Access Point Broadcast Frame Transmission Using Short IFS
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Solution Overview
Problem
In wireless local area networks (WLANs) using the IEEE 802.11 standard, broadcast/multicast frames often experience collisions due to the lack of effective collision avoidance mechanisms, leading to unreliable data transmission and network instability.
Innovation Solution
Implementing a method that uses shorter Interframe Space (IFS) intervals, such as Short IFS (SIFS) or Point Coordination Function IFS (PIFS), to prioritize access for broadcast/multicast frames, allowing the access point to transmit these frames immediately after an ACK, thereby reducing collisions and ensuring reliable transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DCF backoff algorithm is used for broadcast/multicast frames, then collision avoidance is attempted, but transmission reliability remains poor due to frequent collisions
Solution Approach 1:
The access point transmits broadcast/multicast frames immediately after receiving an ACK without performing a backoff procedure. This preliminary action of skipping the backoff algorithm for AP-initiated broadcast/multicast transmissions eliminates the waiting period that would otherwise expose the transmission to collisions, thereby improving transmission reliability while maintaining network productivity
Solution Approach 2:
The invention changes the IFS parameter from DIFS to SIFS for broadcast/multicast frame transmissions initiated by the access point. By using SIFS (Short Interframe Space) instead of DIFS (DCF Interframe Space), the AP可以获得更短的等待时间，从而减少碰撞机会，提高传输可靠性，同时保持网络生产力
2Stability of the object's composition
If standard DCF procedure is followed for broadcast/multicast frames, then medium access control is maintained, but transmission stability deteriorates due to collisions
Solution Approach 1:
The access point performs a preliminary check by waiting for an ACK from a station before transmitting broadcast/multicast frames. This preliminary action ensures the medium is ready and reduces the likelihood of collisions, thereby improving both network stability and transmission stability without requiring complex additional mechanisms
Solution Approach 2:
The ACK frame serves as an intermediary signal that mediates between the station's reception confirmation and the access point's subsequent broadcast/multicast transmission. By using this intermediary acknowledgment mechanism, the system achieves better coordination and reduces collisions, enhancing overall network and transmission stability
3Productivity
If backoff algorithm is applied to all frame types, then collision avoidance is attempted, but access efficiency for broadcast/multicast frames decreases
Solution Approach 1:
The invention applies different backoff rules to different frame types and different roles. Specifically, stations continue to use the standard DCF backoff algorithm for their transmissions, while the access point uses a simplified procedure (waiting for ACK then immediate transmission) for broadcast/multicast frames. This local differentiation improves access efficiency and reduces transmission delay for broadcast/multicast traffic without compromising the collision avoidance mechanism for other traffic types
Solution Approach 2:
The access point performs a preliminary waiting period for an ACK before transmitting broadcast/multicast frames, but then immediately transmits without further backoff. This preliminary action provides just enough time for medium assessment while eliminating unnecessary delays, thereby improving access efficiency and reducing transmission delay compared to applying full backoff procedures
Data Source
AI summary
Provided are a method and apparatus which can reduce the possibility of collision with other frames when transmitting a broadcast/multicast frame in a wireless local area network (LAN) following a Distributed Coordination Function (DCF) rule, thereby ensuring reliable transmission. The wireless communication method for sending or receiving a predetermined frame through contention between an access point and one or more stations according to DCF is characterized in that the access point uses the shortest of interframe space (IFS) intervals for access to a wireless medium. Therefore, when wireless LAN STAs operate in a DCF mode, the possibility of collision during broadcast or multicast frame transmission can be reduced while adopting conventional CSMA/CA mechanism, thereby improving reliability in successful frame transmission.