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.

LTE CSFB Performance in a live network part 2

A while back I made a post about the performance of CSFB in a live network. Even though it was quite insightful it only captured a single CSFB procedure so from a statistical point of view the performance impact of the call setup delay was not that valid.

Recently Ericsson and Qualcomm produced a paper which summarises their findings from multiple tests and I have presented the most relevant table above. The multiple columns represent the performance impact of the different "flavours" of CSFB. As the implementation becomes more complex (from right to left) the call setup delay is reduced.

The basic impementation is what was initially conceived in the standards in 3GPP rel8. In order to save some time when the UE is redirected to UMTS, it can skip reading some SIBs. This can be either a proprietary implementation or some 3GPP rel7 fucntionality can be used which allows the UE to skip some SIBs and inform the network about it, which can then send the relevant information in connected mode.

SI Tunnel, specified in rel9, allows for the SIBs to be sent to the UE while still in LTE as part of the RRC Release with redirection message.

Finally a handover can also take place which will keep the UE in dedicated mode and allow for the fastest call setup.

In my opinion I think the SI Tunnel approach will be the mainstream solution as it offers a good balance of performance Vs complexity.

Interesting enough looking at the CSFB log I posted previously here, we can see that in this occasion the UE actually used some proprietary SIB skipping fuctionality as some SIBs such as SIB11 and SIB5 were not read by the UE. As SIB5 is mandatory for initiall access I can only assume that the UE had previously camped on that particular cell and had stored the SIB5 and SIB11 in memory.

The full paper that contains a lot more interesting information can be found here.

It is not about the subscribers, but still..

A while back network operators realised that using the number of subscribers as a measure of success was not the best thing to do. Much more important was how much they were spending a.k.a. ARPU. However in my opinion the number of subscribers is still a very interesting metric.

So for this post, I looked at the various 2012 Q1 results UK operators publish and compiled the graph above. So in first place is Everything Everywhere which is the joint venture of T-Mobile and Orange in the UK. With 27.2 millions subscribers it is easily in the lead but interesting enough, when first formed back in 2010 they had 29.5 million subscribers. In second place is O2 UK with 23.3 million, which back in 2007 landed the exclusivity of the iPhone and did quite well out of it (it is not in place anymore). Vodafone is third with a round 19 million followed in last place by 3 with 8.2 million.

3's figure is actually quite impressive considering they were the last entrant in the market and operate a 3G network only. 3's operational statement list another very interesting fact which is that 30% of their subscribers are mobile broadband dongles.

In 3's blog they actually posted that 97% of their traffic was data. Considering the number of dongles that is not surprise.

Finally, one last thing to consider is that the UK population is just under 65 million. The grand total of subscribers across all operators is 77.7 million! That just shows the popularity and level of saturation that mobile telephony has.

I too play my small part by having a SIM from each operator. But that is for research of course :)

Sources
Everything Everywhere here
O2 UK here
Vodafone UK here
3 UK here