PEI

Permanent Equipment Identifier

Identifier →
Introduced in Rel-15 Also in: Radio Access Network, Security

PEI is a globally unique, permanent identifier for 3GPP User Equipment, used for device identification, registration, security, and authentication.

Category
Identifier
Introduced
Rel-15
Where
Core Network › 5G Core
Also touches
2 segments
Specifications
26 specs
PEI Description Purpose Related Classification Detected Changes Specifications

Description

The Permanent Equipment Identifier (PEI) is a fundamental identifier within the 3GPP system, designed to uniquely and permanently identify the physical User Equipment (UE) hardware. It is defined as a separate entity from subscriber-based identities like the SUPI, ensuring a clear distinction between the device and the user. The PEI is provisioned into the UE's non-volatile memory during manufacturing and is intended to remain unchanged for the lifetime of the device, barring hardware replacement. Its primary architectural role is within the core network, specifically in interactions with the Access and Mobility Management Function (AMF) and the Unified Data Management (UDM) for registration and authentication procedures.

In operation, the PEI is used during initial network registration and authentication. For 5G systems, the PEI can be included in the Registration Request message sent from the UE to the AMF. The AMF may then use this identifier, particularly for UEs that do not have a Universal Subscriber Identity Module (USIM), to authenticate the device itself. The PEI is also a key parameter for network functions like the Equipment Identity Register (EIR), which uses it to check the device's status (e.g., blacklisted, grey-listed, or white-listed) to prevent the use of stolen or unauthorized devices on the network. This check helps in mitigating fraud and protecting network resources.

The identifier itself can take different forms depending on the device type. For traditional cellular devices, it is typically the International Mobile Equipment Identity (IMEI) or IMEISV. For IoT and other devices, it may be defined differently as per 3GPP specifications. The PEI is a critical element for security, management, and regulatory compliance. It supports functions such as device authentication for network access (especially for non-USIM based authentication in IoT scenarios), lawful interception mandates, and equipment theft deterrence. Its handling is governed by strict privacy and security specifications to prevent unauthorized tracking, with protocols ensuring it is not transmitted unnecessarily over the air.

Purpose & Motivation

The PEI was created to provide a standardized, permanent, and globally unique method for identifying telecommunications equipment independent of the subscriber. This solves several critical problems: it enables network operators to authenticate devices, not just subscribers, which is vital for IoT deployments and scenarios without USIMs. It addresses the issue of device theft and fraud by allowing networks to blacklist stolen devices via an Equipment Identity Register (EIR), preventing their use. Historically, before standardized permanent equipment identifiers, tracking stolen devices or managing device-specific access policies was inconsistent and less effective across different networks and regions.

Its introduction and formalization in 3GPP specifications, particularly from Release 15 onward with 5G, were motivated by the expanding Internet of Things (IoT) ecosystem and the need for more robust device management. IoT devices often use simplified authentication schemes or may not use a traditional SIM card, making a reliable device identifier essential for network security and access control. The PEI also fulfills regulatory requirements for lawful interception and equipment registration in many jurisdictions. It provides a stable anchor for network management functions, charging systems, and security protocols that need to correlate activities with a specific physical device over time.

Classification

Part ofIMEI
Related approachesSUPI

Detected Changes Across Releases

from 3GPP Change Requests

Specific changes extracted from the „Change history“ tables of 3GPP specifications (240 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.

Rel-15 56 changes

In Release 15, the PEI function was formally defined as the Permanent Equipment Identifier, with a key introduction being its specification in the IMEISV format. This release also established the SUPI (Subscription Permanent Identifier) as the core subscriber identity, which can take forms like an IMSI or a Network Access Identifier (NAI) for network-specific, global line, or global cable identifiers. Furthermore, Release 15 introduced the SUCI (Subscription Concealed Identifier) as a privacy-preserving, encrypted counterpart to the SUPI for secure initial network registration.

  • Clarification to Subscription identifier privacy TS 33.501CR0145
  • Use of identifiers for mobility between GERAN/UTRAN and 5GS TS 23.501CR0017
  • Partitioning of Identifier space to ensure success of Context retrieval for EPS Interworking TS 23.501CR0090
  • UDM Discovery with SUPI as input TS 23.501CR0091
  • Subscription Permanent Identifier TS 23.501CR0189
  • SUPI based paging TS 23.501CR0199

+ 50 more changes

Rel-16 69 changes

In Release 16, the PEI function was extended to support new device types, specifically the 5G-CRG and FN-CRG, as well as for UEs not supporting any 3GPP access technologies. The specification also provided clarifications on the PEI format and introduced the concept of an Untrusted FN-RG PEI. Furthermore, support for PEI was defined in the context of 5G Wireline Wireless Convergence (5WWC) scenarios.

  • SUPI and SUCI for wireline access TS 23.501CR0744
  • PEI for 5G-CRG and FN-CRG TS 24.501CR0937
  • Group Identifier Translation TS 29.503CR0281
  • External Group Identifier in NIDD information TS 29.503CR0330
  • SUPI pattern TS 29.503CR0353
  • Translation of Group Id to UE identifier list TS 29.503CR0366

+ 63 more changes

Rel-17 45 changes

In Release 17, key enhancements for the PEI function included specific handling for Multi-USIM (MUSIM) UEs to correctly associate the PEI with network subscriptions and support for UEs that do not support any 3GPP access technologies. These updates ensured proper identifier management in scenarios involving credential holders accessing Standalone Non-Public Networks (SNPNs) and clarified the use of PEI alongside other identifiers during PDU session establishment.

  • IMSI based SUPI support when access an SNPN using credentials owned by CH TS 23.501CR2919
  • Format of SUCI/SUPI used for Onboarding TS 23.501CR3097
  • Identifier Translation TS 29.503CR0654
  • Authorization of Group Identifier Translation TS 29.503CR0694
  • Group Identifier for Network Selection TS 23.003CR0636
  • Handling of SUPI/SUCI format when accessing to a SNPN TS 23.501CR3045

+ 39 more changes

Rel-18 26 changes

In Release 18, the PEI function was enhanced to enable a Remote UE to be identified by its PEI, and clarifications were added regarding the use of PEI for MUSIM UEs. Furthermore, the release included corrections and updates related to identifier handling in non-3GPP access, specifically for the N3IWF identifier received in REGISTRATION REJECT messages. These updates ensure proper equipment identification across new access scenarios and multi-SIM operations.

  • SNPN Identifier based N3IWF FQDN TS 23.003CR0687
  • Decorated NAI format for 5G-NSWO for SUPI TS 23.003CR0696
  • PIN identifiers TS 23.501CR4287
  • Remote UE identified by PEI TS 24.501CR5704
  • Protecting the N3IWF/TNGF identifier information in the REGISTRATION REJECT message TS 24.501CR5932
  • Add Identifier of SNPN for 5G data connectivity charging TS 32.255CR0418

+ 20 more changes

Rel-19 44 changes

In Release 19, the PEI function was enhanced to better support devices behind a UE or 5G-RG, including the definition of new identifiers like the AIoT Device Permanent Identifier for non-3GPP devices. It introduced capabilities for QoS differentiation and suspension based on these device identifiers, and enabled new procedures such as a GPSI/PEI-based ID Association Query. Furthermore, support was added for including PEI in monitoring event configurations and for reporting old PEI values in the Nudm_EE interface.

  • Non-3GPP Device Identifier TS 23.003CR0708
  • Definition of AIoT Device Permanent Identifier TS 23.003CR0713
  • UDR enhancement supporting Device Identifier of non-3GPP Devices connecting behind a UE/5G-RG TS 23.501CR5547
  • Definition of identifiers of N3GPP device behind UE/5G-RG TS 23.501CR5749
  • Support of reject QoS differentiation for non-3GPP device identifier(s) TS 24.501CR6926
  • Procedure update for QoS differentiation of non-3GPP device identifiers TS 24.501CR6994

+ 38 more changes

Explore further

Broader topics and technologies where PEI plays a role.

Topics
Authentication (5G-AKA, EAP)IMS & Voice (VoLTE, VoNR)Privacy (SUPI, SUCI)Policy & ChargingLawful InterceptIoT & MTC
Technologies
5G

Defining Specifications

3GPP specifications that define or reference PEI, with the latest known release. Sourced from the 3GPP document catalog — see methodology.

SpecificationTitleRelease
TS 23.003 vj50 Numbering, addressing and identification in 3GPP Rel-19
TS 23.501 vk00 5G System Architecture Stage 2 Rel-20
TS 24.501 vj50 5G NAS Protocols Specification Rel-19
TS 29.256 vj30 UAS-NF Stage 3 Protocol Specification Rel-19
TS 29.503 vj50 UDM Service Based Interface Stage 3 Rel-19
TS 29.507 vj40 5G Access & Mobility Policy Control Service Rel-19
TS 29.511 vj10 5G Equipment Identity Register Service Interface Rel-19
TS 29.514 vj40 5G System; Policy Authorization Service; Stage 3 Rel-19
TS 29.518 vj50 AMF Service Based Interface Protocol Rel-19
TS 29.525 vj40 5G UE Policy Control Service Stage 3 Rel-19
TS 29.571 vj50 Common Data Types for 5G Service Based Interfaces Rel-19
TS 29.890 vg00 CT3 5G System Technical Report Rel-16
TS 32.255 vk10 Telecom Management; Charging for 5G Data Connectivity Rel-20
TS 32.256 vj40 5G Connection & Mobility Charging Spec Rel-19
TS 32.291 vj40 Charging Management: Service-Based Interface Protocol Rel-19
TS 33.126 vj30 Lawful Interception Requirements Rel-19
TS 33.127 vj50 Lawful Interception Architecture and Functions Rel-19
TS 33.501 vk00 5G Security Architecture and Procedures Rel-20
TR 33.857 vh10 Enhanced Security for Non-Public Networks Rel-17
TS 38.300 vj00 NG-RAN Overall Description Rel-19
TS 38.304 vj00 UE RRC_IDLE and RRC_INACTIVE Procedures Rel-19
TS 38.331 vj00 NR Radio Resource Control (RRC) Protocol Specification Rel-19
TS 38.410 vj10 NG Interface Introduction for NG-RAN to 5GC Rel-19
TS 38.470 vj10 F1 Interface Introduction Rel-19
TS 38.523 vj20 5G NR UE Conformance Testing: Idle/Inactive Rel-19
TR 38.869 vi00 Study on low-power wake up signal and receiver for NR Rel-18