPF (PSA) responds to the SMF  110  with a N4 Session Modification Response message  20   b.    
     In one or more embodiments, the SMF  110  sends a N4 Session Modification Request message  21   a  to Target UPF  114  including Target RAN  106  node&#39;s user plane IP address and TEID for N3 interface. 
     In one or more embodiments, the Target UPF  114  responds to SMF  110  with a N4 Session Modification Response message  21   b.    
     In one or more embodiments, in case the Source UPF  112  is not changed, the SMF  110  needs to send a N4 Session Modification Request message  22   a  to the Source UPF  112  including the Target RAN  106  node&#39;s user plane IP address and the TEID for N3 interface. The source UPF  112  responds with an N4 session modification response message  22   b.    
     In one or more embodiments, the SMF  110  responds with a Handover Complete Acknowledge message  23  to the AMF  108 . 
     In one or more embodiments, in case some PDU sessions were not active and need to be activated due to handover, the SMF  110  needs to update those UPFs with the Target RAN  106  node&#39;s user plane IP address and the TEID for N3 interface (e.g., messages  24   a  and  24   b ). It should be noted that downlink data goes through UPF (PSA), Target UPF  114 , Target RAN  106  to UE. 
     In one or more embodiments, the SMF  110  deletes the indirect data forwarding tunnel to the Target UPF  114 . This may be accomplished by sending a N4 Delete Indirect Data Forwarding Tunnel Request message  25   a  from the SMF  110  to the Target UPF  114 . The Target UPF  114  may respond by sending a N4 Delete Indirect Data Forwarding Tunnel Response message  25   b.    
     In one or more embodiments, the SMF  110  deletes the indirect data forwarding tunnel to the Source UPF  112 . This may be accomplished by sending a Delete Indirect Data Forwarding Tunnel Request message  26   a  from the SMF  110  to the Source UPF  112 . The Source UPF  112  may respond by sending a N4 Delete Indirect Data Forwarding Tunnel Response message  26   b.    
     In one or more embodiments, the AMF  108  sends a UE Context Release Request message  27   a  to Source RAN  104  node. Source RAN  104  node will release the UE&#39;s context and responds to the AMF  108  (e.g., message  27   b ). 
     Any of the radio links described herein may operate according to any one or more of the following radio communication technologies and/or standards including but not limited to: a Global System for Mobile Communications (GSM) radio communication technology, a General Packet Radio Service (GPRS) radio communication technology, an Enhanced Data Rates for GSM Evolution (EDGE) radio communication technology, and/or a Third Generation Partnership Project (3GPP) radio communication technology, for example Universal Mobile Telecommunications System (UMTS), Freedom of Multimedia Access (FOMA), 3GPP Long Term Evolution (LTE), 3GPP Long Term Evolution Advanced (LTE Advanced), Code division multiple access 2000 (CDMA2000), Cellular Digital Packet Data (CDPD), Mobitex, Third Generation (3G), Circuit Switched Data (CSD), High-Speed Circuit-Switched Data (HSCSD), Universal Mobile Telecommunications System (Third Generation) (UMTS (3G)), Wideband Code Division Multiple Access (Universal Mobile Telecommunications System) (W-CDMA (UMTS)), High Speed Packet Access (HSPA), High-Speed Downlink Packet Access (HSDPA), High-Speed Uplink Packet Access (HSUPA), High Speed Packet Access Plus (HSPA+), Universal Mobile Telecommunications System-Time-Division Duplex (UMTS-TDD), Time Division-Code Division Multiple Access (TD-CDMA), Time Division-Synchronous Code Division Multiple Access (TD-CDMA), 3rd Generation Partnership Project Release 8 (Pre-4th Generation) (3GPP Rel. 8 (Pre-4G)), 3GPP Rel. 9 (3rd Generation Partnership Project Release 9), 3GPP Rel. 10 (3rd Generation Partnership Project Release 10), 3GPP Rel. 11 (3rd Generation Partnership Project Release 11), 3GPP Rel. 12 (3rd Generation Partnership Project Release 12), 3GPP Rel. 13 (3rd Generation Partnership Project Release 13), 3GPP Rel. 14 (3rd Generation Partnership Project Release 14), 3GPP Rel. 15 (3rd Generation Partnership Project Release 15), 3GPP Rel. 16 (3rd Generation Partnership Project Release 16), 3GPP Rel. 17 (3rd Generation Partnership Project Release 17), 3GPP Rel. 18 (3rd Generation Partnership Project Release 18), 3GPP 5G, 3GPP LTE Extra, LTE-Advanced Pro, LTE Licensed-Assisted Access (LAA), MuLTEfire, UMTS Terrestrial Radio Access (UTRA), Evolved UMTS Terrestrial Radio Access (E-UTRA), Long Term Evolution Advanced (4th Generation) (LTE Advanced (4G)), cdmaOne (2G), Code division multiple access 2000 (Third generation) (CDMA2000 (3G)), Evolution-Data Optimized or Evolution-Data Only (EV-DO), Advanced Mobile Phone System (1st Generation) (AMPS (1G)), Total Access Communication System/Extended Total Access Communication System (TACS/ETACS), Digital AMPS (2nd Generation) (D-AMPS (2G)), Push-to-talk (PTT), Mobile Telephone System (MTS), Improved Mobile Telephone System (IMTS), Advanced Mobile Telephone System (AMTS), OLT (Norwegian for Offentlig Landmobil Telefoni, Public Land Mobile Telephony), MTD (Swedish abbreviation for Mobiltelefonisystem D, or Mobile telephony system D), Public Automated Land Mobile (Autotel/PALM), ARP (Finnish for Autoradiopuhelin, “car radio phone”), NMT (Nordic Mobile Telephony), High capacity version of NTT (Nippon Telegraph and Telephone) (Hicap), Cellular Digital Packet Data (CDPD), Mobitex, DataTAC, Integrated Digital Enhanced Network (iDEN), Personal Digital Cellular (PDC), Circuit Switched Data (CSD), Personal Handy-phone System (PHS), Wideband Integrated Digital Enhanced Network (WiDEN), iBurst, Unlicensed Mobile Access (UMA), also referred to as also referred to as 3GPP Generic Access Network, or GAN standard), Zigbee, Bluetooth®, Wireless Gigabit Alliance (WiGig) standard, mmWave standards in general (wireless systems operating at 10-300 GHz and above such as WiGig, IEEE 802.11ad, IEEE 802.11ay, etc.), technologies operating above 300 GHz and THz bands, (3GPP/LTE based or IEEE 802.11p and other) Vehicle-to-Vehicle (V2V) and Vehicle-to-X (V2X) and Vehicle-to-Infrastructure (V2I) and Infrastructure-to-Vehicle (I2V) communication technologies, 3GPP cellular V2X, DSRC (Dedicated Short Range Communications) communication systems such as Intelligent-Transport-Systems and others, etc. 
     Aspects described herein can be used in the context of any spectrum management scheme including dedicated licensed spectrum, unlicensed spectrum, (licensed) shared spectrum (such as LSA=Licensed Shared Access in 2.3-2.4 GHz, 3.4-3.6 GHz, 3.6-3.8 GHz and further frequencies and SAS=Spectrum Access System in 3.55-3.7 GHz and further frequencies). Applicable spectrum bands include IMT (International Mobile Telecommunications) spectrum (including 450-MHz, 790-960 MHz, 1710-2025 MHz, 2110-2200 MHz, 2300-2400 MHz, 2500-2690 MHz, 698-790 MHz, 610-790 MHz, 3400-3600 MHz, etc). Note that some bands are limited to specific region(s) and/or countries), IMT-advanced spectrum, IMT-2020 spectrum (expected to include 3600-3800 MHz, 3.5 GHz bands, 700 MHz bands, bands within the 24.25-86 GHz range, etc.), spectrum made available under FCC&#39;s “Spectrum Frontier” 5G initiative (including 27.5-28.35 GHz, 29.1-29.25 GHz, 31-31.3 GHz, 37-38.6 GHz, 38.6-40 GHz, 42-42.5 GHz, 57-64 GHz, 71-76 GHz, 81-86 GHz and 92-94 GHz, etc), the ITS (Intelligent Transport Systems) band of 5.9 GHz (typically 5.85-5.925 GHz) and 63-64 GHz, bands currently allocated to WiGig such as WiGig Band 1 (57.24-59.40 GHz), WiGig Band 2 (59.40-61.56 GHz) and WiGig Band 3 (61.56-63.72 GHz) and WiGig Band 4 (63.72-65.88 GHz), the 70.2 GHz-71 GHz band, any band between 65.88 GHz and 71 GHz, bands currently allocated to automotive radar applications such as 76-81 GHz, and future bands including 94-300 GHz and above. Furthermore, the scheme can be used on a secondary basis on bands such as the TV White Space bands (typically below 790 MHz) where in particular the 400 MHz and 700 MHz bands are promising candidates. Besides cellular applications, specific applications for vertical markets may be addressed such as PMSE (Program Making and Special Events), medical, health, surgery, automotive, low-latency, drones, etc. applications. 
     Aspects described herein can also implement a hierarchical application of the scheme is possible, e.g., by introducing a hierarchical prioritization of usage for different types of users (e.g., low/medium/high priority, etc.), based on a prioritized access to the spectrum e.g., with highest priority to tier-1 users, followed by tier-2, then tier-3, etc. users, etc. 
     Aspects described herein can also be applied to different Single Carrier or OFDM flavors (CP-OFDM, SC-FDMA, SC-OFDM, filter bank-based multicarrier (FBMC), OFDMA, etc.) and in particular, 3GPP NR (New Radio) by allocating the OFDM carrier data bit vectors to the corresponding symbol resources. 
       FIG.  2    illustrates an architecture of a system  200  of a network, in accordance with one or more example embodiments of the present disclosure. 
     The system  200  is shown to include a user equipment (UE)  201  and a UE  202 . The UEs  201  and  202  are illustrated as smartphones (e.g., handheld touchscreen mobile computing devices connectable to one or more cellular networks), but may also comprise any mobile or non-mobile computing device, such as personal data assistants (PDAs), pagers, laptop computers, desktop computers, wireless handsets, or any computing device including a wireless communications interface. 
     In some embodiments, any of the UEs  201  and  202  can comprise an Internet of Things (IoT) UE, which can comprise a network access layer designed for low-power IoT applications utilizing short-lived UE connections. An IoT UE can utilize technologies such as machine-to-machine (M2M) or machine-type communications (MTC) for exchanging data with an MTC server or device via a public land mobile network (PLMN), a Proximity-Based Service (ProSe) or device-to-device (D2D) communication, sensor networks, or IoT networks. The M2M or MTC exchange of data may be a machine-initiated exchange of data. An IoT network describes interconnecting IoT UEs, which may include uniquely identifiable embedded computing devices (within the Internet infrastructure), with short-lived connections. The IoT UEs may execute background applications (e.g., keep-alive messages, status updates, etc.) to facilitate the connections of the IoT network. 
     The UEs  201  and  202  may be configured to connect, e.g., communicatively couple, with a radio access network (RAN)  210 . The RAN  210  may be, for example, an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN), a NextGen RAN (NG RAN), or some other type of RAN. The UEs  201  and  202  utilize connections  203  and  204 , respectively, each of which comprises a physical communications interface or layer (discussed in further detail below); in this example, the connections  203  and  204  are illustrated as air interfaces to enable communicative coupling, and can be consistent with cellular communications protocols, such as a Global System for Mobile Communications (GSM) protocol, a code-division multiple access (CDMA) network protocol, a Push-to-Talk (PTT) protocol, a PTT over Cellular (POC) protocol, a Universal Mobile Telecommunications System (UMTS) protocol, a 3GPP Long Term Evolution (LTE) protocol, a fifth generation (5G) protocol, a New Radio (NR) protocol, and the like. 
     In this embodiment, the UEs  201  and  202  may further directly exchange communication data via a ProSe interface  205 . The ProSe interface  205  may alternatively be referred to as a sidelink interface comprising one or more logical channels, including but not limited to a physical sidelink control channel (PSCCH), a physical sidelink shared channel (PSSCH), a physical sidelink discovery channel (PSDCH), and a physical sidelink broadcast channel (PSBCH). 
     The UE  202  is shown to be configured to access an access point (AP)  206  via a connection  207 . The connection  207  can comprise a local wireless connection, such as a connection consistent with any institute of electrical and electronics engineers (IEEE) 802.11 protocol, wherein the AP  206  would comprise a wireless fidelity (WiFi®) router. In this example, the AP  206  is shown to be connected to the Internet without connecting to the core network of the wireless system (described in further detail below). 
     The RAN  210  can include one or more access nodes that enable the connections  203  and  204 . These access nodes (ANs) can be referred to as base stations (BSs), NodeBs, evolved NodeBs (eNBs), next Generation NodeBs (gNB), RAN nodes, and so forth, and can comprise ground stations (e.g., terrestrial access points) or satellite stations providing coverage within a geographic area (e.g., a cell). The RAN  210  may include one or more RAN nodes for providing macrocells, e.g., macro RAN node  211 , and one or more RAN nodes for providing femtocells or picocells (e.g., cells having smaller coverage areas, smaller user capacity, or higher bandwidth compared to macrocells), e.g., low power (LP) RAN node  212 . 
     Any of the RAN nodes  211  and  212  can terminate the air interface protocol and can be the first point of contact for the UEs  201  and  202 . In some embodiments, any of the RAN nodes  211  and  212  can fulfill various logical functions for the RAN  210  including, but not limited to, radio network controller (RNC) functions such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management. 
     In accordance with some embodiments, the UEs  201  and  202  can be configured to communicate using Orthogonal Frequency-Division Multiplexing (OFDM) communication signals with each other or with any of the RAN nodes  211  and  212  over a multicarrier communication channel in accordance with various communication techniques, such as, but not limited to, an Orthogonal Frequency-Division Multiple Access (OFDMA) communication technique (e.g., for downlink communications) or a Single Carrier Frequency-Division Multiple Access (SC-FDMA) communication technique (e.g., for uplink and ProSe or sidelink communications), although the scope of the embodiments is not limited in this respect. The OFDM signals can comprise a plurality of orthogonal subcarriers. 
     In some embodiments, a downlink resource grid can be used for downlink transmissions from any of the RAN nodes  211  and  212  to the UEs  201  and  202 , while uplink transmissions can utilize similar techniques. The grid can be a time-frequency grid, called a resource grid or time-frequency resource grid, which is the physical resource in the downlink in each slot. Such a time-frequency plane representation is a common practice for OFDM systems, which makes it intuitive for radio resource allocation. Each column and each row of the resource grid corresponds to one OFDM symbol and one OFDM subcarrier, respectively. The duration of the resource grid in the time domain corresponds to one slot in a radio frame. The smallest time-frequency unit in a resource grid is denoted as a resource element. Each resource grid comprises a number of resource blocks, which describe the mapping of certain physical channels to resource elements. Each resource block comprises a collection of resource elements; in the frequency domain, this may represent the smallest quantity of resources that can be allocated currently. There are several different physical downlink channels that are conveyed using such resource blocks. 
     The physical downlink shared channel (PDSCH) may carry user data and higher-layer signaling to the UEs  201  and  202 . The physical downlink control channel (PDCCH) may carry information about the transport format and resource allocations related to the PDSCH channel, among other things. It may also inform the UEs  201  and  202  about the transport format, resource allocation, and H-ARQ (hybrid automatic repeat request) information related to the uplink shared channel Typically, downlink scheduling (assigning control and shared channel resource blocks to the UE  102  within a cell) may be performed at any of the RAN nodes  211  and  212  based on channel quality information fed back from any of the UEs  201  and  202 . The downlink resource assignment information may be sent on the PDCCH used for (e.g., assigned to) each of the UEs  201  and  202 . 
     The PDCCH may use control channel elements (CCEs) to convey the control information. Before being mapped to resource elements, the PDCCH complex-valued symbols may first be organized into quadruplets, which may then be permuted using a sub-block interleaver for rate matching. Each PDCCH may be transmitted using one or more of these CCEs, where each CCE may correspond to nine sets of four physical resource elements known as resource element groups (REGs). Four quadrature phase shift keying (QPSK) symbols may be mapped to each REG. The PDCCH can be transmitted using one or more CCEs, depending on the size of the downlink control information (DCI) and the channel condition. There can be four or more different PDCCH formats defined in the LTE with different numbers of CCEs (e.g., aggregation level, L=1, 2, 4, or 8). 
     Some embodiments may use concepts for resource allocation for control channel information that are an extension of the above-described concepts. For example, some embodiments may utilize an enhanced physical downlink control channel (EPDCCH) that uses PDSCH resources for control information transmission. The EPDCCH may be transmitted using one or more enhanced control channel elements (ECCEs). Similar to above, each ECCE may correspond to nine sets of four physical resource elements known as enhanced resource element groups (EREGs). An ECCE may have other numbers of EREGs in some situations. 
     The RAN  210  is shown to be communicatively coupled to a core network (CN)  220  via an S1 interface  213 . In some embodiments, the CN  220  may be an evolved packet core (EPC) network, a NextGen Packet Core (NPC) network, or some other type of CN. In this embodiment, the S1 interface  213  is split into two parts: the S1-U interface  214 , which carries traffic data between the RAN nodes  211  and  212  and the serving gateway (S-GW)  222 , and the S1-mobility management entity (MME) interface  215 , which is a signaling interface between the RAN nodes  211  and  212  and the MMEs  221 . 
     In this embodiment, the CN  220  comprises the MMEs  221 , the S-GW  222 , the Packet Data Network (PDN) Gateway (P-GW)  223 , and a home subscriber server (HSS)  224 . The MMEs  221  may be similar in function to the control plane of the legacy Serving General Packet Radio Service (GPRS) Support Nodes (SGSN). The MMEs  221  may manage mobility aspects in access such as gateway selection and tracking area list management. The HSS  224  may comprise a database for network users, including subscription-related information to support the network entities&#39; handling of communication sessions. The CN  220  may comprise one or several HSSs  224 , depending on the number of mobile subscribers, on the capacity of the equipment, on the organization of the network, etc. For example, the HSS  224  can provide support for routing/roaming, authentication, authorization, naming/addressing resolution, location dependencies, etc. 
     The S-GW  222  may terminate the S1 interface  213  towards the RAN  210 , and may route data packets between the RAN  210  and the CN  220 . In addition, the S-GW  222  may be a local mobility anchor point for inter-RAN node handovers and also may provide an anchor for inter-3GPP mobility. Other responsibilities may include lawful intercept, charging, and some policy enforcement. 
     The P-GW  223  may terminate an SGi interface toward a PDN. The P-GW  223  may route data packets between the EPC network and external networks such as a network including the application server  230  (alternatively referred to as an application function (AF)) via an Internet Protocol (IP) interface  225 . Generally, the application server  230  may be an element offering applications that use IP bearer resources with the core network (e.g., UMTS Packet Services (PS) domain, LTE PS data services, etc.). In this embodiment, the P-GW  223  is shown to be communicatively coupled to an application server  230  via an IP interface  225 . The application server  230  can also be configured to support one or more communication services (e.g., Voice-over-Internet Protocol (VoIP) sessions, PTT sessions, group communication sessions, social networking services, etc.) for the UEs  201  and  202  via the CN  220 . 
     The P-GW  223  may further be a node for policy enforcement and charging data collection. Policy and charging enforcement function (PCRF)  226  is the policy and charging control element of the CN  220 . In a non-roaming scenario, there may be a single PCRF in the Home Public Land Mobile Network (HPLMN) associated with a UE&#39;s Internet Protocol Connectivity Access Network (IP-CAN) session. In a roaming scenario with local breakout of traffic, there may be two PCRFs associated with a UE&#39;s IP-CAN session: a Home PCRF (H-PCRF) within an HPLMN and a Visited PCRF (V-PCRF) within a Visited Public Land Mobile Network (VPLMN). The PCRF  226  may be communicatively coupled to the application server  230  via the P-GW  223 . The application server  230  may signal the PCRF  226  to indicate a new service flow and select the appropriate quality of service (QoS) and charging parameters. The PCRF  226  may provision this rule into a policy and charging enforcement function (PCEF) (not shown) with the appropriate traffic flow template (TFT) and QoS class of identifier (QCI), which commences the QoS and charging as specified by the application server  230 . 
       FIG.  3    illustrates an architecture of a system  300  of a network in accordance with some embodiments. 
     The system  300  is shown to include a UE  301 , which may be the same or similar to UEs  201  and  202  discussed previously; a RAN node  311 , which may be the same or similar to RAN nodes  211  and  212  discussed previously; a User Plane Function (UPF)  302 ; a Data network (DN)  303 , which may be, for example, operator services, Internet access or 3rd party services; and a 5G Core Network (5GC or CN)  320 . 
     The CN  320  may include an Authentication Server Function (AUSF)  322 ; an network slice selection function (NSSF)  323 ; a Core Access and Mobility Management Function (AMF)  321 ; a Session Management Function (SMF)  324 ; a Network Exposure Function (NEF)  323 ; a Policy Control function (PCF)  327 ; a Network Function (NF) Repository Function (NRF)  326 ; a Unified Data Management (UDM)  323 ; and an Application Function (AF)  328 . The CN  320  may also include other elements that are not shown, such as a Structured Data Storage network function (SDSF), an Unstructured Data Storage network function (UDSF), and the like. 
     The UPF  302  may act as an anchor point for intra-RAT and inter-RAT mobility, an external PDU session point of interconnect to DN  303 , and a branching point to support multi-homed PDU session. The UPF  302  may also perform packet routing and forwarding, packet inspection, enforce user plane part of policy rules, lawfully intercept packets (UP collection); traffic usage reporting, perform QoS handling for user plane (e.g., packet filtering, gating, UL/DL rate enforcement), perform Uplink Traffic verification (e.g., SDF to QoS flow mapping), transport level packet marking in the uplink and downlink, and downlink packet buffering and downlink data notification triggering. UPF  302  may include an uplink classifier to support routing traffic flows to a data network. The DN  303  may represent various network operator services, Internet access, or third party services. DN  303  may include, or be similar to application server  230  discussed previously. 
     The AUSF  322  may store data for authentication of UE  301  and handle authentication related functionality. Facilitates a common authentication framework for various access types. 
     The AMF  321  may be responsible for registration management (e.g., for registering UE  301 , etc.), connection management, reachability management, mobility management, and lawful interception of AMF-related events, and access authentication and authorization. AMF  321  may provide transport for SM messages with SMF  324 , and act as a transparent proxy for routing SM messages. AMF  321  may also provide transport for short message service (SMS) messages between UE  301  and an SMS function (SMSF) (not shown by  FIG.  3   ). AMF  321  may act as Security Anchor Function (SEA), which may include interaction with the AUSF  322  and the UE  301 , receipt of an intermediate key that was established as a result of the UE  301  authentication process. Where USIM based authentication is used, the AMF  321  may retrieve the security material from the AUSF  322 . AMF  321  may also include a Security Context Management (SCM) function, which receives a key from the SEA that it uses to derive access-network specific keys. Furthermore, AMF  321  may be associated with a RAN via an interface. The AMF  321  may be a termination point of RAN CP interface (N2 reference point), a termination point of NAS (N1) signalling, and perform NAS ciphering and integrity protection. 
     AMF  321  may also support NAS signalling with a UE  301  over an N3 interworking-function (IWF) interface. The N3IWF may be used to provide access to untrusted entities. N33IWF may be a termination point for the N2 and N3 interfaces for control plane (CP) and user plane (CP), respectively, and as such, may handle N2 signalling from SMF and AMF for PDU sessions and QoS, encapsulate/de-encapsulate packets for IPSec and N3 tunnelling, mark N3 user-plane packets in the uplink, and enforce QoS corresponding to N3 packet marking taking into account QoS requirements associated to such marking received over N2. N3IWF may also relay uplink and downlink control-plane NAS (N1) signalling between the UE  301  and AMF  321 , and relay uplink and downlink user-plane packets between the UE  301  and UPF  302 . The N3IWF also provides mechanisms for IPsec tunnel establishment with the UE  301 . 
     The SMF  324  may be responsible for session management (e.g., session establishment, modify and release, including tunnel maintain between UPF and RAN node); UE IP address allocation &amp; management (including optional Authorization); Selection and control of UP function; Configures traffic steering at UPF to route traffic to proper destination; termination of interfaces towards Policy control functions; control part of policy enforcement and QoS; lawful intercept (for SM events and interface to LI System); termination of SM parts of NAS messages; downlink Data Notification; initiator of AN specific SM information, sent via AMF over N2 to AN; determine SSC mode of a session. The SMF  324  may include the following roaming functionality: handle local enforcement to apply QoS SLAs (VPLMN); charging data collection and charging interface (VPLMN); lawful intercept (in VPLMN for SM events and interface to LI System); support for interaction with external DN for transport of signalling for PDU session authorization/authentication by external DN. 
     The NEF  325  may provide means for securely exposing the services and capabilities provided by 3GPP network functions for third party, internal exposure/re-exposure, Application Functions (e.g., AF  328 ), edge computing or fog computing systems, etc. In such embodiments, the NEF  325  may authenticate, authorize, and/or throttle the AFs. NEF  325  may also translate information exchanged with the AF  328  and information exchanged with internal network functions. For example, the NEF  325  may translate between an AF-Service-Identifier and an internal 5GC information. NEF  325  may also receive information from other network functions (NFs) based on exposed capabilities of other network functions. This information may be stored at the NEF  325  as structured data, or at a data storage NF using a standardized interfaces. The stored information can then be re-exposed by the NEF  325  to other NFs and AFs, and/or used for other purposes such as analytics. 
     The NRF  326  may support service discovery functions, receive NF Discovery Requests from NF instances, and provide the information of the discovered NF instances to the NF instances. NRF  326  also maintains information of available NF instances and their supported services. 
     The PCF  327  may provide policy rules to control plane function(s) to enforce them, and may also support unified policy framework to govern network behaviour. The PCF  327  may also implement a front end (FE) to access subscription information relevant for policy decisions in a UDR of UDM  323 . 
     The UDM  323  may handle subscription-related information to support the network entities&#39; handling of communication sessions, and may store subscription data of UE  301 . The UDM  323  may include two parts, an application FE and a User Data Repository (UDR). The UDM may include a UDM FE, which is in charge of processing of credentials, location management, subscription management and so on. Several different front ends may serve the same user in different transactions. The UDM-FE accesses subscription information stored in the UDR and performs authentication credential processing; user identification handling; access authorization; registration/mobility management; and subscription management. The UDR may interact with PCF  327 . UDM  323  may also support SMS management, wherein an SMS-FE implements the similar application logic as discussed previously. 
     The AF  328  may provide application influence on traffic routing, access to the Network Capability Exposure (NCE), and interact with the policy framework for policy control. The NCE may be a mechanism that allows the 5GC and AF  328  to provide information to each other via NEF  325 , which may be used for edge computing implementations. In such implementations, the network operator and third party services may be hosted close to the UE  301  access point of attachment to achieve an efficient service delivery through the reduced end-to-end latency and load on the transport network. For edge computing implementations, the 5GC may select a UPF  302  close to the UE  301  and execute traffic steering from the UPF  302  to DN  303  via the N6 interface. This may be based on the UE subscription data, UE location, and information provided by the AF  328 . In this way, the AF  328  may influence UPF (re)selection and traffic routing. Based on operator deployment, when AF  328  is considered to be a trusted entity, the network operator may permit AF  328  to interact directly with relevant NFs. 
     As discussed previously, the CN  320  may include an SMSF, which may be responsible for SMS subscription checking and verification, and relaying SM messages to/from the UE  301  to/from other entities, such as an SMS-GMSC/IWMSC/SMS-router. The SMS may also interact with AMF  321  and UDM  323  for notification procedure that the UE  301  is available for SMS transfer (e.g., set a UE not reachable flag, and notifying UDM  323  when UE  301  is available for SMS). 
     The system  300  may include the following service-based interfaces: Namf: Service-based interface exhibited by AMF; Nsmf: Service-based interface exhibited by SMF; Nnef: Service-based interface exhibited by NEF; Npcf: Service-based interface exhibited by PCF; Nudm: Service-based interface exhibited by UDM; Naf: Service-based interface exhibited by AF; Nnrf: Service-based interface exhibited by NRF; and Nausf: Service-based interface exhibited by AUSF. 
     The system  300  may include the following reference points: N1: Reference point between the UE and the AMF; N2: Reference point between the (R)AN and the AMF; N3: Reference point between the (R)AN and the UPF; N4: Reference point between the SMF and the UPF; and N6: Reference point between the UPF and a Data Network. There may be many more reference points and/or service-based interfaces between the NF services in the NFs, however, these interfaces and reference points have been omitted for clarity. For example, an N5 reference point may be between the PCF and the AF; an N7 reference point may be between the PCF and the SMF; an N11 reference point between the AMF and SMF; etc. In some embodiments, the CN  320  may include an Nx interface, which is an inter-CN interface between the MME (e.g., MME  221 ) and the AMF  321  in order to enable interworking between CN  320  and CN  220 . 
     Although not shown by  FIG.  3   , system  300  may include multiple RAN nodes  311  wherein an Xn interface is defined between two or more RAN nodes  311  (e.g., gNBs and the like) that connecting to 5GC  320 , between a RAN node  311  (e.g., gNB) connecting to 5GC  320  and an eNB (e.g., a RAN node  211  of  FIG.  2   ), and/or between two eNBs connecting to 5GC  320 . 
     In some implementations, the Xn interface may include an Xn user plane (Xn-U) interface and an Xn control plane (Xn-C) interface. The Xn-U may provide non-guaranteed delivery of user plane PDUs and support/provide data forwarding and flow control functionality. The Xn-C may provide management and error handling functionality, functionality to manage the Xn-C interface; mobility support for UE  301  in a connected mode (e.g., CM-CONNECTED) including functionality to manage the UE mobility for connected mode between one or more RAN nodes  311 . The mobility support may include context transfer from an old (source) serving RAN node  311  to new (target) serving RAN node  311 ; and control of user plane tunnels between old (source) serving RAN node  311  to new (target) serving RAN node  311 . 
     A protocol stack of the Xn-U may include a transport network layer built on Internet Protocol (IP) transport layer, and a GTP-U layer on top of a UDP and/or IP layer(s) to carry user plane PDUs. The Xn-C protocol stack may include an application layer signaling protocol (referred to as Xn Application Protocol (Xn-AP)) and a transport network layer that is built on an SCTP layer. The SCTP layer may be on top of an IP layer. The SCTP layer provides the guaranteed delivery of application layer messages. In the transport IP layer point-to-point transmission is used to deliver the signaling PDUs. In other implementations, the Xn-U protocol stack and/or the Xn-C protocol stack may be the same or similar to the user plane and/or control plane protocol stack(s) shown and described herein. 
       FIG.  4    illustrates a flow diagram of illustrative process  400  for a data forwarding tunnel establishment system, in accordance with one or more example embodiments of the present disclosure. 
     At block  402 , a device (e.g., the SMF of  FIG.  1   ) may determine an association of an access and mobility management function (AMF) with a first radio access network (RAN). For example, an AMF may be responsible for registration management (e.g., for registering UE, etc.), connection management, reachability management, mobility management, and lawful interception of AMF-related events, and access authentication and authorization. AMF may provide transport for SM messages between and SMF, and act as a transparent proxy for routing SM messages. AMF may also provide transport for short message service (SMS) messages between UE  301  and an SMS function (SMSF). AMF may act as Security Anchor Function (SEA), which may include interaction with the AUSF and the UE, receipt of an intermediate key that was established as a result of the UE authentication process. Where USIM based authentication is used, the AMF may retrieve the security material from the AUSF. The AMF may also include a Security Context Management (SCM) function, which receives a key from the SEA that it uses to derive access-network specific keys. Furthermore, the AMF may be associated with a RAN via an interface. The AMF may be a termination point of RAN CP interface (N2 reference point), a termination point of NAS (N1) signalling, and perform NAS ciphering and integrity protection. 
     At block  404 , the device may identify a handover request message received from the first RAN via the AMF (e.g., the AMF of  FIG.  1   ). For example, an SMF may determine that a source RAN need to determine when an indirect forwarding is needed between the source UPF and target UPF. The source RAN node may decide to initiate an N2-based handover to the target RAN node due to, for example, no Xn connectivity to the target RAN node or the target RAN has no IP connectivity with source UPF based on its configuration or Xn based handover preparation failure due to target RAN informing that there is no IP connectivity between target RAN and source UPF. The source RAN node sends a Handover Required message (Target ID, Source to Target transparent container, SM N2 info list including PDU session IDs, reason for N2 based handover (e.g., no Xn interface between the source RAN and target RAN, no IP connectivity between target RAN and source UPF), indication of whether indirect data forwarding tunnel is needed between the source UPF and target UPF) to the access &amp; mobility management Function (AMF). 
     At block  406 , the device may identify a request to establish an indirect data forwarding associated with the handover, wherein the request is received from the first RAN via the AMF. For example, when an SMF receives the create indirect data forwarding tunnel request message from AMF, it will establish the indirect data forwarding tunnel between the source UPF and target UPF for the purpose of forwarding downlink data with no loss. 
     At block  408 , the device may to send a response addressed to the AMF indicating that the indirect data forwarding is established. For example, a target UPF may respond to the SMF  110  with N4 Session Establishment Response message and create indirect data forwarding tunnel response message. The SMF  110  sends a create indirect data forwarding tunnel request message to Source UPF including the source and target UPF&#39;s user plane IP address and TEID for data forwarding. The Source UPF responds to SMF with create indirect data forwarding tunnel response message. The SMF responds to AMF with create indirect data forwarding tunnel response message. 
     It is understood that the above descriptions are for purposes of illustration and are not meant to be limiting. 
       FIG.  5    illustrates a flow diagram of illustrative process  500  for a data forwarding tunnel establishment system, in accordance with one or more example embodiments of the present disclosure. 
     At block  502 , a device (e.g., an eNodeB base station) may determine an association with a first radio access network (RAN) (e.g., a source RAN involved in handover procedure). For example, an AMF may be responsible for registration management (e.g., for registering UE, etc.), connection management, reachability management, mobility management, and lawful interception of AMF-related events, and access authentication and authorization. AMF may provide transport for SM messages between and SMF, and act as a transparent proxy for routing SM messages. AMF may also provide transport for short message service (SMS) messages between UE  301  and an SMS function (SMSF). AMF may act as Security Anchor Function (SEA), which may include interaction with the AUSF and the UE, receipt of an intermediate key that was established as a result of the UE authentication process. Where USIM based authentication is used, the AMF may retrieve the security material from the AUSF. The AMF may also include a Security Context Management (SCM) function, which receives a key from the SEA that it uses to derive access-network specific keys. Furthermore, the AMF may be associated with a RAN via an interface. The AMF may be a termination point of RAN CP interface (N2 reference point), a termination point of NAS (N1) signalling, and perform NAS ciphering and integrity protection. 
     At block  504 , the device may cause to send a handover required message to an access and mobility management function (AMF), wherein the handover required message comprises an indication for an indirect forwarding of downlink data to a second RAN. For example, the eNodeB may determine that a source RAN need to determine when an indirect forwarding is needed between the source UPF and target UPF. The source RAN node may decide to initiate an N2-based handover to the target RAN node due to, for example, no Xn connectivity to the target RAN node or the target RAN has no IP connectivity with source UPF based on its configuration or Xn based handover preparation failure due to target RAN informing that there is no IP connectivity between target RAN and source UPF. The source RAN node sends a Handover Required message (Target ID, Source to Target transparent container, SM N2 info list including PDU session IDs, reason for N2 based handover (e.g., no Xn interface between the source RAN and target RAN, no IP connectivity between target RAN and source UPF), indication of whether indirect data forwarding tunnel is needed between the source UPF and target UPF) to the access &amp; mobility management Function (AMF). 
     At block  506 , the device may identify a handover command message received from the AMF, wherein the handover command message comprises information about the establishment of the indirect forwarding of the downlink data. For example, when an SMF receives the create indirect data forwarding tunnel request message from AMF, it will establish the indirect data forwarding tunnel between the source UPF and target UPF for the purpose of forwarding downlink data with no loss. The AMF sends a Handover Command (Target to Source transparent container, SM forwarding info list) message to the Source RAN node. The Target to Source transparent container is forwarded as received from AMF. The SM forwarding info list includes Target RAN SM N3 forwarding info list for direct forwarding or Target UPF SM N3 forwarding info list for indirect data forwarding. 
     At block  508  the device may cause to send a response addressed to the AMF indicating that the indirect data forwarding is established. For example, an AMF may be responsible for registration management (e.g., for registering UE, etc.), connection management, reachability management, mobility management, and lawful interception of AMF-related events, and access authentication and authorization. AMF may provide transport for SM messages between and SMF, and act as a transparent proxy for routing SM messages. AMF may also provide transport for short message service (SMS) messages between UE  301  and an SMS function (SMSF). AMF may act as Security Anchor Function (SEA), which may include interaction with the AUSF and the UE, receipt of an intermediate key that was established as a result of the UE authentication process. Where USIM based authentication is used, the AMF may retrieve the security material from the AUSF. The AMF may also include a Security Context Management (SCM) function, which receives a key from the SEA that it uses to derive access-network specific keys. Furthermore, the AMF may be associated with a RAN via an interface. The AMF may be a termination point of RAN CP interface (N2 reference point), a termination point of NAS (N1) signalling, and perform NAS ciphering and integrity protection. 
     It is understood that the above descriptions are for purposes of illustration and are not meant to be limiting. 
       FIG.  6    illustrates example components of a device  600  in accordance with some embodiments. In some embodiments, the device  600  may include application circuitry  602 , baseband circuitry  604 , Radio Frequency (RF) circuitry  606 , front-end module (FEM) circuitry  608 , one or more antennas  610 , and power management circuitry (PMC)  612  coupled together at least as shown. The components of the illustrated device  600  may be included in a UE or a RAN node. In some embodiments, the device  600  may include less elements (e.g., a RAN node may not utilize application circuitry  602 , and instead include a processor/controller to process IP data received from an EPC). In some embodiments, the device  600  may include additional elements such as, for example, memory/storage, display, camera, sensor, or input/output (I/O) interface. In other embodiments, the components described below may be included in more than one device (e.g., said circuitries may be separately included in more than one device for Cloud-RAN (C-RAN) implementations). 
     The application circuitry  602  may include one or more application processors. For example, the application circuitry  602  may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) may include any combination of general-purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.). The processors may be coupled with or may include memory/storage and may be configured to execute instructions stored in the memory/storage to enable various applications or operating systems to run on the device  600 . In some embodiments, processors of application circuitry  602  may process IP data packets received from an EPC. 
     The baseband circuitry  604  may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry  604  may include one or more baseband processors or control logic to process baseband signals received from a receive signal path of the RF circuitry  606  and to generate baseband signals for a transmit signal path of the RF circuitry  606 . Baseband processing circuity  604  may interface with the application circuitry  602  for generation and processing of the baseband signals and for controlling operations of the RF circuitry  606 . For example, in some embodiments, the baseband circuitry  604  may include a third generation (3G) baseband processor  604 A, a fourth generation (4G) baseband processor  604 B, a fifth generation (5G) baseband processor  604 C, or other baseband processor(s)  604 D for other existing generations, generations in development or to be developed in the future (e.g., second generation (2G), si6h generation (6G), etc.). The baseband circuitry  604  (e.g., one or more of baseband processors  604 A-D) may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry  606 . In other embodiments, some or all of the functionality of baseband processors  604 A-D may be included in modules stored in the memory  604 G and executed via a Central Processing Unit (CPU)  604 E. The radio control functions may include, but are not limited to, signal modulation/demodulation, encoding/decoding, radio frequency shifting, etc. In some embodiments, modulation/demodulation circuitry of the baseband circuitry  604  may include Fast-Fourier Transform (FFT), preceding, or constellation mapping/demapping functionality. In some embodiments, encoding/decoding circuitry of the baseband circuitry  604  may include convolution, tail-biting convolution, turbo, Viterbi, or Low Density Parity Check (LDPC) encoder/decoder functionality. Embodiments of modulation/demodulation and encoder/decoder functionality are not limited to these examples and may include other suitable functionality in other embodiments. 
     In some embodiments, the baseband circuitry  604  may include one or more audio digital signal processor(s) (DSP)  604 F. The audio DSP(s)  604 F may be include elements for compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments. Components of the baseband circuitry may be suitably combined in a single chip, a single chipset, or disposed on a same circuit board in some embodiments. In some embodiments, some or all of the constituent components of the baseband circuitry  604  and the application circuitry  602  may be implemented together such as, for example, on a system on a chip (SOC). 
     In some embodiments, the baseband circuitry  604  may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry  604  may support communication with an evolved universal terrestrial radio access network (EUTRAN) or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Embodiments in which the baseband circuitry  604  is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry. 
     RF circuitry  606  may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry  606  may include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. RF circuitry  606  may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry  608  and provide baseband signals to the baseband circuitry  604 . RF circuitry  606  may also include a transmit signal path which may include circuitry to up-convert baseband signals provided by the baseband circuitry  604  and provide RF output signals to the FEM circuitry  608  for transmission. 
     In some embodiments, the receive signal path of the RF circuitry  606  may include mixer circuitry  606   a , amplifier circuitry  606   b  and filter circuitry  606   c . In some embodiments, the transmit signal path of the RF circuitry  606  may include filter circuitry  606   c  and mixer circuitry  606   a . RF circuitry  606  may also include synthesizer circuitry  606   d  for synthesizing a frequency for use by the mixer circuitry  606   a  of the receive signal path and the transmit signal path. In some embodiments, the mixer circuitry  606   a  of the receive signal path may be configured to down-convert RF signals received from the FEM circuitry  608  based on the synthesized frequency provided by synthesizer circuitry  606   d . The amplifier circuitry  606   b  may be configured to amplify the down-converted signals and the filter circuitry  606   c  may be a low-pass filter (LPF) or band-pass filter (BPF) configured to remove unwanted signals from the down-converted signals to generate output baseband signals. Output baseband signals may be provided to the baseband circuitry  604  for further processing. In some embodiments, the output baseband signals may be zero-frequency baseband signals, although this is not a requirement. In some embodiments, mixer circuitry  606   a  of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect. 
     In some embodiments, the mixer circuitry  606   a  of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry  606   d  to generate RF output signals for the FEM circuitry  608 . The baseband signals may be provided by the baseband circuitry  604  and may be filtered by filter circuitry  606   c.    
     In some embodiments, the mixer circuitry  606   a  of the receive signal path and the mixer circuitry  606   a  of the transmit signal path may include two or more mixers and may be arranged for quadrature downconversion and upconversion, respectively. In some embodiments, the mixer circuitry  606   a  of the receive signal path and the mixer circuitry  606   a  of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuitry  606   a  of the receive signal path and the mixer circuitry  606   a  may be arranged for direct downconversion and direct upconversion, respectively. In some embodiments, the mixer circuitry  606   a  of the receive signal path and the mixer circuitry  606   a  of the transmit signal path may be configured for super-heterodyne operation. 
     In some embodiments, the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternate embodiments, the output baseband signals and the input baseband signals may be digital baseband signals. In these alternate embodiments, the RF circuitry  606  may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry and the baseband circuitry  604  may include a digital baseband interface to communicate with the RF circuitry  606 . 
     In some dual-mode embodiments, a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect. 
     In some embodiments, the synthesizer circuitry  606   d  may be a fractional-N synthesizer or a fractional N/N+1 synthesizer, although the scope of the embodiments is not limited in this respect as other types of frequency synthesizers may be suitable. For example, synthesizer circuitry  606   d  may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider. 
     The synthesizer circuitry  606   d  may be configured to synthesize an output frequency for use by the mixer circuitry  606   a  of the RF circuitry  606  based on a frequency input and a divider control input. In some embodiments, the synthesizer circuitry  606   d  may be a fractional N/N+1 synthesizer. 
     In some embodiments, frequency input may be provided by a voltage controlled oscillator (VCO), although that is not a requirement. Divider control input may be provided by either the baseband circuitry  604  or the applications processor  602  depending on the desired output frequency. In some embodiments, a divider control input (e.g., N) may be determined from a look-up table based on a channel indicated by the applications processor  602 . 
     Synthesizer circuitry  606   d  of the RF circuitry  606  may include a divider, a delay-locked loop (DLL), a multiplexer and a phase accumulator. In some embodiments, the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DPA). In some embodiments, the DMD may be configured to divide the input signal by either N or N+1 (e.g., based on a carry out) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded, tunable, delay elements, a phase detector, a charge pump and a D-type flip-flop. In these embodiments, the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle. 
     In some embodiments, synthesizer circuitry  606   d  may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other. In some embodiments, the output frequency may be a LO frequency (fLO). In some embodiments, the RF circuitry  606  may include an IQ/polar converter. 
     FEM circuitry  608  may include a receive signal path which may include circuitry configured to operate on RF signals received from one or more antennas  610 , amplify the received signals and provide the amplified versions of the received signals to the RF circuitry  606  for further processing. FEM circuitry  608  may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry  606  for transmission by one or more of the one or more antennas  610 . In various embodiments, the amplification through the transmit or receive signal paths may be done solely in the RF circuitry  606 , solely in the FEM  608 , or in both the RF circuitry  606  and the FEM  608 . 
     In some embodiments, the FEM circuitry  608  may include a TX/RX switch to switch between transmit mode and receive mode operation. The FEM circuitry may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry may include an LNA to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry  606 ). The transmit signal path of the FEM circuitry  608  may include a power amplifier (PA) to amplify input RF signals (e.g., provided by RF circuitry  606 ), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas  610 ). 
     In some embodiments, the PMC  612  may manage power provided to the baseband circuitry  604 . In particular, the PMC  612  may control power-source selection, voltage scaling, battery charging, or DC-to-DC conversion. The PMC  612  may often be included when the device  600  is capable of being powered by a battery, for example, when the device is included in a UE. The PMC  612  may increase the power conversion efficiency while providing desirable implementation size and heat dissipation characteristics. 
     While  FIG.  6    shows the PMC  612  coupled only with the baseband circuitry  604 . However, in other embodiments, the PMC  612  may be additionally or alternatively coupled with, and perform similar power management operations for, other components such as, but not limited to, application circuitry  602 , RF circuitry  606 , or FEM  608 . 
     In some embodiments, the PMC  612  may control, or otherwise be part of, various power saving mechanisms of the device  600 . For example, if the device  600  is in an RRC_Connected state, where it is still connected to the RAN node as it expects to receive traffic shortly, then it may enter a state known as Discontinuous Reception Mode (DRX) after a period of inactivity. During this state, the device  600  may power down for brief intervals of time and thus save power. 
     If there is no data traffic activity for an extended period of time, then the device  600  may transition off to an RRC_Idle state, where it disconnects from the network and does not perform operations such as channel quality feedback, handover, etc. The device  600  goes into a very low power state and it performs paging where again it periodically wakes up to listen to the network and then powers down again. The device  600  may not receive data in this state, in order to receive data, it must transition back to RRC_Connected state. 
     An additional power saving mode may allow a device to be unavailable to the network for periods longer than a paging interval (ranging from seconds to a few hours). During this time, the device is totally unreachable to the network and may power down completely. Any data sent during this time incurs a large delay and it is assumed the delay is acceptable. 
     Processors of the application circuitry  602  and processors of the baseband circuitry  604  may be used to execute elements of one or more instances of a protocol stack. For example, processors of the baseband circuitry  604 , alone or in combination, may be used execute Layer 3, Layer 2, or Layer 1 functionality, while processors of the application circuitry  604  may utilize data (e.g., packet data) received from these layers and further execute Layer 4 functionality (e.g., transmission communication protocol (TCP) and user datagram protocol (UDP) layers). As referred to herein, Layer 3 may comprise a radio resource control (RRC) layer, described in further detail below. As referred to herein, Layer 2 may comprise a medium access control (MAC) layer, a radio link control (RLC) layer, and a packet data convergence protocol (PDCP) layer, described in further detail below. As referred to herein, Layer 1 may comprise a physical (PHY) layer of a UE/RAN node, described in further detail below. 
       FIG.  7    illustrates example interfaces of baseband circuitry in accordance with some embodiments. As discussed above, the baseband circuitry  604  of  FIG.  6    may comprise processors  604 A- 604 E and a memory  604 G utilized by said processors. Each of the processors  604 A- 604 E may include a memory interface,  704 A- 704 E, respectively, to send/receive data to/from the memory  604 G. 
     The baseband circuitry  604  may further include one or more interfaces to communicatively couple to other circuitries/devices, such as a memory interface  712  (e.g., an interface to send/receive data to/from memory external to the baseband circuitry  604 ), an application circuitry interface  714  (e.g., an interface to send/receive data to/from the application circuitry  602  of  FIG.  6   ), an RF circuitry interface  716  (e.g., an interface to send/receive data to/from RF circuitry  606  of  FIG.  6   ), a wireless hardware connectivity interface  718  (e.g., an interface to send/receive data to/from Near Field Communication (NFC) components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components), and a power management interface  720  (e.g., an interface to send/receive power or control signals to/from the PMC  612 . 
       FIG.  8    is an illustration of a control plane protocol stack in accordance with some embodiments. In this embodiment, a control plane  800  is shown as a communications protocol stack between the UE  501  (or alternatively, the UE  502 ), the RAN node  511  (or alternatively, the RAN node  512 ), and the MME  521 . 
     The PHY layer  801  may transmit or receive information used by the MAC layer  802  over one or more air interfaces. The PHY layer  801  may further perform link adaptation or adaptive modulation and coding (AMC), power control, cell search (e.g., for initial synchronization and handover purposes), and other measurements used by higher layers, such as the RRC layer  805 . The PHY layer  801  may still further perform error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, modulation/demodulation of physical channels, interleaving, rate matching, mapping onto physical channels, and Multiple Input Multiple Output (MIMO) antenna processing. 
     The MAC layer  802  may perform mapping between logical channels and transport channels, multiplexing of MAC service data units (SDUs) from one or more logical channels onto transport blocks (TB) to be delivered to PHY via transport channels, de-multiplexing MAC SDUs to one or more logical channels from transport blocks (TB) delivered from the PHY via transport channels, multiplexing MAC SDUs onto TBs, scheduling information reporting, error correction through hybrid automatic repeat request (HARQ), and logical channel prioritization. 
     The RLC layer  803  may operate in a plurality of modes of operation, including: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM). The RLC layer  803  may execute transfer of upper layer protocol data units (PDUs), error correction through automatic repeat request (ARQ) for AM data transfers, and concatenation, segmentation and reassembly of RLC SDUs for UM and AM data transfers. The RLC layer  803  may also execute re-segmentation of RLC data PDUs for AM data transfers, reorder RLC data PDUs for UM and AM data transfers, detect duplicate data for UM and AM data transfers, discard RLC SDUs for UM and AM data transfers, detect protocol errors for AM data transfers, and perform RLC re-establishment. 
     The PDCP layer  804  may execute header compression and decompression of IP data, maintain PDCP Sequence Numbers (SNs), perform in-sequence delivery of upper layer PDUs at re-establishment of lower layers, eliminate duplicates of lower layer SDUs at re-establishment of lower layers for radio bearers mapped on RLC AM, cipher and decipher control plane data, perform integrity protection and integrity verification of control plane data, control timer-based discard of data, and perform security operations (e.g., ciphering, deciphering, integrity protection, integrity verification, etc.). 
     The main services and functions of the RRC layer  805  may include broadcast of system information (e.g., included in Master Information Blocks (MIBs) or System Information Blocks (SIBs) related to the non-access stratum (NAS)), broadcast of system information related to the access stratum (AS), paging, establishment, maintenance and release of an RRC connection between the UE and E-UTRAN (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), establishment, configuration, maintenance and release of point to point Radio Bearers, security functions including key management, inter radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting. Said MIBs and SIBs may comprise one or more information elements (IEs), which may each comprise individual data fields or data structures. 
     The UE  501  and the RAN node  511  may utilize a Uu interface (e.g., an LTE-Uu interface) to exchange control plane data via a protocol stack comprising the PHY layer  801 , the MAC layer  802 , the RLC layer  803 , the PDCP layer  804 , and the RRC layer  805 . 
     The non-access stratum (NAS) protocols  806  form the highest stratum of the control plane between the UE  501  and the MME  521 . The NAS protocols  806  support the mobility of the UE  501  and the session management procedures to establish and maintain IP connectivity between the UE  501  and the P-GW  523  of  FIG.  5   . 
     The S1 Application Protocol (S1-AP) layer  815  may support the functions of the S1 interface and comprise Elementary Procedures (EPs). An EP is a unit of interaction between the RAN node  511  and the CN  520 . The S1-AP layer services may comprise two groups: UE-associated services and non UE-associated services. These services perform functions including, but not limited to: E-UTRAN Radio Access Bearer (E-RAB) management, UE capability indication, mobility, NAS signaling transport, RAN Information Management (RIM), and configuration transfer. 
     The Stream Control Transmission Protocol (SCTP) layer (alternatively referred to as the SCTP/IP layer)  814  may ensure reliable delivery of signaling messages between the RAN node  511  and the MME  521  based, in part, on the IP protocol, supported by the IP layer  813 . The L2 layer  812  and the L1 layer  811  may refer to communication links (e.g., wired or wireless) used by the RAN node and the MME to exchange information. 
     The RAN node  511  and the MME  521  may utilize an S1-MME interface to exchange control plane data via a protocol stack comprising the L1 layer  811 , the L2 layer  812 , the IP layer  813 , the SCTP layer  814 , and the S1-AP layer  815 . 
       FIG.  9    is an illustration of a user plane protocol stack in accordance with some embodiments. In this embodiment, a user plane  900  is shown as a communications protocol stack between the UE  501  (or alternatively, the UE  502 ), the RAN node  511  (or alternatively, the RAN node  512 ), the S-GW  522 , and the P-GW  523 . The user plane  900  may utilize at least some of the same protocol layers as the control plane  800 . For example, the UE  501  and the RAN node  511  may utilize a Uu interface (e.g., an LTE-Uu interface) to exchange user plane data via a protocol stack comprising the PHY layer  801 , the MAC layer  802 , the RLC layer  803 , the PDCP layer  804 . 
     The General Packet Radio Service (GPRS) Tunneling Protocol for the user plane (GTP-U) layer  904  may be used for carrying user data within the GPRS core network and between the radio access network and the core network. The user data transported can be packets in any of IPv4, IPv6, or PPP formats, for example. The UDP and IP security (UDP/IP) layer  903  may provide checksums for data integrity, port numbers for addressing different functions at the source and destination, and encryption and authentication on the selected data flows. The RAN node  511  and the S-GW  522  may utilize an S1-U interface to exchange user plane data via a protocol stack comprising the L1 layer  811 , the L2 layer  812 , the UDP/IP layer  903 , and the GTP-U layer  904 . The S-GW  522  and the P-GW  523  may utilize an S5/S8a interface to exchange user plane data via a protocol stack comprising the L1 layer  811 , the L2 layer  812 , the UDP/IP layer  903 , and the GTP-U layer  904 . As discussed above with respect to  FIG.  8   , NAS protocols support the mobility of the UE  501  and the session management procedures to establish and maintain IP connectivity between the UE  501  and the P-GW  523 . 
       FIG.  10    illustrates components of a core network in accordance with some embodiments. The components of the CN  520  may be implemented in one physical node or separate physical nodes including components to read and execute instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium). In some embodiments, Network Functions Virtualization (NFV) is utilized to virtualize any or all of the above described network node functions via executable instructions stored in one or more computer readable storage mediums (described in further detail below). A logical instantiation of the CN  520  may be referred to as a network slice  1001 . The network slice  1001  may include an HSS  524 , an MME  521 , an S-GW  522 , in addition to a network sub-slice  1002 . A logical instantiation of a portion of the CN  520  may be referred to as a network sub-slice  1002  (e.g., the network sub-slice  1002  is shown to include the PGW  523  and the PCRF  526 ). 
     NFV architectures and infrastructures may be used to virtualize one or more network functions, alternatively performed by proprietary hardware, onto physical resources comprising a combination of industry-standard server hardware, storage hardware, or switches. In other words, NFV systems can be used to execute virtual or reconfigurable implementations of one or more EPC components/functions. 
       FIG.  11    is a block diagram illustrating components, according to some example embodiments, of a system  1100  to support NFV. The system  1100  is illustrated as including a virtualized infrastructure manager (VIM)  1102 , a network function virtualization infrastructure (NFVI)  1104 , a VNF manager (VNFM)  1106 , virtualized network functions (VNFs)  1108 , an element manager (EM)  1110 , an NFV Orchestrator (NFVO)  1112 , and a network manager (NM)  1114 . 
     The VIM  1102  manages the resources of the NFVI  1104 . The NFVI  1104  can include physical or virtual resources and applications (including hypervisors) used to execute the system  1100 . The VIM  1102  may manage the life cycle of virtual resources with the NFVI  1104  (e.g., creation, maintenance, and tear down of virtual machines (VMs) associated with one or more physical resources), track VM instances, track performance, fault and security of VM instances and associated physical resources, and expose VM instances and associated physical resources to other management systems. 
     The VNFM  1106  may manage the VNFs  1108 . The VNFs  1108  may be used to execute EPC components/functions. The VNFM  1106  may manage the life cycle of the VNFs  1108  and track performance, fault and security of the virtual aspects of VNFs  1108 . The EM  1110  may track the performance, fault and security of the functional aspects of VNFs  1108 . The tracking data from the VNFM  1106  and the EM  1110  may comprise, for example, performance measurement (PM) data used by the VIM  1102  or the NFVI  1104 . Both the VNFM  1106  and the EM  1110  can scale up/down the quantity of VNFs of the system  1100 . 
     The NFVO  1112  may coordinate, authorize, release and engage resources of the NFVI  1104  in order to provide the requested service (e.g., to execute an EPC function, component, or slice). The NM  1114  may provide a package of end-user functions with the responsibility for the management of a network, which may include network elements with VNFs, non-virtualized network functions, or both (management of the VNFs may occur via the EM  1110 ). 
       FIG.  12    is a block diagram illustrating components, according to some example embodiments, able to read instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) and perform any one or more of the methodologies discussed herein. Specifically,  FIG.  12    shows a diagrammatic representation of hardware resources  1200  including one or more processors (or processor cores)  1210 , one or more memory/storage devices  1220 , and one or more communication resources  1230 , each of which may be communicatively coupled via a bus  1240 . For embodiments where node virtualization (e.g., NFV) is utilized, a hypervisor  1202  may be executed to provide an execution environment for one or more network slices/sub-slices to utilize the hardware resources  1200   
     The processors  1210  (e.g., a central processing unit (CPU), a reduced instruction set computing (RISC) processor, a complex instruction set computing (CISC) processor, a graphics processing unit (GPU), a digital signal processor (DSP) such as a baseband processor, an application specific integrated circuit (ASIC), a radio-frequency integrated circuit (RFIC), another processor, or any suitable combination thereof) may include, for example, a processor  1212  and a processor  1214 . 
     The memory/storage devices  1220  may include main memory, disk storage, or any suitable combination thereof. The memory/storage devices  1220  may include, but are not limited to any type of volatile or non-volatile memory such as dynamic random access memory (DRAM), static random-access memory (SRAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), Flash memory, solid-state storage, etc. 
     The communication resources  1230  may include interconnection or network interface components or other suitable devices to communicate with one or more peripheral devices  1204  or one or more databases  1206  via a network  1208 . For example, the communication resources  1230  may include wired communication components (e.g., for coupling via a Universal Serial Bus (USB)), cellular communication components, NFC components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components. 
     Instructions  1250  may comprise software, a program, an application, an applet, an app, or other executable code for causing at least any of the processors  1210  to perform any one or more of the methodologies discussed herein. The instructions  1250  may reside, completely or partially, within at least one of the processors  1210  (e.g., within the processor&#39;s cache memory), the memory/storage devices  1220 , or any suitable combination thereof. Furthermore, any portion of the instructions  1250  may be transferred to the hardware resources  1200  from any combination of the peripheral devices  1204  or the databases  1206 . Accordingly, the memory of processors  1210 , the memory/storage devices  1220 , the peripheral devices  1204 , and the databases  1206  are examples of computer-readable and machine-readable media. 
     In some embodiments, the electronic device(s), network(s), system(s), chip(s) or component(s), or portions or implementations thereof, of Figures herein may be configured to perform one or more processes, techniques, or methods as described herein, or portions thereof. 
     The following examples pertain to further embodiments. 
     Example 1 may include when SMF receives the Create Indirect Data Forwarding Tunnel Request message from AMF, it will establish the indirect data forwarding tunnel between the source UPF and target UPF for the purpose of forwarding downlink data losslessly. 
     Example 2 may include when SMF was notified about the completion of handover, it will delete the indirect data forwarding tunnel between the source UPF and target UPF. 
     Example 3 may include in parallel with example No. 2 or some other example herein, wherein the SMF will notify source RAN node to release the UE context. 
     Example 4 may include in parallel with example No. 2 and 3 or some other example herein, wherein the SMF will delete the User Plane connection between the source RAN node and the source UPF. 
     Example 5 may include in the Handover Required message, source RAN node needs to inform AMF about the reason (e.g., no Xn interface between the source RAN and target RAN, no IP connectivity between target RAN and source UPF) for N2 based handover and indication of whether indirect data forwarding tunnel is needed between the source UPF and target UPF. 
     Example 6 may include an apparatus comprising means to perform one or more elements of a method described in or related to any of examples 1-5, or any other method or process described herein. 
     Example 7 may include one or more non-transitory computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform one or more elements of a method described in or related to any of examples 1-5, or any other method or process described herein. 
     Example 8 may include an apparatus comprising logic, modules, or circuitry to perform one or more elements of a method described in or related to any of examples 1-5, or any other method or process described herein. 
     Example 9 may include a method, technique, or process as described in or related to any of examples 1-5, or portions or parts thereof. 
     Example 10 may include an apparatus comprising: one or more processors and one or more computer readable media comprising instructions that, when executed by the one or more processors, cause the one or more processors to perform the method, techniques, or process as described in or related to any of examples 1-5, or portions thereof. 
     Example 11 may include a signal as described in or related to any of examples 1-5, or portions or parts thereof. 
     Example 12 may include a signal in a wireless network as shown and described herein. 
     Example 13 may include a method of communicating in a wireless network as shown and described herein. 
     Example 14 may include a system for providing wireless communication as shown and described herein. 
     Example 15 may include a device for providing wireless communication as shown and described herein. 
     The following examples pertain to additional embodiments. 
     Example 16 may include a device comprising storage and processing circuitry configured to: determine an association of an access and mobility management function (AMF) with a first radio access network (RAN); identify a handover request message received from the first RAN via the AMF; identify a request to establish an indirect data forwarding associated with the handover, wherein the request may be received from the first RAN via the AMF; and cause to send a response addressed to the AMF indicating that the indirect data forwarding may be established. 
     Example 17 may include the device of example 16 and/or some other example herein, wherein the device may be a session management function (SMF), wherein the SMF may be communicatively coupled to at least one of a first user plane function (UPF) and a second UPF, the first UPF and the second UPF are associated with the handover. 
     Example 18 may include the device of example 16 and/or some other example herein, wherein the handover request message may include a protocol data unit (PDU) session ID and a target ID wherein the target ID may be associated with a target RAN. 
     Example 19 may include the device of example 16 and/or some other example herein, wherein the processing circuitry may be further configured to: cause to send a create indirect data forwarding tunnel request message to a source UPF; and identify a create indirect data forwarding tunnel response from the source UPF. 
     Example 20 may include the device of example 16 and/or some other example herein, wherein the processing circuitry may be further configured to: identify a handover complete notification received from the AMF; and cause to send a handover complete acknowledgment addressed to the AMF. 
     Example 21 may include the device of example 16 and/or some other example herein, wherein the processing circuitry may be further configured to cause to send a modification request message to a PDU session anchor (PSA), wherein the modification request message may include a target user plane function (UPF) internet protocol (IP) address and a tunnel endpoint identification (TEID), the TEID being associated with the indirect data forwarding. 
     Example 22 may include the device of example 21 and/or some other example herein, wherein the first RAN may be a source RAN associated with the handover, and wherein the processing circuitry may be further configured to determine a target RAN associated with the handover. 
     Example 23 may include the device of example 22 and/or some other example herein, wherein the processing circuitry may be further configured to determine a source UPF associated with the source RAN and the target UPF associated with the target RAN. 
     Example 24 may include the device of example 21 and/or some other example herein, wherein the processing circuitry may be further configured to: cause to send a create an indirect data forwarding tunnel request message on a first interface to the target UPF; and identify a session establishment response message received from the target UPF. 
     Example 25 may include the device of example 24 and/or some other example herein, wherein the processing circuitry may be further configured to delete the indirect data forwarding tunnel to the target UPF. 
     Example 26 may include a non-transitory computer-readable medium storing computer-executable instructions which when executed by one or more processors result in performing operations comprising: determine an association with a first radio access network (RAN); cause to send a handover request message to a session management function (SMF); cause to send a request to establish an indirect data forwarding associated with the handover, wherein the request may be sent to the SMF; and identify a response received from the SMF indicating that the indirect data forwarding may be established. 
     Example 27 may include the non-transitory computer-readable medium of example 26 and/or some other example herein, wherein the handover request message may include a protocol data unit (PDU) session ID and a target ID wherein the target ID may be associated with a target RAN. 
     Example 28 may include the non-transitory computer-readable medium of example 26 and/or some other example herein, wherein the operations further comprise causing to send a create indirect data forwarding tunnel request message to the SMF. 
     Example 29 may include the non-transitory computer-readable medium of example 26 and/or some other example herein, wherein the operations further comprise identifying a create indirect data forwarding tunnel response message from the SMF. 
     Example 30 may include a method comprising: determining, by one or more processors of a device, an association of an access and mobility management function (AMF) with a first radio access network (RAN); identifying a handover request message received from the first RAN via the AMF; identifying a request to establish an indirect data forwarding associated with the handover, wherein the request may be received from the first RAN via the AMF; and causing to send a response addressed to the AMF indicating that the indirect data forwarding may be established. 
     Example 31 may include the method of example 30 and/or some other example herein, wherein the device may be a session management function (SMF), wherein the SMF may be communicatively coupled to at least one of a first user plane function (UPF) and a second UPF, the first UPF and the second UPF are associated with the handover. 
     Example 32 may include the method of example 30 and/or some other example herein, wherein the handover request message may include a protocol data unit (PDU) session ID and a target ID wherein the target ID may be associated with a target RAN. 
     Example 33 may include the method of example 30 and/or some other example herein, further comprises: causing to send a create indirect data forwarding tunnel request message to a source UPF; and identifying a create indirect data forwarding tunnel response from the source UPF. 
     Example 34 may include the method of example 30 and/or some other example herein, further comprises: identifying a handover complete notification received from the AMF; and causing to send a handover complete acknowledgment to the AMF. 
     Example 35 may include the method of example 30 and/or some other example herein, further comprises causing to send a modification request message to a PDU session anchor (PSA), wherein the modification request message may include a target user plane function (UPF) Internet protocol (IP) address and a tunnel endpoint identification (TEID), the TEID being associated with the indirect data forwarding. 
     Example 36 may include the method of example 35 and/or some other example herein, further comprises determining a target RAN associated with the handover, and wherein the first RAN may be a source RAN associated with the handover. 
     Example 37 may include the method of example 36 and/or some other example herein, further comprises determining a source UPF associated with the source RAN and the target UPF associated with the target RAN. 
     Example 38 may include the method of example 35 and/or some other example herein, further comprises: causing to send a create an indirect data forwarding tunnel request message on a first interface to the target UPF; and identifying a session establishment response message received from the target UPF. 
     The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of embodiments to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments.

Metadata:
Filing Date: 20180724
Publication Date: 20240109
Grant Date: 20240109
Priority Date: 20170804
Inventors: SHAN, CHANGHONG
Yu, Yifan
STOJANOVSKI, Alexandre Saso
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W36/322", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W36/0019", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W36/0064", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W36/32", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W8/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W36/0011", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W36/0055", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W36/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W76/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W92/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W76/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W8/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W36/0019", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W36/0064", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W36/322", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 65234172