RT Communication Buffer Segmentation for Shared Networks
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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, priority assignment, and priority control of transmission processing to prioritize RT communication over non-RT communication, ensuring RT frames are stored and transmitted before non-RT frames, and using common protocols for both types of communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If RT communication and non-RT communication share the same network, then network utilization is improved, but packet loss and communication delay in RT communication increase
Solution Approach 1:
The transmission buffer is segmented into a first buffer for RT communication and a second buffer for non-RT communication. This segmentation allows independent management of RT and non-RT traffic, ensuring RT packets are transmitted with priority while still allowing non-RT traffic to share the network, thus resolving the contradiction between network utilization and RT communication quality.
Solution Approach 2:
Different quality of service (QoS) policies are applied to different communication types within the same network. RT communication receives guaranteed bandwidth and priority handling, while non-RT communication uses available bandwidth without affecting RT performance. This local quality differentiation enables both RT reliability and overall network utilization.
2Reliability
If maximum transmission band is limited, then packet loss is reduced, but communication efficiency decreases
Solution Approach 1:
The maximum transmission band limit is dynamically adjusted based on network conditions and QoS requirements. For RT communication, the limit is set to ensure reliable delivery with minimal packet loss, while for non-RT communication, the limit is relaxed to maximize throughput. This dynamic adjustment resolves the contradiction between reliability and efficiency.
Solution Approach 2:
Different transmission parameters including maximum transmission band, buffer sizes, and priority levels are changed based on communication type. RT communication uses conservative parameters to prevent packet loss, while non-RT communication uses aggressive parameters to maximize efficiency, allowing both goals to be achieved simultaneously.
3Reliability
If priority control is implemented, then RT communication reliability is improved, but system complexity increases
Solution Approach 1:
Priority control rules are pre-configured in the system, assigning different priorities to RT and non-RT communication before traffic arrives. This preliminary action eliminates the need for complex real-time priority determination, reducing system complexity while maintaining RT reliability through consistent priority handling.
Data Source
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AI summary
A device (10) includes a processing unit (10b) 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.