Self-Decodable LDPC Redundancy Versions for Missed Original Transmissions
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Solution Overview
Problem
Wireless communication systems using LDPC codes face reduced throughput due to non-self-decodable retransmissions, where receiving devices fail to decode information bits without the original transmission, especially under high interference or missed transmission grants.
Innovation Solution
The implementation of self-decodable redundancy versions for LDPC codes, where bits are re-ordered and stored in a circular buffer to ensure that retransmissions include sufficient systematic bits, allowing independent decoding even without the original transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional redundancy versions are used for LDPC codes, then the system can achieve high throughput under ideal conditions, but the receiving device cannot decode retransmissions independently when the original transmission is lost
Solution Approach 1:
The encoded bit stream is segmented into multiple redundancy versions (RV0, RV1, RV2, RV3) with different starting positions and lengths. Each RV is designed to contain sufficient systematic bits for independent decoding, allowing the receiver to successfully decode any single transmission without requiring the original transmission.
Solution Approach 2:
The system pre-generates multiple redundancy versions during the encoding phase, each carefully constructed to be self-decodable. This preliminary preparation ensures that regardless of which transmission is received, the decoder has all necessary information to recover the original data without needing to request retransmission.
2Reliability
If retransmissions use mainly parity bits to improve decoding of original transmission, then decoding efficiency improves, but the retransmission becomes non-self-decodable when original transmission is missed
Solution Approach 1:
Different redundancy versions have different compositions of systematic and parity bits tailored to their specific decoding needs. For example, RV0 contains all systematic bits for initial decoding, while RV1-RV3 contain different combinations that ensure self-decodability. This local optimization of bit composition for each RV ensures both independent decodability and efficient throughput.
3Ease of manufacture
If the system uses standard LDPC encoding without self-decodable RVs, then the encoding process is simpler, but retransmission decoding fails under high interference or missed grants
Solution Approach 1:
The system dynamically selects which redundancy version to transmit based on channel conditions, packet type, and decoding requirements. The encoder can switch between different RV configurations to optimize for either simplicity or reliability depending on the operational context, making the encoding process adaptable rather than static.
Data Source
AI summary
Methods, systems, and devices for wireless communication are described. In some examples, a wireless device (e.g., a user equipment (UE) or a base station) may encode a codeword from a set of information bits using an LDPC code. The wireless device may then transmit multiple versions of the codeword to improve the chances of the codeword being received. In some aspects, the wireless device may use the techniques herein to generate self-decodable redundancy versions of the codeword to be transmitted to the receiving device. Accordingly, a receiving device may be able to identify information bits from one or more redundancy versions of the codeword even if the receiving device failed to receive an original transmission of the codeword.