Access point and client

The accompanying slides can be downloaded here: TutorialPart2_wilabt.pptx

In this tutorial, we will show you how to set up one wireless access point and connect with 1 client. The access point will start an iPerf server instance, after which we will run an iPerf client instance on the second node. By using the correct IP addresses, we make sure that the iPerf traffic stream is routed over the wireless interfaces.

The following steps should guide you through the entire process:

Reserve 2 wireless nodes using jFed

Your tutor will give everyone the names of 2 nodes you can choose in jFed by right clicking the node. Name them: ap and client in jFed.

Configure the access point

Before running the experiment, we will use the shell script option in the RSpec to install hostapd. Go to the Raw RSpec view and add the following in the node part of the ap (first line is already there):

<sliver_type name="raw-pc"/>
<services>
     <execute shell="sh" command="sudo apt-get update ; sudo apt-get install hostapd"/>
</services>

Note

It should be valid XML, so if you want to use &&, then escape it.

See http://fed4fire-testbeds.ilabt.iminds.be/ilabt-documentation/urnsrspecs.html#install-software-when-provisioning-and-run-a-script-after-provisioning for more examples.

Configuration of Access Point

Become root:

sudo su

Create a config file for the hostapd program:

nano /root/hostapd.conf

Add the following content to the config file (choose a unique name foor ssid, choose other channel, lines should be left aligned):

interface=wlan0
driver=nl80211
country_code=BE
ssid=iperfAP
hw_mode=g
channel=6

Start hostapd. The above config will setup an AP on wlan0 using 802.11g, channel 6, with SSID iperfAP:

hostapd /root/hostapd.conf

Open a second ssh terminal and give an IP address to the wlan0 interface so we can test the connection to the clients (in the next steps):

ifconfig wlan0 192.168.1.1/24

Configure the client

Become root:

sudo su

Put the wireless interface into managed mode and specify the SSID so it knows to which AP it should connect

iwconfig wlan0 mode managed
iwconfig wlan0 essid iperfAP

Specify an IP address and bring up the interface:

ifconfig wlan0 192.168.1.10/24 up

Check if you can ping the AP:

ping 192.168.1.1

iPerf measurement

Start an iPerf server instance (UDP in this case) on the AP:

iperf -s -u -i 1

Configure the iPerf client:

iperf -u -c 192.168.1.1 -b 20M -i 1

By tweaking the transmit power (values of 0 to 20dBm) of the access point, you should be able to see a difference in throughput of the iPerf stream:

iwconfig wlan0 txpower <0-20>

Note that each antenna at the w-iLab.t is equipped with a 10dB attenuator (so 20dB attenuation per link).