LDPC Rate Matching Using Circular Buffer Systematic Bit Puncturing
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Solution Overview
Problem
Existing rate matching methods for LDPC codes, such as those used in 802.11n, are unclear and inefficient, particularly in achieving specific code sizes and rates without defining separate procedures for shortening, puncturing, and repetition.
Innovation Solution
The implementation of circular buffer-based rate matching, which involves puncturing systematic bits and attaching dummy bits to adjust code rates and lengths, allowing for flexible generation of coded bits for transmission while maintaining the weight distribution of the parity check matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate procedures for shortening, puncturing, and repetition are used to achieve different code sizes and rates, then flexibility in code configuration is improved, but device complexity and procedure management become worse
Solution Approach 1:
The patent combines shortening, puncturing, and repetition operations into a single circular buffer-based rate matching procedure. The encoder writes codeword bits into a circular buffer and reads them out sequentially, with the read position and number of bits determining the effective code rate and length. This unified approach eliminates the need for separate procedural paths while achieving the same functional outcomes.
Solution Approach 2:
The circular buffer structure serves multiple functions simultaneously: it implements shortening by skipping initial bits, puncturing by selecting specific bits for transmission, and repetition by wrapping around the buffer. A single mechanism handles all three rate matching operations that previously required separate procedures.
2Productivity
If circular buffer-based rate matching with puncturing systematic bits is implemented, then rate matching efficiency is improved, but decoding performance may worsen
Solution Approach 1:
The patent applies different treatment to different portions of the codeword by puncturing only systematic bits at specific positions while preserving parity bits and other systematic bits. This selective puncturing maintains local code structure quality where it matters most for decoding while achieving the desired rate matching.
Solution Approach 2:
The circular buffer allows dynamic selection of which bits to transmit based on the desired code rate and length. The read position and number of bits read can be adjusted dynamically without changing the underlying encoder structure, enabling flexible rate adaptation while maintaining decoding performance through intelligent bit selection.
Data Source
AI summary
A method of producing a set of coded bits from a set of information bits for transmission between a first node and a second node in a wireless communications system, the method comprises generating a codeword vector by encoding the set of information bits with a low-density parity-check code, wherein the codeword vector is composed of systematic bits and parity bits. The method comprises performing circular buffer-based rate matching on the generated codeword vector to produce the coded bits for transmission, wherein the circular buffer-based rate matching comprises puncturing a first plurality of systematic bits.