Frequency Multiplexed RTS-CTS Access for Collision Reduction
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Solution Overview
Problem
Conventional CSMA/CA systems face efficiency degradation as the number of source nodes increases, leading to performance limitations in managing multiple access to a frequency band, especially when the number of primary users exceeds the number of sub-bands, resulting in collisions and reduced orthogonality among users.
Innovation Solution
The method involves dividing the communication channel into sub-bands, allowing simultaneous data sending authorization request messages on different sub-bands, with a modified wait counter mechanism that decrements when the channel is available, and a destination node that detects and prioritizes these messages to reduce collisions and improve system performance by allowing transmission on specific sub-bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional CSMA/CA protocol is used with single channel operation, then the system is simple to implement and requires no signaling for bandwidth request, but the efficiency degrades rapidly when the number of source nodes increases
Solution Approach 1:
The frequency band is divided into multiple sub-bands, allowing source nodes to transmit authorization request messages on different sub-bands simultaneously. This segmentation of the frequency resource enables parallel access operations, improving system efficiency when multiple source nodes are present while maintaining the simplicity of the CSMA/CA protocol structure.
2Reliability
If the number of primary users exceeds the number of sub-bands, then all sub-bands are occupied and orthogonality between users cannot be maintained, but admitting control to reject requests reduces system capacity
Solution Approach 1:
When all sub-bands are occupied by primary users, the system allows secondary users to access the channel by transitioning to a different dimension of operation - using the same sub-bands with modified access procedures. Secondary users monitor sub-band availability and transmit authorization requests when sub-bands become temporarily available, thereby maintaining orthogonality for primary users while still accommodating additional users in the system.
3Reliability
If multiple source nodes transmit simultaneously on the same sub-band, then collisions occur and transmission success rate decreases, but increasing the number of sub-bands requires more complex resource management
Solution Approach 1:
The frequency band is segmented into multiple sub-bands to provide spatial separation for simultaneous transmissions. Source nodes select different sub-bands for transmitting their authorization requests, which prevents collisions between simultaneous transmissions. The destination node receives these segmented transmissions on different frequency resources and processes them independently, reducing collision probability while maintaining manageable resource allocation through sub-band indexing.
Data Source
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AI summary
The invention relates to a method for multiple access to a frequency band of a communication channel of a communication network with carrier listening and collision avoidance, said frequency band being divided into a set of sub-bands, comprising: at a source node, the detection of the availability of the communication channel and the transmission to a destination node of a request message authorizing the sending of data on the communication channel (RTS NS0, RTS NS1, RTS NS2) carried out on one or more sub-bands (SBi, SB1, SB0), at the destination node, the detection of simultaneous requests for authorization to send data on the communication channel (RTS NS0, RTS NS1, RTS NS2) transmitted by a plurality of source nodes (NS0, NS1, NS2) on a plurality of sub-bands (SBi, SB1, SB0),and the transmission of a data transmission authorization message over the communication channel by at least one source node among said plurality of source nodes (CTS NS0, CTS NS0&NS1).