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Appendix G: Ethernet Requirements.
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Appendix G: Ethernet Requirements.
The Ethernet media is the key component for data transmission in the VIS-300/400 system.
In order to ensure a smooth running system, install the Ethernet infrastructure with the following
considerations in mind:
•
Physical cabling - minimum Cat 5E is recommended – in larger systems, Cat 6 or fibre optic cables
are recommended for backbones with high traffic loads. It is strongly recommended, that the qual-
ity of the installed Ethernet cabling is verified with a suitable network tester (certifier) such as
Fluke Optiview, Fluke Etherscope, Lantek 6 or similar.
•
Network speed – The minimum speed required is 100 Mbit – though 1000 Mbit (1Gbit) is the opti-
mal speed and ensures sufficient bandwidth in most applications. In general, assessment of network
speed is an important issue, and should have been taken into consideration in the design phase. The
transmission speed on a local gantry with (for example) 4 EN-Camera units, could very well be
based on a 100 Mbit network topology which then is linked externally with a 1 Gbit FO (Fibre
Optic) uplink to the server location – see Figure 96
FIGURE 96.
Network cabling example:
•
The actual traffic load that the individual cameras inflict on the network depends heavily on the
cameras current run mode – in a normal operable system, the cameras run in asynchronous mode,
which means that the cameras only grab images when triggered. Converted to network load, asyn-
chronous image triggering with a rate of 3600 incidents per hour (a car per second) will typically
inflict a 3-4% load per camera on a 100 Mbit network. If the same camera is set to synchronous
mode, which is the mode typically used during alignment and diagnostics procedures, the camera
grabs the images with a speed of approximately 10 images per second (measured on a 1.4 Ghz Intel
Centrino based laptop) – the load will now rise to around 30% per camera. Even the drastic increase
in network load when using synchronous mode, will normally not be a problem, since the mode is
only applied to the cameras of interest.
Summary of Contents for Vehicle Imaging Subsystem 300
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