LDPC-HARQ Retransmission for Variable-Rate 5G Links
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Solution Overview
Problem
Current 5G communication systems face challenges in overcoming noise, fading, and inter-symbol interference, which degrade link performance and limit the reliability of high-speed digital communication and broadcasting systems, particularly in next-generation mobile communication and digital broadcasting.
Innovation Solution
The implementation of low density parity check (LDPC) encoding and decoding methods that support variable-length codewords and rates, integrated with a hybrid automatic repeat request (HARQ) scheme, using a designed parity check matrix to generate and transmit bit sequences effectively in communication systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional error correction methods are used, then implementation is simpler, but reliability under noise and interference is insufficient
Solution Approach 1:
The patent segments the error correction process into distinct encoding and decoding phases with well-defined interfaces. The encoder generates systematic codewords with structured parity bits, while the decoder uses structured algorithms (belief propagation, min-sum) that process messages in discrete steps between variable nodes and check nodes on the Tanner graph, making the complex process manageable and implementable
Solution Approach 2:
The patent employs LDPC codes with variable code rates achieved by puncturing different numbers of parity bits from the same base code. By changing the code rate parameter (e.g., from 1/2 to 2/3 to 3/4), the system adapts to different channel conditions and reliability requirements without changing the fundamental code structure, maintaining implementation simplicity while achieving high reliability
2Adaptability or versatility
If fixed-length codewords are used, then encoding and decoding are simpler, but adaptability to different data rates is limited
Solution Approach 1:
The patent uses a universal base LDPC code structure that can serve multiple functions by applying different puncturing patterns. The same base code generates codewords for various code rates (1/2, 2/3, 3/4, etc.) and supports both systematic and non-systematic modes, eliminating the need for multiple specialized codes and simplifying the overall system while achieving high adaptability
Solution Approach 2:
The patent pre-defines multiple puncturing patterns and code rate configurations in the codebook. During operation, the receiver simply needs to identify which code rate and puncturing pattern was used (through signaling) and apply the corresponding predetermined decoding parameters, avoiding complex real-time code selection and reducing operational complexity
3Productivity
If high code rates are used, then transmission efficiency is higher, but error correction capability under noise deteriorates
Solution Approach 1:
The patent implements dynamic code rate adaptation where the system can switch between different code rates (1/2, 2/3, 3/4, etc.) based on channel conditions. When the channel is good, higher code rates provide better efficiency; when the channel is poor, lower code rates provide stronger error correction capability. This dynamic adjustment optimizes both productivity and reliability according to actual transmission conditions
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.