Downlink HARQ Network Coding for Lower Feedback Overhead
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Solution Overview
Problem
In 5G NR, there is a need to reduce HARQ feedback overhead, retransmission overhead, and overall transmission delays due to the introduction of network coding (NC) in HARQ procedures.
Innovation Solution
A wireless transmit/receive unit (WTRU) determines HARQ acknowledgments/negative acknowledgments based on physical layer decoding of PDSCH transmissions, using network coding-related scheduling information to adjust NC coding configurations and generates code block group-based feedback, indicating the number of incorrectly received NC code blocks for retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If network coding is introduced to HARQ procedures, then transmission reliability is improved, but HARQ feedback overhead increases
Solution Approach 1:
The patent segments the transport block into multiple code block groups (CBGs), each containing multiple network coded packets. This segmentation allows selective retransmission of only the failed CBGs rather than the entire TB, reducing feedback overhead while maintaining reliability. The HARQ feedback is divided into multiple bits corresponding to each CBG, enabling granular control.
Solution Approach 2:
The patent implements partial retransmission by transmitting only the failed CBGs in subsequent retransmission rounds, rather than retransmitting the entire TB. This partial action approach reduces the amount of feedback information needed and minimizes overhead while ensuring reliable delivery of all original packets.
2Reliability
If network coding is introduced to HARQ procedures, then data recovery capability is improved, but retransmission overhead increases
Solution Approach 1:
By segmenting the TB into CBGs at the network coding layer, the patent enables selective retransmission of only the failed segments. This reduces retransmission overhead compared to retransmitting the entire TB, while the network coding within each CBG maintains data recovery capability through linear combinations of original packets.
Solution Approach 2:
The patent discards (drops) only the failed CBGs from the retransmission process, while recovering (retransmitting) only the necessary information to reconstruct the failed segments. This selective approach minimizes retransmission overhead while preserving the ability to recover all original data packets through network coding.
3Ease of operation
If traditional TB-level HARQ feedback is used, then feedback simplicity is maintained, but transmission delay increases
Solution Approach 1:
The patent segments the TB-level feedback into CBG-level feedback, where each CBG generates its own HARQ feedback bit. This segmentation enables faster retransmission by identifying and retransmitting only the failed CBGs, reducing overall transmission delay while maintaining relatively simple feedback mechanisms through bitwise operations on the CBG feedback bits.
Data Source
AI summary
Procedures, methods, architectures, apparatuses, systems, devices, and computer program products for downlink (DL) hybrid automatic repeat request (HARQ) reporting and network coding (NC) of DL transmissions. A set of service data units (SDUs) may be encoded by a NC process to obtain a plurality of NC protocol data units (PDUs). NC PDUs may be carried by physical downlink shared channel (PDSCH) transmissions to a wireless transmit/receive unit (WTRU). The WTRU may determine HARQ feedback information (e.g., ACK/NACK) for a PDSCH transmission based on physical layer decoding of the PDSCH transmission and NC-related information. For example, code block group (CBG)-based HARQ feedback may be generated based on the NC-related information and a number of NC PDUs or code blocks (CBs) that are incorrectly received. For example, a WTRU may generate HARQ feedback information to indicate the number of NC PDUs or CBs that need to be retransmitted for the PDSCH transmission.