RTS/CTS Bandwidth Signaling for Legacy-Compatible NAV Control

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Solution Overview

Problem

Existing methods for determining bandwidth in RTS/CTS frames are complex and prone to errors, and there is a need for backward compatibility with legacy protocols while ensuring all parties respect the Duration field.

Innovation Solution

The solution involves encoding bandwidth parameter sets within the scrambler seed or pad bits of RTS/CTS frames, using a predetermined format to indicate bandwidth and static/dynamic capabilities, and employing Viterbi algorithms for decoding, allowing receivers to determine bandwidth without additional channels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If bandwidth determination algorithms are implemented in DSP for RTS frames, then measurement precision is improved, but device complexity increases and reliability decreases due to errors

Engineering Contradiction:
Improvebandwidth determination accuracyVSAvoidalgorithm complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the bandwidth indication from complex DSP algorithms and encodes it directly into the RTS/CTS frame structures. The bandwidth parameter is taken out from the need for complex signal processing and represented as explicit field values in the frame, eliminating the need for complicated determination algorithms while maintaining accurate bandwidth information transmission.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent creates a simplified copy of the bandwidth information by encoding it directly into the frame structure rather than requiring complex DSP analysis. The bandwidth parameter is copied into standardized fields (such as bandwidth indication fields in 802.11ac/nax formats) that can be directly read and processed without complex algorithms, reducing both complexity and error potential.

Inventive Principle:
Principle #26Copying

2Adaptability or versatility

If RTS/CTS frames are made backwards compatible with legacy protocols, then adaptability is improved, but device complexity increases to handle multiple protocol versions

Engineering Contradiction:
Improvelegacy protocol compatibilityVSAvoidprotocol handling complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements a universal frame structure that serves multiple protocol versions simultaneously. The RTS/CTS frames are designed with field formats that are interpreted differently by legacy and modern devices, allowing a single frame structure to function across 802.11a, 802.11n, 802.11ac, and 802.11ax protocols without requiring separate frame formats for each version.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent applies local quality by making specific fields within the frame protocol-version-dependent while keeping the overall structure universal. Certain fields (such as bandwidth indication fields) are present and interpreted by modern devices, while legacy devices simply ignore them or interpret them according to their protocol version, allowing each device type to process only the relevant portions without increasing overall complexity.

Inventive Principle:
Principle #3Local quality

3Measurement precision

If additional channels are used for bandwidth indication, then measurement precision is improved, but loss of time increases due to additional channel reception

Engineering Contradiction:
Improvebandwidth indication accuracyVSAvoidchannel reception time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent merges the bandwidth indication information with the existing RTS/CTS frame structures rather than using separate dedicated channels. The bandwidth parameters are combined into the same communication channel and time slots as the primary data transmission, encoded in fields that coexist with other frame elements, eliminating the need for additional channel receptions while maintaining accurate bandwidth information transmission.

Inventive Principle:
Principle #5Merging (Combining)

Data Source

PatentEP2636187B1Bandwidth indication in RTS/CTS frames
Publication Date: 2026.04.01 CISCO TECHNOLOGY INC
  • EP2636187B1 patent drawingFigure 1~3
  • EP2636187B1 patent drawingFigure 2~4
  • EP2636187B1 patent drawingFigure 5~8

AI summary

Disclosed in an example embodiment is an apparatus comprising a transmitter and processing logic coupled with the transmitter. The processing logic is configured to send data via the transmitter. The processing logic generates a request to send frame. The processing logic encodes data representative of a bandwidth parameter set in the request to send frame. The processing logic transmits the request to send frame via the transmitter.