WLAN HARQ Link Adaptation for MPDU Retransmission Decoding
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Solution Overview
Problem
Conventional WLAN systems lack an effective mechanism to utilize MPDU as an HARQ unit due to its MAC layer nature, hindering the implementation of low latency and high throughput required by delay-sensitive applications like VR, AR, robotics, and unmanned vehicles.
Innovation Solution
Implementing a hybrid automatic repeat request (HARQ) procedure that includes processing HARQ units across both MAC and PHY layers, utilizing short and long training fields, signal fields, and data fields to facilitate decoding and retransmission management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ARQ procedure is used at MAC layer, then implementation simplicity is maintained, but low latency and high throughput performance is insufficient
Solution Approach 1:
The patent merges MAC layer ARQ procedure with PHY layer HARQ procedure to form a hybrid protocol. The MAC layer transmits MPDUs containing HARQ units, while the PHY layer performs combining operations on these HARQ units. This integration allows the system to achieve both low latency and high throughput by leveraging the advantages of both layer-based approaches without the complexity of fully implementing PHY-layer HARQ from scratch.
Solution Approach 2:
The patent segments the data transmission into HARQ units within MPDUs, allowing selective retransmission at the PHY layer while maintaining MAC layer control. This segmentation enables fine-grained retransmission management, improving throughput by retransmitting only failed HARQ units rather than entire MPDUs, while the MAC layer remains relatively simple in its handling of these segmented units.
2Ease of operation
If MPDU is used as HARQ unit, then MAC layer processing is simplified, but PHY layer combining operation becomes problematic
Solution Approach 1:
The patent introduces HARQ units as an intermediary structure that bridges the MAC layer MPDU and PHY layer combining operations. These HARQ units serve as the common interface between layers, allowing the MAC layer to treat them as simple data units while the PHY layer can perform combining operations on them. The HARQ unit format includes necessary fields for both MAC processing and PHY combining, resolving the incompatibility between layer requirements.
3Reliability
If retransmission is performed without HARQ-related information, then protocol simplicity is maintained, but decoding reliability decreases
Solution Approach 1:
The patent implements feedback mechanisms through HARQ-related information fields in the signal field of data units. The transmitter includes information about the status of HARQ units, allowing the receiver to determine which units require retransmission. This feedback enables reliable decoding by ensuring that retransmitted units are properly identified and combined with previous transmissions, while the feedback information itself is efficiently integrated into the protocol structure.
Data Source
AI summary
An electronic device receives a first data unit including a first hybrid automatic repeat request (HARQ) unit and transmits a second data unit including first HARQ-related information indicating that the first HARQ unit fails to be decoded. The electronic device receives a third data unit including a preamble. The preamble includes a first STF, a first LTF, a signal field, a second STF, and a second LTF, and the third data unit includes second HARQ-related information indicating whether the third data unit includes retransmitted data. The electronic device obtains a second HARQ unit based on determination that the second HARQ-related information indicates that the third data unit includes retransmitted data and decodes the second HARQ unit with the first HARQ unit.