LDPC HARQ Incremental Redundancy for Faster Decoding Recovery
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Solution Overview
Problem
Current wireless communication technologies face challenges in achieving high-speed and reliable data transmission, particularly in wireless local area networks (WLANs), due to limitations in encoding and decoding processes, which affect the throughput and reliability of data transfer.
Innovation Solution
The implementation of a hybrid automatic repeat request (HARQ) process using incremental redundancy (IR) with low-density parity-check (LDPC) codes, where a first packet is encoded using LDPC encoding, and if not successfully decoded, a second packet is generated with additional parity bits to aid in successful decoding, enhancing the decoding performance through incremental redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single LDPC encoded packet is transmitted, then transmission speed is maintained, but decoding reliability deteriorates when initial transmission fails
Solution Approach 1:
The transmitter pre-generates multiple sets of parity bits corresponding to different code rates before transmission. When a packet transmission fails, the receiver requests additional parity bits from the pre-generated sets, enabling rapid retransmission without requiring full re-encoding, thus improving both reliability and throughput
Solution Approach 2:
The system dynamically changes the code rate parameter by transmitting packets with different proportions of information bits and parity bits. Initial transmissions use higher code rates for speed, while failed transmissions are retransmitted with lower code rates (more parity bits) to improve decoding reliability, resolving the contradiction between speed and reliability
2Reliability
If incremental redundancy is implemented with multiple LDPC encoding processes, then decoding performance is improved, but system complexity increases
Solution Approach 1:
The encoding process is segmented into multiple independent LDPC encoding operations, each generating a packet with a specific code rate. The transmitter maintains separate encoding contexts for different code rates, allowing modular implementation where each encoding process is independent but coordinated through the HARQ protocol, managing complexity through structured segmentation
Solution Approach 2:
The LDPC encoder is designed with multi-functionality to perform multiple encoding operations with different code rates using the same information bits. A single encoding module handles both initial high-rate transmission and subsequent low-rate retransmissions by adjusting the ratio of information bits to parity bits, reducing overall system complexity compared to having separate encoders for each code rate
3Reliability
If additional parity bits are generated for retransmission, then decoding success rate is improved, but transmission overhead increases
Solution Approach 1:
Instead of transmitting complete redundant packets for retransmission, the system transmits only the additional parity bits needed to achieve successful decoding. The receiver combines these partial transmissions with previously received bits to form complete codewords, reducing total transmission volume while maintaining high decoding success rates through incremental redundancy
Data Source
AI summary
This disclosure provides systems, methods and apparatus, including computer programs encoded on computer storage media, for low density parity check (LDPC)-based incremental redundancy (IR) hybrid automatic repeat request (HARQ) transmission processing. In one aspect, an apparatus for wireless communications is configured to generate a first packet using a LDPC encoding process. The apparatus is further configured to generate coded bits using a second LDPC encoding process if the first packet is not successfully decoded by a wireless device, generate a second packet including at least some of the coded bits generated using the second LDPC encoding process, and output the second packet for transmission.