Special Dual CTS Mode for Legacy-Compatible Collision Avoidance
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Solution Overview
Problem
Legacy STAs in wireless networks cannot decode new or proprietary RTS/CTS frames, leading to hidden node problems and collisions due to the inability to reserve time for data transmission, despite the introduction of dual CTS mode.
Innovation Solution
Implement a special dual CTS mode where STAs determine the type of CTS received and adjust their transmission sequence accordingly, either performing a dual CTS sequence or a normal CTS sequence based on the type of CTS, allowing for effective NAV updates and collision avoidance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If new or proprietary RTS/CTS frames are introduced to improve collision avoidance, then collision avoidance capability is improved for modern STAs, but legacy STAs cannot decode these frames leading to hidden node problems and collisions
Solution Approach 1:
The CTS frame is segmented into two types: a first type (new/proprietary format with NAV updates) and a second type (legacy format). The receiving STA transmits the first type CTS frame in response to an RTS frame, and then transmits the second type CTS frame after a predefined duration. This segmentation allows modern STAs to decode the NAV information while legacy STAs can still function using the second type frame.
Solution Approach 2:
The second type CTS frame acts as an intermediary that bridges the gap between new and legacy STAs. It provides the necessary NAV updates for legacy STAs to reserve time and avoid collisions, while the first type CTS frame provides enhanced functionality for modern STAs. The combination of both frame types resolves the compatibility issue.
2Reliability
If dual CTS mode is implemented to mitigate hidden node problem, then collision avoidance is improved, but legacy STAs still cannot decode NAV information leading to potential collisions
Solution Approach 1:
The CTS transmission is divided into two sequential phases: first transmitting a first type CTS frame containing NAV information in a new format, then transmitting a second type CTS frame in a legacy format. This ensures that both modern STAs (which can decode the first type) and legacy STAs (which can decode the second type) receive the necessary NAV information to avoid collisions.
Solution Approach 2:
The CTS frame format parameter is dynamically changed between two types. The first type CTS frame uses a new format with specific NAV information structure, while the second type uses a legacy format compatible with older STAs. This parameter change ensures broad compatibility while providing enhanced functionality.
Data Source
AI summary
Various techniques pertaining to a special dual clear-to-send (CTS) mode for improvement in collision avoidance in wireless communications are described. A first station (STA) transmits a request-to-send (RTS) and, in response, receives a first CTS from a second STA. The first STA waits to receive a second CTS from the second STA before transmitting data to the second STA responsive to the first CTS being of a first type and the second CTS being of a second type different from the first type. The first STA then transmits the data to the second STA upon passage of a waiting period.