Lifted LDPC Base Graph Encoding for Flexible Code Rates
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently encoding and decoding data at high rates, particularly in multiple-access technologies like 5G NR, where errors during data transmission can lead to unusable data and require retransmission, and existing LDPC codes are complex to implement and describe efficiently for various blocklengths and code rates.
Innovation Solution
The method involves generating lifted low-density parity-check (LDPC) codes by selecting lifting size values and applying lifting values to interconnect edges in copies of a base parity check matrix, allowing for compact description and efficient encoding/decoding of data, enabling flexible implementation across different wireless communication technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional LDPC codes are used for error correction in wireless communication, then data transmission reliability is improved, but encoding and decoding complexity increases
Solution Approach 1:
The patent segments the LDPC code structure into a base graph and multiple lifted graphs. The base graph contains the fundamental parity-check matrix, while lifted graphs are generated by applying lifting operations with different lifting sizes. This segmentation allows the system to use a compact base graph representation that reduces encoding and decoding complexity while maintaining error correction capability through the lifted structures.
Solution Approach 2:
The patent changes key parameters of the LDPC code by varying the lifting size parameter Z. By adjusting Z, the system can generate different code rates and block lengths from the same base graph. This parameter change approach enables flexible adaptation to different communication requirements without redesigning the entire code structure, thereby reducing complexity while preserving reliability.
2Adaptability or versatility
If LDPC codes are designed for various blocklengths and code rates, then adaptability is improved, but description and implementation complexity increases
Solution Approach 1:
The patent creates a universal base graph that serves multiple functions by generating different lifted graphs through lifting operations. A single base graph can produce multiple LDPC codes with different blocklengths and code rates by varying the lifting size parameter. This multi-functionality eliminates the need to store and implement separate parity-check matrices for each code configuration, thereby reducing description and implementation complexity while maintaining high adaptability.
Solution Approach 2:
The patent performs preliminary action by pre-defining the base graph structure and lifting rules. Once the base graph is established, all subsequent code variations are generated systematically through lifting operations with different parameters. This preliminary setup simplifies the description and implementation of multiple code rates and blocklengths, as the complex structural decisions are made once in advance rather than repeatedly for each code configuration.
3Reliability
If error correction coding is applied to prevent data errors, then data reliability is improved, but transmission overhead increases
Solution Approach 1:
The patent uses parameter changes in the lifting size to optimize the balance between error correction capability and transmission overhead. By adjusting the lifting size parameter, the system can achieve different code rates that optimize the ratio of information bits to total transmitted bits. This allows flexible control over the amount of redundancy added for error correction, thereby managing transmission overhead while maintaining data reliability.
Data Source
AI summary
Certain aspects of the present disclosure generally relate to techniques for compactly describing lifted low-density parity-check (LDPC) codes. A method for wireless communications by a transmitting device is provided. The method generally includes selecting a first lifting size value Z and a first set of lifting values for generating a first lifted LDPC code; generating the first lifted LDPC code by applying the first set of lifting values to interconnect edges in Z copies of a base parity check matrix (PCM) having a first number of base variable nodes and a second number of base check nodes to obtain a first lifted PCM corresponding to the first lifted LDPC code; determining a second set of lifting values for generating second lifted PCM corresponding to a second lifted LDPC code for a second lifting size value based on the first lifted PCM and the first set of lifting values; encoding a set of information bits based on at least one of: the first lifted LDPC code or the second lifted LDPC code to produce a code word; and transmitting the code word.