Antenna Calibration via Downlink Channel Weighting
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Solution Overview
Problem
In wireless communication systems, especially in MIMO and CoMP environments, the existing antenna calibration methods require significant uplink overhead for channel feedback, leading to inefficiencies and potential quantization errors, which degrade system performance due to mismatched transmitter and receiver circuits and lack of reciprocity between uplink and downlink channels.
Innovation Solution
The proposed method involves a user equipment performing downlink channel measurement and determining a first weight matrix through eigenvalue decomposition, which is then quantized and reported to the network side for antenna calibration, reducing uplink overhead and enabling efficient calibration between base stations, even in TDD systems without strict channel reciprocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE feeds back channel information over the uplink channel, then the base station can obtain channel state information for transmission optimization, but the uplink channel resources are significantly consumed and quantization errors are introduced
Solution Approach 1:
The patent introduces a calibration factor as an intermediary element that mediates between the uplink and downlink channels. Instead of directly feeding back channel state information, the UE measures the downlink channel and feeds back a calibration factor that compensates for the mismatch between transmitter and receiver circuits. This intermediary approach allows the base station to obtain accurate channel state information without consuming significant uplink resources or introducing quantization errors.
2Adaptability or versatility
If the transmitter and receiver circuits are used separately for uplink and downlink, then the system can operate independently in each direction, but temporal delays and amplitude gains differ causing circuit mismatch and breaking channel reciprocity
Solution Approach 1:
The patent implements a feedback mechanism where the UE measures the downlink channel and feeds back measurement results to the base station. The base station uses this feedback to calculate calibration factors that compensate for the circuit mismatch. This feedback loop enables the system to maintain channel reciprocity despite using separate transmitter and receiver circuits for uplink and downlink operations.
3Reliability
If antenna calibration is performed using existing methods, then the mismatch between circuits can be compensated, but significant uplink overhead is required for channel feedback
Solution Approach 1:
The patent extracts only the essential calibration information from the full channel state information. Instead of feeding back the entire channel matrix, the system extracts and feeds back only the calibration factor, which contains the necessary information to compensate for circuit mismatch. This extraction approach significantly reduces uplink overhead while maintaining effective calibration.
4Quantity of substance
If TDD system uses uplink channel estimation for downlink transmission, then feedback overhead is reduced, but the mismatch between transmitter and receiver circuits makes strict reciprocity inapplicable
Solution Approach 1:
The patent changes the parameter representation from direct channel state information to calibration factors. By transforming the calibration problem into a parameter optimization task, the system can use uplink channel estimates combined with calibration factors to achieve accurate downlink transmission. This parameter transformation allows TDD systems to maintain reciprocity-based operation while compensating for circuit mismatches.
Data Source
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Figure 1B
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AI summary
An embodiment of the present invention relates to the technical field of wireless communications, in particular to an aerial calibration method, system and device. In the prior art, an air interface calibration method involving a user equipment (UE) requires the UE to feed back a channel coefficient, and a channel coefficient direct quantization method occupies a great deal of uplink overhead and reduces system efficiency. The present invention solves the above problem. The method in the embodiment of the present invention comprises: the UE measures a downlink channel and determines a downlink channel matrix; the UE determines a first weighting matrix for aerial calibration according to the downlink channel matrix; the UE notifies a network side of the determined first weighting matrix. In the embodiment of the present invention, a UE decomposes the characteristic value of the downlink channel matrix, or reports the identifier corresponding to the first weighting matrix to the network side device, thus reducing the occupied uplink overhead and improving system efficiency.