Packet Bit Remapping for Robust HARQ Control in Wi‑Fi
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Solution Overview
Problem
The IEEE 802.11 standard does not support Hybrid Automatic Repeat Request (HARQ), leading to difficulties in identifying and storing control information necessary for soft combining at the receiver, especially when address, sequence, or delimiter fields are corrupted during transmission.
Innovation Solution
Re-mapping the data packet to make control information more robust by using systematic LDPC codes and modifying modulation to assign higher robustness to HARQ control bits, allowing for reliable decoding and soft combining during re-transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control information is coded and modulated in the same manner as data in IEEE 802.11, then the transmission structure remains simple and compatible with existing standards, but the receiver cannot reliably identify which soft bits to store and combine when decoding fails
Solution Approach 1:
The patent segments the data packet into distinct portions: control information (including HARQ process ID, receiver address, sequence number) and data payload. The control information is separately encoded and modulated with higher robustness than the data portion, allowing the receiver to reliably identify and extract control fields even when data decoding fails. This segmentation enables reliable soft combining by ensuring control information integrity.
Solution Approach 2:
The patent applies different modulation and coding schemes to different parts of the packet. Specifically, control information bits are mapped to more robust modulation symbols (e.g., using lower-order QAM or more redundant coding) compared to the data portion. This local quality enhancement ensures that control fields remain reliably decodable under poorer channel conditions, enabling successful HARQ operations.
2Reliability
If address, sequence, or delimiter fields are corrupted during transmission, then the receiver cannot determine which soft bit information corresponds to any given sub-frame, but increasing redundancy to prevent corruption reduces transmission efficiency
Solution Approach 1:
The patent performs preliminary encoding and modulation of control information with enhanced robustness before transmission. By pre-protecting control fields (HARQ process ID, address, sequence number) against corruption through more robust coding schemes, the receiver can reliably identify sub-frame boundaries and associate soft bits with the correct data portions, enabling accurate soft combining without requiring excessive redundancy in the data portion itself.
Solution Approach 2:
The control information fields act as an intermediary that mediates between the transmitted signal and the receiver's decoding process. By ensuring the integrity of these intermediary control fields through robust encoding, the receiver can correctly interpret the data structure and perform accurate soft combining, maintaining throughput while improving reliability.
Data Source
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AI summary
A transceiver device comprises a controller arranged to identify a first set of control information within the data packet, and to re-map the data packet such that the first set of control information is mapped on bits known to be more robust. The transceiver device further comprises a transmitter arranged to transmit the re-mapped data packet. The first set of control information holds information which enables for identification to combine soft bits from repeated transmissions at a receiver of the packet. The bits known to be more robust have more distinct value distribution in signal space of a used modulation and coding scheme than other bits. The transceiver device is arranged to transmit a data packet. A corresponding method, computer program, access point and station are also disclosed.