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How to calculate bandwidth requirements for rosserial link?

asked 2014-11-19 08:41:45 -0500

MikeH
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updated 2014-11-19 09:24:57 -0500

We are beginning to prototype a small robot with differential drive, an IMU, and multiple sensors. For the first iteration we plan to put an Arduino with rosserial on the robot and run ROS on a PC. I want to calculate the bandwidth needed for the expected message traffic to determine if rosserial will work for us or if we need to use a different approach, however I can't find any references to the size of ROS messages once they've been serialized.

Can anyone give me some advice on how to approach calculating this rather than running a simulation and measuring the bandwidth?

Cheers, Mike

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Nice question. Would perhaps be a good candidate for a feature request on the rosserial tracker: a tool that could automatically do this.

gvdhoorn ( 2014-11-19 09:07:58 -0500 )edit

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answered 2014-11-19 12:57:44 -0500

flag of United States of America

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Serialized messages in ROS are roughly the size that you'd expect them to be; that is, an int64 is 8 bytes, an float32 is 4 bytes, etc. Strings and variable-length arrays are serialized as a 4-byte length followed by the contents (no null terminator). Fixed-size arrays are serialized as a sequence of data, without the length. There is no padding.

I believe the rosserial protocol adds a bit of overhead because it transmits a topic ID along with each message; this should be well-documented in the rosserial protocol docs.

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Asked: 2014-11-19 08:41:45 -0500

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Last updated: Nov 19 '14

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