WO2016160053A1

WO2016160053A1 - Epdg identification techniques for routing ims emergency calls

Info

Publication number: WO2016160053A1
Application number: PCT/US2015/052518
Authority: WO
Inventors: Anna Lucia PINHEIRO; Alexandre S. STOJANOVSKI; Muthaiah Venkatachalam
Original assignee: Intel IP Corporation
Priority date: 2015-03-31
Filing date: 2015-09-26
Publication date: 2016-10-06

Abstract

ePDG identification techniques for routing IMS emergency calls are described. In one embodiment, for example, an apparatus may comprise at least one memory and logic, at least a portion of which is implemented in circuitry coupled to the at least one memory, the logic to detect an initiation of an emergency call at a roaming user equipment (UE) possessing 5 wireless connectivity with a wireless local area network (WLAN), send, via the WLAN, a first message comprising one or more location indication parameters, and receive a second message comprising one or more public land mobile network (PLMN) identifiers (IDs) in response to the first message. Other embodiments are described and claimed.

Description

EPDG IDENTIFICATION TECHNIQUES FOR ROUTING IMS EMERGENCY CALLS

RELATED CASE

This application claims priority to United States Provisional Patent Application Number 62/141,060, filed March 31, 2015, the entirety of which is hereby incorporated by reference.

TECHNICAL FIELD

Embodiments herein generally relate to communications between devices in broadband wireless communications networks.

BACKGROUND

In a 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) public land mobile network (PLMN), an internet protocol multimedia subsystem (IMS) may provide support for the placement of internet protocol (IP) packet-switched voice calls via an evolved packet core (EPC). User equipment (UE) may establish IP access to the EPC via a 3GPP access network, such as an evolved Universal Mobile Telecommunications System Radio Access Network (E- UTRAN), or through a non-3 GPP access network, such as a wireless local area network

(WLAN). In the event that a UE accesses the EPC via a non-3GPP access network, the UE's access may be classified as either trusted or untrusted, according to a policy of the PLMN operator. A UE that establishes untrusted non-3GPP IP access may communicate with the EPC via an evolved packed data gateway (ePDG).

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an embodiment of a first operating environment.

FIG. 2 illustrates an embodiment of a second operating environment.

FIG. 3 illustrates an embodiment of a third operating environment.

FIG. 4 illustrates an embodiment of a fourth operating environment.

FIG. 5 illustrates an embodiment of a fifth operating environment.

FIG. 6 illustrates an embodiment of a sixth operating environment.

FIG. 7 illustrates an embodiment of a seventh operating environment.

FIG. 8 illustrates an embodiment of a first logic flow.

FIG. 9 illustrates an embodiment of a second logic flow.

FIG. 10 illustrates an embodiment of a third logic flow.

FIG. 11A illustrates an embodiment of a first storage medium.

FIG. 11B illustrates an embodiment of a second storage medium.

FIG. 12 illustrates an embodiment of user equipment. FIG. 13 illustrates an embodiment of a device.

FIG. 14 illustrates an embodiment of a wireless network.

DETAILED DESCRIPTION

Various embodiments may be generally directed to ePDG identification techniques for routing IMS emergency calls. In one embodiment, for example, an apparatus may comprise at least one memory and logic, at least a portion of which is implemented in circuitry coupled to the at least one memory, the logic to detect an initiation of an emergency call at a roaming user equipment (UE) possessing wireless connectivity with a wireless local area network (WLAN), send, via the WLAN, a first message comprising one or more location indication parameters, and receive a second message comprising one or more public land mobile network (PLMN) identifiers (IDs) in response to the first message. Other embodiments are described and claimed.

Various embodiments may comprise one or more elements. An element may comprise any structure arranged to perform certain operations. Each element may be implemented as hardware, software, or any combination thereof, as desired for a given set of design parameters or performance constraints. Although an embodiment may be described with a limited number of elements in a certain topology by way of example, the embodiment may include more or less elements in alternate topologies as desired for a given implementation. It is worthy to note that any reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrases "in one embodiment," "in some

embodiments," and "in various embodiments" in various places in the specification are not necessarily all referring to the same embodiment.

The techniques disclosed herein may involve transmission of data over one or more wireless connections using one or more wireless mobile broadband technologies. For example, various embodiments may involve transmissions over one or more wireless connections according to one or more 3rd Generation Partnership Project (3GPP), 3GPP Long Term

Evolution (LTE), and/or 3 GPP LTE- Advanced (LTE-A) technologies and/or standards, including their revisions, progeny and variants. Various embodiments may additionally or alternatively involve transmissions according to one or more Global System for Mobile

Communications (GSM)/Enhanced Data Rates for GSM Evolution (EDGE), Universal Mobile Telecommunications System (UMTS)/High Speed Packet Access (HSPA), and/or GSM with General Packet Radio Service (GPRS) system (GSM/GPRS) technologies and/or standards, including their revisions, progeny and variants. Examples of wireless mobile broadband technologies and/or standards may also include, without limitation, any of the Institute of Electrical and Electronics Engineers (IEEE) 802.16 wireless broadband standards such as IEEE 802.16m and/or 802.16p, International Mobile Telecommunications Advanced (IMT-ADV), Worldwide Interoperability for Microwave Access (WiMAX) and/or WiMAX II, Code Division Multiple Access (CDMA) 2000 (e.g., CDMA2000 lxRTT, CDMA2000 EV-DO, CDMA EV-DV, and so forth), High Performance Radio

Metropolitan Area Network (HIPERMAN), Wireless Broadband (WiBro), High Speed

Downlink Packet Access (HSDPA), High Speed Orthogonal Frequency-Division Multiplexing (OFDM) Packet Access (HSOPA), High-Speed Uplink Packet Access (HSUPA) technologies and/or standards, including their revisions, progeny and variants.

Some embodiments may additionally or alternatively involve wireless communications according to other wireless communications technologies and/or standards. Examples of other wireless communications technologies and/or standards that may be used in various

embodiments may include, without limitation, other IEEE wireless communication standards such as the IEEE 802.11, IEEE 802.11a, IEEE 802.11b, IEEE 802.1 lg, IEEE 802.11η, IEEE 802. l lu, IEEE 802.1 lac, IEEE 802.11 ad, IEEE 802.11af, and/or IEEE 802.11 ah standards, High-Efficiency Wi-Fi standards developed by the IEEE 802.11 High Efficiency WLAN (HEW) Study Group, Wi-Fi Alliance (WFA) wireless communication standards such as Wi-Fi, Wi-Fi Direct, Wi-Fi Direct Services, Wireless Gigabit (WiGig), WiGig Display Extension (WDE), WiGig Bus Extension (WBE), WiGig Serial Extension (WSE) standards and/or standards developed by the WFA Neighbor Awareness Networking (NAN) Task Group, machine-type communications (MTC) standards such as those embodied in 3GPP Technical Report (TR) 23.887, 3 GPP Technical Specification (TS) 22.368, and/or 3 GPP TS 23.682, and/or near-field communication (NFC) standards such as standards developed by the NFC Forum, including any revisions, progeny, and/or variants of any of the above. The embodiments are not limited to these examples.

In addition to transmission over one or more wireless connections, the techniques disclosed herein may involve transmission of content over one or more wired connections through one or more wired communications media. Examples of wired communications media may include a wire, cable, metal leads, printed circuit board (PCB), backplane, switch fabric, semiconductor material, twisted-pair wire, co-axial cable, fiber optics, and so forth. The embodiments are not limited in this context.

FIG. 1 illustrates an example of an operating environment 100 that may be representative of various embodiments. In operating environment 100, user equipment (UE) 102 may join a wireless local area network (WLAN) 103 by associating with an access point (AP) 104. In some embodiments, joining WLAN 103 may enable UE 102 to engage in internet protocol (IP)-based communications with one or more remote devices in one or more packet data networks. In various embodiments, joining WLAN 103 may enable UE 102 to establish untrusted non-3GPP IP access 106 to elements of an evolved packet core (EPC). In some embodiments, UE 102 may send data to a given remote device in the form of one or more IP packets that it directs to an IP address 112 associated with that remote device. In various embodiments, UE 102 may identify a fully-qualified domain name (FQDN) 108 associated with such a remote device. In some embodiments, UE 102 may send a query message (not pictured) comprising FQDN 108 to a local domain name system (DNS) server 110 via AP 104 in order to request that the DNS server 110 inform UE 102 of the IP address that corresponds to FQDN 108. In various embodiments, DNS server 110 may identify IP address 112 as the IP address that corresponds to FQDN 108 and may send a query response message (not pictured) comprising IP address 112 to UE 102 via AP 104 in order to inform UE 102 that IP address 112 corresponds to FQDN 108. The embodiments are not limited in this context.

In some embodiments, it may be desirable that UE 102 establish untrusted non-3GPP IP access 106 to the EPC so that an emergency call initiated at UE 102 may be routed to the EPC. In various embodiments, such an emergency call may be initiated at UE 102 as a Voice over WLAN (VoWLAN) call. In some embodiments, AP 102 may use untrusted non-3GPP IP access 106 to route the emergency call to an EPC node for further handling. In various embodiments, within the EPC, the emergency call may then be placed as an IP multimedia subsystem (IMS) emergency call. The embodiments are not limited in this context.

FIG. 2 illustrates an example of an operating environment 200 that may be representative of some embodiments in which it may be possible for UE 102 to place an emergency call that is routed to an EPC node via untrusted non-3GPP IP access 106. More particularly, operating environment 200 may be representative of various embodiments in which an emergency call initiated at UE 102 may be routed to a visited PLMN 213 for placement by an internet protocol multimedia subsystem (IMS) of the visited PLMN 213. In some embodiments, visited PLMN 213 may comprise a PLMN within (or near) which UE 102 is roaming. The embodiments are not limited in this context.

In various embodiments, in order to enable its emergency call to be routed to visited

PLMN 213, UE 102 may need to establish a secure tunnel 215 to a visited ePDG 214 comprised in the visited PLMN 213. In some embodiments, secure tunnel 215 may comprise an internet protocol security (IPsec) tunnel. In various embodiments, a tunnel establishment procedure for establishing secure tunnel 215 may involve an exchange of one or more request and response messages between UE 102 and visited ePDG 214. For example, in some embodiments, secure tunnel 215 may be established according to an Internet Key Exchange Protocol Version 2 (IKEv2) tunnel establishment procedure involving a series of exchanges of Internet Key Exchange Protocol Version 2 (IKEv2) request messages, such as IKE_AUTH request messages, and IKEv2 response messages, such as IKE_AUTH response messages. The embodiments are not limited to this example.

In various embodiments, in conjunction with the establishment of secure tunnel 215, UE 102 may provide an indication that it requires packet data network (PDN) connectivity in order to place an emergency call. In some embodiments, in response to this indication, visited ePDG 214 may identify a visited IMS emergency call (IEC) PDN gateway (PGW) 220 that comprises a PGW within visited PLMN 213 that is designated for support of IMS emergency calls. In various embodiments, visited ePDG 214 may identify visited IEC PGW 220 based on an emergency access point name (Em-APN) that is usable within visited PLMN 213 to derive the identity of the PGW that has been selected for IMS emergency call support within visited PLMN 213. In some embodiments, the Em-APN may be a PLMN-specific parameter, such that it is only valid within visited PLMN 213. In various embodiments, once it has identified visited IEC PGW 220, visited ePDG 214 may establish IP connectivity between UE 102 and a visited IMS core 222 of visited PLMN 213 via visited IEC PGW 220. In some embodiments, visited IMS core 222 may generally comprise one or more network nodes that implement IMS operations, functions, and/or communications for visited PLMN 213. The embodiments are not limited in this context.

In various embodiments, once it possesses IP connectivity with visited IMS core 222, UE 102 may direct an emergency call to the IMS of visited PLMN 213. In some embodiments, UE 102 may direct the emergency call to the IMS of visited PLMN 213 by sending a session initiation protocol (SIP) request message to visited IMS core 222. In various embodiments, the SIP request message may comprise an SIP INVITE message. In some embodiments, the SIP request message may contain an emergency call indicator to indicate that the SIP request corresponds to an emergency call. In various embodiments, the SIP request message may contain location information comprising information generally descriptive of a location of UE 102. In some embodiments, visited IMS core 222 may route the SIP request message to a visited public safety answering point (PSAP) 224 that comprises a PSAP of visited PLMN 213. In various embodiments, visited PSAP 224 may generally comprise a call center designated for answering emergency calls and dispatching emergency services in response to such calls. In some embodiments, the emergency services/personnel that visited PSAP 224 may dispatch may generally comprise emergency services/personnel - such as police, firefighters, and emergency medical services (EMS) personnel - that are located in relatively close proximity to visited PSAP 224. In various embodiments, visited PLMN 213 may comprise multiple PSAPs, and visited IMS core 222 may select visited PSAP 224 from among those multiple PSAPs. In some such embodiments, visited IMS core 222 may estimate an approximate location of UE 102 based on location information comprised in the SIP request message and select visited PSAP 224 based on a determination that the estimated approximate location of UE 102 is relatively close to the location of visited PSAP 224. The embodiments are not limited in this context.

In various embodiments, in order to exchange communications with visited ePDG 214 and establish secure tunnel 215, UE 102 may first need to identify an internet protocol (IP) address of visited ePDG 214. In some embodiments, UE 102 may be obtain a visited ePDG IP address 218 comprising an IP address of visited ePDG 214 by querying DNS server 110. More particularly, in various embodiments, UE 102 may obtain visited ePDG IP address 218 by sending a query message (not pictured) comprising a visited ePDG FQDN 216 to DNS server 110 via AP 104, where visited ePDG FQDN 216 is an FQDN for the ePDG(s) of visited PLMN 213. In some embodiments, DNS server 110 may identify visited ePDG IP address 218 as an IP address associated with visited ePDG FQDN 216, and may send a query response message (not pictured) comprising visited ePDG IP address 218 to UE 102 via AP 104. In various embodiments, visited ePDG 214 may comprise a sole ePDG of visited PLMN 213, and thus its visited ePDG IP address 218 may be the only ePDG IP address returned in the query response message. In some other embodiments, visited ePDG 214 may comprise one of multiple ePDGs of visited PLMN 213. In various such embodiments, visited ePDG IP address 218 may comprise one of multiple ePDG IP addresses returned in the query response message. The embodiments are not limited in this context.

In some embodiments, the visited ePDG FQDN 216 for visited PLMN 213 may conform to a naming convention according to which the ePDG FQDN of any given PLMN is defined as a function of the PLMN ID of that PLMN. For example, in various embodiments, visited ePDG FQDN 216 may conform to a naming convention according to which the ePDG FQDN of any given PLMN is defined to be "epdg.epc.mnc<MNC>.mcc<MCC>.pub.3gppnetwork.org", where <MNC> represents a Mobile Network Code (MNC) associated with the PLMN, <MCC> represents a Mobile Country Code (MCC) associated with the PLMN, and the PLMN ID of the PLMN is defined to be a concatenation of its MCC and its MNC. In some embodiments, based on such a naming convention, UE 102 may determine visited ePDG FQDN 216 based on a PLMN ID of visited PLMN 213. In various embodiments, UE 102 may be able to determine the PLMN ID of visited PLMN 213 by, for example, registering with visited PLMN 213 or reading a broadcast channel of a nearby 3 GPP cell and obtaining the PLMN ID from system information broadcast over that channel. The embodiments are not limited to these examples. FIG. 3 illustrates an example of an operating environment 300 that may be representative of some embodiments. More particularly, operating environment 300 may be representative of various embodiments in which UE 102 is not aware of the PLMN ID of visited PLMN 213. This may occur, for example, if UE 102 is not within the respective coverage areas of any of the cells of visited PLMN 213. In some embodiments, since it does not know the PLMN ID for visited PLMN 213, UE 102 may construct a home ePDG FQDN 316 based on a PLMN ID for its home PLMN 313. In various embodiments, UE 102 may then send a query message (not pictured) comprising home ePDG FQDN 316 to DNS server 110 via AP 104. In some embodiments, DNS server 110 may identify a home ePDG IP address 318 of a home ePDG 314 in home PLMN 313 as an IP address associated with home ePDG FQDN 316, and may send a query response message (not pictured) comprising home ePDG IP address 318 to UE 102 via AP 104. The embodiments are not limited in this context.

In various embodiments, UE 102 may then proceed in analogous fashion as was previously discussed in reference to operating environment 200 of FIG. 2. For example, in some embodiments, UE 102 may establish a secure tunnel 315 to home ePDG 314, and may provide home ePDG 314 with an indication that UE 102 requires PDN connectivity in order to place an emergency call. In various embodiments, home ePDG 314 may identify a home IEC PGW 320 based on an Em-APN that is valid within home PLMN 313 and establish IP connectivity between UE 102 and a home IMS core 322 of home PLMN 313 via home IEC PGW 320. In some embodiments, once it possesses IP connectivity with home IMS core 322, UE 102 may direct an emergency call to the IMS of home PLMN 313 by sending an SIP request message to home IMS core 322. In various embodiments, home IMS core 322 may route the SIP request message to a home PSAP 324 that comprises a PSAP of home PLMN 313.

In some embodiments, the emergency services that home PSAP 324 may dispatch in response to emergency calls that it handles may generally comprise emergency

services/personnel that are located in relatively close proximity to home PSAP 324. However, in various embodiments, since UE 102 is roaming and is not located within home PLMN 313, the emergency services/personnel that home PSAP 324 is able to dispatch may not be located in relatively close proximity to UE 102. In some embodiments, for example, home PSAP 324 may comprise an emergency call/dispatch center located in a different city than UE 102, a different state, province, or territory than UE 102, a different country than UE 102, and possibly even a different continent than UE 102. Thus, in various embodiments, the emergency

services/personnel that home PSAP 324 is able to dispatch may not be able to reach the location of UE 102 quickly enough, and possibly may not be able to reach the location of UE 102 at all. Disclosed herein are ePDG identification techniques for routing IMS emergency calls that may be implemented in some embodiments in order to address this issue. According to various such techniques, in conjunction with placing an emergency call, a roaming UE that does not know the PLMN ID of any nearby PLMN may send a request message comprising one or more location indication parameters to a remote device via a WLAN and receive a response message comprising one or more PLMN IDs. In some embodiments, the remote device may determine an approximate location of UE 102 based on the one or more location indication parameters, identify one or more PLMNs that are relatively close to the approximate location of UE 102, send a response message comprising the respective PLMN IDs of the one or more PLMNs. In various embodiments, the roaming UE may construct an ePDG FQDN for a local PLMN based on a PLMN ID comprised in the response message, and may use the ePDG FQDN for the local PLMN to identify an IP address of an ePDG of the local PLMN. In some other embodiments, in conjunction with placing an emergency call, a roaming UE that does not know the PLMN ID of any nearby PLMN may query a DNS server using an emergency ePDG FQDN in order to identify an IP address of a nearby ePDG. The embodiments are not limited in this context.

FIG. 4 illustrates an example of an operating environment 400 that may be representative of the implementation of one or more of the disclosed techniques according to various embodiments. More particularly, operating environment 400 may be representative of some embodiments in which a roaming UE that directs an emergency call to its home PLMN may be provided with the respective PLMN IDs of one or more local PLMNs by a node of its home PLMN.

In operating environment 400, an emergency call may be initiated at UE 102 while UE 102 is roaming and is unaware of any PLMN ID corresponding to a nearby PLMN. In various embodiments, since it is unaware of any PLMN ID corresponding to a nearby PLMN, UE 102 may direct the emergency call to its home PLMN. In some embodiments, in conjunction with directing the emergency call to its home PLMN, UE 102 may initiate a tunnel establishment procedure for establishing secure tunnel 315 to home ePDG 314. In various embodiments, according to the tunnel establishment procedure, UE 102 may send a tunnel establishment request message 426 to home ePDG 314. In some embodiments, UE 102 may send tunnel establishment request message 426 to home ePDG 314 using untrusted non-3GPP IP access 106. In various embodiments, UE 102 may possess untrusted non-3GPP IP access 106 via a WLAN, such as WLAN 103 of FIG. 1, and may send tunnel establishment request message 426 to home ePDG 314 via the WLAN. In some such embodiments, UE 102 may send tunnel establishment request message 426 to home ePDG 314 via an AP of the WLAN, such as AP 104 of FIG. 1. The embodiments are not limited to this example. In various embodiments, UE 102 may include one or more location indication parameters 428 in tunnel establishment request message 426. In some embodiments, each location indication parameter 428 may comprise a parameter that directly or indirectly provides at least a rough indication of the location of UE 102. In various embodiments, UE 102 may include an emergency call indicator 430 in tunnel establishment request message 426. In some

embodiments, emergency call indicator 430 may comprise a flag, bit, or other type of information element set to indicate that tunnel establishment request message 426 is associated with an attempt to place an emergency call. The embodiments are not limited in this context.

In various embodiments, location indication parameters 428 may include geographic coordinates, such as global positioning system (GPS) coordinates, substantially corresponding to the location of UE 102. In some embodiments, location indication parameters 428 may include a civic address, such as a street address, substantially corresponding to the location of UE 102. In various embodiments, location indication parameters 428 may include location information that UE 102 may obtain by querying a location information database. For example, in some embodiments, location indication parameters 428 may include location information that UE 102 may obtain via an HTTP-Enabled Location Delivery (HELD) technique, according to which UE 102 may send a query message comprising its IP address to a location information server and receive location information in a query response message. In various such embodiments, the IP address that UE 102 includes in the query message may correspond to the outer IP header comprised in messages sent to UE 102 via an SWu interface. The embodiments are not limited in this context.

In some embodiments, location indication parameters 428 may include one or more parameters that describe characteristics of AP 104. In various embodiments, for example, location indication parameters 428 may include one or more of geographic coordinates substantially corresponding to the location of AP 104, a civic address substantially

corresponding to the location of AP 104, and a media access control (MAC) address of AP 104. In some embodiments, location indication parameters 428 may include one or more parameters that AP 104 has obtained using one or more Dynamic Host Configuration Protocol (DHCP) extensions for location determination and has provided to UE 102. In various embodiments, for example, location indication parameters 428 may include geographic coordinates that AP 104 has obtained using an Internet Engineering Task Force (IETF) DHCP extension defined in the IETF Request for Comments (RFC) 6225 released in July 2011, and/or one or more

predecessors, revisions, variations, and/or successors thereof. In another example, in some embodiments, location indication parameters 428 may include a civic address that AP 104 has obtained using an IETF DHCP extension defined in the IETF RFC 4676 released in October 2006, and/or one or more predecessors, revisions, variations, and/or successors thereof. The embodiments are not limited to these examples.

In various embodiments, the tunnel establishment procedure may comprise an IKEv2 tunnel establishment procedure for establishing an IPsec tunnel. In some embodiments, tunnel establishment request message 426 may comprise an IKEv2 request message, such as an

IKE_AUTH request message. In various embodiments, tunnel establishment request message 426 may comprise an IKEv2 request message featuring an enhanced format that enables it to be used to convey location indication parameters 428 and/or emergency call indicator 430. In some embodiments, for example, tunnel establishment request message 426 may comprise an enhanced-format IKEv2 request message that can convey location indication parameters 428 and/or emergency call indicator 430 in one or more of a Vendor ID payload, a Notify payload, and a Configuration payload. The embodiments are not limited to this example.

In various embodiments, upon receipt of tunnel establishment request message 426, home ePDG 314 may determine that tunnel establishment request message 426 is associated with an attempt to place an emergency call. In some such embodiments, this determination may be based on emergency call indicator 430 being present within the tunnel establishment request message 426. In various embodiments, based on one or more location indication parameters 428 and/or other information that may be comprised in tunnel establishment request message 426, home ePDG 314 may determine that UE 102 is roaming. In some embodiments, in response to these determinations, rather than proceeding with the tunnel establishment procedure, home ePDG 314 may reject the tunnel establishment request. In various embodiments, home ePDG 314 may send a tunnel establishment response message 432 to UE 102 in conjunction with rejecting the tunnel establishment request. In some embodiments, home ePDG 314 may use the tunnel establishment response message 432 to inform UE 102 of one or more local PLMNs to which it may direct its emergency call, where each such local PLMN comprises a PLMN that home ePDG 314 determines or estimates to be located in the general vicinity of UE 102. In various embodiments, home ePDG 314 may include within tunnel establishment response message 432 a respective local PLMN ID 434 for each of the one or more local PLMNs. The embodiments are not limited in this context.

In some embodiments, home ePDG 314 may estimate an approximate location of UE 102 based on one or more location indication parameters 428 comprised in tunnel establishment request message 426. In various embodiments, the one or more location indication parameters 428 comprised in tunnel establishment request message 426 may include one or more parameters that constitute direct indicators of the location of UE 102. For example, in some embodiments, the one or more location indication parameters 428 may include one or both of GPS coordinates directly corresponding to the location of UE 102 and a civic address substantially corresponding to the location of UE 102. In various embodiments, the one or more location indication parameters 428 comprised in tunnel establishment request message 426 may include one or more parameters that constitute indirect indicators of the location of UE 102. For example, in some embodiments, the one or more location indication parameters 428 may include one or both of geographic coordinates substantially corresponding to the location of AP 104 and a civic address substantially corresponding to the location of AP 104, and given that UE 102 is within wireless communication range of AP 104, the location of AP 104 may constitute a reasonable proxy for the location of UE 102. In another example, in various embodiments, the one or more location indication parameters 428 may include a MAC address of AP 104, and UE 102 may identify an approximate location of AP 104 by querying a database, such as a National Emergency Address Database (NEAD) database, using the MAC address of AP 104. The embodiments are not limited to these examples.

In some embodiments, after estimating the approximate location of UE 102, home ePDG 314 may identify one or more PLMNs that it knows to be located in relatively close proximity to that estimated approximate location as local PLMNs for UE 102. In various embodiments, home ePDG 314 may additionally or alternatively identify one or more local PLMNs for UE 102 without reference to the estimated approximate location of UE 102. For example, in some embodiments, the one or more location indication parameters 428 may include a MAC address of AP 104, and home ePDG 314 may query a database using that MAC address, receive a query response comprising PLMN IDs for one or more PLMNs located in the general vicinity of AP 104, and identify those one or more PLMNs as local PLMNs for UE 102. The embodiments are not limited to this example.

In various embodiments, in response to receipt of tunnel establishment response message 432, UE 102 may direct its emergency call to a local PLMN 413 that corresponds to a local

PLMN ID 434 comprised in tunnel establishment response message 432. In some embodiments, UE 102 may construct a ePDG FQDN 416 using the local PLMN ID 434 corresponding to local PLMN 413, send a query message (not pictured) comprising the ePDG FQDN 416 to DNS server 110, and receive a query response message (not pictured) containing an ePDG IP address 418 that comprises the IP address of an ePDG 414 in local PLMN 413. In various embodiments, UE 102 may then initiate a tunnel establishment procedure to establish a secure tunnel 415 to ePDG 414. In some embodiments, secure tunnel 415 may comprise an IPsec tunnel. In various embodiments, UE 102 may exchange one or more IKEv2 messages with ePDG 414 in order to establish secure tunnel 415. The embodiments are not limited in this context. In some embodiments, after establishing secure tunnel 415 to ePDG 414, UE 102 may direct its emergency call to the IMS of local PLMN 413 via the secure tunnel 415. In various embodiments, ePDG 414 may establish IP connectivity between UE 102 and an IMS core 422 of local PLMN 413 via an IEC PGW 420 that comprises a PGW within local PLMN 413 that is designated for support of IMS emergency calls. In some embodiments, ePDG 414 may identify IEC PGW 420 based on an emergency access point name (Em-APN) that is valid within local PLMN 413. In various embodiments, UE 102 may direct its emergency call to the IMS of local PLMN 413 by sending an SIP request message, such as an SIP INVITE message, to IMS core 422, which may then route the SIP request message to a PSAP 424 within local PLMN 413. The embodiments are not limited in this context.

FIG. 5 illustrates an example of an operating environment 500 that may be representative of the implementation of one or more of the disclosed techniques according to some

embodiments. More particularly, like operating environment 400 of FIG. 4, operating environment 500 may be representative of various embodiments in which a roaming UE that directs an emergency call to its home PLMN may be provided with the respective PLMN IDs of one or more local PLMNs by a node of its home PLMN. However, in operating environment 500, the one or more local PLMNs 434 of FIG. 4 may be provided by home IMS core 322 rather than home ePDG 314.

In operating environment 500, UE 102 may initiate a tunnel establishment procedure to establish secure tunnel 315, obtain IP connectivity to home IMS core 322, and direct its emergency call to the IMS of its home PLMN 313 by sending a session establishment request message 536 to home IMS core 322. In some embodiments, session establishment request message 536 may comprise an SIP request message, such as an SIP INVITE message. In various embodiments, UE 102 may include one or more location indication parameters 428 and/or emergency call indicator 430 in session establishment request message 536.

In some embodiments, upon receipt of session establishment request message 536, home IMS core 322 may determine that session establishment request message 536 is associated with an attempt to place an emergency call. In various such embodiments, this determination may be based on emergency call indicator 430 being present within the session establishment request message 536. In some embodiments, based on one or more location indication parameters 428 and/or other information that may be comprised in session establishment request message 536, home IMS core 322 may determine that UE 102 is roaming.

In various embodiments, in response to these determinations, home IMS core 322 may reject the session establishment request embodied by session establishment request message 536. In some embodiments, home IMS core 322 may send a session establishment response message 538 to UE 102 in conjunction with rejecting the session establishment request. In various embodiments, home IMS core 322 may identify one or more local PLMNs for UE 102 using any of the techniques described above in reference to home ePDG 314 in operating environment 400 of FIG. 4. In some embodiments, home IMS core 322 may include within session establishment response message 538 a respective local PLMN ID 434 for each of those one or more local

PLMNs. In various embodiments, following receipt of session establishment response message 538, UE 102 may construct ePDG FQDN 416, determine ePDG IP address 418, establish secure tunnel 415 to ePDG 414, and direct its emergency call to the IMS core 422 of local PLMN 413 in the same fashion as discussed above in reference to operating environment 400 of FIG. 4. The embodiments are not limited in this context.

FIG. 6 illustrates an example of an operating environment 600 that may be representative of the implementation of one or more of the disclosed techniques according to some

embodiments. In operating environment 600, rather than directing its emergency call to its home PLMN when it is roaming and does not know the PLMN ID of any nearby PLMN, UE 102 may attempt to identify the PLMN IDs of one or more nearby PLMNs by querying a PLMN information database 640. In various embodiments, PLMN information database 640 may generally comprise a database comprising information useable to map one or more types of parameters to PLMN IDs. In some embodiments, PLMN information database 640 may comprise a NEAD database. The embodiments are not limited in this context.

In various embodiments, PLMN information database 640 may include information useable to map MAC addresses to PLMN IDs. In some embodiments, for example, PLMN information database 640 may comprise information defining MAC address-to-location mappings and information defining PLMN ID-to-location mappings, and these two types of mapping information may be used in combination to map MAC addresses to PLMN IDs. In various embodiments, PLMN information database 640 may additionally or alternatively include information usable to map IP addresses to PLMN IDs. In some embodiments, for example, PLMN information database 640 may comprise information defining IP address-to-location mappings and information defining PLMN ID-to-location mappings, and these two types of mapping information may be used in combination to map IP addresses to PLMN IDs. In various embodiments, PLMN information database 640 may additionally or alternatively include information usable to map one or more other types of parameters to PLMN IDs. For example, in some embodiments, PLMN information database 640 may include information usable to map geographic coordinates and/or civic addresses to PLMN IDs. The embodiments are not limited to these examples. In various embodiments, UE 102 may query PLMN information database 640 by sending a query message 642 comprising one or more location indication parameters 428. In some embodiments, in response to the query message 642, UE 102 may receive a query response message (not pictured) comprising one or more local PLMN IDs 434. In various embodiments, the one or more location indication parameters 428 in query message 642 may include a MAC address of AP 104, and the one or more local PLMN IDs 434 in the query response message may include one or more PLMN IDs to which the MAC address of AP 104 maps according to information in PLMN information database 640. In some embodiments, the one or more location indication parameters 428 in query message 642 may additionally or alternatively include an IP address of AP 104, and the one or more local PLMN IDs 434 in the query response message may include one or more PLMN IDs to which the IP address of AP 104 maps according to information in PLMN information database 640.

In various embodiments, the one or more location indication parameters 428 in query message 642 may additionally or alternatively include an IP address of UE 102, and the one or more local PLMN IDs 434 in the query response message may include one or more PLMN IDs to which the IP address of UE 102 maps according to information in PLMN information database 640. In some embodiments, the one or more location indication parameters 428 in query message 642 may additionally or alternatively include one or more other types of parameters, such as geographic locations and/or civic addresses substantially corresponding to the respective locations of UE 102 and/or AP 104, and the one or more local PLMN IDs 434 in the query response message may include one or more PLMN IDs to which one or more such parameters map according to information in PLMN information database 640. The embodiments are not limited in this context.

In various embodiments, following receipt of the query response message comprising the one or more local PLMN IDs 434, UE 102 may construct ePDG FQDN 416, determine ePDG IP address 418, establish secure tunnel 415 to ePDG 414, and direct its emergency call to the IMS core 422 of local PLMN 413 in the same fashion as discussed above in reference to operating environment 400 of FIG. 4. The embodiments are not limited in this context.

FIG. 7 illustrates an example of an operating environment 700 that may be representative of the implementation of one or more of the disclosed techniques according to some

embodiments. In operating environment 700, as in operating environment 600 of FIG. 6, UE 102 may refrain from directing its emergency call to its home PLMN when it does not know the PLMN ID of any nearby PLMN. However, in operating environment 700, UE 102 may also bypass the process according to which it sends a message comprising location indication parameters 428, receives a message comprising one or more local PLMN IDs 434, and constructs ePDG FQDN 416 in operating environments 400, 500, and 600 of FIGs. 4, 5, and 6, respectively.

In operating environment 700, in response to the initiation of an emergency call while it is roaming, UE 102 may send a query message (not pictured) to DNS server 110 that contains an emergency ePDG FQDN 744. In various embodiments, emergency ePDG FQDN 744 may comprise a special dedicated ePDG FQDN designated for use to query DNS servers for ePDG IP addresses during emergencies. In some embodiments, emergency ePDG FQDN 744 may comprise a globally-adopted ePDG FQDN for emergency use, or an otherwise widely- adopted/well-known ePDG FQDN that is reserved for emergency calls. In various

embodiments, emergency ePDG FQDN 744 may comprise the string

'sos.epdg.epc.pub.3gppnetwork.org'. The embodiments are not limited to this example.

In some embodiments, in conjunction with the implementation of emergency ePDG FQDN 744 in any given geographical region, each DNS server in that geographical area may be configured with knowledge of the IP addresses of one or more of its respective nearby ePDGs. In various embodiments, for example, DNS server 110 may be configured with local ePDG information 746 that specifies the IP addresses of one or more ePDGs that are located in the vicinity of DNS server 110. In some embodiments, in response to receipt of the query message from UE 102, DNS server 110 may access local ePDG information 746 and identify ePDG IP address 418 as an IP address of a nearby ePDG. In various embodiments, DNS server 110 may then send a query response message (not pictured) to UE 102 that contains ePDG IP address 418. In some embodiments, following receipt of the query response message, UE 102 may establish secure tunnel 415 to ePDG 414 and direct its emergency call to the IMS core 422 of local PLMN 413 in the same fashion as discussed above in reference to operating environment 400 of FIG. 4. The embodiments are not limited in this context.

Operations for the above embodiments may be further described with reference to the following figures and accompanying examples. Some of the figures may include a logic flow. Although such figures presented herein may include a particular logic flow, it can be appreciated that the logic flow merely provides an example of how the general functionality as described herein can be implemented. Further, the given logic flow does not necessarily have to be executed in the order presented unless otherwise indicated. In addition, the given logic flow may be implemented by a hardware element, a software element executed by a processor, or any combination thereof. The embodiments are not limited in this context.

FIG. 8 illustrates an example of a logic flow 800 that may be representative of the implementation of one or more of the disclosed techniques according to various embodiments. For example, logic flow 800 may be representative of operations that may be performed by UE 102 in operating environment 400 of FIG. 4, operating environment 500 of FIG. 5, and/or operating environment 600 of FIG. 6 according to some embodiments. As shown in FIG. 8, an initiation of an emergency call may be detected at 802 at a roaming UE possessing wireless connectivity with a WLAN. For example, an initiation of an emergency call may be detected at UE 102 while it is roaming and possesses wireless connectivity with WLAN 103 via AP 104. At 804, a first message may be sent via the WLAN, and the first message may comprise one or more location indication parameters. For example, UE 102 may include one or more location indication parameters 428 in a tunnel establishment request message 426, session establishment request message 536, or query message 642 that it sends via AP 104 of WLAN 103.

At 806, a second message may be received in response to the first message, and the second message may comprises one or more PLMN IDs. For example, UE 102 may receive a tunnel establishment response message 432, a session establishment response message 538, or a query response message comprising one or more local PLMN IDs 434 in response to the message sent at 802. At 808, an ePDG FQDN for a PLMN may be determined based on a PLMN ID comprised among the one or more PLMN IDs. For example, UE 102 may determine ePDG FQDN 416 for local PLMN 413 based on one of the one or more PLMN IDs comprised in the message received at 806. At 810, a query message comprising the ePDG FQDN may be sent to a DNS server. For example, UE 102 may send a query message comprising ePDG FQDN 416 to DNS server 110.

At 812, a query response message may be received that comprises an IP address of an ePDG. For example, UE 102 may receive a query response message comprising the ePDG IP address 418 of ePDG 414. At 814, a secure tunnel to the ePDG may be established. For example, UE 102 may establish secure tunnel 415 to ePDG 414. At 816, an emergency call may be directed to an IMS of the PLMN via the secure tunnel to the ePDG. For example, UE 102 may direct an emergency call to IMS core 422 of local PLMN 413 via secure tunnel 415. The embodiments are not limited to these examples.

FIG. 9 illustrates an example of a logic flow 900 that may be representative of the implementation of one or more of the disclosed techniques according to various embodiments. For example, logic flow 900 may be representative of operations that may be performed by UE 102 in operating environment 700 of FIG. 7 according to some embodiments. As shown in FIG. 9, an initiation of an emergency call may be detected at 902 at a roaming UE possessing wireless connectivity with a WLAN. For example, an initiation of an emergency call may be detected at UE 102 while it is roaming and possesses wireless connectivity with WLAN 103 via AP 104. At 904, a query message comprising an emergency ePDG FQDN may be sent to a DNS server via an AP of the WLAN. For example, UE 102 may send a query message comprising emergency ePDG FQDN 744 to DNS server 110 via AP 104.

At 906, a query response message may be received that comprises an IP address of an ePDG of a PLMN. For example, UE 102 may receive a query response message comprising the ePDG IP address 418 of ePDG 414. At 908, a secure tunnel to the ePDG may be established. For example, UE 102 may establish secure tunnel 415 to ePDG 414. At 910, an emergency call may be directed to an IMS of the PLMN via the secure tunnel to the ePDG. For example, UE 102 may direct an emergency call to IMS core 422 of local PLMN 413 via secure tunnel 415. The embodiments are not limited to these examples.

FIG. 10 illustrates an example of a logic flow 1000 that may be representative of the implementation of one or more of the disclosed techniques according to various embodiments. For example, logic flow 1000 may be representative of operations that may be performed by home ePDG 314 in operating environment 400 of FIG. 4 and/or operations that may be performed by home IMS core 322 in operating environment 500 of FIG. 5 according to some embodiments. As shown in FIG. 10, a first message may be received at 1002 that comprises an emergency call indicator and one or more location indication parameters for a roaming UE. For example, home ePDG 314 may receive tunnel establishment request message 426, which may comprise emergency call indicator 430 and one or more location indication parameters 428. In another example, home IMS core 322 may receive session establishment request message 536, which may comprise emergency call indicator 430 and one or more location indication parameters 428. At 1004, one or more PLMNs may be identified based on the one or more location indication parameters. For example, home ePDG 314 or home IMS core 322 may identify one or more local PLMNs for UE 102 based on the one or more location indication parameters 428 comprised in the message received at 1002. At 1006, a second message may be sent that comprises a respective PLMN ID for each of the one or more PLMNs. For example, home ePDG 314 may send tunnel establishment response message 432, which may comprise one or more local PLMN IDs 434, each of which may correspond a respective one of one or more PLMNs identified at 1004. In another example, home IMS core 322 may send session establishment response message 538, which may comprise one or more local PLMN IDs 434, each of which may correspond a respective one of one or more PLMNs identified at 1004. The embodiments are not limited to these examples.

FIG. 11A illustrates an embodiment of a storage medium 1100. Storage medium 1100 may comprise any non-transitory computer-readable storage medium or machine-readable storage medium, such as an optical, magnetic or semiconductor storage medium. In various embodiments, storage medium 1100 may comprise an article of manufacture. In some embodiments, storage medium 1100 may store computer-executable instructions, such as computer-executable instructions to implement one or both of logic flow 800 of FIG. 8 and logic flow 900 of FIG. 9. Examples of a computer-readable storage medium or machine-readable storage medium may include any tangible media capable of storing electronic data, including volatile memory or non-volatile memory, removable or non-removable memory, erasable or nonerasable memory, writeable or re-writeable memory, and so forth. Examples of computer- executable instructions may include any suitable type of code, such as source code, compiled code, interpreted code, executable code, static code, dynamic code, object-oriented code, visual code, and the like. The embodiments are not limited in this context.

FIG. 11B illustrates an embodiment of a storage medium 1150. Storage medium 1150 may comprise any non-transitory computer-readable storage medium or machine-readable storage medium, such as an optical, magnetic or semiconductor storage medium. In various embodiments, storage medium 1150 may comprise an article of manufacture. In some embodiments, storage medium 1150 may store computer-executable instructions, such as computer-executable instructions to implement logic flow 1000 of FIG. 10. Examples of a computer-readable storage medium or machine-readable storage medium and of computer- executable instructions may include any of the respective examples mentioned previously in reference to storage medium 1100 of FIG. 11 A. The embodiments are not limited in this context.

As used herein, the term "circuitry" may refer to, be part of, or include an Application

Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group), and/or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable hardware

components that provide the described functionality. In some embodiments, the circuitry may be implemented in, or functions associated with the circuitry may be implemented by, one or more software or firmware modules. In some embodiments, circuitry may include logic, at least partially operable in hardware. Embodiments described herein may be implemented into a system using any suitably configured hardware and/or software.

FIG. 12 illustrates an example of a UE device 1200 that may be representative of a UE that implements one or more of the disclosed techniques in various embodiments. For example, UE device 1200 may be representative of UE 102 according to various embodiments. In some embodiments, the UE device 1200 may include application circuitry 1202, baseband circuitry 1204, Radio Frequency (RF) circuitry 1206, front-end module (FEM) circuitry 1208 and one or more antennas 1210, coupled together at least as shown. The application circuitry 1202 may include one or more application processors. For example, the application circuitry 1202 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) may include any combination of general-purpose processors and dedicated processors (e.g., graphics processors,

application processors, etc.). The processors may be coupled with and/or may include memory/storage and may be configured to execute instructions stored in the memory/storage to enable various applications and/or operating systems to run on the system.

The baseband circuitry 1204 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 1204 may include one or more baseband processors and/or control logic to process baseband signals received from a receive signal path of the RF circuitry 1206 and to generate baseband signals for a transmit signal path of the RF circuitry 1206. Baseband processing circuity 1204 may interface with the application circuitry 1202 for generation and processing of the baseband signals and for controlling operations of the RF circuitry 1206. For example, in some embodiments, the baseband circuitry 1204 may include a second generation (2G) baseband processor 1204a, third generation (3G) baseband processor 1204b, fourth generation (4G) baseband processor 1204c, and/or other baseband processor(s) 1204d for other existing generations, generations in development or to be developed in the future (e.g., fifth generation (5G), 6G, etc.). The baseband circuitry 1204 (e.g., one or more of baseband processors 1204a-d) may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 1206. The radio control functions may include, but are not limited to, signal modulation/demodulation, encoding/decoding, radio frequency shifting, etc. In some embodiments,

modulation/demodulation circuitry of the baseband circuitry 1204 may include Fast-Fourier Transform (FFT), precoding, and/or constellation mapping/demapping functionality. In some embodiments, encoding/decoding circuitry of the baseband circuitry 1204 may include convolution, tail-biting convolution, turbo, Viterbi, and/or Low Density Parity Check (LDPC) encoder/decoder functionality. Embodiments of modulation/demodulation and encoder/decoder functionality are not limited to these examples and may include other suitable functionality in other embodiments.

In some embodiments, the baseband circuitry 1204 may include elements of a protocol stack such as, for example, elements of an evolved universal terrestrial radio access network (EUTRAN) protocol including, for example, physical (PHY), media access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), and/or radio resource control (RRC) elements. A central processing unit (CPU) 1204e of the baseband circuitry 1204 may be configured to run elements of the protocol stack for signaling of the PHY, MAC, RLC, PDCP and/or RRC layers. In some embodiments, the baseband circuitry may include one or more audio digital signal processor(s) (DSP) 1204f. The audio DSP(s) 1204f may be include elements for compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments. Components of the baseband circuitry may be suitably combined in a single chip, a single chipset, or disposed on a same circuit board in some embodiments. In some embodiments, some or all of the constituent components of the baseband circuitry 1204 and the application circuitry 1202 may be implemented together such as, for example, on a system on a chip (SOC).

In some embodiments, the baseband circuitry 1204 may provide for

communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 1204 may support communication with an evolved universal terrestrial radio access network (EUTRAN) and/or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Embodiments in which the baseband circuitry 1204 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry.

RF circuitry 1206 may enable communication with wireless networks

using modulated electromagnetic radiation through a non-solid medium. In various

embodiments, the RF circuitry 1206 may include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. RF circuitry 1206 may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry 1208 and provide baseband signals to the baseband circuitry 1204. RF circuitry 1206 may also include a transmit signal path which may include circuitry to up-convert baseband signals provided by the baseband circuitry 1204 and provide RF output signals to the FEM circuitry 1208 for transmission.

In some embodiments, the RF circuitry 1206 may include a receive signal path and a transmit signal path. The receive signal path of the RF circuitry 1206 may include mixer circuitry 1206a, amplifier circuitry 1206b and filter circuitry 1206c. The transmit signal path of the RF circuitry 1206 may include filter circuitry 1206c and mixer circuitry 1206a. RF circuitry 1206 may also include synthesizer circuitry 1206d for synthesizing a frequency for use by the mixer circuitry 1206a of the receive signal path and the transmit signal path. In some embodiments, the mixer circuitry 1206a of the receive signal path may be configured to down- convert RF signals received from the FEM circuitry 1208 based on the synthesized frequency provided by synthesizer circuitry 1206d. The amplifier circuitry 1206b may be configured to amplify the down-converted signals and the filter circuitry 1206c may be a low-pass filter (LPF) or band-pass filter (BPF) configured to remove unwanted signals from the down-converted signals to generate output baseband signals. Output baseband signals may be provided to the baseband circuitry 1204 for further processing. In some embodiments, the output baseband signals may be zero-frequency baseband signals, although this is not a requirement. In some embodiments, mixer circuitry 1206a of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect.

In some embodiments, the mixer circuitry 1206a of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 1206d to generate RF output signals for the FEM circuitry 1208. The baseband signals may be provided by the baseband circuitry 1204 and may be filtered by filter circuitry 1206c. The filter circuitry 1206c may include a low-pass filter (LPF), although the scope of the embodiments is not limited in this respect.

In some embodiments, the mixer circuitry 1206a of the receive signal path and the mixer circuitry 1206a of the transmit signal path may include two or more mixers and may be arranged for quadrature downconversion and/or upconversion respectively. In some embodiments, the mixer circuitry 1206a of the receive signal path and the mixer circuitry 1206a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuitry 1206a of the receive signal path and the mixer circuitry 1206a may be arranged for direct downconversion and/or direct upconversion, respectively. In some embodiments, the mixer circuitry 1206a of the receive signal path and the mixer circuitry 1206a of the transmit signal path may be configured for super-heterodyne operation.

In some embodiments, the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternate embodiments, the output baseband signals and the input baseband signals may be digital baseband signals. In these alternate embodiments, the RF circuitry 1206 may include analog-to-digital converter (ADC) and digital-to- analog converter (DAC) circuitry and the baseband circuitry 1204 may include a digital baseband interface to communicate with the RF circuitry 1206.

In some dual-mode embodiments, a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect.

In some embodiments, the synthesizer circuitry 1206d may be a fractional-N synthesizer or a fractional N/N+l synthesizer, although the scope of the embodiments is not limited in this respect as other types of frequency synthesizers may be suitable. For example, synthesizer circuitry 1206d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider.

The synthesizer circuitry 1206d may be configured to synthesize an output frequency for use by the mixer circuitry 1206a of the RF circuitry 1206 based on a frequency input and a divider control input. In some embodiments, the synthesizer circuitry 1206d may be a fractional N/N+l synthesizer.

In some embodiments, frequency input may be provided by a voltage controlled oscillator (VCO), although that is not a requirement. Divider control input may be provided by either the baseband circuitry 1204 or the applications processor 1202 depending on the desired output frequency. In some embodiments, a divider control input (e.g., N) may be determined from a look-up table based on a channel indicated by the applications processor 1202.

Synthesizer circuitry 1206d of the RF circuitry 1206 may include a divider, a delay-locked loop (DLL), a multiplexer and a phase accumulator. In some embodiments, the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DPA). In some embodiments, the DMD may be configured to divide the input signal by either N or N+l (e.g., based on a carry out) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded, tunable, delay elements, a phase detector, a charge pump and a D-type flip-flop. In these embodiments, the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.

In some embodiments, synthesizer circuitry 1206d may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other. In some embodiments, the output frequency may be a LO frequency (fLO). In some

embodiments, the RF circuitry 1206 may include an IQ/polar converter.

FEM circuitry 1208 may include a receive signal path which may include circuitry configured to operate on RF signals received from one or more antennas 1210, amplify the received signals and provide the amplified versions of the received signals to the RF circuitry 1206 for further processing. FEM circuitry 1208 may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry 1206 for transmission by one or more of the one or more antennas 1210. In some embodiments, the FEM circuitry 1208 may include a TX/RX switch to switch between transmit mode and receive mode operation. The FEM circuitry may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry may include a low-noise amplifier (LNA) to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry 1206). The transmit signal path of the FEM circuitry 1208 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by RF circuitry 1206), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 1210.

In some embodiments, the UE device 1200 may include additional elements such as, for example, memory/storage, display, camera, sensor, and/or input/output (I/O) interface.

FIG. 13 illustrates an embodiment of a communications device 1300 that may implement one or more of UE 102, home ePDG 314, a device of home IMS core 322, logic flow 800 of FIG. 8, logic flow 900 of FIG. 9, logic flow 1000 of FIG. 10, storage medium 1100 of FIG. 11 A, storage medium 1150 of FIG. 1 IB, and UE 1200 of FIG. 12. In various embodiments, device 1300 may comprise a logic circuit 1328. The logic circuit 1328 may include physical circuits to perform operations described for one or more of UE 102, home ePDG 314, a device of home IMS core 322, logic flow 800 of FIG. 8, logic flow 900 of FIG. 9, logic flow 1000 of FIG. 10, and UE 1200 of FIG. 12 for example. As shown in FIG. 13, device 1300 may include a radio interface 1310, baseband circuitry 1320, and computing platform 1330, although the

embodiments are not limited to this configuration.

The device 1300 may implement some or all of the structure and/or operations for one or more of UE 102, home ePDG 314, a device of home IMS core 322, logic flow 800 of FIG. 8, logic flow 900 of FIG. 9, logic flow 1000 of FIG. 10, storage medium 1100 of FIG. 11 A, storage medium 1150 of FIG. 11B, UE 1200 of FIG. 12, and logic circuit 1328 in a single computing entity, such as entirely within a single device. Alternatively, the device 1300 may distribute portions of the structure and/or operations for one or more of UE 102, home ePDG 314, a device of home IMS core 322, logic flow 800 of FIG. 8, logic flow 900 of FIG. 9, logic flow 1000 of FIG. 10, storage medium 1100 of FIG. 11 A, storage medium 1150 of FIG. 11B, UE 1200 of FIG. 12, and logic circuit 1328 across multiple computing entities using a distributed system architecture, such as a client-server architecture, a 3-tier architecture, an N-tier architecture, a tightly-coupled or clustered architecture, a peer-to-peer architecture, a master-slave architecture, a shared database architecture, and other types of distributed systems. The embodiments are not limited in this context.

In one embodiment, radio interface 1310 may include a component or combination of components adapted for transmitting and/or receiving single-carrier or multi-carrier modulated signals (e.g., including complementary code keying (CCK), orthogonal frequency division multiplexing (OFDM), and/or single-carrier frequency division multiple access (SC-FDMA) symbols) although the embodiments are not limited to any specific over-the-air interface or modulation scheme. Radio interface 1310 may include, for example, a receiver 1312, a frequency synthesizer 1314, and/or a transmitter 1316. Radio interface 1310 may include bias controls, a crystal oscillator and/or one or more antennas 1318-/. In another embodiment, radio interface 1310 may use external voltage-controlled oscillators (VCOs), surface acoustic wave filters, intermediate frequency (IF) filters and/or RF filters, as desired. Due to the variety of potential RF interface designs an expansive description thereof is omitted.

Baseband circuitry 1320 may communicate with radio interface 1310 to process receive and/or transmit signals and may include, for example, a mixer for down-converting received RF signals, an analog-to-digital converter 1322 for converting analog signals to digital form, a digital-to- analog converter 1324 for converting digital signals to analog form, and a mixer for up-converting signals for transmission. Further, baseband circuitry 1320 may include a baseband or physical layer (PHY) processing circuit 1326 for PHY link layer processing of respective receive/transmit signals. Baseband circuitry 1320 may include, for example, a medium access control (MAC) processing circuit 1327 for MAC/data link layer processing. Baseband circuitry 1320 may include a memory controller 1332 for communicating with MAC processing circuit 1327 and/or a computing platform 1330, for example, via one or more interfaces 1334.

In some embodiments, PHY processing circuit 1326 may include a frame construction and/or detection module, in combination with additional circuitry such as a buffer memory, to construct and/or deconstruct communication frames. Alternatively or in addition, MAC processing circuit 1327 may share processing for certain of these functions or perform these processes independent of PHY processing circuit 1326. In some embodiments, MAC and PHY processing may be integrated into a single circuit.

In various embodiments, in addition to - or rather than - radio interface 1310, device 1300 may comprise one or more interfaces enabling network communications via one or more wired communications media. In some such embodiments, device 1300 may also comprise circuitry for performing PHY and/or MAC layer processing of signals received and/or transmitted via such wired communications media.

The computing platform 1330 may provide computing functionality for the device 1300. As shown, the computing platform 1330 may include a processing component 1340. In addition to, or alternatively of, the baseband circuitry 1320, the device 1300 may execute processing operations or logic for one or more of UE 102, home ePDG 314, a device of home IMS core 322, logic flow 800 of FIG. 8, logic flow 900 of FIG. 9, logic flow 1000 of FIG. 10, storage medium 1100 of FIG. 11 A, storage medium 1150 of FIG. 11B, UE 1200 of FIG. 12, and logic circuit 1328 using the processing component 1340. The processing component 1340 (and/or PHY 1326 and/or MAC 1327) may comprise various hardware elements, software elements, or a combination of both. Examples of hardware elements may include devices, logic devices, components, processors, microprocessors, circuits, processor circuits, circuit elements (e.g., transistors, resistors, capacitors, inductors, and so forth), integrated circuits, application specific integrated circuits (ASIC), programmable logic devices (PLD), digital signal processors (DSP), field programmable gate array (FPGA), memory units, logic gates, registers, semiconductor device, chips, microchips, chip sets, and so forth. Examples of software elements may include software components, programs, applications, computer programs, application programs, system programs, software development programs, machine programs, operating system software, middleware, firmware, software modules, routines, subroutines, functions, methods, procedures, software interfaces, application program interfaces (API), instruction sets, computing code, computer code, code segments, computer code segments, words, values, symbols, or any combination thereof. Determining whether an embodiment is implemented using hardware elements and/or software elements may vary in accordance with any number of factors, such as desired computational rate, power levels, heat tolerances, processing cycle budget, input data rates, output data rates, memory resources, data bus speeds and other design or performance constraints, as desired for a given implementation.

The computing platform 1330 may further include other platform components 1350. Other platform components 1350 include common computing elements, such as one or more processors, multi-core processors, co-processors, memory units, chipsets, controllers, peripherals, interfaces, oscillators, timing devices, video cards, audio cards, multimedia input/output (I/O) components (e.g., digital displays), power supplies, and so forth. Examples of memory units may include without limitation various types of computer readable and machine readable storage media in the form of one or more higher speed memory units, such as read-only memory (ROM), random-access memory (RAM), dynamic RAM (DRAM), Double-Data-Rate DRAM (DDRAM), synchronous DRAM (SDRAM), static RAM (SRAM), programmable ROM (PROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), flash memory, polymer memory such as ferroelectric polymer memory, ovonic memory, phase change or ferroelectric memory, silicon-oxide-nitride-oxide-silicon (SONOS) memory, magnetic or optical cards, an array of devices such as Redundant Array of Independent Disks (RAID) drives, solid state memory devices (e.g., USB memory, solid state drives (SSD) and any other type of storage media suitable for storing information. Device 1300 may be, for example, an ultra- mobile device, a mobile device, a fixed device, a machine-to-machine (M2M) device, a personal digital assistant (PDA), a mobile computing device, a smart phone, a telephone, a digital telephone, a cellular telephone, user equipment, eBook readers, a handset, a one-way pager, a two-way pager, a messaging device, a computer, a personal computer (PC), a desktop computer, a laptop computer, a notebook computer, a netbook computer, a handheld computer, a tablet computer, a server, a server array or server farm, a web server, a network server, an Internet server, a work station, a mini-computer, a main frame computer, a supercomputer, a network appliance, a web appliance, a distributed computing system, multiprocessor systems, processor-based systems, consumer electronics, programmable consumer electronics, game devices, display, television, digital television, set top box, wireless access point, base station, node B, subscriber station, mobile subscriber center, radio network controller, router, hub, gateway, bridge, switch, machine, or combination thereof. Accordingly, functions and/or specific configurations of device 1300 described herein, may be included or omitted in various embodiments of device 1300, as suitably desired.

Embodiments of device 1300 may be implemented using single input single output (SISO) architectures. However, certain implementations may include multiple antennas (e.g., antennas 1318-/) for transmission and/or reception using adaptive antenna techniques for beamforming or spatial division multiple access (SDMA) and/or using MIMO communication techniques.

The components and features of device 1300 may be implemented using any combination of discrete circuitry, application specific integrated circuits (ASICs), logic gates and/or single chip architectures. Further, the features of device 1300 may be implemented using

microcontrollers, programmable logic arrays and/or microprocessors or any combination of the foregoing where suitably appropriate. It is noted that hardware, firmware and/or software elements may be collectively or individually referred to herein as "logic" or "circuit."

It should be appreciated that the exemplary device 1300 shown in the block diagram of

FIG. 13 may represent one functionally descriptive example of many potential implementations. Accordingly, division, omission or inclusion of block functions depicted in the accompanying figures does not infer that the hardware components, circuits, software and/or elements for implementing these functions would be necessarily be divided, omitted, or included in embodiments.

FIG. 14 illustrates an embodiment of a broadband wireless access system 1400. As shown in FIG. 14, broadband wireless access system 1400 may be an internet protocol (IP) type network comprising an internet 1410 type network or the like that is capable of supporting mobile wireless access and/or fixed wireless access to internet 1410. In one or more

embodiments, broadband wireless access system 1400 may comprise any type of orthogonal frequency division multiple access (OFDMA)-based or single-carrier frequency division multiple access (SC-FDMA)-based wireless network, such as a system compliant with one or more of the 3GPP LTE Specifications and/or IEEE 802.16 Standards, and the scope of the claimed subject matter is not limited in these respects.

In the exemplary broadband wireless access system 1400, radio access networks (RANs)

1412 and 1418 are capable of coupling with evolved node Bs (eNBs) 1414 and 1420, respectively, to provide wireless communication between one or more fixed devices 1416 and internet 1410 and/or between or one or more mobile devices 1422 and Internet 1410. One example of a fixed device 1416 and a mobile device 1422 is device 1300 of FIG. 13, with the fixed device 1416 comprising a stationary version of device 1300 and the mobile device 1422 comprising a mobile version of device 1300. RANs 1412 and 1418 may implement profiles that are capable of defining the mapping of network functions to one or more physical entities on broadband wireless access system 1400. eNBs 1414 and 1420 may comprise radio equipment to provide RF communication with fixed device 1416 and/or mobile device 1422, such as described with reference to device 1300, and may comprise, for example, the PHY and MAC layer equipment in compliance with a 3GPP LTE Specification or an IEEE 802.16 Standard. eNBs 1414 and 1420 may further comprise an IP backplane to couple to Internet 1410 via RANs 1412 and 1418, respectively, although the scope of the claimed subject matter is not limited in these respects.

Broadband wireless access system 1400 may further comprise a visited core network (CN)

1424 and/or a home CN 1426, each of which may be capable of providing one or more network functions including but not limited to proxy and/or relay type functions, for example

authentication, authorization and accounting (AAA) functions, dynamic host configuration protocol (DHCP) functions, or domain name service controls or the like, domain gateways such as public switched telephone network (PSTN) gateways or voice over internet protocol (VoIP) gateways, and/or internet protocol (IP) type server functions, or the like. However, these are merely example of the types of functions that are capable of being provided by visited CN 1424 and/or home CN 1426, and the scope of the claimed subject matter is not limited in these respects. Visited CN 1424 may be referred to as a visited CN in the case where visited CN 1424 is not part of the regular service provider of fixed device 1416 or mobile device 1422, for example where fixed device 1416 or mobile device 1422 is roaming away from its respective home CN 1426, or where broadband wireless access system 1400 is part of the regular service provider of fixed device 1416 or mobile device 1422 but where broadband wireless access system 1400 may be in another location or state that is not the main or home location of fixed device 1416 or mobile device 1422. The embodiments are not limited in this context. Fixed device 1416 may be located anywhere within range of one or both of eNBs 1414 and 1420, such as in or near a home or business to provide home or business customer broadband access to Internet 1410 via eNBs 1414 and 1420 and RANs 1412 and 1418, respectively, and home CN 1426. It is worthy of note that although fixed device 1416 is generally disposed in a stationary location, it may be moved to different locations as needed. Mobile device 1422 may be utilized at one or more locations if mobile device 1422 is within range of one or both of eNBs 1414 and 1420, for example. In accordance with one or more embodiments, operation support system (OSS) 1428 may be part of broadband wireless access system 1400 to provide management functions for broadband wireless access system 1400 and to provide interfaces between functional entities of broadband wireless access system 1400. Broadband wireless access system 1400 of FIG. 14 is merely one type of wireless network showing a certain number of the components of broadband wireless access system 1400, and the scope of the claimed subject matter is not limited in these respects.

Various embodiments may be implemented using hardware elements, software elements, or a combination of both. Examples of hardware elements may include processors,

microprocessors, circuits, circuit elements (e.g., transistors, resistors, capacitors, inductors, and so forth), integrated circuits, application specific integrated circuits (ASIC), programmable logic devices (PLD), digital signal processors (DSP), field programmable gate array (FPGA), logic gates, registers, semiconductor device, chips, microchips, chip sets, and so forth. Examples of software may include software components, programs, applications, computer programs, application programs, system programs, machine programs, operating system software, middleware, firmware, software modules, routines, subroutines, functions, methods, procedures, software interfaces, application program interfaces (API), instruction sets, computing code, computer code, code segments, computer code segments, words, values, symbols, or any combination thereof. Determining whether an embodiment is implemented using hardware elements and/or software elements may vary in accordance with any number of factors, such as desired computational rate, power levels, heat tolerances, processing cycle budget, input data rates, output data rates, memory resources, data bus speeds and other design or performance constraints.

One or more aspects of at least one embodiment may be implemented by representative instructions stored on a machine-readable medium which represents various logic within the processor, which when read by a machine causes the machine to fabricate logic to perform the techniques described herein. Such representations, known as "IP cores" may be stored on a tangible, machine readable medium and supplied to various customers or manufacturing facilities to load into the fabrication machines that actually make the logic or processor. Some embodiments may be implemented, for example, using a machine -readable medium or article which may store an instruction or a set of instructions that, if executed by a machine, may cause the machine to perform a method and/or operations in accordance with the embodiments. Such a machine may include, for example, any suitable processing platform, computing platform, computing device, processing device, computing system, processing system, computer, processor, or the like, and may be implemented using any suitable combination of hardware and/or software. The machine-readable medium or article may include, for example, any suitable type of memory unit, memory device, memory article, memory medium, storage device, storage article, storage medium and/or storage unit, for example, memory, removable or non- removable media, erasable or non-erasable media, writeable or re-writeable media, digital or analog media, hard disk, floppy disk, Compact Disk Read Only Memory (CD-ROM), Compact Disk Recordable (CD-R), Compact Disk Rewriteable (CD-RW), optical disk, magnetic media, magneto-optical media, removable memory cards or disks, various types of Digital Versatile Disk (DVD), a tape, a cassette, or the like. The instructions may include any suitable type of code, such as source code, compiled code, interpreted code, executable code, static code, dynamic code, encrypted code, and the like, implemented using any suitable high-level, low- level, object-oriented, visual, compiled and/or interpreted programming language.

The following examples pertain to further embodiments:

Example 1 is a wireless communication method, comprising detecting an initiation of an emergency call at a roaming user equipment (UE) possessing wireless connectivity with a wireless local area network (WLAN), sending, via the WLAN, a first message comprising one or more location indication parameters, and receiving a second message comprising one or more public land mobile network (PLMN) identifiers (IDs) in response to the first message.

Example 2 is the wireless communication method of Example 1 , comprising determining an evolved packet data gateway (ePDG) fully-qualified domain name (FQDN) for a PLMN based on a PLMN ID comprised among the one or more PLMN IDs.

Example 3 is the wireless communication method of Example 2, comprising using the ePDG FQDN to obtain an internet protocol (IP) address of an ePDG of the PLMN.

Example 4 is the wireless communication method of Example 3, comprising sending a query message comprising the ePDG FQDN to a domain name system (DNS) server, and receiving a query response message comprising the IP address of the ePDG.

Example 5 is the wireless communication method of any of Examples 2 to 4, comprising establishing a secure tunnel to the ePDG.

Example 6 is the wireless communication method of Example 5, the secure tunnel to the ePDG comprising an internet protocol security (IPsec) tunnel. Example 7 is the wireless communication method of any of Examples 5 to 6, comprising exchanging one or more Internet Key Exchange Protocol Version 2 (IKEv2) messages with the ePDG in order to establish the secure tunnel to the ePDG.

Example 8 is the wireless communication method of any of Examples 5 to 7, comprising directing the emergency call to an internet protocol multimedia subsystem (IMS) of the PLMN via the secure tunnel to the ePDG.

Example 9 is the wireless communication method of any of Examples 1 to 8, the first message comprising an emergency call indicator.

Example 10 is the wireless communication method of any of Examples 1 to 9, comprising sending the first message to an evolved packet data gateway (ePDG) of a home PLMN of the UE.

Example 11 is the wireless communication method of Example 10, the first message comprising an Internet Key Exchange Protocol Version 2 (IKEv2) request message, the second message comprising an IKEv2 response message received from the ePDG of the home PLMN of the UE.

Example 12 is the wireless communication method of Example 11, the one or more location indication parameters comprised in one or more of a Vendor ID payload, a Notify payload, and a Configuration payload of the IKEv2 request message.

Example 13 is the wireless communication method of any of Examples 11 to 12, the first message comprising an IKE_AUTH request message, the second message comprising an IKE_AUTH response message.

Example 14 is the wireless communication method of any of Examples 1 to 9, comprising directing the first message to an internet protocol multimedia subsystem (IMS) of a home PLMN of the UE.

Example 15 is the wireless communication method of Example 14, the first message comprising a Session Initiation Protocol (SIP) request message, the second message comprising an SIP response message.

Example 16 is the wireless communication method of Example 15, the first message comprising an SIP INVITE message.

Example 17 is the wireless communication method of any of Examples 1 to 9, the first message comprising a query message sent to a remote device to query a PLMN information database, the second message comprising a query response message received from the remote device.

Example 18 is the wireless communication method of Example 17, the PLMN information database comprising a National Emergency Address Database (NEAD). Example 19 is the wireless communication method of any of Examples 1 to 18, the one or more location indication parameters including geographic coordinates substantially

corresponding to a location of the UE.

Example 20 is the wireless communication method of any of Examples 1 to 19, the one or more location indication parameters including geographic coordinates substantially

corresponding to a location of an access point (AP) of the WLAN.

Example 21 is the wireless communication method of any of Examples 1 to 20, the one or more location indication parameters including a civic address substantially corresponding to a location of the UE.

Example 22 is the wireless communication method of any of Examples 1 to 21, the one or more location indication parameters including a civic address substantially corresponding to a location of an access point (AP) of the WLAN.

Example 23 is the wireless communication method of any of Examples 1 to 22, the one or more location indication parameters including a media access control (MAC) address of an access point (AP) of the WLAN.

Example 24 is an apparatus, comprising at least one memory, and logic, at least a portion of which is implemented in circuitry coupled to the at least one memory, the logic to perform a wireless communication method according to any of Examples 1 to 23.

Example 25 is a system, comprising the apparatus of Example 24, and at least one radio frequency (RF) transceiver.

Example 26 is the system of Example 25, comprising at least one RF antenna.

Example 27 is the system of any of Examples 25 to 26, comprising a touchscreen display. Example 28 is at least one non-transitory computer-readable storage medium comprising a set of wireless communication instructions that, in response to being executed on a computing device, cause the computing device to perform a wireless communication method according to any of Examples 1 to 23.

Example 29 is an apparatus, comprising means for performing a wireless communication method according to any of Examples 1 to 23.

Example 30 is a system, comprising the apparatus of Example 29, and at least one radio frequency (RF) transceiver.

Example 31 is the system of Example 30, comprising at least one RF antenna.

Example 32 is the system of any of Examples 30 to 31, comprising a touchscreen display. Example 33 is a wireless communication method, comprising detecting an initiation of an internet protocol multimedia subsystem (IMS) emergency call at a roaming user equipment (UE) possessing wireless connectivity with a wireless local area network (WLAN), sending a query message comprising an emergency evolved packet data gateway (ePDG) fully-qualified domain name (FQDN) to a domain name system (DNS) server, and receiving a query response message comprising an internet protocol (IP) address of an ePDG of a PLMN.

Example 34 is the wireless communication method of Example 33, comprising directing the emergency call to an IMS of the PLMN via the ePDG of the PLMN.

Example 35 is the wireless communication method of any of Examples 33 to 34, comprising directing the emergency call to the IMS of the PLMN via a WLAN access point (AP) and the ePDG of the PLMN.

Example 36 is the wireless communication method of any of Examples 33 to 35, comprising establishing a secure tunnel to the ePDG.

Example 37 is the wireless communication method of Example 36, the secure tunnel to the ePDG comprising an internet protocol security (IPsec) tunnel.

Example 38 is the wireless communication method of any of Examples 36 to 37, comprising exchanging one or more Internet Key Exchange Protocol Version 2 (IKEv2) messages with the ePDG in order to establish the secure tunnel to the ePDG.

Example 39 is the wireless communication method of any of Examples 36 to 38, comprising directing the emergency call to the IMS of the PLMN via the secure tunnel to the ePDG.

Example 40 is the wireless communication method of any of Examples 33 to 39, the emergency ePDG FQDN comprising 'sos.epdg.epc.pub.3gppnetwork.org'.

Example 41 is an apparatus, comprising at least one memory, and logic, at least a portion of which is implemented in circuitry coupled to the at least one memory, the logic to perform a wireless communication method according to any of Examples 33 to 40.

Example 42 is a system, comprising the apparatus of Example 41, and at least one radio frequency (RF) transceiver.

Example 43 is the system of Example 42, comprising at least one RF antenna.

Example 44 is the system of any of Examples 42 to 43, comprising a touchscreen display. Example 45 is at least one non-transitory computer-readable storage medium comprising a set of wireless communication instructions that, in response to being executed on a computing device, cause the computing device to perform a wireless communication method according to any of Examples 33 to 40.

Example 46 is an apparatus, comprising means for performing a wireless communication method according to any of Examples 33 to 40.

Example 47 is a system, comprising the apparatus of Example 46, and at least one radio frequency (RF) transceiver. Example 48 is the system of Example 47, comprising at least one RF antenna.

Example 49 is the system of any of Examples 47 to 48, comprising a touchscreen display.

Example 50 is a method for communicating in a network, comprising receiving, at a node of a communication network, a request message comprising an emergency call indicator and one or more location indication parameters for a roaming user equipment (UE), identifying one or more public land mobile networks (PLMNs) based on the one or more location indication parameters, and sending a response message comprising a respective PLMN identifier (ID) for each of the one or more PLMNs.

Example 51 is the method of Example 50, the response message to comprise a rejection of a request indicated by the request message.

Example 52 is the method of any of Examples 50 to 51, the node comprising an evolved packet data gateway (ePDG) of a home PLMN of the roaming UE.

Example 53 is the method of Example 52, the request message comprising an Internet Key Exchange Protocol Version 2 (IKEv2) request message, the response message comprising an IKEv2 response message.

Example 54 is the method of Example 53, the one or more location indication parameters comprised in one or more of a Vendor ID payload, a Notify payload, and a Configuration payload of the IKEv2 request message.

Example 55 is the method of any of Examples 53 to 54, the IKEv2 request message comprising an IKE_AUTH request message, the IKEv2 response message comprising an IKE_AUTH response message.

Example 56 is the method of any of Examples 50 to 51, the node comprising an element of an internet protocol multimedia subsystem (IMS) of a home PLMN of the roaming UE.

Example 57 is the method of Example 56, the request message comprising a Session Initiation Protocol (SIP) request message, the response message comprising an SIP response message.

Example 58 is the method of any of Examples 56 to 57, the request message comprising an SIP INVITE message.

Example 59 is the method of any of Examples 50 to 58, the one or more location indication parameters including geographic coordinates substantially corresponding to a location of the roaming UE.

Example 60 is the method of any of Examples 50 to 59, the one or more location indication parameters including geographic coordinates substantially corresponding to a location of an access point (AP) of a wireless local area network (WLAN) to which the roaming UE is connected. Example 61 is the method of any of Examples 50 to 60, the one or more location indication parameters including a civic address substantially corresponding to a location of the roaming UE.

Example 62 is the method of any of Examples 50 to 61, the one or more location indication parameters including a civic address substantially corresponding to a location of an access point (AP) of a wireless local area network (WLAN) to which the roaming UE is connected.

Example 63 is the method of any of Examples 50 to 62, the one or more location indication parameters including a media access control (MAC) address of an access point (AP) of a wireless local area network (WLAN) to which the roaming UE is connected.

Example 64 is the method of Example 63, comprising identifying at least one of the one or more PLMNs by querying a PLMN information database based on the MAC address of the AP.

Example 65 is the method of Example 64, the PLMN information database comprising a National Emergency Address Database (NEAD).

Example 66 is an apparatus, comprising at least one memory, and logic, at least a portion of which is implemented in circuitry coupled to the at least one memory, the logic to perform a method according to any of Examples 50 to 65.

Example 67 is a system, comprising the apparatus of Example 66, and at least one network interface.

Example 68 is the system of Example 67, comprising at least one processor.

Example 69 is at least one non-transitory computer-readable storage medium comprising a set of instructions that, in response to being executed on a computing device, cause the computing device to perform a method according to any of Examples 50 to 65.

Example 70 is an apparatus, comprising means for performing a method according to any of Examples 50 to 65.

Example 71 is a system, comprising the apparatus of Example 70, and at least one network interface.

Example 72 is the system of Example 71, comprising at least one processor.

Numerous specific details have been set forth herein to provide a thorough understanding of the embodiments. It will be understood by those skilled in the art, however, that the embodiments may be practiced without these specific details. In other instances, well-known operations, components, and circuits have not been described in detail so as not to obscure the embodiments. It can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments.

Some embodiments may be described using the expression "coupled" and "connected" along with their derivatives. These terms are not intended as synonyms for each other. For example, some embodiments may be described using the terms "connected" and/or "coupled" to indicate that two or more elements are in direct physical or electrical contact with each other. The term "coupled," however, may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other.

Unless specifically stated otherwise, it may be appreciated that terms such as "processing,"

"computing," "calculating," "determining," or the like, refer to the action and/or processes of a computer or computing system, or similar electronic computing device, that manipulates and/or transforms data represented as physical quantities (e.g., electronic) within the computing system' s registers and/or memories into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, transmission or display devices. The embodiments are not limited in this context.

It should be noted that the methods described herein do not have to be executed in the order described, or in any particular order. Moreover, various activities described with respect to the methods identified herein can be executed in serial or parallel fashion.

Although specific embodiments have been illustrated and described herein, it should be appreciated that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. It is to be understood that the above description has been made in an illustrative fashion, and not a restrictive one. Combinations of the above

embodiments, and other embodiments not specifically described herein will be apparent to those of skill in the art upon reviewing the above description. Thus, the scope of various embodiments includes any other applications in which the above compositions, structures, and methods are used.

It is emphasized that the Abstract of the Disclosure is provided to comply with 37 C.F.R. § 1.72(b), requiring an abstract that will allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate preferred embodiment. In the appended claims, the terms "including" and "in which" are used as the plain- English equivalents of the respective terms "comprising" and "wherein," respectively. Moreover, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

CLAIMS What is claimed is:

1. An apparatus, comprising:

at least one memory; and

logic, at least a portion of which is implemented in circuitry coupled to the at least one memory, the logic to:

detect an initiation of an emergency call at a roaming user equipment (UE) possessing wireless connectivity with a wireless local area network (WLAN);

send, via the WLAN, a first message comprising one or more location indication parameters; and

receive a second message comprising one or more public land mobile network (PLMN) identifiers (IDs) in response to the first message.

2. The apparatus of claim 1, the logic to:

determine an evolved packet data gateway (ePDG) fully-qualified domain name (FQDN) for a PLMN based on a PLMN ID comprised among the one or more PLMN IDs;

use the ePDG FQDN to obtain an internet protocol (IP) address of an ePDG of the PLMN; and

direct the emergency call to an internet protocol multimedia subsystem (IMS) of the PLMN via a secure tunnel to the ePDG.

3. The apparatus of claim 1, the first message to contain an emergency call indicator.

4. The apparatus of claim 1, the first message to comprise an Internet Key Exchange Protocol Version 2 (IKEv2) request message to be sent to an evolved packet data gateway (ePDG) of a home PLMN of the UE, the second message to comprise an IKEv2 response message to be received from the ePDG of the home PLMN of the UE.

5. The apparatus of claim 1, the first message to comprise a Session Initiation Protocol (SIP) request message to be directed to an internet protocol multimedia subsystem (IMS) of a home PLMN of the UE, the second message to comprise an SIP response message to be received in response to the SIP request message.

6. The apparatus of claim 1 , the one or more location indication parameters to include at least one of:

geographic coordinates substantially corresponding to a location of the UE; and geographic coordinates substantially corresponding to a location of an access point (AP) of the WLAN.

7. The apparatus of claim 1, the one or more location indication parameters to include at least one of:

a civic address substantially corresponding to a location of the UE; and

a civic address substantially corresponding to a location of an access point (AP) of the WLAN.

8. The apparatus of claim 1, the one or more location parameters to include a media access control (MAC) address of an access point (AP) of the WLAN.

9. A system, comprising:

an apparatus according to any of claims 1 to 8;

at least one radio frequency (RF) transceiver; and

at least one RF antenna.

10. At least one non-transitory computer-readable storage medium comprising a set of wireless communication instructions that, in response to being executed at user equipment (UE), cause the UE to:

send a request message to a node of a home public land mobile network (PLMN) of the UE via a wireless local area network (WLAN) while the UE is roaming, the request message comprising an emergency call indication and at least one location indication parameter; and receive a response message identifying at least one PLMN; and

direct an internet protocol multimedia subsystem (IMS) emergency call to an IMS of a PLMN identified in the response message.

11. The at least one non-transitory computer-readable storage medium of claim 10, the request message to comprise an Internet Key Exchange Protocol Version 2 (IKEv2) request message, the second message to comprise an IKEv2 response message.

12. The at least one non-transitory computer-readable storage medium of claim 11, the at least one location indication parameter to include at least one parameter comprised in a Vendor ID payload, Notify payload, or Configuration payload of the IKEv2 request message

13. The at least one non-transitory computer-readable storage medium of claim 10, the request message to comprise a Session Initiation Protocol (SIP) request message, the second message to comprise an SIP response message.

14. The at least one non-transitory computer-readable storage medium of claim 10, the at least one location indication parameter to include one or more of:

15. The at least one non-transitory computer-readable storage medium of claim 10, the at least one location indication parameter to include one or more of:

a civic address substantially corresponding to a location of the UE; and

16. The at least one non-transitory computer-readable storage medium of claim 10, the at least one location parameter to include a media access control (MAC) address of an access point (AP) of the WLAN.

17. The at least one non-transitory computer-readable storage medium of claim 10, comprising wireless communication instructions that, in response to being executed at the UE, cause the UE to:

determine an evolved packet data gateway (ePDG) fully-qualified domain name (FQDN) based on a PLMN identifier (ID) comprised in the response message;

query a domain name system (DNS) server using the ePDG FQDN in order to determine an internet protocol (IP) address of an ePDG;

establish an internet protocol security (IPsec) tunnel to the ePDG; and

direct the IMS emergency call to the IMS of the PLMN via the IPsec tunnel to the ePDG.

18. At least one non- transitory computer-readable storage medium comprising a set of instructions that, in response to being executed at a node of a communication network, cause the node to:

receive a request message comprising an emergency call indicator and one or more location indication parameters for a roaming user equipment (UE);

identify one or more public land mobile networks (PLMNs) based on the one or more location indication parameters; and

send a response message comprising a respective PLMN identifier (ID) for each of the one or more PLMNs.

19. The at least one non-transitory computer-readable storage medium of claim 18, the node to comprise an evolved packet data gateway (ePDG) of a home PLMN of the roaming UE.

20. The at least one non-transitory computer-readable storage medium of claim 19, the request message to comprise an Internet Key Exchange Protocol Version 2 (IKEv2) request message, the response message to comprise an IKEv2 response message.

21. The at least one non-transitory computer-readable storage medium of claim 20, the one or more location indication parameters to be comprised in one or more of a Vendor ID payload, a Notify payload, and a Configuration payload of the IKEv2 request message.

22. The at least one non-transitory computer-readable storage medium of claim 18, the node to comprise an element of an internet protocol multimedia subsystem (IMS) of a home PLMN of the roaming UE, the request message to comprise a Session Initiation Protocol (SIP) request message, the response message to comprise an SIP response message.

23. The at least one non-transitory computer-readable storage medium claim 18, the one or more location indication parameters to include at least one of:

geographic coordinates substantially corresponding to a location of the roaming UE; and geographic coordinates substantially corresponding to a location of an access point (AP) of a wireless local area network (WLAN) to which the roaming UE is connected.

24. The at least one non-transitory computer-readable storage medium claim 18, the one or more location indication parameters to include at least one of:

a civic address substantially corresponding to a location of the roaming UE; and a civic address substantially corresponding to a location of an access point (AP) of a wireless local area network (WLAN) to which the roaming UE is connected.

25. The at least one non-transitory computer-readable storage medium claim 18, the one or more location indication parameters to include a media access control (MAC) address of an access point (AP) of a wireless local area network (WLAN) to which the roaming UE is connected.