Opinion: Pros and cons of VoWiFi

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VoWiFi has captured a lot of attention lately. A&T recently announced that it’s handling four million VoWiFi calls a day, upon which T-Mobile countered that it boasts some 22 million calls per day using the technology. Now, many enterprises and mobile operators consider VoWiFi an easy and cost-effective way to provide indoor mobile coverage in buildings that block macro mobile signals. However, VoWiFi isn’t suitable for every application, nor do mobile operators want it to be.

Market momentum

VoWiFi usage is on the rise. According to Cisco, VoWiFi traffic will grow from 15.7 percent of all mobile IP voice traffic in 2015 to 52.9 percent in 2020. While mobile operators are also implementing IP VoLTE, Cisco projects that VoLTE usage will only grow from 18 percent in 2015 to 26.3 percent in 2020. The real push toward VoWiFi started with T-Mobile, but other major operators have now followed suit. VoLTE deployment has also spurred VoWiFi because both are IP services and you can hand off the Wi-Fi connection to VoLTE when users roam from a Wi-Fi-provisioned building to an outdoor environment. Finally, handset support is critical and major mobile phone platforms now natively support VoWiFi.

Pros and cons

VoWiFi technology has recently made great strides in call quality and reliability. Mobile operators like the technology because of the growing number of Wi-Fi hotspots. Moreover, VoWiFi enables non-subscriber devices like Wi-Fi tablets to make calls and enables free calls overseas.  It’s also inexpensive for operators to augment services inside buildings when macro network signals don’t penetrate well. 

Enterprises are drawn to VoWiFi, firstly because Wi-Fi works in unlicensed frequency bands, so VoWiFi can be implemented without wireless operator permission or involvement.  VoWiFi also leverages an investment that, in most cases, has already been made by the enterprise (their Wi-Fi network) so incremental spend may be minimal.  Furthermore, as long as the user has a device which supports VoWifi, the service is universal – it’s not specific to any one operator.

Despite these benefits, VoWiFi does have some drawbacks.  Indeed, mobile operators have no control over Wi-Fi networks. Wi-Fi was not originally designed to support voice and when enterprise Wi-Fi networks are loaded with data traffic, voice traffic becomes a second-class citizen.  It is also necessary to cannibalise Wi-Fi data capacity in order to dedicate channels to voice service. In enterprises, most people use Wi-Fi for data, so dedicating channels to voice service may impact data service. 

Wi-Fi is also an unlicensed frequency, so it’s subject to interference from many sources.  There’s also no transparent auto-connect for Wi-Fi calls.  Callers are not automatically transferred from the mobile network to Wi-Fi when they enter a building with one or more Wi-Fi hotspots.  Furthermore, maintenance is problematic; carriers are not responsible for troubleshooting and repairing Wi-Fi networks. Instead, residential Wi-Fi users and enterprise IT departments are responsible.  There’s also currently no E-911 capability in VoWiFi.

Given these potential drawbacks, VoWiFi is better suited for residential or SoHo applications. Larger buildings can implement VoWiFi, but it has scalability issues. The number of users VoWiFi can support depends on what type of Wi-Fi network is in place. A 5,000 square foot office might have roughly 35 users, but the call capacity on a 2.4GHz Wi-Fi network is four users. If the network uses 5GHz technology, the capacity goes up to 18 users, which would be acceptable, but many of these smaller buildings still use 2.4GHz technology.

Where VoWiFi fits for mobile operators

Mobile voice will always be the main voice service because it offers mobile operators revenue, guaranteed quality of service and has high scalability to support buildings of any size.  The main attraction for VoWiFi is that it reduces customer churn without requiring any capital expenditures by the operator. However, it’s difficult for mobile operators to get enthusiastic about a service that takes away from the bottom line. Along with supporting VoWiFi, most major operators sell residential femtocells that bring outdoor mobile signals inside homes.

When considering VoWiFi, it’s important to remember that as with any solution, one size doesn’t fit all. VoWiFi is a good solution for smaller buildings with low user density, but it’s not a panacea for all in-building coverage challenges.

Do you have any further thoughts on VoWiFI? Let us know in the comments.


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