On Jul 11, 2007, at 10:48 AM, Chonggang Wang wrote:
Hello,
I am trying to test the pure throughput of 802.15.4 and conduct an
experiment as follows:
\/ \/
| |
----------- ------- --------
-----------
| PC1 | |Mote1| |Mote2| | PC2 |
| |-----| | |
|---------| |
---------- ------- --------
----------
Both motes are placed close (guarantee good channel condition) and
configured as Base Station by being installed TOSBase application.
There is a sender program at PC1 and a receiver program at PC2.
Both PC1 and PC2 start SerailForwarder (SF) (I changed the original
SF in order to support UDP and avoid the effect of TCP Congestion
Control and ACK). The baud rate for both motes is 115200.
Then the sender program at PC1 continuously send a file (large
enough) to SF at PC1 through UDP socket. The receiver program at
PC2 listens to the SF's UDP port at PC2 and calculate the received
data rate. I repeated this experiment for lots of times and found
the received data rate at PC2 is only about 35 Kbps. Since tmote
sky uses chipcon 2420 with 250 Kbps data rate, 35 Kbps is
surprisingly pretty slow since in this case there should not be any
collision. I am not sure if those two motes automatically go to
sleep state. Also i did not find any bad packet due to CRC failure
in SerialForwarder.
Could any one give me a clue?
MAC backoff.
Phil
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