Wireless Mesh Network Time Synchronization for Industrial Control
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Solution Overview
Problem
Wireless mesh networks in industrial control applications face challenges with high latency and unreliability due to interference in shared ISM radio bands, particularly in closed-loop control systems where sensors-to-controller and controller-to-actuators communication phases incur longer end-to-end delays, missing critical time deadlines.
Innovation Solution
A time-synchronized network with nodes that transmit and receive data concurrently using a differentiated forwarding scheme, bypassing the central controller for direct communication between sensors and actuators, and employing spatial diversity and capture effects to achieve robust, low-latency, and energy-efficient many-to-many communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wireless solutions are used in industrial control applications, then cost is reduced and deployment is easier, but latency increases and reliability decreases due to interference in shared ISM radio bands
Solution Approach 1:
The network is segmented into multiple independent transmission channels or paths. Instead of relying on a single wireless link that is vulnerable to interference, the system divides data transmission across multiple parallel paths, allowing packets to be routed through alternative routes when interference occurs on one path, thereby maintaining reliability while using wireless technology
Solution Approach 2:
The system dynamically changes transmission parameters such as frequency channels, transmission power, and modulation schemes in response to detected interference conditions. By adapting these parameters in real-time, the system maintains reliable communication over wireless channels despite the noisy ISM band environment
2Device complexity
If sensors transmit data to a central controller which then transmits to actuators in sequential phases, then communication is simplified, but end-to-end latency increases causing missed deadlines
Solution Approach 1:
The invention extracts and removes the central controller from the critical data path between sensors and actuators. By allowing direct peer-to-peer communication between sensor nodes and actuator nodes, the system eliminates the sequential two-phase communication through the controller, drastically reducing end-to-end latency while maintaining communication simplicity through standardized protocols
Solution Approach 2:
The system transitions from a hierarchical two-phase communication model to a parallel many-to-many communication model. Multiple sensors can simultaneously transmit to multiple actuators in parallel, utilizing spatial and temporal dimensions to achieve concurrent data flow, thereby reducing overall latency without increasing structural complexity
3Loss of time
If multiple source nodes transmit data concurrently to multiple destination nodes, then latency is reduced, but interference and collision increase on shared channels
Solution Approach 1:
Nodes perform preliminary actions by listening to the channel before transmission and predicting potential collisions. The system uses carrier sense multiple access (CSMA) mechanisms where nodes check channel occupancy before transmitting, and employs prediction algorithms to anticipate future collisions based on observed traffic patterns, allowing nodes to adjust their transmission timing to avoid interference
Solution Approach 2:
The system implements feedback mechanisms where receiving nodes send acknowledgment signals back to transmitting nodes. When collisions or interference are detected, feedback information is used to adjust transmission parameters, retry timing, or select alternative paths. This closed-loop feedback enables the network to dynamically adapt to interference conditions while maintaining concurrent transmissions
Data Source
AI summary
A time synchronised network comprising a plurality of nodes, the plurality of nodes each comprising a receiver, a transmitter, a controller and memory storing program instructions. The plurality of nodes are suitable for participating in time synchronised data re-transmission within the network. The plurality of nodes comprise a plurality of source nodes, a plurality of destination nodes and at least one intermediate node. The plurality of source nodes transmitting data concurrently with the other source nodes via the respective transmitter in a first flooding round to a plurality of corresponding destination nodes. The plurality of destination nodes receiving data via the respective receiver from a plurality of corresponding source nodes. The intermediate node receiving, via the respective receiver, data from at least one of the plurality of source nodes, and re-transmitting the received data in the form it was received using the transmitter.