The MEID was created to replace electronic serial numbers (ESNs), whose virgin form was exhausted in November 2008.
GSM phones do not have ESN or MIN, only an International Mobile Station Equipment Identity (IMEI) number.
[3] The separation between international mobile equipment identifiers (IMEIs) used by GSM/UMTS and MEIDs is based on the number ranges.
A check-digit can be calculated from the 18 digit result using the standard base 10 Luhn algorithm and appended to the end.
These will cause an extremely rare condition known as a 'collision' on a pure ESN-only network as the ESN is used for the calculation of the Public Long Code Mask (PLCM) used for communication with the base-station.
Two mobiles using the same pESN within the same base-station area (operating on the same frequency) can result in call setup and page failures.
[4] Roughly, it is estimated that even on a heavily loaded network the frequency of this situation is closer to 1 out of 1 million calls than to 1 out of 100 000.
3GPP2 specifications C.S0016 (Revision C or higher) and C.S0066 have been modified to allow the replacement MEID identifier to be transmitted, resolving this problem.