Variable Frame Numbering Field for Ethernet Redundancy
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Solution Overview
Problem
Current communication networks on aircraft, based on the ARINC 664 Part 7 standard, face challenges in managing redundancy at higher bit rates, such as 1 Gbits/s, due to the limited frame number reuse interval, which can be insufficient for handling interference lasting longer than 15.81 ms, making it difficult to ensure reliable communication.
Innovation Solution
The proposed solution involves a deterministic switched Ethernet network with two independent elementary networks, where transmitter and receiver devices adjust the length of the numbering field in data frames based on the bandwidth allocation gap (BAG) value, using a first predetermined length for conventional bit rates and a second, longer length for higher bit rates, allowing for increased frame number reuse intervals and improved redundancy management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the frame number reuse interval is extended to handle longer interference durations at higher bit rates, then reliability is improved, but the frame transmission speed decreases
Solution Approach 1:
The patent applies dynamics by making the numbering field length variable rather than fixed. The transmitter device dynamically adjusts the length of the numbering field (e.g., from 8 bits to 16 bits or more) based on the BAG value and bit rate conditions. This dynamic adaptation allows the system to extend the frame number reuse interval when needed for reliability while maintaining shorter intervals for normal high-speed operation, thus resolving the contradiction between reliability and transmission speed.
Solution Approach 2:
The patent changes the parameter of the numbering field length in the data frame structure. By modifying this parameter from a fixed 8 bits to a variable length (8, 16, 32 bits or more) depending on the BAG value and bit rate, the system can adjust the frame number reuse interval to match the interference duration requirements at different transmission speeds, thereby balancing reliability and productivity.
2Device complexity
If a fixed 8-bit numbering field is used, then device complexity is reduced, but adaptability to different bit rates deteriorates
Solution Approach 1:
The patent makes the numbering field length dynamic based on the BAG value and bit rate conditions. The transmitter device determines the appropriate length (8 bits for conventional rates, 16+ bits for higher rates) and configures both transmitter and receiver accordingly. This dynamic approach maintains simplicity for conventional applications while providing adaptability for higher bit rates, resolving the contradiction between device complexity and adaptability.
Solution Approach 2:
The patent creates a universal numbering field structure that can function at multiple bit rates (from conventional 100 Mbits/s to 1 Gbits/s and beyond). By making the numbering field length configurable rather than fixed, a single device design can serve multiple bit rate requirements, achieving universality without significantly increasing base device complexity.
3Reliability
If the numbering field length is increased for higher bit rates, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies dynamics by conditionally adjusting the numbering field length based on the BAG value and bit rate. The device only increases the numbering field length when specifically needed for higher bit rates with longer interference durations. For conventional bit rates, the simpler 8-bit field is used. This conditional approach improves reliability when necessary while avoiding unnecessary complexity in normal operation.
Solution Approach 2:
The patent changes the numbering field length parameter from a fixed value to a configurable parameter determined by the BAG value and bit rate. This parameter change allows the system to optimize between reliability (longer field) and complexity (shorter field) based on actual operating conditions, rather than always using the more complex longer field.
Data Source
AI summary
A communication network on board a vehicle is a deterministic switched Ethernet network using virtual links, including a set of subscriber devices and a set of switches in which communications are performed redundantly. To manage redundancy, each data frame transmitted on a virtual link includes a frame number in a numbering field of the frame. The transmitter and/or receiver subscriber devices on the virtual link take into account a length of the numbering field equal to a first predetermined length when the BAG value associated with the virtual link is greater than or equal to a predetermined BAG value, otherwise equal to a second predetermined length greater than the first length.