Uplink Beam Selection for EVM and Link Budget Trade-offs
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Solution Overview
Problem
In millimeter wave (mmW) communication systems, beamforming can degrade the error vector magnitude (EVM) when user equipment (UE) is proximate to a base station due to coherent noise fed into multiple antenna elements, leading to signal obscuration by the noise floor, especially in regions with low power spectrum density (PSD).
Innovation Solution
The UE determines the power spectrum density (PSD) and selects either a directional beam or a wide beam for uplink signal transmission based on PSD thresholds, using a single antenna element to generate a wide beam when PSD is low to prevent EVM degradation, and switching to a directional beam when PSD is high to improve EVM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beamforming is used to generate directional beams with multiple antenna elements, then link budget is improved and fading effect is reduced, but error vector magnitude degrades in low power spectrum density regions due to coherent noise
Solution Approach 1:
The system dynamically switches between wide beam and directional beam modes based on real-time assessment of power spectrum density and distance to base station. When UE is proximate to base station (low PSD), wide beam mode is selected to avoid coherent noise. When UE is distant (high PSD), directional beam mode is selected to improve link budget. This dynamic adaptation resolves the contradiction by selecting the appropriate beam type for each operational condition.
Solution Approach 2:
The invention changes the beamforming parameters (beam width, antenna element activation) based on operating conditions. In low PSD regions, the system changes parameters to generate wide beams with fewer active antenna elements, preventing EVM degradation. In high PSD regions, parameters are changed to create narrow directional beams for improved link budget. This parameter adaptation allows the system to optimize both reliability and signal quality under different conditions.
2Reliability
If directional beams are used to reduce fading effect, then signal transmission reliability is improved, but signal is obscured by noise floor in low power spectrum density regions
Solution Approach 1:
The system changes beamforming parameters based on PSD levels. In low PSD regions, parameters are adjusted to create wide beams that illuminate larger areas with lower gain, preventing signal obscuration by noise floor. In high PSD regions, parameters are changed to create narrow directional beams with higher gain for improved signal transmission reliability. This parameter adaptation resolves the contradiction between reliability and noise floor effects.
3Manufacturing precision
If wide beam is used to prevent EVM degradation, then error vector magnitude is maintained, but link budget requirement may not be met in distant communication scenarios
Solution Approach 1:
The system dynamically selects between wide beam and directional beam modes based on real-time distance and PSD assessment. When UE is proximate to base station, wide beam mode is used to maintain EVM. When UE is distant, the system switches to directional beam mode to meet link budget requirements. This dynamic selection resolves the contradiction by matching beam type to communication distance and conditions.
Solution Approach 2:
The invention changes beamforming parameters based on operational conditions. In proximate scenarios, parameters are set for wide beams that preserve signal quality and EVM. In distant scenarios, parameters are changed to create narrow directional beams that provide sufficient gain to meet link budget requirements. This parameter adaptation allows the system to optimize both EVM and link budget under different conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively prevents EVM degradation in low PSD regions while maintaining link budget requirements, ensuring reliable signal transmission by adapting beam type based on proximity to the base station.
Implementation Method 1
the UE may apply beamforming by combining a plurality of antenna elements (e.g., elements of an antenna array) in order to steer the directional beam toward an intended target
Data Source
AI summary
In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be configured to determine a PSD based on a transmission power associated with transmission of an uplink signal. The apparatus may be configured to select one of a first beam or a second beam for the transmission of the uplink signal based on the PSD. The second beam may be wider than the first beam, and may be generated by a single antenna element of the apparatus. The apparatus may be configured to transmit the uplink signal using the selected one of the first beam or the second beam.