Wired article and the VoIP over WiFi question

Yesterday Wired published a great article by Lizzie Wade, entitled Where Cellular Networks Don’t Exist, People Are Building Their Own, on the groundbreaking work being done by Rhizomatica to bring community-owned cellular networks to rural Mexico. This is highly recommended reading, even for those who are already familiar with Rhizomatica’s work and open source mobile networks. The comments the article has already attracted going to underline the level of interest and the opportunity at hand.

Speaking of comments, a question that came up — and which we frequently get asked! — is, why not just use VoIP over WiFi? After all, most handsets tend to have WiFi, are capable of running a SIP client and this would seem like an obvious solution.  Well, there are numerous reasons why such an approach is far from optimal:

  • WiFi is typically short range. Sure, you can achieve longer distances with high gain antennas and powerful equipment at both ends of a link, but this is impractical for mobile. However, Fairwaves GSM solutions can cover a range of 2-4km now, and 10km will soon be possible.
  • Commodity WiFi equipment simply isn’t designed for applications such as this and — due to using weak CPUs which can only sustain low packet per second rates — will only be able to support a relatively low number of calls reliably. GSM on the other hand is designed from the outset for voice, scaling and reliability.
  • GSM consumes far less power. Remember how a handset without a touchscreen, apps and data would last for a week on a single charge? Well, it’s possible to achieve multiple days on a modern handset if you put it into GSM-only mode and disable data. Turn on WiFi and it’s a whole other story!
  • Finally, in many countries you need a spectrum licence in order to operate outdoor WiFi networks.

So, as you can see, GSM certainly makes more sense than VoIP+WiFi for mobile voice, and even more so in rural areas where power supply may be a relatively scarce/premium resource and the greater distances that can be covered by a single site the better. In fact, for the very same reasons, in such applications GSM is typically preferable to more modern, albeit more power hungry and shorter range, 3G and 4G systems.

In closing it should be noted that there are applications where VoIP+ WiFi is the right solution. Such as rural fixed telecoms, as championed by the good folks at Village Telco. A mention should also go to the Serval Project, whose WiFi mesh network-based approach is well suited to use in support of disaster relief efforts.