RT Transmission Buffer Segmentation for Packet Loss Control
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Solution Overview
Problem
Existing control systems face challenges in achieving both zero packet loss and zero communication delay simultaneously in real-time (RT) communication, particularly due to fluctuations in transmission and reception bandwidths and interference from non-RT communication.
Innovation Solution
Implementing mechanisms such as limiting maximum transmission band, flow control of the data link layer between adjacent nodes, and priority assignment to ensure RT communication is processed before non-RT communication, using a common RT transmission buffer for RT communication and separate buffer for non-RT communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If RT communication and non-RT communication share a common transmission buffer, then device complexity is reduced, but RT communication reliability deteriorates due to packet loss and delay
Solution Approach 1:
The transmission buffer is segmented into a common transmission buffer and a dedicated RT transmission buffer. The common buffer handles both RT and non-RT communications, while the dedicated RT buffer ensures priority handling of real-time packets. This segmentation allows the system to maintain low complexity overall while providing targeted reliability improvement for RT communication through the dedicated buffer portion.
2Reliability
If priority assignment is implemented for RT communication, then RT communication reliability is improved, but device complexity increases
Solution Approach 1:
Priority assignment is performed in advance by classifying packets into RT and non-RT categories before they enter the transmission buffer. RT packets are directed to the dedicated RT transmission buffer with pre-assigned priority, while non-RT packets go to the common buffer. This preliminary classification simplifies the buffering logic compared to dynamic priority arbitration, reducing the actual complexity while maintaining reliability.
3Reliability
If maximum transmission band is limited, then RT communication reliability is improved by reducing packet loss, but communication productivity decreases
Solution Approach 1:
Bandwidth limitation is applied locally and selectively only to non-RT communication traffic, while RT communication traffic is allowed to utilize the full available bandwidth. This is achieved by maintaining separate buffer queues where RT packets are transmitted without artificial bandwidth constraints, ensuring high throughput for time-critical data while limiting non-RT traffic to prevent buffer overflow and packet loss.
4Reliability
If separate physical networks are used for RT and non-RT communication, then RT communication reliability is improved, but device complexity and cost increase
Solution Approach 1:
RT and non-RT communication networks are merged into a single shared physical network infrastructure, eliminating the need for separate hardware networks. Virtual separation is achieved through the dual-buffer mechanism (common buffer and dedicated RT buffer) and priority assignment logic, which provides logical isolation equivalent to physical separation while reducing infrastructure complexity and cost.
Data Source
AI summary
A device includes a processing unit configured to store a transmission frame transmitted through a communication flow in an RT transmission buffer for RT communication in a case where a priority of the communication flow is valid, and store the transmission frame in a transmission buffer for non-RT communication in a case where the priority is invalid, transmit the transmission frame stored in the RT transmission buffer earlier than the transmission frame stored in the transmission buffer, and perform flow control of a data link layer with a direct communication partner.