NAV Control for Hidden Node Synchronization in WLAN
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Solution Overview
Problem
In wireless local area networks (WLANs) based on IEEE 802.11 technology, hidden nodes fail to enter the channel access competition state timely due to the 'hidden node problem,' where they do not receive the CF_End frame, leading to regional discrimination and delayed channel access.
Innovation Solution
A method where a TXOP responder updates its local NAV value to a preset first value when monitoring a MAC frame carrying a specific identity, allowing hidden nodes to enter the channel access competition state synchronously with nodes under the TXOP holder's coverage, by transmitting a MAC response frame with a first identity indicating the end of the TXOP.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the TXOP holder transmits the CF_End frame to end the TXOP early, then nodes under the TXOP holder's coverage can enter channel access competition timely, but hidden nodes cannot receive the CF_End frame and thus cannot enter channel access competition timely
Solution Approach 1:
The patent introduces a new frame type called CF-End-Relay frame that acts as an intermediary to propagate the TXOP termination information to hidden nodes. The CF-End-Relay frame is transmitted by intermediate nodes (such as the last transmitting node in the TXOP) to relay the end-of-TXOP signal to nodes that could not receive the original CF_End frame from the TXOP holder, thereby solving the hidden node problem.
Solution Approach 2:
The patent segments the TXOP termination notification function into two parts: the original CF_End frame transmitted by the TXOP holder for nodes within direct range, and the CF-End-Relay frame transmitted by intermediate nodes for hidden nodes. This segmentation allows different transmission paths to reach different node groups, ensuring all nodes receive the termination signal appropriately.
2Reliability
If the NAV value is updated based only on the CF_End frame from the TXOP holder, then nodes under coverage can clear NAV timely, but hidden nodes maintain outdated NAV values causing regional discrimination
Solution Approach 1:
The patent implements a feedback mechanism where intermediate nodes monitor the TXOP termination frames and relay the information further to hidden nodes. The CF-End-Relay frame carries the necessary NAV clearance information back to hidden nodes, creating a feedback loop that ensures all nodes in the network, regardless of their position, receive consistent NAV update information and can synchronize their channel access timing.
Data Source
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AI summary
The present invention discloses a method, a device and a system for performing NAV control on a node and a node. The method includes: updating a local NAV value to a preset first value when it is determined that a preset first field of a monitored MAC frame carries a first identity, wherein the first value is smaller than a current local NAV value and the MAC frame of which the preset first field carriers the first identity is transmitted by a TXOP responder after receiving a last MAC frame transmitted by a TXOP holder. The method, device, system and node may enable a hidden station to enter a channel access competition state timely, thereby solving a problem of regional discrimination of a station.