When the topic of voice calls using WiFi on a smartphone comes up is often related to making cheap--or free--calls, and bypassing the cellular operators' fees. With the exception of international roaming, I never understood the big appeal of cheap or free voice calls in markets like the U.S. where we typically have more minutes in our buckets than we know what to do with.
Would I bother to find a WiFi location to make a quick call? It is extremely unlikely. For an important and long conference call, do I want to use WiFi over cellular? Maybe, but in that case I will probably be sitting down, and use the WiFi connection over the laptop. Being able to use WiFi to save on calls is a nice-to-have feature, but not one that is likely to be a major driver for handset selection.
Coverage, coverage, coverage
However, there are situations in which Voice over WiFi (VoWiFi) capabilities can be extremely valuable to subscribers, especially if the service is fully integrated with cellular voice. If you happen to live or work in a place where cellular coverage is not available or reliable (I used to fall in both categories), you know what I am talking about.
As long as you have a broadband connection, a WiFi access point, and a WiFi and Unlicensed Mobile Access (UMA) handset, you can make and receive calls over your WiFi connection as if they were routed through the cellular network. Handoffs to the cellular network are also supported, but they usefulness (and availability) is limited in areas with uneven cellular coverage, as the phone has no network to handoff to, and UMA is typically not used in mobile usage scenarios, e.g., when you are making a call while walking or in a car.
I have used it for many years and in most cases it is difficult to know whether you are using WiFi or cellular. The UMA software works in the background and it is completely transparent to the subscribers. In fact, it is not even cheap. The software is free, but the calls routed through WiFi are counted towards your monthly allocation. If you do not have coverage, this is a fair deal. You are not looking for cheap service; you just want to make sure receive your calls.
However, because you can make and receive calls from anywhere your phone can connect to a WiFi network, UMA also allows saving on roaming charges. When you are abroad, you can connect to a WiFi access point and make calls as if you were in your country. If you happen to be in Korea or Japan and do not have a phone that works there, UMA may be the only way to use your phone.
More than VoWiFi
The reason why UMA works so well is that it is much more than VoWiFi: It goes beyond the wireless link and it integrated with the cellular network. A phone connected through UMA is recognized as part of the cellular network. When a call is placed to a handset with a UMA connection, the UMA gateway routes the call through the WiFi access point the handset it connected to. When a UMA handset initiates a call, the cellular core network manages it as if it were a cellular call
The tight integration with the cellular network is what makes UMA powerful, but also not trivial to use for subscribers. They cannot just download a UMA app--they need to have a plan with an operator that has adopted UMA, and use a handset that supports UMA. In the U.S., T-Mobile USA is the only operator that offers UMA on some of their WiFi phones, so it is only a fraction of U.S. mobile subscribers who can use it. (UMA is only available for GSM-based networks, and this further restricts availability in the U.S., where Verizon Wireless and Sprint Nextel do not use this technology).
With this long detour, I hope to have convinced you that the value of VoWiFi goes well beyond cheap calls and that UMA is a valuable tool, for subscribers to get coverage and for operators to provide better coverage than competitors in difficult-to-reach areas. UMA fulfills the same role of a femtocell, but without requiring any additional hardware to be installed in the subscriber home if there is a WiFi access point.
Android, meet UMA
Now let's get to Android. Android phones (or the iPhone for that matter) seem to be a perfect fit for UMA. To date however UMA users have been disappointed, and in many cases delayed or avoided a transition to Android phones because they may end up losing their precious UMA coverage at home or in the office. The recent announcement by Kineto Wireless that a client for UMA is available for Android phones got the UMA crowd excited about the possibility of finally getting UMA on their phones and there has been a lively debate in blogs on why we can't just download an app to add UMA to Android phones.
Taking UMA to Android phones
This would clearly be desirable, but coordination is needed between the handset manufacturer and the operator to ensure that UMA works as expected within the cellular network. Firmware is required from the manufacturer. The operator has to add support for specific UMA devices. For applications like Skype, none of this is required because the calls are routed as data streams that are completely separate from the voice cellular network. As UMA calls are managed within the cellular core network, the operator has to use security mechanisms to protect the network and ensure reliability. In turn, this translates in more consistent and secure calls for the subscriber, as well as a seamless experience.
At least in the near future, we should continue to expect UMA to be available only on a selection of handsets and most commonly to be pre-installed when the handset is purchased. Over-the-air firmware upgrades may also become available if the operator decides to do so.
Will T-Mobile extend UMA support to Android devices?
T-Mobile has been understandably silent on this issue, as mobile operators do not typically announce features ahead of availability, but there is wide expectation that they will add UMA support for Android phones--most likely for the Vibrant and the G2. The marginal cost of adding UMA support for Android phones is minimal, and the potential for differentiation from other operators is significant. T-Mobile can offer femtocell-like capabilities to all their Android subscribers as part of their current service and without the need of another piece of hardware. Unofficial reports have surfaced that suggest that T-Mobile is indeed prepping a launch of VoWiFi services for Android phones, but it is not entirely clear whether it is a solution that is based on UMA, as it is reportedly similar to Skype, used to make calls (not to receive them), and does not support handoffs. Support for handoffs could be eliminated without affecting the core UMA functionality, but the ability to receive calls is crucial to UMA, and its main differentiator from other VoWiFi applications when used to enhance cellular coverage. Often when in an area with limited or no cellular coverage, the subscriber may use fixed lines or VoIP as alternatives to place calls. Receiving calls is typically the challenging part. As the T-Mobile has shown it can support both outgoing and incoming calls, it would be a pity if it would rollout a watered down VoWiFi application--or none at all.
Monica Paolini, PhD, is the founder and president of Senza Fili Consulting and can be contacted at [email protected]. Senza Fili Consulting provides expert advisory services on wireless data technologies and services.