AR9342: Two odd packets in every beacon interval in 5Ghz

AR9342: Two odd packets in every beacon interval in 5Ghz

[Harshal Chhaya]

Hello,

We have an AR9342-based AP that is sending out two odd packets each
beacon interval. These packets are 1804 bytes in size, are transmitted
at 6.5Mbps and have the dest MAC address the same as the source MAC
address.

The payload of these packets is all zeros.

It does this only in 5Ghz. These packets aren't transmitted in the 2.4Ghz band.

If we set the bandwidth to 40MHz, it sends only one of these packets
between beacons.

Are these some control or mgmt packets that are part of the protocol?
Or is this unexpected behavior?

The AP is running the 3.3.8 kernel and a compat-wireless from Sep 2012
(part of the openwrt image for this chip).

Thanks,
- Harshal

Re: AR9342: Two odd packets in every beacon interval in 5Ghz

[Felix Fietkau]

On 2013-04-05 5:24 PM, Harshal Chhaya wrote:
> Hello,
> 
> We have an AR9342-based AP that is sending out two odd packets each
> beacon interval. These packets are 1804 bytes in size, are transmitted
> at 6.5Mbps and have the dest MAC address the same as the source MAC
> address.
> 
> The payload of these packets is all zeros.
> 
> It does this only in 5Ghz. These packets aren't transmitted in the 2.4Ghz band.
> 
> If we set the bandwidth to 40MHz, it sends only one of these packets
> between beacons.
> 
> Are these some control or mgmt packets that are part of the protocol?
> Or is this unexpected behavior?
> 
> The AP is running the 3.3.8 kernel and a compat-wireless from Sep 2012
> (part of the openwrt image for this chip).
Maybe it's (failing) PA predistortion calibration, which needs to send
training frames to complete.
I'd suggest trying a newer compat-wireless version, this type of
calibration has been disabled there because of various issues (including
hardware damage on some chips).

- Felix

Re: AR9342: Two odd packets in every beacon interval in 5Ghz

[Harshal Chhaya]

On Fri, Apr 5, 2013 at 11:15 AM, Felix Fietkau <nbd@openwrt.org> wrote:
> On 2013-04-05 5:24 PM, Harshal Chhaya wrote:
>> Hello,
>>
>> We have an AR9342-based AP that is sending out two odd packets each
>> beacon interval. These packets are 1804 bytes in size, are transmitted
>> at 6.5Mbps and have the dest MAC address the same as the source MAC
>> address.
...
> Maybe it's (failing) PA predistortion calibration, which needs to send
> training frames to complete.
> I'd suggest trying a newer compat-wireless version, this type of
> calibration has been disabled there because of various issues (including
> hardware damage on some chips).

Felix,

Thanks for that suggestion. I will try a newer compat-wireless and let
you know what happens.

Regards,
- Harshal

Re: AR9342: Two odd packets in every beacon interval in 5Ghz

[Harshal Chhaya]

On Fri, Apr 5, 2013 at 11:32 AM, Harshal Chhaya <harshal@gmail.com> wrote:
> On Fri, Apr 5, 2013 at 11:15 AM, Felix Fietkau <nbd@openwrt.org> wrote:
>> On 2013-04-05 5:24 PM, Harshal Chhaya wrote:
>>> Hello,
>>>
>>> We have an AR9342-based AP that is sending out two odd packets each
>>> beacon interval. These packets are 1804 bytes in size, are transmitted
>>> at 6.5Mbps and have the dest MAC address the same as the source MAC
>>> address.
> ...
>> Maybe it's (failing) PA predistortion calibration, which needs to send
>> training frames to complete.
>> I'd suggest trying a newer compat-wireless version, this type of
>> calibration has been disabled there because of various issues (including
>> hardware damage on some chips).
>
> Felix,
>
> Thanks for that suggestion. I will try a newer compat-wireless and let
> you know what happens.


Felix,

Sorry for the delayed reply (a couple of other problems had to be
fixed first) but a newer compat-wireless indeed fixed the problem. No
more slow, long packets.

Thank you for explaining what those packets were and for the solution.

Thanks,
- Harshal