[Tinyos-help] Resizing message_t MTU problem

antonio gonga ask25019fe at hotmail.com
Wed Feb 20 18:42:56 PST 2008


Dear all,
I've been trying to increase the performance of my modified BaseStation, but I'm now unable to do more.
Problem:
Sensors send messages to BaseStation, which receives these messages
containing different sizes. At the BaseStation, each message is time
stamped(Arrival Time), and forwarded to the serial port(UART). There's
no possibility to insert time stamps on the incoming message. The
solution I found is to change the MTU at the BaseStation to 42, so
that, I create a new message and the payload of the incoming message is
copied to the new message with higher payload and the time stamp is
also inserted . These new message will then be forwarded to the serial
port.  On a PC the arrival time can be decoded through a packet parser
that I developed.

The application is working fine, but my big
challenge now is that I'm getting so many "Bad Packets" in the Java
application running in the PC. I know that, the problem is at the
BaseStation. With low traffic the Application works quite fine, but with High traffic, it sends so many bad packets. The resizing process cause delay to create a new message and to forward the message to the Serial port, but what I don't
understand, where these bad packets are from?. And what could cause a
packet to be considered as a Bad Packet?. Because up to 97% of the packets are being correctly received without errors in the Java App.

Any help is welcome.



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