Two-Way Beamforming Calibration for 5G NR
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G NR, face challenges in calibrating hybrid beamforming weights for uplink and downlink communications due to differences in radio frequency pathways and circuitry, requiring offline calibration procedures that are inefficient and unreliable, especially as the number of antenna elements increases.
Innovation Solution
A two-way hybrid beamforming operation is implemented for online calibration, where a user equipment (UE) receives reference signals, estimates a complex-valued beamformed channel, and computes calibration adjustment factors based on feedback signals to adjust beamforming weights dynamically, allowing for real-time calibration of both transmit and receive paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If offline calibration procedures are used to calibrate hybrid beamforming weights, then calibration can be performed, but the process is inefficient and unreliable, especially as the number of antenna elements increases
Solution Approach 1:
The patent transitions from static offline calibration to dynamic online calibration that occurs continuously during normal communication operations. The calibration process is performed dynamically by adjusting beamforming weights in real-time based on feedback signals exchanged between UE and network entity, making the calibration adaptive to changing channel conditions rather than a one-time static process
Solution Approach 2:
The patent implements a feedback mechanism where the network entity provides feedback signals containing measurements of reference signals transmitted by the UE. The UE uses these feedback signals to compute calibration adjustment factors that are applied to correct discrepancies between uplink and downlink beamforming weights, creating a closed-loop calibration system that continuously improves accuracy
2Adaptability or versatility
If the number of antenna elements is increased to improve communication performance, then beamforming capability is enhanced, but the complexity of calibration increases significantly
Solution Approach 1:
The patent enables the UE to perform self-calibration by autonomously transmitting reference signals and processing feedback signals to compute its own calibration adjustment factors. This self-service approach eliminates the need for complex manual calibration procedures and allows the system to automatically adapt to the increased number of antenna elements without proportionally increasing operational complexity
Solution Approach 2:
The patent changes the calibration parameters from fixed offline values to dynamic adjustment factors that are computed based on actual channel conditions. By expressing calibration as adjustments to beamforming weights rather than absolute value assignments, the system can handle increased numbers of antenna elements more efficiently, as only the necessary adjustment factors need to be computed rather than complete recalibration of all parameters
3Adaptability or versatility
If hybrid beamforming is used to support both uplink and downlink communications, then communication versatility is improved, but discrepancies in radio frequency pathways create calibration challenges
Solution Approach 1:
The patent segments the calibration process into separate uplink and downlink components by using dedicated reference signals for each direction. The UE transmits uplink reference signals and receives downlink reference signals separately, allowing independent calibration of each pathway's beamforming weights while maintaining the hybrid beamforming capability for both directions
Solution Approach 2:
The patent introduces feedback signals as an intermediary mechanism that carries measurements of the downlink reference signals back to the UE. These feedback signals serve as a mediator that enables the UE to compare and adjust its uplink beamforming weights against the known downlink characteristics, resolving the pathway discrepancy issue without compromising communication versatility
Data Source
AI summary
Method and apparatus for two-way beamforming operations for calibration. The apparatus receives a first set of reference signals from a network node using N sets of beam weights over N symbols. The apparatus estimates a complex-valued beamformed channel based on the first set of reference signals. The apparatus transmits a second set of reference signals to the network entity using the N sets of beam weights. The apparatus receives a set of feedback signals from the network entity comprising measurements of the transmitted second set of reference signals. The apparatus computes a set of calibration adjustment factors between transmit and receive parts of a set of beam weights based on the set of feedback signals and the estimated complex-valued beamformed channel. The apparatus performs a calibration adjustment operation based on the computed set of calibrated adjustment factors.