Method, system, and storage medium for n5cw device handover core network

Abstract

This invention discloses a method, system, and storage medium for switching the core network of an N5CW device, which can be widely applied in the field of 5G core network technology. This application interacts with the N5CW device through a non-3GPP reference point of the TNAN, and interacts with the AMF and UPF respectively through the TNAN. During the handover process, when the connection information weakens based on the location information of the N5CW device, the target AMF and target TWIF that can serve the current N5CW device exchange information are exchanged, and then context interaction response information is sent to the source AMF, thereby performing the handover between the source TWIF and the target TWIF. This eliminates the need for manual configuration, enabling the handover process between the current N5CW device and the core network.

Description

Technical Field

[0001] This invention relates to the field of 5G core network technology, and in particular to a method, system and storage medium for switching the core network of an N5CW device. Background Technology

[0002] In related technologies, to address the issue of insufficient uplink bandwidth in 5G NR, WiFi devices without 5G access capability (N5CW) have been introduced to meet users' uplink bandwidth needs. Currently, the common methods for N5CW device access are either through R-AN to achieve 3GPP access core network handover mode or through N3IWF to achieve non-3GPP access core network handover mode. Alternatively, in non-3GPP, TWAP and TWIF operate in a one-to-one mode, requiring users to manually switch TWAPs after leaving the TWAP before reconnecting to the 5G core network. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a method, system, and storage medium for switching the core network of N5CW devices, which can realize the automatic switching function of N5CW devices.

[0004] On one hand, embodiments of the present invention provide a method for switching the core network of an N5CW device, wherein the N5CW device interacts with a TNAN through a non-3GPP reference point, and the TNAN interacts with an AMF and a UPF respectively; the TNAN includes TWAP and TWIF, the TWIF includes a source TWIF and a target TWIF; the AMF includes a source AMF and a target AMF; the method includes the following steps:

[0005] Obtain the location information of the N5CW device;

[0006] Based on the location information, it is determined that the signal connected to the N5CW device is weakening, and a target AMF that can serve the N5CW device is obtained;

[0007] After the target AMF and the target TWIF exchange and interact, the target AMF sends context interaction response information to the source AMF.

[0008] The source AMF notifies the source TWIF that the handover preparation is complete;

[0009] The source TWIF forwards the information of the N5CW device to the target TWIF;

[0010] After the N5CW device is successfully switched over, the source AMF releases the resources of the source TWIF related to the N5CW device and the source TWIF releases the radio side resources.

[0011] In some embodiments, determining that the signal connected to the N5CW device is weakening based on the location information and obtaining a target AMF that can serve the N5CW device includes:

[0012] The source TWIF determines that the signal connected to the N5CW device is weakening based on the location information, and sends a first handover request information to the source AMF. The first handover request information includes the device identifier of the source TWIF and the IP address of the source TWIF.

[0013] When the source AMF no longer serves the N5CW device, the source AMF determines an AMF that can serve the N5CW device as the target AMF.

[0014] In some embodiments, after the target AMF and the target TWIF exchange and interact, the target AMF sends context interaction response information to the source AMF, including:

[0015] The source AMF sends a context interaction request message to the target AMF, and the context interaction request message includes the N2 context information of the N5CW device.

[0016] After the target AMF interacts with the SMF, the target AMF sends a second handover request to the target TWIF. The second handover request is used to request the establishment of radio side network resources.

[0017] The target TWIF returns handover request confirmation information to the target AMF based on the second handover request information. The handover request confirmation information includes the SM message of N2 and the address and tunnel information of N3.

[0018] The target AMF sends a context interaction response to the source AMF based on the handover request confirmation information.

[0019] In some embodiments, the source AMF notifies the source TWIF that the handover preparation is complete, including:

[0020] The source AMF sends a handover command to the source TWIF. The handover command includes the SM message and N3 address and tunnel information of the target TWIF's N2, as well as the IP address and device identifier of the target TWIF.

[0021] After receiving the handover preparation complete message, the source TWIF forwards the handover preparation complete message to the N5CW device.

[0022] In some embodiments, the source TWIF forwards information about the N5CW device to the target TWIF, including:

[0023] The source TWIF forwards the information of the N5CW device to the target TWIF based on the N3 address and tunnel information.

[0024] In some embodiments, after the source TWIF forwards the information of the N5CW device to the target TWIF, the method further includes the following steps:

[0025] After receiving the handover preparation complete message, the N5CW device obtains the IP address and device identifier of the target TWIF, and sends handover confirmation information to the target TWIF according to the IP address and device identifier of the target TWIF.

[0026] In some embodiments, the source AMF releases the resources of the source TWIF related to the N5CW device, including:

[0027] The target TWIF sends a handover notification to the target AMF, the handover notification being used to notify the target AMF that the handover was successful;

[0028] The target AMF sends a resource release notification to the source AMF based on the handover notification information. The resource release notification is used to notify the source AMF to release the resources of the source TWIF related to the N5CW device.

[0029] In some embodiments, the source TWIF releases radio-side resources, including:

[0030] After the source AMF replies to the target AMF with a resource release confirmation message, it sends a UE release command to the source TWIF. The UE release command is used to instruct the source TWIF to release radio-side resources.

[0031] The source TWIF replies to the source AMF with a resource release complete message.

[0032] On the other hand, embodiments of the present invention provide a system for switching the core network of an N5CW device, comprising:

[0033] At least one memory for storing programs;

[0034] At least one processor is used to load the program to execute the method for switching the core network of the N5CW device.

[0035] On the other hand, embodiments of the present invention provide a computer storage medium storing a computer-executable program, which, when executed by a processor, is used to implement the method for switching the core network of the N5CW device.

[0036] The method for switching the core network of an N5CW device provided in this embodiment of the invention has the following beneficial effects:

[0037] This embodiment interacts with the N5CW device through a non-3GPP reference point of the TNAN, and interacts with the AMF and UPF respectively through the TNAN. During the handover process, when the connection information is determined to be weak based on the location information of the N5CW device, the target AMF that can serve the current N5CW device exchanges and interacts with the target TWIF, and then sends context interaction response information to the source AMF, thereby performing the handover between the source TWIF and the target TWIF. Thus, the handover process between the current N5CW device and the core network can be realized without manual settings.

[0038] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0040] Figure 1 This is a schematic diagram of a 5GS architecture according to an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of another 5GS architecture according to an embodiment of the present invention;

[0042] Figure 3 This is a flowchart illustrating a method for switching the core network of an N5CW device according to an embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram illustrating the application of a method for switching the core network of an N5CW device according to an embodiment of the present invention. Detailed Implementation

[0044] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0045] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0046] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0047] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0048] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0049] Before describing specific embodiments, the terms used in the embodiments of this application are explained as follows:

[0050] 5GC: 5G Core Network, is the core of the 5G mobile network. It establishes reliable and secure network connections for end users and provides access to their services. The core domain handles various essential functions in the mobile network, such as connectivity and mobility management, authentication and authorization, user data management, and policy management. 5G core network functions are entirely software-based and designed to be cloud-native, meaning they are independent of the underlying cloud infrastructure, enabling greater deployment agility and flexibility.

[0051] AMF stands for Access and Mobility Management Function, which includes functions such as connectivity management, reachability management, mobility management, and access authorization.

[0052] T-AMF: Target AMF, which stands for Target Mobility and Mobility Management Function.

[0053] S-AMF: Source AMF, which stands for Source Mobility and Mobility Management Functions.

[0054] SMF stands for Session Management Function. Its functions include session management, such as session establishment, modification, and release, as well as channel maintenance between UPF and AN nodes.

[0055] UPF stands for User Plane Function. Its functions include session points for interconnecting external PDUs with data networks, packet routing, and forwarding. For example, it supports uplink classifiers to route traffic to the data network.

[0056] TWAP: Trusted non-3GPP access point.

[0057] T-TNAN: The full English name is Trusted Non-3GPP Access Network, which can be translated as a trusted non-3GPP access network.

[0058] N5CW: The full English name is Non-5G-Capable over WLAN, which means that the device does not support accessing 5GC NAS signaling via WLAN.

[0059] Yt: non-3gpp reference point.

[0060] Yw: non-3gpp reference point.

[0061] T-TWIF: Target TWIF, a target trusted WLAN interoperability function.

[0062] S-TWIF: Source TWIF, a source-trusted WLAN interoperability function.

[0063] N1: The N1 interface is the signaling plane interface between the terminal and the AMF.

[0064] N2: The N2 interface is the signaling plane interface between (R)AN and AMF.

[0065] N3: The N3 interface is the user plane interface between (R)AN and UPF.

[0066] WLAN stands for Wireless Local Area Network.

[0067] MCC stands for Mobile country code.

[0068] MNC stands for Mobile network code.

[0069] To address the insufficient uplink bandwidth issue in 5G NR, WiFi devices without 5G access capabilities (N5CW) have been introduced to meet users' uplink bandwidth requirements. Currently, a common networking scenario involves multiple TWAPs connecting to a single TWAF, which in turn connects to the 5G core network. Current protocols and specifications do not define automatic switching to a new TWAP and TWAF when a user moves to a new TWIF and the signal strength is stronger than the original TWAP. Therefore, how to support TNAN in selectively switching to different 5G core networks based on the strength of the connection signal to the user is a pressing issue that needs to be addressed.

[0070] Reference Figure 1 This is a 5GS architecture diagram provided in an embodiment of this application. As shown in the diagram, the N5CW device interacts with the TNAN through a non-3GPP reference point Yt. The TNAN includes TWAP and TWIF. The TWAP connects to the TWIF through the non-3GPP reference point Yw, the TWIF interacts with the AMF through N1 and N2, and the TWIF interacts with the UPF through N3. When the TNAN includes multiple TWAPs and multiple TWIFs, as shown... Figure 2 As shown, TNAN includes TWAP1, TWAP2, TWIF1, and TWIF2. The N5CW device connects to TWAP1 and TWAP2 via a non-3GPP reference point Yt. TWAP1 connects to TWIF1 via Yw, and TWAP2 connects to TWIF2 via Yw. 5GC includes, but is not limited to, AMF and UPF. TWIF1 and TWIF2 interact with 5GC via N1, N2, and N3. In this embodiment, the N5CW device interacts with AMF via the Yt interface, using TNAN as the access side, to achieve message interaction on the N1 and N2 interfaces; and interacts with UPF to achieve message interaction on the N3 interface. When the N5CW device successfully goes online via TWIF and is in a connected state, because the N5CW device moves from the source TWIF to the target TWIF node, to ensure the N5CW device can use the network normally, TWAP sends a weak user signal notification to TWIF, and TWIF initiates a handover process to the 5G core network. Ultimately, S-TWIF will transfer to T-TWIF based on the handover information sent from WLAN. Specifically, in this embodiment, when TWIF1 sends a user message to TWIF2, it will include the TWIF1 ID and device type to distinguish between TWAP and TWIF messages.

[0071] Specifically, refer to Figure 3This invention provides a method for switching the core network of an N5CW device. In this embodiment, TWIF includes a source TWIF and a target TWIF; AMF includes a source AMF and a target AMF. During execution, the method of this embodiment includes, but is not limited to, the following steps:

[0072] Step S110: Obtain the location information of the N5CW device;

[0073] Step S120: Determine that the signal connected to the N5CW device is weakening based on the location information, and obtain the target AMF that can serve the N5CW device;

[0074] In this embodiment, when the source TWIF determines that the signal connected to the N5CW device is weakening based on the location information, it can send a first handover request to the source AMF. The first handover request includes the device identifier of the source TWIF and the IP address of the source TWIF. When the source AMF no longer serves the N5CW device, an AMF that can serve the N5CW device is determined as the target AMF through the source AMF.

[0075] Step S130: After the target AMF and target TWIF exchange and interact, the target AMF sends context interaction response information to the source AMF.

[0076] In this embodiment, the source AMF sends a context interaction request message carrying N2 context information of the N5CW device to the target AMF; after the target AMF interacts with the SMF, the target AMF sends a second handover request message to the target TWIF to request the establishment of radio-side network resources; the target TWIF returns a handover request confirmation message including the N2 SM message and the N3 address and tunnel information to the target AMF according to the second handover request message; the target AMF sends a context interaction response message to the source AMF according to the handover request confirmation message.

[0077] Step S140: The source AMF notifies the source TWIF that the handover preparation is complete;

[0078] In this embodiment, the source AMF sends a handover command to the source TWIF. The handover command includes the SM message of the target TWIF's N2 and the N3 address and tunnel information, as well as the target TWIF's IP address and device identifier. After receiving the handover preparation completion message, the source TWIF forwards the handover preparation completion message to the N5CW device.

[0079] Step S150: The source TWIF forwards the information of the N5CW device to the target TWIF. Specifically, the source TWIF forwards the information of the N5CW device to the target TWIF based on the N3 address and tunnel information. Then, when the N5CW device receives the handover preparation complete message, the N5CW device obtains the IP address and device identifier of the target TWIF, and sends handover confirmation information to the target TWIF based on the IP address and device identifier of the target TWIF.

[0080] Step S160: After the N5CW device is successfully switched over, the source AMF releases the resources of the source TWIF related to the N5CW device and the source TWIF releases the wireless side resources.

[0081] In this embodiment, when releasing the resources of the source TWIF related to the N5CW device, the target TWIF can send a handover notification message to the target AMF to notify the target AMF that the handover was successful; the target AMF sends a resource release notification message to the source AMF based on the handover notification message to notify the source AMF to release the resources of the source TWIF related to the N5CW device.

[0082] When the source TWIF releases radio-side resources, it can send a UE release command to the source TWIF after replying to the target AMF with a resource release confirmation message, instructing the source TWIF to release the radio-side resources; the source TWIF then replies to the source AMF with a resource release completion message.

[0083] For example, with Figure 4 Taking the interactive scenario shown as an example, the application process of this application embodiment includes, but is not limited to, the following steps:

[0084] Step 1: Based on the location information of the N5CW device, S-TWIF determines that the connection signal with the N5CW device is weakening and sends a Handover Request message (first handover request information) to S-AMF to notify S-AMF that a device needs to be switched over. The first handover request information carries the S-TWIF device identifier and the S-TWIF IP address.

[0085] Step 2: If the S-AMF can no longer serve the N5CW device, it selects a serviceable T-AMF. The S-AMF sends a Namf_Comunication_CreateEUEContext request message (context interaction request information) to the T-AMF, initiating the handover resource allocation process. The context interaction request information carries the N2 context information of the N5CW device.

[0086] Step 3: After interacting with the SMF, the T-AMF sends a Handover Request message (second handover request information) to the T-TWIF to request the establishment of network resources on the radio side.

[0087] Step 4: After receiving the Handover Request message (second handover request information), T-TWIF returns a Handover Request Acknowledge message (handover request confirmation information) to T-AMF. The handover request confirmation information carries the SM message of N2 and the address and tunnel information of N3.

[0088] Step 5: After receiving the handover request response message from T-TWIF, T-AMF sends a Namf_Communication_CreateUEContext Response message (context interaction response information) to S-AMF.

[0089] Step Six: After receiving the response message, S-AMF sends a Handover Command message to S-TWIF to notify S-TWIF that the handover preparation is complete. This message carries the T-TWIF's N2 SM message, N3 address and tunnel information, T-TWIF's IP address, and device identifier.

[0090] Step 7: After receiving the handover preparation completion message, S-TWIF forwards it to the N5CW device.

[0091] Step 8: Based on the N3 address and tunnel information obtained from the S-AMF notification of the handover completion message, S-TWIF sends the information of the N5CW device stored in S-TWIF to T-TWIF.

[0092] Step 9: After receiving the handover preparation completion message, the N5CW device obtains the IP address and device identifier of the T-TWIF, and sends a Handover Confirm message to the T-TWIF using the IP address and device identifier.

[0093] Step 10: After receiving a successful handover notification from the N5CW, the T-TWIF sends a Handover Notify message to the T-AMF to inform the T-AMF that the handover was successful.

[0094] Step 11: After receiving the handover success message, T-AMF sends a Namf_Communication_N2InfoNotify message (resource release notification information) to S-AMF to notify S-AMF to release the resources of S-TWIF related to the N5CW device.

[0095] Step 12: S-AMF replies to T-AMF with a Namf_Communication_N2InfoNotif_Ack message (resource release confirmation message).

[0096] Step 13: S-AMF sends a UE Context Release Command message to notify S-TWIF to release the radio-side resources.

[0097] Step 14: S-TWIF replies to S-AMF with a UE Context Release Complete message (resource release complete message).

[0098] Therefore, this embodiment mainly addresses the issue of multiple TNANs within a WLAN. N5CW devices can connect to TNANs via the Yt interface, but the network signal strength of the TNANs is inconsistent. N5CW devices need to switch to a suitable and stable 5G core network. TWIFs can communicate with each other based on IP addresses and device identifiers to transfer the context and configuration of the N5CW devices to the T-TWIF, achieving handover within the WLAN. After using this embodiment, the AMF finds the UDM's NAS codec through the terminal's IMEI and directly uses it. This allows a single core network to dynamically support multiple customized NAS protocols, supporting diverse terminal deployments and service processing in various scenarios, thus improving the core network's compatibility with diverse terminals.

[0099] Furthermore, this embodiment can also notify the 5G core network through other special methods; or use other special methods to set the SSID of TWIF and TWAP to be consistent, and switch the user to the new TWIF when the 5G core network is notified, thereby realizing the selection of different TWIFs according to the strength of the connection signal with the user and accessing the 5G core network.

[0100] This invention provides a system for switching the core network of an N5CW device, comprising:

[0101] At least one memory for storing programs;

[0102] At least one processor is used to load the program for execution. Figure 3 The method for switching the core network of the N5CW device is shown.

[0103] The content of the method embodiments of the present invention is applicable to the system embodiments. The specific functions implemented in the system embodiments are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above methods.

[0104] This invention provides a computer storage medium storing a computer-executable program, which, when executed by a processor, is used to implement... Figure 3 The method for switching the core network of the N5CW device is shown.

[0105] The content of the method embodiments of the present invention is applicable to the storage medium embodiments. The specific functions implemented by the storage medium embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above methods.

[0106] Furthermore, embodiments of the present invention also provide a computer program product or computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of a computer device can read the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, causing the computer device to perform... Figure 3 The method for switching the core network of the N5CW device is shown.

[0107] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for switching the core network of an N5CW device, characterized in that, The N5CW device interacts with the TNAN via a non-3GPP reference point, and the TNAN interacts with the AMF and UPF respectively; the TNAN includes TWAP and TWIF, and the TWIF includes a source TWIF and a target TWIF; the AMF includes a source AMF and a target AMF; the method includes the following steps: Obtain the location information of the N5CW device; Based on the location information, it is determined that the signal connected to the N5CW device is weakening, and a target AMF that can serve the N5CW device is obtained; After the target AMF and the target TWIF exchange and interact, the target AMF sends context interaction response information to the source AMF. The source AMF notifies the source TWIF that the handover preparation is complete; The source TWIF forwards the information of the N5CW device to the target TWIF; After the N5CW device is successfully switched over, the source AMF releases the resources of the source TWIF related to the N5CW device and the source TWIF releases the radio side resources. 2.The method of claim 1, wherein, The step of determining that the signal connected to the N5CW device is weakening based on the location information and obtaining the target AMF that can serve the N5CW device includes: The source TWIF determines that the signal connected to the N5CW device is weakening based on the location information, and sends a first handover request information to the source AMF. The first handover request information includes the device identifier of the source TWIF and the IP address of the source TWIF. When the source AMF no longer serves the N5CW device, the source AMF determines an AMF that can serve the N5CW device as the target AMF.

3. The method of claim 1, wherein, After the target AMF and target TWIF exchange and interact, the target AMF sends context interaction response information to the source AMF, including: The source AMF sends a context interaction request message to the target AMF, and the context interaction request message includes the N2 context information of the N5CW device. After the target AMF interacts with the SMF, the target AMF sends a second handover request message to the target TWIF. The second handover request message is used to request the establishment of radio side network resources. The target TWIF returns handover request confirmation information to the target AMF based on the second handover request information. The handover request confirmation information includes the SM message of N2 and the address and tunnel information of N3. The target AMF sends a context interaction response to the source AMF based on the handover request confirmation information.

4. The method for switching the core network of an N5CW device according to claim 1, characterized in that, The source AMF notifies the source TWIF that the handover preparation is complete, including: The source AMF sends a handover command to the source TWIF. The handover command includes the SM message and N3 address and tunnel information of the target TWIF's N2, as well as the IP address and device identifier of the target TWIF. After receiving the handover preparation complete message, the source TWIF forwards the handover preparation complete message to the N5CW device.

5. The method of claim 4, wherein, The source TWIF forwards information about the N5CW device to the target TWIF, including: The source TWIF forwards the information of the N5CW device to the target TWIF based on the N3 address and tunnel information.

6. The method of claim 5, wherein, After the source TWIF forwards the information of the N5CW device to the target TWIF, the method further includes the following steps: After receiving the handover preparation complete message, the N5CW device obtains the IP address and device identifier of the target TWIF, and sends handover confirmation information to the target TWIF according to the IP address and device identifier of the target TWIF.

7. The method of claim 1, wherein, The source AMF releases the resources of the source TWIF related to the N5CW device, including: The target TWIF sends a handover notification to the target AMF, the handover notification being used to notify the target AMF that the handover was successful; The target AMF sends a resource release notification to the source AMF based on the handover notification information. The resource release notification is used to notify the source AMF to release the resources of the source TWIF related to the N5CW device. 8.The method of claim 1, wherein, The source TWIF releases radio-side resources, including: After the source AMF replies to the target AMF with a resource release confirmation message, it sends a UE release command to the source TWIF. The UE release command is used to instruct the source TWIF to release radio-side resources. The source TWIF replies to the source AMF with a resource release complete message. 9.A system for a N5CW device to switch core networks, the system comprising: include: At least one memory for storing programs; At least one processor is configured to load the program to perform the method for switching the core network of an N5CW device as described in any one of claims 1-8.

10. A computer storage medium, characterized in that, It contains a computer-executable program, which, when executed by a processor, is used to implement the method for switching the core network of an N5CW device as described in any one of claims 1-8.

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