In-band Relay Gain via Adaptive Echo Cancellation
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Solution Overview
Problem
Current amplify-and-forward relays in wireless communications suffer from noise amplification and self-echo, leading to oscillation and limited relay gain, which is exacerbated by the need for physical separation of antennas, increasing costs and limiting their applicability.
Innovation Solution
The method involves performing antenna beamforming to identify settings that improve signal-to-noise ratio and self-interference channel isolation, combined with adaptive echo cancellation in the analog domain to reduce self-interference and increase relay gain without causing oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If physical separation between incoming and outgoing antennas is increased to reduce self-echo, then oscillation is avoided, but device complexity and cost increase
Solution Approach 1:
An adaptive echo cancellation circuit is introduced as an intermediary component between the transmit and receive signal paths. This circuit actively cancels self-echo through adaptive filtering, allowing antennas to be placed in close proximity without causing oscillation, thus resolving the contradiction between compact design and oscillation avoidance
Solution Approach 2:
The self-echo cancellation function is extracted from the physical antenna separation requirement and implemented as a separate signal processing function. By taking out the echo cancellation capability and implementing it electronically through adaptive filtering, the system achieves oscillation avoidance without requiring increased physical distance between antennas
2Power
If relay gain is increased to improve signal amplification, then noise amplification and self-echo oscillation occur, but signal quality deteriorates
Solution Approach 1:
An adaptive echo cancellation circuit with feedback mechanism is implemented to continuously monitor and cancel self-echo in the receive signal path. This feedback loop allows the system to maintain high relay gain while actively suppressing oscillation, resolving the contradiction between power amplification and harmful feedback effects
Solution Approach 2:
The self-echo, which is normally a harmful feedback effect limiting relay gain, is converted into a useful signal source for training the adaptive filter. By using the echoed signal to train the cancellation circuit, the system transforms the harmful oscillation problem into a beneficial training mechanism that enables stable high-gain operation
3Measurement precision
If antenna elements are increased to improve signal-to-noise ratio, then device complexity and manufacturing cost increase
Solution Approach 1:
Multiple antenna elements are merged into a phased array configuration with shared signal processing circuitry. By combining the functionality of multiple antennas and their processing circuits into an integrated array system, the achieve improved signal-to-noise ratio through coherent combining while reducing overall device complexity and manufacturing cost compared to independent antenna systems
Data Source
AI summary
A method and system is disclosed for operating an in-band relay to receive and amplify an incoming radio frequency signal and forward the amplified radio frequency signal. Methods to improve isolation between receive and transmit front-ends are disclosed, enabling an increase in the amplification gain without causing oscillation. Methods for learning the impulse response of the self-interference channel, and methods to perform adaptive echo cancellation in the analog domain. In addition, methods for transmit and receive beamforming are presented that achieve two objectives: (1) Improve the signal-to-noise ratio of the relayed signal, thereby compensating for noise amplification. (2) Improve the isolation, thereby enabling to increase the relay gain without causing oscillation.