Phase Error Compensation for 5G Downlink Antennas
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Solution Overview
Problem
Fifth Generation (5G) downlink systems with four correlated and uncalibrated antennas face beam misalignment issues due to phase errors, leading to poor performance when using the NR type I codebook, which assumes beams from two polarizations always point to the same direction.
Innovation Solution
Applying N incremented phase rotations to one of the four antennas to produce N channel state information reference signal (CSI-RS) resources, transmitting these on 4 CSI-RS ports, and receiving a CSI-RS resource indication to apply the corresponding phase rotation, thereby compensating for phase errors and improving beam alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If antennas are calibrated to achieve beamforming gain, then beam alignment is improved, but system cost increases
Solution Approach 1:
The system performs self-calibration by having the wireless device measure phase differences between antennas and feed back compensation information. The network node automatically applies phase rotations to compensate for calibration errors without requiring manual calibration hardware, enabling the system to correct its own phase misalignment.
Solution Approach 2:
The patent implements a feedback mechanism where the wireless device measures channel state information, determines phase differences between antennas, and feeds back compensation parameters to the network node. The network node then applies these compensation parameters to correct beam misalignment, creating a closed-loop system that continuously improves beamforming performance.
2Device complexity
If NR type I codebook is used assuming beams align, then codebook complexity is reduced, but performance deteriorates due to phase errors
Solution Approach 1:
The patent transforms the static codebook approach into a dynamic system by introducing phase rotation parameters that can be adjusted based on measured phase differences. Instead of using a fixed codebook that assumes perfect alignment, the system dynamically adapts the beamforming weights to account for actual phase errors, maintaining performance without requiring an exponentially larger codebook.
Solution Approach 2:
The patent modifies the codebook parameters by introducing phase rotation factors that compensate for calibration errors. Rather than expanding the codebook to cover all possible phase error combinations, the system changes the parameters of existing codebook entries through phase rotation, achieving performance improvement with minimal additional complexity.
3Reliability
If phase errors are compensated through exhaustive codebook combinations, then beam alignment is improved, but search complexity increases
Solution Approach 1:
Instead of exhaustively searching all possible phase compensation combinations, the patent uses a partial approach where the wireless device measures phase differences and computes specific compensation parameters. This partial action approach achieves sufficient beam alignment without the computational burden of exhaustive search, reducing complexity while maintaining performance.
Data Source
AI summary
A method, network node and wireless device for phase error compensation for Fifth Generation downlink systems with four correlated uncalibrated antennas are provided. A method includes applying N incremented phase rotations to one of the four antennas to produce N channel state information reference signal resources, N being an integer greater than 1. The method also includes transmitting N CSI-RS on 4 CSI-RS ports to a wireless device, WD, each of the N CSI-RS resources being transmitted with a different one of the incremented phase rotations. The method further includes receiving from the WD a CSI-RS resource indication that indicates a particular one of the N CSI-RS resources. The method also includes applying, in subsequent transmissions to the WD, a phase rotation to the one of the four antennas, the phase rotation corresponding to the indicated CSI-RS resource.