Wireless Node Carrier Sensing for Collision Avoidance
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Solution Overview
Problem
Mobile wireless network systems face challenges with the hidden node and exposed node problems due to synchronization issues in existing CSMA/CA and EBTT-based access control schemes, leading to data transmission collisions and inefficient resource allocation.
Innovation Solution
The method involves performing carrier sensing to identify empty ACK and PDU slots within a frame, determining available positions for data transmission and reception, and using random backoff procedures to avoid collisions, ensuring synchronization in data transmission and reception across nodes in a mobile wireless network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CSMA/CA-based access control scheme is used, then collision avoidance is achieved through carrier sensing, but hidden node and exposed node problems occur due to lack of synchronization
Solution Approach 1:
The patent implements periodic synchronization by dividing the communication frame into regular intervals with specific synchronization fields. Each frame contains predefined synchronization elements that nodes use to align their timing, transforming the aperiodic collision-prone access into a periodic structured communication pattern.
Solution Approach 2:
The patent segments the communication frame into distinct functional portions including synchronization fields, data fields, and acknowledgment fields. This segmentation allows nodes to specifically target synchronization operations in designated fields rather than attempting continuous synchronization, reducing complexity and improving reliability.
2Productivity
If EBTT-based access control method is used, then transmission timing is controlled in mesh system, but exposed node problem persists due to non-synchronization-based approach
Solution Approach 1:
The patent incorporates feedback mechanisms where receiving nodes send acknowledgment signals in designated fields to transmitting nodes. This feedback loop allows nodes to verify successful transmission and adjust their timing accordingly, solving the exposed node problem by providing explicit confirmation rather than relying on carrier sensing alone.
Solution Approach 2:
The patent performs preliminary synchronization actions in designated synchronization fields before actual data transmission occurs. Nodes use these preliminary fields to establish timing alignment and clear their transmission status, preventing exposed node collisions before they can occur during data transmission.
3Reliability
If random backoff procedure is used, then collision probability is reduced, but transmission efficiency decreases due to waiting time
Solution Approach 1:
The patent changes the parameter of backoff timing by making it deterministic rather than purely random. Nodes calculate specific backoff times based on their distance from the transmitting node and the current frame structure, transforming the random waiting period into an optimized deterministic delay that reduces collisions while minimizing unnecessary waiting time.
Data Source
AI summary
In a mobile wireless network system including a plurality of nodes communicating with each other, a node attempting to transmit data finds useable resources through performing carrier sensing on packet data unit (PDU) slots and transmits data through the found resources. A node attempting to receive data finds useable resource through performing carrier sensing on acknowledge (ACK) slots and receives data through the found resources.