wiki:WiMAX/WiMAX-Tutorial/RTC/00

Version 5 (modified by Fraida Fund, 6 years ago) (diff)

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On-Campus WiMAX

In this experiment, we'll explore what you can do with on-campus WiMAX.

More than a dozen campuses are now participating in GENI WiMAX. While anybody can use GENI WiMAX remotely, if you are on or near a WiMAX campus you can also do interactive, mobile, and live experiments.

Experiment Background

In this experiment, we'll run a WebRTC video chat in which one participant is using a commodity laptop equipped with a USB WiMAX dongle. (The other participant is connected to the Internet over WiFi).

WebRTC is a new and evolving video standard for enabling voice, video, and data communications in the browser - without plugins. A diverse and vibrant ecosystem of applications using WebRTC has grown up and around the standard in the last year.

Instrumenting the Experiment

We're using the oml4js library, a JavaScript library for collecting measurements from a website and storing them using OML. While the video chat is active, measurements from the chat will be continuously streamed to a local OML server on the laptop. After the experiment is over, we'll push the results to iRODS and examine them more closely there.

Experiment Procedure

The experiment procedure is as follows:

  • The first peer visits the URL for the WebRTC app in Google Chrome. A bar at the top of the screen will ask if you are willing to let the browser access your camera; don't click allow until the second peer has joined the chat!
  • The second peer visits the same URL
  • Both peers click "Allow" and should now see video streams from each other's webcams

Post-Experiment

After the experiment, the OML-instrumented peer will send the measurement results to iRODS using the iput command.

Inside iRODS, we'll use the iRODS web browser to visualize the results of our experiment.

Reconfiguring the WiMAX BS

A major advantage of on-campus WiMAX (over using a regular cellular carrier) for experimentation, is that you can reconfigure the WiMAX BS. In this experiment, we'll try using WebRTC with and without link-layer retransmission (ARQ) and observe the effect of ARQ on latency, packet loss, and video rate.

To reconfigure a base station, you need to log on to the testbed console using SSH:

ssh tutor01@witestlab.poly.edu

From there, you can change base station settings using a simple HTTP command. For example, to turn on ARQ:

wget -qO- "http://wimaxrf:5052/wimaxrf/bs/set?arq=1"

Most reconfigurations only take effect after a reboot:

wget -qO- "http://wimaxrf:5052/wimaxrf/bs/restart"

You can see the full list of configurable options:

wget -qO- "http://wimaxrf:5052/wimaxrf/bs/get?all" | xml_pp

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