Description
Paging Policy Differentiation (PPD) is a mechanism introduced in 5G System (5GS) to enable differentiated handling of paging procedures based on various policies. It operates within the Access and Mobility Management Function (AMF) in the 5G core network, which is responsible for initiating paging when downlink data or signaling arrives for a UE in idle or inactive mode. PPD allows the AMF to select from multiple paging strategies, each defined by a set of configurable parameters, to optimize performance for specific scenarios.
How it works begins with the AMF receiving a downlink data notification from the User Plane Function (UPF) or a signaling request from another network function. The AMF evaluates attributes such as the Data Network Name (DNN), Single-Network Slice Selection Assistance Information (S-NSSAI), QoS Flow characteristics, or UE subscription data to determine an appropriate paging policy. Policies can dictate variations in the paging area scope (e.g., cell, tracking area list, or entire registration area), the number of paging attempts, the time interval between retries, and the use of priority indicators. For instance, a policy for ultra-reliable low-latency communication (URLLC) might trigger paging across a smaller area with more rapid retries, while a policy for massive IoT might use wider areas with fewer attempts to conserve signaling.
Key components include the Paging Policy Indicator (PPI), which can be signaled between network functions to convey the chosen policy, and the N1/N2 interface procedures that carry paging messages to the Next-Generation Node B (gNB). The architecture integrates with Network Slicing, as different slices may have distinct paging policies aligned with their service level agreements. The AMF uses local configuration or policy control function (PCF) guidance to map service requirements to paging parameters. Additionally, PPD can interact with RAN-based paging optimization in inactive mode, where the RAN may store UE context and assist in location-aware paging.
Its role is to make paging in 5G more intelligent and efficient compared to the one-size-fits-all approach of previous generations. By differentiating policies, the network can balance conflicting objectives: minimizing paging signaling load to reduce congestion, maximizing paging success probability to meet latency targets, and conserving UE battery life. This is especially critical in 5G's diverse deployment scenarios, which range from enhanced mobile broadband with dense user concentrations to industrial IoT with massive device counts. PPD thus contributes to the overall scalability and service-aware operation of the 5G core network.
Purpose & Motivation
PPD was created to address the limitations of uniform paging mechanisms in LTE, which could not efficiently accommodate the wide variety of services and requirements envisioned for 5G. In 4G, paging parameters were largely static or based on simple UE categories, leading to suboptimal performance for extreme use cases like massive machine-type communications or mission-critical services. The one-size-fits-all approach resulted either in excessive signaling overhead or inadequate reliability for certain applications.
It solves the problem of inefficient resource usage during mobility management for heterogeneous services. For example, paging a massive IoT device with the same urgency as a voice call wastes network resources, while paging an autonomous vehicle with the same laxity as a sensor could cause dangerous delays. PPD introduces granular control, allowing the network to tailor paging behavior to the specific needs of each service type, slice, or QoS flow. This optimization reduces core and RAN signaling load, which is vital for supporting the predicted scale of 5G connections.
The motivation stems from 5G's key design principles: service-based architecture and network slicing. As 5G aims to serve vertical industries with stringent and varied requirements, the core network must treat different traffic classes distinctly. PPD provides the tools to implement this differentiation in the paging domain, a fundamental mobility procedure. Historical context includes the evolution from basic paging in 2G/3G to slightly enhanced paging in LTE with features like paging prioritization, but 5G's PPD represents a systematic, policy-driven framework. It enables operators to deploy customized paging strategies that align with business policies, regulatory requirements, and technical constraints, thereby enhancing overall network efficiency and user experience.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (114 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, Paging Policy Differentiation (PPD) was introduced to enable the AMF to control which messages trigger paging, including support for SUPI-based paging. This function allows for differentiated paging strategies, such as providing paging cause indications for services like voice to assist the RAN. The mechanisms were further refined through updates and corrections to ensure proper handling within the 5G system's paging procedures.
- Architectural solution for User Plane (UP) Security policy and User Plane Integrity Protection TS 23.501CR0066
- Correction to rejected S-NSSAI TS 23.501CR0007
- Paging Policy Differentiation correction TS 23.501CR0013
- Correction to handling of S-NSSAI mapping information TS 23.501CR0020
- Control of the Messages triggering Paging at AMF TS 23.501CR0033
- Update Paging Policy Differentiation TS 23.501CR0036
+ 18 more changes
In Release 16, the Paging Policy Differentiation function was introduced, enabling QoS-based differentiation for paging procedures. This enhancement allowed the network to apply different paging strategies, such as using distinct DRX or eDRX values, based on policy control for services like voice or other prioritized applications. The mechanism assists the RAN in performing more efficient, service-aware paging when the UE is in the RRC_INACTIVE state.
- Introduction of inter-UE QoS differentiation for NB-IoT using NB-IoT UE Priority TS 23.501CR0892
- 23.501 part of PCF selection for PDU sessions with same DNN and S-NSSAI TS 23.501CR1375
- QoS differentiation for access to SNPN (PLMN) services via PLMN (SNPN) TS 23.501CR1264
- Clarification on S-NSSAI(s) for PDU session TS 23.501CR1548
- PCF selection for multiple PDU Sessions to the same DNN and S-NSSAI TS 23.501CR1743
- Applicability of UP Security Policy to a MA PDU Session TS 23.501CR1924
+ 9 more changes
In Release 17, the Paging Policy Differentiation (PPD) function was enhanced by introducing a Paging Cause Indication for Voice Service to assist the NG-RAN in performing RAN-based paging. This release also added support for paging reception for 5GS and provided clarifications on paging restrictions, particularly during mobility events like Registration Updates outside the current Registration Area. Furthermore, updates were made to enable paging for extended idle mode DRX in E-UTRA and NR connected to 5GC.
- Introduction of Paging Cause feature TS 23.501CR2574
- Support multiple NSACFs for one S-NSSAI during UE mobility TS 23.501CR2909
- Support RedCap UEs differentiation in 5GC TS 23.501CR3155
- Support for Paging Early Indication TS 23.501CR3319
- Allowing usage of S-NSSAI and Network Instance for internal UPF resource allocation TS 23.501CR3010
- NSSAAF Discovery and Selection based on S-NSSAI or UE ID Range TS 23.501CR3172
+ 19 more changes
In Release 18, the PPD function was enhanced to improve paging during satellite discontinuous coverage, ensuring reliable UE reachability in non-terrestrial networks. Furthermore, clarifications and updates were made to policy control enhancements for supporting multi-modal services, which influence network access and service authorization. These refinements build upon the existing framework where paging for a UE in CM-CONNECTED with RRC_INACTIVE state is managed by the RAN with core network assistance.
- N3IWF selection enhancement for support of S-NSSAI needed by UE TS 23.501CR3707
- Policy control enhancements to support multi-modal flows TS 23.501CR3864
- PIN policy configuration TS 23.501CR3898
- TNGF selection enhancement for support of S-NSSAI needed by UE TS 23.501CR3953
- Paging enhancement during satellite discontinuous coverage TS 23.501CR3966
- Allowing UE to simultaneously send data to different groups with different QoS policy TS 23.501CR3986
+ 27 more changes
In Release 19, Paging Policy Differentiation (PPD) was enhanced by introducing UE radio capability for paging handling, which provides the network with additional information to optimize paging strategies. Furthermore, corrections and clarifications were made to RAN paging priority mechanisms to ensure proper differentiation. These updates build upon the existing framework where paging for a UE in CM-CONNECTED with RRC_INACTIVE state is managed by the RAN using assistance information from the core network.
- Local Offloading Policy provisioning TS 23.501CR5463
- Exposure enhancements for static UE IP address assignment and 5G VN group's User Plane Security Policy TS 23.501CR5492
- KI#2: UE subscription and policy control for energy efficiency and energy saving TS 23.501CR5739
- S-NSSAI selection while in EPS TS 23.501CR5866
- Support for S-NSSAI granularity energy consumption exposure TS 23.501CR5956
- MPS for Messaging RAN Paging for SMS over NAS TS 23.501CR5834
+ 9 more changes
In Release 20, the Paging Policy Differentiation (PPD) function was enhanced to support network energy saving through policy control. This involved updates to the architecture and the Exposure and Integration Function (EIF) to enable energy consumption information exposure. These changes allowed for policy control mechanisms to influence paging and access control as part of the system's network access control functionality.
Explore further
Broader topics and technologies where PPD plays a role.
Defining Specifications
3GPP specifications that define or reference PPD, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |