UEM

Unwanted Emissions Mask

Physical Layer →
Introduced in Rel-11

UEM is the regulatory specification defining the permissible limits of a transmitter's radio frequency emissions outside its assigned carrier bandwidth to prevent harmful interference to other systems.

Category
Physical Layer
Introduced
Rel-11
Where
Radio Access Network › NG-RAN (5G)
Specifications
6 specs
UEM Description Purpose Related Classification Detected Changes Specifications

Description

The Unwanted Emissions Mask (UEM) is a set of limits specified in 3GPP technical documents that constrain the out-of-band and spurious emissions of radio transmitters. Unwanted emissions consist of several components: Out-of-Band Emissions (OOBE), which are emissions immediately outside the assigned channel bandwidth due to modulation and power amplifier non-linearities; and Spurious Emissions, which are emissions at frequencies far removed from the carrier, often due to harmonics, intermodulation, or clock noise. The UEM defines a power limit profile across a range of frequencies offset from the carrier center.

Architecturally, the UEM is a requirement imposed on the design of the radio transmitter, affecting the RF front-end, power amplifier, filtering, and digital signal processing. It is measured during equipment conformance testing. The mask is typically defined as a maximum permissible power level (in dBm) within a specified measurement bandwidth at a given frequency offset from the edge of the channel bandwidth. Different masks may apply for base stations (BS) and user equipment (UE), and they can vary depending on the band of operation and the technology (e.g., LTE vs NR).

Its role is fundamental to spectrum management and interference avoidance. By adhering to the UEM, a 3GPP-compliant device ensures it does not pollute the radio spectrum, protecting services in neighboring bands (which could be other cellular systems, Wi-Fi, radar, or satellite links). Compliance with UEM is mandatory for regulatory approval (e.g., by FCC or ETSI). The specifications (37.809, 37.810, 38.104, etc.) provide the detailed numerical limits and test methodologies for verifying these emissions.

Purpose & Motivation

The UEM exists to enable the peaceful coexistence of multiple radio systems within the crowded radio spectrum. Without strict limits on unwanted emissions, a powerful 5G base station could desensitize receivers of a nearby 4G system or even a non-cellular service. Historically, as cellular technology evolved with wider bandwidths and more complex modulation (e.g., from GSM to 5G NR), the potential for unwanted emissions increased, necessitating more refined and stringent masks.

It addresses the engineering challenge of designing efficient, high-power transmitters that are also 'clean'. The motivation for its continuous evolution across releases is driven by new spectrum allocations (e.g., new NR bands), the introduction of technologies like carrier aggregation (which combines multiple carriers, affecting emission profiles), and the need for global harmonization of equipment standards. Each release updates UEM limits to balance technical feasibility with spectrum protection requirements.

Classification

Part ofOOBE

Detected Changes Across Releases

from 3GPP Change Requests

Specific changes extracted from the „Change history“ tables of 3GPP specifications (12 CRs across 4 releases). Complements the general historical overview above with the evidence-based evolution of this function.

Studied in Rel-11, normative work from Rel-15.

Rel-15 2 changes

In Release 15, the specification introduced specific corrections to the Unwanted Emissions Mask (UEM) function, including a targeted correction to the unwanted emissions mask for specific operating bands n7 and n38. Furthermore, the release included updates to the emissions scaling methodology and clarifications on transmitter co-existence and co-location requirements that impact the UEM framework.

  • CR to TS 38.104 on Combined updates from RAN4 #90 This document combines the proposed changes in the following Draft CRs from RAN4 #90: - R4-1900284, "Draft CR on NR PUCCH format2 performance requirements for TS 38.104" - R4-1900763, "Draft CR to TS 38.104: Update of performance requirement numbers for DFT-s-OFDM based PUSCH" - R4-1900876, "Draft CR to TS 38.104: On RX spurious emissions requirement" - R4-1900968, "Draft CR for 38.104: Performance requirements for NR PUCCH format 1" - R4-1901329, "Draft CR to 38.104: Annex C.6 correction" - R4-1901330, "Draft CR to 38.104: Abbreviations addition" - R4-1901387, "Draft CR to TS 38.104 BS demodulation PUCCH format 0 requirements" - R4-1901474, "Draft CR to TS 38.104: Corrections on transmitter co-existence and co-location requirements" - R4-1901483, "Draft CR to TS 38.104: Corrections on general intermodulation requirement" - R4-1902239, "Draft CR to TS 38.104: Addition of missing EIRP/EIS definitions in terminology in clause 3.1" - R4-1902241, "Draft CR to 38.104; clarification of BS power limits" - R4-1902245, "Draft CR to 38.104: Correction to FR2 OTA Interfering signal mean power units" - R4-1902246, "Draft CR to 38.104; Correction to definition of OTA reference sensitivity" - R4-1902260, "draft CR to TS 38.104 - update emissions scaling" - R4-1902338, "Draft CR: Update on FR1 range extension for TS38.104" - R4-1902389, "draftCR for 38.104 on PUSCH requirements with CP-OFDM and FR1" - R4-1902394, "Draft CR to TS 38.104 – PUSCH requirements with CP-OFDM for FR2" - R4-1902396, "CR: Updates to PUCCH formats 3 and 4 performance requirements in TS 38.104" - R4-1902444, "Draft CR to TS 38.104: Editorial CR for BS demodulation requirements" - R4-1902561, "Draft CR for updating PRACH performance requirements in TS38.104" - R4-1902571, "Corrections to 38.104 Delay profile calculation" - R4-1902642, "Draft CR to TS 38.104: Correction on multi-band operation related requirements" TS 38.104CR0019
  • 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
Rel-16 3 changes

In Release 16, the UEM (Unwanted Emissions Mask) function saw clarifications and corrections, including updates to regional requirements for FCC Title 47 limits for OTA operating band unwanted emissions. Specific technical refinements were made to the methodology for Medium Range (MR) and Local Area (LA) Base Stations, ensuring the UEM properly scaled with output power and maintained coexistence guarantees between E-UTRA, UTRA, and GSM carriers, particularly when a GSM carrier is placed at the RF bandwidth edge.

  • 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 to 38.104 on Receiver spurious emissions exclusion band (Rel-16) TS 38.104CR0209
  • CR to 38.104 on Category B OTA spurious emissions for and n257 TS 38.104CR0261
Rel-18 5 changes

In Release 18, the UEM function was updated with specific corrections and new operating band unwanted emission limits. This included clarifications for band n104, the introduction of additional limits for band n100, and the definition of requirements for Single RAT Base Stations supporting multi-band operation. Furthermore, corrections were made to transmitter spurious emissions for the protection of Band n20.

  • CR to TS 38.104 on table references for OTA operating band unwanted emission limits TS 38.104CR0437
  • CR to TS 38.104 on corrections and clarifications of operating band unwanted emission limits for band n104 TS 38.104CR0470
  • CR for TS 38.104: Operating band unwanted emissions for Single RAT BS supporting multi-band operation TS 38.104CR0482
  • [NR_RF_FR1-Core] CR to TS 38.141-1 on correction of transmitter spurious emissions for protection of Band n20 TS 38.104CR0524
  • (NR_RAIL_EU_900MHz-Core) CR to TS 38.104 on additional unwanted emission limits for band n100 TS 38.104CR0563
Rel-19 2 changes

In Release 19, the UEM function was updated with corrections for specific device types and multi-band scenarios. This included a correction on the output RF spectrum emissions for A-IoT devices to ensure proper limits. Furthermore, a correction was made to the operating band unwanted emissions requirements for equipment using a multi-band connector to guarantee accurate co-existence.

  • CR for TS 38.191, Correction on A-IoT Device Output RF spectrum emissions TS 38.191CR0002
  • (TEI17) Correction of Operating band unwanted emissions for multi-band connector TS 38.104CR0748

Explore further

Broader topics and technologies where UEM plays a role.

Topics
Spectrum & CoexistenceTesting & ConformanceLTE / LTE-Advanced5G NR (New Radio)Lawful InterceptManagement & Operations
Technologies
LTE5G

Defining Specifications

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

SpecificationTitleRelease
TS 37.809 vb00 E-UTRA & MSR BS Class Requirements Rel-11
TS 37.810 vc20 Study on Base Station Specification Structure Rel-12
TS 38.104 vj20 NR Base Station RF Requirements Rel-19
TS 38.191 vj00 NR Ambient IoT RF Characteristics Rel-19
TS 38.194 vj00 Ambient IoT Base Station RF Spec Rel-19
TS 38.817 3GPP TR 38.817 Rel-11