I want to develop a 2G, 3G or 4G driver for RIOT.
I have worked before with a Gemalto BGS2T serial modem (2G only) for IoT applications, and worked fine.
Here is the datasheet: http://www.activexperts.com/files/manuals/cinterion-bgs2t-rs232-datasheet.pdf
What do you think about it? Do you know another 2G, 3G or 4G that coudl work better?