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
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (89 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the OBUE (Operating Band Unwanted Emissions) function was updated with new additional unwanted emission limits for the L-Band, alongside corrections to OBUE emissions tables and the unwanted emissions mask. Furthermore, specific requirements were introduced for BS operating in Band 41 in Japan, where OBUE limits apply to the sum of emission power over all antenna connectors. The release also saw the addition of Over-the-Air (OTA) test requirements for OBUE and corrections to emissions scaling factors.
- CR to 37.104: Introduction of new additional unwanted emission limit for L-Band TS 37.104CR0807
- CR to 37.141: Introduction of new additional unwanted emission limit for L-Band TS 37.141CR0812
- Correction on unwanted emission mask for TS 37.105 TS 37.105CR0095
- Addition of NR to co-existence and co-location related emissions for single RAT BS TS 37.105CR0101
- Correction of NR related OBUE emissions tables TS 37.105CR0102
- CR to TS 37.105 on Correction of unwanted emissions scaling TS 37.105CR0129
+ 12 more changes
In Release 16, key refinements to the Operating Band Unwanted Emissions (OBUE) function included the formal addition and correction of OBUE applicability tables for various base station types, such as for Wide Area (WA) BS and in OTA testing specifications. Specific technical corrections were made to the unwanted emissions mask for bands n7 and n38 and to the OBUE mask for FR2 Category B base stations. Furthermore, the release introduced clarifications and procedural corrections for measuring OBUE, including updates for non-contiguous spectrum operation and the use of specific measurement techniques like the orthogonal cut grid.
- CR to TS 37.104: addition of missing note for BC1/BC3 OBUE applicability table for WA BS, Rel-16 TS 37.104CR0912
- Correction to unwanted emissions mask for bands n7 and n38 TS 37.104CR0849
- CR to 37.104: Correction to ACLR limit in non-contiguous spectrum (Rel-16) TS 37.104CR0914
- Correction to RX spurious emissions applicability range for SR E-UTRA BS TS 37.105CR0154
- CR to TS 37.105: Correction on operation band unwanted emission TS 37.105CR0162
- CR to TS 37.105: addition of the OBUE applicability table, Rel-16 TS 37.105CR0213
+ 13 more changes
In Release 17, the specifications for Operating Band Unwanted Emissions (OBUE) were refined with corrections and clarifications to table headings, applicability notes, and specific limits. Key updates included corrections to ACLR requirements for non-contiguous spectrum and for Local Area (LA) base stations, as well as modifications to spurious emissions limits for Active Antenna System (AAS) base stations tested Over-The-Air (OTA) to ensure coexistence with other systems. Furthermore, the requirements for NR repeaters were explicitly addressed, defining their ACLR and receiver spurious emissions obligations.
- CR to TS 38.104 on BS channel bandwidth per operating band TS 38.104CR0310
- CR to TS38.106: clarification on the supported operating bands for NR repeater TS 38.106CR0009
- CR to 38.106: NR repeater ACLR requirements TS 38.106CR0013
- CR to 38.106: NR repeater receiver spurious emissions requirements TS 38.106CR0015
- CR to 38.106: Correction of LA ACLR requirements TS 38.106CR0017
- CR to 38.106: Correction of LA ACLR requirements TS 38.106CR0018
+ 9 more changes
In Release 18, the OBUE function was updated with specific corrections and clarifications for carriers with less than 5MHz bandwidth, ensuring accurate requirements for these narrow carriers. The release also introduced clarifications on OBUE limits for scenarios where a narrow carrier is positioned adjacent to the edge of a spectrum sub-block. Furthermore, new operating band unwanted emission requirements were formalized for various base station types, including repeaters and AAS base stations.
- CR to 38.104: Correction of ACLR requirements for lessthan 5MHz BW TS 38.104CR0617
- CR to TS 38.104: Clarifications on RMR terminology and related operating bands TS 38.104CR0637
- CR to 38.104: Correction of OBUE requirements for lessthan 5MHz BW TS 38.104CR0618
- CR to 38.106: NR repeater transmitter spurious emissions requirements (rel-18) TS 38.106CR0064
- CR for TS 38.106, Correction on ACLR requirement for NCR TS 38.106CR0067
- CR to 38.106: ACLR requirements for NCR TS 38.106CR0098
+ 28 more changes
In Release 19, the OBUE function saw corrections for multi-band connector scenarios and for unwanted emissions in general, alongside a specific correction to the unit of measurement for Over-the-Air Adjacent Channel Leakage Ratio (OTA ACLR). The release also clarified that for Base Stations operating in Band 41 in Japan, the operating band unwanted emissions limits apply to the sum of emission power across all antenna connectors.
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 |