PLCA Ethernet Multidrop Collision Avoidance
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Solution Overview
Problem
Existing Ethernet multidrop networks face challenges with deterministic data transmission due to random latencies and reduced throughput caused by collision detection mechanisms like CSMA/CD, and TDMA solutions result in low throughput and rigidity, making them unsuitable for real-time applications.
Innovation Solution
A method is introduced that synchronizes data exchange modules across devices, offering transmission opportunities cyclically and dynamically, using a Physical Layer Collision Avoidance Reconciliation Sublayer (PLCA) to manage data transmission and avoid collisions by buffering data until a designated transmission opportunity, ensuring deterministic and efficient data transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CSMA/CD collision detection mechanism is used, then network nodes can detect and retry transmissions after collision, but this causes random latencies and reduced aggregate throughput
Solution Approach 1:
The patent implements periodic time slots for each network node to transmit data. Instead of allowing random access with collision detection, each node is assigned specific time intervals during which it can transmit without contention. This periodic structure eliminates random latencies while ensuring that transmissions occur at predictable intervals, resolving the contradiction between reliability and time loss.
Solution Approach 2:
The patent dynamically adjusts the time slot allocation and transmission opportunities based on network conditions and node requirements. The system can modify time slot durations, frequencies, and assignments to optimize performance, allowing the network to adapt to varying traffic patterns while maintaining deterministic timing. This dynamic approach enables the system to achieve both reliability and reduced latency by optimizing transmission schedules in real-time.
2Loss of time
If TDMA time division multiple access is used, then network determinism is achieved with fixed time slots, but throughput drastically decreases and system becomes rigid
Solution Approach 1:
The patent introduces dynamic time slot allocation where each node can transmit multiple packets within its assigned time slot if data is available. Unlike traditional TDMA that forces nodes to wait until the next slot even if data remains, this system allows continued transmission within the same slot, dynamically utilizing available bandwidth. This increases throughput while maintaining the deterministic timing structure that prevents collisions.
Solution Approach 2:
The patent enables continuous data transmission within assigned time slots by allowing nodes to send multiple packets back-to-back without waiting for slot boundaries. This eliminates the wasted transmission opportunities in traditional TDMA where nodes must stop transmitting at slot endings even when data queues remain. The continuous action principle maximizes media utilization while preserving deterministic timing, resolving the throughput penalty of traditional TDMA.
3Reliability
If TDMA fixed time slots are used, then collision avoidance is achieved, but system rigidity increases and dynamic bandwidth allocation becomes difficult
Solution Approach 1:
The patent implements dynamic time slot configuration where the duration, frequency, and assignment of time slots can be adjusted based on network conditions and node requirements. The system can allocate more time slots to nodes with higher traffic demands and fewer slots to nodes with lower demands, enabling dynamic bandwidth allocation while maintaining collision-free operation. This adaptability resolves the contradiction between reliability and versatility.
Solution Approach 2:
The patent segments the transmission medium into configurable time slots that can be dynamically assigned to different nodes. By dividing the medium access into discrete, controllable time segments, the system can flexibly allocate bandwidth to different nodes based on their needs while preventing collisions. This segmentation approach provides both the structure needed for collision avoidance and the flexibility for dynamic allocation.
4Loss of time
If TSN protocols with distributed packet scheduler are used, then precise time synchronization and flexible traffic shaping are achieved, but overall complexity becomes very high
Solution Approach 1:
The patent implements a self-synchronizing mechanism where each node independently maintains its time slot schedule using local timing references. Instead of requiring complex centralized coordination or distributed packet scheduling algorithms, nodes autonomously determine when to transmit based on pre-configured time slot information. This self-service approach achieves precise time synchronization with minimal complexity, as each node simply follows its assigned schedule without needing complex interaction with other nodes or centralized controllers.
Data Source
AI summary
A method for avoiding collision over a communication network, wherein devices are connected to the same medium. Each device has an access control module, a transceiver and a data exchange module. The access control module is configured to transmit data to the data exchange module when it receives information that no data is present on the medium. The transceiver is configured to transmit data on the medium each time it receives data from the data exchange module. The data exchange modules of all the devices are synchronized and then offered, in sequence, the opportunity to transmit data on the medium. The opportunity to transmit is offered dynamically after a previous transmission end or, if no transmission occurred, after a predetermined time range has expired. The data exchange module transmits data to the transceiver of the same device only when it is offered the opportunity to transmit.