Description
Error Vector Magnitude (EVM) is a fundamental performance measurement for the physical layer of digital radio transmitters, particularly in orthogonal frequency-division multiplexing (OFDM) and single-carrier systems used in 3GPP standards. It is defined as the root-mean-square (RMS) value of the error vector—the vector difference in the I/Q (In-phase/Quadrature) plane between the ideal constellation point (as defined by the modulation scheme, e.g., QPSK, 16QAM, 64QAM, 256QAM) and the actual measured point of the received symbol after timing, frequency, and phase corrections have been applied. The result is typically normalized to the power of the ideal signal and expressed as a percentage or in dB.
The measurement process involves capturing the transmitted signal, synchronizing to it, and equalizing the channel effects as much as possible to isolate the transmitter's impairment. For multi-carrier systems like OFDM, EVM is measured per subcarrier and often aggregated as an RMS average over a specified set of subcarriers and symbols within a measurement period. Key sources of EVM include transmitter imperfections such as phase noise from the local oscillator, non-linear distortion from the power amplifier (causing spectral regrowth and compression), I/Q imbalance (gain and phase mismatch between I and Q paths), and residual carrier frequency offset. Each of these impairments causes the constellation points to spread or rotate, increasing the EVM.
In 3GPP specifications (e.g., TS 36.104 for LTE, TS 38.104 for NR), EVM is a core transmitter requirement specified for each supported modulation order in the base station (BS) and user equipment (UE) radio conformance tests. Strict EVM limits are defined to ensure that the transmitted signal is sufficiently accurate to allow the receiver to demodulate data with a low block error rate (BLER). For higher-order modulations like 256QAM or 1024QAM, which pack more bits per symbol and have smaller decision regions between constellation points, the permitted EVM is much tighter (e.g., 3.5% for 256QAM in NR) compared to lower-order modulations like QPSK (e.g., 17.5%). This makes EVM a direct enabler of high spectral efficiency. The specifications detail the exact measurement procedure, including the reference signal used (e.g., dedicated pilots or DM-RS), the measurement bandwidth, and the exclusion of certain time/frequency resources.
Purpose & Motivation
EVM exists as a comprehensive, single-figure-of-merit to quantify the overall modulation quality of a digital transmitter, replacing older, less precise metrics like signal-to-noise ratio (SNR) for assessing linearity and purity in complex modulated signals. As mobile systems evolved from 2G GMSK to 3G/4G/5G high-order QAM, the need for a precise measure of transmitter imperfections became critical because these imperfections directly limit the achievable data rates and cell-edge performance. Without tight control of EVM, higher-order modulations would fail, forcing the link adaptation to fall back to more robust but less efficient schemes, reducing network capacity.
The primary problem EVM solves is providing equipment manufacturers and network operators with a standardized, repeatable method to verify that a radio transmitter meets the minimum performance needed for reliable communication. It correlates strongly with system-level performance metrics like throughput and BLER. By specifying maximum EVM values in conformance tests, 3GPP ensures interoperability—a UE from one vendor can successfully demodulate signals from a base station from another vendor, even under non-ideal conditions. This was especially important for the global success of LTE and NR.
Historically, as each new generation introduced higher bandwidths and more complex modulation, the sources of EVM degradation became more challenging to manage. The creation of detailed EVM specifications motivated advancements in radio frequency (RF) component design, such as improved power amplifier linearization techniques (like digital pre-distortion), lower phase noise oscillators, and better I/Q modulator calibration. Thus, EVM is not just a measurement but a driver for RF technology innovation, enabling the high-speed data services that define modern mobile broadband.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (21 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, specific updates to the EVM (Error Vector Magnitude) function were introduced, including a correction to the EVM annex and a change to replace the term "reference signal" with "ideal signal" within the EVM context in the specifications. These changes, detailed in CRs R4-1907634 and R4-1907629 to TS 38.104, aimed to clarify the measurement methodology and its description.
- CR to TS 37.145-2 Removal of referencing error for in-band blocking TS 37.145CR0070
- CR to TR 37.843: Wave vector spacing sampling grid (Section 10.8.2.6) TS 37.843CR0011
- CR to TR 37.843: Improvement of error contribution decsription for RC in Annex E.5 TS 37.843CR0027
- CR to TS 38.104 Combined updates from RAN4 #90bis and RAN4#91 From RAN4 #90bis: - R4-1903105, "Draft CR to TS 38.104: Corrections on terminologies and editorial errors" - R4-1903319, "Draft CR to TS 38.104: removal of unused definition: "minimum EIRP level under extreme condition"" - R4-1903320, "Draft CR to TS 38.104: OSDD information correction" - R4-1903457, "Draft CR to TS 38.104: Removal of FFS for FR2 TDD OFF power level requirement in clause 9.5" - R4-1903499, "Draft CR to 38.104: Correction to unwanted emissions mask for bands n7 and n38" - R4-1903836, "Draft CR to TS 38.104: Correction on description on multi-band operation in section 4.8" - R4-1904024, "Draft CR to TS 38.104 Applicability rules for BS demodulation" - R4-1904234, "draftCR: Correlation matrix for 8Rx in TS 38.104" - R4-1904723, "Draft CR to TS 38.104: Update of performance requirements for DFT-s-OFDM based PUSCH" - R4-1904726, "draftCR for 38.104 on PUSCH requirements with CP-OFDM and FR1" - R4-1904729, "Draft CR on PRACH performance requirements in TS38.104" - R4-1904734, "Draft CR on TS 38.104 Performance requirement for PUCCH format 1" - R4-1904735, "Draft CR on NR PUCCH format2 performance requirements for TS 38.104" - R4-1904739, "Draft CR to TS 38.104 BS demodulation PUCCH format 0 requirements" - R4-1904745, "draftCR: Updates to PUCCH formats 3 and 4 performance requirements in TS 38.104" - R4-1904799, "Draft CR to TS 38.104: FRC update for PUSCH FR1 mapping type B and FR2 DMRS 1+1" - R4-1904816, "Draft CR : Clarification on step 5 and step 6 for delay profiles calculation (38.104)" - R4-1904842, "Draft CR to TS 38.104 BS demodulation CP-OFDM PUSCH FR2 requirements" - R4-1905126, "draft CR to 38.104 for TAE requirements" - R4-1905139, "draft CR to TS 38.104 on EVM measurement (Annex B and C)" - R4-1905140, "Draft CR: editorial correction on FR1 spurious emission requirement in TS38.104" - R4-1905143, "Draft CR for TS 38.104: Addition of NOTE for transmitter intermodulation requirements in certain regions" - R4-1905144, "Draft CR to TS 38.104: FRC reference corrections for the Rx requirements" - R4-1905145, "Draft CR to TS 38.104: Clarification on application of interfering signal offsets for ACS, blocking and intermodulation requirements" - R4-1905148, "Draft CR to TS 38.104: Corrections on out-of-band blocking requirement" From RAN4 #91: - R4-1906002, "Draft CR to 38.104: Subclause 6.7 and 9.8 transmitter intermodulation – correction of interfering signal type" - R4-1906096, "Draft CR to 38.104: Correction of frequency range for OTA spurious emissions" - R4-1906311, "Draft CR to 38.104: Correction on FRC (Annex A)" - R4-1906346, "Removal of n65 in Rel-15 38.104" - R4-1906915, "Draft CR to TS 38.104: Clarification on application of interfering signal offsets for OTA ACS, blocking and intermodulation requirements" - R4-1906918, "Draft CR to TS 38.104: Clarification on type of interfering signal for ACS, in-band blocking and ICS requirements" - R4-1907110, "Draft CR to TS 38.104: correction of the fundamental frequency limit of 2.55GHz for the spurious emissions" - R4-1907246, "Draft CR to TS 38.104: Update of performance requirements for DFT-s-OFDM based PUSCH" - R4-1907249, "Draft CR to TS 38.104: Correction on the terminology in PUSCH FRC tables" - R4-1907252, "Draft CR to TS38.104: Updates of PRACH performance requirements" - R4-1907255, "Draft CR on NR PUCCH format2 performance requirements for TS 38.104" - R4-1907258, "Draft CR on NR UCI on PUSCH performance requirements for TS 38.104" - R4-1907261, "draftCR: Updates to PUCCH formats 3 and 4 performance requirements in TS 38.104" - R4-1907266, "Draft CR on TS 38.104 Performance requirement for PUCCH format 1" - R4-1907267, "Draft CR on TS 38.104 Performance requirement for multi-slot PUCCH format 1" - R4-1907272, "Draft CR to TS 38.104 BS demodulation PUCCH format 0 requirements" - R4-1907275, "Draft CR to TS 38.104 BS demodulation CP-OFDM PUSCH FR2 requirements" - R4-1907277, "draftCR for 38.104 on PUSCH requirements with CP-OFDM and FR1" - R4-1907629, "Draft CR to 38.104: Term “reference signal” replacing by term “ideal signal” in EVM context" - R4-1907634, "Draft CR to 38.104: corrections to the EVM annex" - R4-1907659, "Draft CR to TS 38.104 on Spurious emission Category B in FR2" - R4-1907661, "Draft CR to 38.104 Definition of contiguous transmission bandwidth" - R4-1907662, "Draft CR to 38.104: BS TAE requirements" - R4-1907664, "Draft CR to 38.104: Clarification of interferer RB frequency for narrowband blocking" - R4-1907672, "Draft CR for TS 38.104: Correction on EVM" - R4-1907689, "Correction to CA carrier spacing" TS 38.104CR0029
In Release 16, specific technical clarifications and corrections were made to the EVM (Error Vector Magnitude) function, including a defined frame averaging method for EVM and corrections to the EVM window length calculations. The release also clarified the applicability of EVM for V2X in non-concurrent operation and introduced performance requirement updates for various channels like DFT-s-OFDM based PUSCH and NR PUCCH formats. These changes refined the measurement procedures and performance criteria to ensure greater accuracy and applicability for new use cases.
- Applicability of Error Vector Magnitude for V2X for non-concurrent operation TS 38.522CR0067
- CR to T 38.104: Implementation of endorsed draft CRs from RAN4#92 (Rel-16) (Mirrors changes in R4-1908440 for Rel-15 TS 38.104) - R4-1907940, "Draft CR to TS 38.104: Correction on the terminology in FRC tables in A.1 and A.2" - R4-1908307, "Draft CR to TS 38.104: Clarification on application of OTA receiver requirements for BS supporting polarization" - R4-1908387, "Draft CR for TS38.104: editorial correction for reference meausrement channel" - R4-1908619, "Draft CR to TS38.104: Correction on interferer frequency offset values for ACS" - R4-1908629, "Draft CR to TS38.104: Corrections on EVM window length (Annex B.5.2, C.5.2)" - R4-1908774, "DraftCR to 38.104: Editorial Corrections to redudant units in clause 10.8.3" - R4-1908805, "Draft CR to 38.104: Limits in FCC title 47 for OTA operating band unwanted emissions (9.7)" - R4-1909270, "Draft CR to TS 38.104: Receiver spurious emissions frequency correction" - R4-1909309, "DraftCR to TS 38.104: text corrections, Rel-15" - R4-1909310, "DraftCR to 38.104: correction of TAB connectors mapping to TAB connector TX min cell group, Rel-15" - R4-1909416, "draft CR 38.104 - correct reference to annex F" - R4-1910066, "Draft CR to TS 38.104: Update of performance requirements for DFT-s-OFDM based PUSCH" - R4-1910069, "Draft CR on NR PUCCH format2 performance requirements for TS 38.104" - R4-1910072, "Draft CR on NR UCI on PUSCH performance requirements for TS 38.104" - R4-1910075, "draftCR for 38.104 on PUSCH requirements with CP-OFDM and FR1" - R4-1910078, "Draft CR to TS38.104: Updates to NR PRACH performance requirements" - R4-1910081, "Draft CR to TS 38.104 BS demodulation PUCCH format 0 requirements" - R4-1910084, "Draft CR to TS 38.104 BS demodulation CP-OFDM PUSCH FR2 requirements" - R4-1910088, "Draft CR for 38.104: Performance requirements for NR PUCCH format 1" - R4-1910089, "Draft CR for 38.104: Performance requirements for NR multi-slot PUCCH" - R4-1910094, "draftCR: Updates to PUCCH formats 3 and 4 performance requirements in TS 38.104" - R4-1910431, "Corrections to EVM calculations in 38.141-1 annex B" - R4-1910462, "Draft CR to 38.104: Correction on regional requirements (4.5)" - R4-1910493, "Draft CR to TS 38.104 correction to Annex C.7" - R4-1910606, "Draft CR for TS 38.104: Channel spacing for adjacent NR carriers" TS 38.104CR0034
- CR Frame averaging for EVM Annex B and C in TS 38.104 TS 38.104CR0110
In Release 17, the EVM (Error Vector Magnitude) function saw updates including the introduction of a new EVM test case applicability and corrections to the repeater EVM test procedure. Furthermore, specific errors in the EVM requirements and related test procedures were corrected within the relevant technical specifications.
- CR to 38.106: EVM requirements TS 38.106CR0027
- CR for TS 38.106: Correction of some errors in 3.2 TS 38.106CR0029
- CR for TS 38.115-1: Correction of some errors TS 38.115CR0001
- CR to 38.115-1: Correction on repeater EVM test procedure TS 38.115CR0005
- CR to TS 38.176-2 with bracket removal for measurement uncertainties for OTA timing error between IAB-DU and IAB-MT TS 38.176CR0017
- New EVM test case applicability TS 38.522CR0156
In Release 18, the updates to the EVM function specifically involved corrections and refinements to test cases for NB-IoT and IoT NTN. This included a correction to message exceptions for the EVM NPRACH test case for NB-IoT and the splitting and updating of frequency error test cases for IoT Non-Terrestrial Networks. These changes aimed to improve the precision and applicability of conformance testing for these technologies.
In Release 19, specific updates were made to the Error Vector Magnitude (EVM) function, including the addition of an EVM window length specification for FR1-NTN Ku bands and the addition of applicability rules for EVM equalizer spectrum flatness for FR2 Carrier Aggregation (CA). These changes provide more detailed testing parameters for new frequency bands and aggregation scenarios.
- Update of Doppler and delay in IoT NTN frequency error test cases TS 36.521CR0137
- CR to 38.104 for correction of errors in the SBFD introduction TS 38.104CR0752
- CR to TS38.108 Add EVM window length for FR1-NTN Ku bands TS 38.108CR0140
- Addition of Applicability for EVM equalizer spectrum flatness for FR2 CA TS 38.522CR0620
- (IoT_NTN_FDD_LS_band-Core) CR to TS 36.102 for correcting errors TS 36.102CR0127
Explore further
Broader topics and technologies where EVM plays a role.
Defining Specifications
3GPP specifications that define or reference EVM, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| TS 25.106 vj00 | UTRA FDD Repeater RF Performance Requirements | Rel-19 |
| TS 25.141 vj00 | UTRA FDD Base Station RF Conformance Testing | Rel-19 |
| TS 25.142 vj00 | UTRA TDD Base Station RF Test Methods | Rel-19 |
| TS 25.143 vj00 | UTRA FDD Repeater RF Test Requirements | Rel-19 |
| TS 25.153 vj00 | LCR TDD Repeater RF Requirements & Testing | Rel-19 |
| TS 36.101 vj30 | LTE UE Radio Transmission & Reception Requirements | Rel-19 |
| TS 36.102 vj10 | E-UTRA UE Satellite Access RF Requirements | Rel-19 |
| TS 36.104 vj10 | Base Station (BS) radio transmission and reception | Rel-19 |
| TS 36.106 vj00 | E-UTRA FDD Repeater RF Requirements | Rel-19 |
| TS 36.108 vj10 | Satellite Access Node RF Requirements | Rel-19 |
| TS 36.116 vj00 | E-UTRA Relay RF Requirements | Rel-19 |
| TS 36.117 vj00 | E-UTRA Relay RF Test Methods & Requirements | Rel-19 |
| TS 36.141 vj00 | E-UTRA BS Conformance Testing | Rel-19 |
| TS 36.143 vj00 | E-UTRA FDD Repeater RF Testing | Rel-19 |
| TS 36.181 vj30 | E-UTRA RF Test Methods for Satellite Access Node | Rel-19 |
| TS 36.521 vj00 | E-UTRA UE Conformance ICS Proforma | Rel-19 |
| TS 36.747 ve00 | Enhanced CRS and SU-MIMO IM Performance Requirements | Rel-14 |
| TR 36.770 vi00 | Technical Report for High Power UE in LTE Band 14 | Rel-18 |
| TS 36.863 vc00 | CRS Interference Mitigation for Homogeneous Networks | Rel-12 |
| TS 37.104 vj10 | MSR Base Station RF Characteristics | Rel-19 |
| TS 37.141 vj10 | RF Test Methods for Multi-Standard Radio Base Stations | Rel-19 |
| TS 37.145 vj10 | AAS Base Station Conducted Conformance Testing | Rel-19 |
| TS 37.802 va10 | MSR BS RF Requirements for Non-Contiguous Spectrum | Rel-10 |
| TS 37.812 vb30 | Multi-band Multi-standard Radio BS Requirements | Rel-11 |
| TR 37.843 vf70 | AAS BS Radiated RF Requirement Background | Rel-15 |
| TR 37.900 vj00 | Multi-Standard Radio (MSR) Base Station Requirements | Rel-19 |
| TR 37.901 vf10 | UE Application Layer Data Throughput Performance | Rel-15 |
| TR 37.941 vj20 | RF Conformance Testing Background for Radiated BS Requirements | Rel-19 |
| TS 38.101 vj31 | NR User Equipment Radio Transmissions | Rel-19 |
| TS 38.104 vj20 | NR Base Station RF Requirements | Rel-19 |
| TS 38.106 vj20 | NR Repeater Radio Transmission and Reception | Rel-19 |
| TS 38.108 vj20 | NTN NR Satellite Access Node RF Requirements | Rel-19 |
| TS 38.115 vj20 | NR Repeater RF Conformance Testing Part 1 | Rel-19 |
| TS 38.141 vj20 | NR Base Station RF Conformance Testing Part 1 | Rel-19 |
| TS 38.174 vj10 | NR Integrated Access and Backhaul Radio Spec | Rel-19 |
| TS 38.176 vj20 | IAB Conformance Testing Specification | Rel-19 |
| TS 38.181 vj10 | NR Satellite Access Node RF Testing | Rel-19 |
| TS 38.521 vj20 | NR Physical Layer UE Conformance Testing | Rel-19 |
| TS 38.522 vj11 | UE Conformance Test Applicability Statement | Rel-19 |
| TS 38.551 vi30 | User Equipment (UE) Multiple Input Multiple Output (MIMO) Over-the-Air (OTA) performance | Rel-18 |
| TS 38.741 vj00 | NTN L-/S-band for NR Technical Specification | Rel-19 |
| TS 38.755 vj10 | NR FR1 DL Fragmented Carriers Study | Rel-19 |
| TR 38.785 vh00 | UE radio transmission for enhanced NR sidelink | Rel-17 |
| TR 38.786 vi20 | Technical Report for NR Sidelink Evolution | Rel-18 |
| TS 38.787 vj00 | UE Radio Transmission for Sidelink CA in ITS Band | Rel-19 |
| TS 38.793 vj00 | Simultaneous Rx/Tx Band Combinations TR | Rel-19 |
| TR 38.810 vg70 | NR OTA Test Methods Study | Rel-16 |
| TS 38.817 | 3GPP TR 38.817 | R99 |
| TS 38.831 vg10 | UE RF Requirements for FR2 Enhancements | Rel-16 |
| TR 38.839 vh00 | Simultaneous Rx/Tx band combinations | Rel-17 |
| TS 38.843 vj00 | Study on AI/ML for NR Air Interface | Rel-19 |
| TS 38.863 vj10 | NR NTN RF and Co-existence Spec | Rel-19 |
| TR 38.868 vh00 | Optimizations of pi/2 BPSK uplink power in NR | Rel-17 |
| TR 38.877 vi10 | Technical Report | Rel-18 |
| TR 38.881 vi00 | Technical Report on Lower MSD for Inter-band CA/EN-DC/DC | Rel-18 |
| TR 38.884 vi20 | Technical Report | Rel-18 |
| TR 38.886 vg30 | NR V2X UE Radio Transmission & Reception | Rel-16 |
| TR 38.894 vi00 | Technical Report | Rel-18 |
| TR 38.903 vj00 | Test Tolerances & Measurement Uncertainties | Rel-19 |