Testing Wireless Throughput with Different Environment

[Arie --]

Hello,

Please help me to understand about the effect of interference to the wireless throughput.

By wired, I have 100Mbps download and upload speed. The backbone link connect to Cisco Switch 3850 and down to the Cisco 2960. The Access Point (AP), which is Aironet 3702I, connect to the 2960 switch with Full PoE power (PoE+).

• I enable 2.4GHz and 5.0GHz radio.
• I enable the n and ac rates
• The mandatory rate for 2.4GHz and 5.0GHz are 12 and 24 Mbps
• Rate below 12Mbps are disabled.
• DCA and TPC are enabled.
• CleanAir is enabled.
• The SSID use open authentication with centralized switching.
• The SSID name is #FirstMediaWifi

Scenario 1

I tested on less interference environment and the results are attached.

Scenario 2

I tested on crowded interference environment and the results are attached.

I test the throughput by using Speedtest.net with consistent test server (the nearest and reliable server), either on smartphone or laptop.

From the result, what are the possibilites that caused the throughput decrease on scenario 2?

And what should I do to improve the throughput on scenario 2?

Thank you all.

Regards,

Arie.

[Brett Verney]

Check out this for further reading;

http://wifinigel.blogspot.com.au/2013/03/how-fast-is-my-ipad-on-wifi.html

[Brett Verney · Accepted solution]

Hi Arie,

There are many factors that influence the throughput speeds of a wireless clients.

• Co-Channel Interference (CCI) from other APs
• Adjacent Channel Interference (ACI) from other APs
• Client capabilities (can they support multiple spatial streams, or 40/80mhz channels)
• Airtime utilisation from other clients on the same AP (wireless is essentially half duplex)
• Distance from AP
• Physical Obstructions
• Whether legacy devices (802.11b) are on the network
• Legacy data rates enabled on the WLC
• Number of SSID's being advertised from a single AP
• AP to client ratio

There are many more but this a list off the top of my head. At the end of the day your throughput is determined by your Signal-to-Nose Ratio (SNR). The higher the SNR (high signal, low noise) the more throughput you will get out of a client.

I'd use the 5 GHz network where possible, as there are many more channels available for use. You will be less likely to experience interference from your neighbour's APs.

I'd also be more inclined to use a local speedtest server opposed to speedtest.net. This way you can also rule out having to rely on the ISP. iPerf is a simple client/server command line tool that you can run to test throughput on your LAN. There are Android/iPhone utilities that have iPerf built in as well.

You can also use tools like RX-SOP to effectively shrink the size of your AP cell edge (smaller cell sizes) allow more APs to be added in High Density environments to avoid channel overlap, especially on the 2.4 GHz band.

I know this may not have been the answer you were looking for, but should give you a place to start. ~70Mbps is roughly the throughput limit for devices with a single spatial stream and 40mhz support so you could be at your client limits. You'd expect half that if the device only supports 20mhz.

Regards,

Brett Verney