Wireless – How to test Wi-Fi Multimedia (WMM) QoS management with LANforge

qostestingthroughputwireless

I would like to test the Wi-Fi Multimedia (WMM) feature of an access point AP.

How can I test it using Candela Technologies LANforge-WiFIRE WiFi traffic generator?

Some thoughts after reading the WMM whitepaper:

  1. Assuming the capacity of the wireless link is 60 Mbps, set up a virtual station STA-1 with a video UDP uplink stream of 30 Mbps.

  2. Set up another virtual station STA-2 with a background TCP uplink stream of 30 Mbps.

  3. Set up another STA-3 with a background TCP uplink stream of 30 Mbps, starting after 10 seconds.

When WMM is enabled, there should be a drastic drop in throughput for the first background stream while there should be no change for the video stream. When WMM is disabled, the video stream should suffer a loss in rate.

What should be the best procedure?

Best Answer

This is the record of the testing done on the AP using the LANforge.

Inside the anechoic chamber, the LANforge (eth1) is connected to the AP under test via a LAN cable.

I set up 4 virtual stations in the LANforge, with the same SSID as the AP. This results in a loop that allows the LANforge to measure the throughputs of the various streams. The stations are named:

STA-1-BK (background) STA-2-BE (best effort) STA-3-VI (video) STA-4-VO (voice)

I configure 1 uplink stream per station. Each stream is set as 10 Mbps UDP. Notice that the streams are in an increasing order of priority.

Tests are conducted when WMM is disabled, and the same tests are conducted when WMM is enabled.

The test procedure is as follows:

STA-1 starts transmitting. Then STA-i starts transmitting at time (i-1)*30 s.

I found that the video and voice streams are not able to achieve the desired 10 Mbps, when WMM is disabled.

Next, WMM is enabled.

When WMM is enabled, the QoS priority of the data streams are taken into account. When the video or voice streams are turned on, they maintain the constant desired throughput, while the background and best effort streams are starved of throughput.

Also, when WMM is enabled, only the background and best effort streams shows large latency. The video and voice streams have very little latency.

Therefore, it can be seen that the WMM feature is working in AP under test.

Reference: Wi-Fi Multimedia (WMM) www.uniroma2.it/didattica/TPI2/deposito/wmm.pdf

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