What's the impact of Voice over Wi-Fi on Small Cells?

Fran-Heeran-150When we often consider how cellular networks can adapt to growing capacity and coverage demands, Wi-Fi clearly has a role to play. With the launch of Voice over Wi-Fi and the migration of services towards an all-encompassing IP model, we ask how that impacts small cell take-up. We spoke with Fran Heeran, SVP for IP Communications Business at Alcatel-Lucent for his take on this topic.

Fran looks after both fixed and mobile aspects of carrier and enterprise IP Communications, which leverages IMS technology. He's not part of their Small Cell division, so provides a slightly different perspective.

Where are we with VoLTE today?

VoLTE (Voice over LTE) commercial deployments have increased significantly this year with services now available from carriers in the U.S., South Korea, Hong Kong and Japan. It is an all IP voice and video communications service running on LTE mobile networks providing HD quality audio, very fast call setup (less than 1 second) and support for both voice and video calling. Its tight integration with the network allows for a far higher quality of service compared to alternative, OTT voice services

At this early stage of market launch, there is little to no VoLTE interoperability between operators. However Verizon and AT&T are among several carriers who have announced plans to introduce this during 2015, when you would be able to make an end-to-end VoLTE call between networks.

How does Voice over Wi-Fi work?

Once you have VoLTE in commercial service, a next logical step is Voice over Wi-Fi (VoWi-Fi). End users can make or receive calls over Wi-Fi or LTE and their call will transition seamlessly from one network to the other while maintaining active call sessions. Although there is one significant difference in that voice and video calls over Wi-Fi will be "best effort" and cannot get the guaranteed Quality of Service (QoS) that is available over LTE due the nature of the network. However, voice and video Wi-Fi calling can bring significant benefits to carriers – notably enhanced coverage where LTE network coverage may be poor or non-existent, and also network traffic offload for bandwidth intensive services such as video calling.

With Wi-Fi calling much of the work is done in conjunction with core mobile network (EPC) interacting with the handset. Ideally, an active call session will maintain the same IP address as you transition between LTE and Wi-Fi, anchored through the EPC. The data connection is routed either through the EPDG (Enhanced Packet Data Gateway) if coming from an untrusted Wi-Fi network or the TWAG (Trusted Wireless Access Gateway) if connected to a trusted/secure hotspot (e,g one provided by the operator). If the smartphone decides it wants to execute a handover to Wi-Fi, then a secure connection is established to the network and the IP address is seamlessly transitioned to the new connection. This provides a secure IP connection through the mobile operator's core network terminating in the same IP address regardless of whether it's using Wi-Fi or LTE. A significant benefit of this approach is that it can be used for more than communication services but also video or any other service. The IMS portion of the VoLTE network can use this method effectively to deliver HD voice services through Wi-Fi just as easily as through cellular. Pretty much any Wi-Fi hotspot can be used and depends on carrier choices for setting up the service.

And since this call set-up procedure is integrated into the smartphone natively, there is no need to use a separate app since this will operate exactly the same when using Wi-Fi or the cellular network.

What about seamless handover to/from Wi-Fi?

There are perhaps half a dozen smartphone devices commercially available today which can do this. I'd expect it to become more of a standard feature in the future. The latest generation of phones has thresholds defined that detect a weakening signal and figure out when Wi-Fi is below a set threshold. There needs to be some intelligence to avoid flip-flopping between Wi-Fi and the cellular network – that's the really clever piece – and this is an evolving aspect of the solution.

Why has RCS (Rich Communications Services) failed?

While I would agree that RCS has currently failed to penetrate the mass market, I don't think this is necessarily a permanent state. The primary reason it hasn't taken off is until it's universally available through the majority of primary mobile operators, its usefulness to the consumer is limited. I do believe 2015 is the year for all IP services. VoLTE first, then moving SMS to IP messaging using RCS or RCS light. I've met a number of (mobile) carriers with significant plans for RCS for next year, intending to provide that rich messaging experience similar to WhatsApp but ubiquitous and not needing a separate app. It all comes down to what will be the default basic service. I'd speculate that in the long term, this would be RCS or an evolution of it.

Why won't voice and messaging from Apple, Google, Facebook etc. just take over?

Each of these has its own services but they aren't interoperable. Apple Facetime only works between Apple devices and not with Android. But the goal is to know you can connect to anyone, anywhere regardless of what device or network operator they use.

What we're also seeing is that carriers are aiming to go further with their new communication services, bringing communications as a feature into any device or application, and doing some clever things with the call flows. Examples include changing the call flows based on different situations. We have several demonstrations of machine-to-person communications including an in car demo where you can automatically handle calls differently depending on whether you are alone in the car or with a passenger. Enterprises could develop their own rule-based call handling to match their own needs. I think that is where carriers are going to go, customizing services for enterprises and introducing more value added services for consumers.

So what are the implications for Small Cells?

Wi-Fi calling will have its place, but will be challenged by small cells in both the residential and enterprise. Call quality, phone support and transfer to the cell network will play an important role in the residential case. In the case of enterprise, I don't think enterprises want to add that kind of traffic onto their internal Wi-Fi networks or for services needing very good quality, so I see small cell/Femto market becoming very enterprise oriented and growing dramatically. Outdoor and urban/metro small cells are essential because Wi-Fi is less effective in those situations. We also see different approaches from different operators in relation to the residential market and a Wi-Fi or Femto approach (and in some cases both).

Over time, Hotspot 2.0 will provide easier access to hotspots and that will trickle into Wi-Fi calling. From a call quality point of view, it will always be a balance of the benefit vs. user experience. For example, carriers with very good network coverage may choose to use Wi-Fi calling purely for traffic offload purposes, perhaps limiting it to video offload and maintain voice calls on the LTE network, as Verizon did when they launched VoLTE.

Overall, I'd see Wi-Fi calling as another important tool deployed by operators and which has its own place, but is not nirvana. In the long term, small cell/large cell/Wi-Fi and fixed broadband will all appear as one seamless wireless network to the user, who won't realise just how much engineering lies beneath. Seamless interoperability between these different access technologies combined with the availability of our carrier communications services across all our IP devices (not just our phone) will be key over the coming years.

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