IP address is very simple thing, but!

Hey mates,
I've some concerns about IP address in LTE. I've read 3GPP spec (quite boring, isn't it?) and found different overviews of IP address allocation process on the Internet.
So, IP address is allocated by P-GW along with default bearear. This is well known statement.
But - who knows, how IP address is actually allocated? DHCP? Based on IMEI thru HSS?

I will answer this question here later, but you have an opportunity to be the first.