Collision Detection in Shared RF Spectrum
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Solution Overview
Problem
In wireless communication systems, collisions between different radio access technologies (RATs) transmitting in a shared radio frequency spectrum band are not effectively detected, leading to unfair channel access opportunities, as one RAT may not recognize collisions with transmissions from another RAT, resulting in inefficient use of shared resources.
Innovation Solution
A device, such as user equipment (UE), detects collisions by sensing energy levels during transmission gaps in a time-domain energy signature or through unsuccessful decoding of channel reservation signals, and reports these collisions to the transmitting node, allowing it to adjust its contention window to ensure fair access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transmitters of different RATs operate in a shared spectrum band without collision detection, then device complexity is reduced, but channel access fairness deteriorates
Solution Approach 1:
The patent introduces an intermediary collision detection mechanism that monitors transmissions from different RATs. A dedicated detection module observes the shared spectrum band and identifies collisions between LTE and Wi-Fi transmissions, then reports them to the transmitting node for contention window adjustment, thereby ensuring fairness without requiring complex modifications to the transmitters themselves.
Solution Approach 2:
The patent implements a feedback loop where collision detection results are reported back to the transmitting node. The transmitting node uses this feedback to dynamically adjust its contention window size, increasing it when collisions are detected and decreasing it when the channel is clear, thereby achieving fair channel access through continuous adaptation based on observed conditions.
2Reliability
If collision detection mechanisms are implemented, then channel access fairness is improved, but device complexity increases
Solution Approach 1:
The patent segments the collision detection function into a separate, dedicated module that operates independently from the main transmission logic. This modular approach allows the detection mechanism to be added without fundamentally redesigning the transmitter architecture, thereby limiting the increase in overall device complexity while still achieving fair channel access.
3Reliability
If contention window adjustment is performed frequently, then channel access fairness is improved, but loss of time increases due to more backoff procedures
Solution Approach 1:
The patent implements dynamic contention window adjustment where the window size adapts based on real-time collision detection results. The contention window is increased only when collisions are detected and decreased when the channel is clear, creating a dynamic system that responds to actual channel conditions rather than using fixed or overly frequent adjustments, thereby balancing fairness with time efficiency.
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 enhances fairness in channel access by allowing transmitters to adjust their contention windows based on detected collisions, improving the overall efficiency of shared radio frequency spectrum usage between different RATs.
Implementation Method 1
detecting a collision between transmitters of two different radio access technologies (RATs) transmitting in a shared radio frequency spectrum band... by sensing energy levels during transmission gaps in a time-domain energy signature
Implementation Method 2
detecting a collision between transmitters of two different radio access technologies (RATs) transmitting in a shared radio frequency spectrum band... through unsuccessful decoding of channel reservation signals
Data Source
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Figure 3A
AI summary
Detection and reporting techniques for collisions between transmitters of two different radio access technologies (RATs) transmitting in a shared radio frequency spectrum band is described. The collision may occur following a listen-before-talk procedure but prior to transmission of data, and may not affect the reception of the transmitted data. Collisions may be detected using for example, energy sensing, preamble or ready-to-send (RTS) signal detection, or unsuccessful decoding of all or part of a channel reservation signal. A transmitting device may determine a collision has occurred by detecting an energy level during a preamble transmission is greater than a threshold level or by detecting that an energy level during a transmission gap of a time-domain energy pattern is above a threshold level. A receiving device, such as a user equipment (UE), that detects the collision may report the collision to the transmitter.