[Tinyos-devel] RE: [Tinyos-help] shorter (cc2420/telosb) radio range in t2 compared tot1?

David Moss dmm at rincon.com
Tue Oct 30 07:55:23 PDT 2007


Here's one possible explanation: the CSMA backoff changed between T1 and T2.

In T1, the CSMA backoff wasn't very fair, allowing one transmitter to
possibly hog the channel.  The CSMA congestion and initial backoffs were
flipped in T2, making the initial backoff longer and the congestion backoff
shorter.  This causes less throughput but an increase in fairness.

This brings up a good point though: more energy is consumed in T2 to deliver
the same amount of information because throughput is diminished. We should
explore turning the radio to IDLE during CSMA backoff wait periods to see
how that impacts energy consumption and throughput.
 
-David



-----Original Message-----
From: tinyos-help-bounces at Millennium.Berkeley.EDU
[mailto:tinyos-help-bounces at Millennium.Berkeley.EDU] On Behalf Of Jeongyeup
Paek
Sent: Tuesday, October 30, 2007 12:33 AM
To: tinyos-help
Subject: [Tinyos-help] shorter (cc2420/telosb) radio range in t2 compared
tot1?

Dear all.

I am running a very simple test applications where
40 nodes are broadcasting packets every 10 sec,
and a BaseStation node is listening to those packets.

And I am receiving far less packets in t2, compared to t1,
for (what I believe to be) the same application.
So I was wondering whether anyone had experienced
shorter radio range in t2 compared to t1.

The exact scenario is, 40 telosb nodes,
with & without 'CFLAGS += -DCC2420_DEF_RFPOWER=31',
on an indoor testbed (http://enl.usc.edu/projects/tutornet/)
where node 1~40 are sending broadcasts and node 10 is the BaseStation.
I ran experiments several times, for several tens of minutes each time,
and tried channel 23 and 26.
Also, although I am new to T2, I have some experiences with T1.

In T1, I receive packets from 15~20 nodes on average.
In T2, I receive packets from 8~12 nodes on average.

And the only guess that I can think of
(assuming that I've done t1->t2 poring correctly)
is shorter radio range in t2 compared to t1.... for some weird reason.

is this possible?

-- 
Jeongyeup Paek
Ph.D. student
Embedded Networks Laboratory
Department of Computer Science
University of Southern California
http://enl.usc.edu/~jpaek
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