TPC

Transmit Power Control Command Error Rate

Physical Layer →
Introduced in R99

TPC is the error rate of Transmit Power Control commands sent over the radio interface, a metric critical for evaluating the reliability of power control signaling in UMTS and LTE systems.

Category
Physical Layer
Introduced
R99
Where
Radio Access Network › NG-RAN (5G)
Specifications
34 specs
TPC Description Purpose Related Classification Detected Changes Specifications

Description

Transmit Power Control Command Error Rate (TPC CER) is a key performance indicator defined in 3GPP specifications for UMTS (UTRAN) and LTE systems. It quantifies the probability that a Transmit Power Control (TPC) command, transmitted over the physical layer, is received in error by the intended receiver (either the User Equipment or the NodeB). TPC commands are essential for closed-loop power control, where the receiver instructs the transmitter to increase or decrease its output power to maintain a target signal quality, typically measured as Signal-to-Interference Ratio (SIR). The TPC CER is calculated as the ratio of erroneously decoded TPC commands to the total number of TPC commands sent over a defined measurement period, under specific channel conditions.

In operation, TPC commands are embedded in dedicated physical channels. For example, in UMTS FDD, TPC bits are part of the uplink DPCCH and downlink DPCH. The receiver (NodeB in uplink, UE in downlink) decodes these bits to determine the power adjustment command. Errors can occur due to channel impairments like fading, interference, or noise, leading to incorrect power adjustments. A high TPC CER degrades the effectiveness of power control, causing the transmitter to use suboptimal power levels. This can result in increased interference to other users, reduced link quality, higher battery consumption in UEs, and overall degradation of system capacity and coverage. Therefore, TPC CER is a critical parameter for network planning, optimization, and conformance testing of UEs and base stations.

The measurement of TPC CER is specified under various test conditions in 3GPP TS 25.101 (UE radio transmission and reception), TS 25.104 (NodeB radio transmission and reception), and similar LTE specs. These define reference measurement channels, propagation conditions (e.g., multipath fading profiles), and required performance thresholds. For instance, a UE must achieve a TPC CER below a certain value (e.g., 10^-2 or 10^-3) under specified signal-to-noise ratios to be compliant. The metric is used not only for certification but also in drive tests and network monitoring tools to assess real-world power control performance. By ensuring low TPC CER, operators can maintain efficient radio resource management, minimize interference, and provide consistent service quality.

Purpose & Motivation

TPC CER exists as a standardized measure to ensure the reliability of transmit power control signaling, which is fundamental to the operation of CDMA-based systems like UMTS and OFDMA-based systems like LTE with power control features. In these systems, precise power control is vital to combat the near-far problem, manage intra-cell and inter-cell interference, and conserve UE battery life. Without accurate TPC command delivery, power control loops become unstable, leading to degraded network performance. Prior to standardization, power control performance was assessed indirectly through overall link quality metrics, but a direct command error rate metric was needed for precise engineering and equipment validation.

The specification of TPC CER addresses the need for a quantifiable, testable parameter that equipment manufacturers and network operators can use to guarantee that power control mechanisms work as intended under various channel conditions. It enables consistent conformance testing across different vendor equipment, ensuring interoperability and reliable network operation. By defining acceptable error rates, 3GPP ensures that power control commands are sufficiently robust, allowing networks to maintain optimal transmit power levels, maximize capacity, and provide a consistent user experience even in challenging radio environments.

Classification

Part ofSIR
Related approachesDPCCH

Detected Changes Across Releases

from 3GPP Change Requests

Specific changes extracted from the „Change history“ tables of 3GPP specifications (36 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.

Rel-15 7 changes

In Release 15, the TPC (Transmit Power Control Command Error Rate) function was enhanced through clarifications on the power ramping counter procedure and the completion of the description for power saving features. These updates provided more precise definitions for power control measurements, such as specifying the average power measurement period as one power control group (timeslot). The changes ensured tighter integration with network control functions like Connection Admission Control (CAC) and the management of radio resources.

  • Corrections to Unified Access Control TS 38.300CR0036
  • Completion of description of power saving TS 38.300CR0050
  • Slice Aware Access Control TS 38.300CR0028
  • Notification Control TS 38.300CR0108
  • Clarification on power ramping counter TS 38.300CR0125
  • Approved by plenary – Rel-15 spec under change control TS 38.202

+ 1 more changes

Rel-16 7 changes

In Release 16, the new aspects for TPC primarily focused on introducing and correcting UE Power Saving features, which inherently involve power control mechanisms. The release specifically introduced power saving procedures within the physical layer specifications (as indicated by references to 38.212) and applied these to NR (New Radio). Furthermore, corrections were made to these power-saving features, including aspects related to notification control, following decisions from the RAN plenary meetings.

  • Introduction of UE Power Savings TS 38.202CR0014
  • Introduction of power saving in 38.212 TS 38.212CR0028
  • Introduction of UE Power Saving in NR TS 38.300CR0193
  • Corrections for power saving after RAN1#100-e TS 38.212CR0035
  • Corrections for power saving TS 38.212CR0039
  • Corrections on AQP for notification control TS 38.300CR0328

+ 1 more changes

Rel-17 10 changes

In Release 17, the enhancements to the TPC (Transmit Power Control) command error rate function were introduced as part of the broader UE power saving enhancements. These changes included specific corrections and clarifications to the relevant technical specifications, such as TS 38.212 and TS 38.300, to improve the reliability and accuracy of power control signaling. The focus was on optimizing UE power consumption while maintaining uplink transmission integrity, including clarifications related to uplink full power transmission indications.

  • Introduction of Rel-17 UE power saving enhancements TS 38.212CR0091
  • Introduction of UE power saving enhancements In 38.300 TS 38.300CR0417
  • Corrections on NR UE Power Saving Enhancements TS 38.202CR0023
  • Corrections on UE power saving enhancements in 38.212 TS 38.212CR0103
  • Corrections on UE power saving enhancements in 38.212 TS 38.212CR0111
  • Corrections on UE Power Saving Enhancements for NR in TS 38.212 TS 38.212CR0120

+ 4 more changes

Rel-18 5 changes

In Release 18, the TPC (Transmit Power Control Command Error Rate) function was updated to provide clarification on TPC commands for typeA SRS (Sounding Reference Signal) when using SUL (Supplementary Uplink). This change ensured proper power control operation in scenarios involving SUL, aligning with other Release 18 enhancements like the introduction and specification of Network-Controlled Repeaters across multiple technical documents.

  • Introduction of Rel-18 network controlled repeaters TS 38.212CR0150
  • Introducing support for Network-Controlled Repeaters to 38.300 TS 38.300CR0685
  • Corrections on Rel-18 network controlled repeaters in 38.212 TS 38.212CR0174
  • Clarification to Network-Controlled Repeaters Stage-2 description TS 38.300CR0808
  • Clarification on typeA SRS TPC commands for SUL TS 38.212CR0176
Rel-19 7 changes

In Release 19, the primary new work related to TPC was not directly addressed in the provided materials. The listed Change Requests and grounding context focus on introducing new features like the low-power Wake-up Signal for NR and on-demand positioning system information block requests, alongside corrections to various procedures and descriptions, but do not specify any updates to the Transmit Power Control Command Error Rate function itself.

  • Introduction of Rel-19 low-power Wake-up Signal for NR TS 38.212CR0217
  • Introduction of control parameters for on-demand posSIB request [OdPosSIB_Req] TS 38.300CR1009
  • Introduction of Low-Power Wake-Up Signal and Receiver for NR TS 38.300CR1015
  • Corrections on Rel-19 low-power Wake-up Signal for NR TS 38.212CR0228
  • Correction on A-IoT Inventory and Command procedure figures TS 38.300CR1072
  • Correction on the description of NG Control Plane TS 38.300CR1110

+ 1 more changes

Explore further

Broader topics and technologies where TPC plays a role.

Topics
Testing & ConformanceMEC (Edge Computing)LTE / LTE-AdvancedLawful InterceptSMS & MessagingUMTS / WCDMA
Technologies
LTE

Defining Specifications

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

SpecificationTitleRelease
TR 21.905 vj00 3GPP Technical Terms and Definitions Rel-19
TS 25.101 vj00 UTRA FDD UE RF Requirements Rel-19
TS 25.102 vj00 UTRA TDD RF Characteristics Rel-19
TS 25.103 v1100 RF Requirements for RRM R99
TS 25.104 vj00 UTRA FDD Base Station RF Characteristics Rel-19
TS 25.105 vj00 UTRA TDD Base Station RF Requirements Rel-19
TS 25.123 vj00 Radio Resource Management for TDD Rel-19
TS 25.133 vj00 UTRAN RRM Requirements for FDD Rel-19
TS 25.141 vj00 UTRA FDD Base Station RF Conformance Testing Rel-19
TS 25.211 vj00 UTRA FDD Layer 1: Transport & Physical Channels Rel-19
TS 25.212 vj00 UTRA FDD Layer 1 Multiplexing & Channel Coding Rel-19
TS 25.214 vj00 UTRA FDD Physical Layer Procedures Rel-19
TS 25.221 vj00 UTRA TDD Physical Layer Specification Rel-19
TS 25.222 vj00 UTRA TDD Multiplexing & Channel Coding Rel-19
TS 25.224 vj00 UTRA TDD Physical Layer Procedures Rel-19
TS 25.301 vj00 UE-UTRAN Radio Interface Protocol Architecture Rel-19
TS 25.302 vj00 UTRA Physical Layer Services Rel-19
TS 25.308 vj00 HSDPA Overall Description Rel-19
TS 25.321 vj00 MAC Protocol Specification for UTRAN Rel-19
TS 25.322 vj00 RLC Protocol Specification Rel-19
TS 25.423 vj00 UTRAN RNSAP Specification Rel-19
TS 25.427 vj00 UTRAN Iub/Iur User Plane Protocols Rel-19
TS 25.433 vj00 Node B Application Part (NBAP) Protocol Rel-19
TS 25.702 vc10 DCH Enhancements for UMTS Study Rel-12
TS 25.800 vc10 UMTS Heterogeneous Networks Study Rel-12
TR 25.903 vj00 Continuous Connectivity for Packet Data Users Rel-19
TR 25.927 ve00 Energy Saving Solutions for UMTS Node B Rel-14
TR 25.929 vj00 Continuous Connectivity for Packet Data Users Rel-19
TS 38.101 vj31 NR User Equipment Radio Transmissions Rel-19
TS 38.202 vj00 5G NR Physical Layer Services Rel-19
TS 38.212 vj10 NR Multiplexing and Channel Coding Rel-19
TS 38.300 vj00 NG-RAN Overall Description Rel-19
TS 38.521 vj20 NR Physical Layer UE Conformance Testing Rel-19
TR 38.889 vg00 NR-based access to unlicensed spectrum study Rel-16