[Tinyos-help] wireless communication speed

[João Paulo Amaro da Costa Luz Carneiro]

Hi,
I've finally tested my application and maximum transmission rate again  
and get the same results.
I believe this low packet rate experience is probably because I'm  
using CTP (forgot to mention in the original question) and I'm sending  
from two nodes to one sink, if just use one node to sink I can  
increase the packet rate but by an insignificant amount. Can you tell  
me if this transmission rate is normal when using CTP?
Can I still follow our suggestion of using the slotted mac (does it  
work with CTP)? Is there a paper or documentation on the slotted mac?
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