Assisted handover to volte in case of vowifi failure

In the case of VOW IFI failure, to VOLTE's auxiliary switching technology field

[0001] The present invention relates to managing wireless communication services, and in particular, to a method and device for controlling device switching between WLAN and cellular service access.

Background technique

[0002] Cellular data networks provide data connectivity for mobile devices with cellular network interfaces. The network consists of a network core for processing control plane functions and data packet routing, and a radio access network (RAN) of a macro cell base station located in the coverage area of the entire mobile network for wireless communication with user mobile devices. An example of cellular network architecture is Long Term Evolution (LTE). Unlike previous generations of second-generation (2G) and third-generation (3G) cellular networks that provide packet-switched data services on circuit-switched voice platforms, LTE is a fully packet-switched data network architecture that does not support traditional voice call platforms.

[0003] Since LTE does not support traditional voice telephony, some mobile network operators provide traditional voice telephony by switching mobile devices from the LTE network to 2G/3G services during a phone call or upon receiving a short message service (SMS). service. This process is called circuit switched fallback (CSFB).

[0004] CSFB provides a reliable way to handle voice calls, but requires network operators to maintain LTE and traditional networks. The former is used for data connectivity, and the latter is used for voice calls and slow data access in places where LTE network coverage is lacking.

[0005] Wireless local area networks (WLANs) operating in accordance with the IEEE 802.11 series of standards (commonly referred to as Wi-Fi) are common in many user locations and provide data connectivity within a short geographic range. Generally, a wireless local area network is generated and maintained by a wireless access point, which acts as a device connected to the WLAN (for example, a smart phone, a tablet) and a local network connected via a wired interface (TV, network attached storage) Packet routing interface between devices. The wireless access point serves local devices and is usually co-located or integrated with an external network interface (such as a modem) used to provide a backhaul link to an external network (such as the Internet) via an Internet service provider's core network. Example backhaul technologies include Digital Subscriber Line (xDSL) copper/fiber and cable based on the Cable Data Service Interface Specification (DOCSIS) architecture.

[0006] Throughout this, such a combined WLAN, routing, and modem device will be referred to as a hub. [0007] Both LTE and WLAN are examples of packet-switched data networks, where application data is divided into multiple packets, and the packets can take any path within the network to reach the recipient. In contrast, circuit-switched networks need to establish a dedicated data path before sending data along a dedicated circuit.

[0008] VoIP/VoLTE/VoffiFi

[0009] Internet telephony (VoIP) applications are known to allow voice communication via a packet-switched network. The voice data is sampled into voice data packets, and the packets are sent through the data network. Although the packets may arrive in a different order from the transmission order, the packet loss can be tolerated because the delay has a greater negative impact on the user's quality of experience.

[0010] The VOIP application is an Over-The Top (OTT) service, which usually requires users to generate a username identification, and usually can only establish VoIP between two users with the same VoIP application on their mobile devices call. Even in the case where the VoIP application allows calls to traditional phones and the caller information display shows the caller's phone number, when the callee tries to return the call, the call is forwarded to the standard dialer instead of the VoIP application.

[0011] In addition, in the VoIP service, if the mobile device moves out of the range of the current access point

If the technology is switched to another access technology, the call cannot be maintained.

[0012] Voice over LTE (Voice over LTE, VoLTE) is a voice service that runs through LTE. It uses optimized headers and priority markings to provide voice services using packet-switched networks. It aims to reduce/replace the need for CSFB and VoIP. rely. This will reduce operating overhead and may allow some traditional 2G and 3G platforms to shut down.

[0013] Since WLAN is ubiquitous in many areas, WiFi voice transmission (Voice over Wi_Fi, VoWiFi) or Wi-Fi call service has also been deployed by multiple network operators. In VoWiFi, WLAN is considered a non-3GPP access network base station to the LTE network, enabling standard telephony software to be used for making and receiving voice calls, and packet data tunneling in and out of the cellular network core. Therefore, VoWiFi appears to extend cellular network coverage to indoor locations and allows switching to normal VoLTE or CSFB services when mobile devices move to outdoor locations.

[0014] Therefore, mobile devices such as smart phones will have a cellular network interface and a WLAN interface for data connectivity. Traditionally, WLAN provides faster, more reliable and non-metered services, so when both WLAN and cellular access are available, mobile devices are configured to prefer WLAN interfaces for all data connections.

[0015] In conventional processing, the mobile device only cares about the quality of the WLAN signal to the hub. As long as the WLAN signal strength is higher than the signal strength threshold, the mobile device will remain connected to the WLAN even if there is no forward connection to an external network (such as the Internet). This may cause confusion for users because the mobile phone displays a strong WLAN connection (usually using icons with various bars to indicate signal strength), but the data service is not connected.

[0016] The present invention solves the above-mentioned problems.

Summary of the invention

[0017] In one aspect, an embodiment of the present invention provides a method of operating a wireless network access point to control at least one mobile device's access to a voice service located in a cellular network and accessible via the wireless access point , The wireless access point has a wireless network interface for communicating with at least one mobile device via a wireless link and a wide area network interface for communicating with a wide area network, and the at least one mobile device has a wireless network interface for communicating with the wireless network access point and A wireless network interface for voice services via a cellular gateway device located at the logical edge of a cellular network, and a cellular network interface for communicating with voice services via the cellular network, the method includes: processing related to the cellular gateway device There is information to determine whether the cellular gateway device is available; if the cellular gateway device is determined to be unavailable, it is determined whether at least one mobile device will lose access to voice services via the cellular gateway device; and if at least one mobile device will lose access to the voice service via the cellular gateway device The gateway device's access to the voice service indicates that at least one mobile device is connected to the voice service via the cellular network instead of the cellular gateway device.

[0018] In another aspect, an embodiment of the present invention provides an apparatus for controlling at least one mobile device to access a voice service located in a cellular network and accessible via a wireless access point, the at least A mobile device has a wireless network interface for communicating with wireless network access points and voice services via a cellular gateway device located at the logical edge of the cellular network, and also has a cellular network interface for communicating with voice services via the cellular network The device includes: a wireless network interface for communicating with the at least one mobile device via a wireless link; a wide area network interface for communicating with a wide area network; and a wide area network interface for processing presence information related to the cellular gateway device to determine the cellular gateway Means for whether the device is available; means for determining whether the at least one mobile device will lose access to the voice service via the cellular gateway device if the cellular gateway device is determined to be unavailable; and Means for instructing the at least one mobile device to connect to the voice service via the cellular network instead of the cellular gateway device if the at least one mobile device will lose access to the voice service via the cellular gateway device.

Description of the drawings

[0019] The embodiments of the present invention will now be described with the aid of the accompanying drawings, in which:

[0020] FIG. 1 schematically shows an overview of the communication network of the first embodiment;

[0021] FIG. 2 schematically shows the behavior of the hub and UE in the communication network when the link to the VoWiFi service component is interrupted;

[0022] FIG. 3 schematically shows the internal components of the hub according to the first embodiment;

[0023] FIG. 4 schematically shows an overview of connections formed by a VoWiFi service monitor to multiple hubs and multiple ePDGs of various MN0 networks;

[0024] FIG. 5 schematically shows the components of the VoWiFi service monitor in the first embodiment;

[0025] FIG. 6 is a flowchart showing the operation of the VoWiFi service monitor when checking the status of the link to the MN0; [0026] FIG. 7 is a flowchart showing how the hub causes the UE to disconnect or reconnect to VoWiFi from VoLTE Operation flow chart; and [0027] FIG. 8 schematically shows the internal components of the user entity device according to the first embodiment.

Detailed ways

[0028] System Overview

[0029] FIG. 1 shows an overview of main components in a communication system 1 according to the first embodiment. System 1 has multiple functional subsystems:

[0030] Long Term Evolution (LTE) cellular network 3 infrastructure;

[00311 Non-cellular network infrastructure including local network and Internet Service Provider (ISP) architecture 5; and

[0032] IP Multimedia Subsystem (IMS) 7.

[0033] In contrast to older circuit-switched networks, the LTE cellular network 3 provides data and voice services to cellular network client devices called user entities (UE), such as mobile phones 9, by using a packet-switched IP network. The LTE cellular network includes a network core 11 and a radio access network formed by the eNodeB 13 for connecting services and resources in the network core 11 to the UE 9. The network core U contains standard control functions such as a multimedia mobile entity (MME) (not shown), a home subscriber server (HSS) (not shown), and a policy configuration rule function (PCRF) (not shown). In order to route data packets to remote resources, there are multiple serving gateways (SGW) (not shown) and packet gateways (PGW) (not shown).

[0034] IMS 5 is an IP data network, which provides a unified service architecture for all networks. Even though the access networks may be different, multiple services can be provided on a single control/service layer. Therefore, IMS 7 reduces the need for duplication of data services/applications. VoLTE and VoWiFi voice call services are located in the application server 15 within the IMS 7. In this embodiment, they are provided by a service called Multimedia Telephony Service (MMTel).

[0035] The non-cellular network infrastructure 5 includes a wireless access point/modem router device 17 (hereinafter referred to as a hub) located in the home, which generates a wireless local area network (WLAN) 19 in accordance with the IEEE 802.11 series of standards to allow communication with the UE 9 and such as Only WLAN devices such as the computer W communicate. For external network access, the hub 17 communicates with an Internet Service Provider (ISP) 21, and the ISP 21 routes data to external servers and users via a wide area network such as the Internet 23.

[0036] Since the LTE cellular network 3 uses non-cellular access capabilities for applications such as Wi-Fi offloading, the LTE cellular network 3 also includes an evolved packet data gateway (ePDG) 25, which serves as a The termination point of the IPSec tunnel of the UE on the trusted 3GPP IP system. This allows data to enter the EPC network core 11 for use in LTE cellular 3 and IMS 7

Processing within the network.

[0037] The system in FIG. 1 also includes a VoWiFi service monitor 27, which is a network component maintained by an ISP or a third party. As shown in Figure 1, the VoWiFi service monitor has a data link 28 to the ePDG 25 and a data link to the hub 17. The SLVoWiFi service representative hub 17 monitors whether the ePDG 25 is accessible and therefore whether VoWiFi is available, and notifies the hub of the ePDG Any change in the accessibility of 25 over time.

[0038] The UE 9 has a WLAN wireless interface and an LTE wireless interface for respectively accessing a non-cellular network infrastructure and an LTE cellular network, and the UE 9 supports VoLTE, VoWiFi, and CSFB voice calls. In order to highlight the difference between the UE 9 and other connected WLAN devices 10, the computer 10 only has a WLAN interface and therefore can only access the WLAN 19 of the hub 17, but not the cellular network 3, because it does not have the ability to send and receive LTE. Signal interface.

[0039] UE behavior for activating Wi-Fi interface and LTE interface

[0040] As described above, the UE 9 has a WLAN interface and an LTE interface, and can perform both VoLTE call processing and VoWiFi call processing. Since the eNodeB 13 of the LTE network has a larger geographic coverage area than the WLAN 19, usually the UE will be connected to the LTE network 3 and will use VoLTE.

[0041] However, when the UE is within the range of the WLAN 19 (as shown in FIG. 1), there is overlap in the connectivity range, and the UE 9 can connect to the data service using a cellular interface or a WLAN interface. Generally, the default policy is to prefer WLAN connections. Therefore, when the UE is connected to the LTE network and it detects a known WLAN, the UE will try to use the WLAN.

[0042] Therefore, when a known WLAN is detected, the UE 9 will enable its WLAN interface and disable the cellular interface, causing any existing services to be disconnected. This change is usually transparent to the user of the UE because it has little impact on the operation of services such as file transfer and web browsing. However, a general UE strategy that prefers WLAN to cellular data interfaces may have an impact on the quality of experience of users who use VoWiFi instead of VoLTE voice services.

[0043] In particular, the VoWiFi service is only available when the UE 9 has a data link to the MMTel service 15 in the IMS 7 via the ePDG 25. If the ePDG 25 does not work, the UE cannot communicate to access the MMTel service and therefore will not be able to use VoWiFi to make and receive voice calls.

[0044] However, as long as the UE detects the WLAN 19, it will maintain the WLAN connection in preference to the LTE connection. Therefore, even if there is no connection to the VoWiFi service, the UE 9 will still be connected to the IjWLAN 19, which will cause the user of the UE to lose the voice call because the phone is not registered on the VoWiFi or VoLTE service.

[0045] In this embodiment, the hub 17 knows that some connected devices can use VoWiFi and therefore the hub 17 uses the information about the accessibility of the ePDG 25 from the VoWiFi service monitor 27, and therefore uses the availability of the VoWiFi service to Manage UE's access to VoWiFi.

[0046] As shown in FIG. 2, if the ePDG 25 loses service, for example, because the logical data link 28 is closed, the VoWiFi service monitor will notice the service loss and notify the hub 17 that the ePDG 25 is unavailable. With the new data, the hub can then notify the connected VoWiFi-enabled UE 9 that uses the VoWiFi service for this MN0 that in order to maintain voice connectivity, the UE 9 should switch to VoLTE even though WLAN 19 is available.

[0047] Since only the PDG 25 or the link 28 to the ePDG is determined to be inaccessible, the UE 9 can switch to VoLTE and LTE for all data services, or maintain two wireless connections, so that LTE is used for VoLTE, but All other data services use Wi-Fi.

[0048] The VoWiFi service monitor 27 continuously monitors the link to the ePDG, and when the ePDG 25 or the connection to the ePDG 25 is restored, the hub 17 is notified so that it can instruct the connected UE 9 to switch back to VoWiFi is available of. [0049] The components of the hub will now be described with reference to FIG. 3.

[0050] FIG. 3 shows the internal components of the hub 17 in more detail. The hub 17 contains a plurality of network interfaces for communicating with various types of network devices. For local devices, there is a wireless local area network (WLAN) interface 31 for communicating with wireless devices using a wireless protocol such as the IEEE 802.11 series of wireless LAN standards called Wi-Fi. In this embodiment, the WLAN interface 31 is compatible with the 802.1lac standard for WLAN operation. For wired LAN devices, there is an Ethernet interface 33 that conforms to the IEEE 802.3 standard.

[0051] In order to connect to an Internet Service Provider (ISP), the hub 17 has a wide area network (WAN) interface 35, which in this embodiment is a modem compatible with the Digital Subscriber Line (xDSL) series of standards, such as ultra-high-speed DSL ( VDSL) modem. In an ISP's alternative solution based on the Cable Data Service Interface Specification (DOCSIS), the WAN interface 35 is a cable modem compatible with the DOCSIS cable standard.

[0052] The hub 17 also includes a packet routing function 37, which is responsible for managing the flow of data packets between the three interfaces 31, 33, 35. The packet routing function 37 processes the headers of the input packets received on the three interfaces 31, 33, 35 and determines where to send the packet for forward delivery to the intended packet destination. The packet routing function 37 will also include functions such as network address translation (NAT) for directing packets between the local interfaces 31, 33 and the WAN interface 35.

[0053] In order to process the information from the VoWiFi service monitor 27 and apply the information to the connected UE 9, the hub 17 contains a VoWiFi monitor function 39. This function is connected to the WAN interface 35 and the packet routing function 37, and is responsible for communicating with the VoWiFi service monitor 27 to determine when the UE 9 will not be able to use VoWiFi and notifying the UE 9 to switch to VoLTE if necessary.

[0054] The VoWiFi monitor function 39 includes an interface 41 to the VoWiFi service monitor, a UE manager 43, and a VoWiFi connection client list 45.

[0055] The interface 41 to the VoWiFi service monitor is linked to the VoWiFi service monitor 27 via the data link 29 to receive status information about the ePDG 25 of the MN03. The connected device list 45 contains the identification of any UE 9 using the VoWiFi service. The connected device list 45 is a subset of the total set of devices connected to the WLAN. Although any WLAN-enabled device 9, 10 can be connected to the hub 17 as long as it has relevant credentials, not all devices have VoWiFi capability. For example, some smart phones have VoLTE and VoWiFi capabilities, but older smart phones, laptops, and computers will not be able to support VoWiFi, and therefore will not benefit from the processing of the first embodiment. In addition, some smart phones may have related hardware, but the service has not been enabled by their MN0. Therefore, it is important for the hub 17 to identify a group of VoWiFi-enabled UEs from the set of connected UEs on the WLAN to reduce its processing load.

[0056] In this embodiment, the hub 17 makes a passive determination of whether the device is operating the VoWiFi service by analyzing the address information of the data packet sent between the UE and the external resource.

[0057] The VoWiFi monitor 39 obtains a list of known ePDG addresses from the ePDG directory. ePDG is a gateway that links untrusted non-3GPP networks to network operators' EPC and IMS services. The address of the ePDG is well known, and therefore can be provided to the hub 17 by the ISP 21 via a management service such as TR-069 or a similar method for ISP 21 to hub 17 communication. Alternatively, the VoWiFi service monitor 27 provides a list of ePDGs it is monitoring during the registration process by the hub.

[0058] The VoWiFi monitor 39 identifies the VoWiFi-enabled UE 9 from the total set of connected WLAN devices by analyzing the IP flow passing through the hub 17. In particular, any IP flow whose destination is the ePDG gateway address can be assumed to be an IP flow for VoWiFi traffic between the VoWiFi-enabled UE 9 and the MMTel voice service 15. If there is any such flow, the VoWiFi monitor 39 extracts device information such as MAC address and saves the mapping between the IP address of the UE 9 and the ePDG of the user 0, so that the hub has a record of the subset of the WLAN device 9 , This subset has VoWiFi capability and

Is using or has used the VoWiFi service of the known ePDG 25.

[0059] The monitoring of the IP flow relies on the following standard processing of the UE 9 capable of VoWiFi service: establish an IPSec tunnel to the ePDG 25 when it is connected to the WLAN 19 to register to VoWiFi and/or switch from VoLTE to VoWiFi. Therefore, a device that does not establish a connection to the ePDG is considered a standard WLAN device.

[0060] The scanning process is periodically performed by the VoWiFi monitor 39 to maintain the validity of the connected client list 45 so that any new devices 9 connected to or disconnected from the WLAN 19 are identified. In this embodiment, the scan is performed every 5 minutes.

[00611 In addition, according to this embodiment, the connected client list further includes an entry field for storing the status of each ePDG. This data is provided by the VoWiFi service monitor, as will be described later.

[0062] The UE manager 43 is responsible for communicating with VoWiFi-enabled UEs 9 whose details are stored in the list of connected clients, and is especially used to inform those UEs 9 about when ePDG is unavailable and when ePDG is available after service interruption. Available again.

[0063] Further details regarding the operation of the hub 17 and the VoWiFi monitor function 39 will be described later when other network components are described.

[0064] In most countries, there is more than one MNO to improve competition and provide more user choices. Therefore, it is not sufficient to monitor a single MN0 as shown in FIG. 1, because UE 9 in the local area network may order different MN0.

[0065] FIG. 4 shows the general configuration of the VoWiFi service monitor 27 with respect to various hubs 17 and different ePDGs 25 of the MNO 3.

[0066] The VoWiFi service monitor 27 is configured with details of each MNO 3 in the service area, so that each ePDG 25 corresponding to the VoWiFi-enabled MNO 3 can be monitored for service availability. In Fig. 4, four MN0 3a, 3b, 3c, and 3d are shown, which provide VoWiFi service and each have their respective ePDG 25 to allow access from an external network.

[0067] The VoWiFi service monitor 27 is also connected to a plurality of hubs, and each hub provides services to different UEs 9 ordered to one of the four ketones 0 3a, 3b, 3c, and 3d. Using the information collected from ePDG monitoring, the VoWiFi service monitor can therefore periodically send information about the status of each ePDG to each hub 17.

[0068] By forming a central collector of ePDG status information, the number of ePDG status requests is minimized.

[0069] FIG. 5 shows the functional components of the VoWiFi service monitor 27.

[0070] The VoWiFi service monitor 27 is configured as a server and includes a network interface 51 for external device communication. The network interface 51 can be divided into two main interfaces, namely the ePDG interface 53 for communicating with the ePDG 25 and the hub interface 55 for communicating with the hub 17.

[0071] The ePDG link monitoring unit 57 controls communication via the ePDG interface 53, which receives input from the MN0 ePDG address information data storage 59 containing pre-stored IP address information for the location of each ePDG. In this embodiment, the status of the ePDG is determined by pinging the address of the ePDG. If each set in the ping is successfully sent and confirmed, then the logical data to the ePDG is considered an indication that the ePDG is working correctly. If the ping is lost, there must be a problem at the ePDG or Wi-Fi link, so the ePDG is considered inaccessible.

[0072] The MN0 ePDG current state table maintains information about the results of the ePDG state scan.

[0073] An example of the content of the MN0 ePDG current state table is shown below. In this example, all ePDGs for this set of MN0 are determined to be available.

<td>.MN0'</td><td>ePDG destination IP (via secure tunnel)</td><td>Logical link status</td>

<td>3 a</td><td>MNO 3 a ePDG server IP</td><td>Connect (UP)</td>

<td>3b</td><td>MNO 3b ef⁵DG server IP</td><td>connection</td>

<td>know</td><td>MNO 3c ePDG server IP</td><td>connection</td>

[0075] Table 1

[0076] In this embodiment, the network availability of the ePDG associated with MN0 3 is used as an indication of whether VoWiFi is available for UE 9. This is because ePDG is a publicly addressable entry point to the Keto-0 network. All VoWiFi traffic must travel through this network component between the MMTel service and any UE 9 that uses VoWiFi. Therefore, if the access to the ePDG is interrupted, the VoWiFi service will not be available for any UE 9.

[0077] The VoWiFi service monitor 27 is configured to monitor the logical network path between the device in the public network domain and the edge of the MN0 network represented by ePDG. Although the network paths will not be the same, if the VoWiFi network monitor 27 can establish a connection with the ePDG, other public addressable devices (such as hubs and UE 9) should also be able to form a logical data path to the ePDG.

[0078] On the side of the VoWiFi service monitor 27 facing the hub, the ePDG status information transmitter is responsible for registering the hub subscribed to the monitoring service, and uses the data in the MN0 ePDG current status table to notify the registered hub about the ePDG status.

[0079] FIG. 6 is a flowchart showing the operation of the components of the VoWiFi service monitor 27.

[0080] In step si, a list of ePDG addresses is obtained from the MN0 ePDG address information data storage 59. This list represents the publicly accessible IP address of each ePDG 25 in the country or operating area covered by the VoWiFi service monitor 27, which is 4 MN0 in this example. The address information is provided and installed by the system administrator. When the ePDG address changes or there is temporary offline maintenance, the address information can also be changed by the system administrator.

[0081] In step s3, the ePDG link monitoring unit 57 selects one of the ePDGs in the list 59, and pings the address within a period of time or within multiple messages. This is to confirm whether the ePDG is still publicly accessible.

[0082] In step s5, a test is performed to determine whether a response has been received from the ePDG.

[0083] If a response to the ping is received, the process proceeds to step s7, which updates the MN0 ePDG current state table 61 to indicate that the ePDG is available.

[0084] If the rest of step s5 fails, the ePDG link monitoring unit 59 waits for a period of time in step s9, in this case 500ms, and then checks again in step s11 to test. If a response is received, the process proceeds to step s7 described above.

[0085] If the response is still not received, it is assumed that the link to the ePDG link or the ePDG itself is disconnected, and in step s13, the MNO ePDG current state table 61 is updated to indicate lack of service.

[0086] After step s13 and step s7, a test is performed in step s15 to determine if there are any other ePDGs to try in the list. If there are more ePDGs, the process returns to step s3 so that more ePDGs can be tested.

[0087] For example, if the ePDG service monitor 27 can reach the ePDGs 25a and 25b but cannot reach the ePDG 25c of the MN0 3c, the MN0 ePDG current state table 61 will be updated to the following content:

[0088]

<td>ΜΝ0</td><td>ePDG destination IP (via secure tunnel)</td><td>Logical link status</td>

<td>3a</td><td>ΜΝ0 3a ePDG server IP</td><td>through</td>

<td>3b</td><td>ΜΝ0 3b ePDG server IP</td><td>through</td>

<td>3c</td><td>ΜΝ0 3c ePDG server IP</td><td>Cut off</td>

[0089] Table 2

[0090] After step s15, if there are no other ePDGs to try, a test is performed in step s17 to determine whether there is any change in the information of the MNO ePDG current state table 61. If there is no change, then the currently saved information is accurate, and because there is no need to send the same information twice, the process ends.

[00911 However, if there is a change, in step S19 of the first embodiment, the ePDG status information is transmitted to all hubs 17 and the process ends.

[0092] Through the above processing, the VoWiFi service monitor 27 can provide the hub 17 with current information about the status of the ePDG 25, so that the hub is aware of service loss and service recovery, so as to notify the connected VoWiFi and VoLTE-enabled UE 9 about their status. Services should be switched at the time.

[0093] The VoWiFi service monitor 27 provides a centralized network entity for monitoring the status of the ePDG 25, thereby reducing the complexity of the hub 17 and reducing network traffic when determining the status of the ePDG.

[0094] The processing of each hub 17 connected to the VoWiFi service monitor 27 will now be described. FIG. 7 is a flowchart showing the operation of the hub 17 in response to a status message from the VoWiFi service monitor 27. As described above, the VoWiFi service monitor 27 will only send a new status message when a change is detected in the logical link to at least one of the ePDGs. [0095] In step s21, the interface to the VoWiFi service monitor 41 receives the latest ePDG status message. In step s23, the content of the message is used to update the VoWiFi connection client list 45 of the hub 17.

[0096] For example, if the earlier content of the connected client list 45 before receiving the latest ePDG status message already contains the following data:

[0097]

<td>Connected device</td><td>UE MAC address</td><td>3 omissions, dare to discuss and ridicule: inverse</td><td>Logical link status of VoWiFi service</td>

<td>9a</td><td>D8: BO:3C:38:D4BB</td><td>MNO 3a ePDG server IP</td><td>:w^：.............................................-Satisfaction</td>

<td>9 b</td><td>C3:BB:3C:3S:A4:BI3</td><td>MNO 3a elOG server 11)</td><td></td>

<td>9c</td><td>D2:BB;3C:22:A4: z\A</td><td>MNO 3b eI⁵DG server IP</td><td>:Fiber:</td>

<td>9d</td><td>A3:CA:3C:21:B2:AC</td><td>MNO 3c ePDG server IP</td><td>Fiber</td>

[0098] Table 3

[0099] This will indicate that there are four VoWiFi enabled devices 9a-9d. Two of the devices 9a and 9b are users of the first MN0 3a, the third connected device 9c listed is the user of the second MN0 3b, and the fourth connected device 9d listed is the third MN0 3c User.

[0100] After receiving the latest ePDG status message containing ePDG 25c unreachable information, the connected client list 45 will be updated as follows:

<td>Not connected</td><td>UE MAC address</td><td>VoWiFi destination IP</td><td>VoWiFi service logical link status</td>

<td>9a</td><td>D8: BD:3C\3S:O4BB</td><td>MNO 3a ePDG server IP</td><td>through</td>

<td>9b</td><td>C3:BB:3C:3S:A4:BB</td><td>MNO 3a ePDG server IP</td><td>through</td>

<td>9c</td><td>O2:BB:3C:22:A4:AA</td><td>MNO 3b ePDG server IP</td><td>through</td>

<td>9d</td><td>A3:CA:3C:2I:B2:AC</td><td>MNO 3c ePDG server IP</td><td>Cut off</td>

[0102] Table 4

[0103] In step s25, the changed ePDG 25c is identified. In this example, the state of the ePDG 25c of the MNO 3c has changed.

[01041 In step s27, determine the type of change, and in particular, whether the ePDG status change involves service loss. If the ePDG status is service loss, the process moves to step s29, where the connected client list 45 is checked to determine whether there are any connected UEs affected by the service loss.

[0105] In this example, the device 9d is a user of ketone 0 3c, so even if the UE 9d does not notice because the Wi-Fi link between the UE 9d and the hub 17 is still active, it will also lose VoWiFi connectivity. Therefore, the UE 9d must be notified about the service loss.

[0106] In step s31, the hub 17 sends a notification message to any affected UEs. In this example, there is only one

The UE is affected. The notification message includes an instruction to inform the affected UE to disconnect from the VoWiFi service and the processing ends. [0107] If it is determined in step s27 that the state change is not service loss but service restoration, then in step s33, the VoWiFi monitor 39 of the hub 17 will perform a process of identifying the affected device that has previously been disconnected from VoWiFi, and then In step s35, any identified device is sent an instruction message to make the affected UE reconnect from V ο L T E to VoWiFi. The processing then ends.

[01081 Through the above processing, the hub 17 is responsible for detecting the change of the ePDG status based on the update from the VoWiFi service monitor 27, and then determining whether any of their locally connected devices is affected by the ePDG change. If there are any connected devices, the hub in this embodiment is responsible for managing the switching behavior of the UE from VoLTE to VoWiFi and from VoWiFi to VoLTE.

[0109] The components of UE 9 will now be described with reference to FIG. 4.

[0110] The UE 9 includes a cellular network interface 71 and a WLAN interface 73. The cellular interface 71 is compatible with the eNodeB 13 of the cellular network 3, and the WLAN interface 73 is compatible with the WLAN interface 31 of the hub 17.

[0111] Since the UE 9 can use the interface 71 or 73, the data link interface 75 is responsible for enabling and disabling each interface 71, 73 as needed, and is responsible for routing user data and control packets to the interface 71, 73.

[0112] The operating system 77 is responsible for the overall operation tasks performed by the UE 9, and links multiple applications and services 79 to the data layer interface 75. One of the applications within the applications and services 79 is the phone application 81, which is compatible with VoLTE and VoWiFi.

[0113] In normal operation, the phone application 61 is configured to connect to the picture Tel service 15 provided in the IMS 7 to provide voice services via VoLTE and VoWiFi. The UE 9 registers for VoWiFi when connected to the WLAN 19, and the UE 9 registers for VoLTE when connected to the LTE cellular network 3.

[0114] Within the operating system 77, the UE also has a receiver 83 for receiving instructions on VoWiFi connectivity from the hub, and the UE also has a device for moving phone services from VoLTE to VoWiFi and from VoWiFi to VoLTE.

VoLTE/VoWiFi switch control 85.

[0115] In the first embodiment, according to the switching instruction sent by the VoWiFi monitor 39, each VoWiFi-enabled UE 9 switches from VoLTE to VoWiFi and from VoWiFi to VoLTE. In particular, when the hub 17 instructs the UE 9 to switch from VoWiFi to VoLTE because the ePDG for the UE is turned off, the UE 9 will disable its VoWiFi service and enable VoLTE. However, the UE 9 will maintain the WLAN connection so that other data services continue to travel via the WLAN interface, and only the VoLTE service uses the LTE cellular connection.

[0116] Although there may be battery loss due to enabling two wireless data connections at the same time, the benefit is that only the VoLTE service is using LTE, so there is no interruption caused by switching the network adapter to other data services that may be active on the UE. In addition, most cellular users for MN0 have data usage restrictions on LTE services, and therefore it would be a negative user experience to transparently switch all data services to LTE when users think they are on WLAN (usually unmetered) .

[0117] Another benefit of maintaining the WLAN connection is that when the hub is notified that the ePDG data connection has been restored, it can use the WLAN connection to send instructions to connect back to VoWiFi.

[0118] When the UE receives such an instruction, it will switch to VoWiFi and disable the LTE interface to save power.

[0119] In the first embodiment, the VoWiFi service monitor monitors the logical data path of the ePDG of the MNO as an indication of whether the VoWiFi service is available to users of the MNO network. Since the UE prefers the standard configuration of WLAN connectivity compared to LTE cellular connectivity, if the VoWiFi service is not available, the UE will not automatically switch to VoLTE while the WLAN connection is available between the UE and the hub. When an ePDG status change is detected, the VoWiFi service monitor notifies any connected hubs. The hub receives notifications from the VoWiFi service monitor, and determines for each notification whether the ePDG status change affects one or more VoWiFi-enabled UEs connected to the hub. If at least one such device is affected by the change, the hub informs the affected UE to switch from VoWiFi to VoLTE with an indication. In this way, the UE is unlikely to miss an incoming voice call due to a failure of the VoWiFi service.

[0120] Alternatives and Modifications

[0121] In this embodiment, the centralized VoWiFi service monitor performs a check on the availability of ePDG, and then notifies the hub when there is a change in any monitored ePDG. In a modified example, the hub is configured to tell the VoWiFi service monitor which ePDGs their connected devices are using, so that the VoWiFi service monitor filters the set of monitored ePDGs and only notifies the hub when one of the related ePDGs changes. This adds to the complexity of the VoWiFi service monitor, because it must retain more complex configuration files for each registered hub. However, each hub is relatively simple because it will only listen to the ePDG status used by the connected VoWiFi device.

[0122] In this embodiment, the VoWiFi service monitor is a centralized function for monitoring the status of various ePDGs. The hub registers with the VoWiFi service monitor for status updates. This arrangement allows collating information about the entire network of MNOS. In an alternative solution, the VoWiFi service monitor does not exist, but the function of the monitor exists in each hub, that is, each hub is configured to ping the ePDG associated with the VoWiFi-connected UE to determine whether the VoWiFi service is available . Any affected UEs are notified and instructed to switch.

[0123] Since the data packet is more likely to travel along a path similar to the real VoWiFi packet, this alternative solution saves the registration routine to the external device, and also provides information about the status of the logical data link between the UE and the ePDG. More accurate assessment. For example, if there is a problem in the ISP section of the data link, even if the cause cannot be determined, the link monitor at the hub will detect the problem and instruct the VoWiFi-enabled UE to switch to VoLTE. However, due to the increase in the number of hubs sending ping packets to the ePDG, the network traffic and processing load on the ePDG will increase.