[Tinyos-help] wireless communication speed

João Paulo Amaro da Costa Luz Carneiro jcarneiro at netcabo.pt
Wed Feb 18 15:39:45 PST 2009


Hi, thanks for your answer and sorry for this late response as I was  
only able to reply now.
I will try using the slotted mac, is there any disadvantage in using  
it? Why isn't it default?
I am using the default IRIS channel (11 I thing?) and already using a  
timer for the periodic sending.
I will test again and check for problems with my application using the  
default MAC first.
Are these results 130-160 (default MAC) or 300 (slotted MAC) packets/ 
second between 2 motes or also with larger networks?
Thanks and regards,

Joao

On 2009/02/12, at 18:21, Miklos Maroti wrote:

> Hi Joao,
>
>> I have a question related to the maximum transmission speed for the
>> IRIS 2.4GHz mote.
>> The datasheet Crossbow provides states that it can transmit at
>> 250Kbps. Has anyone tested this speed?
>> 250Kbps = 31,25KB/s
>
> That is correct.
>
>> If a normal packet has a default payload size of 28Bytes and the full
>> packet with headers  (if I remember correctly) is around 44B, then a
>> mote needs to be able to send  (31250 / 44 = ) 710 packets per  
>> second.
>
> You need backoff time, and time to switch between TX and RX and some
> synchronization, acknowledgement, upload/download to/from the radio
> chip, etc.
>
> However, I was able to achieve 300 full packets per seconds. You need
> to use the so called slotted mac. Try running your application with
> RF230_SLOTTED_MAC defined and it is best if you transmit messages
> periodically from a timer.
>
>> The results I've experienced in my tests are very very far from this.
>> The tests I made a few months ago I could send a packet every 250ms
>> without packet loss but increasing the size or decreasing this 250ms
>> would result in packet loss.
>
> That is very strange. The default mac should perform much better than
> 4 packets / second. Which channel do you use?
>
> Miklos



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