Adaptive LDPC and Raptor Coding for Noisy Channel Throughput
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Solution Overview
Problem
Current wireless communication coding techniques, such as LDPC and Raptor codes, face challenges in achieving optimal throughput and error correction, especially in noisy channels and varying signal conditions, with irregular LDPC codes performing variably and computational complexity being a concern.
Innovation Solution
Dynamic adjustment of transmission parameters, including power and bit fraction, based on receiver feedback signals indicating channel quality, to optimize LDPC and Raptor code performance, with the use of linear programming to maximize throughput and adhere to constraints such as signal-to-noise ratio and bit erasure rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If puncturing is employed to increase transmitted bit rate, then throughput is improved, but error correction capability deteriorates
Solution Approach 1:
The patent applies dynamic puncturing where the puncturing pattern is adjusted based on channel conditions and feedback from the receiver. The system dynamically selects which bits to transmit in each interval, transitioning from static to dynamic operation to optimize both throughput and error correction under varying conditions
Solution Approach 2:
The system changes transmission parameters including the fraction of codeword bits transmitted and power levels based on receiver feedback signals indicating channel quality. This parameter adjustment allows the system to adapt the puncturing rate and pattern to maintain error correction capability while maximizing throughput
2Reliability
If irregular LDPC codes are used to improve performance, then error correction is enhanced, but computational complexity increases
Solution Approach 1:
The patent segments the LDPC code into multiple intervals with different puncturing patterns. This segmentation allows the use of irregular LDPC structures to improve error correction while managing computational complexity through structured division of the coding process into manageable segments
Solution Approach 2:
The system dynamically adjusts the irregularity pattern of the LDPC code based on channel conditions. The degree of irregularity and the specific connection patterns between variable and check nodes are adapted in real-time to optimize error correction performance while controlling decoding complexity
3Productivity
If more codeword bits are transmitted in each interval, then throughput increases, but signal-to-noise ratio requirement increases
Solution Approach 1:
The patent jointly optimizes the fraction of codeword bits transmitted and the power level as coupled parameters based on receiver feedback. When channel quality is good, the system transmits more bits at lower power; when channel quality degrades, it transmits fewer bits at higher power, maintaining the product relationship that governs effective signal-to-noise ratio
Data Source
AI summary
Significant improvement in Raptor codes and punctured LDPC codes are obtainable by use of the invention. In both a transmission scheme for Raptor-encoded or LDPC-encoded information, a dynamic adjustment approach is employed. A fraction of a codeword or information frame is transmitted. A feedback signal is sent from the receiver to the transmitter indicating either 1) successful decoding, or 2) failure to decode and/or a feedback signal indicative of a statistical measure of transmission channel quality. If decoding fails, a further portion of the codeword or frame is sent. The intensity and/or size of the fraction is adjusted based on the feedback signal. In one embodiment, a specific range for probabilities employed in the encoding process for Raptor codes provides the ability to increase transmission throughput. Further it has been found that the advantageous Raptor codes are useful in noise conditions where even the improved punctured LDPC codes of the invention begin to degrade.