Technical Analysis on Huawei VoWiFi Solution
The Voice over Wi-Fi (VoWiFi) service, also called Wi-Fi Calling, enables subscribers to use smartphones that support VoWiFi to dial numbers to initiate voice or video calls when Wi-Fi connection is available.Huawei VoWiFi solution complies with 3GPP specifications. It based on the EPC (ePDG), SingleSDB (3GPP AAA), and IMS as the core control architecture.
When common subscribers access network under Wi-Fi hotspots, they can enjoy HD voice & video service and seamless handover between VoLTE and VoWiFi.
I. Benefits
VoWiFi addresses problems of insufficient coverage at initial VoLTE deployment phase, decreases MVNO's air interface rent, provides cost-effective international roaming services. In addition, carriers attract more subscribers using VoWiFi or retain subscribers using competitive packages to increase carrier revenue and enhance carrier competitiveness.
II. Deployment Solution
VoWiFi has been applied for multiple years, and Wi-Fi calling standard in 3GPP has gradually being completed. The following five deployment solutions are available:
Comparison between common VoWiFi deployment solutions
|
Item |
Description |
Current Status |
|
Solution 1: UMA |
The Unlicensed Mobile Access (UMA) virtualizes mobile phones accessing through Wi-Fi into 2G/3G mobile phones and connect the phones to CS networks, implementing mobile CS services in Wi-Fi scenarios. The mapping product is generic access network controller (GANC). |
The UMA is available for commercial use only in North America and some countries in Europe. The technical evolution has stooped. The UMA does not support LTE and IMS Core and has been abandoned. |
|
Solution 2: Direct connection to the IMS network |
The way access the IMS network directly via Wi-Fi network can't gurantee UE addresses have no change after WLAN-LTE handover. It is difficult to realize unified authentication and subscriber numbers. And Handover have special requirements on UEs and the IMS network.Roaming and interworking scenarios are complex. |
No native UEs are available. Subscribers need to download an app and apply for an account and a password. |
|
Solution 3: Untrusted access to ePDG (EPC) and IMS |
UEs access 3GPP networks over the S2b interface through untrusted public WLAN networks. The P-GW functions as the anchoring point of WLAN-LTE handovers. UEs must support IPsec and IKEv2 authentication. 3GPP release 10 supports this solution. |
iPhone 6 and iOS8 have been released. Samsung, SONY, and Nokia have provided commercial terminals. Carriers have provided solutions for commercial use or are paying close attention. 3GPP release 10 supports this solution. |
|
Solution 4: Trusted access to EPC and IMS |
UEs access 3GPP networks over the S2a interface through trusted WLAN networks deployed by carriers. The P-GW functions as the anchoring point of WLAN-LTE handovers. WLAN-LTE handovers are under discussion in 3GPP. |
3GPP release 12 is completed recently. No chip or UE supports this solution. Carriers need to deploy Wi-Fi but cannot use existing third-party Wi-Fi. |
|
Solution 5: OTT |
Subscribers need to download an app. An account and a password are required for login. Call waiting and call forwarding services are not supported. VoLTE and CS subscriber service consistency cannot be ensured, and interworking capabilities are restricted. |
No native UEs are available. Subscribers need to download an app, such as Skype, WhatsApp, and WeChat. VoLTE and CS subscriber service consistency cannot be ensured, and interworking capabilities are restricted. |
To sum up, solutions 2 and 3 are available for commercial use. Most carriers select the two solutions.
III. Huawei VoWiFi Solution
The Huawei VoWiFi solution complies with 3GPP specifications and uses the EPC (ePDG), SingleSDB (3GPP AAA), and IMS as the core control architecture. The Huawei VoWiFi solution uses untrusted WLAN access (native VoWiFi) or direct connection to IMS (VoWiFi with app).
Untrusted Wi-Fi Access
The ePDG is mandatory for untrusted Wi-Fi access.
Subscriber authentication: UEs access the ePDG through untrusted Wi-Fi, and the AAA server and HSS perform authentication. SIM card based authentication (EAP-AKA/EAP-SIM) is used, and subscribers are not sensible of the authentication.
Network security: IPsec channels are established between Wi-Fi UEs and the ePDG to ensure data transmission security.
Voice continuity: UEs hand over freely between Wi-Fi and LTE eNodeBs to ensure voice continuity.
HD voice: VoWiFi and VoLTE share the same core network and use the same HD codecs to provide high-quality audio/video services for subscribers.
Self-help service activation: The CDM authenticates terminals and performs automatic service provisioning. Subscribers can register VoWiFi using self-help services to accelerate VoWiFi commercial use. This mitigates impacts of UE re-registrations on networks.
The Huawei VoWiFi network reuses the VoLTE architecture. Carriers can deploy the ePDG or upgrade the live EPC network, deploy the 3GPP AAA or upgrade the live SDM to deploy VoWiFi. In addition, the CDM shortens service activation cycles and accelerate VoWiFi commercial use. For carriers that have deployed commercial VoLTE networks and plan to deploy commercial VoLTE networks, untrusted Wi-Fi access is the optimal choice.
Direct Access to the IMS Network
Huawei SDK-based app: The Huawei VoWiFi with app is based on Huawei SDKs, which can detect voice quality and determine handovers. Subscribers can use VoWiFi services after accessing the IMS networking using the app.
Network security: STG channels are established between UEs and the SBC using SIP over TLS, SRTP, or MSRP over TLS. All-scenario handover: The Huawei SDK based app VoWiFi implements handovers to LTE networks and Wi-Fi to UMTS handovers. Subscribers can hand over among LTE, Wi-Fi, and GPS networks to ensure voice continuity.
HD audio/video: The SDKs provide diverse audio/video codecs and support adaptation. The SDKs support voice enhancement capabilities acoustic echo cancellation (AEC), packet loss compensation (PLC), voice activity detection (VAD), and jitter buffer.
App VoWiFi is easy to deploy and is an optimal choice for fixed carriers who want to develop mobile services but do not want to develop VoLTE services. To sum up, the Huawei VoWiFi solution supports flexible deployment, quick release, and convergence with VoLTE. Core network NEs on the VoWiFi and VoLTE networks support cloudification (vIMS, vEPC, and vSDM) to meet cloud-based evolution requirements.
IV. Mature VoWiFi Technologies
Key technologies required for VoWiFi, such as authentication, QoS, security, voice continuity, and emergency call, are mature and have been applied for VoWiFi. Key technologies required for VoWiFi are listed in the following table.|
Direct Access to the IMS |
Untrusted WLAN |
|
|
Wi-Fi |
Hotspot 2.0 |
Hotspot 2.0/ANDSF |
|
Authentication and authorization |
User name/password, one-time password (OTP) |
SIM card based (EAP-AKA/EAP-SIM) authentication |
|
QoS |
TCP layer QoS controllable |
QoS between UEs and the ePDG is difficult to ensure. |
|
Security |
STG channels are established between UEs and the SBC using SIP over TLS, SRTP, or MSRP over TLS. |
IPsec channels are established between UEs and the ePDG. |
|
Voice continuity |
DRVCC: Wi-Fi to 3G PS handovers LTE to Wi-Fi handovers |
DRVCC: Wi-Fi to 3G PS handovers LTE to Wi-Fi handovers |
|
Emergency call |
Call fallback to CS (only for phone and no precise location information) |
Call fallback to CS (only for phone and no precise location information) |
Huawei provides mature solutions and implements quick deployment on the basis of VoLTE, implementing perfect 4G communication experience for subscribers. The Huawei VoWiFi solution has been widely applied in the global word, and Huawei became a strategic partner of carriers in 4G convergence communication field.