Receiver Equalization Using Oversampled and Fractionally Spaced Samples
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fractionally spaced equalizers in communication systems face challenges due to high complexity and power consumption, while symbol spaced equalizers are sensitive to sampling time due to non-compliance with the Nyquist criterion after pulse shaping.
Innovation Solution
A method and receiver that employ an equalization algorithm combining oversampled sampling, processing to generate symbol and fractionally spaced samples, calculating taps based on symbol spaced samples, and filtering with a fractionally spaced equalizer, which performs calculations in the frequency domain and applies anti-aliasing filtering to reduce complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fractionally spaced equalizers are used, then performance is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent changes the fundamental parameter of sampling rate from symbol rate to oversampled rate, enabling the use of simpler symbol-spaced equalizers while achieving performance comparable to complex fractionally spaced equalizers. This parameter change resolves the contradiction by allowing low-complexity implementation without sacrificing performance.
Solution Approach 2:
The patent introduces dynamic tap calculation where the equalizer taps are computed based on current channel conditions and training sequences. This dynamic adaptation allows the simple symbol-spaced equalizer to achieve performance parity with fractionally spaced equalizers through intelligent parameter adjustment rather than structural complexity.
2Device complexity
If symbol spaced equalizers are used, then device complexity is reduced, but sensitivity to sampling time increases
Solution Approach 1:
The patent applies preliminary oversampling of the received signal before equalization. This preliminary action creates a buffer that decouples the equalizer from precise timing requirements, as the oversampled data provides multiple opportunities for accurate symbol detection regardless of exact sampling moments. This resolves the timing sensitivity issue while maintaining low complexity.
Solution Approach 2:
The patent implements feedback mechanisms using training sequences and channel estimation to dynamically adjust equalizer parameters. This feedback loop compensates for sampling time variations by continuously adapting the equalizer taps based on actual channel conditions, thereby reducing sensitivity to timing errors while maintaining simple equalizer structure.
3Reliability
If oversampled sampling is applied, then sampling time sensitivity is reduced, but device complexity increases
Solution Approach 1:
The patent segments the signal processing into distinct stages: oversampling stage, channel estimation stage, and equalization stage. By separating these functions, the system achieves sampling time insensitivity through oversampling while keeping each stage relatively simple. The segmentation allows independent optimization of each stage without requiring the entire system to be complex.
Data Source
AI summary
A receiver and a method for equalizing signals, the method includes: receiving input signals; sampling the input signals to provide oversampled samples; processing the oversampled samples to provide symbol spaced samples and to provide fractionally spaced samples that represent the oversampled samples; calculating taps of a fractionally spaced equalizer based on the symbol spaced samples; feeding the taps to the fractionally spaced equalizer; and filtering the fractionally spaced samples by the fractionally spaced equalizer to provide equalized samples.