Trying to wrap my head around mobile tech and the various protocols involved. After some quick research, this is what I’ve learned:
GSMGSM is a 2G network spec that does calls and text, but doesn't (nicely?) support data transfer. You can add data capabilities to a GSM network with GPRS or EDGE.
UMTSUMTS is an incompatible evolution of GSM which supports calls, text, and data. The initial release (R99/Release 1999) supports data transfer speeds of up to 384 kbit/s.
HSPA can be added to a UMTS network to acheive much faster, and eventually 4G download speeds.
CDMAMeanwhile, CDMA networks are still popular in North America and have evolved to 3G speeds with progressive upgrades (CDMA One, CDMA 2000, and now . For the most part CDMA phones don't require SIM cards and are not compatible with 3G networks. I don't know how these phones are registered onto the network.
UMTS actually uses the underlying concepts of CDMA to operate, but when referring to simply "CDMA" people are generally talking about the trade name rather than the technique.
LTE and 4GLTE is a data-only network based on, but incompatible with UMTS which provides 4G speeds of nearly 300 mbit/s down. As it's a packet network, traditional voice calls can't be placed (without carriers re-engineering their network) so phones either use VoIP or fall back to the next available network to talk. LTE is slated to be the first global mobile network, as even CDMA carriers are reportedly implementing it.
I think that just about covers it.