PATENT DOCUMENT

Publication Number: US-11889589-B2
Application Number: US-202217958031-A
Country: US
Kind Code: B2

Title: Communications network

Abstract:
A communications network may be used to convey Short Message Service (SMS) messages using the Internet Protocol (IP). User equipment may transmit an SMS-over-IP Session Initiation Protocol (SIP) message to wireless equipment over a high-bandwidth communications link. The wireless equipment may route the SMS-over-IP SIP message to the ePDG. When the high-bandwidth link is unavailable, the user equipment may transmit a compressed message to the proxy server over a low-bandwidth communications link. The proxy server may convert the compressed message into an SMS-over-IP SIP message that is transmitted to the ePDG. The proxy server may serve as a proxy for the first user equipment from the perspective of the ePDG. This may allow SMS message data to continue to be conveyed through the communications network even when the high-bandwidth communications link becomes unavailable.

Claims:
What is claimed is: 
     
       1. A user equipment device comprising:
 one or more antennas; and 
 wireless circuitry configured to use the one or more antennas to:
 transmit message data over a first communications link having a first bandwidth, and 
 while the first communications link is unavailable, transmit, over a second communications link, a compressed message that is free of Short Message Service (SMS) headers, the second communications link having a second bandwidth that is less than the first bandwidth. 
 
 
     
     
       2. The user equipment device of  claim 1 , wherein the compressed message is encapsulated using a compression algorithm associated with the second communications link. 
     
     
       3. The user equipment device of  claim 2 , wherein the compressed message is free of IP Multimedia Subsystem (IMS) headers. 
     
     
       4. The user equipment device of  claim 3 , wherein the message data transmitted over the first communications link comprises an SMS header and an IMS header and wherein the compressed message comprises a link layer header. 
     
     
       5. The user equipment device of  claim 1 , wherein the message data comprises Short Message Service (SMS) message data. 
     
     
       6. The user equipment device of  claim 1 , wherein the first communications link forms part of an overlying network tunnel that terminates at the user equipment device and at an Evolved Packet Data Gateway (ePDG), and wherein the network tunnel runs through a wireless access point or a wireless base station. 
     
     
       7. The user equipment device of  claim 6 , wherein the second communications link forms part of an additional network tunnel that terminates at the user equipment device and a proxy server. 
     
     
       8. The user equipment device of  claim 1 , wherein the message data transmitted over the first communications link forms part of a Session Initiation Protocol (SIP) message. 
     
     
       9. The user equipment device of  claim 1 , wherein the first communications link uses a first communications protocol and the second communications link uses a second communications protocol that is different from the first communications protocol. 
     
     
       10. A method of operating a communications network to convey message data from first user equipment to second user equipment, wherein the communications network comprises a network node, a wireless base station, and a proxy server, the method comprising:
 with the wireless base station, receiving a first message from the first user equipment over a first communications link having a first bandwidth; 
 with the wireless base station, routing the first message to the network node; 
 with the network node, receiving the first message over a first network tunnel that runs from the first user equipment to the network node and through the wireless base station; and 
 with the proxy server, while the first communications link is unavailable, receiving message data from the first user equipment over a second communications link, the second communications link having a second bandwidth that is less than the first bandwidth. 
 
     
     
       11. The method of  claim 10 , further comprising:
 with the proxy server, converting the message data received from the first user equipment into a second message; and 
 with the proxy server, transmitting the second message to the network node. 
 
     
     
       12. The method of  claim 11 , further comprising:
 with the proxy server, receiving a third message from the network node, the third message comprising additional message data transmitted by the second user equipment; 
 with the proxy server, extracting, from the third message, the third message data transmitted by the second user equipment; 
 with the proxy server, generating a compressed message by encapsulating, using a compression algorithm associated with the second communications link, the third message data transmitted by the second user equipment; and 
 with the proxy server, transmitting the compressed message to the first user equipment over the second communications link. 
 
     
     
       13. The method of  claim 11 , further comprising:
 with the network node, receiving the second message over a second network tunnel from the proxy server to the network node. 
 
     
     
       14. The method of  claim 13 , wherein receiving the message data from the first user equipment over the second communications link comprises receiving the message data over a third network tunnel that terminates at the first user equipment and the proxy server. 
     
     
       15. The method of  claim 13 , wherein the second communications link comprises a wireless communications link having the second bandwidth and a network selected from the group consisting of: a relay network, a mesh network, a star network, a ring network, and a tree network. 
     
     
       16. The method of  claim 11 , further comprising:
 with the proxy server, receiving carrier configuration file information from a carrier configuration file server; 
 with the proxy server, while the first communications link is unavailable, receiving configuration data from the first user equipment over the second communications link; 
 with the proxy server, identifying, based on the configuration data and the carrier configuration file information, a network address of the network node; 
 with the proxy server, after the network address of the network node has been identified, transmitting an authentication request to an authentication server via the network node; 
 with the proxy server, receiving a response to the authentication request from the authentication server through the network node, the response to the authentication request being addressed to the proxy server; 
 with the proxy server, transmitting the response to the authentication request to the first user equipment over the second communications link; 
 with the proxy server, receiving a subscriber identity module (SIM) challenge response from the first user equipment over the second communications link; 
 with the proxy server, transmitting the SIM challenge response to the authentication server via the network node; 
 with the proxy server, receiving, via the network node, an acknowledgement indicative of the SIM challenge response being verified by the authentication server; and 
 with the proxy server and after the acknowledgement has been received, transmitting, via the network node and a network tunnel extending from the proxy server to the network node, an IP Multimedia Subsystem (IMS) registration request to the authentication server. 
 
     
     
       17. A method of operating a user equipment device, the method comprising:
 transmitting, using one or more antennas, message data over a first communications link having a first bandwidth, the first communications link comprising a first network tunnel from the user equipment device to a network node; and 
 while the first communications link is unavailable, transmitting, using the one or more antennas, over a second communications link, a compressed message, the second communications link having a second bandwidth that is less than the first bandwidth. 
 
     
     
       18. The method of  claim 17 , wherein transmitting the message data over the first communications link comprises transmitting the message data at a first frequency and using a first communications protocol, transmitting the compressed message over the second communications link comprises transmitting the compressed message at a second frequency and using a second communications protocol, the second frequency is different from the first frequency, and the second communications protocol is different from the first communications protocol. 
     
     
       19. The method of  claim 18 ,
 wherein the second communications link comprises a second network tunnel that runs from the user equipment device to a proxy server different from the network node. 
 
     
     
       20. The method of  claim 19 , wherein transmitting the message data over the first communications link comprises wirelessly transmitting the message data to a wireless base station, transmitting the compressed message comprises wirelessly transmitting the compressed message to a network device other than the wireless base station and the network node, the first network tunnel runs through the wireless base station, and the second network tunnel runs through the network device.

Description:
This application is a continuation of U.S. patent application Ser. No. 16/595,260, filed Oct. 7, 2019, which claims the benefit of provisional patent application No. 62/871,585, filed Jul. 8, 2019, each of which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to communications networks, and, more particularly, to communications networks for conveying Short Message Service (SMS) messages. 
     BACKGROUND 
     Communications networks are used to convey data messages between first user equipment and second user equipment. The data messages often include text-based messages such as Short Message Service (SMS) messages. SMS messages are conveyed between the first user equipment and a carrier core network by a cellular base station (i.e., using radio-frequency signals in a cellular telephone frequency band). 
     Many communications networks have SMS-over-IP capabilities in which an SMS message to or from carrier-authorized first user equipment is included in an SMS-over-IP message conveyed over the internet or other networks that operate using the Internet Protocol (IP). A network carrier that manages the carrier core network also operates a carrier Evolved Packet Data Gateway (ePDG) that is communicatively coupled to the carrier core network. The SMS-over-IP messages are conveyed between the first user equipment and the carrier ePDG through the Internet as well as additional networks not operated by the carrier such as a local wireless access point (i.e., using radio-frequency signals in a wireless local area network frequency band). 
     The ability to convey SMS message data between the first user equipment and the second user equipment typically depends upon the availability of a first wireless communications link between the first user equipment and the cellular base station or a second communications link between the first user equipment and the Internet. If care is not taken, the first user equipment and the second user equipment may be unable to convey SMS message data through the communications network when the first and second communications links are unavailable. 
     SUMMARY 
     A communications network may be used to convey Short Message Service (SMS) message data between first and second user equipment using the Internet Protocol (IP). The communications network may include Internet-supplying networking equipment such as a router or a wireless access point, a proxy server, and an Evolved Packet Data Gateway (ePDG). The first user equipment may wirelessly transmit an SMS-over-IP Session Initiation Protocol (SIP) message that includes SMS message data over a first communications link between the first user equipment and the Internet-supplying networking equipment. The internet-supplying networking equipment may route the SMS-over-IP SIP message to the ePDG through the Internet. The SMS-over-IP SIP message may, for example, be transmitted over a network tunnel that overlies the wireless equipment, the Internet, and the first communications link and that terminates at the ePDG and the first user equipment. 
     The first user equipment may determine when the first communications link is unavailable (e.g., when the first user equipment is out of range of the wireless equipment or when the Internet is unavailable). When the first communications link is unavailable, the first user equipment may encapsulate the SMS message data to form a compressed message. The first user equipment may wirelessly transmit the compressed message to the proxy server over a second communications link having a bandwidth that is less than that of the first communications link. The proxy server may convert the compressed message into an SMS-over-IP SIP message. For example, the proxy server may de-encapsulate and decompress the compressed message to recover the SMS message data. The proxy server may then re-encapsulate the SMS message data to generate the SMS-over-IP SIP message. The proxy server may transmit the SMS-over-IP SIP message to the ePDG (e.g., over a network tunnel that terminates at the proxy server and the ePDG). 
     This process may be reversed to receive SMS message data transmitted by the second user equipment at the first user equipment. The carrier ePDG may transmit the SMS message from the second user equipment to the proxy server in an SMS-over-IP SIP message. The proxy server may convert the SMS-over-IP SIP message received from the ePDG into a compressed message that is provided to the first user equipment over the second communications link. The SMS-over-IP SIP messages conveyed by the proxy server may be indistinguishable to the carrier ePDG from the SMS-over-IP messages conveyed through the wireless equipment. In this way, the proxy server may serve as a proxy for the first user equipment from the perspective of the ePDG when the first communications link is unavailable. This may allow SMS message data to continue to be conveyed between the first and second user equipment even when the first communications link is unavailable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an illustrative communications network that conveys Short Message Service (SMS) message data in accordance with some embodiments. 
         FIG.  2    is a schematic diagram of illustrative user equipment for conveying SMS message data over a communications network in accordance with some embodiments. 
         FIG.  3    is a flow chart of illustrative steps involved in using a communications network to convey SMS message data via a low-bandwidth communications link and a proxy server when high-bandwidth communications links are unavailable in accordance with some embodiments. 
         FIG.  4    is a flow chart of illustrative steps involved in establishing and authenticating a logical network path between user equipment and a carrier Evolved Packet Data Gateway (ePDG) via a low-bandwidth communications link and a proxy server in accordance with some embodiments. 
         FIG.  5    is a flow chart of illustrative steps involved in transmitting SMS message data from user equipment to a carrier ePDG via a low-bandwidth communications link and a proxy server in accordance with some embodiments. 
         FIG.  6    is a flow chart of illustrative steps involved in receiving SMS message data at user equipment via a proxy server and a low-bandwidth communications link in accordance with some embodiments. 
         FIG.  7    is flow diagram showing how illustrative user equipment may transmit SMS message data over a high-bandwidth communications link and then over a low-bandwidth communications when the high-bandwidth communications link is unavailable in accordance with some embodiments. 
         FIG.  8    is flow diagram showing how illustrative user equipment may receive SMS message data over a high-bandwidth communications link and then over a low-bandwidth communications link when the high-bandwidth communications link is unavailable in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     A communications network may include first user equipment and second user equipment. The first user equipment may transmit messages to the second user equipment and may receive messages from the second user equipment. The communications network may include a carrier core network that is operated by a network carrier or service provider. The communications network may also include a carrier Evolved Packet Data Gateway (ePDG) that is operated by the network carrier. 
     The communications network may convey message data such as Short Message Service (SMS) message data between the first and second user equipment. The SMS message data may be included in SMS messages that are conveyed between the carrier core network and the first user equipment via a cellular base station (e.g., over a cellular telephone communications link). The SMS message data may also be included in SMS-over-IP messages that are conveyed by the communications network using the Internet Protocol (IP). SMS-over-IP messages may be conveyed between the carrier core network and the first user equipment via the carrier ePDG and a wireless access point (e.g., the SMS-over-IP messages may be conveyed between the wireless access point and the first user equipment over a wireless local area network communications link). If desired, the SMS-over-IP messages may also be conveyed between the carrier core network and the first user equipment via the carrier ePDG and the cellular base station (e.g., in scenarios where the cellular telephone communications link is capable of conveying SMS-over-IP messages). The SMS-over-IP messages are Session Initiation Protocol (SIP) messages and may therefore sometimes be referred to herein as SMS-over-IP SIP messages or simply as SIP messages. 
     The cellular telephone communications link and the wireless local area network communications link are high-bandwidth communications links that support relatively high data rates (e.g., 100 kB/s or more, 1 MB/s or more, 10 MB/s or more, 1 GB/s or more, etc.). The communications network may also include a proxy server that communicates with the first user equipment over a low-bandwidth communications link. The low-bandwidth communications link may operate using relatively low data rates (e.g., 100 kB/s or less, 10 kB/s or less, 1 kB/s or less, or other data rates that are lower than the data rates of the high-bandwidth communications links). The first user equipment may still be able to communicate with the proxy server over the low-bandwidth communications link when the first user equipment is unable to communicate over the high-bandwidth communications links (e.g., when the first user equipment has moved out of range of the cellular base station and wireless access point or when the Internet is unavailable). 
     When the high-bandwidth communications links are unavailable to the first user equipment, the communications network may establish and authenticate a logical network path between the first user equipment and the carrier ePDG via the proxy server and the low-bandwidth communications link. The logical network path may include a first path between the first user equipment and the proxy server and a second path that includes a secure network tunnel between the proxy server and the carrier ePDG. Once the logical network path has been established, the first user equipment may generate a compressed message that includes SMS message data to convey to the second user equipment. The first user equipment may generate the compressed message by encapsulating the SMS message data using a compression algorithm associated with the low-bandwidth communications link. The first user equipment may transmit the compressed message to the proxy server over the low-bandwidth communications link. 
     The proxy server may unpack (de-encapsulate) the SMS message data from the compressed message using a decompression algorithm associated with the low-bandwidth communications link. The proxy server may re-pack (re-encapsulate) the unpacked SMS message data to produce an SMS-over-IP SIP message. The proxy server may transmit the SMS-over-IP SIP message to the carrier ePDG (e.g., over the secure network tunnel), which conveys the SMS-over-IP SIP message or the SMS message data from the SMS-over-IP message to the carrier core network. The carrier core network may provide the SMS-over-IP SIP message or the SMS message data from the SMS-over-IP SIP message to an SMS controller. The SMS controller may forward the SMS message data to the second user equipment (e.g., as an SMS message or SMS-over-IP message conveyed to the second user equipment over a different carrier core network or the same carrier core network). To the carrier ePDG, the SMS-over-IP SIP message received from the proxy server may appear indistinguishable from SMS-over-IP SIP messages conveyed to the carrier ePDG via the cellular base station and the wireless access point. This process may be reversed to convey SMS message data from the second user equipment to the first user equipment via the proxy server and the low-bandwidth communications link when the high-bandwidth communications links are unavailable. 
       FIG.  1    is a schematic diagram of an illustrative communications network (system)  10  for conveying SMS message data or other message data between first user equipment (UE)  12  and second user equipment  14 . As shown in  FIG.  1   , communications network  10  may include carrier core network  16 , carrier ePDG  24 , authentication server  26 , SMS controller  18 , network portion  32 , carrier configuration file server  28 , proxy server  30 , one or more cellular base stations  22 , and one or more wireless access points  20 . Cellular base station  22  and/or wireless access point  20  may be omitted if desired. Cellular base station  22  and wireless access point  20  may sometimes be referred to collectively herein as high-bandwidth wireless equipment or simply as wireless equipment. 
     First user equipment  12  may communicate with cellular base station  22  over a high-bandwidth communications link such as high-bandwidth communications link  36 . Cellular base station  22  may communicate with carrier core network  16  over data path  38 . If desired, cellular base station  22  may communicate with carrier ePDG  24  over a corresponding data path (not shown in  FIG.  1    for the sake of clarity). First user equipment  12  may communicate with wireless access point  20  over a high-bandwidth communications link such as high-bandwidth communications link  34 . Wireless access point  20  may communicate with carrier ePDG  24  over data path  40 . Carrier ePDG  24  may communicate with carrier core network  16  over data path  42 . Proxy server  30  may communicate with carrier ePDG  24  over data path  52  and may communicate with carrier configuration file server  28  over data path  48 . Carrier core network  16  may communicate with authentication server  26  over data path  46  and may communicate with SMS controller  18  over data path  44 . 
     Data paths  38 ,  40 ,  42 ,  44 ,  46 ,  48 , and  52  may sometimes be referred to herein as communications paths or communications data paths. Data paths  38 ,  40 ,  42 ,  44 ,  46 ,  48 , and  52  may each include one or more wired communications links (e.g., communications links formed using cabling such as ethernet cables, radio-frequency cables such as coaxial cables or other transmission lines, optical fibers or other optical cables, etc.), one or more wireless communications links (e.g., short range wireless communications links that operate over a range of inches, feet, or tens of feet, medium range wireless communications links that operate over a range of hundreds of feet, thousands of feet, miles, or tens of miles, and/or long range wireless communications links that operate over a range of hundreds or thousands of miles, etc.), switches, routers, servers, modems, repeaters, telephone lines, network cards, line cards, communications gateways, portals, user equipment (e.g., computing devices, mobile devices, etc.), wireless access points, base stations, some or all of a network of communications (network) nodes or terminals coupled together using these components or other components (e.g., some or all of a mesh network, relay network, ring network, local area network, wireless local area network, personal area network, cloud network, star network, tree network, or networks of communications nodes having other network topologies), the Internet, combinations of these, etc. 
     SMS controller  18  may communicate with second user equipment  14  over network portion  32 . Network portion  32  may include one or more communications links, data paths, wireless access points, cellular base stations, proxy servers, carrier ePDGs, carrier core networks, and/or carrier configuration file servers. Carrier core network  16  and carrier ePDG  24  of  FIG.  1    may be operated by a corresponding network carrier or service provider. In one suitable arrangement, network portion  32  may include a carrier core network, carrier ePDGs, and other components that are operated by a different network carrier than the network carrier associated with carrier core network  16  and carrier ePDG  24 . In another suitable arrangement, network portion  32  may be operated by the same network carrier or service provider as carrier core network  16  and carrier ePDG  24  (e.g., network portion  32  may include one or more of carrier core network  16 , carrier ePDG  24 , cellular base station  22 , wireless access point  20 , carrier configuration file server  28 , and data paths  38 ,  40 ,  42 ,  44 , and  46  in a scenario where second user equipment  14  and first user equipment  12  both subscribe to the same network carrier). 
     In practice, first user equipment  12  may only communicate using high-bandwidth communications links  36  and  34  when user equipment  12  is located within range of cellular base station  22  or wireless access point  20 . When user equipment  12  is located outside the range of cellular base station  22  and wireless access point  20  (or whenever high-bandwidth communications links  36  and  34  are otherwise unavailable), first user equipment  12  may communicate with carrier ePDG  24  via proxy server  30  and low-bandwidth communications link  50 . First user equipment  12  and proxy server  30  may be able to convey data over low-bandwidth communications link  50  even when high-bandwidth communications links  34  and  36  are unavailable. Proxy server  30  may be implemented on a computer, server, or any other computing equipment. If desired, proxy server  30  may be implemented on a distributed computer system such as a cloud-based computer network. For example, proxy server  30  may be logically defined as a virtual machine or server that is implemented (distributed) across two or more underlying physical computers, servers, network terminals, network nodes, or other computing equipment at one or more geographic locations. 
     Low-bandwidth communications link  50  may support data transfer using a relatively low data rate (e.g., 100 kB/s or less, 10 kB/s or less, 1 kB/s or less, or other data rates that are less than the data rates supported by high-bandwidth communications links  34  and  36 ). In other words, low-bandwidth communications link  50  may support data transfer using relatively low bandwidths (and/or data rates) that are lower than the relatively high bandwidths (and/or data rates) supported by high-bandwidth communications links  34  and  36 . Low-bandwidth communications link  50  may include one or more low-bandwidth wireless communications links (e.g., wireless communications links that convey data using the relatively low bandwidth and data rate). The low-bandwidth wireless communications links in low-bandwidth communications link  50  may be short range wireless communications links that operate over a range of inches, feet, or tens of feet, medium range wireless communications links that operate over a range of hundreds of feet, thousands of feet, miles, or tens of miles, and/or long range wireless communications links that operate over a range of hundreds or thousands of miles, etc. The low-bandwidth wireless communications links may wirelessly convey data over any desired frequency bands (e.g., frequency bands that are different from the frequency bands handled by high-bandwidth communications links  34  and  36  or one or more of the same frequency bands as those handled by high-bandwidth communications links  34  and  36 ). Low-bandwidth communications link  50  may be a direct connection between first user equipment  12  and proxy server  30  or may include multiple network nodes that convey data using at least one low-bandwidth wireless communications link and one or more other wireless or wired communications links. For example, low-bandwidth communications link  50  may include a relay network, a mesh network, a star network, a tree network, a ring network, a local area network, a wireless local area network, combinations of these, and/or a network of network nodes having other network topologies. 
     First user equipment  12  and second user equipment  14  may convey text-based message data such as SMS message data over communications network  10 . The SMS message data may be included in SMS messages and/or SMS-over-IP SIP messages (e.g., the SMS message data may form a data payload for the SMS messages or SMS-over-IP SIP messages and may include text or other input generated by software applications running on the user equipment or provided by a user via input/output devices on or coupled to the user equipment). The SMS messages may include an SMS header in addition to the SMS message data. The SMS-over-IP SIP messages may include an SMS header and other headers such as an IP Multimedia Subsystem (IMS) header in addition to the SMS message data. Communications network  10  may use the SMS header in the SMS messages and the SMS and IMS headers in the SMS-over-IP SIP messages to help determine where to route the SMS message data to reach a desired message destination. 
     When first user equipment  12  is in range of cellular base station  22 , first user equipment  12  may transmit an SMS message to cellular base station  22  over high-bandwidth communications link  36 . Cellular base station  22  may relay the SMS message to carrier core network  16  over data path  38 . Carrier core network  16  may transmit the SMS message data from the SMS message to SMS controller  18  over data path  44 . SMS controller  18  may convey the SMS message data to second user equipment  14  via network portion  32 . 
     When first user equipment  12  is in range of wireless access point  20 , first user equipment  12  may transmit an SMS-over-IP SIP message to wireless access point  20  over high-bandwidth communications link  34 . Wireless access point  20  may route the SMS-over-IP SIP message to carrier ePDG  24  over data path  40 . Carrier ePDG  24  is a node or gateway that is communicatively coupled to carrier core network  16  via data path  42 . Carrier ePDG may transmit the SMS-over-IP SIP message to carrier core network  16  over data path  42 . Carrier core network  16  may parse and process the SMS-over-IP SIP message and may convey the SMS-over-IP SIP message or the corresponding SMS message data from the SMS-over-IP SIP message to SMS controller  18 . SMS controller  18  may convey the SMS message data to second user equipment  14  via network portion  32 . 
     A secure network tunnel such as an Internet Protocol Security (IPSec) tunnel may be established between carrier ePDG  24  and first user equipment  12  (through wireless access point  20 ) using authentication information (e.g., security keys or other information) stored at authentication server  26 . The SMS-over-IP SIP message may be conveyed between first user equipment  12  and carrier ePDG  24  over the IPSec tunnel (e.g., via the underlying high-bandwidth communications link  34 , wireless access point  20 , and data path  40 ). If desired, the SMS-over-IP SIP message may additionally or alternatively be conveyed between first user equipment  12  and carrier ePDG  24  via cellular base station  22  and high-bandwidth communications link  36  (e.g., in scenarios where high-bandwidth communications link  36  is a cellular telephone communications link capable of conveying SMS-over-IP messages such as a 4G LTE link). These processes may be reversed to receive SMS message data at first user equipment  12  (e.g., SMS message data transmitted by second user equipment  14 ). 
     When high-bandwidth communications links  36  and  34  are unavailable to first user equipment  12 , first user equipment  12  may convey SMS message data using low-bandwidth communications link  50  and proxy server  30  instead of using high-bandwidth communications links  36  and  34 , cellular base station  22 , and wireless access point  20 . Information stored at authentication server  26  and carrier configuration file server  28  may be used in establishing and securing a logical network path between first user equipment  12  and carrier ePDG  24 . The logical network path may include one or more secure network tunnels such as a first network tunnel between first user equipment  12  and proxy server  30  (e.g., SMS message data conveyed over low-bandwidth communications link  50  may be encapsulated using a protocol associated with low-bandwidth communications link  50 ) and a second network tunnel between proxy server  30  and carrier ePDG  24  (e.g., an IPSec tunnel). Proxy server  30  may convert the SMS message data between a low-bandwidth format associated with low-bandwidth communications link  50  and a high-bandwidth format associated with data path  52  (e.g., an SMS-over-IP SIP message). Proxy server  30  and low-bandwidth communications link  50  may allow for seamless or near-seamless communications between second user equipment  14  and first user equipment  12  using SMS-over-IP messages even when high-bandwidth communications links  36  and  34  become unavailable to first user equipment  12 . 
     The example of  FIG.  1    is merely illustrative. First user equipment  12  and second user equipment  14  may convey SMS-over-IP information whenever first user equipment  12  is connected to a network that can communicate via the Internet Protocol with carrier ePDG  24 . For example, first user equipment  12  may be communicatively coupled to a network that has high speed IP connectivity to carrier ePDG  24  such as an access point connected to the public Internet. However, first user equipment  12  need not communicate with carrier ePDG via the public Internet. In other words, access point  20  may be an access point with Internet access or may be hardwired to a private IP network that is directly connected to the carrier (e.g., data path  40  may include the public Internet or a private IP network). For example, access point  20  may be a subscriber identity module (SIM)-based Internet of Things (IoT) device hard-wired to a corporate network that peers with the carrier. In this example, access point  20  may be a device with no Internet or wireless capability but that still conveys SMS-over-IP information between first user equipment  12  and carrier ePDG  24 . High-bandwidth communications link  34  may be replaced by a wired link and need not be wireless in this or in other examples. 
     While low-bandwidth communications link  50  is described herein as being a low-bandwidth link, the methods described herein may be used for any second communications link (e.g., in place of low-bandwidth communications link  50  of  FIG.  1   ) that does not fit the criteria of being able to connect to a network that has high speed IP connectivity to carrier ePDG  24  (e.g., via access point  20 ) and that is not connected to the carrier over a cellular telephone communications link. This communication may be low-bandwidth, may occur when first user equipment  12  is connected to a network that does not have IP connectivity to carrier ePDG  24  such as a corporate network that does not have Internet, or may be high speed without communicating using IP (e.g., a high speed network that does not have SIM-based devices that need to send SMS messages, a private IP corporate network without Internet connectivity, etc.). In other words, low-bandwidth communications link  50  need not be low-bandwidth and may, in general, be any communications link that does not fit the criteria of being able to connect to a network that has high speed IP connectivity to carrier ePDG  24 . 
       FIG.  2    is a schematic diagram of first user equipment  12 . First user equipment  12  may be a portable electronic device such as a cellular telephone, portable media player, wearable electronic device (e.g., wristwatch), laptop computer, tablet computer, gaming controller, remote control, or electronic navigation device, other larger electronic devices such as a desktop computer, television, set-top box, home entertainment system, server, or computer monitor, or may include electronic equipment integrated into a larger system such as a kiosk, building, or vehicle. First user equipment  12  may include a housing having housing walls formed from dielectric and/or conductive materials. Second user equipment  14  of  FIG.  1    may include any of these types of equipment. In another suitable arrangement, second user equipment  14  may include Internet service equipment. Information conveyed between first user equipment  12  and second user equipment  14  may include any desired information (e.g., message data, application data, image data, video data, email data, webpage data, authentication data such as two-factor authentication codes, real-time chat data, etc.). 
     As shown in  FIG.  2   , first user equipment  12  may include control circuitry  54 , input/output devices  60 , and wireless circuitry  62 . Control circuitry  54  may include storage such as storage  58 . Storage  58  may include volatile memory (e.g., static or dynamic random-access-memory), nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory), hard drive storage, etc. Control circuitry  54  may also include processing circuitry  56 . Processing circuitry  56  may control the operation of first user equipment  12 . Processing circuitry  56  may include one or more application specific integrated circuits, microprocessors, microcontrollers, baseband processor integrated circuits, central processing units, digital signal processors, etc. 
     Control circuitry  54  may be used to run software on first user equipment  12  such as operating system functions, software applications, etc. For example, storage  58  may store computer code or other software instructions that are executed by processing circuitry  56 . The computer code may be stored on a non-transitory computer readable storage medium (e.g., storage  58  or a removable storage medium). Control circuitry  54  may also be used in implementing wireless communications protocols (e.g., wireless communications protocols associated with different radio-access technologies that are used to wirelessly convey data over wireless communications links in high-bandwidth communications links  34  and  36  and low-bandwidth communications link  50  of  FIG.  1   ). 
     Input/output devices  60  are used in providing input to and output from first user equipment  12 . For example, input/output devices  60  may include one or more displays (e.g., touch sensitive displays, liquid crystal displays, light emitting diode displays, etc.), sensors (e.g., light sensors, proximity sensors, range sensors, image sensors, audio sensors such as microphones, force sensors, moisture sensors, humidity sensors, fingerprint sensors, pressure sensors, touch sensors, ultrasonic sensors, accelerometers, gyroscopes, compasses, etc.), status indicator lights, speakers, vibrators, keyboards, touch pads, buttons, joysticks, etc. 
     Wireless circuitry  62  may include radio-frequency transceivers  64  and one or more antennas  66  for wirelessly communicating with external equipment (e.g., cellular base station  22 , wireless access point  20 , and proxy server  30  of  FIG.  1   ). Antennas  66  may include any desired types of antennas such as patch antennas, dipole antennas, monopole antennas, inverted-F antennas, planar inverted-F antennas, slot antennas, helical antennas, combinations of these and/or other types of antennas, etc. Transceivers  64  may be used to transmit and receive radio-frequency signals using antennas  66 . Transceivers  64  may each be formed from respective integrated circuits or may share one or more integrated circuits. Transceivers  64  may include mixer circuitry, analog-to-digital converter circuitry, digital-to-analog transceiver circuitry, amplifier circuitry, and/or any other desired components for transmitting and receiving radio-frequency signals. Wireless circuitry  62  may also include baseband processor circuitry, transmission line structures, filter circuitry, switching circuitry, and/or any other desired circuitry for transmitting and receiving wireless radio-frequency signals using antennas  66 . 
     If desired, each transceiver  64  may handle radio-frequency signals using a different respective radio access technology and/or frequency band. For example, a first transceiver  64  may handle communications over high-bandwidth communications link  36  of  FIG.  1    using a first radio access technology and/or a first frequency band, a second transceiver  64  may handle communications over high-bandwidth communications link  34  using a second radio access technology and/or a second frequency band, and a third transceiver  64  may handle communications over low-bandwidth communications link  50  using a third radio access technology and/or a third frequency band. This is merely illustrative and, if desired, the same radio access technology and/or frequency band may be used to handle one, two, or each of low-bandwidth communications link  50 , high-bandwidth communications link  34 , and high-bandwidth communications link  36 . Similar components may be used to form second user equipment  14  of  FIG.  1    if desired. 
       FIG.  3    is a flow chart of illustrative steps that may be performed by communications network  10  of  FIG.  1    to convey SMS message data between first user equipment  12  and second user equipment  14 . The steps of  FIG.  3    may, for example, allow for seamless or near-seamless communications between second user equipment  14  and first user equipment  12  using SMS message data even after high-bandwidth communications links  36  and  34  have become unavailable to first user equipment  12 . 
     At step  70  of  FIG.  3   , communications network  10  may convey SMS message data between first user equipment  12  and second user equipment  14  using high-bandwidth communications links  36  and/or  34 . For example, SMS messages may be conveyed between carrier core network  16  and first user equipment  12  via data path  38  and high-bandwidth communications link  36 . As another example, SMS-over-IP SIP messages may be conveyed between first user equipment  12  and carrier ePDG  24  via data path  40 , wireless access point  20 , and high-bandwidth communications link  34  (e.g., over an IPSec tunnel from carrier ePDG  24  to first user equipment  12  through wireless access point  20 ). SMS message data received at first user equipment  12  may be provided to software applications running on first user equipment  12  (e.g., for displaying to a user using a display on the first user equipment). SMS message data transmitted by first user equipment  12  may be provided by software applications running on user equipment  12  and/or one or more user input devices on the first user equipment. 
     When high-bandwidth communications links  36  and  34  are no longer available to first user equipment  12 , processing may proceed to step  74  as shown by arrow  72 . High-bandwidth communications links  36  and  34  may become unavailable when first user equipment  12  has moved out of range of wireless access point  20  and cellular base station  22  (e.g., when first user equipment  12  has moved out of range of any wireless access points or cellular base stations), when first user equipment  12  no longer has access to cellular base station  22  and wireless access point  20  (e.g., because cellular base station  22  and wireless access point  20  are operated by a network carrier that does not provide first user equipment  12  with access to cellular base station  22  and wireless access point  20 ), when cellular base station  22  and wireless access point  20  are disabled, inoperable, or powered down, etc. 
     If desired, first user equipment  12  may monitor the status of high-bandwidth communications links  34  and  36  and may identify when high-bandwidth communications links  34  and  36  have become unavailable. For example, first user equipment  12  may monitor the link quality of high-bandwidth communications links  34  and  36  (e.g., using received signal strength measurements, received signal strength indicator measurements, error rate measurements, signal-to-noise ratio measurements, etc.), may determine when data is no longer being received over high-bandwidth communications links  36  and  34 , may process satellite navigation data or other sensor data to identify when first user equipment  12  is no longer in range of cellular base station  22  and wireless access point  20 , may identify messages received from cellular base station  22 , wireless access point  20 , or elsewhere indicating that high-bandwidth communications links  34  and  36  are no longer available, and/or may perform any other desired operations to determine when high-bandwidth communications links  34  and  36  have become unavailable. Cellular base station  22 , wireless access point  20 , and/or any other desired components in communications network  10  may perform one or more of these operations to determine when high-bandwidth links  34  and  36  have become unavailable if desired. 
     At step  74  (e.g., in response to identifying, at first user equipment  12 , that high-bandwidth communications links  36  and  34  are unavailable), communications network  10  may establish and authenticate a logical network path between first user equipment  12  and carrier ePDG  24  through low-bandwidth communications link  50 , proxy server  30 , and data path  52 . The example of  FIG.  3    is merely illustrative and, in another suitable arrangement, step  74  may be performed while one or more of the high-bandwidth communications links are still being used to convey SMS message data (e.g., step  74  may be performed concurrently with step  70 ). 
     In establishing and authenticating the logical network path, communications network  10  may establish one or more secure network tunnels between carrier ePDG  24  and first user equipment  12 . For example, first user equipment  12  and proxy server  30  may establish a first secure network tunnel such as an interworking wireless local area network (iWLAN) tunnel between first user equipment  12  and proxy server  30 . SMS message data may be conveyed over the first network tunnel by encapsulating the SMS message data using a compression algorithm or envelope associated with low-bandwidth communications link  50  prior to conveying the SMS message data over the low-bandwidth communications link. This encapsulation may be reversed using a decompression (de-encapsulation) algorithm after the SMS message data has been conveyed over the low-bandwidth communications link and the first secure network tunnel (e.g., at proxy server  30  or first user equipment  12 ). First user equipment  12  and proxy server  30  may convey data over communications link  50  without using a network tunnel if desired. Communications network  10  may also establish a second secure network tunnel (e.g., an IPSec tunnel) between proxy server  30  and carrier ePDG  24 . The established and authenticated logical network path may include the underlying low-bandwidth communications link  50 , proxy server  30 , and data path  52 . However, proxy server  30  may appear indistinguishable from first user equipment  12  to carrier ePDG  24  (e.g., proxy server  30  may serve as a proxy for first user equipment  12  from the perspective of carrier ePDG  24 ). 
     At step  76 , communications network  10  may convey SMS message data between first user equipment  12  and second user equipment  14  using low-bandwidth communications link  50 , proxy server  30 , data path  52 , and carrier ePDG  24 . For example, first user equipment  12  may transmit SMS message data in a low-bandwidth format (e.g., as a compressed message) to proxy server  30  over low-bandwidth communications link  50 . Proxy server  30  may convert the SMS message data from the low-bandwidth format into a high-bandwidth format associated with carrier ePDG  24  (e.g., proxy server  30  may convert the compressed message into an SMS-over-IP SIP message). Proxy server  30  may transmit the SMS message data in the high-bandwidth format (e.g., as an SMS-over-IP SIP message) to carrier ePDG  24  over data path  52  (e.g., via the IPSec tunnel between proxy server  30  and carrier ePDG  24 ). Carrier ePDG  24  may transmit the SMS message data to second user equipment  14  via carrier core network  16 , SMS controller  18 , and network portion  32 . This process may be reversed to receive SMS message data from second user equipment  14  at first user equipment  12 . 
     Carrier ePDG  24  may be unable to distinguish between the IPSec tunnel between carrier ePDG  24  and proxy server  30  and an IPSec tunnel between carrier ePDG  24  and first user equipment  12  through wireless access point  20  (e.g., as used to convey SMS-over-IP SIP messages while processing step  70 ). Similarly, carrier ePDG  24  may be unable to distinguish between the SMS-over-IP SIP messages received from wireless access point  20  and the SMS-over-IP SIP messages received from proxy server  30  (e.g., because the SMS-over-IP SIP messages received at carrier ePDG  24  are the same regardless of whether the messages were conveyed over data path  40  and high-bandwidth communications link  34  or whether the messages were conveyed over data path  52  and low-bandwidth communications link  50  via proxy server  30 ). Proxy server  30  may therefore appear to carrier ePDG  24  and the rest of communications network  10  above dashed line  41  of  FIG.  1    as indistinguishable from first user equipment  12 . SMS message data conveyed to first user equipment  12  from second user equipment  14  may terminate at proxy server  30  (e.g., as if proxy server  30  were in fact the first user equipment  12 ). Proxy server  30  may then forward the SMS message data to first user equipment  12  (e.g., as a compressed message) over low-bandwidth communications link  50 . 
     In this way, first user equipment  12  and second user equipment  14  may continue to convey SMS message data even when high-bandwidth communications links  34  and  36  are unavailable. Once high-bandwidth communications link  34  and/or high-bandwidth communications link  36  have become available again, processing may loop back to step  70 , as shown by arrow  78 . Communications network  10  may then continue conveying SMS message data using high-bandwidth communications links  34  and  36  until the high-bandwidth communications links are no longer available. 
       FIG.  4    is a flow chart of illustrative steps that may be performed by communications network  10  in establishing and authenticating a logical network path between first user equipment  12  and carrier ePDG  24  through an underlying low-bandwidth communications link  50 , proxy server  30 , and data path  52  ( FIG.  1   ). Some or all of the steps of  FIG.  4    may, for example, be performed while processing step  74  of  FIG.  3   . 
     At step  80  of  FIG.  4   , proxy server  30  may receive carrier configuration file information (e.g., one or more carrier configuration files) from carrier configuration file server  28  over data path  48 . Carrier configuration file server  28  may store the latest carrier configuration file for each network carrier associated with communication network  10 . The carrier configuration file information may identify the domain and network address of one or more carrier ePDGs such as carrier ePDG  24 . Carrier configuration file server  28  may periodically update the carrier configuration file information over time. Step  80  may be performed concurrently with or prior to step  70  of  FIG.  3   , if desired. 
     At step  82  of  FIG.  4   , first user equipment  12  may transmit a configuration data message to proxy server  30  over low-bandwidth communications link  50 . The configuration data message may include the international mobile subscriber identity (IMSI) of first user equipment  12  or other network identity information that uniquely identifies first user equipment  12 . The configuration data may also include the network access identifier (NAI) of first user equipment  12 , which identifies the network carrier associated with first user equipment  12 . As an example, the NAI may be of the form “x&lt;IMSI&gt;@nai.epc.mnc&lt;MNC&gt;.mcc&lt;MCC&gt;.3gppnetwork.org,”, “imsi@realm,” or other formats, where “x” represents a version of Extensible Authentication Protocol Authentication and Key Agreement (EAP-AKA) that is used (e.g., “0&lt;IMSI&gt;@nai.epc.mnc&lt;MNC&gt;.mcc&lt;MCC&gt;.3gppnetwork.org” to signal regular EAP-AKA, “6&lt;IMSI&gt;@nai.epc.mnc&lt;MNC&gt;.mcc&lt;MCC&gt;.3gppnetwork.org” to signal EAP-AKA′, “0&lt;IMSI&gt;@nai.epc.mnc&lt;MNC&gt;.mcc&lt;MCC&gt;.3gppnetwork.org” to signal EAP-SIM, etc.). If desired, the configuration data message may include any other desired information (e.g., information identifying the configuration data message as a configuration data message to use in establishing a logical path between first user equipment  12  and carrier ePDG  24 , the domain and network address of carrier ePDG  24 , etc.). 
     Proxy server  30  may subsequently begin a network authentication procedure such as an Internet Key Exchange Version 2 (IKEv2) procedure based on the configuration data message and the carrier configuration file information. For example, at step  84 , proxy server  30  may identify the domain and network address of carrier ePDG  24  based on the configuration data received from first user equipment  12  and the carrier configuration file information received from carrier configuration file server  28 . Proxy server  30  may, for example, identify the carrier ePDG domain and network address in the carrier configuration file server information corresponding to the NAI in the configuration data received from first user equipment  12 . 
     As part of the network authentication procedure, proxy server  30  may begin a key exchange procedure such as an Extensible Authentication Protocol Authentication and Key Agreement (EAP-AKA) key exchange with authentication server  26 . For example, at step  86 , proxy server  30  may transmit an authentication request to carrier ePDG  24  (e.g., using the domain and network address identified while processing step  84 ). Carrier ePDG  24  may pass the authentication request to authentication server  26  via data path  42 , carrier core network  16 , and data path  46 . Authentication server  26  may generate a response to the authentication request and may transmit the response to proxy server  30 . 
     At step  88 , proxy server  30  may receive the response to the authentication request from authentication server  26  via data path  46 , carrier core network  16 , data path  42 , carrier ePDG  24 , and data path  52 . 
     At step  90 , proxy server  30  may transmit the response to the authentication request to first user equipment  12  over low-bandwidth communications link  50 . 
     At step  92 , first user equipment  12  may challenge a subscriber identity module (SIM) at first user equipment  12  using the response to the authentication request received over low-bandwidth communications link  50 . When challenged by the response to the authentication request, the SIM at first user equipment  12  may produce a challenge response. 
     At step  94 , first user equipment  12  may transmit the challenge response to proxy server  30  over low-bandwidth communications link  50 . 
     At step  96 , proxy server  30  may transmit the challenge response to authentication server  26  via data path  52 , carrier ePDG  24 , data path  42 , carrier core network  16 , and data path  46 . The challenge response may appear to authentication server  26  and the rest of communications network  10  above dashed line  41  of  FIG.  1    as if it were generated by a SIM at proxy server  30  (e.g., because proxy server  30  serves as a proxy for first user equipment  12 ). Authentication server  26  may verify the received challenge response and, once the challenge response has been verified, may transmit an acknowledgement of the challenge response to proxy server  30 . 
     At step  98 , proxy server  30  may receive the acknowledgement of the challenge response from authentication server  26  via data path  46 , carrier core network  16 , data path  42 , carrier ePDG  24 , and data path  52 . Once proxy server  30  has received the acknowledgment, a secure and authentic network tunnel such as an IPSec tunnel is established between proxy server  30  and carrier ePDG  24 . 
     At step  100 , communications network  10  may perform IMS registration operations for proxy server  30 . For example, proxy server  30  may provide an IMS registration request to authentication server  26  (e.g., via the IPSec tunnel over data path  52 , carrier ePDG  24 , data path  42 , carrier core network  16 , and data path  46 ). Authentication server  26  may respond to the IMS registration request with unique response data transmitted to proxy server  30 . Proxy server  30  may convey the unique response data to first user equipment  12  over low-bandwidth communications link  50 . First user equipment  12  may use the unique response data to challenge the SIM at first user equipment  12 , which generates a challenge response. First user equipment  12  may transmit the challenge response to proxy server  30  over low-bandwidth communications link  50 . Proxy server  30  may transmit the challenge response to authentication server  26  (e.g., via the IPSec tunnel over data path  52 , carrier ePDG  24 , data path  42 , carrier core network  16 , and data path  46 ). Authentication server  26  may verify the challenge response and, once the challenge response has been verified, may transmit a corresponding acknowledgement to proxy server  30 . At this point, proxy server  30  and thus first user equipment  12  may be IMS-registered. Once IMS registration is complete, a secure and authenticated logical network path is established between first user equipment  12  and carrier ePDG  24  through proxy server  30 . SMS message data may subsequently be conveyed over low-bandwidth communications link  50  and over data path  52  (e.g., via the IPSec tunnel). This example is merely illustrative and, if desired, other authentication procedures may be used to establish and authenticate the logical network path. 
       FIG.  5    is a flow chart of illustrative steps that may be performed by communications network  10  in transmitting SMS message data from first user equipment  12  to second user equipment  14 . The steps of  FIG.  5    may, for example, be performed while processing step  76  of  FIG.  3   . 
     At step  102  of  FIG.  5   , first user equipment  12  may identify SMS message data to transmit to second user equipment  14 . The SMS message data may be a data payload that includes text or other input generated by software applications running on the user equipment or provided by a user via input/output devices on or coupled to the user equipment. In scenarios where high-bandwidth communications link  36  is available, the SMS message data may be included in an SMS message or in an SMS-over-IP SIP message provided to cellular base station  22  over high-bandwidth communications link  36 . Similarly, in scenarios where high-bandwidth communications link  34  is available, the SMS message data may be included in an SMS-over-IP SIP message provided to wireless access point  20  over high-bandwidth communications link  34 . When high-bandwidth communications links  34  and  36  are unavailable, only low-bandwidth communications link  50  is available for first user equipment  12  to transmit the SMS message data. However, low-bandwidth communications link  50  may be unable to support excessively large messages such as SMS-over-IP messages. 
     At step  104 , first user equipment  12  may generate a compressed message that includes the identified SMS message data (e.g., a compressed message in the low-bandwidth format associated with low-bandwidth communications link  50 ). To generate the compressed message, first user equipment  12  (e.g., control circuitry  54  of  FIG.  2   ) may encapsulate the SMS message data using a compression algorithm or envelope associated with low-bandwidth communications link  50 . The compression algorithm may, for example, remove any SMS or IMS headers from the SMS message data (e.g., headers that would otherwise be present when the SMS message data is sent as an SMS-over-IP SIP message via high-bandwidth communications links  34  or  36 ) and/or may perform any other desired compression operations on the SMS message data. Removing the SMS and IMS headers from the SMS message data may significantly reduce the size of the compressed message relative to the size of an SMS-over-IP SIP message. The compressed message may, for example, be less than 5 kB, less than 1 kB, etc. This reduced size may allow the compressed message to be conveyed over low-bandwidth communications link  50 . The compressed message may include Link Layer headers or other relatively small headers (e.g., headers that are smaller in size than SMS or IMS headers), network identity information associated with first user equipment  12  (e.g., the IMSI of first user equipment  12 ), and/or any other desired information that helps to route the SMS message data in the compressed message to a desired destination (e.g., to second user equipment  14 ). 
     At step  106 , first user equipment  12  may transmit the compressed message to proxy server  30  over low-bandwidth communications link  50 . The encapsulation of the SMS message data to form the compressed message may, for example, configure the SMS message data to be conveyed over the first secure network tunnel between first user equipment  12  and proxy server  30  (e.g., via the underlying low-bandwidth communications link  50 ). 
     At step  108 , proxy server  30  may unpack (extract) the SMS message data from the compressed message received over low-bandwidth communications link  50 . For example, proxy server  30  may unpack the SMS message data by performing a decompression algorithm (e.g., de-enveloping or de-encapsulating process) on the compressed message (e.g., the decompression algorithm may reverse the compression algorithm performed by first user equipment  12  because the first secure network tunnel terminates at proxy server  30 ). 
     At step  110 , proxy server  30  may re-pack the unpacked SMS message data into a high-bandwidth format associated with data path  52 . For example, proxy server  30  may re-pack (e.g., encapsulate) the SMS message data as an SMS-over-IP SIP message. The SMS-over-IP SIP message may include SMS and IMS headers (e.g., headers that were removed at first user equipment  12  while processing step  104 ), where the SMS message data forms the data payload for the SMS-over-IP SIP message. 
     At step  112 , proxy server  30  may transmit the SMS-over-IP SIP message to carrier ePDG  24  via data path  52  (e.g., over the IPSec tunnel between proxy server  30  and carrier ePDG  24 ). The SMS-over-IP SIP message generated by proxy server  30  may be indistinguishable to carrier ePDG  24  from an SMS-over-IP SIP message conveyed to carrier ePDG  24  via wireless access point  20  and high-bandwidth communications link  34 . While the source address header fields of the SMS-over-IP SIP message may identify proxy server  30  as the source of the SMS-over-IP SIP message rather than first user equipment  12 ), carrier ePDG  24  may have no way of knowing that proxy server  30  is a network entity that is different from first user equipment  12  (e.g., proxy server  30  serves as a proxy for first user equipment  12  and, from the perspective of carrier ePDG  24 , is indistinguishable from first user equipment  12 ). 
     At step  114 , carrier ePDG  24  may transmit the SMS message data (e.g., the SMS-over-IP SIP message) received from proxy server  30  to carrier core network  16  over data path  42 . Carrier core network  16  may transmit the SMS message data to SMS controller  18  over data path  44 . SMS controller  18  may transmit the SMS message data to second user equipment  14  via network portion  32 . 
       FIG.  6    is a flow chart of illustrative steps that may be performed by communications network  10  in transmitting SMS message data from second user equipment  14  to first user equipment  12 . The steps of  FIG.  6    may, for example, be performed while processing step  76  of  FIG.  3   . Second user equipment  14  may transmit SMS message data (e.g., in an SMS message or an SMS-over-IP SIP message) that is forwarded to carrier core network  16  by SMS controller  18 . Carrier core network  16  may pass the SMS message data to carrier ePDG  24  over data path  42 . Carrier ePDG  24  may transmit an SMS-over-IP SIP message that includes the SMS message data to proxy server  30  over data path  52  (e.g., over the IPSec tunnel associated with data path  52 ). 
     At step  116  of  FIG.  6   , proxy server  30  may receive the SMS-over-IP SIP message from carrier ePDG  24 . From the perspective of carrier ePDG  24 , proxy server  30  is the destination for the SMS message data in the SMS-over-IP SIP message. However, proxy server  30  is aware of low-bandwidth communications link  50  and that first user equipment  12  is the final destination for the SMS message data in the SMS-over-IP SIP message. 
     At step  118 , proxy server  30  may unpack the SMS message data from the SMS-over-IP SIP message received from carrier ePDG  24 . 
     At step  120 , proxy server  30  may re-pack the SMS message data to generate a compressed message. For example, proxy server  30  may generate the compressed message by encapsulating the SMS message data using the compression algorithm or envelope associated with low-bandwidth communications link  50  (e.g., using the same compression algorithm used by first user equipment  12  while processing step  104  of  FIG.  5   ). 
     At step  122 , proxy server  30  may transmit the compressed message to first user equipment  12  over low-bandwidth communications link  50 . 
     At step  124 , first user equipment  12  may unpack the SMS message data from the compressed message received from proxy server  30  over low-bandwidth communications link  50 . For example, first user equipment  12  may unpack the SMS message data by performing the decompression algorithm (e.g., de-enveloping or de-encapsulating process) associated with low-bandwidth communications link  50  on the compressed message (e.g., the same decompression algorithm used by proxy server  30  in processing step  108  of  FIG.  5   ). The unpacked SMS message data may be provided to software applications running on first user equipment  12  (e.g., for display to a user of first user equipment  12 ). 
     The steps of  FIGS.  5  and  6    may be processed to exchange SMS messages in both directions between first user equipment  12  and second user equipment  14  when high-bandwidth communications links  34  and  36  are unavailable. In another suitable arrangement, second user equipment  14  may broadcast SMS message data to first user equipment  12  and/or other user equipment in communications network  10  (e.g., without first user equipment  12  transmitting SMS message data back to second user equipment  14 ). Rather than being addressed to an individual proxy server  30 , SMS-over-IP SIP messages that include SMS message data broadcasted by second user equipment  14  may be provided to multiple user equipment network addresses by carrier ePDG  24  (e.g., different network addresses known by the network carrier associated with carrier core network  16  and carrier ePDG  24  to be located within or associated with a particular geographic region or area). In scenarios where high-bandwidth communications links  34  and  36  are unavailable, this broadcasted SMS message data (e.g., the SMS-over-IP SIP messages that include the broadcasted SMS message data) may be addressed to proxy server  30  (e.g., because proxy server  30  represents first user equipment  12  from the perspective of carrier ePDG  24 ). Proxy server  30  may forward the broadcasted SMS message data to first user equipment  12  over low-bandwidth communications link  50 . 
       FIG.  7    is a flow diagram showing how first user equipment  12  may transmit SMS message data over communications network  10  when high-bandwidth communications link  34  is available and when high-bandwidth communications link  34  is unavailable. As shown in  FIG.  7   , when high-bandwidth communications link  34  is available, first user equipment  12  may transmit SMS-over-IP SIP message  126  to wireless access point  20  over high-bandwidth communications link  34 , as shown by arrow  128 . Wireless access point  20  may route SMS-over-IP SIP message  126  to carrier ePDG  24  over data path  40 , as shown by arrow  130 . Communications network  10  may, for example, transmit SMS-over-IP SIP message  126  over a secure network tunnel such as IPSec tunnel  129  that extends from first user equipment  12  to carrier ePDG  24  through wireless access point  20  (e.g., an IPSec tunnel that runs through wireless access point  20  but that terminates at first user equipment  12  and carrier ePDG  24 ). Carrier ePDG  24  may transmit SMS-over-IP SIP message  126  to carrier core network  16  over data path  42 , as shown by arrow  132 . Carrier ePDG  24  may transmit the SMS message data from SMS-over-IP SIP message  126  to carrier core network  16  in other formats if desired. The communications network may subsequently transmit the SMS message data to the second user equipment via SMS controller  18  of  FIG.  1   . 
     When high-bandwidth communications link  34  is unavailable, first user equipment  12  may generate compressed message (CM)  134  by encapsulating (compressing) the SMS message data that would otherwise have been transmitted in SMS-over-IP SIP message  126  (e.g., while processing step  104  of  FIG.  5   ). First user equipment  12  may transmit compressed message  134  to proxy server  30  over low-bandwidth communications link  50 , as shown by arrow  136  (e.g., while processing step  106  of  FIG.  5   ). Compressed message  134  may, for example, be transmitted over a secure network tunnel  137  extending from first user equipment  12  to proxy server  30 . While low-bandwidth communications link  50  may not have sufficient bandwidth to support transmission of SMS-over-IP SIP messages, low-bandwidth communications link  50  may be capable of transmitting compressed message  134 , which is much smaller than SMS-over-IP SIP message  126 . 
     Proxy server  30  may unpack the SMS message data from compressed message  134  and may re-pack (encapsulate) the SMS message data as SMS-over-IP SIP message  140  (e.g., while processing steps  108  and  110  of  FIG.  5   ). Proxy server  30  may transmit SMS-over-IP SIP message  140  to carrier ePDG  24  over data path  52 , as shown by arrow  138  (e.g., while processing step  112  of  FIG.  5   ). SMS-over-IP SIP message  140  may, for example, be transmitted over a secure network tunnel such as IPSec tunnel  139  extending from proxy server  30  to carrier ePDG  24  (e.g., an IPSec tunnel that terminates at proxy server  30  and carrier ePDG  24 ). SMS-over-IP SIP message  140  may be indistinguishable from SMS-over-IP SIP message  126  to carrier ePDG  24  (e.g., carrier ePDG  24  may be unable to distinguish between IPSec tunnel  129  and IPSec tunnel  139 ). Carrier ePDG  24  may transmit SMS-over-IP SIP message  140  to carrier core network  16  over data path  42 , as shown by arrow  142 . Carrier ePDG  24  may transmit the SMS message data from SMS-over-IP SIP message  140  to carrier core network  16  in other formats if desired. The communications network may subsequently transmit the SMS message data to the second user equipment via SMS controller  18  of  FIG.  1   . 
       FIG.  8    is a flow diagram showing how first user equipment  12  may receive SMS message data over communications network  10  when high-bandwidth communications link  34  is available and when high-bandwidth communications link  34  is unavailable. As shown in  FIG.  8   , when high-bandwidth communications link  34  is available, carrier ePDG  24  may receive SMS-over-IP SIP message  154  from carrier core network  16  over data path  42 , as shown by arrow  156 . Carrier ePDG  24  may transmit SMS-over-IP SIP message  154  to first user equipment  12  over IPSec tunnel  129  (e.g., SMS-over-IP SIP message  154  may be conveyed to wireless access point  20  over data path  40 , as shown by arrow  158 , and may be conveyed to first user equipment  12  over high-bandwidth communications link  34 , as shown by arrow  160 ). 
     When high-bandwidth communications link  34  is unavailable, carrier ePDG  24  may receive SMS-over-IP SIP message  144  from carrier core network  16  over data path  42 , as shown by arrow  146 . Carrier ePDG  24  may transmit SMS-over-IP SIP message  144  to proxy server  30  over data path  52 , as shown by arrow  148  (e.g., over IPSec tunnel  139 ). Because carrier ePDG  24  is unable to distinguish between IPSec tunnel  129  and IPSec tunnel  139 , SMS-over-IP SIP message  144  may be transmitted to proxy server  30  even though high-bandwidth communications link  34  is unavailable. 
     Proxy server  30  may unpack the SMS message data from SMS-over-IP SIP message  144  and may re-pack (encapsulate) the SMS message data to generate compressed message  150  (e.g., while processing steps  118  and  120  of  FIG.  6   ). Proxy server  30  may transmit compressed message  150  to first user equipment  12  over low-bandwidth communications link  50 , as shown by arrow  152  (e.g., while processing step  122  of  FIG.  6   ). First user equipment  12  may subsequently unpack (de-encapsulate) compressed message  150  to retrieve the SMS message data from SMS-over-IP SIP message  144  (e.g., while processing step  124  of  FIG.  6   ). While low-bandwidth communications link  50  may have insufficient bandwidth to support transmission of SMS-over-IP SIP messages, low-bandwidth communications link  50  may be capable of transmitting compressed message  150 , which is much smaller than SMS-over-IP SIP message  154 . In this way, first user equipment  12  may continue to transmit and receive SMS message data even when high-bandwidth communications links become unavailable. Because carrier ePDG  24  is unable to distinguish between SMS-over-IP messages from proxy server  30  and SMS-over-IP messages from first user equipment  12 , communications may transition from the high-bandwidth communications links to the low-bandwidth communications links without requiring expensive and time-consuming modifications to carrier ePDG  24 , carrier core network  16 , or other portions of communications network  10 . 
     In practice, first user equipment  12  may rapidly and unpredictably switch between the high-speed communications link (e.g., high-bandwidth communications link  34 ) and the low-speed communications link (e.g., low-bandwidth communications link  34 ) such that the same message is received multiple times over different protocols and/or communications links (e.g., over links  34  and  50 ), potentially over long periods of time. This may occur, for example, in scenarios where both the high-speed communications link (e.g., high-bandwidth communications link  34 ) and the low-speed communications link (e.g., low-bandwidth communications link  50 ) are concurrently available and/or in scenarios where proxy server  30  and/or carrier ePDG  24  queue messages for first user equipment  12  such as when first user equipment  12  has no connectivity. Consider an example in which first user equipment  12  receives a message over low-bandwidth communications link  50  but the link is severed before first user equipment  12  sends an acknowledgement (ACK) message back to proxy server  30 . Then, when high-bandwidth communications link  34  is back in service (e.g., hours later), first user equipment  12  may receive the same message over link  34  and may send an ACK message to carrier ePDG  24  in response. In these scenarios, first user equipment  12  may perform de-duplication operations to handle the receipt and acknowledgement of these duplicate messages at first user equipment  12 . 
     If desired, proxy server  30  may control other devices to send and receive SMS messages (e.g., SMS-over-IP messages) on behalf of first user equipment  12 . For example, proxy server  30  may communicate with one or more additional devices (e.g., a tablet computer, laptop computer, speaker device, desktop computer, cellular telephone, etc.) to control the device(s) to send and/or receive SMS messages on behalf of first user equipment  12  while first user equipment  12  is communicatively coupled to proxy server  30  (e.g., via low-bandwidth communications link  50  or any Internet link). Proxy server  30  may be communicatively coupled to the additional device(s) via any desired wired and/or wireless links. Proxy server  30  may transmit message data from first user equipment  12  to the additional device(s) for transmission to second user equipment  14  and may relay message data received by the additional device(s) to first user equipment  12 . This operation may be performed even when first user equipment  12  is not constantly connected to proxy server  30  (e.g., authentication may be performed once and then on some regular period thereafter). 
     The methods and operations described above in connection with  FIGS.  1 - 8    may be performed by the components of communications network  10  using software, firmware, and/or hardware (e.g., dedicated circuitry or hardware). Software code for performing these operations may be stored on non-transitory computer readable storage media (e.g., tangible computer readable storage media) stored on one or more of the components of communications network  10  or elsewhere (e.g., storage  58  of  FIG.  2   ). The software code may sometimes be referred to as software, data, instructions, program instructions, or code. The non-transitory computer readable storage media may include drives, non-volatile memory such as non-volatile random-access memory (NVRAM), removable flash drives or other removable media, other types of random-access memory, etc. Software stored on the non-transitory computer readable storage media may be executed by processing circuitry on one or more of the components of communications network  10  (e.g., processing circuitry  56  of  FIG.  2   ). The processing circuitry may include microprocessors, central processing units (CPUs), application-specific integrated circuits with processing circuitry, or other processing circuitry. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20220930
Publication Date: 20240130
Grant Date: 20240130
Priority Date: 20190708
Inventors: MBONYE, GAHIMA S.
ELLIS, Daniel P.
NELSON, GREGORY R.
VASHI, Prashant H.
SITNIKOV, SERGEY
YERRABOMMANAHALLI, Vikram B.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W80/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W4/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W36/0027", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W88/182", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W4/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W80/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W28/065", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W76/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L69/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L67/5651", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W36/0027", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W88/182", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 71130838