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--- exploring_lora [2018/09/23 15:03] – [6. Performance Evaluation] samer
+++ exploring_lora [2018/09/27 13:41] – [4.2. Packet Error Rate] samer
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   * How LoRa is compatible with LPWAN requirements and constraints?
 </WRAP>
-===== -. Hardware Platform =====
+===== -. Setting the Lab =====
+==== -. Hardware Platform ====
 In order to design and implement experiments with LoRa, you will use the following devices:
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   * Give an estimated cost of your platform.
 </WRAP>
-===== -. Software Tools =====
+==== -. Software Tools ====
 Download the following software on your PC:
   * RadioHead: The Packet Radio library for embedded microprocessors can be downloaded from [[http://www.airspayce.com/mikem/arduino/RadioHead/]] or from this [[http://www.airspayce.com/mikem/arduino/RadioHead/RadioHead-1.86.zip|direct link]].
-  * Arduino IDE: Specific OS versions can be downloaded from [[https://www.arduino.cc/en/Main/Software]] or easier for the course Moodle.
+  * Arduino IDE: Specific OS versions can be downloaded from [[https://www.arduino.cc/en/Main/Software]].
 Unzip the RadioHead library and copy it to your sketchbook library folder as detailed in [[https://www.arduino.cc/en/Guide/Libraries]].
-===== -. Installation =====
+<WRAP center round tip 75%>
+Note well the location of the library folder on your computer. In the following, you will be required to modify source files located in this folder.
+</WRAP>
+==== -. Installation ====
 Start by plugging the Dragino shields on the Arduino devices and mounting the antennas as shown in Fig. 1.
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 For Arduino Mega 2560, additional drivers for Microsoft Windows can be installed from [[http://wch.cn/download/CH341SER_ZIP.html]].
 </WRAP>
-===== -. Running Basic Sketches =====
-Start by setting the central frequency of the LoRa modules. For this, open the ''RH_RF95.cpp'' file locate in the ''RadioHead'' folder and change the frequency to 868.10 (Group 1), 868.30 (Group 2), and 868.50 MHz (Group 3).
+===== -. Theoretical Study =====
+In this section, you will perform a theoretical assessment of the performance of LoRa modulation. You will later compare this theoretical results to the experimental ones as in a typical scientific study.
+<WRAP left round help 100%>
+  * What is the relation between processing gain and spreading factor in LoRa modulation? Explain.
+  * How does the spreading factor impact the coverage of a LoRa transmitter?
+  * For each of the three possible configurations of your LoRa module, what is the transmission bit rate? Explain your computation.
+  * Compute the receiver sensitivity, assuming the following parameters: channel bandwidth = 125 kHz, spreading factor = 7, coding rate = 4/5, bit error rate (BER) target = 10<sup>-4</sup>, and receiver noise figure = 6 dB. Refer to this {{ :1705.05899.pdf | article}} to determine the mapping between the BER and the SNR.
+  * Compare the computed sensitivity to that provided by the {{ :an1200.22.pdf |Semtech Application Note AN1200.22}} for the same parameters.
+</WRAP>
+===== -. Configuring and Running the Lab =====
+==== -. Modifying the Radio Parameters ====
+Start by setting the central frequency of the LoRa modules. For this, open the ''RH_RF95.cpp'' file locate in the ''RadioHead'' folder and change the frequency according to the following table:
+^  Group Number  ^   Frequency     ^
+|       1        |      866.7      |
+|       2        |      866.9      |
+|       3        |      867.1      |
+|       4        |      867.3      |
+|       5        |      867.5      |
+|       6        |      867.7      |
+|       7        |      867.9      |
+|       8        |      868.1      |
+|       9        |      868.3      |
+|       10       |      868.5      |
+|       11       |      868.7      |
+|       12       |      868.9      |
 <file cpp RH_RF95.cpp>
 setFrequency(868.X);
 </file>
-Download the {{ :example-lora-sketch.zip | basic sketches}} that implement a reliable LoRa communication between the two modules. Open the sketches with Arduino IDE, compile and upload on the two arduino modules, respectively. On the serial interfaces, you should obtain similar results as in Fig. 2 and Fig. 3. The client sends a short message and waits for an acknowledgement message from the server. Both modules output the RSSI (received power in dBm) for each received message.
-[{{ :client-iotlab1.png?direct&600 ||Figure 2. Client serial monitor}}]
-[{{ :server-iotlab1.png?direct&600 ||Figure 3. Server serial monitor}}]
-===== -. Modifying the Radio Parameters =====
 The typical configuration for LoRa modules consists of 125 kHz sub-channels, a coding rate of 4/5, and a spreading factor equal to 7. You can modify the radio parameters by selecting one of the three available configurations:
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 setModemConfig(Bw125Cr45Sf128);
 </file>
+==== -. Running Basic Sketches ====
-<WRAP left round help 100%>
+Download the {{ :example-lora-sketch.zip | basic sketches}} that implement a reliable LoRa communication between the two modules. Open the sketches with Arduino IDE, compile and upload on the two arduino modules, respectively. On the serial interfaces, you should obtain similar results as in Fig. 2 and Fig. 3. The client sends a short message and waits for an acknowledgement message from the server. Both modules output the RSSI (received power in dBm) for each received message.
-  * What is the relation between processing gain and spreading factor in LoRa modulation? Explain.
-  * How does the spreading factor impact the coverage of a LoRa transmitter?
+[{{ :client-iotlab1.png?direct&600 ||Figure 2. Client serial monitor}}]
-  * For each of the three possible configurations of your LoRa module, what is the transmission bit rate? Explain your computation.
+[{{ :server-iotlab1.png?direct&600 ||Figure 3. Server serial monitor}}]
-  * Compute the receiver sensitivity, assuming the following parameters: channel bandwidth = 125 kHz, spreading factor = 7, coding rate = 4/5, bit error rate (BER) target = 10<sup>-4</sup>, and receiver noise figure = 6 dB. Refer to this {{ :1705.05899.pdf | article}} to determine the mapping between the BER and the SNR.
-  * Compare the computed sensitivity to that provided by the {{ :an1200.22.pdf |Semtech Application Note AN1200.22}} for the same parameters.
-</WRAP>
 In the remainder of this lab, you will conduct measurements to validate the obtained theoretical receiver sensitivity.
 ===== -. Performance Evaluation =====
 In the following, you will design and implement a set of scenarios that enable to evaluate the performance of the LoRa modulation. As you will deal with scientific assessment, you are required to use scientific tools to show the results. You have the choice between [[http://www.gnuplot.info | gnuplot]], [[https://matplotlib.org/index.html#|matplotlib]] with Python, and MATLAB. Take some time to become familiar with one of these software as you will be required to use them in different occasions of your academic programme.
-==== -. Round Trip Time ====
-In this section, you will measure the Round Trip Time of LoRa communication under the three different radio configurations. For this, you can start by implementing a function on the client that measures the time between the message sending and the reception of the acknowledge from the server. For example, you can use the [[https://www.arduino.cc/en/Reference/Micros| micros()]] function available in the arduino libraries.
+==== -. Time on Air ====
+In this section, you will measure the Time on Air (ToA) under the three different radio configurations and for different message sizes. For this, you can start by implementing a function on the client that measures the time necessary for sending a message. For example, you can use the [[https://www.arduino.cc/en/Reference/Micros| micros()]] function available in the arduino libraries.
 <WRAP center round help 100%>
-  * Draw a box plot of the RTT under the three different radio configurations.
+  * Draw a box plot of the ToA under the three different radio configurations and for three different message sizes.
   * Analyze the obtained results and compare with the theoretical computations.
 </WRAP>
-==== -. Packet Error Rate ====
+==== -. Packet Delivery Ratio ====
 In this section, you will measure the Packet Error Rate (PER) under the three different radio configurations and for different transmission periods. For this, you can start by implementing a function on the client that measures the ratio of successfully delivered packets.
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   * What type of mathematical models enables to theoretically compute the PER?
 </WRAP>
 ==== -. Coverage ====
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 In order to compute distances in your experiment, you can get the GPS coordinates as recorded by your smartphone using an application such as [[https://play.google.com/store/apps/details?id=com.flashlight.lite.gps.logger&hl=en|Ultra GPS Logger]]. You can export the time-location correspondence in a CSV format from this application. As for the time-RSSI correspondence, you can use a {{ :log-windows.py.zip |logger file}} on your laptop. Finally, the time matching enables you to obtain the RSSI for each GPS location, hence for different distances.
+===== -. Coverage Challenge =====
 ===== -. Grading =====
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 ^ Design experiments       |                      |                    |                    |                    |
 ^ Analyse results          |                      |                    |                    |                    |