Description
Operating Band Unwanted Emissions (OBUE) is a key transmitter conformance requirement defined in 3GPP radio specifications (e.g., for Base Stations and User Equipment). It quantifies the unwanted power emitted by a radio transmitter within its designated operating band (the frequency range the radio is licensed to use) but outside its instantaneously occupied channel bandwidth. These emissions are distinct from Out-of-Band (OOB) emissions and spurious emissions, which fall outside the operating band entirely. OBUE primarily consists of spectral regrowth due to power amplifier non-linearity and noise from the transmitter chain. The measurement is typically defined as a spectrum emission mask or as an Adjacent Channel Leakage Ratio (ACLR) within the operating band. The specification sets maximum permissible limits for this unwanted power, expressed in dB relative to the transmitted carrier power (dBc) or in absolute power (dBm). The test procedure involves configuring the transmitter on a specific channel and measuring the power spectral density at defined offset frequencies within the operating band. Compliance ensures that a device's emissions do not excessively degrade its own receiver performance (self-interference in frequency-division duplex systems) and, more critically, do not cause harmful interference to other channels belonging to the same or other operators within the same frequency band. It is a fundamental parameter for ensuring spectral efficiency and coexistence in densely deployed cellular networks.
Purpose & Motivation
OBUE specifications exist to manage intra-band interference, a critical problem in shared spectrum cellular systems. Without strict limits, a powerful transmitter operating on one channel could 'leak' enough energy into adjacent channels to desensitize receivers or completely block communication on those nearby channels. This is especially problematic in wide operating bands (like the 3.5 GHz n78 band for 5G NR) where many channels are packed closely together. Previous approaches focused heavily on Out-of-Band and spurious emissions to protect other services in different bands. However, as spectrum became more valuable and reuse more intense, controlling pollution within the licensed operating band itself became paramount. OBUE requirements address the limitations of only specifying OOB limits by providing a finer-grained control of the emission 'skirt' close to the transmitted carrier. This allows network operators to deploy carriers with minimal guard bands, maximizing spectral efficiency. The introduction of OBUE in 3GPP Rel-15 coincided with the first 5G NR specifications, reflecting the need for tighter RF performance to support wide bandwidths, advanced modulation (like 1024-QAM), and dense carrier aggregation scenarios essential for 5G's high data rate promises.
Classification
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (23 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the specifications introduced new Over-the-Air (OTA) test procedures for Operating Band Unwanted Emissions (OBUE) and Adjacent Channel Leakage Ratio, as indicated in the CR to TS 37.145-2. The release also added Multi-User (MU) evaluation for testing OBUE in the Radiated Configuration (RC) test method and provided specific clarifications for NR operation, including the application of OBUE limits to the sum of emission power over all antenna connectors for Band 41 in Japan.
- Correction of NR related OBUE emissions tables TS 37.105CR0102
- CR to TS 37.145-2: OTA Adjacent Channel Leakage Ratio (6.7.3) and OTA Operating band unwanted emissions (6.7.5) - corrections to text and tables TS 37.145CR0055
- CR to TR 37.843: Addition of MU evaluation for testing output power, ACLR and OBUE in RC test method in subclause 10.4 TS 37.843CR0020
In Release 16, the OBUE (Operating Band Unwanted Emissions) specifications were enhanced with new applicability tables for Wide Area (WA) Base Stations in BC1 and BC3 bands, including specific provisions for BS with standalone NB-IoT carriers. The release also introduced a correction for the FR2 Category B OBUE mask and clarified regional requirements, such as the specific application of OBUE limits to the sum of emission power over all antenna connectors for Band 41 operation in Japan.
- CR to TS 37.104: addition of missing note for BC1/BC3 OBUE applicability table for WA BS, Rel-16 TS 37.104CR0912
- CR to TS 37.105: addition of the OBUE applicability table, Rel-16 TS 37.105CR0213
- CR to TS 37.145-2: addition of the OBUE applicability table, Rel-16 TS 37.145CR0267
- 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: Correction on FR2 Category B OBUE mask TS 38.104CR0108
In Release 17, the specification work clarified and corrected the applicability and table headings for Operating Band Unwanted Emissions (OBUE) requirements. This included providing specific technical details for Band 41 operation in Japan, where OBUE limits must be applied to the sum of emission power over all antenna connectors, and defining rules for multi-band operation within Inter RF Bandwidth gaps. The changes also involved updates to the supporting notes and the structure of the requirement tables for different base station classes and deployment scenarios.
In Release 18, the OBUE function was updated with specific clarifications and corrections for narrow carriers placed adjacent to sub-block edges and for Base Stations supporting multi-band operation. It also introduced new or corrected OBUE requirements for specific deployments, including Band 41 in Japan, 6G licensed bands, and for n100/n101 NR bands. Furthermore, the release provided technical clarifications on calculating limits within Inter RF Bandwidth gaps for multi-band operation and updated absolute limits for ACLR and OBUE in IAB scenarios.
- CR to 38.104: Correction of OBUE requirements for lessthan 5MHz BW TS 38.104CR0618
- CR to 38.115-1: Operating band unwanted emissions (rel-18) TS 38.115CR0051
- CR to 37.104: Clarification on the OBUE limites when narrow carrier adjacent to the sub block edge TS 37.104CR0985
- CR to 37.105: Clarification on the OBUE limites when narrow carrier adjacent to the sub block edge TS 37.105CR0277
- (AAS_BS_LTE_UTRA-Core) CR to TS 37.105: Correction of OBUE requirement applicability in Table 6.6.5.2.2-0 TS 37.105CR0286
- CR to 37.141: Clarification on the OBUE limites when narrow carrier adjacent to the sub block edge TS 37.141CR1041
+ 5 more changes
In Release 19, a correction was made to the Operating Band Unwanted Emissions (OBUE) requirements for multi-band operation, specifically addressing the calculation for Base Stations operating with multiple bands. The change clarifies that for a BS with an Inter RF Bandwidth gap of less than 2×Δf_OBUE, the emissions within that gap must not exceed the cumulative sum of the minimum requirements specified at the RF Bandwidth edges on each side.
- (TEI17) Correction of Operating band unwanted emissions for multi-band connector TS 38.104CR0748
Explore further
Broader topics and technologies where OBUE plays a role.
Defining Specifications
3GPP specifications that define or reference OBUE, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 37.104 vj10 | MSR Base Station RF Characteristics | Rel-19 |
| TS 37.105 vj10 | AAS Base Station Transmission & Reception Requirements | 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 |
| TR 37.843 vf70 | AAS BS Radiated RF Requirement Background | Rel-15 |
| TR 37.941 vj20 | RF Conformance Testing Background for Radiated BS Requirements | 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 38.115 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 38.817 | 3GPP TR 38.817 | Rel-15 |
| TR 38.844 vi00 | Efficient utilization of licensed spectrum | Rel-18 |
| TR 38.877 vi10 | Technical Report | Rel-18 |
