ORBIT-USER: questions about atheros card

[Kishore Ramachandran]

Hi Xiangpeng:

(1) When I tried to set channel on atheros cards with master mode, it
> always give me error:
> Error for wireless request "Set Mode" (8B06) :
>     SET failed on device ath0 ; Invalid argument.
>
>   How to set a pair of master/managed nodes on a particular channel,
> as they have better association than ad-hoc mode?


I suggest using nodehandler for imaging and shell scripts for node
configuration and application control. Also in infrastructure mode, you only
set the channel of the AP and regular "iwconfig" should work. There may be
sequencing issues such as setting the channel before the interface is
brought up or IP address assignment is performed. In these cases, I suggest
using the latest version of madwifi since the driver writers have fixed a
number of issues in the latest versions. These are available in our latest
images, baseline-2.0 and baseline-2.1.

(2) How is the ad-hoc mode status for atheros card now? I managed to
> set up a couple of atheros nodes using ad-hoc mode, and finally their
> essid, channel, cell id are all same. But some nodes still can not
> communicate with others, e.g., node18-18 can not communicate with
> node10-11, but was able to communicate with other nodes.


I have used single-hop ad-hoc mode and it works quite well for me with
Chris' ad-hoc fix. I do not see any reason why this fix should not work for
a multi-hop setup (with multiple ESSIDs for the different hops). I suggest
you patch the driver with this fix or find an image with this fix.

(3) Maybe Kishore can help me with this question: how long is the
> latency when I dynamically set up a channel for a pair of atheros
> nodes before they are able to communicate? I used system calls
> (iwconfig) in my program (I know it's a bad method) to change runtime
> channels but atheros nodes can not communicate in this way (before it
> worked great for intel cards). Is there a faster way to change atheros
> card channels runtime, e.g., some ioctls for the old aironet driver?


Channel switching latency reported for Atheros 5212 is 5ms - I have never
measured this myself explicitly. If iwconfig does not work, I would suggest
modifying the driver to use a configfs-based solution (similar to procfs).
All ioctl-based techniques will have the same delay that current
iwconfig-based approaches will have. Also, how long does it take for the
atheros nodes to start communicating after the channel switch using
iwconfig? I am surprised they do not communicate at all - are you just
changing channels on the AP? If you change channels on the client as well,
from past experience, the cards will not communicate.

regards,
Kishore
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