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

[Jeongyeup Paek]

Yes... though the scenario is reversed.
When all nodes are sending broadcasts, and one basestation is receiving,
that base station is receiving packets from *less number of nodes*.

thanks

- jpaek


Omprakash Gnawali wrote:
> I think he is talking about a shorter range and not lower
> throughput. He says whenever he sends a broadcast packet, fewer nodes
> receive that broadcast pkt in T2 than in T1.
> 
> - om_p
> 
>> 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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>>
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-- 

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