Frequency Multiplexed RTS Transmission for CSMA/CA Collision Reduction
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Solution Overview
Problem
CSMA/CA systems face efficiency degradation with increasing numbers of source nodes, leading to high collision probabilities and reduced transmission capacities due to the limitations of conventional single-channel operations and the inability to maintain orthogonality among primary users when their number exceeds the number of sub-bands.
Innovation Solution
Implementing a method that allows multiple source nodes to simultaneously transmit data sending authorization request messages on different sub-bands using frequency multiplexing, such as OFDMA, with a modified RTS/CTS mechanism where each source node can transmit multiple RTS messages on various sub-bands, reducing collision probability and improving access efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If multiple source nodes compete for access on a single channel using conventional CSMA/CA, then the system is simple to operate, but the collision probability increases and transmission efficiency degrades rapidly as the number of source nodes increases
Solution Approach 1:
The frequency band is divided into multiple sub-bands, and each source node transmits authorization request messages on different sub-bands simultaneously. This segmentation of the frequency resource allows multiple nodes to access the channel in parallel, reducing collision probability while maintaining the simplicity of the CSMA/CA access mechanism.
2Quantity of substance
If the number of primary users exceeds the number of sub-bands, then more users can be served, but orthogonality between primary users cannot be maintained
Solution Approach 1:
When the number of primary users exceeds the number of sub-bands, the system introduces a time dimension by allocating different time slots to different users on the same sub-band. This allows the system to maintain orthogonality by separating users both in frequency (sub-bands) and time (time slots), thereby supporting more users while preserving orthogonal access.
3Productivity
If source nodes transmit multiple RTS messages on different sub-bands, then collision probability is reduced and access efficiency is improved, but the device complexity increases
Solution Approach 1:
The system performs preliminary allocation of sub-bands to source nodes before the actual data transmission. The destination node or a central controller assigns specific sub-bands to different source nodes in advance, so that when source nodes transmit RTS messages, they already know which sub-band to use. This preliminary action reduces the complexity of managing multiple transmissions while maintaining the collision-reduction benefits.
Data Source
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AI summary
The invention relates to a method of 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 (SB0, SB1, ..., SBi, ..., SBn) of the communication channel, characterized in that it comprises at a source node, following the detection of the availability of the communication channel, the transmission to a destination node of several requests for authorization to send data on the communication channel (RTS NS0 RTS NS1), each of said messages being transmitted on a sub-band of the communication channel.