Predictive HARQ Subcodeword Decodability Estimation
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Solution Overview
Problem
Communication networks face delays due to erroneous data transmissions and associated retransmission requests, as existing retransmission mechanisms often require additional round-trip time to correct decoding failures, especially in noisy channels.
Innovation Solution
Implementing a predictive hybrid automatic repeat request (HARQ) process using low-density parity-check (LDPC) codes, where a subcodeword is transmitted first to allow early decodability estimation at the receiver, enabling early retransmission requests and reducing latency by sending additional redundancy during the next transmission interval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional retransmission mechanisms are used, then decoding failures can be corrected, but additional round-trip time is required causing delays
Solution Approach 1:
The patent applies preliminary action by transmitting a subcodeword before the complete codeword, allowing the receiver to perform early decodability estimation. This enables the receiver to determine whether additional redundancy will be needed before the entire codeword is transmitted, thereby reducing the round-trip time required for retransmission requests while maintaining decoding reliability.
2Loss of time
If early decodability estimation is performed using subcodeword, then retransmission latency is reduced, but the system complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the complete codeword into a subcodeword (transmitted first) and remaining codeword parts. The subcodeword is sufficient for early decodability estimation, allowing the system to make retransmission decisions without processing the entire codeword, thus reducing latency while controlling the complexity increase through structured segmentation.
3Reliability
If additional redundancy is transmitted during next transmission interval, then decoding reliability is improved, but data processing efficiency may be reduced
Solution Approach 1:
The patent applies feedback by using the early decodability estimation result to control whether additional redundancy is transmitted. The receiver's estimation feedback enables the transmitter to send redundancy only when necessary, improving decoding reliability while maintaining data processing efficiency by avoiding unnecessary retransmissions that would reduce overall throughput.
Data Source
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Figure 3(a)
AI summary
A receiver is described which receives encoded data over a channel (102) from a transmitter. The data is parity-check encoded to obtain a codeword. The codeword is defined by a plurality of variable nodes associated with a plurality of the check nodes of a bipartite graph representing the code. The codeword is received over the channel (102) such that certain variable nodes, which are associated with a subset of the check nodes of the bipartite graph, are received prior to other variable nodes, and the certain variable nodes define a subcodeword (116a) known by the receiver. The receiver estimates a decodability of the transmitted codeword using the subcodeword (116a) prior to receiving all variable nodes of the codeword. Responsive to an estimation indicating that the codeword cannot be decoded, the receiver requests from the transmitter additional redundancy, and, responsive to an estimation indicating that the codeword can be decoded, the receiver signals the transmitter to stop transmitting additional redundancy. To estimate the decodability of the transmitted codeword, the receiver takes into account in addition one or more of the channel quality, the channel estimation, and CRC symbols.