Evaluation of the effects of 3GPP-specific beamforming and channel estimation on the 3D EIRP profile of a 5G gNB

TL;DR

This paper evaluates the 3D EIRP profile of 5G gNBs using 3GPP Release-18 standards, revealing practical impacts of beamforming and nulling techniques on interference and link performance.

Contribution

It provides the first empirical assessment of 3D EIRP in 5G gNBs, highlighting implementation-dependent factors and proposing effective beam nulling methods.

Findings

Interference depends on various beam directions due to side-lobes.

AAS architecture significantly influences average 3D EIRP.

Beam nulling achieves 11 dB power reduction with 3.5-4.5 dB SNR loss.

Abstract

Spatial domain exploitation through 3D beamforming serves as a critical technology enabler for performance enhancement in the Fifth Generation New Radio (5G NR) specification. This is realized at the gNodeB (gNB) through the integration of massive antenna element arrays that facilitates 3D spatial multiplexing. However, these systems with high-directional transmissions also represent a threat to incumbent services such as radar and satellites. These incumbents already operate in midband spectrum\textemdash{}including the 4.4-4.9 GHz and 7.125-7.4 GHz bands\textemdash{}that are currently being evaluated for future cellular deployments. Here, we present the first work that evaluates the transmitted Effective Isotropic Radiated Power (EIRP) of a gNB in 3D space, using the 3GPP Release-18 standard for FR-1 instead of theoretical analyses of beam nulling, which can be simplistic. We shed light on the problems requiring attention with the EIRP profile in 3D space for existing codebook designs predefined in 3GPP: i) interference from a gNB does not depend only on the worst-case beamforming direction, but on a variety of beamforming directions due to side-lobes; ii) advanced antenna systems (AAS) architecture and antenna port configurations play a crucial role in average 3D EIRP, which are implementation dependent, and iii) we introduce two beam nulling methods, which achieve a 11 dB power reduction toward a target direction, with 3.5-4.5 dB SNR loss in UE link performance at a 10^{-4} bit error rate (BER) across modulation schemes under ideal and practical channel estimation, a higher loss compared to predictions from theoretical analyses.