Wireless LAN Frame Retransmission Using MPDU Segmentation and Block ACK
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Solution Overview
Problem
Current wireless LAN systems face challenges in efficiently retransmitting frames, particularly in high-frequency bands like the 60 GHz band, where signal propagation is dominated by ray-like propagation, leading to issues with antenna beam alignment and throughput optimization.
Innovation Solution
A method for frame retransmission in a wireless LAN system using multiple directional antenna modules, where a MAC Service Data Unit (MSDU) is segmented into multiple MAC Protocol Data Units (MPDUs) with division and sequence information, and if an acknowledgement (ACK) is not received within a preset time, a Block ACK Request (BAR) frame is sent to determine which MPDUs to retransmit, based on a Block ACK (BA) frame received from the second wireless terminal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If frame retransmission is performed in wireless LAN system operating at 60 GHz band, then throughput can be improved, but signal propagation reliability deteriorates due to ray-like propagation characteristics
Solution Approach 1:
The patent segments a MAC Service Data Unit (MSDU) into multiple MAC Protocol Data Units (MPDUs) for transmission. Each MPDU is assigned a sequence number, allowing the receiver to identify and acknowledge successfully received segments. This segmentation enables selective retransmission of only failed segments rather than retransmitting the entire data unit, improving reliability in the challenging 60 GHz propagation environment while maintaining throughput efficiency.
2Speed
If multiple MPDUs are transmitted without segmentation, then transmission speed is improved, but retransmission efficiency deteriorates when packet loss occurs
Solution Approach 1:
The patent divides the MSDU into multiple MPDUs that can be transmitted in sequence without waiting for acknowledgments between segments, maintaining high transmission speed. When packet loss is detected through missing sequence numbers in Block ACK frames, only the specific lost MPDUs are retransmitted rather than all transmitted data, significantly improving retransmission efficiency.
Solution Approach 2:
The patent implements a feedback mechanism using Block ACK frames that contain acknowledgment information for multiple received MPDUs. The receiver sends Block ACK frames containing sequence numbers of successfully received MPDUs, enabling the transmitter to identify which segments were lost and retransmit only those specific segments, optimizing retransmission efficiency.
3Loss of energy
If Block ACK frames are used for multiple MPDU acknowledgment, then overhead is reduced, but complexity of frame processing increases
Solution Approach 1:
The patent combines multiple individual ACK frames into a single Block ACK frame that acknowledges multiple received MPDUs simultaneously. The Block ACK frame contains a compact bitmap or sequence number list indicating which MPDUs were successfully received, reducing the total number of frames transmitted and lowering overhead. While the frame structure is more complex, the overall system overhead is reduced due to fewer frame exchanges.
Data Source
AI summary
A method for frame retransmission performed by a first wireless terminal in a wireless LAN system comprises the steps of: dividing an MSDU received from an upper layer of a first wireless terminal into multiple MPDUs; transmitting the multiple divided MPDUs to a second wireless terminal, wherein each of the multiple divided MPDUs includes division information and transmission sequence information; if an ACK frame for notifying of successful reception of the multiple divided MPDUs is not received until a preset time elapses, transmitting, to the second wireless terminal, a BAR frame for determining at least one MPDU to be retransmitted by the first wireless terminal among the multiple divided MPDUs; receiving a BA frame from the second wireless terminal in response to the BAR frame, wherein the BA frame includes frame information indicating a last MPDU successfully received by the second wireless terminal among the multiple divided MPDUs; and performing a retransmission procedure on the basis of the frame information.