A unique International Mobile Subscription Identity (IMSI) shall be allocated to each mobile subscriber in the GSM/UMTS/EPS system.
: This IMSI is the concept referred to by ITU-T as "International Mobile Subscription Identity".
In order to support the subscriber identity confidentiality service the VLRs, SGSNs and MME may allocate Temporary Mobile Subscriber Identities (TMSI) to visiting mobile subscribers. The VLR, SGSN and MME must be capable of correlating an allocated TMSI with the IMSI of the MS to which it is allocated.
An MS may be allocated three TMSIs, one for services provided through the MSC, one for services provided through
the SGSN (P-TMSI for short) and one for the services provided via the MME (M-TMSI part GUTI for short).
For addressing on resources used for GPRS, a Temporary Logical Link Identity (TLLI) is used. The TLLI to use is built
by the MS either on the basis of the P-TMSI (local or foreign TLLI), or directly (random TLLI).
In order to speed up the search for subscriber data in the VLR a supplementary Local Mobile Station Identity (LMSI) is
The LMSI may be allocated by the VLR at location updating and is sent to the HLR together with the IMSI. The HLR
makes no use of it but includes it together with the IMSI in all messages sent to the VLR concerning that MS.
IMSI is composed of three parts:
Mobile Country Code (MCC) consisting of three digits. The MCC identifies uniquely the country of domicile of
the mobile subscription;
Mobile Network Code (MNC) consisting of two or three digits for 3GPP network applications. The MNC
identifies the home PLMN of the mobile subscription. The length of the MNC (two or three digits) depends on
the value of the MCC. A mixture of two and three digit MNC codes within a single MCC area is not
recommended and is outside the scope of this specification.
Mobile Subscriber Identification Number (MSIN) identifying the mobile subscription within a PLMN.
The SUPI is a globally unique 5G Subscription Permanent Identifier allocated to each subscriber in the 5G System. It is
defined in clause 5.9.2 of TS 23.501
The SUPI is defined as:
a SUPI type: in this release of the specification, it may indicate an IMSI or a network specific identifier; and
dependent on the value of the SUPI type:
an IMSI as defined in clause 2.1;
a network specific identifier, taking the form of a Network Access Identifier (NAI) as defined in clause 28.7.2;
for an FN-CRG a Global Cable Identifier (GCI) which includes the HFC Identifier and an operator identifier, as defined in clause 28.15.2;
for an FN-BRG a Global Line Identifier (GLI) which includes a Line Id and an operator identifier, as defined in clause 28.16.2.
: Depending on the protocol used to convey the SUPI, the SUPI type can take different formats.
The SUCI is a privacy preserving identifier containing the concealed SUPI. It is defined in clause 6.12.2 of TS 33.501
The SUCI is composed of the following parts:
SUPI Type, consisting in a value in the range 0 to 7. It identifies the type of the SUPI concealed in the SUCI.
The following values are defined:
1: Network Specific Identifier
2 to 7: spare values for future use.
Home Network Identifier, identifying the home network of the subscriber.
When the SUPI Type is an IMSI, the Home Network Identifier is composed of two parts:
When the SUPI type is a Network Specific Identifier, the Home Network Identifier consists of a string of
characters with a variable length representing a domain name as specified in clause 2.2 of RFC 7542.
Mobile Country Code (MCC), consisting of three decimal digits. The MCC identifies uniquely the country of
domicile of the mobile subscription;
Mobile Network Code (MNC), consisting of two or three decimal digits. The MNC identifies the home
PLMN of the mobile subscription.
Routing Indicator, consisting of 1 to 4 decimal digits assigned by the home network operator and provisioned in
the USIM, that allow together with the Home Network Identifier to route network signalling with SUCI to AUSF
and UDM instances capable to serve the subscriber.
Each decimal digit present in the Routing Indicator shall be regarded as meaningful (e.g. value "012" is not the
same as value "12"). If no Routing Indicator is configured on the USIM, this data field shall be set to the value 0
(i.e. only consist of one decimal digit of "0").
Protection Scheme Identifier, consisting in a value in the range of 0 to 15 (see Annex C.1 of TS 33.501). It represents the null scheme or a non-null scheme specified in Annex C of
TS 33.501 or a protection scheme specified by the HPLMN;
Home Network Public Key Identifier, consisting in a value in the range 0 to 255. It represents a public key
provisioned by the HPLMN and it is used to identify the key used for SUPI protection. This data field shall be
set to the value 0 if and only if null protection scheme is used;
Scheme Output, consisting of a string of characters with a variable length or hexadecimal digits, dependent on
the used protection scheme, as defined below. It represents the output of a public key protection scheme
specified in Annex C of
TS 33.501 or the output of a protection scheme specified by the HPLMN.