Guard Interval Detector for Wireless Collision Mitigation
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Solution Overview
Problem
IEEE 802.11ah devices face challenges in collision mitigation due to their different power-saving characteristics and bandwidth ratios compared to IEEE 802.11ac devices, leading to increased conflicts during channel assessment and network allocation.
Innovation Solution
Implementing a guard interval detector within the Clear Channel Assessment (CCA) logic to detect guard intervals on both primary and secondary channels, allowing devices to defer transmissions and avoid collisions by correlating signals with delayed versions to identify ongoing transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If IEEE 802.11ah devices use standard CCA rules for channel assessment, then coexistence with IEEE 802.11ac devices is enabled, but collision probability increases due to different power-saving characteristics and bandwidth ratios
Solution Approach 1:
The patent segments the channel assessment process into two distinct phases: initial CCA using standard rules for coexistence, and a subsequent refined CCA using guard interval detection for collision avoidance. This segmentation allows devices to first establish basic compatibility with diverse standards, then apply more sophisticated detection specifically tailored to their operating context, thereby resolving the contradiction between broad adaptability and collision reliability.
Solution Approach 2:
The patent implements preliminary guard interval detection before actual data transmission begins. By detecting the guard interval of an ongoing transmission in advance, devices can determine channel availability ahead of time and adjust their transmission timing accordingly. This preliminary action allows IEEE 802.11ah devices to wake from power-save mode and perform channel assessment without risking collisions with ongoing IEEE 802.11ac transmissions.
2Reliability
If devices perform frequent channel assessments to avoid collisions, then collision probability decreases, but power consumption increases due to extended active mode duration
Solution Approach 1:
The patent replaces continuous active monitoring with event-triggered guard interval detection. Instead of keeping the receiver continuously active to monitor for collisions, devices only activate the guard interval detector when specific conditions are met (e.g., upon waking from power-save mode). This substitution dramatically reduces power consumption while maintaining collision avoidance effectiveness, as the detection mechanism is triggered only when necessary rather than operating continuously.
Solution Approach 2:
The patent changes the operational parameters of channel assessment by introducing guard interval detection with specific correlation thresholds and timing parameters. Rather than using uniform assessment intervals, the system adjusts detection parameters dynamically based on whether a guard interval is detected, allowing devices to extend or shorten their active monitoring period accordingly. This parameter adaptation reduces unnecessary active mode duration and associated power consumption while maintaining reliable collision detection.
3Measurement precision
If guard interval detection is implemented on both primary and secondary channels, then channel availability determination accuracy improves, but device complexity increases
Solution Approach 1:
The patent implements a universal guard interval detection mechanism that operates across multiple channel bandwidths (1 MHz, 2 MHz, 4 MHz, 8 MHz, 16 MHz) without requiring separate detection logic for each bandwidth. The same correlation-based detection algorithm is applied uniformly across all channel types, with the detector automatically adapting to the specific bandwidth configuration. This universal approach improves measurement precision across all channels while minimizing the increase in device complexity, as a single multi-functional detector replaces what would otherwise require multiple specialized detection circuits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces the probability of collisions by accurately determining channel availability, especially for devices waking from power-save mode, thereby enhancing coexistence and reducing power consumption.
Implementation Method 1
correlating signals with delayed versions to identify ongoing transmissions
Data Source
Figure 1
Figure 1A~1C
Figure 1D
AI summary
Logic for collision mitigation between transmissions of wireless transmitters and receivers operating at different bandwidths. Logic of the receivers may be capable of receiving and detecting signals transmitted at narrower bandwidths. In several embodiments, the receivers comprise a clear channel assessment logic that implements a guard interval (or cyclic prefix) detector to detect transmissions at narrower bandwidths. For instance, a two MegaHertz(MHz) bandwidth receiver may implement a guard interval detector to detect 1MHz bandwidth signals and a 16MHz bandwidth receiver may implement logic to detect one or more 1MHz bandwidth signals and any other combination of, e.g., 1, 2, 4, 8 MHz bandwidth signals. In many embodiments, the guard interval detector may be implemented to detect guard intervals on a channel designated as a primary channel as well as on one or more non-primary channels.