Apple announce FaceTime over 3G/LTE on iOS6

At the recent Apple WWDC it was announced that on iOS6 users will be able to use FaceTime over the cellular network. I should point out that this has been possible for a while with a jailbroken iPhone but in iOS6 it will be available as standard.

Now video calling has been possible in 3G since the beginning, but as most people know it never had much success. Some device manufacturers actually even removed the capability from the menu as years progressed. I guess the reasons for it failing were many, but for sure the quality aspect of it had a big impact. Video calls over 3G were handled by a circuit switched 64kbps connection and no matter how good the codecs, trying to send video and audio over that bandwidth just didn't work.

Things have obviously evolved since and now with HSPA(+) and LTE there is quite a lot a bandwidth over the air interface. But how much bandwidth does FaceTime require anyway? To find out I hooked up my iPhone to a Wi-Fi access point that I can monitor and produced the graph below.

The x axis shows bits, so on average the bandwidth utilisation is around 400kbps. I should point out that for this FaceTime call the background was mostly static. As you can see at the beginning of the call there was some movement and the utilisation exceeded 500kbps. This is due to the way video codecs work where only the delta between frames is sent (roughly speaking).

From an network operator point it will be interesting to see how the quality aspect of it is handled. Even though the air interface bandwidth with HSPA(+) and LTE is very high, it is still a shared medium, with mobility, fading, noise, etc which could make the user experience quite poor in some situations.

One approach could be to offer a best effort service (which almost all operators do for data at the moment) but another approach could be to offer some level of QoS. In 3G this could be through the use of a secondary PDP context that is mapped to a streaming type RAB. This would require some development from Apple's point of view as the device would have to request the secondary PDP context activation when the FaceTime app is initiated. In LTE things are simpler and the PCRF (Policy and Charging Rules Function) could detect the FaceTime call through deep packet inspection and request the establishment of a Dedicated EPS Bearer with a better QoS. These concepts are further described here.