As I travel a lot I kept a close eye on falling roaming costs over the years. On the one hand every price reduction offsets increasing volume requirements due to the continuing increase of website and document sizes. On the other hand, additional data volume for the same price as before gives me additional autonomy from local Wifi access that is often patchy and slow and allows me to do new and more data intensive things even while not at home. When I was recently in Dubai, I was glad to notice that my mobile network operator of choice has increased the amount of data I can get for €25 from 500 MB back in December 2018 to 1 GB in January 2019. In both cases, the data bucket was valid for up to a week and additional packages could be bought when running out of data earlier.
This nice increase also allowed me to add one more thing to my list of services I use while roaming outside the EU: VoWifi over LTE.
Voice Telephony When Roaming Can Be A Pain
When roaming outside the EU there are two main issues when it comes to voice calls. First, voice calls when roaming in countries outside the EU are (still) charged at hilarious rates of several euros per minute. And secondly, more often than not, the sound quality leaves a lot to be desired. This is due to compression and other not so nice things being done to the digital speech packets on the roaming interconnect.
One way to improve things is to use VoWifi which, as the name implies needs a Wifi hotspot. As VoWifi establishes an IPSec tunnel to the ePDG gateway of the home network operator over the Internet, voice calls are then tunneled and thus can’t be touched by anything in between. Also, they are not charged as roaming calls but as home network calls. The catch is, of course, that a Wifi hotspot is needed which, at least as far as the design is concerned, connects to a fixed line Internet connection.
But what about opening a Wifi-hotspot on a smartphone that then backhauls the IP traffic over LTE!? On another phone, that Wifi hotspot can then be used for VoWifi. To the VoWifi client on the second smartphone it is totally transparent that the Wifi hotspot does not connect to a fixed line Internet link but rather to an Internet connection over LTE.
VoWifi over LTE in Practice
In practice this has worked rather well with the only downside having been the higher power consumption. I had the Wifi hotspot open 24/7 over several days on the smartphone on which I bought the 1 GB roaming data package. Incoming and outgoing calls over VoWifi over LTE from the second smartphone worked like a charm. And in addition to avoiding the several euros per minute roaming charges for voice calls, I didn’t only have standard voice quality but even WB-AMR to people back home who also had a phone that supported the better codec. So even if voice calls from abroad were cheap over normal roaming channels, this would still be an advantage of using VoWifi over LTE. And while some network operators block the use of VoWifi when the subscriber is outside the home country, mine doesn’t. Well done!