Somnath,
There aren't really straightforward answers to your questions because
they both are non-deterministic to a degree.
For the first question: What data rate are you talking about? The raw
number of bits(including headers/footers?) that can be successfully
delivered over the air using the hardware or the number of payload bits
that you can deliver? The CC2420 can support variable length payload
sizes. Are you talking about the default payload size, or can
modifications be made to increase it? Are there more than 1 transmitter
operating on the particular channel? Is there interference from other
wireless devices (baby monitors, WiFi, Bluetooth, etc)? Are the
transmissions broadcast (no ack) or unicast (acks)?
All of these effect the data rate. If you have the hardware, you can
just run a few simple tests to get some anecdotal results, but they
won't be able to fully describe every possibility mentioned.
The second question also needs to be qualified. If you are using the
AMSenderC, it provides fair queuing between all concurrent instances of
AMSenderC. Are there any other instances of AMSenderC competing for
access to the radio? How often are interrupts occurring (timer
interrupts, adc done interrupts, etc)? These can significantly bog down
an attempt to use the radio. How many times does the sender have to
back-off because it detects that the medium is busy?
As you can see there are many different variables that can impact the
answers to both of your questions. Aside from some anecdotal results, I
doubt anyone will be able to provide you better data than what you could
achieve by experimentally determining these answers yourself using your
own hardware/RF environment.
Sorry I couldn't be more helpful, but the short answer is "it's hard to
calculate these for any generic situation, and you will get more
accurate results if you test these yourself using your own
hardware/software and RF environment"
-Paul
Somnath Mitra wrote:
Hello ,
I need the exact data rate number that is achievable on a tmote
(I do not mean CC2420 data rate - which is 250 kbps). I mean the data
rate that is achievable taking into account the MAC layer.
I would also like to know the time to transmit [probably a formula] a
packet of n bytes, from the point an application calls SendMsg.send()
on the sender mote to the point where the message is received by the
application layer on the receiver mote.
The motes are Tmotes running TinyOS 1.15 and the Boomerang TinyOS
stack from MoteIV.
Thanks,
Somnath
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