LDPC Puncturing Patterns Matched to Modulation Schemes
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Solution Overview
Problem
Current LDPC code systems, such as those used in DVB-S2, are limited to only two codeword lengths, which restricts their extendibility and flexibility, particularly in communication systems requiring various data rates, and storing independent parity-check matrices for each length reduces memory efficiency.
Innovation Solution
A method and apparatus for generating LDPC codes with different codeword lengths using puncturing or shortening, considering high-order modulation, by optimizing the puncturing pattern based on the structural characteristics of the LDPC code, such as q-periodic puncturing, to support various codeword lengths without the need for additional stored information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If independent parity-check matrices are stored for each codeword length, then various codeword lengths can be supported, but memory efficiency deteriorates
Solution Approach 1:
The patent applies universality by designing a single parity-check matrix that can serve multiple codeword lengths through puncturing operations. The base LDPC code is configured to generate codewords of a reference length, and by selectively puncturing different numbers of parity bits, the system can adaptively support various shorter codeword lengths using the same underlying matrix structure, thereby eliminating the need to store separate matrices for each length.
Solution Approach 2:
The patent utilizes parameter changes by varying the puncturing pattern and the number of punctured parity bits to achieve different codeword lengths from a single base code. By changing the puncturing parameters (which parity bits to remove and how many to remove) rather than changing the fundamental code structure, the system can flexibly support multiple codeword lengths while maintaining memory efficiency.
2Device complexity
If puncturing is applied without considering modulation scheme, then implementation is simpler, but decoding performance deteriorates in high-order modulation
Solution Approach 1:
The patent applies local quality by differentiating the puncturing strategy based on the specific modulation scheme being used. Different puncturing patterns are designed for different modulation types (e.g., QPSK vs. 16QAM vs. 64QAM), optimizing the puncturing approach for each local condition. This ensures that the puncturing operation maintains decoding performance by accounting for the specific reliability characteristics and bit significance of each modulation scheme.
Solution Approach 2:
The patent implements dynamics by making the puncturing pattern adaptive to the modulation scheme. Rather than using a fixed puncturing pattern regardless of conditions, the system dynamically selects or configures the puncturing pattern based on the active modulation scheme, allowing the puncturing behavior to change according to the operational context and maintain optimal performance across different modulation types.
Data Source
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AI summary
A method for encoding a channel in a communication system using a Low-Density Parity-Check (LDPC) code is provided. The method includes determining a number of parity bits for puncturing; dividing the parity bits at predetermined intervals, and determining a number of puncturing parity bits, which are subjected to puncturing within the predetermined intervals; determining a modulation scheme; determining positions of puncturing parity bits corresponding to the determined number of the puncturing parity bits within the predetermined intervals according to the modulation scheme; repeatedly performing puncturing on puncturing parity bits corresponding to the determined positions at the predetermined intervals; and transmitting remaining bits except for the punctured bits according to the modulation scheme.