WLAN Transmission Rate Control via Collision Detection
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Solution Overview
Problem
Existing link adaptation schemes in IEEE 802.11 WLANs fail to distinguish between collision-caused and channel error-caused transmission failures, leading to inefficient rate adjustments in high-contention environments, which results in decreased performance and increased time consumption during data transmission.
Innovation Solution
A method and apparatus that detect collision-caused transmission failures and implement an RTS/CTS exchange scheme to retransmit data, adjusting the transmission rate based on the number of failures to optimize data transmission in both high- and low-contention environments by differentiating between channel errors and collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If link adaptation schemes decrease transmission rate upon transmission failure, then transmission reliability improves, but transmission efficiency deteriorates in high-contention environments due to collision misidentification
Solution Approach 1:
The patent segments transmission failures into two distinct categories: collision-caused failures and channel error-caused failures. By implementing separate handling mechanisms for each type (RTS/CTS exchange for collisions, rate fallback for channel errors), the system avoids misidentification and maintains transmission efficiency while ensuring reliability for actual channel errors.
Solution Approach 2:
The patent introduces an intermediary collision detection mechanism that operates between the transmission layer and the rate adaptation layer. This intermediary detects collisions through specific indicators (ACK timeout, CTS timeout, RTS timeout) and prevents them from being mistakenly treated as channel errors, thereby maintaining transmission efficiency while preserving reliability for genuine channel errors.
2Reliability
If RTS/CTS exchange is implemented for all transmissions, then collision avoidance improves, but overhead increases and performance decreases in low-contention environments
Solution Approach 1:
The patent implements a dynamic RTS/CTS triggering mechanism that adapts to current channel conditions. The system monitors transmission failure patterns and selectively activates RTS/CTS exchange only when collision indicators are detected, rather than applying it universally. This dynamic approach reduces overhead in low-contention environments while maintaining collision avoidance capability when needed.
Solution Approach 2:
The patent changes the parameter of RTS/CTS usage from a static always-on mode to a conditional mode based on detected transmission failure patterns. By monitoring parameters such as ACK timeout, CTS timeout, and consecutive failure counts, the system adjusts whether to employ RTS/CTS exchange, thereby optimizing the balance between collision avoidance and overhead in different environmental conditions.
3Object-affected harmful factors
If transmission rate is decreased upon collision, then collision impact is reduced, but transmission performance deteriorates due to unnecessary rate reduction
Solution Approach 1:
The patent segments the handling of transmission failures by type, applying different responses to collision-caused failures versus channel error-caused failures. For collisions, the system employs RTS/CTS exchange to protect the transmission without necessarily reducing the data rate. For channel errors, rate fallback is applied. This segmentation prevents unnecessary rate reduction for collisions while still addressing their impact through appropriate protective mechanisms.
Solution Approach 2:
The patent implements a feedback mechanism that monitors transmission outcomes and distinguishes between collision indicators (ACK timeout, CTS timeout) and channel error indicators. This feedback loop enables the system to make informed decisions about whether to apply rate reduction or RTS/CTS protection, avoiding unnecessary rate reduction for collisions while maintaining performance for channel errors.
Data Source
AI summary
An apparatus and method for controlling transmission rate by determining whether a data transmission failure is caused by a channel error or a data collision in order to reduce a collision-caused rate decrease or a collision-caused rate increase delay in a WLAN. A collision-caused data transmission failure and if the number of data transmission failures reaches a predetermined threshold, data is retransmitted by means of an RTS/CTS exchange.