Link-Adaptation Power Backoff for Beamforming Saturation
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Solution Overview
Problem
Advanced antenna systems (AAS) with beamforming face challenges in predicting received power and SINR, leading to potential saturation and interference issues, as traditional power control methods are not effective in optimizing power allocation for beamformed signals.
Innovation Solution
Implementing link-adaptation (LA) power backoff techniques that adjust transmit power and modulation and coding schemes based on Hybrid Automatic Repeat reQuest (HARQ) indications, allowing for dynamic power management and interference reduction by switching between power backoff and conventional LA modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmit power is increased to improve SINR, then signal quality is improved, but receiver saturation and performance degradation occur
Solution Approach 1:
The system performs preliminary calibration to determine saturation thresholds before actual transmission. The network node pre-configures maximum useful receive power levels and uses these thresholds to control transmit power, preventing receiver saturation before it occurs.
Solution Approach 2:
The system implements feedback mechanisms where the wireless device reports received power measurements and saturation conditions back to the network node. The network node adjusts transmit power based on this feedback, creating a closed-loop control system that prevents saturation while maintaining optimal SINR.
2Reliability
If beamforming is used to increase gain and SINR, then signal quality is improved, but received power becomes difficult to predict and control
Solution Approach 1:
The wireless device performs self-measurement of received power and autonomously determines saturation conditions. Instead of relying on network predictions, the device monitors its own receiver chain saturation and reports actual measurements back to the network node for power adjustment.
Solution Approach 2:
The system dynamically changes transmit power parameters based on beamforming gain measurements. The network node adjusts power levels according to measured beamforming effectiveness and reported saturation conditions, adapting parameters in real-time to maintain optimal performance.
3Ease of operation
If constant transmit power is used, then power control is simple, but interference cannot be optimized for beamformed signals
Solution Approach 1:
The system transitions from constant power to dynamic power adjustment. The network node varies transmit power across different time intervals and beams based on reported saturation conditions and interference measurements, optimizing power allocation while maintaining simple operation through automated control.
Solution Approach 2:
The system applies different power levels to different beams and time intervals based on local conditions. Each beamformed transmission receives optimized power control tailored to its specific direction and interference environment, rather than using uniform power across all transmissions.
4Reliability
If maximum power is transmitted intermittently with beamforming, then SINR is improved in targeted directions, but the 'flashlight effect' creates sudden interference
Solution Approach 1:
The system applies preliminary power backoff based on predicted interference impact. Before transmitting high-power beamformed signals, the network node calculates potential interference to other users and pre-reduces power levels to prevent harmful flashlight effects, while still achieving adequate SINR through optimized beamforming.
Data Source
AI summary
Apparatuses and methods are disclosed for link-adaptation (LA) power backoff for beamforming. In one embodiment, a method in a network node includes triggering a link adaptation for a channel transmission, the link adaptation comprising adjusting a transmit power of the channel transmission based at least in part on whether a previous channel transmission was correctly decoded. In another embodiment, a method in a wireless device includes receiving a downlink, DL, channel transmission at a first transmit power value; and transmitting a message to a network node, the message indicating a power saturation condition as a result of the first transmit power value.