802.11ac beamforming report makes no sense!

[Uri]

Hi guys,
maybe someone more experienced in reading .pcap files could help me. links at the bottom.
I have a single 802.11ac client (rivet killer 1535) and an AP (Linksys EA8500), and I have used a macbook air 2014 wireless diagnostics tool to sniff the packets from the air.

Just as the spec orders, every 100 ms. the AP sends out a Null Data Packet Announcement (NDPA) and the client sends back a beamforming feedback report.
The problem is that the beamforming report should describe a matrix of size Nr X Nc, but the values of Nr and Nc makes no sense!

Nc = the number of Space-Time-Streams, as it is specified in the NDP. this value should be between 2 and 8.
Nr = Min between the above and the number of antennas at the client.
(see 802.11ac-2013 page 57)

However, the value specified in the beamforming report is Nc=1! And on the other hand, the report includes the avg. SNR for Space-Time Streams [STS1,STS2,STS3..,STSNc] (see 802.11ac-2013 page 58), and there it shows 8 values, indicating Nc=8!

Can anyone shed some light on the matter?

802.11ac-2013 spec, full pcap and pcap with just the NDPA and beamforming reports can be found here:
https://drive.google.com/folderview?id=0B7X38eaciUXGM3ExZG1kRFFpWnM&usp=sharing

Thanks,
Uri

 

[sfx2000]

802.11ac-2013 spec, full pcap and pcap with just the NDPA and beamforming reports can be found here:

Might want to pull down the IEEE specs, as you might get into trouble there...

802.11-2012, if I recall, is available free from the Get IEEE site (they need a registration), but 11ac, if I recall, is still a paid document...

 

[Uri]

Might want to pull down the IEEE specs, as you might get into trouble there...

802.11-2012, if I recall, is available free from the Get IEEE site (they need a registration), but 11ac, if I recall, is still a paid document...

Thanks @sfx2000 , I pulled it down...

 

[sfx2000]

I have used a macbook air 2014 wireless diagnostics tool to sniff the packets from the air.

If you're using the Air to pull down packets - the driver there is still spewing bad captures... over the air it's fine, it's the WCAP's on that task that are borked, and even with 10.11.2, it's still borked..

So I understand why you're asking - probably time to invest in an AirMagnet or similar...

 

[Uri]

If you're using the Air to pull down packets - the driver there is still spewing bad captures... over the air it's fine, it's the WCAP's on that task that are borked, and even with 10.11.2, it's still borked..

So I understand why you're asking - probably time to invest in an AirMagnet or similar...

@sfx2000 aren't you a resourceful guy to have around
Just to clarify, your point is that the Mac's hardware is fine, but the software side is doing a bad job and spits out errors in the result, and buying a dedicated software for that, such as Airmagnet, might solve the problem, even running on a Mac, correct?

 

[sfx2000]

@sfx2000 aren't you a resourceful guy to have around
Just to clarify, your point is that the Mac's hardware is fine, but the software side is doing a bad job and spits out errors in the result, and buying a dedicated software for that, such as Airmagnet, might solve the problem, even running on a Mac, correct?

Talk to Fluke and some of the other players - about your project and what you're doing, and perhaps datashare... getting decent caps on 11ac is a problem...

 

[Uri]

Thanks!