Friday 27 June 2014

Voice over WiFi (VoWiFi)

One of the changes that I have noticed in the last year is that some of the operators who have been opposed to WiFi in the past have not only embraced it but are now trying to monopolise the same WiFi spectrum they billed as interference prone. Personally, I think the future of Wi-Fi is not just offloading but also working together with LTE. We are billing this as 4.5G and have recently produced a whitepaper, available here.

There has been a flurry of activity on Voice over Wi-Fi in the last few months. Recently the UK operators '3' and EE announced that they are both allowing WiFi calling and SMS. While '3' customers will have to use an OTT app for the time being, EE customers will experience this seamlessly.

I heard Taqua in the recent LTE World Summit talking about their solution and have offered to share their slides (embedded below). It was interesting to find out while having a discussion with them that their solution supports 'hand-in' and 'hand-out'. This takes away a major advantage that Small Cells offered, seamless roaming. Anyway, feel free to let me know of you have any opinion on this topic


viande_de_chat said...

How works VoWiFi for an operator which has implemented S2a? The Handset is authenticated (EAP-SIM) and its packets are already routed in the P-Gw. In this case an additional IPSec tunnel is not required. But I don't think that the Handset is able to detect that he is connected to the P-Gw over S2a. In case of VoWifi, the handset will still initiate the IPSec tunnel and the operator has to enhance its TWAG with an IPSec Gw. Is that correct?

Colin said...

For VoWiFi the IPSec tunnel is best established for voice specifically (hence it wouldn't carry other data traffic). Carriers that already have deployed a Carrier WiFi solution (with S2a support), maybe able to enhance its TWAG with ePDG functionality.
However, note that the requirements for mobile (internet) data and VoWiFi are quite different in terms of performance, throughput capacity and, latency and packet loss varaibility.

Anonymous said...

slide 13 mentions support for regulatory feature. Could you expend a bit on this when a terminal has only wifi coverage. Thinking about 911 calls handling in T-Mobile network for instance

Anonymous said...

For VoWifi , IMS REGISTER should be sent over the established IPsec tunnel.
How a transport mode protected IMS REGISTER will be sent through tunnel mode (IPsec).
Can anyone please help or provide a rfc reference.