exploring_lora
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exploring_lora [2018/10/06 14:04] – [4.3. [Classroom activity] Collisions and Packet Delivery Ratio] samer | exploring_lora [2021/10/20 12:51] – [4.2 [Classroom activity] Collisions and Packet Delivery Ratio] samer | ||
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- | ===== -. Setting the Lab ===== | + | ===== - Setting the Lab ===== |
- | ==== -. Hardware Platform ==== | + | ==== - Hardware Platform ==== |
In order to design and implement experiments with LoRa, you will use the following devices: | 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 devices. | * Give an estimated cost of your devices. | ||
</ | </ | ||
- | ==== -. Software Tools ==== | + | ==== - Software Tools ==== |
Download the following software on your PC: | Download the following software on your PC: | ||
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Unzip the RadioHead library and copy it to your sketchbook library folder as detailed in [[https:// | Unzip the RadioHead library and copy it to your sketchbook library folder as detailed in [[https:// | ||
- | ==== -. Installation ==== | + | |
+ | <WRAP center round tip 75%> | ||
+ | Make sure to restart your computer after the installation of Arduino IDE and run the software as administrator. | ||
+ | </ | ||
+ | |||
+ | |||
+ | ==== - Installation ==== | ||
Start by plugging the Dragino shields on the Arduino devices and mounting the antennas as shown in Fig. 1. | 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:// | For Arduino Mega 2560, additional drivers for Microsoft Windows can be installed from [[http:// | ||
+ | For Arduino Duemilanove, | ||
+ | [[https:// | ||
+ | |||
</ | </ | ||
- | ===== -. Theoretical Study ===== | + | ===== - 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. | 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%> | <WRAP left round help 100%> | ||
- | * What is the relation between processing gain and spreading factor in LoRa modulation? | + | * What is the relation between processing gain and spreading factor in LoRa modulation? |
* How does the spreading factor impact the coverage of a LoRa transmitter? | * How does the spreading factor impact the coverage of a LoRa transmitter? | ||
* What is the transmission bit rate for each of the following configurations of your LoRa device? Explain your computation. | * What is the transmission bit rate for each of the following configurations of your LoRa device? Explain your computation. | ||
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In the remainder of this lab, you will conduct measurements to validate the obtained theoretical receiver sensitivity. | 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 ==== | + | ==== - Modifying the Radio Parameters ==== |
- | Download the {{ : | + | Download the {{ : |
Take a look at the source code in '' | Take a look at the source code in '' | ||
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| | | | ||
| | | | ||
- | ==== -. Running Basic Sketches ==== | + | ==== - Running Basic Sketches ==== |
- | Now you can compile and upload the client and server sketches on the two arduino devices, respectively. On the serial interfaces, you should obtain similar results as in Fig. 2 and Fig. 3. The client sends periodically a short message | + | Now you can compile and upload the client and server sketches on the two arduino devices, respectively. On the serial interfaces, you should obtain similar results as in Fig. 2 and Fig. 3. The client sends periodically a short packet |
[{{ : | [{{ : | ||
[{{ : | [{{ : | ||
- | ===== -. Performance Evaluation ===== | + | ===== - 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:// | 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:// | ||
As we are in presence of variable radio conditions, some experiments should be repeated multiple times and results can be shown as probability distributions. Take a look at this excellent repository of data visualisation tools [[https:// | As we are in presence of variable radio conditions, some experiments should be repeated multiple times and results can be shown as probability distributions. Take a look at this excellent repository of data visualisation tools [[https:// | ||
- | ==== -. Time on Air ==== | + | ==== - Time on Air ==== |
- | In this section, you will measure the Time on Air (ToA) that is given by the time necessary to transmit a message | + | In this section, you will measure the Time on Air (ToA) that is given by the time necessary to transmit a packet |
- | Start by implementing a function on the client that measures the time necessary for sending a message. You can have recourse to the [[https:// | + | Start by implementing a function on the client that measures the time necessary for sending a packet. You can have recourse to the [[https:// |
- | For example, the scenario for assessing the impact of the spreading factor on the ToA consists of sending 100 messages | + | For example, the scenario for assessing the impact of the spreading factor on the ToA consists of sending 100 packets |
+ | |||
+ | As for the theoretical computation of the ToA, you can refer to the the following documents : | ||
+ | |||
+ | * The Semtech {{ : | ||
+ | * An explanatory video: https:// | ||
+ | * Various calculation tools available online: https:// | ||
+ | |||
+ | Note that all messages sent and received by the [[https:// | ||
+ | |||
+ | * 8 symbol PREAMBLE | ||
+ | * Explicit header with header CRC (handled internally by the radio) | ||
+ | * 4 octets HEADER: (TO, FROM, ID, FLAGS) | ||
+ | * 0 to 251 octets DATA | ||
+ | * CRC (handled internally by the radio) | ||
<WRAP center round help 100%> | <WRAP center round help 100%> | ||
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* Analyze the obtained results and compare with the theoretical computations. You can superpose the theoretical results and the experimental ones on the same graph. | * Analyze the obtained results and compare with the theoretical computations. You can superpose the theoretical results and the experimental ones on the same graph. | ||
</ | </ | ||
- | ==== -. Coverage | + | ==== - Collisions and Packet Delivery Ratio ==== |
+ | |||
+ | In this section, you will compute the impact of the packet arrival rate on the collision rate and consequently the Packet Delivery Ratio (PDR). | ||
+ | |||
+ | Let us consider an ALOHA model for the random access in a LoRaWAN network. | ||
+ | |||
+ | * What are the advantages of a random access in a wireless IoT context? What are the shortcomings? | ||
+ | |||
+ | Suppose that the packet length is 50 bytes. | ||
+ | |||
+ | * What is the maximum packet generation rate for each spreading factor (SF7 to SF12)? Explain your answer. | ||
+ | |||
+ | 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. | ||
+ | |||
+ | * 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. | ||
- | In this section, you will measure | + | * Plot the number |
+ | ===== - Coverage Challenge ===== | ||
- | Start by identifying a set of five 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: | + | 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: |
<WRAP center round help 100%> | <WRAP center round help 100%> | ||
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* Analyze the obtained results. | * Analyze the obtained results. | ||
</ | </ | ||
- | ==== -. [Classroom activity] Collisions and Packet Delivery Ratio ==== | ||
- | In this section, you will measure | + | You are now required to establish a record of LoRa coverage. You can certainly unleash your scientific imagination, but some rules must be followed to validate |
- | The setting for this experiment | + | * Direct transmission between the two devices |
- | * Only one server | + | * 3D distance |
- | * All groups are required | + | * PDR must be higher than 10% as computed for 100 packets. |
- | * On each client, the same average arrival rate for all groups. | + | * Supporting live video and screen capture should be used to authenticate the record. |
+ | |||
+ | You can use [[https:// | ||
<WRAP center round help 100%> | <WRAP center round help 100%> | ||
- | * Draw the PDR as a function of the average arrival rate. Analyze | + | * Compute |
- | * What type of mathematical model enables to theoretically | + | * Provide the expression |
+ | * Compare | ||
+ | * Prepare a short presentation (5 minutes pitch) to describe your experiment. | ||
</ | </ | ||
- | ===== -. Coverage Challenge ===== | ||
- | In this section, you are required to establish a record of LoRa coverage. You can certainly unleash your scientific imagination, | + | <WRAP center round important 75%> |
- | + | This challenge and the corresponding grading is considered as a part of the final project. | |
- | * Direct transmission between the two devices is only considered. | + | |
- | * 3D distance is computed between devices. | + | |
- | * PDR must be higher than 10% as computed for 100 packets. | + | |
- | + | ||
- | <WRAP center round help 100%> | + | |
- | * Compute | + | |
- | * Provide the expression | + | |
- | * Compare the received power obtained experimentally with the theoretical results. | + | |
- | * Write an article (blog, wiki, ...) to describe your experiment. | + | |
</ | </ | ||
- | ===== -. Grading ===== | + | ===== - Grading ===== |
- | | ^ Exemplary | + | | |
- | ^ Answer | + | ^ Techniques for Engineering Practice |
- | ^ Design experiments | + | ^ Skills for Engineering Practice |
- | ^ Analyse results | + | ^ Engineering tools | Students showed advanced ability |
+ | ^ Problem solving | ||
+ | ^ Results and analysis | ||
+ | ^ Motivation, initiative, and creativity | ||
+ | ^ Written communication skills | ||
+ | ^ Scientific referencing |
exploring_lora.txt · Last modified: 2021/10/20 12:52 by samer