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Glossary

IMSI (International Mobile Subscriber Identity) in 3GPP: meaning and where it is specified

Published 2026-10-16Updated 2026-10-16

At a glance

Term
IMSI
Stands for
International Mobile Subscriber Identity
Defined in
3GPP TR 21.905 V19.2.0, clause 4
Used in
TS 29.060, TS 29.274, TS 48.008

In plain words

IMSI means International Mobile Subscriber Identity, the term listed in 3GPP TR 21.905. TS 29.060 and TS 29.274 each use it in a clause titled International Mobile Subscriber Identity. TS 48.008 describes its coding this way: "The IMSI is coded as a sequence of BCD digits, compressed two into each octet."

Source: 3GPP TS 48.008 V19.0.0, clause 3.2.2.6. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: https://www.3gpp.org/ftp/Specs/archive/48_series/48.008/48008-j00.zip

Sources

  1. 3GPP TR 21.905 V19.2.0, clause 4. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: https://www.3gpp.org/ftp/Specs/archive/21_series/21.905/21905-j20.zip
  2. 3GPP TS 29.060 V19.0.0, clause 7.7.2. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: https://www.3gpp.org/ftp/Specs/archive/29_series/29.060/29060-j00.zip
  3. 3GPP TS 29.274 V19.6.0, clause 8.3. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: https://www.3gpp.org/ftp/Specs/archive/29_series/29.274/29274-j60.zip
  4. 3GPP TS 48.008 V19.0.0, clause 3.2.2.6. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: https://www.3gpp.org/ftp/Specs/archive/48_series/48.008/48008-j00.zip

How this page was made

The facts box comes straight from the 3GPP TDoc list and specification archive as indexed by 3GPP Scout. An AI model (GPT-6 Luna) wrote the paragraph and named the source of each sentence. Code checked every quote word for word against the stored source text and every number against the cited source. A second AI model from another company (Claude Opus 5.5) reviewed the paragraph against the same sources. The 3GPP documents themselves govern.