Can someone please tell me why the initial backoff and congestion backoff
values are defined in two places??!! One in CC2420CsmaP.nc and again in
DefaultLplP.nc. The hx values used in the calculations in both places are
different. What does this mean?
In CC2420CsmaP.nc (lines 216 to 229)
/***************** SubBackoff Events ****************/
async event void SubBackoff.requestInitialBackoff(message_t *msg) {
call SubBackoff.setInitialBackoff ( call Random.rand16()
% (0x1F * CC2420_BACKOFF_PERIOD) + CC2420_MIN_BACKOFF);
signal RadioBackoff.requestInitialBackoff(msg);
}
async event void SubBackoff.requestCongestionBackoff(message_t *msg) {
call SubBackoff.setCongestionBackoff( call Random.rand16()
% (0x7 * CC2420_BACKOFF_PERIOD) + CC2420_MIN_BACKOFF);
signal RadioBackoff.requestCongestionBackoff(msg);
}
In DefaultLplP.nc (lines 316 to 330)
/***************** RadioBackoff Events ****************/
async event void RadioBackoff.requestInitialBackoff(message_t *msg) {
//[am_id_t amId](message_t *msg) {
if((call CC2420PacketBody.getMetadata(msg))->rxInterval
> ONE_MESSAGE) {
call RadioBackoff.setInitialBackoff( call Random.rand16()
/*[amId]( call Random.rand16() */
% (0x4 * CC2420_BACKOFF_PERIOD) + CC2420_MIN_BACKOFF);
}
}
async event void RadioBackoff.requestCongestionBackoff(message_t *msg) {
//[am_id_t amId](message_t *msg) {
if((call CC2420PacketBody.getMetadata(msg))->rxInterval
> ONE_MESSAGE) {
call RadioBackoff.setCongestionBackoff ( call Random.rand16()
/**[amId]( call Random.rand16()*/
% (0x3 * CC2420_BACKOFF_PERIOD) + CC2420_MIN_BACKOFF);
}
}
On Thu, December 9, 2010 2:20 pm, Miklos Maroti wrote:
> Hi Urs,
>
> During the random back-off time we do nothing. After the timer
> expires, then we do CCA and if the channel is free, then we send the
> message. If the channel is busy, then we go another round of random
> back-off (congested). On the TelosB the random back-off time was up to
> 8 ms the last time I have checked. IRIS uses 4 ms now.
>
> Best,
> Miklos
>
> On Thu, Dec 9, 2010 at 9:42 AM, Urs Hunkeler <urs.hunke...@epfl.ch> wrote:
>> Hi,
>>
>> My bad, I mixed CCA (clear channel assessment) up with random back-off
>> time. I think that the original question was rather about the random
>> back-off time (used for the CSMA in the default MAC protocol used by
>> TinyOS), during which (please correct me if I'm wrong here) the channel
>> is continuously checked to see whether it is busy, and if so, the timer
>> for the random back-off is suspended while the channel is sensed to be
>> busy.
>>
>> Cheers,
>> Urs
>>
>> On 12/09/2010 09:20 AM, Miklos Maroti wrote:
>>> Hi Guys!
>>>
>>> On the RF230 we perform an instantaneous RSSI based CCA check, but you
>>> can enable the hardware CCA which takes around 16 microseconds.
>>>
>>> Miklos
>>>
>>> On Thu, Dec 9, 2010 at 7:55 AM, Urs Hunkeler<urs.hunke...@epfl.ch>
>>> wrote:
>>>> From my tests on a TelosB (CC2420 radio) it varies linearly between
>>>> 1ms
>>>> and 10ms (when the channel is free, in principle the radio is already
>>>> in
>>>> receive mode while the message is being copied to the radio's memory,
>>>> but I don't think this is used as the CCA). The duration on an Iris
>>>> mote
>>>> (RF230 radio) is shorter, but I haven't measured the details.
>>>>
>>>> The duration of the CCA is definitely configured by TinyOS, as I
>>>> managed
>>>> to shorten it. You might have to dig into the lower levels of the
>>>> radio
>>>> interface.
>>>>
>>>> Cheers,
>>>> Urs
>>>>
>>>>
>>>>
>>>> On 12/08/2010 10:46 PM, TheMrOrange wrote:
>>>>> from my tests cc2420 is in rx mode for 8msec if the channel is empty
>>>>>
>>>>> Davide
>>>>>
>>>>> On 08/dic/10, at 20:53, Eric Decker wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> On Wed, Dec 8, 2010 at 12:27 PM, wasif masood<rwmas...@gmail.com
>>>>>> <mailto:rwmas...@gmail.com>> wrote:
>>>>>>
>>>>>>
>>>>>> Hi all,
>>>>>>
>>>>>> can anyone tell me how long does a sender sense(in msec) the
>>>>>> channel if I use CCA enabled transmission? is this mention
>>>>>> anywhere?
>>>>>>
>>>>>>
>>>>>> I think that is buried down in the radio h/w but I am not sure. You
>>>>>> might want to take a look at the h/w specs for the radio you are
>>>>>> using.
>>>>>>
>>>>>> eric
>> _______________________________________________
>> Tinyos-help mailing list
>> Tinyos-help@millennium.berkeley.edu
>> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
>>
>
> _______________________________________________
> Tinyos-help mailing list
> Tinyos-help@millennium.berkeley.edu
> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
>
> --
> This message has been scanned for viruses and
> dangerous content by MailScanner, and is
> believed to be clean.
>
>
--Deeksha
--Deeksha
--
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.
_______________________________________________
Tinyos-help mailing list
Tinyos-help@millennium.berkeley.edu
https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
