On Fri, Sep 16, 2011 at 06:58:46AM -0700, George Nychis wrote:
> Hi all,
>
> I was wondering what the status of the clear channel assessment is on the
> RedBee. I am noticing that 802.11 slaughters reception, although I think the
> 802.11 signal should be strong enough to carrier sense.
>
> I am wondering if it is: 1) 802.11 not backing off to the zigbee
> transmissions,
> or 2) zigbee not backing off to 802.11.
>
> I understand there is a fairness issue here, and I can imagine (1) not
> occurring because of ZigBee only transmitting in a subset of the frequency
> space that 802.11 is sensing. But, I was wondering more of what the status of
> (2) is.
>
> I looked through some of the code and found the maca code and mentions of CCA
> flags, but the "TODO" says CCA.
I have CCA basically sorted out, but what exacly to do with it is an
open question for a lot of different implementations.
If one wished to implement one of the CSMA modes specified in
802.15.4, for instance, I have enough knowledge about how the CCA
hardware works to get them through that development.
I'm currently working on fixing ContikiMAC for the mc1322x, which also
requires a CCA check. That code is here:
http://git.devl.org/?p=malvira/contiki-2.x.git;a=shortlog;h=refs/heads/contikimac-oldcfg
In cpu/mc1322x/lib/maca.c and cpu/mc1322x/contiki-maca.c you'll find
CCA code.
-Mar.
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