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--- exploring_lora [2021/08/28 09:46] – samer
+++ exploring_lora [2021/10/20 12:52] (current) – [4.2 Collisions and Packet Delivery Ratio] samer
@@ Line 48: / Line 48: @@
 <WRAP center round tip 75%>
-For Arduino Mega 2560, additional drivers for Microsoft Windows 7 or 8 can be installed from [[http://wch.cn/download/CH341SER_ZIP.html]].
+For Arduino Mega 2560, additional drivers for Microsoft Windows can be installed from [[http://wch.cn/download/CH341SER_ZIP.html]].
 For Arduino Duemilanove, additional drivers can be installed from
 [[https://www.ftdichip.com/Drivers/CDM/CDM21228_Setup.zip]]
@@ Line 69: / Line 69: @@
 In the remainder of this lab, you will conduct measurements to validate the obtained theoretical receiver sensitivity.
-===== -. Configuring and Running the Lab =====
+===== - Configuring and Running the Lab =====
 ==== - Modifying the Radio Parameters ====
@@ Line 152: / Line 152: @@
   * Analyze the obtained results and compare with the theoretical computations. You can superpose the theoretical results and the experimental ones on the same graph.
 </WRAP>
-==== - [Classroom activity] Collisions and Packet Delivery Ratio ====
+==== - Collisions and Packet Delivery Ratio ====
-In this section, you will measure the impact of the packet arrival rate on the collision rate and consequently the Packet Delivery Ratio (PDR).
+In this section, you will compute the impact of the packet arrival rate on the collision rate and consequently the Packet Delivery Ratio (PDR).
-The setting for this experiment is unique:
+Let us consider an ALOHA model for the random access in a LoRaWAN network.
-  * Only one server is required in the classroom. This server should compute the ratio of successfully delivered packets or PDR.
-  * All groups are required to use the same frequency, spreading factor, and coding rate.
-  * The average packet arrival rate is equal for all clients.
 <WRAP center round help 100%>
-  * Draw the PDR as a function of the average arrival rate. Analyze your results.
+  * What are the advantages of a random access in a wireless IoT context? What are the shortcomings?
-  * What type of mathematical model enables to theoretically compute the PDR? Verify the obtained results.
 </WRAP>
-===== -. Coverage Challenge =====
+Suppose that the packet length is 50 bytes.
+<WRAP center round help 100%>
+  * What is the maximum packet generation rate for each spreading factor (SF7 to SF12)? Explain your answer.
+</WRAP>
+In the following we consider N devices transmitting 50 bytes packets using SF7. The packet generation rate is assumed to be equal to the maximum possible rate given the duty cycle limitation.
+<WRAP center round help 100%>
+  * Compute the number of successful transmissions per hour for 50, 100, and 200 devices respectively. Comment the obtained results.
+  * Plot the number of successful transmissions per hour as a function of the number of devices for SF7 and SF12. Analyse the obtained figure and attach the simulation code.
+  * Plot the packet delivery ratio as a function of the number of devices for different SFs. Give the details of your computation and the simulation code.
+  * Plot the number of successful transmissions per hour per device as a function of the number of generated packets per hour per device for 20 and for 100 devices. Note well the duty cycle limitation.
+</WRAP>
+===== - Coverage Challenge =====
 Start by identifying a set of three geographical locations or Test Points (TP). These TPs should be astutely chosen to explore the limits of LoRa coverage. Then, you should implement a function on the server that measures the ratio of successfully delivered packets or PDR (Packet Delivery Ratio). Now, you should run the experiment for three different radio configurations: such configurations should provide different reliability levels (high, medium, and low reliability).