Token-Passing PLC Coordination on Shared Feeder Lines
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Solution Overview
Problem
Power line communications between local renewable energy systems (LRESs) sharing the same feeder line often result in data collisions due to independent installations and lack of awareness among systems, leading to interference and inefficient communication.
Innovation Solution
A decentralized communication protocol using a round-robin token-passing protocol, carrier-sense multiple access with collision avoidance (CSMA/CA), and CSMA/CA for urgent messages, allowing coordinators to efficiently communicate with their respective device nodes on a shared media while mitigating cross-domain interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple LRESs independently install PLC communication systems on a shared feeder line, then each system can operate autonomously, but data collisions and interference occur between systems
Solution Approach 1:
A virtual token is introduced as an intermediary control mechanism that mediates access to the shared communication medium. The token-passing protocol ensures that only the coordinator holding the token can transmit data, preventing collisions while allowing independent LRES installations. Each coordinator autonomously follows the token-passing rules without needing awareness of other systems.
Solution Approach 2:
The communication protocol implements periodic token passing among coordinators in a round-robin fashion. Each coordinator receives the token for a fixed time quota, transmits data periodically during its turn, then passes the token to the next coordinator. This periodic structure ensures fair access and prevents interference between independently installed systems.
2Productivity
If multiple coordinators transmit data simultaneously on a shared media channel, then communication speed increases, but data collisions occur
Solution Approach 1:
The virtual token serves as a mediator that controls transmission rights. Instead of allowing simultaneous transmissions that cause collisions, the token ensures sequential access while maintaining high utilization of the communication channel through fixed time quotas for each coordinator.
Solution Approach 2:
The protocol incorporates acknowledgment mechanisms where receiving coordinators confirm receipt of tokens and data. This feedback ensures reliable transmission while the round-robin structure maintains efficient channel utilization by systematically rotating transmission opportunities among all coordinators.
3Reliability
If a single coordinator controls all communication on a shared media channel, then data collisions are eliminated, but communication bandwidth is underutilized
Solution Approach 1:
The round-robin token-passing protocol implements periodic transmission opportunities for each coordinator. Instead of one coordinator monopolizing the channel, the token cycles through all coordinators in sequence, with each receiving a fixed time quota for transmission. This periodic sharing eliminates collisions while maximizing bandwidth utilization through systematic rotation.
Solution Approach 2:
The communication channel access is segmented into discrete time quotas assigned to different coordinators. Rather than a single coordinator controlling the entire channel continuously, the channel is divided into time slots that are periodically allocated to different coordinators in a round-robin fashion, enabling parallel utilization without collision.
4Loss of time
If urgent messages are transmitted immediately when needed, then response time is reduced, but data collisions increase on shared media
Solution Approach 1:
The protocol dynamically adjusts transmission behavior based on message urgency. While the base protocol follows strict round-robin token passing for normal data, urgent messages trigger a dynamic response where the receiving coordinator can interrupt the current token holder's transmission after the ongoing data transfer completes, allowing faster response while maintaining collision-free operation through controlled interruption rather than immediate transmission.
Data Source
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AI summary
A method and computer readable medium for communication on a shared media. In one embodiment, the method comprises holding a token by a first coordinator on a virtual ring, only a token-holding coordinator is permitted to transmit data associated with a first service level; transmitting data associated with the first service level, by the first coordinator, to device(s) on a first local domain; passing, by the first coordinator, the token to a second coordinator; periodically transmitting data associated with the first service level, by the second coordinator, to device(s) on a second local domain; receiving, by a third coordinator while the second coordinator holds the token, a message to transmit data associated with a second service level to device(s) of a third local domain; and transmitting, by the third coordinator while the second coordinator is not transmitting, the data associated with the second service level.