Electronic Serial Number
Encyclopedia
Electronic serial numbers (ESNs) were created by the U.S. Federal Communications Commission
(FCC) to uniquely identify mobile devices, from the days of AMPS
in the United States from the early 1980s. The administrative role was taken over by the Telecommunications Industry Association
in 1997 and is still maintained by them. ESNs are mainly used with CDMA phones (and were previously used by AMPS
and TDMA
phones), compared to International Mobile Equipment Identity
(IMEI) numbers used by all GSM phones.
The first 8 bits of the ESN was originally the manufacturer code, leaving 24 bits for the manufacturer to assign up to 16,777,215 codes to mobiles. To allow more than 256 manufacturers to be identified the manufacturer code was extended to 14 bits, leaving 18 bits for the manufacturer to assign up to 262,144 codes. Manufacturer code 0x80 is reserved from assignment and is used instead as an 8-bit prefix for pseudo-ESNs (pESN). The remaining 24 bits are the least significant bits of the SHA-1 hash of a mobile equipment identifier (MEID). Pseudo-ESNs are not guaranteed to be unique (the MEID is the unique identifier if the phone has a pseudo-ESN).
ESNs are often represented as either 11-digit decimal numbers or 8 digit hexadecimal numbers. For the decimal format the first three digits are the decimal representation of the first 8 bits (between 000 and 255 inclusive) and the next 8 digits are derived from the remaining 24 bits and will be between 00000000 and 16777215 inclusive. The decimal format of pseudo ESNs will therefore begin with 128. The decimal format separately displays 8 bit manufacturer codes in the first 3 digits, but 14 bit codes are not displayed as separate digits. The hexadecimal format displays an ESN as 8 digits and also does not separately display 14 bit manufacturer codes which occupy 3.5 hexadecimal digits.
As ESNs have essentially run out, a new serial number format, MEID
, was created and was first implemented by Verizon in 2006. MEIDs are 56 bits long, the same length as the IMEI and, in fact, MEID was created to be a superset of IMEI. The main difference between MEID and IMEI is that the MEID allows hexadecimal digits while IMEI allows only decimal digits – "IMSI shall consist of decimal digits (0 through 9) only".
The last of the previously unused ESN codes were allocated in November 2008. Applications for assignments were accepted until June 30, 2010 using reclaimed ESN codes, those previously assigned to AMPS
or TDMA
phones and therefore not present on CDMA2000
systems. Reclaimed codes have also been used for UIMID
assignments. Codes are assigned according to industry guidelines.
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
(FCC) to uniquely identify mobile devices, from the days of AMPS
Advanced Mobile Phone System
Advanced Mobile Phone System was an analog mobile phone system standard developed by Bell Labs, and officially introduced in the Americas in 1983, Israel in 1986, and Australia in 1987. It was the primary analog mobile phone system in North America through the 1980s and into the 2000s...
in the United States from the early 1980s. The administrative role was taken over by the Telecommunications Industry Association
Telecommunications Industry Association
The Telecommunications Industry Association is accredited by the American National Standards Institute to develop voluntary, consensus-based industry standards for a wide variety of ICT products, and currently represents nearly 400 companies...
in 1997 and is still maintained by them. ESNs are mainly used with CDMA phones (and were previously used by AMPS
Advanced Mobile Phone System
Advanced Mobile Phone System was an analog mobile phone system standard developed by Bell Labs, and officially introduced in the Americas in 1983, Israel in 1986, and Australia in 1987. It was the primary analog mobile phone system in North America through the 1980s and into the 2000s...
and TDMA
Digital AMPS
IS-54 and IS-136 are second-generation mobile phone systems, known as Digital AMPS . It was once prevalent throughout the Americas, particularly in the United States and Canada. D-AMPS is considered end-of-life, and existing networks have mostly been replaced by GSM/GPRS or CDMA2000...
phones), compared to International Mobile Equipment Identity
International Mobile Equipment Identity
The International Mobile Equipment Identity or IMEI is a number, usually unique, to identify GSM, WCDMA, and iDEN mobile phones, as well as some satellite phones. It is usually found printed inside the battery compartment of the phone...
(IMEI) numbers used by all GSM phones.
The first 8 bits of the ESN was originally the manufacturer code, leaving 24 bits for the manufacturer to assign up to 16,777,215 codes to mobiles. To allow more than 256 manufacturers to be identified the manufacturer code was extended to 14 bits, leaving 18 bits for the manufacturer to assign up to 262,144 codes. Manufacturer code 0x80 is reserved from assignment and is used instead as an 8-bit prefix for pseudo-ESNs (pESN). The remaining 24 bits are the least significant bits of the SHA-1 hash of a mobile equipment identifier (MEID). Pseudo-ESNs are not guaranteed to be unique (the MEID is the unique identifier if the phone has a pseudo-ESN).
ESNs are often represented as either 11-digit decimal numbers or 8 digit hexadecimal numbers. For the decimal format the first three digits are the decimal representation of the first 8 bits (between 000 and 255 inclusive) and the next 8 digits are derived from the remaining 24 bits and will be between 00000000 and 16777215 inclusive. The decimal format of pseudo ESNs will therefore begin with 128. The decimal format separately displays 8 bit manufacturer codes in the first 3 digits, but 14 bit codes are not displayed as separate digits. The hexadecimal format displays an ESN as 8 digits and also does not separately display 14 bit manufacturer codes which occupy 3.5 hexadecimal digits.
As ESNs have essentially run out, a new serial number format, MEID
MEID
A mobile equipment identifier is a globally unique number identifying a physical piece of CDMA mobile station equipment. The number format is defined by the but in practical terms it can be seen as an IMEI but with hexadecimal digits....
, was created and was first implemented by Verizon in 2006. MEIDs are 56 bits long, the same length as the IMEI and, in fact, MEID was created to be a superset of IMEI. The main difference between MEID and IMEI is that the MEID allows hexadecimal digits while IMEI allows only decimal digits – "IMSI shall consist of decimal digits (0 through 9) only".
The last of the previously unused ESN codes were allocated in November 2008. Applications for assignments were accepted until June 30, 2010 using reclaimed ESN codes, those previously assigned to AMPS
Advanced Mobile Phone System
Advanced Mobile Phone System was an analog mobile phone system standard developed by Bell Labs, and officially introduced in the Americas in 1983, Israel in 1986, and Australia in 1987. It was the primary analog mobile phone system in North America through the 1980s and into the 2000s...
or TDMA
Digital AMPS
IS-54 and IS-136 are second-generation mobile phone systems, known as Digital AMPS . It was once prevalent throughout the Americas, particularly in the United States and Canada. D-AMPS is considered end-of-life, and existing networks have mostly been replaced by GSM/GPRS or CDMA2000...
phones and therefore not present on CDMA2000
CDMA2000
CDMA2000 is a family of 3G mobile technology standards, which use CDMA channel access, to send voice, data, and signaling data between mobile phones and cell sites. The set of standards includes: CDMA2000 1X, CDMA2000 EV-DO Rev. 0, CDMA2000 EV-DO Rev. A, and CDMA2000 EV-DO Rev. B...
systems. Reclaimed codes have also been used for UIMID
UIMID
A UIMID is a 32-bit Electronic Serial Number stored in a R-UIM or CSIM used for TDMA or CDMA2000 phones . It is given a different name to avoid confusion with the hardware ESN stored in the phone. In all known systems the UIMID displaces the ESN in signaling...
assignments. Codes are assigned according to industry guidelines.