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WiFiMon Hardware Probes (WHP) are used for performance measurements in a WiFi network from dedicated small form factor devices which are installed in fixed points. WiFiMon tested its operation and recommends the use of Raspberry Pi’s v3 Model B+ or v4. 

WHP configuration

WiFiMon Hardware Probe will work in the following configuration:

WiFiMon Raspberry Pi image given above is a custom version of Raspbian Stretch with desktop, with the default Raspberry Pi credentials (user: pi, password: raspberry).

We advise the user to secure Raspberry Pi by changing the default password.

Setting up the WHP

Step 1: Write the image to the micro SD card

Follow the instructions at the official Raspberry Pi site. Skip the "Download the image" step and use the WiFiMon Raspberry Pi operating system image instead.

Step 2: Start the Raspberry Pi

Follow the simple steps below:

  • Insert the microSD in the Raspberry Pi
  • Plug the USB keyboard into one of the USB ports (or USB wireless adapter for keyboard and mouse)
  • Plug the USB mouse into one of the USB ports
  • Connect the monitor cable to the Pi's HDMI port
  • Plug the power supply into a socket and connect it to the micro USB power port

You should see a red light on the Raspberry Pi and raspberries on the monitor. The WiFiMon Hardware Probe will boot up into a graphical desktop.

Step 3: Configure the RPi

Secure your Raspberry Pi by changing the default password. Optionally, you may enable SSH to access the command line of a Raspberry Pi remotely or setup remote desktop. Next, you have to connect to the wireless network you want to measure.

The WiFiMon Hardware Probe (WHP) performs performance tests towards the WiFiMon Test Server (WTS) in an automated manner, thus simulating end users from a fixed location in the monitored WiFi network. WHP uses crontab to schedule the tests. To do that, open the terminal (as user "pi") and enter the command: crontab -e. You will have to pick the text editor. Then scroll to the bottom of the file and add the following code block (which you will modify as explained below): 

19,39,59 * * * * export DISPLAY=:0 && firefox --new-window https://www.google.com >/dev/null 2>&1

00,05,10,15,20,25,30,35,40,45,50,55 * * * * export DISPLAY=:0 && firefox --new-tab URL_TO_nettest.html >/dev/null 2>&1

01,06,11,16,21,26,31,36,41,46,51,56 * * * * export DISPLAY=:0 && firefox --new-tab URL_TO_speedworker.html >/dev/null 2>&1

02,07,12,17,22,27,32,37,42,47,52,57 * * * * export DISPLAY=:0 && firefox --new-tab URL_TO_boomerang.html >/dev/null 2>&1

03,08,13,18,23,28,33,38,43,48,53,58 /home/pi/wireless.py >> ~/cron.log 2>&1

18,38,58 * * * * scripts/kill-firefox.sh >/dev/null 2>&1

10 0 * * 0 scripts/pi-reboot.sh >/dev/null 2>&1

You have to modify the following parts of the crontab in lines 2-4:

  • URL_TO_nettest
  • URL_TO_speedworker
  • URL_TO_boomerang

You should put the URL or IP address of the WTS in which the NetTest, speedtest and boomerang JS scripts are injected. Details about the configuration of the WiFiMon testtools are included in the WiFiMon Test Server (WTS) installation documentation. Following the assumptions/notations of the WTS guide, example URLs for NetTest, speedtest and boomerang respectively are (i) https://WTS_FQDN/wifimon/measurements/nettest.html, (ii) https://WTS_FQDN/wifimon/measurements/speedworker.html and (iii) https://WTS_FQDN/wifimon/measurements/boomerang.html.

Line 5 of the crontab is related to the streaming of wireless network interface metrics to the WiFiMon Analysis Server (WAS). Optionally, the intervals of the WHP measurements could be altered by appropriately configuring the crontab so that measurement are more or less frequent. The configuration of the following code block considers 5-minute intervals for each test tool.

Step 4: Streaming Wireless Network Interface Metrics to the WiFiMon Analysis Server (WAS)

In /home/pi, you will find the Python script wireless.py. The contents of the script are the following:

wireless.py
#!/usr/bin/python

import subprocess
import datetime
import requests
from requests.packages.urllib3.exceptions import InsecureRequestWarning
requests.packages.urllib3.disable_warnings(InsecureRequestWarning)

def return_command_output(command):
    proc = subprocess.Popen(command, stdout = subprocess.PIPE, shell = True)
    (out, err) = proc.communicate()
    out_without_carriage_return = out.rstrip('\n')
    return out_without_carriage_return

def parse_iwconfig():
    command1 = "sudo iwconfig wlan0 | grep \"Link Quality\""
    command1_output = return_command_output(command1)
    command1_output = ' '.join(command1_output.split())
    command1_parsed = command1_output.split(" ")
    link_quality = command1_parsed[1].split("=")[1]
    link_quality = link_quality.split("/")[0]
    signal_level = command1_parsed[3].split("=")[1]
    command2 = "sudo iwconfig wlan0 | grep \"Tx-Power\""
    command2_output = return_command_output(command2)
    command2_output = ' '.join(command2_output.split())
    command2_parsed = command2_output.split(" ")
    bit_rate = command2_parsed[1].split("=")[1]
    tx_power = command2_parsed[3].split("=")[1]

    timestamp = int(datetime.datetime.now().strftime("%s")) * 1000
    probeNo = "WHP_NUMBER"

    headers = {'content-type':"application/json"}
    data = "{\"timestamp\":" + str(timestamp) + ", \"bitRate\":" + bit_rate + ", \"txPower\":" + tx_power + ", \"linkQuality\":" + link_quality + ", \"signalLevel\":" + signal_level + ", \"probeNo\":\"" + probeNo + "\"}"
    try:
        session = requests.Session()
        session.verify = False
        session.post(url='https://WAS_FQDN:8443/wifimon/probes/', data=data, headers=headers, timeout=15)
    except:
        pass
    return None

if __name__ == "__main__":
    parse_iwconfig()

User has to edit lines 31 and 38 according to their setup. In line 31, "WHP_NUMBER" should match the number assigned to the testtools of the particular WiFiMon Hardware Probe (WHP), e.g. for the WHP assigned the number 1, the value should be "1". Assigning numbers to WHPs is possible by appropriately setting the testtool attribute included in the websites monitored by them. More information related to assigning number to WHPs is available in the WiFiMon Test Server installation guide. In line 38, "WAS_FQDN" should match the FQDN of the WiFiMon Analysis Server (WAS) responsible for processing the wireless performance metrics of the WHP. The above code block assumes that the WAS uses the WiFiMon Secure Agent. In case of using the WiFiMon Non-Secure Agent, the URL of line 38 should be modified; instead of "https", the WiFiMon Non-Secure Agent requires "http" and the port on which the WAS listens is "9000" instead of "8443".

That's all! At this point you may (optionally) unplug the keyboard, the mouse and the monitor and let the WHP measure the performance of your wireless network!

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