Wi-Fi calling using SIP-IMS handset and evolved packet data gateway

1. A method, comprising:

determining, by a mobile device, whether any Long-Term Evolution (LTE) coverage is available;

determining, by the mobile device, whether data roaming is available;

determining, by the mobile device, whether a visited public land mobile network (VPLMN) is available;

determining, by the mobile device, whether a domain name server (DNS) query to a first evolved packet data gateway (ePDG) is successful;

connecting the mobile device to the first ePDG responsive to a determination that LTE coverage is available, a determination that data roaming is available, a determination that a VPLMN is available, and a determination that the DNS query to the first ePDG is successful;

routing Session Initiation Protocol-Internet Protocol (IP) Multimedia Subsystem (SIP-IMS) traffic between the mobile device and a packet data network (PDN) gateway through via a Wi-Fi access point and the first ePDG while the mobile device is connected to the first ePDG, and routing over-the-top (OTT) applications traffic to an Internet service provider (ISP) network via the Wi-Fi access point while the mobile device is connected to the first ePDG; and

connecting the mobile device to a second ePDG responsive to a determination that no data roaming is available or a determination that no LTE coverage is available.

2. The method of claim 1 , wherein the connecting the mobile device to the second ePDG comprise:

connecting the mobile device to the ISP network via the Wi-Fi access point; and

registering the mobile device to an Internet Protocol (IP) Multimedia Subsystem (IMS) network via an IMS access point name (APN) through an ePDG Internet Protocol Security (IPSec) tunnel.

3. The method of claim 2 , further comprising:

establishing data connectivity through the Wi-Fi access point; and

establishing voice over Wi-Fi (VoWiFi) connectivity through the Wi-Fi access point.

4. The method of claim 2 , further comprising:

placing a 3 rd Generation Partnership Project (3GPP) radio of the mobile device in a sleep mode; and

periodically searching for a 3GPP radio access technology (RAT) and a public land mobile network (PLMN).

5. The method of claim 2 , further comprising: enabling voice calls through the IMS network through the Wi-Fi access point.

6. The method of claim 5 , wherein the enabling of the voice calls through the IMS network comprises providing a seamless transition of a voice call over the IMS network from LTE to Wi-Fi and from Wi-Fi to LTE.

7. The method of claim 2 , further comprising:

enabling an IMS packet data network (PDN) Internet Protocol Security (IPSec) tunnel; and

routing rich communication services (RCS) signals and media traffic through the IMS PDN IPSec tunnel.

8. The method of claim 7 , wherein the enabling of the IMS PDN IPSec tunnel comprises maintaining the IMS PDN IPSec tunnel on Wi-Fi when a received signal strength indication (RSSI) level of Wi-Fi signals is above a threshold value.

9. The method of claim 8 , wherein the threshold value is −75 dBm.

10. The method of claim 2 , further comprising:

enabling an IMS packet data network (PDN) Internet Protocol Security (IPSec) tunnel; and

routing video calling signals and media traffic through the IMS PDN IPSec tunnel.

11. The method of claim 10 , wherein the routing of the video calling signals through the IMS PDN IPSec tunnel comprises providing a seamless transition of a video call through the IMS PDN IPSec tunnel from LTE to Wi-Fi and from Wi-Fi to LTE.

12. The method of claim 10 , wherein the enabling of the IMS PDN IPSec tunnel comprises maintaining the IMS PDN IPSec tunnel on Wi-Fi when a received signal strength indication (RSSI) level of Wi-Fi signals is above a threshold value.

13. The method of claim 12 , wherein the threshold value is −75 dBm.

14. The method of claim 1 , further comprising:

determining, by the mobile device, that LTE coverage is available following connection of the mobile device to the second ePDG via the Wi-Fi access point;

initiating handover between LTE and Wi-Fi by considering one or more metrics comprising:

a received signal strength indication (RSSI) level;

downlink and uplink packet error rates;

Real-time Transport Protocol (RTP) Control Protocol (RTCP) information; and

LTE reference signal received power (RSRP) and reference signal received quality (RSRQ) information.

15. The method of claim 1 , wherein the connecting the mobile device to the second ePDG includes establishing IMS packet data network (PDN) connectivity via the Wi-Fi access point, further comprising:

attaching a 3 rd Generation Partnership Project (3GPP) radio of the mobile device to an LTE network while the mobile device is connected to the second ePDG via the Wi-Fi access point;

making a determination, by the mobile device, that the (3GPP) radio of the mobile device fell back from the LTE network to a Universal Mobile Telecommunications System (UMTS) or Global System for Mobile Communications (GSM) radio access technology (RAT); and

in response to the determination, detaching the 3GPP radio of the mobile device from the UMTS or GSM RAT, and placing the 3GPP radio in a sleep mode in order to scan for a LTE coverage.

16. The method of claim 1 , further comprising: establishing, by an ePDG application on the mobile device, an Internet Protocol Security (IPSec) tunnel.

17. The method of claim 16 , wherein the establishing of the IPSec tunnel comprises performing one or more of operations comprising:

establishing and maintaining three or more packet data network (PDN) connections simultaneously;

establishing the IPSec tunnel based on Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6);

selecting a first public land mobile network (PLMN) of a plurality of PLMNs as a home PLMN, identifications of the plurality of PLMNs stored in the mobile device; and

supporting one or more static IP addresses and one or more fully qualified domain names (FQDN) for the second ePDG responsive to connecting to the second ePDG.

18. A device, comprising:

a memory configured to store data and one or more sets of processor-executable instructions; and

a processor coupled to the memory, the processor configured to access the memory to execute the one or more sets of processor-executable instructions to perform operations comprising:

determining whether to connect to a first evolved packet data gateway (ePDG) or a second ePDG by performing operations comprising:

determining, by a mobile device, whether any Long-Term Evolution (LTE) coverage is available;

determining, by the mobile device, whether data roaming is available;

determining, by the mobile device, whether a visited public land mobile network (VPLMN) is available;

determining, by the mobile device, whether a domain name server (DNS) query to the first ePDG is successful;

connecting the mobile device to the first ePDG responsive to a determination that LTE coverage is available, a determination that data roaming is available, a determination that a VPLMN is available, and a determination that the DNS query to the first ePDG is successful; and

connecting the mobile device to the second ePDG responsive to a determination that no data roaming is available while the VPLMN is available, or a determination that no LTE coverage is available while the VPLMN is available.

19. The device of claim 18 , wherein the processor is configured to further perform one or more operations comprising:

placing a 3 rd Generation Partnership Project (3GPP) radio of the mobile device in a sleep mode;

periodically searching for a 3GPP radio access technology (RAT) and a public land mobile network (PLMN);

enabling voice calls through an IMS network through a Wi-Fi access point;

enabling an IMS packet data network (PDN) Internet Protocol Security (IPSec) tunnel;

routing rich communication services (RCS) signals and media traffic through the IMS PDN IPSec tunnel;

routing video calling signals and media traffic through the IMS PDN IPSec tunnel;

determining, by the mobile device, that LTE coverage is available following connection of the mobile device to the second ePDG via the Wi-Fi access point; and

initiating handover between LTE and Wi-Fi by considering one or more metrics comprising:

a received signal strength indication (RSSI) level;

downlink and uplink packet error rates;

Real-time Transport Protocol (RTP) Control Protocol (RTCP) information; and

LTE reference signal received power (RSRP) and reference signal received quality (RSRQ) information.

20. The device of claim 19 , wherein in enabling of the voice calls through the IMS network the processor is configured to provide a seamless transition of a voice call over the IMS network from LTE to Wi-Fi and from Wi-Fi to LTE, wherein in enabling the IMS PDN IPSec tunnel the processor is configured to maintain the IMS PDN IPSec tunnel on Wi-Fi when a RSSI level of Wi-Fi signals is above a threshold value of −75 dBm, wherein in routing the video calling signals through the IMS PDN IPSec tunnel the processor is configured to provide a seamless transition of a video call through the IMS PDN IPSec tunnel from LTE to Wi-Fi and from Wi-Fi to LTE, and wherein in establishing the IPSec tunnel the processor is configured to perform one or more of operations comprising:

establishing and maintaining three or more PDN connections simultaneously;

establishing the IPSec tunnel based on Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6);

selecting a first PLMN of a plurality of PLMNs as a home PLMN, identifications of the plurality of PLMNs stored in the mobile device; and

supporting one or more static IP addresses and one or more fully qualified domain names (FQDN) for the second ePDG responsive to connecting to the second ePDG.