Anyone got this to work on 4G? This example only work for 2G last time I did the same.
3G will be turned off during 2019 to make room for 5G, thats why I only ask for 4G.
Since many networks don't actually have VoLTE fully implemented and working yet (and many popular Android handsets have quirks/bugs/issues around it, coupled with MNOs trying to "pitch" VoLTE as an exclusive feature when you buy the handset direct on their own MNO-modified firmware), a 2G catcher should still work in many scenarios. If 3G is switched off, that (ironically) means that many people's calls will end up going over original 2G networks, where the handset doesn't authenticate the network at all! 3G handsets at least do a mutual authentication of the network.
If you want to look at a real LTE catcher, take a look at this paper [1]. Worth noting this is not passive however, and requires transmitting in licensed spectrum, which defeats the point of this passive one.
East Asia is leading the way in regard to switching-off 2G networks. In certain countries in the region, such as Japan, Macau, Singapore and South Korea, there is no 2G available at all. In Taiwan and Thailand, the major network operators have already phased out 2G with some operators in those countries still offering 2G services for a limited time. https://www.emnify.com/blog/global-2g-phase-out
Active IMSI catchers abuse 2). At this stage of early connection setup, the network is not yet authenticated (the IMSI is required for the authentication). Therefore the smartphone must assume the IMSI request comes from the operator network -- and it cannot tell that it's actually a IMSI catcher.
Case 1) is obviously pretty rare, so it might be a bit boring to perform IMSI catching on 4G.