WLAN Reset Frame Synchronizes NAV Timers for Fair Medium Access
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Solution Overview
Problem
In wireless local area networks (WLANs) where high throughput (HT) stations and legacy stations coexist, collisions frequently occur due to differences in data transmission capabilities, leading to unfair access to the medium, as legacy stations struggle to interpret HT format frames and thus delay their contention for the medium.
Innovation Solution
Generating a data frame with HT format that includes information indicating medium unavailability until an ACK frame is received, and transmitting a reset frame that resets network allocation vectors (NAVs) of all stations, ensuring both HT and legacy stations can interpret it, allowing them to contend fairly by resetting NAV timers equally.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If HT format frames are used for high throughput transmission, then data transmission rate is improved, but legacy stations cannot interpret the frames properly causing collision probability to increase
Solution Approach 1:
The patent introduces a translation mechanism that converts HT format frames into legacy-compatible format. The access point receives HT format frames from HT stations, translates them into legacy format frames that legacy stations can interpret, and transmits them to legacy stations. This intermediary translation process enables high throughput transmission while maintaining compatibility with legacy stations, thus preventing collisions.
Solution Approach 2:
The patent changes the format parameter of the frame from HT format to legacy format during translation. By modifying the frame structure, header format, and other parameters to be compatible with legacy station requirements, the system enables legacy stations to properly interpret the frames while maintaining the high throughput capabilities of HT stations.
2Reliability
If virtual carrier sensing is used for collision avoidance, then medium access control is improved, but when MPDU cannot be properly extracted due to errors, collision probability increases
Solution Approach 1:
The access point acts as an intermediary that ensures proper frame extraction and interpretation. It receives frames from HT stations, extracts the necessary information, translates it into legacy format, and transmits to legacy stations. This intermediary process prevents extraction errors that would otherwise occur when legacy stations directly receive HT format frames.
Solution Approach 2:
The patent implements error prevention mechanisms before transmission occurs. The access point performs frame translation and validation in advance, ensuring that legacy stations receive frames in a format they can properly interpret. This beforehand cushioning prevents extraction errors and maintains reliable collision avoidance.
3Adaptability or versatility
If HT stations and legacy stations coexist in the same network, then network compatibility is improved, but unfair medium access occurs due to different data transmission capabilities
Solution Approach 1:
The access point serves as a fair intermediary that manages medium access between HT and legacy stations. It translates frames bidirectionally, ensuring that both HT and legacy stations can access the medium fairly without disadvantage to either group, thus maintaining network compatibility and operational fairness.
Solution Approach 2:
The access point performs multiple functions: receiving HT format frames from HT stations, translating them to legacy format, transmitting to legacy stations, and vice versa. This multi-functionality enables universal compatibility between different station types while maintaining fair medium access through centralized control.
Data Source
AI summary
A method and apparatus for preventing a plurality of stations in a wireless local area network (WLAN) where a plurality of high throughput (HT) stations and a plurality of 802.11 legacy stations coexist from colliding are provided. The method includes generating a data frame having an HT format by inserting information indicating that a medium will be unavailable until the reception of an acknowledgement (ACK) frame is concluded into a physical layer (PHY) header having a format that can be interpreted by both the HT stations and the legacy stations; transmitting the data frame; and transmitting a reset frame which resets network allocation vectors (NAVs) of a plurality of stations which have heard the data frame, and has a format that can be interpreted by both the HT stations and the legacy stations. The apparatus includes a data frame generation unit; a reset frame generation unit; and a transmission unit.