Transmitter-End FEXT Cancellation for Signal Integrity
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Solution Overview
Problem
Current systems are inadequate in effectively canceling far-end crosstalk (FEXT) interferences due to signal attenuation and the complexity of measuring FEXT, with most solutions focusing on near-end crosstalk (NEXT) cancellation at the receiver end.
Innovation Solution
Implementing a FEXT canceller at the transmitter end, using digital signal processing with finite impulse response (FIR) filters, and combining it with analog circuits to cancel both FEXT and NEXT, with adaptation mechanisms to compensate for environmental changes, and using overhead bits for continuous adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If crosstalk cancellation is performed at the receiver end using existing techniques, then near-end crosstalk (NEXT) can be reduced, but far-end crosstalk (FEXT) cancellation remains ineffective
Solution Approach 1:
The patent inverts the conventional approach by placing the FEXT canceller at the transmitter end rather than the receiver end. The transmitter uses information obtained from the receiver (such as channel state information or error signals) to generate cancellation signals that are injected back into the transmit path, thereby canceling FEXT at its source before it reaches the far-end receiver.
Solution Approach 2:
The patent introduces an intermediary feedback mechanism where the receiver provides channel state information or error signals back to the transmitter. This intermediary information enables the transmitter to adaptively adjust its FEXT cancellation signals, creating a closed-loop system that improves cancellation effectiveness without requiring direct FEXT measurement at the far end.
2Measurement precision
If FEXT measurement is performed at the far end of the communication link, then FEXT cancellation can be achieved, but the measurement process becomes extremely time-consuming and complex
Solution Approach 1:
The patent extracts the FEXT measurement function from the far-end receiver and relocates it to the near-end transmitter. Instead of measuring FEXT at the far end where it is weak and difficult to isolate, the system uses the transmitter's position to measure and characterize the crosstalk path using known test signals or training sequences, dramatically simplifying the measurement process.
Solution Approach 2:
The patent creates a model or copy of the FEXT channel characteristics at the transmitter end using training sequences or pilot signals. By transmitting known patterns and analyzing the received signals at the near end, the system builds a mathematical model of the crosstalk path that can be used for cancellation without performing actual FEXT measurements at the far end.
3Reliability
If signal swing is increased to overpower Gaussian and power supply noises, then signal quality can be improved, but crosstalk interference increases proportionally
Solution Approach 1:
The patent converts the harmful crosstalk signals into beneficial cancellation signals. By capturing the crosstalk at the transmitter end and processing it through adaptive filters, the system generates anti-phase signals that when combined with the original transmit signals, cancel out the FEXT and NEXT components, thereby improving signal quality without increasing signal swing.
Solution Approach 2:
The patent changes the parameter of signal cancellation by introducing adaptive filter coefficients that dynamically adjust the amplitude and phase of cancellation signals. This allows the system to optimize the cancellation effect for varying channel conditions without changing the fundamental transmit signal power level, thus avoiding the trade-off between signal quality and crosstalk generation.
Data Source
AI summary
The present invention effectively cancels echo, near-end crosstalk and far-end crosstalk. A FEXT canceller is placed at the transmitter rather than at the receiver according to an aspect of the invention. In some embodiment, a FEXT canceller can be placed at the receiver only or the combination of both ends. The FEXT canceller is continuously adapted with information sent back from a remote receiver and with data from a neighbor transmitter that causes the crosstalk at the remote receiver. This allows the FEXT canceller to quickly adapt to a change in crosstalk function or conditions with the surrounding environment, for example, aging, temperature, humidity, physical pressure, etc. In some embodiments, an adaptation control signal is sent back from the receiver to the transmitter by using an overhead bit in the frame format. In some embodiments, part of the FEXT canceller is built-in at the remote receiver.