NNPR Pulse-Shaping Filters for Spectral Efficiency and ISI Trade-Offs
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Solution Overview
Problem
Existing broadband satellite communication systems face challenges in efficiently utilizing limited spectral resources due to interference and inefficiencies in pulse shaping filters, leading to increased interference and reduced spectral efficiency.
Innovation Solution
Implementing non-Nyquist partial response (NNPR) filters with tunable weighting factors to generate pulse-shaped signals that control inter-symbol interference (ISI) and optimize throughput and power penalty, using modified orthogonalization to improve spectral characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Nyquist-based pulse shaping filters are used, then inter-symbol interference is minimized, but spectral efficiency is reduced
Solution Approach 1:
The patent changes the fundamental parameter of pulse shaping by transitioning from Nyquist-based filters to non-Nyquist partial response filters. This parameter change allows the system to accept controlled amounts of inter-symbol interference in exchange for significantly improved spectral efficiency, achieving a new operating point that was not accessible with conventional filters.
Solution Approach 2:
The patent introduces dynamically adjustable weighting factors that control the trade-off between inter-symbol interference and spectral efficiency. By making the filter characteristics adjustable rather than fixed, the system can adapt to different operational requirements and optimize performance based on channel conditions and service requirements.
2Object-affected harmful factors
If pulse shaping filters are used to contain transmitted signal within available spectrum, then interference to neighboring bands is minimized, but bandwidth utilization is reduced
Solution Approach 1:
The patent employs non-Nyquist pulse shaping filters with modified spectral characteristics that allow the transmitted signal to extend beyond the traditional Nyquist bandwidth while maintaining controlled interference levels. This parameter change in filter design enables more aggressive bandwidth utilization without proportionally increasing interference to adjacent channels.
Solution Approach 2:
The patent uses weighting factors that can be adjusted based on feedback regarding spectral occupancy and interference levels. This feedback mechanism allows the system to optimize the balance between bandwidth utilization and interference management, adapting the pulse shaping characteristics to actual operating conditions.
3Productivity
If non-Nyquist waveforms are used for pulse shaping, then spectral efficiency is improved, but inter-symbol interference increases
Solution Approach 1:
The patent converts the harmful effect of inter-symbol interference into a beneficial feature by using non-Nyquist partial response filters that deliberately shape the interference in a controlled manner. The weighting factors allow the system to transform what would normally be unwanted interference into a manageable characteristic that can be optimized for spectral efficiency.
Solution Approach 2:
The patent changes the fundamental approach to inter-symbol interference by moving from Nyquist-based elimination to non-Nyquist controlled acceptance. By adjusting the weighting factors, the system can parameterize the amount of interference tolerated in exchange for spectral efficiency gains, transforming a binary choice into a continuous optimization problem.
4Ease of manufacture
If conventional pulse shaping filters are used, then implementation is straightforward, but spectral resources are not efficiently utilized
Solution Approach 1:
The patent maintains implementation feasibility by using filter structures that are parameterized through weighting factors rather than requiring completely new filter designs. This parameter-based approach allows conventional filter implementation techniques to be adapted to non-Nyquist pulse shaping, preserving ease of manufacture while achieving improved spectral resource utilization.
Data Source
AI summary
Systems and methods are described for generating and implementing pulse-shaping filters for efficient utilization of limited spectral resources in wireless communication systems. Wireless communication systems operating at high spectral efficiency conventionally use pulse shaping filters that rely on Nyquist waveforms for good main lobe performance with low inter-symbol interference (ISI) power. Conventional uses of non-Nyquist waveforms typically involve an orthogonalization process to convert those non-Nyquist waveforms to Nyquist waveforms for ISI free performance. Embodiments of pulse shaping filters described herein generate a non-Nyquist partial response (NNPR) transmit filter and/or matched receive filter based on applying a tunable second-weighted orthogonalization to a tunable first-weighted non-Nyquist waveform to obtain a pulse-shaping waveform with parametric control over throughput and power penalty.