Here are my 5 cents reasons:
1. Mobile VoIP is (Still) Downloadable
Mobile VoIP is yet to be embedded as part of the natural user experience of a mobile phone. There are some handsets that support mobile VoIP, but finding it, configuring it and using it is way harder than simply calling someone.
In most cases, the only way to use mobile VoIP is to download a third party application to the phone. The need to download an application for daily communications is something that most users won’t accept. And from the developer’s perspective, the need to develop a specialized application for every other handset out there is a real hassle.
And if you think that the “millions of users” who are already using mobile VoIP are a movement, think again: there are 4.3 billion mobile subscribers worldwide today. A few millions is a drop in the water, nothing more.
2. Mobile VoIP by Whom?
Decided to use mobile VoIP? Great! But which one?
Skype? Google Voice? Want to use Fring for your calls? Or maybe their arch rival Nimbuzz?
And there are dozen others that I will not bother to mention here.
Mobile VoIP client vendors vary widely in offering, user interface and quality of experience. Not to say in the “coverage” of the people you can contact using it.
The bottom line is that if you want to use Mobile VoIP today, really use (as an alternative to the “plain old” mobile calls), you’ll probably need more than a single client, switching between clients depending on whom you want to contact.
3. Mobile VoIP – On What Network?
Mobile VoIP can use either a WiFi connection or any network using its data connection (3G, for instance).
Today’s mobile networks are already quite optimized when it comes to their bandwidth use. They are based on the old faithful circuit switching technology, where a “channel” is reserved for the call over the network and used only for the call itself. This allows reducing the overhead on top of the actual voice data to a bare minimum. It also what makes it way more bandwidth-optimized than mobile VoIP.
This means that carriers have no incentive to move to a VoIP network, as it may require more bandwidth per call on their side (and bandwidth is scarce). It also means that carriers will do what they can to reduce the number of people using Mobile VoIP on their networks (tweaking data network latency and packet loss, forcing people to download the applications, not approving VoIP applications into their specialized app stores, etc).
So Mobile VoIP is left with WiFi, where coverage is getting better every year, but it sure isn’t as robust as the cellular network is. WiFi also requires a roaming service of some kind, making it a hassle of checking each time which WiFi network exists in the vicinity and trying to connect to one that you can actually work with.
4. Voice Quality
Circuit switched mobile calling takes care of voice quality simply by guaranteeing bandwidth end-to-end. It is also what cellular networks were built and optimized for – passing voice calls. Data came later.
And data didn’t take voice calling into account. As Mobile VoIP is sensitive to packet loss and latency, it is not suitable for the 3G data networks it rides upon (and its suitability for WiFi access points can also be questioned). This is why, in a lot of cases, and with a lot of the different mobile VoIP applications out there, voice quality won’t be as good as that of regular mobile calls.
5. Battery Life
Mobile VoIP requires that the data connection will remain open at all times. This is because it has to “listen in” on what goes on over the IP network, “trying” to catch packets that are routed to it. It is the case even when you are not participating in a call.
Why is that an issue? Because baseband chips in mobile handsets today are optimized for circuit switching – up to the point of reducing their power requirements on standby mode. But standby mode in most handsets (or all that I know of, at least) don’t allow for having an open data channel (or WiFi connection), listening in on IP packets.
So if you want to go all-Mobile VoIP, expect to recharge your battery more than once a day. Not that usable. Or green.
If this seems to you that I am against mobile VoIP then you are wrong. All of these issues will be fixed. All that is needed is enough time to improve the networks and the technologies that are used by mobile VoIP.
For now though, Mobile VoIP gets a resounding #FAIL.