Expected 802.11ac Wireless Throughput

[Dennis]

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 receiverFor 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 receiverBelow 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!

[Andre_Brits_Kan]

Microsoft surface Pro 4:

Wi-Fi CERTIFIED™ 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

[Sam]

https://www.wi-fi.org/product-finder 

[Sam]

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...

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-...

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

[Emre_Kurtman]

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.

[Dennis]

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.