Mobile VoIP – Back to reality
After a few months trying different Mobile VoIP client apps and VoIP service providers, I reached an approaching state of mind: the reality of Mobile VoIP is not pretty, primarily because the 3G data networks of the wireless carriers can not be relied upon to support critical voice applications.
VoIP solutions work fine on non congested WiFi networks
In order to be acceptable, a true Mobile VoIP service should have at least the same level of performance as a conventional GSM service: you should be reachable anywhere and reliably, you should be able to place calls when you feel like it or need it, and once engaged in a conversation, you should not loose the connection or have to drop because of a poor call quality.
Practically, the requirements are met in controlled environments: at home or in the office, on non-congested WiFi networks. With some caveats, the two VoIP clients and the two VoIP service providers I tested provide a solution whose quality is good enough: your correspondents reach you, and supposing the Wireless LAN is not congested, the quality of service will be good enough.
In any case, my recommendation would be to buy an optional G729 Codec from the vendor of the VoIP app, in order to limit the bandwidth requirements to a bare minimum.
Wireless data networks are not reliable enough for voice applications
Unfortunately, as soon as you leave home or the office, you have to rely on the data network of your favorite carrier, and that’s where the problems start.
The coverage of data networks is not as good as the coverage of the good old GSM or CDMA networks, and it’s very likely that you will miss a few calls a day, or that you will not be able to place a call when you absolutely need it, for lack of a good enough data connection. To me it’s simply not acceptable, and it disqualifies mobile VoIP as a primary mobile telephony solution.
There are different ways to implement Mobile VoIP (with UDP or TCP call control, with or without a third party notification gateway that wakes up the smartphone when a call is being received), so it’s difficult to formulate a definitive opinion about battery life. In some cases, I had to recharge my phone every few hours.
While traveling abroad, VoIP over WiFi networks is a nice way to call people back home, but VoIP over wireless data connections is not a practical option: if you stay with your US carrier, data roaming is horrendously expensive, and if you take a local data subscription from a local wireless carrier, you could be up for some serious configuration work (various gateways), without any guarantee that the local carrier’s data network is capable of supporting voice.
A much better option is to subscribe to a local GSM Voice service (and get a local phone number), and let your VoIP service provider redirect your incoming calls to your local mobile number over its own IP network (for a few Cents per minute).
The VoIP Apps (running Bria or Acrobits on a smartphone)I tested two softphone apps for iOS, Acrobit’s Groundwire and Counterpath’s Bria. There are other VoIP clients on the marketplace, but some of them come with some unpleasant strings attached.
Acrobit’s Groundwire and Counterpath’s Bria are two mature VoIP apps, recommended or supported by the major VoIP service providers, with relatively little to differentiate them.The development teams update their application and extend their feature set very regularly, and what looks like an advantage of one product today might disappear in a few weeks or a few months as the other product catches up.
Counterpath, the developer of Bria, is a well known Canadian vendor of softphones and VoIP gateways, and they have versions of their VoIP clients for iOS, Android, as well as Windows and Mac OS X.
Acrobits is a smaller company, based in Europe, and at the moment, their softphone application is only available for the iOS and Android platform.
Technically, both products work very well. Acrobit’s Groundwire has a few advantages over Bria. Or it had last time I checked. There are more configuration options for the technology savvy, but some features work better with Bria: for instance, you can reliably enter DTMF codes to navigate IVRs, ASRs and other automated systems (I could never make it work with Groundwire).
Very interestingly, Groundwire also offers a gateway service that relays SIP calls received over UDP to Apple’s push notification system. (more about the different technical ways to implement VoIP on an iPhone at : Tech and Simple – A working Mobile VoIP solution for the iPhone – Acrobits Groundwire and Flowroute).On the other hand, Bria’s user interface is a bit simpler and marginally more user friendly than Groundwire’s.
The price of the two apps is in the same ballpark (less than $10), and you can’t go wrong with any of them.
CallCentric and Flowroute
CallCentric and Flowroute have a very different approach. CallCentrix has a large catalog of services (they can provide you local phone numbers almost anywhere in the world), and their customer service is first class. But they’re not the cheapest, and stick to tried and tested solutions.
Flowroute, on the other hand, has a much smaller catalog, but is cheaper and has developed a standard solution well suited to mobile VoIP (they support G729 codecs and TCP natively). As an “amateur technologist” (I’m not a telecom engineer by any means), I struggled a bit with the configuration pages of Flowroute’s Web site.
One last word
All the carriers are currently deploying LTE networks (aka 4G networks). LTE networks are data only networks, and they don’t offer any mechanism to transport voice conversations using conventional multiplexing technologies such as CDMA and GSM. That’s why most of the LTE capable smartphones sold by Verizon and Sprint have two radios (one for CDMA, one for LTE), and that’s why the iPhone 5, with only one radio, can not support simultaneous voice and data connections on their networks.*
The long term plan of the carriers is to shut down their old multiplexed voice networks, and to transport packetized voice as any other data payload on their new LTE networks. Metro PCS will be the first one to deploy VoIP over LTE (at the end of 2013, or so they say).
Considering the coverage and battery life issues I experienced when trying to use the current 3G data networks to transport voice, I’m not sure I would rush to be an early adopter.
* ATT’s implementation of its 3G network is different from Verizon’s or Sprint’s, and the same 3G connection can support conventional voice and data simultaneously. But like any other LTE network, ATT’s 4G network only supports data connections. It explains why an ATT LTE iPhone (with only one radio, as we have seen), falls back to 3G for data and for voice as soon as the user wants to talk and surf at the same time.