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VoWifi: benefits and drawbacks

(Image credit: Image Credit: Everything Possible / Shutterstock)

There’s no doubt that Voice over Wi-Fi (VoWiFi) has captured a lot of attention lately. Indeed, A&T has announced that it is handling four million VoWiFi calls per day and T-Mobile boasts some 22 million calls per day using the technology.  Today, 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 and neither do mobile operators want it to be.   

VoWiFi 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 of such traffic in 2020. While mobile operators are also implementing IP voice over LTE (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 a few years ago, but the other major operators have now jumped on the bandwagon. 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 cell phone platforms like Apple’s IOS and Google’s Android now natively support VoWiFi. 

Benefits and drawbacks 

Over the past few years VoWiFi technology has made great strides in call quality and reliability, and mobile operators like the technology for several reasons, including:   

  • The number of Wi-Fi hotspots is growing rapidly. Many residential units have Wi-Fi networks, and Informa estimated that there would be 5.8 million Wi-Fi hotspots around the world by the end of 2015
  • VoWiFi enables non-subscriber – i.e. no SIM – devices like Wi-Fi tablets to make calls
  • VoWiFi enables free calls from overseas locations
  • VoWiFi is an inexpensive way for mobile operators to augment services inside buildings – particularly residential units – when macro network signals don’t penetrate well

Among these, in-building coverage in residences and offices seems to be a major driver of operator interest in VoWiFi. VoWiFi represents an ‘easy button’ for mobile operators and enterprises wanting to deliver in-building wireless voice services. By relying on homeowner- or enterprise-supplied Wi-Fi hotspots, mobile operators can offload traffic from the macro network and hopefully provide superior service. 

Enterprises are drawn to the solution for a number of reasons, including: 

  • Wi-Fi works in unlicensed frequency bands, so VoWiFi can be implemented without wireless operator permission or involvement
  • VoWiFi leverages an investment that, in most cases, has already been made by the enterprise – their Wi-Fi network – so incremental spend may be minimal
  • As long as the user has a device which supports VoWifi, the service is universal – it’s not specific to any one operator, but can be used by anyone with a device that supports it and is granted access to the Wi-Fi network

On the other hand, VoWiFi has some inherent drawbacks that make quality of service a continuing problem, including:   

  • Mobile operators have no control over Wi-Fi networks. Wi-Fi is a best-effort service that 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 necessary to cannibalize 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 an unlicensed frequency – as opposed to licensed mobile frequencies – so it’s subject to interference from many sources
  • There’s 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. In fact, an enterprise may have VoWiFi for its employees, but visitors wouldn’t know the network password and wouldn’t be able to access the network
  • 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 currently no E-911 capability in VoWiFi

Use cases for VoWiFi technology

Given its potential drawbacks, VoWiFi is better suited for residential or Small Office/Home Office (SoHo) applications. Larger buildings can implement VoWiFi, but it has scalability issues. For example, the number of users VoWiFi can support depends on what type of Wi-Fi network is in place. A 5000 square foot office building 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.

VoWiFi for mobile operators

Revenue is the main stumbling block for mobile operators when they consider VoWiFi. Mobile operators are already facing stagnating revenue curves, and VoWiFi doesn’t help, because Wi-Fi calls are free. For this reason, mobile voice will always be the main voice service because it delivers revenue. In addition, mobile voice offers guaranteed quality of service and has high scalability to support buildings of any size.  The main attraction for VoWiFi for mobile operators is that it reduces customer churn by helping them deliver voice services in buildings that can’t get service from the mobile network, and it does so without requiring any capital expenditures by the operator. However, it’s difficult for mobile operators to get very enthusiastic about a service that takes away from the bottom line. This is why along with supporting VoWiFi, most major mobile operators sell residential femtocells that bring outdoor mobile signals inside homes.

Ultimately, mobile operators need to remember that as with any solution, one size doesn’t fit all, and this is especially true for VoWiFi. While It’s a good solution for smaller buildings with low user density, VoWiFi is not the solution for all in-building coverage challenges. 

Image Credit: Everything Possible / Shutterstock

David Del Fava
David Del Fava is VP North American Services and is responsible for the design, distribution and implementation of distributed antenna systems in the Americas.