LDPC HARQ Retransmission with Flexible Lifting and Code Rates
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Solution Overview
Problem
Existing LDPC codes face challenges in supporting variable lengths and code rates, particularly in 5G communication systems, due to limitations in existing lifting methods that restrict length compatibility and code rate flexibility, making it difficult to apply them effectively in mobile communication systems.
Innovation Solution
The proposed solution involves designing a parity check matrix using a modified lifting process that allows exponent conversion without performance degradation, even when the values of Z are not in a multiple relationship, enabling support for various lengths and code rates through the use of a redundancy version index and rate matching in LDPC encoding and decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing lifting methods are used for LDPC codes, then the code structure is simple, but the length compatibility and code rate flexibility are restricted
Solution Approach 1:
The patent applies dynamics by making the lifting process adaptive rather than fixed. The modified lifting process dynamically adjusts the exponent values in the parity check matrix based on the desired code length and rate, allowing the same base matrix to generate multiple LDPC codes with different parameters. This resolves the contradiction by enabling flexibility without requiring completely different matrix designs for each application scenario.
Solution Approach 2:
The patent changes the exponent parameter in the parity check matrix construction to achieve different code lengths and rates. By modifying the exponent values (particularly allowing non-multiple relationships between Z values), the system can generate LDPC codes with varying parameters from a unified base structure. This parameter change approach enables length compatibility and code rate flexibility while maintaining structural simplicity.
2Adaptability or versatility
If variable lengths and code rates are supported, then the adaptability improves, but the complexity of encoding and decoding increases
Solution Approach 1:
The patent achieves universality by designing a single modified lifting process that can generate LDPC codes for multiple code lengths and rates. The unified parity check matrix construction method serves multiple functions - it can produce different code parameters by adjusting exponent values, eliminating the need for separate encoding/decoding implementations for each code variant. This reduces overall system complexity while maintaining broad adaptability.
Solution Approach 2:
The patent segments the parity check matrix into base matrices with specific exponent patterns that can be systematically varied. This segmentation allows the encoding and decoding processes to follow consistent algorithms while adapting to different code parameters through controlled modifications of the exponent values, rather than requiring completely different processing paths for each code variant.
3Adaptability or versatility
If exponent conversion is performed in lifting process, then the flexibility increases, but the performance may degrade
Solution Approach 1:
The patent carefully controls parameter changes in the exponent conversion process to maintain performance. By establishing specific relationships between exponent values and code parameters, and by constraining the conversion rules to preserve essential code properties, the system achieves flexibility without sacrificing reliability. The modified lifting process ensures that exponent conversions maintain the structural integrity needed for good coding performance.
Data Source
AI summary
The present disclosure relates to a pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4th-Generation (4G) communication system such as Long Term Evolution (LTE). The present disclosure discloses a method for effective retransmission when HARQ is applied to data encoded with a low density parity check (LDCP) code. A data transmission method of the transmitter may include: initially transmitting data encoded with an LDPC code to a receiver; receiving a negative acknowledgement (NACK) from the receiver; determining retransmission related information for data retransmission; and retransmitting, in response to the NACK, LDPC-encoded data based on the retransmission related information.