Feedforward Noise Cancellation for Optical Receivers
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Solution Overview
Problem
Current noise cancellation techniques in optical fiber links suffer from high latency and require feedback connections, training symbols, and large overhead, which are critical issues in latency-sensitive systems and complex architectures.
Innovation Solution
A feedforward noise cancellation device and method that predicts noise samples from both preceding and succeeding signal samples in a buffer, eliminating the need for feedback connections and reducing latency, while improving bit error rate (BER) without requiring training symbols or large overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback connections are used in noise cancellation, then noise cancellation performance is improved, but latency increases and system complexity increases
Solution Approach 1:
The patent inverts the conventional feedback-based noise cancellation approach by using a feedforward structure. Instead of using past decisions to cancel noise in current samples (feedback), the invention uses predicted noise from both preceding and succeeding samples in a feedforward manner, eliminating the need for feedback connections and reducing latency.
Solution Approach 2:
The patent performs preliminary noise prediction by calculating predicted noise samples from both preceding and succeeding signal samples before making the final decision on the modulation level. This preliminary action allows noise cancellation to occur without waiting for feedback, thereby reducing latency while maintaining performance.
2Reliability
If feedback connections are used in noise cancellation, then noise cancellation performance is improved, but device complexity increases
Solution Approach 1:
The patent eliminates feedback connections by inverting the conventional approach to noise cancellation. The feedforward structure using predicted noise from preceding and succeeding samples removes the need for complex feedback loops, decision buffers, and synchronization mechanisms, thereby reducing device complexity while maintaining noise cancellation performance.
3Measurement precision
If training symbols and large overhead are used, then equalization performance is improved, but productivity decreases
Solution Approach 1:
The patent enables the noise cancellation device to serve itself by using the actual signal samples (both preceding and succeeding) to predict and cancel noise. This self-service approach eliminates the need for external training symbols or large overhead, allowing continuous data transmission without performance degradation.
4Device complexity
If only preceding samples are used for noise prediction, then device complexity is reduced, but noise cancellation performance deteriorates
Solution Approach 1:
The patent extends noise prediction from one dimension (only preceding samples) to two dimensions by incorporating both preceding and succeeding samples. This dimensional expansion allows the system to capture noise characteristics more comprehensively, improving noise cancellation performance while maintaining manageable complexity through a symmetric structure.
Data Source
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AI summary
The present invention relates to noise cancellation in systems using equalization to cope with strong intersymbol interference. In particular, the invention presents a noise cancelling (NC) device and method for a receiver. The NC device is configured to hold a plurality of samples of a signal in a buffer. Further, the NC device is configured to make a decision on a modulation level of each of N ≥ 1 samples successively arranged in the buffer, wherein the decision for a given sample of the N samples is made based on: the given sample; a first predicted noise sample, predicted from K ≥ 1 other samples arranged before the given sample in the buffer; and a second predicted noise sample, predicted from M ≥ 1 other samples arranged after the given sample in the buffer. The NC device may have low latency and low complexity.