# US 2026/0089481 A1 · Network interworking systems and methods > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2026/0089481 A1 - Document ID: US20260089481A1 - Status: Published application - Kind: A1 - Application number: 18/898,182 - Filed: 2024-09-26 - Published: 2026-03-26 - Earliest claimed: 2024-09-26 - Assignees: Boost SubscriberCo L.L.C. - Applicants: Boost SubscriberCo L.L.C. - Inventors: Jaya Chandra Chikatmarla; Kumar Anshuman; Sruthi Nair; Dawood Shahdad - Web page: https://patentgrep.com/patent/US20260089481A1 ## CPC - H04W 8/06: Registration at serving network Location Register, VLR or user mobility server - H04W 8/12: between location registers or mobility servers - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract A disclosed method may include transmitting, by a UDM function based on determining that a network interworking support database contains VLR information for a UE associated with a legacy network, a deregistration request to a Home Location Register (HLR) of a mobile network such that an HLR clears the VLR information of the UE from the network interworking support database and sends a cancellation message to a VLR of a legacy network to remove registration information for the UE such that the mobile network avoids redirecting a call for the UE to the legacy network after the UE has returned to a coverage area of the mobile network after roaming in a coverage area of the legacy network. ## Claims ### Claim 1 A method comprising: accessing, by a User Data Management (UDM) function of a mobile network, in response to receiving a registration request from a User Equipment (UE), a network interworking support database that supports interworking between the mobile network and a legacy network that operates using a mobile network standard for a specific subscriber in a roaming scenario that is of an earlier generation than the mobile network primarily uses for the specific subscriber; determining, by the UDM function, whether the network interworking support database contains Visitor Location Register (VLR) information for the UE associated with the legacy network; and transmitting, by the UDM function based on determining that the network interworking support database contains VLR information for the UE associated with the legacy network, a deregistration request to a Home Location Register (HLR) of the mobile network such that the HLR clears the VLR information of the UE from the network interworking support database and sends a cancellation message to a VLR of the legacy network to remove registration information for the UE such that the mobile network avoids redirecting a call for the UE to the legacy network after the UE has returned to a coverage area of the mobile network after roaming in a coverage area of the legacy network. ### Claim 2 (depends on 1) The method of claim 1, wherein the registration request is received from an Access and Mobility Management Function (AMF) of the mobile network. ### Claim 3 (depends on 1) The method of claim 1, wherein accessing the network interworking support database comprises performing a database read operation to retrieve Subscriber Permanent Identifier (SUPI), mobility, Serving GPRS Support Node (SGSN), and VLR information. ### Claim 4 (depends on 1) The method of claim 1, wherein: the mobile network comprises a 5G network; and the legacy network comprises a 3G network. ### Claim 5 (depends on 1) The method of claim 1, wherein the registration request comprises an IP Multimedia Subsystem (IMS) registration request. ### Claim 6 (depends on 5) The method of claim 5, further comprising performing an IMS registration for the UE after clearing the VLR information. ### Claim 7 (depends on 1) The method of claim 1, wherein the registration request comprises a location update request. ### Claim 8 (depends on 1) The method of claim 1, wherein the deregistration request comprises a NUDM_UECM_DeregistrationNotification including VLR information comprising a VLR number, a Local Mobile Subscriber Identity (LMSI), a Mobile Application Part (MAP) version, and a cancellation type. ### Claim 9 (depends on 1) The method of claim 1, wherein the cancellation message sent to the VLR comprises a Cancel Location message. ### Claim 10 (depends on 1) The method of claim 1, wherein the deregistration request prevents a Service Centralization and Continuity Application Server (SCC-AS) from performing a Terminating Access Domain Selection (T-ADS) query based on the cleared VLR information. ### Claim 11 (depends on 1) The method of claim 1, wherein clearing the VLR information prevents generation of a Provide Roaming Number (PRN) response for the UE. ### Claim 12 (depends on 1) The method of claim 1, wherein the method improves interworking between 5G and 3G networks. ### Claim 13 (depends on 1) The method of claim 1, further comprising updating a Home Subscriber Server (HSS) to reflect the cleared VLR information. ### Claim 14 (depends on 1) The method of claim 1, wherein the VLR information remains in the network interworking support database based on the UE failing to deregister from the legacy network due to loss of coverage or battery depletion. ### Claim 15 (depends on 1) The method of claim 1, wherein the VLR information remains in the network interworking support database based on a Mobile Switching Center (MSC) of the legacy network failing to send a purge request. ### Claim 16 (depends on 1) The method of claim 1, further comprising performing a Lightweight Directory Access Protocol (LDAP) update to delete VLR and SGSN address information from the network interworking support database. ### Claim 17 A non-transitory computer-readable medium that has instructions stored thereon that, when executed by at least one physical computing processor, cause a computing device to perform operations comprising: accessing, by a User Data Management (UDM) function of a mobile network, in response to receiving a registration request from a User Equipment (UE), a network interworking support database that supports interworking between the mobile network and a legacy network that operates using a mobile network standard for a specific subscriber in a roaming scenario that is of an earlier generation than the mobile network primarily uses for the specific subscriber; determining, by the UDM function, whether the network interworking support database contains Visitor Location Register (VLR) information for the UE associated with the legacy network; and transmitting, by the UDM function based on determining that the network interworking support database contains VLR information for the UE associated with the legacy network, a deregistration request to a Home Location Register (HLR) of the mobile network such that the HLR clears the VLR information of the UE from the network interworking support database and sends a cancellation message to a VLR of the legacy network to remove registration information for the UE such that the mobile network avoids redirecting a call for the UE to the legacy network after the UE has returned to a coverage area of the mobile network after roaming in a coverage area of the legacy network. ### Claim 18 (depends on 17) The non-transitory computer-readable medium of claim 17, wherein the registration request is received from an Access and Mobility Management Function (AMF) of the mobile network. ### Claim 19 A system comprising: at least one physical computing processor of a computing device; and a non-transitory computer-readable medium that has instructions stored thereon that, when executed by the at least one physical computing processor, cause the computing device to perform operations comprising: accessing, by a User Data Management (UDM) function of a mobile network, in response to receiving a registration request from a User Equipment (UE), a network interworking support database that supports interworking between the mobile network and a legacy network that operates using a mobile network standard for a specific subscriber in a roaming scenario that is of an earlier generation than the mobile network primarily uses for the specific subscriber; determining, by the UDM function, whether the network interworking support database contains Visitor Location Register (VLR) information for the UE associated with the legacy network; and transmitting, by the UDM function based on determining that the network interworking support database contains VLR information for the UE associated with the legacy network, a deregistration request to a Home Location Register (HLR) of the mobile network such that the HLR clears the VLR information of the UE from the network interworking support database and sends a cancellation message to a VLR of the legacy network to remove registration information for the UE such that the mobile network avoids redirecting a call for the UE to the legacy network after the UE has returned to a coverage area of the mobile network after roaming in a coverage area of the legacy network. ### Claim 20 (depends on 19) The system of claim 19, wherein the registration request is received from an Access and Mobility Management Function (AMF) of the mobile network.