Access Point Block Acknowledgement Frame Generation for SIFS Compliance
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Solution Overview
Problem
In wireless local area networks (WLANs), the increasing complexity of data transmission algorithms and the introduction of distributed architectures lead to delays in replying with acknowledgement frames within the short interframe space (SIFS), making it difficult for receive end devices to respond promptly with acknowledgement frames.
Innovation Solution
The method involves an access point (AP) in a WLAN calculating and generating a block acknowledgement frame with a fixed length block acknowledgement bitmap field, allowing it to generate the legacy signal field of the preamble before receiving the aggregated MPDUs, thereby reducing processing delays and enabling timely acknowledgement frame transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the receive end device parses the MAC frame and generates the ACK frame using traditional methods, then the acknowledgement can be sent after receiving the data, but the processing time exceeds the short interframe space (SIFS) limit
Solution Approach 1:
The access point pre-calculates the length of the block acknowledgement frame based on the maximum quantity of bytes determined during session association phase, and pre-generates the legacy signal field with this predetermined length. This preliminary action allows the AP to prepare the acknowledgement frame structure before receiving the actual A-MPDU, eliminating the need to wait for complete data reception before initiating the acknowledgement transmission.
Solution Approach 2:
The patent changes the parameter of block acknowledgement bitmap field length from variable (based on actual received data) to fixed (maximum predetermined length). This parameter change allows the AP to determine the acknowledgement frame length in advance during session association, enabling timely generation of the legacy signal field and ensuring the total duration remains within the SIFS limit.
2Reliability
If the AP uses increasing complexity algorithms and distributed architecture to improve WLAN performance, then transmission reliability improves, but the processing duration for parsing MAC frames increases
Solution Approach 1:
The access point performs preliminary determination of the maximum quantity of bytes for the block acknowledgement bitmap field during the session association phase. This pre-determined value is stored and used to calculate the legacy signal field length in advance, allowing the AP to prepare acknowledgement frames without waiting for complete MAC frame parsing or A-MPDU reception, thus reducing processing duration while maintaining reliability.
Solution Approach 2:
The patent introduces dynamic adaptation where the AP determines the block acknowledgement bitmap field length based on the maximum quantity of bytes corresponding to each STA during session association. This dynamic determination allows the system to adapt to different STA requirements while maintaining a fixed predetermined length for practical purposes, balancing reliability needs with processing time constraints.
3Loss of information
If the AP waits to receive the entire A-MPDU before generating the block acknowledgement frame, then complete acknowledgement can be provided, but the transmission time exceeds the SIFS limit
Solution Approach 1:
The access point pre-calculates the legacy signal field length based on the predetermined maximum quantity of bytes for the block acknowledgement bitmap field, and pre-generates the legacy signal field with this length. This preliminary action allows the AP to start transmitting the acknowledgement frame immediately after receiving the trigger frame, without waiting for the entire A-MPDU to be received, thus maintaining timeliness while providing complete acknowledgement.
Solution Approach 2:
The patent changes the approach from variable acknowledgement frame length (based on actual received A-MPDU size) to fixed predetermined length (maximum possible size). This parameter change enables the AP to generate the legacy signal field in advance with the correct length, ensuring the total duration from receiving trigger frame to sending acknowledgement frame remains within the SIFS limit while still providing complete acknowledgement for all A-MPDU blocks.
Data Source
AI summary
A method for replying with an acknowledgement frame includes: calculating, by an access point (AP), sending duration of a physical layer service data unit (PSDU) in a to-be-sent downlink physical layer protocol data unit (downlink PPDU) based on a format and a sending rate that are of the downlink PPDU and based on only that a length of each block acknowledgement bitmap field in a block acknowledgement frame in the downlink PPDU is a maximum quantity of bytes that is of each respective block acknowledgement bitmap field of the plurality of stations (STAs), to generate an legacy signal field of a second preamble; and generating, by the AP, the block acknowledgement frame, where each STA information subfield in a block acknowledgement information field of the block acknowledgement frame includes an association identifier traffic identifier field, a block acknowledgement starting sequence control field, and a block acknowledgement bitmap field.