Antenna Array Channel Characterization Without Feedback
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Solution Overview
Problem
Current cellular networks face challenges in estimating downlink channels without channel feedback, especially in large MIMO systems where the overhead of feedback is excessive, and existing methods like channel reciprocity are not applicable due to Frequency Division Duplexing used in most cellular connections.
Innovation Solution
A method that characterizes transmit channels from an antenna array to a transceiver by computing receive and transmit channel characteristics using received transmissions, allowing for the estimation of downlink channels without requiring the same frequencies for transmission and reception or channel feedback, leveraging frequency-invariant signal path representations and Fourier transforms to infer channels in different frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If channel feedback is used to estimate downlink channels, then channel estimation accuracy is improved, but feedback overhead becomes excessive
Solution Approach 1:
Instead of having the remote device measure downlink channels and feed back to the base station, the invention inverts the approach by having the base station measure uplink channels and use channel reciprocity to infer downlink channels. This eliminates the need for feedback while achieving accurate channel estimation.
Solution Approach 2:
The base station uses its own uplink measurements and channel reciprocity properties to independently estimate downlink channels without requiring assistance or feedback from the remote device. The system serves itself by leveraging the symmetry in the channel characteristics.
2Reliability
If channel feedback is used in large MIMO systems, then beamforming performance is improved, but processing requirements and time delays increase
Solution Approach 1:
The base station performs preliminary measurements of uplink channels and computes channel characteristics in advance. By pre-characterizing the channels using uplink transmissions, the system eliminates the need for time-consuming feedback loops while maintaining accurate beamforming performance.
3Quantity of substance
If channel reciprocity is used to estimate downlink channels, then feedback overhead is reduced, but applicability is limited to TDD systems
Solution Approach 1:
The invention changes the fundamental parameter approach by measuring channels at one frequency (uplink) and using frequency-invariant signal path representations to infer channels at different frequencies (downlink). This allows the method to work across different frequency bands without requiring the same frequency for both transmissions.
Data Source
AI summary
Characteristics of channels from an antenna array to a transceiver are characterized based on reciprocity in an approach that eliminates a need for channel feedback from the transceiver. In some embodiments, these channel characteristics are used in MIMO communication to a plurality of transceivers from the antenna array.