Description
Uplink Data Compression (UDC) is a performance-enhancing feature in 3GPP LTE and 5G NR that operates at the Packet Data Convergence Protocol (PDCP) layer. Its primary function is to apply lossless compression algorithms to user plane data packets in the uplink direction (from User Equipment to the base station) before they are ciphered and transmitted over the radio interface. The process involves the UE compressing IP packets (including headers and payload) and the receiving network node (eNodeB/gNB) decompressing them. The compression context is established and synchronized between the UE and the network during radio bearer setup or reconfiguration.
Architecturally, UDC is integrated into the PDCP entity for a specific data radio bearer. When configured by the network via RRC signaling, the UE's PDCP layer applies a compression algorithm (e.g., based on Robust Header Compression (ROHC) principles or dedicated UDC algorithms) to the incoming IP packets from higher layers. The compressed packet, along with necessary control information, is then processed through standard PDCP functions like ciphering and adding a PDCP header before being passed to the RLC layer. The gNB performs the inverse operation. The feature requires robust error recovery mechanisms to handle packet loss without causing de-synchronization of the compression context.
UDC plays a crucial role in optimizing radio resource utilization. By reducing the size of uplink transmissions, it decreases the amount of physical layer resources (time/frequency blocks) required, which directly translates to improved cell capacity and user throughput. It is especially effective for applications with repetitive data patterns, such as messaging, IoT sensor reports, or certain web protocols. The feature is managed by the RAN and can be dynamically controlled per UE and per bearer based on network policy and observed traffic characteristics.
Purpose & Motivation
UDC was created to address the growing asymmetry in cellular data traffic and the specific challenges of uplink transmission. While downlink capacity saw significant improvements with advanced techniques, uplink efficiency remained a bottleneck, constrained by UE transmit power and available bandwidth. Transmitting raw, repetitive data (like protocol headers) consumes valuable radio resources and UE battery life unnecessarily.
The technology solves this by applying lossless compression at the source (the UE), directly reducing the payload size before it consumes radio interface resources. This is particularly important for latency-tolerant IoT devices, which often send small, periodic reports, and for scenarios with limited uplink coverage. By improving spectral efficiency, UDC allows networks to serve more users with the same bandwidth or to deliver the same user experience with lower resource allocation, leading to cost savings and enhanced performance. Its introduction in LTE-Advanced (Rel-9) was part of a broader effort to optimize all aspects of the radio interface for efficient data handling.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (139 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-9, normative work from Rel-15.
In Release 15, the Uplink Data Compression (UDC) function was newly introduced with a specific compression algorithm. The standard introduced the DEFLATE-based UDC solution as the defined compression method. Furthermore, the release included corrections and clarifications regarding the UDC data format and its configuration.
- Header compression for MC services over MBMS TS 23.280CR0058
- Introduction of DEFLATE based UDC Solution TS 36.300CR1090
- Introduction of DEFLATE based UDC Solution TS 36.306CR1543
- Introduction of DEFLATE based UDC Solution TS 36.323CR0217
- Introduction of DEFLATE based UDC Solution TS 36.331CR3211
- Introduction of PDCP duplication TS 38.323CR0009
+ 45 more changes
In Release 16, the new developments for Uplink Data Compression (UDC) included the introduction of EHC (Ethernet Header Compression) in LTE PDCP and specific handling for UDC reconfiguration and BufferSize reconfiguration during RRC connection re-establishment. The release also allowed for a PDCP version change to occur without requiring a handover procedure. These enhancements built upon the foundational UDC principle of simplifying network topology and avoiding data duplication.
- Support of QCI values for Framework for Live Uplink Streaming (FLUS) TS 29.212CR1698
- Support of Framework for Live Uplink Streaming (FLUS) in Rx interface TS 29.214CR1632
- Introducing EHC in LTE PDCP TS 36.323CR0278
- Mapping of Uplink Traffic to Backhaul RLC Channels TS 38.300CR0255
- Uplink Tx DC location reporting for two carrier uplink CA TS 38.306CR0539
- Configuration for uplink power boosting via suspended IBE requirements TS 38.331CR2008
+ 33 more changes
In Release 17, the key new development for Uplink Data Compression (UDC) was its introduction as a supported function in the NR (New Radio) air interface. The release also included specific corrections and parameter definitions to ensure proper operation, such as corrections for the PDCP Control PDU used for UDC feedback and the definition of UDC parameters over the E1 interface between base station functions.
- Introducing support of UP IP for EPC connected architectures using NR PDCP TS 36.300CR1353
- Introducing support of UP IP for EPC connected architectures using NR PDCP TS 36.331CR4763
- Introduction of the support for UDC in NR TS 38.300CR0415
- Introducing support of UP IP for EPC connected architectures using NR PDCP TS 38.323CR0085
- Introduction of the support for UDC in NR TS 38.323CR0087
- Introducing support of UP IP for EPC connected architectures using NR PDCP TS 38.331CR2904
+ 25 more changes
In Release 18, the UDC (User Data Convergence) function introduced support for separate uplink and downlink PDU set QoS parameters, enhancing the granularity of quality of service management. This allows applications interfacing with the UDC to manage uplink and downlink data flows independently according to their specific requirements. Furthermore, the release included corrections and refinements to the PDCP configuration to ensure proper handling for multicast MRB (Multicast Radio Bearer) within the converged data architecture.
- Introduction of MIMO evolution for Downlink and Uplink TS 38.300CR0742
- Support of oversize UL SDT Data Arrival [Large SDT Uplink Data] TS 38.300CR0748
- Introduction of NR sidelink PDCP duplication in TS 38.323 TS 38.323CR0126
- Introduction of separate uplink and downlink PDU set QoS parameters TS 37.483CR0104
- Support of PDCP SN Gap Report TS 37.483CR0135
- Correction to PDCP duplication description for L2 MP using SL relay or N3C indirect path TS 38.300CR0989
+ 7 more changes
In Release 19, the UDC (User Data Convergence) function was not updated. The provided Change Request titles and grounding specification text contain no new details, corrections, or enhancements specific to UDC for this release.
- Introduction of R19 XR enhancements for PDCP spec. TS 38.323CR0149
- XR PDCP corrections TS 38.323CR0151
- Clarification on NR uplink transmission duty cycle TS 38.306CR1407
- Correction on pdcp-Config for SRB4 and SRB5 TS 38.331CR5586
- Correction on uplink power control for Type-1 CG-PUSCH [PL RS Type 1 CG] TS 38.331CR5606
Explore further
Broader topics and technologies where UDC plays a role.
Defining Specifications
3GPP specifications that define or reference UDC, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 22.985 vj00 | 3GPP User Data Convergence (UDC) concept | Rel-19 |
| TS 23.203 vj20 | Policy and charging control architecture | Rel-19 |
| TS 23.280 vk10 | Common Architecture for Mission Critical Services | Rel-20 |
| TS 23.335 vj00 | User Data Convergence (UDC) Procedures | Rel-19 |
| TS 23.845 va00 | UDC Evolution Study | Rel-10 |
| TS 23.862 vc00 | Interworking Solutions for Mobile Operators & Data Apps | Rel-12 |
| TS 29.212 vj00 | Gx/Gxx/Sd/St Diameter Protocol | Rel-19 |
| TS 29.213 vj20 | PCC Signalling Flows and QoS Mapping | Rel-19 |
| TS 29.214 vj20 | Policy and Charging Control over Rx | Rel-19 |
| TS 29.215 vj00 | S9 Reference Point Stage 3 Specification | Rel-19 |
| TR 29.935 vj00 | HSS Reference Data Model for Ud Interface | Rel-19 |
| TS 32.181 vj00 | User Data Convergence Management Framework | Rel-19 |
| TS 32.182 vj00 | UDC Common Baseline Information Model (CBIM) | Rel-19 |
| TR 32.901 vj00 | UDC Application Data Models Study | Rel-19 |
| TS 36.300 vj00 | E-UTRAN Radio Interface Protocol Architecture Overview | Rel-19 |
| TS 36.306 vj00 | E-UTRA UE Radio Access Capability Parameters | Rel-19 |
| TS 36.323 vj00 | PDCP Protocol Specification | Rel-19 |
| TS 36.331 vj00 | LTE RRC Protocol Specification | Rel-19 |
| TS 36.754 vf10 | Study on Uplink Data Compression in LTE | Rel-15 |
| TS 37.483 vj10 | E1 Application Protocol (E1AP) | Rel-19 |
| TS 38.300 vj00 | NG-RAN Overall Description | Rel-19 |
| TS 38.306 vj00 | NR UE Radio Access Capability Parameters | Rel-19 |
| TS 38.323 vj00 | Packet Data Convergence Protocol (PDCP) | Rel-19 |
| TS 38.331 vj00 | NR Radio Resource Control (RRC) Protocol Specification | Rel-19 |
| TS 38.523 vj20 | 5G NR UE Conformance Testing: Idle/Inactive | Rel-19 |