What's the difference between GSM, CDMA, WCDMA, EVDO, and LTE? How do they relate to the network icon labels? Which one is 3G? Which ones are E, H and H+?
After doing some research, I've reduced it down to this:
GSM and CDMA = 2G EDGE (E) = 2.5G WCDMA and EVDO = 3G HSPA (H) = 3.5G HSPA+ (H+) = 3.75G LTE = 4G
GSM and CDMA are competing technologies, as well as WCDMA and EVDO. Contrary to what you'd think, WCDMA is an evolution of GSM, while EVDO is an evolution of CDMA, which is why a carrier or device will support either GSM/WCDMA or CDMA/EVDO, but not CDMA/WCDMA or GSM/EVDO. EDGE is an enhancement of the GSM protocol, while HSPA/HSPA+ are enhancements of the WCDMA protocol.
I am by no means an expert on this. I had a bit of trouble finding any single source that gave a short, high-level rundown on the topic, so I figured I might as well share my findings. If I've made any errors, feel free to comment or suggest an edit.