FDR Self-Interference Channel Estimation via DFT Reference Signals
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Solution Overview
Problem
In full-duplex radio (FDR) systems, intra-device self-interference significantly deteriorates performance, and existing methods struggle to efficiently estimate and cancel non-linear self-interference signals, particularly due to high-order inter-modulation distortion components generated by non-linear device properties.
Innovation Solution
A method is introduced for transmitting reference signals for channel estimation of non-linear self-interference signals, where the reference signals are subjected to discrete Fourier transform (DFT) and mapped to the frequency domain, allowing for efficient channel estimation by allocating them on specific symbols of subframes, such as the fourth symbol, and potentially across full bandwidth or specific bands, with zero insertion as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If reference signals are transmitted in conventional half-duplex communication, then channel estimation can be performed, but full-duplex system capacity cannot be achieved due to self-interference
Solution Approach 1:
The patent converts the harmful self-interference signal into a useful resource by transmitting reference signals during the same time-frequency resources as the desired signal. The self-interference channel characteristics are estimated using these reference signals, enabling the interference to be characterized and potentially cancelled, thereby allowing full-duplex operation with improved system capacity.
Solution Approach 2:
The patent performs channel estimation for self-interference signals by transmitting reference signals before the actual communication takes place. This preliminary action allows the system to characterize the self-interference channel properties in advance, enabling subsequent interference cancellation to be performed more effectively during normal operation.
2Measurement precision
If reference signals are transmitted on every symbol, then channel estimation accuracy is improved, but overhead and interference with data transmission increase
Solution Approach 1:
The patent segments the reference signal transmission into specific time-frequency resources rather than transmitting continuously. Reference signals are transmitted on specific symbols (e.g., first and last symbols of a subframe) rather than all symbols, which reduces overhead while still providing sufficient information for accurate channel estimation through the auto-correlation and cross-correlation properties of the reference signal sequence.
Solution Approach 2:
The patent makes the reference signal sequence serve multiple functions: it enables channel estimation for both the desired signal and the self-interference signal simultaneously. The same reference signal transmission provides the necessary information to characterize both channels, eliminating the need for separate reference signals and reducing overall system complexity.
3Reliability
If non-linear self-interference cancellation is performed, then FDR performance is improved, but estimation complexity increases due to high-order inter-modulation distortion
Solution Approach 1:
The patent replaces complex time-domain non-linear signal processing with frequency-domain correlation-based estimation. By transforming the self-interference signal to the frequency domain and using auto-correlation and cross-correlation properties of the reference signal sequence, the system can estimate channel characteristics without performing computationally intensive non-linear cancellation operations in the time domain.
Solution Approach 2:
The patent uses reference signal sequences that have known auto-correlation and cross-correlation properties to create copies of the channel characteristics. These correlation properties allow the system to estimate self-interference channel parameters by measuring the correlation between reference signals and received signals, providing a simplified approach compared to direct non-linear signal copying and cancellation.
Data Source
AI summary
A method for a FDR scheme-using communication device transmitting reference signals for estimating a channel of a non-linear self-interference signal comprises the step of transmitting, on a specific symbol of a corresponding subframe, reference signals for estimating the channel of the non-linear self-interference signal, wherein a sequence mapped to the reference signals is a sequence generated in a frequency domain by being discrete Fourier transform (DFT)-converted, and the generated sequence may be mapped, on the frequency domain, to a RE for the reference signals.