iPhone data connection types

Just curious — could anyone explain the exact meaning of all the connection type symbols in iPhone?

Let's see, wifi and 3G, the fastest connection types, are quite clear, but how about the others: E is probably for EDGE (aka EGPRS), but what does the circle (O) mean? (2G something? GPRS? Or is the latter a higher-level concept in mobile data transfer?) EDGE is presumably the better of these two? (In practice I haven't noticed great difference as both are much slower than 3G.)

Finally, how do UMTS or W-CDMA fit in this picture? And if EDGE is a 3G technology too (as stated in Wikipedia), what kind of 3G technology exactly does iPhone's "3G" refer to? (Also, please correct me if there are more than the four types I could remember.)

Solution 1:

On GSM (All but Verizon/Sprint):

• 4G = LTE (or HSPA+ on AT&T)
• 3G = UTMS/HSDPA
• E = EDGE
• o = GPRS

On CDMA (Verizon or Sprint in the USA):

• 4G = LTE
• 3G = EV-DO
• E = no equivalent - not possible
• o = 1xRTT