Receiver Sequence Detection With Pseudo Partial Response Equalization
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Solution Overview
Problem
High-rate signaling in digital communications receivers faces challenges with intersymbol interference (ISI) and noise, where existing equalizers like linear and decision feedback equalizers fail to provide low error rates, and maximum likelihood sequence detectors (MLSD) are prohibitively complex for multibit symbols.
Innovation Solution
The implementation of a reduced-complexity maximum likelihood sequence detector (rMLSD) with pseudo partial response equalization, which includes a feedforward equalizer, decision element, and filter to diminish ISI and apply partial response to the equalized signal for input to the MLSD, reducing complexity by considering only initial and competing symbol decisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If maximum likelihood sequence detector (MLSD) is used for optimal error rate detection, then detection accuracy is improved, but device complexity and power consumption become prohibitive for multibit symbols
Solution Approach 1:
The patent segments the detection process into two stages: first, a simplified detector provides initial symbol decisions, and second, a reduced-complexity MLSD processes only the most likely candidates (initial decisions and competing decisions). This segmentation maintains detection accuracy while dramatically reducing complexity by avoiding exhaustive evaluation of all possible symbol sequences.
Solution Approach 2:
The patent applies partial MLSD by evaluating only a subset of possible symbol sequences - specifically, only the initial symbol decisions and competing symbol decisions - rather than performing complete MLSD on all possible sequences. This partial action achieves sufficient detection accuracy for practical applications while reducing computational burden.
2Device complexity
If linear equalizers or decision feedback equalizers are used for low complexity equalization, then device complexity is reduced, but bit error rates increase at high data rates
Solution Approach 1:
The patent merges the advantages of simple equalizers with the benefits of MLSD by combining a low-complexity equalizer (linear or DFE) with a reduced-complexity MLSD stage. The equalizer provides initial symbol decisions, and the MLSD refines these decisions by evaluating competing sequences, achieving low error rates without the full complexity of traditional MLSD.
Solution Approach 2:
The patent introduces an intermediary stage between simple equalization and full MLSD. The equalizer acts as an intermediary that produces initial symbol decisions, which are then refined by the reduced-complexity MLSD. This intermediary approach enables the system to achieve MLSD-level performance with significantly reduced complexity.
Data Source
AI summary
Receivers and receiving methods having maximum likelihood sequence detection with pseudo partial response equalization. One illustrative receiver includes: a feedforward equalizer that produces an equalized receive signal by diminishing a receive signal's intersymbol interference; a decision element that derives initial symbol decisions from samples of the equalized receive signal; and a filter that applies a partial response to the equalized receive signal or to an equalization error signal to produce input for a maximum likelihood sequence detector (MLSD). The MLSD may be a reduced complexity detector that derives a final sequence of symbol decisions by evaluating state metrics only for each initial symbol decision and its competing symbol decision.