HARQ Parity Frame Generation for IEEE 802.11
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Solution Overview
Problem
Current implementations of Hybrid Automatic Repeat Request (HARQ) in IEEE 802.11 standards face challenges in combining Forward Error Correction (FEC) and Automatic Repeat Request (ARQ) techniques across different protocol layers, leading to inefficiencies in data transmission due to codeword mismatches and lack of support for codeword-based ARQ mechanisms in the Physical (PHY) layer.
Innovation Solution
The proposed solution involves using an FEC Frame-based (FECF) encoder to generate parity frames at the sender, which are transmitted in response to ARQ requests, allowing for HARQ functionalities to be implemented with minimal changes to the PHY and MAC layers, including a HARQ-hard scheme at the MAC layer and a HARQ-soft scheme at the PHY layer, with opportunistic transmission of redundancy frames to compensate for packet losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If HARQ is employed only in the MAC protocol using MPDUs or A-MP DUs, then the implementation is simple at the MAC layer, but codeword mismatches prevent combining retransmitted codewords at the receiver
Solution Approach 1:
The patent merges HARQ functionality across both MAC and PHY layers by enabling the PHY layer to perform codeword-based ARQ operations. This allows the receiver to combine retransmitted codewords effectively while maintaining MAC layer protocol simplicity, resolving the contradiction between ease of implementation and combining capability.
Solution Approach 2:
The patent segments the HARQ implementation into distinct MAC layer and PHY layer functions. The MAC layer handles protocol control and ACK management, while the PHY layer handles codeword-level error correction and combining. This segmentation allows each layer to operate optimally without interfering with the other's functionality.
2Reliability
If HARQ is employed only at the LDPC codeword level, then combining retransmissions is effective, but the PHY layer lacks capability to support codeword-based ARQ mechanism
Solution Approach 1:
The patent introduces an intermediary mechanism where the MAC layer provides control signals and coordination for the PHY layer's codeword-based ARQ operations. This intermediary role enables the PHY layer to perform complex combining operations while the MAC layer maintains simplicity through standardized protocol interactions.
3Ease of operation
If ARQ is used independently at MAC layer, then protocol implementation is straightforward, but bandwidth efficiency is relatively low due to discarding partially decoded data
Solution Approach 1:
The patent merges ARQ and FEC functionalities into a unified HARQ system that operates across MAC and PHY layers. This integration allows partially decoded data to be retained and combined with retransmissions, improving bandwidth efficiency while maintaining protocol simplicity through the MAC layer's continued use of standard ACK mechanisms.
4Reliability
If FEC is used to improve transmission reliability, then retransmission is reduced, but bandwidth efficiency decreases due to added redundancy
Solution Approach 1:
The patent implements a dynamic HARQ system that adapts between FEC and ARQ modes based on channel conditions. When channel conditions are good, the system uses lighter FEC with fewer parity bits, improving bandwidth efficiency. When conditions deteriorate, the system increases FEC redundancy and utilizes retransmissions, maintaining reliability while optimizing spectral efficiency.
Data Source
AI summary
Methods and apparatus for enabling data transmission using HARQ in IEEE 802.11 systems are described. A method is disclosed, performed by a transmitting device, comprising computing a plurality of redundancy frames based on a plurality of data frames, transmitting the plurality of data frames to a receiving device, and transmitting a set of the plurality of redundancy frames to the receiving device determined by the transmitting device in response to receiving acknowledgement. One embodiment includes a method determining failed data frames of the plurality of data frames, requesting a set of the plurality of redundancy frames, and recovering the failed data frame using a decoder employing hard decision inputs. Other embodiments include an apparatus in a receiver device implementing the method of decoding the failed data frames using a decoder employing soft decision inputs.