VoWiFi Solution Considerations
Solution Description
Solution 1: UMA
Solution 2: Direct connection to the IMS network
Solution 3: untrusted access to ePDG (EPC)/IMS
Solution 4: trusted access to EPC/IMS
Solution 5: OTT
Solution 1: UMA
- Unlicensed Mobile Access (UMA) uses a Generic Access Network Controller (GANC) to virtualize mobile phones using Wi-Fi access to 2G/3G mobile phones.
- Mobile phones using Wi-Fi access connect to a CS network over the standard A/Iu interface. This facilitates traditional mobile services in the CS domain when Wi-Fi is available
- UMA is available for commercial uses only in the North America and some European countries
- UMA does not support the LTE network and IMS Core, and has been abandoned in the entire industry.
Solution 2: Direct connection to the IMS network
- Wi-Fi network connects to the IMS network directly
- UE IP address may change after a WLAN-LTE handover
- Unified authentication and unified subscriber number are unavailable
- Handovers have high requirements on UEs and the IMS network
- Roaming and interworking are complex
- Due to lack of native UEs, subscribers must download an App and apply for accounts and passwords
- Seamless handovers to VoLTE networks are unavailable, and voice call continuity to 2G/3G networks cannot be ensured
- VoBB and RCS solutions support this mode.
Solution 3: untrusted access to ePDG (EPC)/IMS
- UEs access 3GPP networks over the S2b interface through untrusted public WLAN networks
- P-GW serves as the anchoring point of WLAN-LTE handovers
- UEs must support IPSec and IKEV2 authentication
- 3GPP release 10 supports this solution
- Terminal maturity: iPhone 6/iOS 8 has been globally released
- Samsung has released Android-based customized UEs in the North America
- Carriers have released this solution for commercial uses or highly focus on this solution
- 3GPP release 10 supports this solution.
Solution 4: trusted access to EPC/IMS
- UEs access 3GPP networks over the S2a interface through carriers' WLAN networks
- P-GW serves as the anchoring point of WLAN-LTE handovers
- WLAN-LTE handovers will be available in 3GPP
- 3GPP release 12 is completed recently. No chip or UE supports this solution
- Carriers must deploy their own Wi-Fi networks
- Existing third-party Wi-Fi networks cannot be used
Solution 5: OTT
- An App must be downloaded
- Independent user names and passwords are required
- Cal Waiting and Call Forwarding services are not supported
- Service experience may be inconsistent with that on the VoLTE and CS networks
- Due to lack of native UEs, subscriber must download an App - similar to OTT solutions Skype, WhatsApp, and WeChat
- Calls addressed to non-OTT subscribers are charged
- A mobile subscriber cannot use the MSISDN to receive calls from OTT subscribers
