Objectives
COMP4336/9336 Mobile Data Networking
Lab 3: Experimental study of wireless path loss – line-of-sight (LoS)
1. To observe path loss phenomenon under LoS condition by analysing RSS at different distances
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2. To estimate path loss exponent for indoor and outdoor under LoS
Prerequisites
• Access to two mobile devices, such as a laptop and a mobile phone with WiFi interfaces
• Wireshark (and any additional monitoring software, e.g., Network Monitor for Windows users)
installed in one of the devices, such as in the laptop
• Familiarity with Wireshark, such as completion of Lab 1
• Understanding of the concepts of path loss, such as lecture notes from Week 2
Introduction
Path loss refers to the loss of signal power as it travels through space. Path loss exponent captures how fast the signal power decays with distance. Different environments, such as indoor and outdoor, usually exhibit different path loss. Having a good estimate of path loss for a given environment of interest is crucial in designing a mobile communication system. Commercial mobile network operators use sophisticated instruments to accurately estimate path loss in areas of their deployment. In this lab, you will use simple tools, such as laptops, phones, and WiFi packet capture tools (e.g., Wireshark), to observe the pathloss phenomenon and derive a crude estimate of path loss component for the indoor and outdoor environments that you have access to.
Your Tasks
RSS data capture [2 marks]: Your first task is to capture RSS data at different distances and save them in CSV files for post-processing. To capture RSS data, follow the following 3 steps (repeat the same steps for both indoor and outdoor):
Step 1: Configure your phone as a WiFi hotspot (set SSID to your UNSW ZID) and connect your laptop to it so that you can capture, e.g., using Wireshark, the beacon packets transmitted by the phone.
Step 2: Place the laptop at one corner of the indoor/outdoor area and mark 10 equally distant spots (locations) from it with the 10th spot located at the farthest corner of the area. Make sure that the laptop has LoS with the phone. and adjust the 9 other spots accordingly.
Step 3: For each marked location, capture WiFi packets transmitted by the phone for at least 1 minute and save them in a CSV file. After this step, you should have 10 CSV files (10 for indoor and 10 for outdoor), one for each of the 10 locations. If you are taking the RSS values only from the beacon packets for consistence transmit powers, you should be able to accumulate between 200 to 600 RSS data in 1 minute assuming beacon intervals anywhere between 100ms to 300ms. Please make sure there are at least 200 RSS data in the trace file; you may need to extend the capturing duration to make sure that you have enough data to process.
Path loss exponent estimation [2 marks]: First, plot the raw RSS data against distance in log scale, i.e., in the y-axis plot RSS in dBm and x-axis log10(distance), where distance is in meters. You will find the graph very noisy and difficult to estimate path loss exponent. Next, plot only the average RSS values per location (x-axis still in log-scale). The later should look much clearer. Now fit a straight line to the average RSS values and find the slope of the line using packages such as Excel, Matlab etc. Show the important data about your fit, such as the equation of the straight line, the slope, and the R squared value (0