Partial Response Signaling for Nonlinear Satellite Spectral Efficiency
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Solution Overview
Problem
Conventional satellite communication systems face limitations in spectral efficiency due to constraints imposed by Nyquist's criterion for inter-symbol interference (ISI) free reception, which restricts maximum symbol rate and signal power spectrum density, prompting the need for techniques that introduce controlled ISI to enhance throughput.
Innovation Solution
The implementation of partial response signaling systems and methods in nonlinear satellite systems, utilizing new transmit and receive filters that introduce a controlled amount of ISI, allowing for a compact signal spectrum and higher channel capacity, along with a receiver design that mitigates linear and nonlinear signal distortions using a turbo-Volterra receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Nyquist signaling criterion is used to ensure ISI-free reception, then reception reliability is improved, but spectral efficiency deteriorates due to constraints on maximum symbol rate and signal power spectrum density
Solution Approach 1:
The patent converts the harmful effect of ISI into a beneficial tool by deliberately introducing controlled ISI through partial response signaling. The transmit filter is designed to create specific ISI patterns that are then compensated at the receiver, allowing higher symbol rates and improved spectral efficiency while maintaining acceptable error performance through iterative detection and cancellation techniques.
Solution Approach 2:
The patent changes the signaling parameters by using partial response signaling with memory L>0, which modifies the pulse shaping filter characteristics to introduce controlled ISI. The system adjusts the roll-off factor and filter memory to optimize the trade-off between spectral compactness and ISI introduction, enabling higher spectral efficiency compared to conventional Nyquist signaling.
2Productivity
If higher symbol rates are used to improve spectral efficiency, then productivity is improved, but inter-symbol interference increases causing deterioration in reception reliability
Solution Approach 1:
The patent implements feedback mechanisms through iterative detection and interference cancellation. The receiver uses soft information from channel decoding to estimate and cancel ISI, feeding this information back into the detection process. This iterative feedback loop allows the system to maintain high symbol rates while compensating for the introduced ISI, thereby preserving reception reliability.
Solution Approach 2:
The patent applies preliminary action by pre-compensating for ISI through carefully designed partial response transmit filters. The filter characteristics are predetermined to create specific ISI patterns that can be effectively canceled at the receiver, allowing the system to operate at higher symbol rates without suffering from uncontrolled ISI degradation.
3Reliability
If conventional RRC filters are used to satisfy Nyquist criterion, then ISI-free reception is achieved, but signal spectrum occupies more bandwidth reducing spectral efficiency
Solution Approach 1:
The patent changes the filter parameters by using partial response signaling with memory L>0 instead of conventional RRC filters. The transmit filter is designed with specific coefficients that create a compact spectrum while introducing controlled ISI. This parameter change allows the signal to occupy less bandwidth while maintaining acceptable error performance through iterative cancellation at the receiver.
Solution Approach 2:
The patent converts the spectrum occupancy issue into an opportunity by deliberately designing filters that create compact spectra with controlled ISI. The introduced ISI is not treated as a problem to be eliminated but as a characteristic to be managed and compensated, allowing more efficient spectral utilization compared to conventional ISI-free signaling.
4Productivity
If partial response signaling is implemented to improve spectral efficiency, then productivity is improved, but system complexity increases due to need for sophisticated receiver processing
Solution Approach 1:
The patent segments the receiver processing into distinct functional blocks: partial response filter, matched filter, soft decision detector, and iterative cancellation module. This segmentation allows each component to be optimized independently and facilitates implementation using standard digital signal processing techniques, reducing overall system complexity while maintaining the benefits of partial response signaling.
Solution Approach 2:
The patent introduces soft information as an intermediary between the detector and the interference cancellation module. This soft information carries probabilistic information about the transmitted symbols, allowing the receiver to perform sophisticated ISI cancellation without requiring hard decisions. The intermediary soft information enables gradual refinement of symbol estimates across multiple iterations, managing complexity effectively.
Data Source
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AI summary
New partial response signaling systems and methods for high spectral efficiency communications are described. In a first implementation, a communication system includes a partial response signaling transmitter and a nonlinear satellite transponder. The partial response signaling transmitter includes a partial response transmit filter configured to convert complex- valued data symbols to a transmit signal using a partial response pulse shaping function; and a modulator configured to modulate the transmit signal onto a carrier wave. The transponder receives and non-linearly amplifies the modulated transmit signal for broadcast to receivers. In a second implementation, a receiver includes circuitry for downconverting a received input signal; a partial response filter with a partial response impulse function for filtering the downconverted signal; circuitry for downsampling the partial response filtered signal; circuitry for equalizing the downsampled signal; and a linear and non-linear interference cancellation module including circuitry for removing linear and non-linear ISI in the input signal.