Translation of RIL_PreferredNetworkType terminology to human speak?
I figured them out thanks to here and here.


GSM is 2G (on GSM networks)
WCDMA is 3G (HSPA)
CDMA is 2G (on CDMA networks)
EvDo is 3G (on CDMA networks)
TD-SCDMA is 3G (UMTS)
LTE is 4G (LTE)


This PDF (page 16) explains the evolution of the different technologies.

Warning: A lot of this terminology is conflated (e.g. "CDMA" can refer to both the channel access method as well as mobile phone standards, "3G" and "4G" can refer to lots of different things, etc.) so take these with a grain of salt.