Cross-Packet Check Blocks for URLLC Reliability
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Solution Overview
Problem
Existing wireless communication technologies face inefficiencies in parity check and retransmission techniques, particularly in scenarios requiring extreme low latency and high reliability, such as ultra-reliable low-latency communications (URLLC).
Innovation Solution
The implementation of physical layer network coding using two-dimensional (2D) joint coding, which involves generating cross-packet check blocks from bits of multiple packets and transmitting these check blocks along with the packets to improve decoding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional HARQ retransmission is used where all code blocks are retransmitted when any CB is in error, then reliability is improved, but transmission efficiency deteriorates due to redundant retransmission of correctly decoded blocks
Solution Approach 1:
The transport block is divided into multiple code block groups (CBGs), where each CBG contains one or more code blocks. This segmentation allows the receiver to identify and report only the specific CBGs that contain erroneous code blocks, enabling selective retransmission of only the failed CBGs rather than retransmitting all CBs, thus improving transmission efficiency while maintaining reliability
Solution Approach 2:
Instead of retransmitting all code blocks when any error is detected, the system retransmits only the partial set of code blocks that are actually in error (i.e., only the erroneous CBGs). This partial action approach avoids the waste of retransmitting correctly decoded blocks, thereby improving transmission efficiency without compromising the reliability of the overall transport block
2Productivity
If code block groups (CBGs) are used with index feedback, then retransmission efficiency is improved, but feedback overhead increases when multiple CBGs need to be reported
Solution Approach 1:
Multiple individual code block groups are merged into a single transport block structure, allowing the feedback mechanism to report errors at the CBG level rather than individual CB level. This merging reduces the quantity of feedback information needed while maintaining the ability to selectively retransmit only erroneous portions, thus improving retransmission efficiency without excessive feedback overhead
3Ease of operation
If outer codes are used for erasure coding, then no knowledge of failed CBs is needed, but effectiveness decreases when the number of failed CBs is large
Solution Approach 1:
The transport block is segmented into multiple CBGs, each with its own error detection capability. This segmentation allows the system to identify which specific CBGs contain errors without needing complex outer code mechanisms, while still providing effective error correction when the number of failed CBs is large by enabling targeted retransmission of only the erroneous CBGs rather than relying solely on outer code recovery
Data Source
AI summary
Methods and systems for physical layer network coding based on two-dimensional (2D) joint coding are described. In some methods, first and second packets are obtained. A set of one or more cross-packet check blocks is generated, where each cross-packet check block is generated based on a set of cross-packet bits including at least one bit from each of the first and second packets. At least one cross-packet check block is transmitted to a first communication node.