hai...
IEEE-802.15.4 devices that are there in the market right now are softmac devices
ex: cc2420,cc2520. So it can only detect whether the channel is free or not. For
example in case of cc2520 ,the h/w is providing us the one GPIO pin which is
CCA. It will be high when the channel is free. If the channel is busy (GPIO_CCA
= 0), generating the backoff and resending the packet is not in the h/w
(cc2520) provided the channel is free. So we need to take care of generating the
backoff and resending the packet if the channel is free from the
microcontroller side.
For this to be implemented there are two approaches that i thought of,,,
1. This logic can be at the mac level in kernel (mac802154). We can export that
symbol....
2. Logic can be at the driver code in the ieee802154_ops-> (*tx) : means in the
transmission function(by checking GPIO_CCA in case of cc2520)
If i am wrong please correct me....
Regards,
Bhadram
On January 23, 2014 at 4:15 PM Dmitry Eremin-Solenikov <dbarysh...@gmail.com>
wrote:
> Hello,
>
> On Thu, Jan 23, 2014 at 8:04 AM, Varka Bhadram <var...@cdac.in> wrote:
> > hai....
> >
> > Where is the CSMA-CA implementation ? Is it there in H/w (IEEE-802.15.4
> > radio example:cc2520) itself or is it there at the mac802154 in linux ?
>
> CSMA/CA has so strict timing requirements (logical, you check that the
> channel is
> free and then you immediately should start to transfer), that it's
> just unpractical
> and unrealistic to implement any CSMA/CA / CCA handling in the kernel itself.
>
> Either your hardware should implement that for you, or you are out of luck
> and just hope that the channel is clear.
>
> --
> With best wishes
> Dmitry
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