Incremental LDPC Coding for HARQ Under Interference
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Solution Overview
Problem
Wireless communication systems face challenges in accurately decoding LDPC encoded data due to errors caused by high interference and low transmission power, where existing coding schemes fail to provide unambiguous error correction, especially in HARQ transmissions.
Innovation Solution
The method involves incrementing the number of nodes in LDPC codes by adding explicit parity bits and core degree 2 accumulate nodes, allowing for unambiguous error correction by requesting and transmitting additional nodes as part of the HARQ transmission, thereby enhancing decoding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of nodes in LDPC code is increased to improve error correction capability, then decoding reliability is improved, but transmission overhead and complexity increase
Solution Approach 1:
The LDPC code is segmented into information bits and parity bits, with the parity portion used for error detection and correction. This segmentation allows the system to maintain reliable decoding through parity verification while keeping the information portion compact and efficient for transmission.
Solution Approach 2:
The patent employs incremental redundancy by dynamically adjusting the code rate and parity bit allocation based on channel conditions. When error rates are high, additional parity bits are transmitted to improve decoding reliability; when conditions are good, fewer parity bits are needed, reducing overhead and complexity.
2Reliability
If additional parity bits are added to enable unambiguous error correction, then error correction capability is improved, but transmission time and bandwidth consumption increase
Solution Approach 1:
The system dynamically adjusts the number of parity bits transmitted based on channel conditions and decoding success. This dynamic adaptation allows the system to achieve unambiguous error correction only when necessary, maintaining high transmission efficiency under good conditions while ensuring reliability when channel quality degrades.
Solution Approach 2:
The code rate and parity bit allocation are adjusted as parameters based on channel quality metrics. When the channel is clean, the system uses lower redundancy (higher code rate) to maximize throughput; when interference increases, additional parity bits are added (lower code rate) to ensure successful decoding, optimizing the trade-off between error correction capability and transmission efficiency.
3Reliability
If LDPC coding is used to correct errors from low transmission power and high interference, then transmission reliability is improved, but processing complexity at receiver increases
Solution Approach 1:
The received signal is segmented into information bits and parity bits, with separate processing paths for decoding and verification. This segmentation allows the receiver to efficiently process the signal by first attempting to decode the information portion and then using the parity portion for verification, reducing overall processing complexity compared to treating all bits uniformly.
Solution Approach 2:
The LDPC code structure enables the received signal to self-verify its integrity through built-in parity checks. The parity bits contain redundancy information that allows the receiver to automatically detect and correct errors without requiring complex external verification mechanisms, reducing receiver processing complexity while maintaining high transmission reliability.
Data Source
AI summary
Systems and methodologies are described that facilitate transmitting low-density parity-check encoded communications in a wireless communications network and incrementing such codes in response to requests from receiving devices. The LDPC codes can have associated constraints allowing the codes to be error corrected upon receipt. The requests for incremented codes can be in cases of low transmission power or high interference, for example, where the original code can be too error-ridden to properly decode. In this case, additional nodes can be added to current and/or subsequent communications to facilitate adding a more complex constraint to the LDPC code. In this regard, the large codes can require less validly transmitted nodes to predict error-ridden values as the additional constraint renders less ambiguity in possible node value choices.