VoWiFi extends and enriches LTE services

Next Generation Communications Blog

VoWiFi extends and enriches LTE services

By: David E. Nowoswiat, Senior Product and Solutions Marketing Manager, IP Routing & Transport, and  Ed Elkin, Head of Marketing for IP Communication, Alcatel-Lucent

The growing importance and usage of Wi-Fi™ is spurring rapid development in voice over Wi-Fi (VoWiFi) to complement robust VoLTE services. Mobile device manufacturers are taking advantage of Wi-Fi to solidify their relationship with consumers and enterprises, so mobile network operators (MNOs) need to act quickly to secure a share in the hot Wi-Fi market. By developing a strategy that encompasses Wi-Fi, MNOs can leverage their most important asset - their LTE network - to deliver a seamless experience for subscribers while leveraging their virtualized IMS investment to create  new revenue opportunities for themselves.

Benefits of VoWiFi for MNO subscribers   

  • Seamless – Unrestricted connectivity and mobility between Wi-Fi and cellular IP networks enables new VoLTE services to be used anywhere, even outside of LTE coverage
  • Simple – Easy to use and connect with automatic network discovery and authentication
  • Secure – Strong network security from a trusted operator that protects data from unlawful intercept and hacking
  • Savings – Voice and video calling everywhere with service bundles that can lower rates and reduce roaming fees

 Benefits of VoWiFi for MNOs

  • Increased coverage and capacity – MNOs and MVNOs can address LTE coverage gaps with Wi-Fi hotspots, using any open Wi-Fi, or selectively using closed Wi-Fi that they or their partners provide.
  • Optimized network access – Roaming and bandwidth-intensive video traffic advanced features costs can be reduced by offloading from the cellular network to Wi-Fi.
  • Ability to extend services easily to Wi-Fi – Subscriber’s wireless access can be managed holistically across multiple services.

 Challenges of adding Wi-Fi to LTE networks

There are two main challenges:  

  • Service continuity
    • Mobile device IP addresses must be preserved when moving between LTE and Wi-Fi, to ensure seamless handovers of calls and other network services such as enterprise VPNs.
  • Service consistency/security
    • Public Wi-Fi networks are susceptible to hacking. Secure tunneling protocols and subscriber authentication methods are required.

Fortunately, these challenges are addressed with the new mobile network architecture that combines Wi‑Fi/cellular access with new Evolved Packet Core (EPC) functions.  The architecture is described in 3GPP Technical Specification 23.402 (Architecture Enhancements for non-3GPP Services).

ALU.WoWiFi.2.19.15.JPGEPC architecture for LTE with Wi-Fi access

In the standards, Wi-Fi is considered a type of non-3GPP wireless access, which the MNO can view as either a trusted network or an untrusted network. To support these two network access types, two core network functions are needed:

  • Evolved Packet Data Gateway (ePDG) - Supports the untrusted non-3GPP Wi-Fi access network
  • Trusted Wireless Access Gateway (TWAG) - Supports the trusted non-3GPP Wi-Fi access network

For simplicity, we focus in this blog on the ePDG, but both methods perform similar functions for their respective access networks:

  • Secure tunneling and aggregation of traffic from Wi-Fi access points (APs)
  • Interface to the AAA server for authentication of the mobile device to the EPC
  • Access to the EPC via secure tunneling mechanisms (GTP or PMIP) to the MNO’s packet gateway (PGW) which provides the IP address for the mobile device
  • Create the session request for bearer establishment and do the VoWiFi call data forwarding between the Wi-Fi access network and MNO’s PGW

Although VoWiFi is the primary focus here, the method is transparent to the services (including Internet, enterprise VPNs and IMS).  Indeed, this is the beauty of the solution.  Implementation is relatively lightweight: an ePDG is added to the network and a slight update is made to the device’s client. In return, the solution works for any Wi-Fi AP (because no integration is required) and for any service (such as IMS, enterprise VPN and content delivery networks).  The TWAG is similar, except it doesn’t require an update to the device, but does require integration with the Wi-Fi AP.

VoWiFi  - part of the new IP communications customer experience

When the Wi-Fi/cellular access is used with a virtualized IMS that comes equipped with native APIs, MNOs can deliver new services to their consumers and enterprises.  These include:

  • Video-call offload.  Video calls consume approximately 400 Megabytes/hour, which can cause pricing reluctance in some subscribers.  Yet video brings a new human dynamic to communications, with visual cues and warmth. It can be used creatively, with ambient video, uni-casting, app-embedded video snippets, and so on.  By enabling subscribers to easily choose LTE or Wi-Fi, prior to or during the call, the MNO encourages subscribers to experiment with video.
  • Increased coverage.  VoLTE has better audio and newer features than 3G circuit voice.  No longer constrained to the limitations imposed by the 2G/3G HLR/VLR voice roaming architecture, the MNO is free to rapidly create and deploy new features.  However, the MNO might not have complete LTE coverage, or it might be using a very high LTE frequency that has line-of-sight characteristics.  Using VoWiFi to fill in coverage gaps, the MNO ensures the new VoLTE service works anywhere. 
  • Multi-device. The new mobile architecture enables tablets and laptops equipped with only Wi-Fi to attach to the MNO's network and use its services. Subscribers can choose the most convenient device.  For example, they can answer an incoming call on their tablet, when their smartphone is not within reach.  Multi-device services are particularly interesting, as they can move the call interaction from today’s mode of calling a phone number (which is associated with one device) to calling a person (who can choose to answer the call on whichever device they prefer). 
  • Roaming.  Subscribers can easily stay in touch when traveling, using voice and IP messaging (which interworks with SMS texting).  They can continue to use their home network services even while not connected to the service provider’s access network, and reduce the spending that normally occurs while roaming.

Witness seamless VoWi-Fi / VoLTE services at MWC

The new conversation experience is becoming a commercial reality: visit our booth (Hall #3, booth 3K10) at Mobile World Congress 2015 for a live demonstration of VoWiFi and VoLTE.  You will see it in action on an Apple® iPhone 6, and implemented on an Android by D2 Technologies and InterDigital Technologies, over our vEPC/ePDG and vIMS network.

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