ESN (Electronic Serial Number)

An ESN is a numeric identifier that uniquely identifies a CDMA phone in the United States. The ESN can typically be found written underneath a phone's battery and is generally written in both decimal and hexadecimal versions. The ESN is what a CDMA network uses to identify a phone and determine which subscriber's account, if any, it is linked to. Because of this, when switching from one phone to another, subscribers will have to provide the ESN of the new phone to the network carrier before it can be activated. This can often be done at the carrier's website. The ESN is slowly being phased out in favor of the MEID, a longer number that is compatible with the IMEI system used in GSM and UMTS phones. This is happening because phone manufacturers are literally running out of ESN identifiers.

EDGE (Enhanced Data for Global Evolution)

EDGE is a data system used on top of GSM networks that provides faster data speeds than GPRS, the technology it makes obsolete. It has a theoretical maximum downlink data rate of nearly 475Kbps, which qualifies it as a 3G technology based on ITU guidelines, even if typical implementations are configured for non-3G speeds. Generally, it is referred to as 2.75G.

EV-DO

Commonly known simply as EV-DO, CDMA 1xEV-DO is a 3G technology add-on for CDMA networks that allows for theoretical download speeds as fast as 2.4576Mbps, though actual rates tend to be far slower. Originally known as CDMA Evolution Data Only, EV-DO is today generally regarded as standing for Evolution Data Optimized for what are likely marketing purposes. 1xEV-DV (Evolution Data Voice) is the technology that was originally destined to handle the future 3G voice and data needs of CDMA networks, but has failed to catch on in North America. Instead, 1xEV-DO Rev A has been developed, which allows for faster uplink speeds than the original EV-DO spec, which relies on the older, and much slower, 1xRTT system for uplink connections.