HARQ Container Encapsulation for Wi-Fi LDPC Alignment
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Solution Overview
Problem
The current IEEE 802.11 Wi-Fi protocol does not seamlessly support Hybrid Automatic Repeat Request (HARQ) due to issues with scrambling, LDPC encoding, and payload alignment, which hinders efficient retransmission and combination of soft bits, limiting throughput and performance at lower Signal-to-Noise Ratios (SNR).
Innovation Solution
Decoupling data unit size from codeword size boundaries and scrambling seed management, by encapsulating data units in container units aligned with codeword sizes and separate transmission of scrambling seeds, allows for efficient HARQ implementation without modifying existing MPDU/A-MPDU formats or acknowledgement procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ is introduced into Wi-Fi to improve throughput and PER performance, then reliability and productivity are improved, but device complexity and difficulty of implementation increase due to conflicts with existing scrambling, LDPC encoding, and payload alignment mechanisms
Solution Approach 1:
The patent segments the data transmission structure by introducing container units that wrap individual MPDUs or A-MPDUs. Each container unit is independently encoded into codeword sets, allowing selective retransmission of only failed containers. This segmentation enables HARQ operation at the container level while maintaining compatibility with existing Wi-Fi protocols, resolving the conflict between introducing HARQ and maintaining protocol simplicity.
Solution Approach 2:
The container unit serves as an intermediary structure between the existing MPDU/A-MPDU format and the new HARQ mechanism. By encapsulating data units in containers with explicit alignment to codeword boundaries, the patent creates a buffer layer that reconciles the mismatch between variable-length MPDUs and fixed-size LDPC codewords, enabling HARQ without fundamentally altering existing protocols.
2Productivity
If data units are retransmitted with different scrambling seeds or LDPC encoding positions, then partial retransmission efficiency is improved, but soft bit combination fails because LLRs are misaligned
Solution Approach 1:
The patent applies preliminary action by pre-aligning each container unit to codeword boundaries before encoding. This ensures that when a container is retransmitted, its LLRs will be positioned identically to the original transmission, enabling reliable soft combining. The alignment is established in advance through the container structure design, which accounts for LDPC codeword length requirements before the actual encoding and retransmission processes.
3Reliability
If the scrambling function operates on the entire A-MPDU payload with 128-bit periodicity, then scrambling coverage is maximized, but alignment with 32-bit MPDU boundaries and LDPC codeword blocks is lost
Solution Approach 1:
The patent segments the scrambled payload into container units, each of which is then encoded into separate LDPC codeword sets. This segmentation allows the scrambling function to operate on the entire payload for maximum coverage while ensuring that each resulting container aligns with codeword boundaries. The container structure acts as a delimiter that preserves alignment information despite the periodic scrambling operation.
Data Source
AI summary
The present disclosure relates to Hybrid Automatic Repeat Request (HARQ) in wireless communication technologies, particularly HARQ for IEEE 802.11, i.e. HARQ for Wi-Fi. One example transmitting device is configured to encapsulate a data unit in a container unit, and encode the container unit into a codeword set of one or more codewords. One example receiving device is configured to receive, from a transmitting device, at least one codeword set of one or more codewords, decode the codewords of the codeword set to obtain a container unit, and decapsulate the container unit to obtain a data unit. A bit-size of the container unit is equal to a bit-size of the codeword set in the transmitting device and the receiving device.