Expected 802.11ac Wireless Throughput

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Hi Team, new customer here .. go easy! :-)

I'm after tips for troubleshooting Wi-Fi performance. I believe I should be seeing better performance from our deployment: V2110 Small and AP3935i-ROW.

The iperf output below is from a Surface Pro 4 (Windows 10), however, I observed the same performance from an HP Folio 9480m (Windows 10) and a MacBook Pro (Mid 2014 model, macOS Sierra). At time of testing there were < 10 clients connected to the AP.
PS C:\Users\user1> iperf3.exe -c melrad01 -n 200m
Connecting to host melrad01, port 5201
[ 4] local 192.168.220.33 port 49899 connected to 192.168.1.77 port 5201
[ ID] Interval Transfer Bandwidth [ 4] 0.00-1.00 sec 9.25 MBytes 77.5 Mbits/sec [ 4] 1.00-2.00 sec 9.50 MBytes 79.8 Mbits/sec [ 4] 2.00-3.00 sec 9.50 MBytes 79.5 Mbits/sec [ 4] 3.00-4.01 sec 8.88 MBytes 74.2 Mbits/sec [ 4] 4.01-5.00 sec 8.38 MBytes 70.5 Mbits/sec [ 4] 5.00-6.01 sec 8.50 MBytes 70.7 Mbits/sec [ 4] 6.01-7.00 sec 8.62 MBytes 72.8 Mbits/sec [ 4] 7.00-8.01 sec 9.38 MBytes 78.1 Mbits/sec [ 4] 8.01-9.00 sec 9.75 MBytes 82.5 Mbits/sec [ 4] 9.00-10.00 sec 9.25 MBytes 77.5 Mbits/sec [ 4] 10.00-11.01 sec 10.1 MBytes 84.2 Mbits/sec [ 4] 11.01-12.00 sec 8.88 MBytes 75.3 Mbits/sec [ 4] 12.00-13.00 sec 9.25 MBytes 77.7 Mbits/sec [ 4] 13.00-14.00 sec 8.25 MBytes 69.1 Mbits/sec [ 4] 14.00-15.01 sec 9.25 MBytes 77.3 Mbits/sec [ 4] 15.01-16.01 sec 9.25 MBytes 77.4 Mbits/sec [ 4] 16.01-17.01 sec 8.88 MBytes 74.4 Mbits/sec [ 4] 17.01-18.01 sec 9.25 MBytes 77.4 Mbits/sec [ 4] 18.01-19.00 sec 9.50 MBytes 80.2 Mbits/sec [ 4] 19.00-20.00 sec 9.00 MBytes 75.6 Mbits/sec [ 4] 20.00-21.00 sec 8.88 MBytes 74.6 Mbits/sec [ 4] 21.00-21.95 sec 8.50 MBytes 75.0 Mbits/sec - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bandwidth [ 4] 0.00-21.95 sec 200 MBytes 76.4 Mbits/sec sender [ 4] 0.00-21.95 sec 200 MBytes 76.4 Mbits/sec receiver
For reference, and to prove no load on the iperf server side, here is the same test from the Surface Pro 4 via Ethernet. Noting Ethernet and AP are connected to the same switch via Cat6 1Gbps cable.
PS C:\Users\user1> iperf3.exe -c melrad01 -n 1g
Connecting to host melrad01, port 5201
[  4] local 192.168.1.89 port 49968 connected to 192.168.1.77 port 5201
[ ID] Interval           Transfer     Bandwidth
[  4]   0.00-1.00   sec   113 MBytes   948 Mbits/sec
[  4]   1.00-2.00   sec   113 MBytes   947 Mbits/sec
[  4]   2.00-3.00   sec   113 MBytes   945 Mbits/sec
[  4]   3.00-4.00   sec   112 MBytes   941 Mbits/sec
[  4]   4.00-5.00   sec   110 MBytes   919 Mbits/sec
[  4]   5.00-6.00   sec   104 MBytes   869 Mbits/sec
[  4]   6.00-7.00   sec   112 MBytes   939 Mbits/sec
[  4]   7.00-8.00   sec   113 MBytes   945 Mbits/sec
[  4]   8.00-9.00   sec   111 MBytes   933 Mbits/sec
[  4]   9.00-9.21   sec  24.2 MBytes   948 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth
[  4]   0.00-9.21   sec  1.00 GBytes   932 Mbits/sec                  sender
[  4]   0.00-9.21   sec  1024 MBytes   932 Mbits/sec                  receiver
Below are my Wi-Fi settings during testing.
PS C:\Users\user1> netsh wlan sh in

There is 1 interface on the system:
    Name                   : Wi-Fi
    Description            : Marvell AVASTAR Wireless-AC Network Controller
    GUID                   : 0648234d-869f-40aa-a19c-17f05462fe12
    Physical address       : bc:83:85:0e:d5:b6
    State                  : connected
    SSID                   : [removed]
    BSSID                  : [removed]
    Network type           : Infrastructure
    Radio type             : 802.11ac
    Authentication         : WPA2-Enterprise
    Cipher                 : CCMP
    Connection mode        : Profile
    Channel                : 157
    Receive rate (Mbps)    : 360
    Transmit rate (Mbps)   : 360
    Signal                 : 90%
    Profile                : [removed]
I have read this article which indicates "If a WiFi client gets between 50-60% of the data rate shown that's pretty universally considered a good solid connection and transfer speed". The lowest 802.11ac data rate quoted in the article is "450 Megabits per second = 56.25 Megabytes per second".

I'm achieving nowhere near that.

One thing I have noticed is that the APs are operating in 802.11af mode and not 802.11at. I have Low Power Override enabled. My understanding (from various articles) is that the AP is operating at a reduced capacity. The PoE+ switch port the AP is connected to indicates it has allocated 17W of power and actual power is 6.6W. Not sure if this effects anything but thought I'd call it out.

The 3935i is capable of 1.7Gbps throughput and the Surface Pro 4 is capable of 800Mpbs (approx). Yes, I realise these are theoretical, but average transfer over 802.11ac in the above test was 75Mbps.

Any assistance would be great. Thanks!
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Dennis

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Posted 9 months ago

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Andre Brits Kannemeyer

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Hi


Are you using 20, 40 or 80 Mhz channels??

Also with 802.3af the 3935i goes from 4x4 mimo ap to a 2x2 mimo ap....
(Edited)
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Dennis

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So just to clarify, a drop from 4x4 MIMO to 2x2 MIMO = a performance hit consistent with the iperf results? What then is Low Power Mode Override?

Channel Width configured to 40Mhz.

(Edited)
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Kurtman, Emre, Employee

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Hi Dennis,

iperf paramters plays a significant role on the throughput rates you get.

Especially -w (window size) and -P (parallel stream number) make the most significant changes. You can try between 800k (800 kilobyte) and 1M (1 megabyte) for -w and 1 to 10 for -P.

For AP settings, AMPDU and ADDBA should be enabled too.

By the way, if you leave TxBF enabled with MU-MIMO, then your MCS index will drop and that will affect your connection rate. So if you do not want to test MU-MIMO, yan can leave TxBF off.
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Sam, Employee

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Hi Dennis,

Unless the client is capable of 4x4 MIMO you’ll not see the true benefits. Although Mu-MIMO with 4 spatial streams could benefit you here since an AP would be able to communicate with up to 4 devices simultaneously, however as Kurtman emphasized if you do not want to test MU-MIMO leave TxBF off. 

Low power override will try to force the AP to use 802.3at (if it’s available) by sending a power status element with ‘power mode’ set to 0. The AP3935i data sheet documents a max power draw of 19w, I would advise reviewing the controller logs to see if there are any message representing the log below:

Critical    17 sec in cycle 1: AP powered by AF instead of AT PS, entering low power mode(2x2 R1,2x2 R2)

It could be a PoE budget issue, or depending on the switch, additional configuration could be required. See additional notes in the following article: https://gtacknowledge.extremenetworks.com/articles/Q_A/What-PoE-standards-are-needed-to-power-up-the-AP39xx

The Wi-Fi settings you have shown for your testing are indicative of a GI of 800ns, if you reduced that to a SGI of 400ns (providing the environment allows for it) you could see an increase to 400mbps on receive and transmit rates at 256-QAM 5/6.

There are also a few additional settings in this article that would be beneficial to double check on your network: https://gtacknowledge.extremenetworks.com/articles/How_To/How-do-I-measure-the-wireless-performance-of-a-client-on-an-access-point-and-what-factors-might-impact-performance

Additionally, was there a survey completed pre-deployment and then a validation survey post deployment to set an expectation, and prove, what would be achievable in your environment? 

One last consideration is you mentioned that there were additional clients on the AP, what applications were they using? Have you run the test with a single client on the AP? 

- Sam
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Andre Brits Kannemeyer

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Hi Dennis

Another note is to look at the client, even though the client supports 802.11ac it does not mean that it supports four spatial streams.
Your client could have a single antenna.....
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Andre Brits Kannemeyer

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Microsoft surface Pro 4:

Wi-Fi CERTIFIEDTM ac
2 Spatial Streams 5 GHz
Rx MCS 8-9 (256-QAM)
Rx STBC 2x1
Rx A-MPDU of A-MSDU
Low Density Parity Check coding
Tx SU beamformee
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Dennis

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Thanks for the responses. I've got some reading and further testing to do. In repsonse to the various questions:

- AMPDU and ADDBA is enabled
- TxBF is OFF
- Can't see this "Critical    17 sec in cycle 1: AP powered by AF instead of AT PS, entering low power mode(2x2 R1,2x2 R2)" in the logs (yet)
- GI set to SHORT
- Re-tested with 3 clients connected with same result but will try with 1 as soon as convenient
- Site survey was done and recommendations made but no concrete figures were presented
- From site survery report can see that the AP has no overlap, 3 co-channel and 9 adjacent

I think I'll focus on PoE requirements and take it from there.
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Dennis

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From the AP / controller Is there some way to determine the wattage an AP is drawing or confirm why it has not negotiated 802.11at rather than 802.11af?

I have configured my switch port to 30W but finding it's not drawing anywhere near that.
  PoE   | Power  Power    Alloc Alloc Actual Configured  Detection   Power
  Port  | Enable Priority By    Power Power  Type        Status      Class
  ----- + ------ -------- ----- ----- ------ ----------- ----------- -----
  1     | Yes    low      value 30 W  6.2 W              Delivering  4
And this ...
# sh lldp info remote-device 1
 LLDP Remote Device Information Detail
  Local Port   : 1
  ChassisType  : mac-address
  ChassisId    : d8 84 66 79 21 cb
  PortType     : inte...
  PortId       : eth0
  SysName      : CA-L4-EAST
  System Descr :
  PortDescr    :
  System Capabilities Supported  :
  System Capabilities Enabled    :
  Remote Management Address
  MED Information Detail
    EndpointClass          :Class1
    Poe Device Type        :PD
    Power Requested        :25.0 W
    Power Source           :Unknown
    Power Priority         :Unknown
I have restarted the AP, too. Thanks.
(Edited)
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Sam, Employee

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Hi Dennis,

The AP will draw power based on client throughput and load. So now you know it has access to the required power from the switch i'd try loading that AP up with clients and see what the results are on the power draw. 

- Sam 
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Sam, Employee

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In addition, to confirm on the controller: 
AF vs AT; to confirm AP is not in low power, you can view from the following: 

  • Controller>Home – Health/APs in low power mode. 
  • Controller>Reports>APs > AP Inventory > “Mode” is one of the cells of table displayed in report.
Hope this helps. 

- Sam 
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Dennis

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OK thanks Sam. Will give it a go when I'm in the office tomorrow.

Noting that I'm still seeing AF negotiation on LAN1 of the AP (forgot I could check this):
Normal
PS:Off
Port1:AF
Port2:Off
Config Override
LAN1:1G/FDX
LAN2:N/A
(Edited)
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Sam, Employee

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What switch is it that you are using? Also what FW versions are you running on the wireless and switch? 

Is LLDP enabled on the AP? (AP > [Select AP] > Configure > Advanced).

If you get no joy tomorrow when the AP is loaded with clients, i think it'll be time to get a GTAC case open.

Best regards,
Sam 
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Dennis

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HP ProCurve 2910al running firmware W.14.49, which I suspect is well behind current release. Wireless firmware is 10.31.01.0048.

I emailed our Exteme Networks rep today who will kindly lend me a PoE injector to test with.
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Dennis

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Hi Team, just an update to this. One of those cases where I forgot to check the obvious :-| I connected an Ethernet client to the same swtich port as the AP and experienced the same throughput results. It turns out the issue is completely wireless unrelated. It's an issue with inter-VLAN routing which I am investigating with the router vendor.

Thanks for all the suggestions!