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
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (1 CRs across 1 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, a key update to the Unwanted Emissions Mask (UEM) function involved specific corrections to the mask for operating bands n7 and n38. Furthermore, the release defined the UEM for Medium Range Base Stations, establishing its limits relative to output power scaling from 38 dBm down to 31 dBm, with absolute limits applying for power below 31 dBm.
- 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
Explore further
Broader topics and technologies where UEM plays a role.
Defining Specifications
3GPP specifications that define or reference UEM, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| 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 |
