Access Point Wireless Medium Clearing via CTS-to-Self
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Solution Overview
Problem
Wireless networking environments face issues with 'hidden nodes' causing collisions and inefficient medium usage due to non-responsive nodes, leading to low throughput and corrupt data reception.
Innovation Solution
Access points (APs) are instructed to transmit Clear to Send (CTS)-to-self or Contention Free (CF)-end frames to clear Network Allocation Vectors (NAV) set by failed Request to Send (RTS) frames, allowing for selective medium clearing based on Quality of Service (QoS) of queued frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RTS frames are repeatedly transmitted to reserve the medium for non-responsive nodes, then collision avoidance is improved, but medium efficiency deteriorates due to airtime wastage
Solution Approach 1:
The AP transmits CTS-to-self frames proactively to clear the medium before attempting to transmit data frames. This preliminary action removes the reserved status set by failed RTS frames, preventing future collisions while avoiding the wastage of repeatedly transmitting RTS frames to non-responsive nodes. The medium is cleared in advance, allowing other nodes to access it when ready.
Solution Approach 2:
The patent extracts the harmful reserved status from the medium by transmitting CTS-to-self frames that clear the NAV vectors of other nodes. This separates the collision avoidance function from the data transmission function, allowing the medium to be freed from the束缚 of failed RTS frame reservations without compromising reliability.
2Reliability
If RTS frames are used to reserve medium for hidden nodes, then hidden terminal problem is mitigated, but throughput deteriorates due to continuous retry attempts
Solution Approach 1:
The AP performs preliminary medium clearing by transmitting CTS-to-self frames before attempting data transmission. This preliminary action ensures that even if RTS frames have reserved the medium for hidden nodes, the medium will be cleared before data transmission, preventing continuous retry attempts and improving throughput while maintaining hidden terminal mitigation.
Solution Approach 2:
The CTS-to-self frame acts as an intermediary mechanism that resolves the conflict between RTS frame reservations and medium availability. It mediates between the need to maintain reservations for hidden terminal protection and the need to free the medium for throughput improvement, by clearing the medium in a controlled manner without directly conflicting with RTS frame functionality.
3Reliability
If AP continuously transmits RTS frames to non-responsive nodes, then medium reservation is maintained, but time efficiency deteriorates due to extended reservation duration
Solution Approach 1:
The AP transmits CTS-to-self frames as a preliminary action to clear the medium before attempting data transmission. This prevents the need for continuous RTS frame transmissions to maintain reservation, as the medium is proactively cleared of reserved status. The time loss is reduced because the clearing action is performed once rather than requiring continuous retry attempts.
Solution Approach 2:
Instead of continuous RTS frame transmission, the patent employs periodic CTS-to-self frame transmission to clear the medium. This periodic action maintains medium reservation reliability by periodically ensuring the medium is clear, while significantly reducing the time loss associated with continuous retry attempts to non-responsive nodes.
Data Source
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AI summary
In some examples, a method can include transmitting, with an Access Point (AP), Request to Send (RTS) frames to a wireless client over a wireless medium; determining, with the AP, whether the medium is reserved by failed RTS frames for the client; and transmitting, with the AP, a frame to clear the medium when it is determined that the medium is reserved by failed RTS frames for the client.