E-UTRA Adjacent Channel Leakage Ratio

Description

E-UTRA Adjacent Channel Leakage Ratio (E-UTRAACLR) is a radio frequency (RF) performance metric introduced in 3GPP Release 19 to quantify the amount of power that leaks from an E-UTRA (LTE) carrier into adjacent channels. It is defined in specifications 38.101 (NR UE radio transmission and reception) and 38.521 (NR UE conformance testing), which are part of the 5G NR specifications. E-UTRAACLR is critical for ensuring coexistence between LTE and 5G NR in the same frequency band, as well as minimizing interference with other systems.

In multi-RAT deployments, a user equipment (UE) may transmit LTE and NR signals simultaneously, either in the same band (intra-band) or in different bands (inter-band). The E-UTRAACLR metric specifies the maximum allowed leakage from the E-UTRA carrier into the adjacent NR or LTE channel. This is particularly important for dual-connectivity scenarios (EN-DC, NE-DC) and for spectrum sharing between LTE and NR. The metric is measured as the ratio of the transmitted power in the E-UTRA channel to the power measured in an adjacent channel after filtering, expressed in dB.

The E-UTRAACLR requirements are defined for various UE power classes and frequency bands, taking into account the modulation scheme, bandwidth, and resource block allocation. The UE must meet these requirements to ensure that its transmissions do not cause harmful interference to other channels. Compliance is verified through conformance testing as specified in 38.521, which outlines the test procedures and measurement setups.

Architecturally, E-UTRAACLR is a UE RF performance requirement that impacts the design of the UE's power amplifier, filters, and duplexers. It also influences network planning and spectrum allocation, as operators must ensure that adjacent channel interference is kept within acceptable limits. The metric is closely related to other ACLR metrics, such as NR ACLR and UTRA ACLR, which apply to NR and UMTS carriers respectively.

In Release 19, E-UTRAACLR was introduced to address the specific challenges of LTE-NR coexistence in 5G-Advanced networks. As operators refarm spectrum from LTE to NR, the need for precise ACLR requirements for E-UTRA signals becomes more pronounced. The specification ensures that UEs can operate efficiently in multi-RAT environments without degrading network performance.

Purpose & Motivation

E-UTRAACLR was created to address the need for clear RF performance requirements for LTE signals in 5G NR deployments. As 5G networks are rolled out, many operators are refarming LTE spectrum for NR or deploying both technologies in the same band. Without proper ACLR specifications, interference between LTE and NR carriers could degrade network performance and user experience.

Previous 3GPP releases defined ACLR for LTE (in 36.101) and NR (in 38.101), but the interaction between the two in multi-RAT scenarios required additional clarification. E-UTRAACLR provides a unified metric that ensures LTE transmissions do not exceed acceptable leakage levels into adjacent NR or LTE channels. This is essential for dynamic spectrum sharing (DSS) and dual-connectivity, where LTE and NR signals coexist in the same band.

The introduction of E-UTRAACLR in Release 19 reflects the maturity of 5G deployments and the need for precise coexistence requirements. It enables operators to maximize spectral efficiency while maintaining quality of service, and it provides UE vendors with clear design targets for multi-RAT capable devices.