5g multicast broadcast service handover

Abstract

Systems and methods for session continuity for multicast broadcast (MB) sessions are provided. In some embodiments, a method for session continuity for MB sessions performed by a base station includes at least one of: providing at least one MB session to a wireless device connected with a 5G; determining that the wireless device is handed over to a target next generation radio access network (NG-RAN); and providing session continuity for the at least one MB session to the wireless device. In some embodiments, the handover to the target NG-RAN includes an Xn handover. In some embodiments, the handover to the target NG-RAN includes an N2 handover. Some embodiments of the present disclosure provide support for multicast broadcast session continuity (aka "handover") upon inter-gNB Xn handover and inter-gNB N2 handover in 5G NR radio access.

Description

[0001] Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 029,116, filed May 22, 2020, the disclosure of which is incorporated herein in its entirety by reference. TECHNICAL FIELD

[0003] The present disclosure relates to multicast broadcast sessions. BACKGROUND

[0004] The 3rd Generation Partnership Project (3GPP) developed Multicast / Broadcast Multimedia Subsystem (MBMS) for video multicast / broadcast and streaming services early on for 3G networks (see 3GPP TS 23.246 v16.1.0) and later introduced evolved MBMS (eMBMS) for Evolved Packet System (EPS). In Release 13 and Release 14, the MBMS system has been updated to support new services such as public safety, Cellular Internet of Things (CIoT), and Vehicle-to-Everything (V2X).

[0005] The scope of the new Release 17 study by the 3GPP SA2 working group is to study both multicast requirements and use cases for CIoT, public safety, V2X, etc. and dedicated broadcast requirements and use cases. The study is for 5G Release 17 and New Radio (NR) radio access. The results of the study to date have been documented in TR 23.757 V0.3.0.

[0006] There are some challenges at present. So far, multicast / broadcast services are not supported on 5G NR. With the enhanced features of 5G NR (e.g., short latency, bandwidth, etc.), it is believed that mission critical services (Mission Critical Push To Talk (MCPTT), Mission Critical Data (MCData), and Mission Critical Video (MCVideo) and VTX services will perform much better on 5G NR with enhanced performance.

[0007] For 5G MBS multicast support, the 5G system (5GS) must support UE mobility. Session continuity during handover (i.e., Xn handover and N2 handover) is a requirement. The existing procedures in TS 23.502 v16.4.0, section 4.9.1.2, “Xn based inter NG-RAN handover” and section 4.9.1.3, “Inter NG-RAN node N2 based handover” need to be enhanced to support 5MBS and MB sessions during handover. 5MBS study is documented in TR 23.757 V0.3.0, but so far no solution on handover has been documented. Improved systems and methods for session continuity for MB sessions are needed. SUMMARY

[0008] Systems and methods for session continuity for MB sessions are provided. In some embodiments, a method for session continuity for a multicast broadcast (MB) session performed by a base station includes at least one of: providing at least one MB session to a wireless device connected with 5G; determining that the wireless device is handed over to a target next generation radio access network (NG-RAN); and providing session continuity for the at least one MB session to the wireless device.

[0009] In some embodiments, the handover to the target NG-RAN includes an Xn handover. In some embodiments, the handover to the target NG-RAN includes an N2 handover.

[0010] Some embodiments of the present disclosure provide support for multicast broadcast session continuity (aka “handover”) at inter-gNB Xn handover and inter-gNB N2 handover in 5G NR radio access.

[0011] In some embodiments, a method for session continuity for a MB session performed by a base station includes at least one of: providing at least one MB session to a wireless device connected with 5G; determining that the wireless device is handed over to a target next generation radio access network (NG-RAN); and providing session continuity for the at least one MB session to the wireless device.

[0012] In some embodiments, a method for session continuity for a MB session performed by a base station includes at least one of: receiving a handed over wireless device that is receiving at least one MB session; and providing session continuity for the at least one MB session to the wireless device.

[0013] In some embodiments, the method further comprises causing resources to be established in the target NG-RAN at an Xn handover preparation phase. In some embodiments, the method further comprises causing resources to be established in the target NG-RAN at an Xn handover execution phase.

[0014] In some embodiments, the method further comprises notifying and / or triggering an Access and Mobility Management Function, AMF, to start establishing MB session resources in the NG-RAN. In some embodiments, the notification and / or triggering comprises a MB session command. In some embodiments, the notification and / or triggering comprises a new parameter to an existing path switch request and / or path switch request acknowledge message.

[0015] In some embodiments, a new parameter “Temporary Mobile Group Identity, TMGI” (or list of TMGIs) is included in the existing path switch request message.

[0016] In some embodiments, the handover to the target NG-RAN comprises an N2 handover.

[0017] In some embodiments, the method further comprises causing resources to be established in the target NG-RAN at an N2 handover preparation phase.

[0018] In some embodiments, the method further comprises releasing resources if this is the last wireless device leaving the MB session.

[0019] Certain aspects of the present disclosure and their embodiments can provide solutions to the above-described or other challenges. Particular parts of the 5MBS procedure are included in other publications. Some publications include 5MBS Radio Access Network - Fifth Generation Core (RAN-5GC) interactions. PCT / EP2020 / 055482 application includes Access and Mobility Management Function (AMF) service discovery for MB-Session Management Function (SMF). BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which are incorporated in and form a part of the specification, illustrate several aspects of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0021] Figure 1 One example of a cellular communication system 100 in which embodiments of the present disclosure can be implemented is shown;

[0022] Figure 2 One wireless communication system is shown, representing a 5G network architecture composed of core network functions, NFs, where the interaction between any two NFs is represented by a point-to-point reference point / interface;

[0023] Figure 3A 5G network architecture is shown that uses service-based interfaces between NFs in the CP, rather than Figure 2 point-to-point reference points / interfaces used in the 5G network architecture of

[0024] Figure 4 A method performed by a wireless device for session continuity for an MB session is shown in accordance with some embodiments of the disclosure;

[0025] Figure 5 A method performed by a base station for session continuity for an MB session is shown in accordance with some embodiments of the disclosure;

[0026] Figure 6 Example embodiments for inter-gNB Xn handover are shown in accordance with some embodiments of the disclosure;

[0027] Figure 7 Example embodiments for inter-NG RAN node N2-based handover are shown in accordance with some embodiments of the disclosure;

[0028] Figure 8 Example embodiments for inter-NG RAN node N2-based handover are shown in accordance with some embodiments of the disclosure;

[0029] Figure 9 is a schematic block diagram of a radio access node according to some embodiments of the disclosure;

[0030] Figure 10 is a schematic block diagram illustrating a virtualized embodiment of a radio access node according to some embodiments of the disclosure;

[0031] Figure 11 is a schematic block diagram of a radio access node according to some other embodiments of the disclosure;

[0032] Figure 12 is a schematic block diagram of a wireless communication device according to some embodiments of the disclosure;

[0033] Figure 13 is a schematic block diagram of a wireless communication device 1200 according to some other embodiments of the disclosure;

[0034] Figure 14 A communication system is shown comprising a telecommunication network such as a 3GPP-type cellular network including an access network such as a RAN and a core network in accordance with some embodiments of the disclosure;

[0035] Figure 15 A communication system is shown comprising a host computer in accordance with some embodiments of the disclosure; and

[0036] Figures 16 to 19 is a flowchart illustrating a method implemented in a communication system according to some embodiments of the disclosure. DETAILED DESCRIPTION

[0037] The embodiments set forth below depict information that enables a person skilled in the art to practice the embodiments and demonstrate the best mode of practicing them. The embodiments are based on information available prior to the filing date of this application and, as such, are not intended to limit the scope of the disclosure, which is limited only by the claims that follow this disclosure. The skilled person will understand that the concepts disclosed herein have application in a wide variety of contexts.

[0038] Radio node: As used herein, a “radio node” is a radio access node or a wireless communication device.

[0039] Radio access node: As used herein, a “radio access node” or “radio network node” or “radio access network node” is any node of a radio access network (RAN) of a cellular communications network that operates to transmit and / or receive signals wirelessly. Some examples of radio access nodes include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high- power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, etc.), a relay node, a network node that implements part of the functionality of a base station (e.g., a network node that implements a gNB central unit (gNB-CU) or a network node unit that implements a gNB distributed unit (gNB-DU)), or a network node that implements part of the functionality of some other type of radio access node.

[0040] Core network node: As used herein, a “core network node” is any type of node in a core network or any node that implements core network functionality. Some examples of core network nodes include, for example, a mobility management entity (MME), a packet data network gateway (P-GW), a service capability exposure function (SCEF), a home subscriber server (HSS), etc. Some other examples of core network nodes include nodes that implement the following functions: an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), an authentication server function (AUSF), a network slice selection function (NSSF), a network exposure function (NEF), a network function (NF) repository function (NRF), a policy control function (PCF), a unified data management (UDM), etc.

[0041] Communication Device: As used herein, a “communication device” is any type of device that has access to an access network. Some examples of a communication device include, but are not limited to: mobile phones, smartphones, sensor devices, meters, vehicles, household appliances, medical appliances, media players, cameras, or any type of consumer electronic device such as, but not limited to, television, radios, lighting arrangements, tablet computer, laptop, or personal computer (PC). A communication device can be a portable, hand-held, computer- included, or car-mounted mobile device that communicates voice and / or data via a radio or wired connection.

[0042] Wireless Communication Device: One type of communication device is a wireless communication device, which can be any type of wireless device that has access to (i.e., is served by) a wireless network, examples of which are cellular networks. Some examples of a wireless communication device include, but are not limited to: a user equipment (UE) in a 3GPP network, a machine-type communication (MTC) device, and an Internet of Things (IoT) device. Such a wireless communication device can be or can integrate with a mobile phone, a smartphone, a sensor device, a meter, a vehicle, a household appliance, a medical appliance, a media player, a camera, or any type of consumer electronic device such as, but not limited to, a television, a radio, a lighting arrangement, a tablet computer, a laptop, or a PC. A wireless communication device can be a portable, hand-held, computer- included, or car-mounted mobile device that communicates voice and / or data via a wireless connection.

[0043] Network Node: As used herein, a “network node” is any node that is part of the RAN or core network of a cellular communications network / system.

[0044] Note that the description given herein focuses on 3GPP cellular communications systems, and thus often uses terminology that is 3GPP terminology or similar thereto. However, the concepts disclosed herein are not limited to 3GPP systems.

[0045] Note that in the description herein, the term “cell” can be mentioned; however, especially for 5G NR concepts, beams can be used instead of cells, and thus, it is important to note that the concepts described herein are equally applicable to both cells and beams.

[0046] Figure 1One example of a cellular communications system 100 in which embodiments of the present disclosure can be implemented is shown. In the embodiments described herein, the cellular communications system 100 is a 5G system (5GS) comprising a Next Generation RAN (NG-RAN) and a 5G Core (5GC). In this example, the RAN comprises base stations 102-1 and 102-2, which in the 5GS comprise NR base stations (gNBs), and optionally Next Generation eNBs (ng-eNBs) (e.g., LTE RAN nodes connected to the 5GC), with the base stations 102-1 and 102-2 controlling corresponding (macro) cells 104-1 and 104-2. The base stations 102-1 and 102-2 are generally referred to herein collectively as base stations 102 and individually as base station 102. Likewise, the macro cells 104-1 and 104-2 are generally referred to herein collectively as macro cells 104 and individually as macro cell 104. The RAN can also include a number of low power nodes 106-1 through 106-4 controlling corresponding small cells 108-1 through 108-4. The low power nodes 106-1 through 106-4 can be small base stations (e.g., pico or femto base stations) or Remote Radio Heads (RRHs), among others. Notably, while not shown, one or more of the small cells 108-1 through 108-4 can alternatively be provided by the base stations 102. The low power nodes 106-1 through 106-4 are generally referred to herein collectively as low power nodes 106 and individually as low power node 106. Likewise, the small cells 108-1 through 108-4 are generally referred to herein collectively as small cells 108 and individually as small cell 108. The cellular communications system 100 also includes a core network 110, which in the 5G system (5GS) is referred to as a 5GC. The base stations 102 (and optionally the low power nodes 106) connect to the core network 110.

[0047] The base stations 102 and the low power nodes 106 serve corresponding cells 104 and 108 to wireless communication devices 112-1 through 112-5. The wireless communication devices 112-1 through 112-5 are generally referred to herein collectively as wireless communication devices 112 and individually as wireless communication device 112. In the following description, the wireless communication devices 112 are often a UE, but the present disclosure is not limited to this.

[0048] Figure 2 A wireless communication system is shown representing a 5G network architecture composed of core network functions (NFs), where the interaction between any two NFs is represented by a point-to-point reference point / interface. Figure 2 The system 100 can be considered as Figure 1 one particular implementation of the system 100.

[0049] From an access side, Figure 2The 5G network architecture shown in FIG. 1 includes a plurality of UEs 112 connected to a RAN 102 or access network (AN) and an AMF 200. Generally, the R(AN) 102 includes a base station, e.g., a base station such as an eNB or gNB. From the core network side, Figure 2 The 5GC NFs shown include an NSSF 202, an AUSF 204, a UDM 206, an AMF 200, an SMF 208, a PCF 210, and an application function (AF) 212.

[0050] In the specification standardization, reference points of the 5G network architecture are used to develop detailed call flows. The N1 reference point is defined for carrying signaling between a UE 112 and an AMF 200. The reference points for the connection between an AN 102 and an AMF 200 and between an AN 102 and a UPF 214 are defined as N2 and N3, respectively. There is a reference point N11 between an AMF 200 and an SMF 208, which means that the SMF 208 is at least partially controlled by the AMF 200. N4 is used by an SMF 208 and a UPF 214 so that the UPF 214 can be set using control signals generated by the SMF 208, and the UPF 214 can report its status to the SMF 208. N9 is the reference point for the connection between different UPFs 214, and N14 is the reference point for the connection between different AMFs 200, respectively. N15 and N7 are defined because a PCF 210 applies policies to an AMF 200 and an SMF 208, respectively. An AMF 200 needs N12 to perform authentication of a UE 112. N8 and N10 are defined because the AMF 200 and the SMF 208 need subscription data of a UE 112.

[0051] The 5GC network aims to separate the UP and the CP. The UP carries user traffic, while the CP carries signaling in the network. In Figure 2 In the 5GC, the UPF 214 is in the UP, while all other NFs, i.e., the AMF 200, the SMF 208, the PCF 210, the AF 212, the NSSF 202, the AUSF 204, and the UDM 206, are in the CP. Separating the UP and the CP ensures that each plane resource can be scaled independently. It also allows the UPF to be deployed in a distributed manner separate from the CP functions. In this architecture, the UPF can be deployed very close to the UE to shorten the round-trip time (RTT) between the UE and the data network for some applications that require low latency.

[0052] The core 5G network architecture is composed of modularized functions. For example, the AMF 200 and the SMF 208 are independent functions in the CP. The separate AMF 200 and SMF 208 allow independent evolution and scaling. Other CP functions, such as the PCF 210 and the AUSF 204, can be separated as shown. Figure 2 The modularized function design enables the 5GC network to flexibly support various services.

[0053] Each NF interacts directly with another NF. Messages can be routed from one NF to another NF using intermediate functions. In the CP, a set of interactions between two NFs is defined as a service so that it can be reused. This service implementation supports modularity. The UP supports interactions such as forwarding operations between different UPFs.

[0054] Figure 3 One 5G network architecture is shown, which uses service-based interfaces between NFs in the CP instead of Figure 2 the point-to-point reference points / interfaces used in the 5G network architecture. However, the NFs described above with reference to Figure 2 correspond to the NFs shown in Figure 3 . The services provided by the NFs to other authorized NFs can be exposed to the authorized NFs through the service-based interfaces. In Figure 3 , the service-based interfaces are denoted by the letter “N” followed by the name of the NF, for example, the service-based interface of the AMF 200 is denoted as Namf, the service-based interface of the SMF 208 is denoted as Nsmf, and so on. Figure 3 The NEF 300 and the NRF 302 in Figure 2 are not shown in the above-discussed Figure 2 . However, it should be clarified that although Figure 2 is not explicitly indicated in Figure 3 , all the NFs depicted in may interact with the NEF 300 and the NRF 302 in

[0055] as needed. Figure 2 and 3Some of the properties of the NFs shown in the middle. The AMF 200 provides UE-based authentication, authorization, mobility management, etc. The UE 112 is basically connected to a single AMF 200 even if it uses multiple access technologies, because the AMF 200 is independent of the access technology. The SMF 208 is responsible for session management and allocates an Internet Protocol (IP) address to the UE. It also selects and controls the UPF 214 for data transfer. If the UE 112 has multiple sessions, a different SMF 208 can be allocated to each session to manage them separately and possibly provide different functions for each session. The AF 212 provides information on packet flow to the PCF 210 responsible for policy control to support Quality of Service (QoS). Based on the information, the PCF 210 determines policies regarding mobility and session management to enable the AMF 200 and the SMF 208 to function normally. The AUSF 204 supports authentication functions for the UE and the like, so it stores data for authentication and the like of the UE, while the UDM 206 stores subscription data of the UE 112. The Data Network (DN) is not part of the 5GC network, and the DN provides Internet access or operator services, etc.

[0056] The NFs can be implemented as network elements on dedicated hardware, as software instances running on dedicated hardware, or as virtualized functions instantiated on an appropriate platform, e.g., a cloud infrastructure.

[0057] For 5G MBS multicast support, the 5G system (5GS) must support UE mobility. Session continuity during handover (i.e., Xn handover and N2 handover) is a requirement. The existing procedures in TS 23.502 v16.4.0 Section 4.9.1.2 “Xn based inter NG-RAN handover” and Section 4.9.1.3 “Inter NG-RAN node N2 based handover” need to be enhanced to support 5MBS and MB sessions during handover. 5MBS study is documented in TR 23.757 V0.3.0, but so far no solution on handover has been documented. Improved systems and methods for session continuity for MB sessions are needed.

[0058] Systems and methods for session continuity for multicast broadcast (MB) sessions are provided. In some embodiments, a method for session continuity for MB sessions performed by a base station includes at least one of: providing at least one MB session to a wireless device connected with a 5G; determining that the wireless device is handed over to a target next generation radio access network (NG-RAN); and providing session continuity for the at least one MB session to the wireless device. In some embodiments, the handover to the target NG-RAN includes an Xn handover. In some embodiments, the handover to the target NG-RAN includes an N2 handover. Some embodiments of the present disclosure provide support for multicast broadcast session continuity (aka "handover") at inter-gNB Xn handover and inter-gNB N2 handover in 5G NR radio access.

[0059] The present disclosure has two major categories of embodiments: 5MBS Xn handover and 5MBS N2 handover. Details about some implementations of these embodiments are included below.

[0060] Certain embodiments can provide one or more of the following technical advantages. Advantages of the Xn embodiments:

[0061] • Enhanced 5G Xn handover procedure (TS 23.502 v16.4.0 Section 4.9.1.2) to support session continuity (aka "handover") for 5G MB sessions.

[0062] • Resources in the target NG-RAN are already established at the Xn handover preparation phase (see Step 2 description for "Option 1"). This means that when the UE is handed over to a new cell in the target NG-RAN, the UE is able to start immediately receiving the 5MBS media stream in the new cell. That is, the service continuity feature will be excellent, and the gap in media reception is minimal or none.

[0063] • Resources in the target NG-RAN can optionally be established at the Xn handover execution phase (see Step 10 description for "Option 2"). This Option 2 can be an alternative way, e.g., when moving from a source NG-RAN that does not support 5MBS to a target NG-RAN that supports 5MBS, or for better system robustness, but it can also be a complementary way. With Option 2, the service continuity feature (i.e., the gap in media reception) will be slightly worse, but it can still be acceptable for most use cases.

[0064] • A new message MB Session Command (TMGI) in Step 2a by which the NG-RAN informs and triggers the AMF to start establishing MB session resources in the NG-RAN.

[0065] • New parameter enhancements to the existing Path Switch Request and Path Switch Request Acknowledge messages (step 9) can reduce the signaling between the AMF and NG-RAN (step 10a / “MB Session Join” message can be replaced by adding new corresponding parameters (NGAP ID and TMGI) to the Path Switch Request Acknowledge message).

[0066] Furthermore, including a new parameter “TMGIs” (or TMGI list) in the existing Path Switch Request message can enable the AMF to know whether the NG-RAN already knows that the UE has joined the MB session, in which case the MB Session Join step 10a is not needed.

[0067] • If this is the last UE leaving the MB session in the source NG-RAN node, release resources in that node (step 8)

[0068] Advantages of the N2 embodiment:

[0069] • The enhanced 5G N2 handover procedure (TS 23.502 v16.4.0 section 4.9.1.3) to support session continuity (i.e. “handover”) of 5G MB sessions.

[0070] • The resources in the T-NG-RAN have already been established in the N2 handover preparation phase. This means that when the UE switches to a new cell in the T-NG-RAN (i.e. in step 4) in the execution phase, the UE is able to start receiving the 5MBS media stream in the new cell immediately. That is, the service continuity feature will be excellent, and the gap in media reception is minimal or none.

[0071] • If this is the last UE leaving the MB session in the S-NG-RAN node, release resources in that node (step 14c in section 4.9.1.3.3).

[0072] Figure 4 A method performed by a wireless device for session continuity of MB sessions according to some embodiments of the present disclosure is shown. In some embodiments, the method includes at least one of: receiving at least one MB session while connected in 5G (step 400); switching to a target NG-RAN (step 402); and optionally, continuing to receive the at least one MB session (404).

[0073] Figure 5A method performed by a base station for session continuity for MB sessions is shown in accordance with some embodiments of the disclosure. In some embodiments, the method includes at least one of: providing at least one MB session to a wireless device connected with a 5G (step 500); determining that the wireless device is being handed over to a target NG-RAN (step 502); and optionally, providing session continuity for the at least one MB session to the wireless device (step 504).

[0074] In this way, some embodiments provide support for multicast broadcast session continuity (aka "handover") at inter-gNB Xn handover and inter-gNB N2 handover in 5G NR radio access.

[0075] In some embodiments, there is Xn handover of the MB session. Note that in some embodiments, 5G MB sessions are not strictly handed over because they are shared. PDU sessions are not shared and are handed over. In some embodiments, the MB session is started in the target cell (if the MB session is not already active and used by other UEs in that cell), and in some embodiments, the MB session is released in the source cell (e.g., if this is the last UE listening to that MB session in that cell).

[0076] Some embodiments describe Xn handover for MB sessions for NR. Xn handover between RATs is not supported (e.g., Xn handover between NR and E-UTRA is not supported). Instead, session continuity is assumed to be handled at the application level, e.g., as described in TS 23.468 section 5.3 "Service Continuity".

[0077] The message names in the following procedures are descriptive. It is assumed that the corresponding SBI-based names are used to update the names when applicable in the specification phase. N2, N3 messages depend on RAN3 decisions.

[0078] For inter-gNB Xn handover: the target NG-RAN triggers the 5GC to establish any MB session resources that need to be established during the Xn handover preparation phase (which precedes the handover execution phase) (see Option 1 below). The UE will immediately continue to receive the media stream when it has synchronized to the new cell. This enables MB session continuity.

[0079] Alternatively, the AMF can be in charge of the establishment of MB session resources in the target NG-RAN after the UE is handed over to the target NG-RAN (see Option 2 below). Parameters in the Path Switch Request / Response messages can provide some optimizations. This option will result in a slightly larger gap in terms of MB session continuity, assuming that UE personal data forwarding does not apply to MB session user data.

[0080] In some embodiments, during Xn handover, the UE's PDU sessions are moved and connected to the new NG-RAN node. Unlike PDU sessions, MB sessions are never moved and connected to the target NG-RAN node. The transfer of data associated with MB sessions starts on the target NG-RAN node and is released on the source NG-RAN node, if needed.

[0081] For the complete sequence on Xn handover procedure, see section 4.9.1.2 in TS 23.502 [x] and section 9.2.3 in TS 38.300 [y].

[0082] Figure 6 An example embodiment for inter-gNB Xn handover is shown in accordance with some embodiments of the present disclosure.

[0083] 0. Media flow to source NG-RAN and PTM / PTP transmission to the UE are ongoing. The source NG-RAN triggers handover (see steps 0 to 2 in section 9.2.3.2.1 in TS 38.300 [x]).

[0084] 1. The source NG-RAN sends an Xn handover request to the target NG-RAN. The UE context contains MB session information.

[0085] 2. Option 1: The source NG-RAN informs the target NG-RAN of any MB session resources that need to be established. The MB session information for MB sessions that the UE has joined is included in the Xn handover request message with a list of {TMGI, active / non-active indicator, LL MC address}. In some embodiments, the Temporary Mobile Group Identity (TMGI) is a radio resource efficient mechanism for identifying MBMS bearer services (as opposed to using IP multicast address and Access Point Name).

[0086] If Option 1 is used and for any TMGI in the list in step 1, the target NG-RAN does not have an active MB session Ctx:

[0087] 2a. The target NG-RAN declares its interest in the MB session by sending an MB session command (TMGI) to the AMF.

[0088] 2b. If the MB session is set to the active state described above, the AMF sends an MB Session Resource Setup Request (TMGI, LL MC, 5G Granted QoS Profile) message to the NG-RAN node. The NG-RAN creates the MB session Ctxt if it does not exist yet, sets it to active, stores the TMGI, 5G Granted QoS Profile and AMF ID in the MB session Ctxt. When the resources have been successfully set up, the NG-RAN node returns an MB Session Resource Setup Response (TMGI) message to the AMF. The AMF stores the NG-RAN ID of the target NG-RAN node in the AMF MB session Ctxt.

[0089] 2c. The target NG-RAN joins the multicast group (i.e. the LL MC address) of the new active MB session.

[0090] 3. For an active MB session, resources can be configured for the UE switching from source to target to transmit the media stream by the target NG-RAN. If there are already other UEs joining the active MB session in the target NG-RAN, then PTM / PTP transmission is also ongoing.

[0091] 4. The target NG-RAN sends an Xn Handover Request Acknowledge () to the source NG-RAN.

[0092] 5. The source NG-RAN sends a Uu Handover Command () to the UE. The UE starts accessing and synchronizing to the new cell.

[0093] 6. The target NG-RAN determines that the new UE in the cell should receive the media of one or more MB sessions and provides PTM / PTP transmission to the new UE. In some embodiments, optionally, the data transfer on PTM to the UE can have already started in step 3. The RAN makes the determination.

[0094] 7. The SN status is transferred to the target NG-RAN but not for the MB session. Forwarding of the PDU session can be performed.

[0095] 8. [Conditional] If the UE is the last UE leaving the MB session in the source NG-RAN, the source NG-RAN releases its resources for the MB session (see session leaving procedure).

[0096] 9. The target NG-RAN sends a Path Switch Request (TMGI) message to the AMF. If the target NG-RAN knows the TMGIs the UE has joined, they can be included in the request message. The AMF responds with a Path Switch Request Acknowledge () message.

[0097] In some embodiments, the RAN can decide to introduce a TMGI list parameter in the Path Switch Request Ack() message instead of the following step 10a.

[0098] 10. Option 2: The AMF determines whether MB session resources need to be established in the target NG-RAN by e.g. checking whether the NG-RAN ID of the target NG-RAN node is already stored in the AMF MB session Ctx and checking the status of the MB session Ctx. If it is in active status and not stored, steps 10a to 10c are performed.

[0099] 10a. When the AMF receives the Path Switch Request() message, the AMF sends an MB Session Join (NG-RAN ID, TMGI) message to the target NG-RAN for each TMGI that the AMF has in its UE context, unless the target NG-RAN already knows due to Option 1 (as indicated by the presence of TMGIs in the Path Switch Request message), then no MB Session Join message is sent.

[0100] 10b. If any TMGI in the AMF UE context has an MB session Ctx in active status and the AMF has not yet requested the target NG-RAN node to do resource establishment, the AMF sends an MB Session Resource Setup Request (TMGI, LL MC, 5G granted QoS profile) message to the target NG-RAN.

[0101] 10c. If there is no MB session Ctx for a TMGI in the target NG-RAN yet, the NG-RAN creates an MB session Ctx, sets it to active status, stores the list of TMGIs, QoS profiles and AMF IDs in the MB session Ctx and joins the multicast group (i.e. the LL MC address). Otherwise, the target NG-RAN only stores the AMF IDs in its MB session Ctx.

[0102] 11. If there is an MB session Ctx in active status for any TMGI of the new UE in the target NG-RAN, the target NG-RAN provides PTM / PTP transmission to the new UE (if it has not done so (in step 6)).

[0103] In some embodiments, support for Option 1 above is decided by the RAN. Option 1 can provide better session continuity characteristics at handover and reduce N2 signaling. In some embodiments, support for a TMGI parameter in the Path Switch Request message is decided by the RAN. When Option 1 is used, it can reduce the N2 session join signaling in step 10a. In some embodiments, support for a TMGI list parameter in the Path Switch Request Acknowledge message is decided by the RAN. It can reduce the N2 session join signaling in step 10a. If the RAN decides to use this TMGI-list parameter, then the parameter in the above note can not be needed. In some embodiments, Option 1 and Option 2 can be complementary and both can be standardized as depending on RAN decision.

[0104] In some embodiments, various impacts can occur to services, entities, and interfaces, for example:

[0105] UE: - receives multicast data using PTM / PTP under RRC connection. - receives handover from source NG-RAN to target NG-RAN when the Xn handover execution phase starts.

[0106] NG-RAN: - support of MB session information in Xn Handover Request (Option 1). - MB session resource setup during Xn handover preparation phase (Option 1). - MB session resource setup during Xn handover execution phase (Option 2). - new parameters in Path Switch message.

[0107] AMF: - support of new message that triggers MB session resource setup in NG-RAN during Xn handover preparation phase (Option 1).

[0108] In this way, some embodiments provide support for multicast broadcast session continuity (aka "handover") at inter-gNB Xn handover and inter-gNB N2 handover in 5G NR radio access.

[0109] In some embodiments, the handover occurs via N2 handover. During the N2 handover preparation phase, the source NG-RAN triggers the 5GC to setup any MB session resources that need to be setup. When the UE has synchronized to the new cell, the UE will immediately continue to receive the media stream. This enables MB session continuity.

[0110] The N2 handover solution is shown in TS 23.502 section 4.9.1.3 N2 handover procedure. In some cases, the proposed changes are shown in bold below.

[0111] Figure 7 An example embodiment for N2 based inter-NG RAN handover is shown in accordance with some embodiments of the present disclosure.

[0112] 0. MB media flow and PTM / PTP delivery can be ongoing in the 5GS, i.e. from the MB-UPF to the S-RAN to the UE.

[0113] 1. S-RAN to S-AMF: Handover required (Target ID, Source-to-Target transparent container, SM N2 information list, PDU Session ID, Intra-system handover indication).

[0114] The Source-to-Target transparent container includes NG-RAN information created by the S-RAN to be used by the T-RAN and is transparent to the 5GC.

[0115] 2. T-AMF selection: The S-AMF selects a T-AMF when it can no longer serve the UE as described in TS 23.501 section 6.3.5 on "AMF Selection Function" (see 3GPP 23.501 v16.4.0, hereafter [2]).

[0116] 3. [Conditional] S-AMF to T-AMF: Namf_Communication_CreateUEContext request (N2 information (Target ID, Source-to-Target transparent container, SM N2 information list, PDU Session ID), UE Context Information (SUPI, Service Area Restrictions, Allowed NSSAI per access type (if available), Trace requirements, LTE M indication, list of PDU Session IDs and corresponding SMF information and corresponding S-NSSAI, PCF ID, DNN, UE Radio Capability ID, and UE Radio Capability Information). If the subscription information includes Trace requirements, the old AMF provides the Trace requirements to the target AMF.

[0117] In case of inter-PLMN mobility, the UE Context Information includes the HPLMN S-NSSAIs corresponding to the allowed NSSAI per access type, and does not include the allowed NSSAI of the source PLMN. The target AMF can determine the allowed NSSAI based on the HPLMN S-NSSAIs received in step 3, or the target AMF queries the NSSF by invoking the Nnssf_NSSelection_Get service operation using the HPLMN S-NSSAIs and the PLMN ID of the SUPI. The target AMF can trigger AMF reallocation when performing a mobility registration update during the handover execution phase, as described in section 4.2.2.2.3.

[0118] The S-AMF initiates the handover resource allocation procedure by invoking the Namf_Communication_CreateUEContext service operation to the T-AMF.

[0119] This step and step 12 are not needed when the S-AMF is still able to serve the UE.

[0120] If the service area restrictions are available in the S-AMF, the service area restrictions can be forwarded to the T-AMF as described in section 5.3.4.1.2 in TS 23.501 [2].

[0121] If the S-AMF provides a home PCF ID and an accessed PCF ID, the T-AMF contacts the (V-)PCF identified by the (V-)PCF ID. If the (V-)PCF identified by the (V-)PCF ID is not used or there is no PCF ID received from the S-AMF, the T-AMF can select a PCF as described in section 6.3.7.1 in TS 23.501 [2] and according to the V-NRF to H-NRF interaction described in section 4.3.2.2.3.3. The T-AMF informs the S-AMF that the PCF ID is not used as defined in step 12, then the S-AMF terminates the association of the AM policy with the PCF identified by the PCF ID.

[0122] 4-7. [Conditional] T-AMF to SMF: Nsmf_PDUSession_UpdateSMContext (PDU Session ID, Target ID, T-AMF ID, N2 SM information).

[0123] 7a. [Conditional] For each TMGI in the AMF UE context: T-AMF to MB-SMF: Nmbsmf_MBSession_UpdateMBContext (TMGI, T-AMF ID).

[0124] The MB-SMF stores the T-AMF ID in the list of AMF IDs in the MB-SMF MB session context. If the T-AMF is new in the list, i.e. the T-AMF does not have yet a MB session and the MB-SMF MB session status is "active", the MB-SMF prepares to send a MB session start notification to the AMF (step 7c).

[0125] 7b. MB-SMF to T-AMF: Nmbsmf_MBSession_UpdateMBContext response (TMGI).

[0126] The MB-SMF includes N2 MB information in the Nmbsmf_MBSession_UpdateMBContext response, which contains the lower layer multicast address (LL MC) allocated for the MB session and used by the MB-UPF, and the QoS profile indicating that the N2 SM information is for 5G authorized for the target NG-RAN. In some embodiments, the T-AMF creates the MB session context and sets its status to "inactive".

[0127] 7c. If the T-AMF is new in the MB-SMF list and the MB session is "active" in step 7a, the MB-SMF sends Nmbsmf_MBSession_UpdateMBContext start (i.e. MB session start) to the AMF. The T-AMF updates its MB session context and sets the status to "active".

[0128] 7d to 7t. The T-AMF sends the MB session resource setup request message to the T-NG-RAN. See the MB session start procedure. The handover incoming indicator is included in the MB session resource setup request message to avoid the NG-RAN releasing resources because there can be no UE interested in this TMGI at this time.

[0129] 8. The AMF supervises the Nsmf_PDUSession_UpdateSMContext response messages from the involved SMFs. The minimum value of the maximum delay indication for the PDU sessions that are candidates for handover gives the longest time the AMF can wait for the Nsmf_PDUSession_UpdateSMContext response messages before continuing the N2 handover procedure. When the maximum waiting time expires or when all Nsmf_PDUSession_UpdateSMContext response messages are received, the AMF continues the N2 handover procedure (handover request message in step 9). For the UE that has joined one or more MB sessions, the T-AMF does not need to wait for the Nmbsmf_MBSession_UpdateMBContext response because these MB sessions can be executed in parallel with the N2 handover procedure.

[0130] In some embodiments, the delay value per PDU session is locally configured in the AMF and implementation specific.

[0131] 9. T-AMF to T-RAN: Handover Request (source to target transparent container, N2 MM information, N2 SM information list, trace requirements, UE radio capability ID). If the subscription information includes trace requirements, the target AMF provides the trace requirements for the target RAN in the handover request.

[0132] The T-AMF determines the T-RAN based on the target ID. The T-AMF can allocate the 5G-GUTI valid for the UE in this AMF and target TAI.

[0133] The source to target transparent container received from the S-RAN is forwarded. The N2 MM information includes e.g. security information and mobility restriction list (if available in the T-AMF).

[0134] The N2 SM information list includes the N2 SM information received from the SMF for the T-RAN in the Nsmf_PDUSession_UpdateSMContext response message received within the maximum allowed delay supervised by the T-AMF mentioned in step 8.

[0135] The mobility restriction list is sent in the N2 MM information (if available in the target AMF).

[0136] If the UE radio capability ID is included in the handover request message, when there is no corresponding UE radio capability set for the UE radio capability ID at the T-RAN, the T-RAN shall request the T-AMF to provide the T-RAN with the UE radio capability set corresponding to the UE radio capability ID.

[0137] 10. T-RAN to T-AMF: Handover request acknowledgement (target to source transparent container, list of PDU sessions to be switched with N2 SM information, list of PDU sessions that failed to setup (with failure cause given in N2 SM information element)).

[0138] The target to source transparent container includes a UE container with access stratum part and NAS part. The UE container is transparently sent to the UE via the T-AMF, S-AMF and S-RAN.

[0139] The T-RAN creates the list of PDU sessions that failed to setup and the failure cause (e.g. T-RAN decision, S-NSSAI not available, unable to complete user plane security implementation) based on the T-RAN determination. The information is provided to the S-RAN.

[0140] The N2 SM information in the list of PDU sessions to be switched contains the T-RAN N3 addressing information per PDU session ID, i.e. the T-RAN's N3 UP address and tunnel ID for the PDU session.

[0141] If redundant transmission is performed for one or more QoS flows of a PDU Session, the T-RAN provides two pieces of AN tunnel information for the PDU Session in the N2 SM information. The T-RAN indicates to the SMF that one of the AN tunnel information is used as a redundant tunnel for the PDU Session as described in section 5.33.2.2 of TS 23.501 [2]. If the target NG-RAN only provides one piece of AN tunnel information for the PDU Session, the SMF can release these QoS flows after the handover procedure by triggering a PDU Session modification procedure as specified in section 4.3.3.

[0142] The N2 SM information can also include: - an indication whether UP integrity protection is performed for the PDU Session. - the N3 UP address and tunnel ID of the T-RAN for receiving the forwarded data (if the PDU Session has at least one QoS flow for data forwarding). The T-RAN provides the data forwarding address for each data forwarding tunnel it decides to establish. - for each QoS flow accepted using an alternative QoS profile (see TS 23.501 [2]), the target NG-RAN shall include a reference to the completed alternative QoS profile.

[0143] 11a-f. AMF to SMF: Nsmf_PDUSession_UpdateSMContext request.

[0144] 12. [Conditional] T-AMF to S-AMF: Namf_Communication_CreateUEContext response (N2 information needed by the S-AMF to send the handover command to the S-RAN, which includes the target-to-source transparent container, the list of PDU Sessions that failed to establish, the N2 SM information (N3 DL forwarding information, PCF ID)).

[0145] The AMF supervises the Nsmf_PDUSession_UpdateSMContext response messages from the involved SMFs. When the maximum waiting time expires or when all Nsmf_PDUSession_UpdateSMContext response messages are received, the T-AMF sends the Namf_Communication_CreateUEContext response to the S-AMF.

[0146] The list of PDU Sessions that failed to establish includes the list of PDU Sessions that failed to establish received from the target RAN in step 10 and the list of PDU Sessions that were not accepted generated by the T-AMF.

[0147] The list of PDU Sessions that were not accepted includes the following PDU Sessions with the appropriate cause value:

[0148] - PDU session not accepted by the SMF;

[0149] - PDU session not accepted by the AMF due to no response from the SMF within the maximum wait time; and

[0150] - PDU session not accepted by the AMF due to unavailable S-NSSAI in the T-AMF decided at step 4.

[0151] Target-to-source transport container is received from the T-RAN. N2 SM context is received from the SMF in step 1 If.

[0152] Execution phase

[0153] Figure 8 An example embodiment for N2 based handover between NG RAN nodes is shown in accordance with some embodiments of the present disclosure. For brevity, registration of the service AMF with the UDM is not shown in the figure.

[0154] 1. S-AMF to S-RAN: Handover Command (Target-to-source transparent container, list of PDU sessions to be handed over with N2 SM information (which contains information received from the T-RAN during the handover preparation phase), list of PDU sessions with establishment failure).

[0155] Target-to-source transparent container received from the S-AMF is forwarded.

[0156] The SM forwarding information list includes either the T-RAN SM N3 forwarding information list for direct forwarding or the S-UPF SM N3 forwarding information list for indirect data forwarding.

[0157] The S-RAN uses the list of PDU sessions with establishment failure and the indicated failure cause to decide whether to continue with the N2 handover procedure.

[0158] If the S-RAN receives a reference to an alternative QoS profile for a QoS flow that has been accepted, it shall take this into account in deciding whether to continue with the N2 handover procedure (see TS 23.501 [2]).

[0159] 2. S-RAN to UE: Handover Command (UE container).

[0160] The UE container is the UE part of the target-to-source transparent container, which is transparently sent from the T-RAN to the S-RAN via the AMF and provided by the S-RAN to the UE.

[0161] 2a0. If the PLMN has configured the assistance RAT usage reporting and the source NG-RAN has assistance RAT usage data to report, the source NG-RAN node can provide the AMF with a RAN usage data report message (N2 SM information (assistance RAT usage data), Handover flag) as in section 4.21. The Handover flag indicates to the AMF that it should buffer the N2 SM information containing the usage data report before forwarding.

[0162] This step is not shown in this figure, but the assistance RAT usage data reporting procedure is shown in section 4.21 Figure 4 .21-1.

[0163] 2a to 2c. The S-RAN sends an uplink RAN state transfer message to the S-AMF as specified in TS 36.300

[46] and TS 38.300 [9]. The S-RAN can omit sending this message if no radio bearers of the UE shall be handled using PDCP state saving.

[0164] If there is an AMF relocation, the S-AMF sends this information to the T-AMF via the Namf_Communication_N1N2MessageTransfer service operation and the T-AMF acknowledges. The S-AMF or (in case of AMF being relocated) the T-AMF sends this information to the T-RAN via a downlink RAN state transfer message as specified in TS 36.300

[46] and TS 38.300 [9].

[0165] 3. Uplink packets are sent from the T-RAN to the T-UPF and the UPF (PSA). Downlink packets are sent from the UPF (PSA) to the S-RAN via the S-UPF. The S-RAN shall start forwarding downlink data from the S-RAN to the T-RAN for the QoS flows or DRBs used for data forwarding. This can be direct forwarding (step 3a) or indirect forwarding (step 3b).

[0166] 4. UE to T-RAN: Handover confirm.

[0167] After the UE has successfully synchronised to the target cell, the UE sends a handover confirm message to the T-RAN. With this message, the UE considers the handover to be successful. If for any TMGI of the new UE there are MB session Ctxts in active state in the T-NG-RAN, the T-NG-RAN provides PTM / PTP transmission to the new UE.

[0168] 5. T-RAN to T-AMF: Handover notification.

[0169] With this message, the handover is considered successful in the T-RAN.

[0170] For each QoS flow accepted using an alternative QoS profile (see TS 23.501 [2]), the target RAN shall send to the SMF a reference to the completed alternative QoS profile.

[0171] 6a. [Conditional] T-AMF to S-AMF: Namf_Communication_N2InfoNotify.

[0172] The T-AMF informs the S-AMF about the N2 handover notification received from the T-RAN by invoking Namf_Communication_N2InfoNotify.

[0173] A timer in the S-AMF is started to supervise when the resources in the S-RAN should be released.

[0174] 6b. [Conditional] S-AMF to T-AMF: Namf_Communication_N2InfoNotify Ack (N2 SM information (assistance RAT usage data)).

[0175] The S-AMF acknowledges by sending Namf_Communication_N2InfoNotify Ack to the T-AMF. The N2 SM information here is the information buffered at step 2a0 when applicable.

[0176] 6c. [Conditional] S-AMF to SMF: Nsmf_PDUSession_ReleaseSMContext request (SUPI, PDU Session ID, N2 SM information (assistance RAT usage data)).

[0177] If the T-AMF does not accept the PDU session (e.g. the S-NSSAI associated with the PDU session is not available in the T-AMF), the S-AMF triggers the PDU session release procedure as specified in section 4.3.4.2 in step 6a after the S-AMF receives the N2 handover notification.

[0178] 7. T-AMF to SMF: Nsmf_PDUSession_UpdateSMContext request (handover completion indication for PDU Session ID, UE presence in LADN service area, N2 SM information (assistance RAT usage data)). The N2 SM information here is the information received at step 6b when applicable.

[0179] The handover completion indication is sent to the corresponding SMF per PDU session to indicate the success of the N2 handover.

[0180] When the smf_PDUSession_UpdateSMContext response message arrives too late during the handover preparation phase (see step 8 of section 4.9.1.3.2), or in case the T-RAN does not accept the PDU session with SMF involvement, the NsmfPDUSession_UpdateSMContext request (SUPI, PDU Session ID, Operation Type) is sent to the corresponding SMF, allowing the SMF to de-allocate the N3 UP address and tunnel ID of the selected UPF that can have been allocated. The PDU session handled by this SMF is considered deactivated and the handover attempt for this PDU session is terminated.

[0181] In case the AMF determines that the PDU session is related to a LADN, the AMF provides "UE is present in the LADN service area". If the AMF does not provide the "UE is present in the LADN service area" indication and the SMF determines that the DNN corresponds to a LADN, the SMF considers the UE outside the LADN service area.

[0182] The SMF takes actions on LADN PDU sessions as defined in TS 23.501 [2] section 5.6.5 based on the "UE is present in the LADN service area" indication.

[0183] For each QoS flow for which the SMF has received a reference to a completed alternative QoS profile, the SMF informs the PCF and the UE as described in TS 23.501 [2].

[0184] 8a. [Conditional] SMF to T-UPF (intermediate): N4 Session Modification Request.

[0185] If a new T-UPF is inserted or an existing intermediate S-UPF is reassigned, the SMF shall send an N4 Session Modification Request to the T-UPF indicating the DL AN tunnel information of the T-RAN.

[0186] 8b. [Conditional] T-UPF to SMF: N4 Session Modification Response.

[0187] The T-UPF confirms by sending an N4 Session Modification Response message to the SMF.

[0188] 9a. [Conditional] SMF to S-UPF (intermediate): N4 Session Modification Request.

[0189] If the UPF is not reassigned, the SMF shall send to the S-UPF an N4 Session Modification Request indicating the DL AN tunnel information of the T-RAN.

[0190] 9b. [Conditional] S-UPF to SMF: N4 Session Modification Response. In some embodiments, the S-UPF confirms by sending an N4 Session Modification Response message to the SMF.

[0191] 10a. [Conditional] SMF to UPF (PSA): N4 Session Modification Request.

[0192] For non-roaming or local breakout roaming scenarios, the SMF sends to the PDU Session Anchor UPF (UPF (PSA)) an N4 Session Modification Request message providing the N3 AN tunnel information of the T-RAN or the DL CN tunnel information of the T-UPF in case of insertion of a new T-UPF or reassignment of an existing intermediate S-UPF. If redundant transmission is performed for one or more QoS flows of the PDU Session, two pieces of N3 AN tunnel information of the T-RAN or two pieces of DL CN tunnel information of the two T-UPFs are provided and the SMF indicates to the UPF (PSA) which one of the AN / CN tunnel information to use as the redundant tunnel for the PDU Session. If an existing intermediate S-UPF terminating towards N9 of the H-UPF (PDU Session Anchor) is reassigned for a home routed roaming scenario, the V-SMF invokes the Nsmf_PDUSession_Update Request (End Marker indication) service operation to the H-SMF. The End Marker indication is used to indicate that an End Marker is to be sent.

[0193] In case the S-UPF acts as UL CL or BP, the SMF indicates only one of the PDU Session Anchors to send the “End Marker” packet. To ensure that the “End Marker” is the last user plane packet on the old path, the SMF shall modify the path on the other PDU Session Anchor before indicating the PDU Session Anchor to send the “End Marker” packet.

[0194] If no T-UPF is inserted or no existing intermediate S-UPF is reassigned, steps 10a and 10b are skipped.

[0195] 10b. [Conditional] UPF (PSA) to SMF: N4 Session Modification Response.

[0196] The UPF(PSA) sends an N4 Session Modification Response message to the SMF. To assist the reordering function in the T-RAN, the UPF(PSA) sends one or more “end marker” packets immediately after the handover path for each N3 tunnel on the old path, which the source NG-RAN shall forward to the target NG-RAN. In this regard, if a new T-UPF is inserted or an existing intermediate S-UPF is reallocated, the UPF(PSA) starts sending downlink packets via the T-UPF to the T-RAN. In case of home routed roaming scenario, once the H-UPF (PDU Session Anchor) is updated with the UL tunnel information of the T-UPF, the H-SMF responds to the V-SMF using the Nsmf_PDUSession_UpdateResponse service operation.

[0197] Steps 10a and 10b are performed for each UPF(PSA) when there are multiple UPF(PSA).

[0198] 11. SMF to T-AMF: Nsmf_PDUSession_UpdateSMContext Response (PDU Session ID).

[0199] The SMF acknowledges the reception of the Handover Complete.

[0200] If indirect data forwarding is applied, the SMF starts the indirect data forwarding timer to release the resources of the indirect data forwarding tunnel.

[0201] 12. The UE initiates the mobility registration update procedure as described in section 4.2.2.2.2.

[0202] The target AMF knows that this is a handover procedure, so the target AMF only performs a subset of the registration procedure, specifically, steps 4, 5 and 10 for context transfer between the source AMF and the target AMF in the registration procedure are skipped.

[0203] 13a. [Conditional] SMF to S-UPF (intermediate): N4 Session Release Request.

[0204] If there is a source intermediate UPF, the SMF initiates the resource release after the expiry of the timer or the indirect data forwarding timer in step 6 by sending an N4 Session Release Request (Release Cause) to the source UPF. This message is also used to release the indirect data forwarding resources in the S-UPF.

[0205] 13b. S-UPF to SMF: N4 Session Release Response.

[0206] The S-UPF acknowledges using the N4 Session Release Response message to acknowledge the release of resources.

[0207] In case of indirect data forwarding, the resources for indirect data forwarding are also released.

[0208] 14a. AMF to S-RAN: UE Context Release Command ().

[0209] After the expiry of the timer in step 6a, the AMF sends the UE Context Release Command.

[0210] 14b. S-RAN to AMF: UE Context Release Complete ().

[0211] The source NG-RAN releases its resources related to the UE and responds with the UE Context Release Complete () message.

[0212] 14c. [Conditional] If the UE is the last UE leaving the MB session in the S-NG-RAN, the S-NG-RAN releases its resources for the MB session (see session leaving procedure).

[0213] 15a. [Conditional] SMF to T-UPF: N4 Session Modification Request.

[0214] If indirect forwarding is applied and the UPF is reassigned, after the expiry of the timer for indirect data forwarding, the SMF sends the N4 Session Modification Request to the T-UPF to release the indirect data forwarding resources.

[0215] 15b. [Conditional] T-UPF to SMF: N4 Session Modification Response.

[0216] The T-UPF acknowledges with the N4 Session Modification Response message to confirm the release of the indirect data forwarding resources.

[0217] If other NFs have subscribed to mobility events with this AMF, the AMF notifies the corresponding NFs of the event by invoking the Namf_EventExposure_Notify service operation described in clause 4.15.4.2.

[0218] Upon receiving Namf_EventExposure_Notify with an indication that only regulatory priority services have access to the UE, the SMF deactivates the PDU session if the service of the PDU session is not regulatory priority. For the case of home routed roaming, the V-SMF triggers deactivation of the PDU session, in addition, the H-SMF upon receiving the notification, refrains from sending downlink signaling if it is not related to regulatory priority traffic.

[0219] In some embodiments, the impact on services, entities, and interfaces can include one or more of the following:

[0220] UE: - receives multicast data using PTM / PTP under RRC connection. - receives handover from source NG-RAN to target NG-RAN when the N2 handover execution phase starts.

[0221] NG-RAN: - MB session resource setup during N2 handover preparation phase. - reception of MB media flow. - forwards MB media flow to UEs using PTM / PTP transmission when the N2 handover execution phase starts.

[0222] AMF: - triggers MB session join and MB session start signaling to setup resources during N2 handover preparation phase.

[0223] In this way, some embodiments provide support for multicast broadcast session continuity (aka "handover") at inter-gNB Xn handover and inter-gNB N2 handover in 5G NR radio access.

[0224] Figure 9 is a schematic block diagram of a radio access node 900 according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The radio access node 900 can be, for example, a base station 102 or 106 or a network node implementing all or part of the functionality of a base station 102 or gNB described herein. As shown, the radio access node 900 includes a control system 902 that includes one or more processors 904 (e.g., central processing units (CPUs), application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), and / or the like), memory 906, and a network interface 908. The one or more processors 904 are also referred to herein as processing circuitry. In addition, the radio access node 900 can include one or more radio units 910 that each include one or more transmitters 912 and one or more receivers 914 coupled with one or more antennas 916. The radio units 910 can be referred to as, or be part of, radio interface circuitry. In some embodiments, the radio units 910 are external from the control system 902 and connected to the control system 902 via, for example, a wired connection (e.g., an optical cable). However, in some other embodiments, the radio units 910 and possibly the antennas 916 are integrated with the control system 902. The one or more processors 904 are used to provide one or more functions of the radio access node 900 as described herein. In some embodiments, the functions are implemented in software that is stored, for example, in the memory 906 and executed by the one or more processors 904.

[0225] Figure 10is a schematic block diagram illustrating a virtualized embodiment of a radio access node 900 according to some embodiments of the present disclosure. The discussion applies equally to other types of network nodes. In addition, other types of network nodes can have similar virtualized architectures. Also, optional features are represented by dashed boxes.

[0226] As used herein, a "virtualized" radio access node is an implementation of the radio access node 900 in which at least a portion of the functionality of the radio access node 900 is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network). As illustrated, in this example, the radio access node 900 can include a control system 902 and / or one or more radio units 910, as described above. The control system 902 can be connected to the radio unit(s) 910 via, for example, an optical cable or the like. The radio access node 900 includes one or more processing nodes 1000 coupled to or included as part of a network 1002. If present, the control system 902 or radio unit is connected to the processing node(s) 1000 via the network 1002. Each processing node 1000 includes one or more processors 1004 (e.g., CPUs, ASICs, FPGAs, or the like), memory 1006, and a network interface 1008.

[0227] In this example, the functionality 1010 of the radio access node 900 described herein is implemented at the processing node(s) 1000 or distributed across the processing node(s) 1000 and the control system 902 and / or radio unit(s) 910 in any desired manner. In some particular embodiments, some or all of the functionality 1010 of the radio access node 900 described herein is implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 1000. As will be appreciated, additional signaling or communication between the processing node(s) 1000 and control system 902 is used in order to perform at least some of the desired functionality 1010. Notably, in some embodiments, the control system 902 can not be included, in which case the radio unit(s) 910 communicate directly with the processing node(s) 1000 via an appropriate network interface.

[0228] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of radio access node 900 or a node (e.g., processing node 1000) implementing one or more functions of radio access node 900 in a virtual environment according to any of the embodiments described herein 1010. In some embodiments, a carrier containing the computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0229] Figure 11 is a schematic block diagram of a radio access node 900 according to some other embodiments of the present disclosure. The radio access node 900 includes one or more modules 1100, each of which is implemented in software. The one or more modules 1100 provide the functionality of the radio access node 900 described herein. This discussion is equally applicable to the processing node 1000 of Figure 10 where the modules 1100 can be implemented at one of the processing nodes 1000 or distributed across multiple processing nodes 1000 and / or distributed across the processing nodes 1000 and the control system 902.

[0230] Figure 12 is a schematic block diagram of a wireless communication device 1200 according to some embodiments of the present disclosure. As illustrated, the wireless communication device 1200 includes one or more processors 1202 (e.g., CPUs, ASICs, FPGAs, etc.), memory 1204, and one or more transceivers 1206 each including one or more transmitters 1208 and one or more receivers 1210 coupled to one or more antennas 1212. The transceiver 1206 includes radio-front end circuitry coupled to the antenna 1212 that is configured to condition signals communicated between the antenna 1212 and the processor 1202, as will be appreciated by persons skilled in the art. The processor 1202 is also referred to herein as processing circuitry. The transceiver 1206 is also referred to herein as radio circuitry. In some embodiments, the functionality of the wireless communication device 1200 described above can be fully or partially implemented in software that is, for example, stored in the memory 1204 and executed by the processor 1202. Note that the wireless communication device 1200 can include additional components not Figure 12 not shown in FIG. 12, such as one or more user interface components (e.g., input / output interfaces including displays, buttons, touchscreens, microphones, speakers, etc., and / or any other components allowing input of information into and / or output of information from the wireless communication device 1200), power supplies (e.g., batteries and associated power supply circuitry), etc.

[0231] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of a wireless communication device 1200 according to any of the embodiments described herein is provided. In some embodiments, a carrier containing the computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory or a storage device).

[0232] Figure 13 is a schematic block diagram of a wireless communication device 1200 according to some other embodiments of the disclosure. The wireless communication device 1200 includes one or more modules 1300, each of which is implemented in software. The modules 1300 provide the functionality of the wireless communication device 1200 described herein.

[0233] Reference Figure 14 , according to an embodiment, F1404. The access network 1402 comprises a plurality of base stations 1406A, 1406B, 1406C, e.g., Node Bs, eNBs, gNBs, or other types of wireless Access Points (APs), each defining a corresponding coverage area 1408A, 1408B, 1408C. Each base station 1406A, 1406B, 1406C is connectable to the core network 1404 over a wired or wireless connection 1410. A first UE 1412 located in coverage area 1408C is configured to wirelessly connect to, or be paged by, the corresponding base station 1406C. A second UE 1414 in coverage area 1408A is wirelessly connectable to the corresponding base station 1406A. While a plurality of UEs 1412, 1414 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 1406.

[0234] The telecommunication network 1400 is itself connected to a host computer 1416, which can be implemented as a hardware and / or software of a standalone server, a cloud-implemented server, a distributed server, or as a processing resource in a server farm. The host computer 1416 can be administered or operated by a service provider. The connection 1418 between the telecommunication network 1400 and the host computer 1416 can pass via an external network 1422, such as the Internet, a private network, or a combination of both. The external network 1422 in turn can be connected to the core network 1404, possibly by passing through an intermediate network (not shown). The intermediate network can be one or more of the public Internet, a private network, or a combination of both.

[0235] Figure 14 The communication system as a whole enables connectivity between the connected UEs 1412, 1414 and the host computer 1416. The connectivity can be described as an over-the-top (OTT) connection 1424. The host computer 1416 and the connected UEs 1412, 1414 are configured to use the OTT connection 1424 to exchange data and / or signaling, using the access network 1402, the core network 1404, any intermediate network 1422, and possible further infrastructure (not shown) as intermediaries. The OTT connection 1424 can be transparent in the sense that the participating communication devices through which the OTT connection 1424 passes are unaware of the content (e.g., nature or format) of the communications passing between the host computer 1416 and the connected UEs 1412, 1414. For example, the base station 1406 can not be aware that the data rate of the OTT connection 1424 is depending on the capacity of the wireless access interface 1408, the properties of the wireless access interface 1408, the data size of the data packets 1420, and / or the channel conditions.

[0236] Example implementations, in accordance with an embodiment, of the UE, base station, and host computer discussed in the preceding paragraphs will now be described with reference to the Figure 15 communications devices of the communication system 1500. The host computer 1502 further comprises processing circuitry 1508, which can have storage and / or processing capabilities. In particular, the processing circuitry 1508 can comprise one or more programmable processors, ASICs, FPGAs, or combinations of these (not shown) adapted to execute instructions. The host computer 1502 further comprises software 1510, which is stored in the host computer 1502 or accessible by the host computer 1502, and can be executable by the processing circuitry 1508. The software 1510 includes a host application 1512. The host application 1512 can be operable to provide a service to a remote user, such as the UE 1514, via an OTT connection 1516 terminating at the UE 1514 and the host computer 1502. In providing the service to the remote user, the host application 1512 can provide user data which is transmitted using the OTT connection 1516.

[0237] The communication system 1500 also includes a base station 1518 configured in the telecommunications system. The base station 1518 includes hardware 1520 enabling it to communicate with the host computer 1502 and the UE 1514. Hardware 1520 may include: a communication interface 1522 for establishing and maintaining wired or wireless connections with different communication devices of the communication system 1500; and a radio interface 1524 for establishing and maintaining at least a wireless connection 1526 with the UE 1514, which is located within the coverage area served by the base station 1518. Figure 15 (Not shown in the image). The communication interface 1522 can be configured to facilitate connection 1528 to the host computer 1502. The connection 1528 can be direct, or it can be through the core network of a telecommunications system (…). Figure 15 (Not shown) and / or via one or more intermediate networks located outside the telecommunications system. In the illustrated embodiment, the hardware 1520 of base station 1518 also includes processing circuitry 1530, which may include one or more programmable processors, ASICs, FPGAs, or combinations thereof (not shown) adapted to execute instructions. Base station 1518 also has software 1532 stored internally or accessible via an external connection.

[0238] The communication system 1500 also includes the previously mentioned UE 1514. The hardware 1534 of UE 1514 may include a radio interface 1536 configured to establish and maintain a wireless connection 1526 with a base station serving the coverage area currently occupied by UE 1514. The hardware 1534 of UE 1514 also includes processing circuitry 1538, which may include one or more programmable processors, ASICs, FPGAs, or combinations thereof (not shown) suitable for executing instructions. UE 1514 also includes software 1540, which is stored in or accessible by UE 1514 and can be executed by the processing circuitry 1538. Software 1540 includes a client application 1542. Client application 1542 can be operated to provide services to human or non-human users via UE 1514, supported by host computer 1502. In host computer 1502, the executing host application 1512 can communicate with the executing client application 1542 via OTT connection 1516, which terminates between UE 1514 and host computer 1502. When providing services to a user, client application 1542 can receive request data from host application 1512 and provide user data in response to the request data. OTT connection 1516 can transmit both request data and user data. Client application 1542 can interact with the user to generate the user data it provides.

[0239] Notice, Figure 15The host computer 1502, base station 1518, and UE 1514 in Figure 14 Fig. 15 can be similar or identical to the host computer 1416, one of the base stations 1406A, 1406B, 1406C, and one of the UEs 1412, 1414 of Figure 15 Fig. 14, respectively. That is, the inner workings of these entities can be as shown in Figure 14 Fig. 15 and independently, the surrounding network topology can be that of Fig. 14.

[0240] In Figure 15 Fig. 15, OTT connection 1516 is abstractly depicted as an OTT connection 1516 between host computer 1502 and UE 1514, without explicit reference to any intermediate devices and the precise routing of message via these devices. Network infrastructure can make routing decisions to Fig. 15, OTT connection 1516 is abstractly depicted as an OTT connection 1516 between host computer 1502 and UE 1514, without explicit reference to any intermediate devices and the precise routing of message via these devices. Network infrastructure can make routing decisions to

[0241] Fig. 15, OTT connection 1516 is abstractly depicted as an OTT connection 1516 between host computer 1502 and UE 1514, without explicit reference to any intermediate devices and the precise routing of message via these devices. Network infrastructure can make routing decisions to Fig. 15, OTT connection 1516 is abstractly depicted as an OTT connection 1516 between host computer 1502 and UE 1514, without explicit reference to any intermediate devices and the precise routing of message via these devices. Network infrastructure can make routing decisions to

[0242] A measurement procedure can be implemented to monitor data rate, latency and other factors of one or more embodiments improvements. There can also be an optional network functionality to reconfigure OTT connection 1516 between host computer 1502 and UE 1514, in response to variations in the measurement results. The measurement procedure and / or the network functionality to reconfigure OTT connection 1516 can be implemented in software 1510 and hardware 1504 of host computer 1502, or in software 1540 and hardware 1534 of UE 1514, or both. In some embodiments, sensors (not shown) can be deployed in or in association with communication devices through which OTT connection 1516 passes; the sensors can participate the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 1510, 1540 can compute or estimate the monitored quantities. The reconfiguring of OTT connection 1516 can include message format, retransmission settings, preferred routing, etc.; the reconfiguring need not affect base station 1518, and it can be unknown or invisible to the base station 1518. Such procedures and functionalities can be known and practiced in the art. In certain embodiments, measurements can involve proprietary UE signaling facilitating host computer 1502’s measurements of throughput, propagation times, latency and the like. The measurements can be implemented in that software 1510, 1540 causes messages to be transmitted, in particular empty or ‘dummy’ messages, using OTT connection 1516, while it monitors propagation times, errors etc.

[0243] Figure 16 is a flowchart illustrating a method implemented in a communication system in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which can be those described with reference to Figure 14 and Figure 15 . For simplicity of the present disclosure, only drawing references to Figure 16 will be included in this section. In step 1600, the host computer provides user data. In sub-step 1602 (which can be optional) of step 1600, the host computer provides the user data by executing a host application. In a second step 1604, the host computer initiates a transmission carrying the user data to the UE. In a third step 1606 (which can be optional), the base station transmits to the UE the user data carried in the transmission initiated by the host computer, in accordance with the teachings of the embodiments described throughout this disclosure. In step 1608 (which can also be optional), the UE executes a client application associated with the host application executed by the host computer.

[0244] Figure 17is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which can be those described with reference to Figure 14 and Figure 15 Figures 13 to 16. To simplify the present disclosure, in this section, reference will only be made to the Figure 17 embodiments described with reference to Figures 13 to 16. In step 1700 of the method, the host computer provides user data. In an optional substep (not shown) the host computer provides the user data by executing a host application. In a second step 1702, the host computer initiates a transmission carrying the user data to the UE. The transmission can pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In step 1704 (which can be optional), the UE receives the user data carried in the transmission.

[0245] Figure 18 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which can be those described with reference to Figure 14 and Figure 15 Figures 13 to 16. To simplify the present disclosure, in this section, reference will only be made to the Figure 18 embodiments described with reference to Figures 13 to 16. In step 1800 (which can be optional), the UE receives input data provided by the host computer. Additionally or alternatively, in a second step 1802, the UE provides user data. In a substep 1804 (which can be optional) of step 1800, the UE provides the user data by executing a client application. In a substep 1806 (which can be optional) of step 1802, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executing client application can further take into account user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in a third substep 1808 (which can be optional), transmission of the user data to the host computer. In a step 1810 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

[0246] Figure 19 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which can be those described with reference to Figure 14 and Figure 15 Figures 13 to 16. To simplify the present disclosure, in this section, reference will only be made to the Figure 19The base station initiates transmission of the received user data to the host computer. In a third step 1904, the host computer receives the user data carried in the transmission initiated by the base station.

[0247] Any appropriate steps, methods, features, functions, or benefits disclosed herein can be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus can comprise a number of these functional units. These functional units can be implemented by processing circuitry, which can include one or more microprocessor or microcontrollers, as well as other digital hardware (which can include digital signal processors (DSPs), special-purpose computer chips, application- specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), and / or regular microprocessors, etc.). The processing circuitry can be configured to execute program code stored in memory to perform the functions described herein. The memory can include one or several types of memory such as read-only memory (ROM), random-access memory (RAM), cache memory, flash memory devices, optical storage media, etc. The program code can include program instructions for implementing the methods disclosed herein, as well as other

[0248] While the processes in the accompanying figures illustrate particular orders of performing certain operations, it should be understood that such order is exemplary (e.g., alternative embodiments can perform the operations in different order, combine certain operations, overlap certain operations, etc.).

[0249] Embodiments

[0250] Group A Embodiments

[0251] Embodiment 1 : A method for session continuity for MB sessions performed by a wireless device, the method comprising at least one of: receiving at least one MB session while connected with a 5G; handover to a target NG-RAN; and continuing to receive the at least one MB session.

[0252] Embodiment 2: The method of embodiment 1, wherein handover to a target NG-RAN comprises an Xn handover.

[0253] Embodiment 3: The method of embodiment 1, wherein handover to a target NG-RAN comprises an N2 handover.

[0254] Embodiment 4: The method of any one of embodiments 1 to 3, wherein the handover comprises any of the features described in Group B Embodiments.

[0255] Embodiment 5: The method of any of the preceding embodiments, further comprising: providing user data; and forwarding the user data to the host computer via a transmission to the base station.

[0256] Group B Embodiments

[0257] Embodiment 6: A method for session continuity for MB sessions performed by a base station, the method comprising at least one of: providing at least one MB session to a wireless device connected with a 5G connection; determining that the wireless device is being handed over to a target NG-RAN; and providing session continuity for the at least one MB session to the wireless device.

[0258] Embodiment 7: A method for session continuity for MB sessions performed by a base station, the method comprising at least one of: receiving a handed over wireless device that is receiving at least one MB session; and providing session continuity for the at least one MB session to the wireless device.

[0259] Embodiment 8: The method of any of embodiments 6-7, wherein the handover to the target NG-RAN comprises an Xn handover.

[0260] Embodiment 9: The method of embodiment 8, further comprising causing resources to be established in the target NG-RAN during an Xn handover preparation phase.

[0261] Embodiment 10: The method of any of embodiments 8-9, further comprising causing resources to be established in the target NG-RAN during an Xn handover execution phase.

[0262] Embodiment 11: The method of any of embodiments 8-10, further comprising notifying and / or triggering the AMF to start establishing MB session resources in the NG-RAN.

[0263] Embodiment 12: The method of embodiment 11, wherein the notifying and / or triggering comprises an MB session command.

[0264] Embodiment 13: The method of embodiment 11, wherein the notifying and / or triggering comprises a new parameter to an existing path switch request and / or path switch request acknowledge message.

[0265] Embodiment 14: The method of any of embodiments 8-13, wherein a new parameter “TMGIs” (or list of TMGIs) is included in the existing path switch request message.

[0266] Embodiment 15: The method of any of embodiments 6-7, wherein the handover to the target NG-RAN comprises an N2 handover.

[0267] Embodiment 16: The method of embodiment 15 further comprises causing resources to be established in the target NG-RAN at an N2 handover preparation phase.

[0268] Embodiment 17: The method of any of embodiments 1 to 16 further comprises releasing resources if this is the last wireless device leaving the MB session.

[0269] Embodiment 18: The method of any of the preceding embodiments, further comprising obtaining user data; and forwarding the user data to the host computer or the wireless device.

[0270] Group C Embodiments

[0271] Embodiment 19: A wireless device for session continuity for a MB session, the wireless device comprising processing circuitry configured to perform any of the steps of any of the embodiments in Group A; and power supply circuitry configured to supply power to the wireless device.

[0272] Embodiment 20: A base station for session continuity for a MB session, the base station comprising processing circuitry configured to perform any of the steps of any of the embodiments in Group B; and power supply circuitry configured to supply power to the base station.

[0273] Embodiment 21 : A user equipment, UE, for session continuity for a MB session, the UE comprising an antenna configured to transmit and receive wireless signals; radio front-end circuitry connected to the antenna and to processing circuitry and configured to condition signals communicated between the antenna and the processing circuitry; the processing circuitry configured to perform any of the steps of any of the embodiments in Group A; an input interface connected to the processing circuitry and configured to allow input of information into the UE to be processed by the processing circuitry; an output interface connected to the processing circuitry and configured to output information from the UE that has been processed by the processing circuitry; and a battery connected to the processing circuitry and configured to supply power to the UE.

[0274] Embodiment 22: A communication system including a host computer comprising processing circuitry configured to provide user data; and a communication interface configured to forward the user data to a cellular network for transmission to a user equipment, UE; wherein the cellular network comprises a base station having a radio interface and a processing circuitry, the base station’s processing circuitry configured to perform any of the steps of any of the embodiments in Group B.

[0275] Embodiment 23: The communication system of the preceding embodiment, further including the base station.

[0276] Embodiment 24: The communication system of the preceding 2 embodiments, further including the UE, wherein the UE is configured to communicate with the base station.

[0277] Embodiment 25: A communication system according to the previous 3 Embodiments, wherein: the processing circuitry of the host computer is configured to execute a host application, thereby providing the user data; and the UE comprises processing circuitry configured to execute a client application associated with the host application.

[0278] Embodiment 26: A method implemented in a communication system including a host computer, a base station and a user equipment, UE, the method comprising: at the host computer, providing user data; and at the host computer, initiating a transmission carrying the user data to the UE via a cellular network comprising the base station, wherein the base station performs any of the steps of any of the Group B embodiments.

[0279] Embodiment 27: The method according to the previous Embodiment, further comprising: at the base station, transmitting the user data.

[0280] Embodiment 28: The method according to the previous 2 Embodiments, wherein the user data is provided at the host computer by execution of a host application, the method further comprising executing, at the UE, a client application associated with the host application.

[0281] Embodiment 29: A user equipment, UE, configured to communicate with a base station, the UE comprising a radio interface and processing circuitry, the processing circuitry configured to perform a method according to the previous 3 Embodiments.

[0282] Embodiment 30: A communication system including a host computer comprising processing circuitry configured to provide user data; and a communication interface configured to forward the user data to a cellular network for transmission to a user equipment, UE; wherein the UE comprises a radio interface and processing circuitry, the UE’s components configured to perform any of the steps of any of the Group A embodiments.

[0283] Embodiment 31: The communication system according to the previous Embodiment, wherein the cellular network further comprises the base station, the base station configured to communicate with the UE.

[0284] Embodiment 32: The communication system according to the previous 2 Embodiments, wherein: the processing circuitry of the host computer is configured to execute a host application, thereby providing the user data; and the processing circuitry of the UE is configured to execute a client application associated with the host application.

[0285] Example 33: A method implemented in a communication system including a host computer, a base station, and a User Equipment, UE, the method comprising: at the host computer, providing user data; and at the host computer, initiating a transmission carrying the user data to the UE via a cellular network comprising the base station, wherein the UE is configured to perform any of the steps of any of the Group A embodiments.

[0286] Example 34: The method of the preceding embodiment, further comprising: at the UE, receiving, from the base station, the user data.

[0287] Example 35: A communication system including a host computer, the host computer comprising a communication interface configured to receive user data originating from a transmission from a user equipment, UE, to a base station; wherein the UE comprises a radio interface and processing circuitry, the UE’s processing circuitry configured to perform any of the steps of any of the Group A embodiments.

[0288] Example 36: The communication system of the preceding embodiment, further comprising the UE.

[0289] Example 37: The communication system of the preceding 2 embodiments, further comprising the base station, wherein the base station comprises a radio interface configured to communicate with the UE and a communication interface configured to forward the user data carried from the UE to the base station to the host computer.

[0290] Example 38: The communication system of the preceding 3 embodiments, wherein: the host computer’s processing circuitry is configured to execute a host application; and the UE’s processing circuitry is configured to execute a client application associated with the host application, thereby providing the user data.

[0291] Example 39: The communication system of the preceding 4 embodiments, wherein: the host computer’s processing circuitry is configured to execute a host application, thereby providing request data; and the UE’s processing circuitry is configured to execute a client application associated with the host application, thereby providing the user data in response to the request data.

[0292] Example 40: A method implemented in a communication system including a host computer, a base station, and a User Equipment, UE, the method comprising: at the host computer, receiving user data transmitted from the UE to the base station, wherein the UE performs any of the steps of any of the Group A embodiments.

[0293] Example 41: The method of the preceding embodiment, further comprising: at the UE, providing the user data to the base station.

[0294] Embodiment 42: The method of the preceding 2 embodiments, further comprising: at the UE, executing a client application, thereby providing the user data to be transmitted; and at the host computer, executing a host application associated with the client application.

[0295] Embodiment 43: The method of the preceding 3 embodiments, further comprising: at the UE, executing a client application; and at the UE, receiving input data for the client application, the input data being provided at the host computer by executing a host application associated with the client application; wherein the user data to be transmitted is provided by the client application in response to the input data.

[0296] Embodiment 44: A communication system including a host computer comprising a communication interface configured to receive user data originating from a transmission from a user equipment, UE, to a base station, wherein the base station comprises a radio interface and processing circuitry configured to perform any of the steps of any of the Group B embodiments.

[0297] Embodiment 45: The communication system of the preceding embodiment, further including the base station.

[0298] Embodiment 46: The communication system of the preceding 2 embodiments, further including the UE, wherein the UE is configured to communicate with the base station.

[0299] Embodiment 47: The communication system of the preceding 3 embodiments, wherein: the processing circuitry of the host computer is configured to execute a host application; and the UE is configured to execute a client application associated with the host application, thereby providing the user data to be received by the host computer.

[0300] Embodiment 48: A method implemented in a communication system including a host computer, a base station and a user equipment, UE, the method comprising: at the host computer, receiving from the base station user data originating from a transmission received by the base station from the UE, wherein the UE performs any of the steps of any of the Group A embodiments.

[0301] Embodiment 49: The method of the preceding embodiment, further comprising at the base station, receiving the user data from the UE.

[0302] Embodiment 50: The method of the preceding 2 embodiments, further comprising at the base station, initiating transmission of the received user data to the host computer.

[0303] At least some of the following abbreviations can be used in this disclosure. If there is an inconsistency between abbreviations, the above should take precedence over any subsequent listing. If listed multiple times below, the first listing should take precedence over any subsequent listing.

[0304] • 3GPP Third Generation Partnership Project

[0305] • 5G Fifth Generation

[0306] • 5GC Fifth Generation Core

[0307] • 5GS Fifth Generation System

[0308] • AF Application Function

[0309] • AMF Access and Mobility Function

[0310] • AN Access Network

[0311] • AP Access Point

[0312] • ASIC Application-Specific Integrated Circuit

[0313] • AUSF Authentication Server Function

[0314] • CPU Central Processing Unit

[0315] • DN Data Network

[0316] • DSP Digital Signal Processor

[0317] • eMBMS Evolved Multicast / Broadcast Multimedia Subsystem

[0318] • eNB Enhanced or Evolved Node B

[0319] • EPS Evolved Packet System

[0320] • E-UTRA Evolved Universal Terrestrial Radio Access

[0321] • FPGA Field-Programmable Gate Array

[0322] • gNB New Radio Base Station

[0323] • gNB-CU gNB Centralized Unit

[0324] • gNB-DU New Radio Base Station Distributed Unit

[0325] • HSS Home Subscriber Server

[0326] • IoT Internet of Things

[0327] • IP Internet Protocol

[0328] • LTE Long Term Evolution

[0329] • MB Multiband Broadcast

[0330] • MBMS Multicast / Broadcast Multimedia Subsystem

[0331] • MME Mobility Management Entity

[0332] • MTC Machine Type Communication

[0333] • NEF Network Exposure Function

[0334] • NF Network Function

[0335] • NGAP Next Generation Application Protocol

[0336] • NG-RAN Next Generation Radio Access Network

[0337] • NR New Radio

[0338] • NRF Network Function Repository Function

[0339] • NSSF Network Slice Selection Function

[0340] • OTT Over-the-Top

[0341] • PC Personal Computer

[0342] • PCF Policy Control Function

[0343] • P-GW Packet Data Network Gateway

[0344] • QoS Quality of Service

[0345] • RAM Random Access Memory

[0346] • RAN Radio Access Network

[0347] • ROM Read Only Memory

[0348] • RRC Radio Resource Control

[0349] • RRH Remote Radio Head

[0350] • RTT Round Trip Time

[0351] • SCEF Service Capability Exposure Function

[0352] • SMF Session Management Function

[0353] • TMGI Temporary Mobile Group Identity

[0354] • UDM Unified Data Management

[0355] • UE User Equipment

[0356] • UPF User Plane Function

[0357] • V2X Vehicle to anything

[0358] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered to be within the scope of the concepts disclosed herein.

Claims

1. A method for session continuity for a multicast broadcast, MB, session performed by at least one wireless device participating / joining the MB session, the method comprising: receiving at least one MB session data associated with a temporary mobile group identity, TMGI, from a source next generation radio access network, NG-RAN; receiving an instruction to handover to a target cell in a target NG-RAN node in which a context for the MB session associated with the TMGI already exists; and continuing to receive data for the at least one MB session associated with the same TMGI via the target NG-RAN once the at least one wireless device is handed over to the target cell.

2. The method of claim 1, wherein, The handover to the target NG-RAN comprises an Xn handover.

3. The method of claim 1, wherein, The handover to the target NG-RAN comprises an N2 handover.

4. The method of claim 3, further comprising: Causing resources to be established in the target NG-RAN at an N2 handover preparation phase.

5. A method for session continuity for a multicast broadcast, MB, session performed by a next generation radio access network, NG-RAN, node, the method comprising: providing at least one MB session data associated with a temporary mobile group identity, TMGI, from an MB-user plane function, UPF, to one or more wireless devices; determining that at least one of the one or more wireless devices is handed over to a target NG-RAN node; handing over (504) the at least one of the one or more wireless devices and the at least one MB session associated with the TMGI to the target NG-RAN node; and releasing resources corresponding to the at least one MB session upon determining that the at least one of the one or more wireless devices is the last wireless device leaving the at least one MB session in the NG-RAN node as a result of the handover.

6. The method of claim 5, wherein, The handover to the target NG-RAN comprises an Xn handover.

7. The method of claim 6, further comprising: Causing resources to be established in the target NG-RAN at an Xn handover preparation phase.

8. The method of claim 6, further comprising: Causing resources to be established in the target NG-RAN at an Xn handover execution phase.

9. The method of claim 6, further comprising: Informing and / or triggering an access and mobility management function, AMF, to start establishing MB session resources in the target NG-RAN.

10. The method of claim 9, wherein, The informing and / or triggering comprises an MB session command.

11. The method of claim 9, wherein, The informing and / or triggering comprises a new parameter to an existing path switch request and / or path switch request acknowledge message.

12. The method of claim 11, wherein, The TMGI or a list of TMGIs is included in the existing path switch request message.

13. The method of claim 5, wherein, The handover to the target NG-RAN comprises an N2 handover.

14. The method of claim 13, further comprising: Causing resources to be established in the target NG-RAN at an N2 handover preparation phase.

15. The method of claim 5, further comprising: Releasing resources if this is the last wireless device leaving the MB session.

16. A method for session continuity for a multicast broadcast, MB, session performed by a next generation radio access network, NG-RAN, node, the method comprising: receiving a handed over wireless device that is receiving at least one MB session associated with a temporary mobile group identity, TMGI, from a source next generation radio access network, NG-RAN; and providing the wireless device with session continuity of the at least one MB session associated with the TMGI.

17. The method of claim 16, wherein, The handover comprises any of the features of claims 6-15.

18. A wireless device (1200) for session continuity of a multicast broadcast, MB, session, comprising: one or more transmitters (1208); one or more receivers (1210); and processing circuitry (1202) associated with the one or more transmitters (1208) and the one or more receivers (1210), the processing circuitry (1202) being configured to cause the wireless device (1200) to: receive, from a source Next Generation Radio Access Network, NG-RAN, at least one MB session data associated with a Temporary Mobile Group Identity, TMGI; receive an instruction to handover to a target cell in a target NG-RAN node in which a context of the MB session associated with the TMGI already exists; and continue receiving, via the target NG-RAN, data of at least one MB session associated with the same TMGI once the wireless device is handed over to the target cell.

19. The wireless device (1200) according to claim 18, wherein, The processing circuitry (1202) is further configured to cause the wireless device (1200) to perform the method of any of claims 2-4.

20. A Next Generation Radio Access Network, NG-RAN, node (900) for session continuity of a multicast broadcast, MB, session, comprising: one or more transmitters (912); one or more receivers (914); and processing circuitry (904) associated with the one or more transmitters (912) and the one or more receivers (914), the processing circuitry (904) being configured to cause the NG-RAN node (900) to perform steps of: providing, from a MB-User Plane Function, UPF, at least one MB session data associated with a Temporary Mobile Group Identity, TMGI, to one or more wireless devices; determining that at least one of the one or more wireless devices is handed over to a target NG-RAN node; and handing over (504) the at least one of the one or more wireless devices and at least one MB session associated with the TMGI to the target NG-RAN node; upon determining that the at least one of the one or more wireless devices is the last wireless device leaving the at least one MB session in the NG-RAN node as a result of the handover, releasing resources corresponding to the at least one MB session.

21. The NG-RAN node (900) of claim 20, wherein, The processing circuitry (904) is further configured to cause the NG-RAN node (900) to perform the method of any of claims 6-15.

Images