exploring_lora
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exploring_lora [2018/09/29 22:53] – [4.1. Time on Air] samer | exploring_lora [2021/10/20 12:52] – [4.2 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: | ||
- | * Arduino Mega (x2). | + | * Arduino Mega or Arduino Duemilanove |
* LoRa shields from [[http:// | * LoRa shields from [[http:// | ||
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* Give the main characteristics of the LoRa shield from Dragino (www.dragino.com). | * Give the main characteristics of the LoRa shield from Dragino (www.dragino.com). | ||
* What type of Antenna are you using? Explain the corresponding characteristics. | * What type of Antenna are you using? Explain the corresponding characteristics. | ||
- | * Give an estimated cost of your platform. | + | * 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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<WRAP center round tip 75%> | <WRAP center round tip 75%> | ||
- | Note well the location | + | Make sure to restart your computer after the installation |
</ | </ | ||
- | ==== -. Installation ==== | + | |
+ | |||
+ | ==== - 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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Connect the two Arduino devices to USB ports on your computer. If this is the first time you use Arduino IDE, make sure to install the necessary USB drivers by selecting '' | Connect the two Arduino devices to USB ports on your computer. If this is the first time you use Arduino IDE, make sure to install the necessary USB drivers by selecting '' | ||
- | Now, you have to choose the '' | + | Now, you have to choose the '' |
<WRAP center round tip 75%> | <WRAP center round tip 75%> | ||
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:// | ||
- | </WRAP> | + | 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? | ||
- | * For each of the three possible | + | * What is the transmission bit rate for each of the following |
+ | * Configuration 1: channel bandwidth = 125 kHz, spreading factor = 7, coding rate = 4/5 | ||
+ | * Configuration 2: channel bandwidth = 500 kHz, spreading factor = 7, coding rate = 4/5 | ||
+ | * Configuration 3: channel bandwidth = 125 kHz, spreading factor = 12, coding rate = 1/2 | ||
* Compute the receiver sensitivity, | * Compute the receiver sensitivity, | ||
* Compare the computed sensitivity to that provided by the {{ : | * Compare the computed sensitivity to that provided by the {{ : | ||
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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 '' |
- | * Central frequency | + | * Central frequency |
- | * Spreading Factor | + | * Spreading Factor |
- | * Bandwidth | + | * Bandwidth |
- | * Coding Rate (CR) | + | * Coding Rate |
- | * Transmit power (Pow) | + | * Transmit power |
<code c++> | <code c++> | ||
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</ | </ | ||
- | In order to reduce collisions, configure the central frequency of your LoRa devices as indicated below: | + | In order to reduce collisions |
^ Group Number | ^ Group Number | ||
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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 packet |
- | + | ||
- | 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 | + | |
[{{ : | [{{ : | ||
[{{ : | [{{ : | ||
- | ===== -. 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 packet on the radio interface. You will assess the impact of the spreading factor, bandwidth, coding rate, and packet size on the ToA. | ||
+ | |||
+ | 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 packets for three different spreading factors //e.g.,// 7, 9, and 10, and drawing the average ToA or the distribution in a boxplot for comparing the results. | ||
+ | |||
+ | 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:// | ||
- | In this section, you will measure the Time on Air (ToA) that is given by the time necessary to transmit a message on the radio interface | + | Note that all messages sent and received |
- | Start by implementing a function on the client that measures the time necessary for sending a message. For example, you can use the [[https:// | + | * 8 symbol PREAMBLE |
+ | * Explicit header with header CRC (handled internally | ||
+ | * 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 measure | + | In this section, you will compute |
- | For this, you will start by identifying a set of geographical locations or Test Points (TP). These TPs should be astutely chosen to explore | + | Let us consider an ALOHA model for the random access in a LoRaWAN network. |
<WRAP center round help 100%> | <WRAP center round help 100%> | ||
- | * Draw the test points on a map and motivate your choices. | + | * What are the advantages of a random access in a wireless IoT context? What are the shortcomings? |
- | * Visualise the experimental results by plotting the PDR for each TP and each radio configuration. | + | |
- | * Analyze | + | |
</ | </ | ||
- | ==== -. [Classroom activity] Collisions and Packet Delivery Ratio ==== | ||
- | In this section, you will measure | + | Suppose that the packet length is 50 bytes. |
- | The setting for this experiment | + | <WRAP center round help 100%> |
+ | * What is the maximum packet generation rate for each spreading factor (SF7 to SF12)? Explain your answer. | ||
+ | </ | ||
- | * Only one server is required in the classroom. This server should compute the ratio of successfully delivered | + | In the following we consider N devices transmitting 50 bytes packets |
- | * All groups are required | + | |
<WRAP center round help 100%> | <WRAP center round help 100%> | ||
- | * Draw the PER as a function | + | * Compute |
- | * What type of mathematical models enables to theoretically compute the PER? | + | |
- | </ | + | |
- | ===== -. Coverage Challenge ===== | + | * 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. |
- | In this section, you will study the properties | + | * Plot the packet delivery ratio as a function |
+ | |||
+ | * Plot the number of successful transmissions per hour per device | ||
+ | </ | ||
+ | ===== - Coverage Challenge ===== | ||
+ | |||
+ | Start by identifying a set of three geographical locations or Test Points (TP). These TPs should be astutely chosen to explore | ||
<WRAP center round help 100%> | <WRAP center round help 100%> | ||
- | * Provide | + | * Draw the test points on a map and motivate your choices. |
- | * Draw the RSSI values as a function | + | * Describe |
- | * What is the path loss exponent? | + | * Visualise |
- | * Using regressions, | + | * Analyze |
- | * Compare | + | |
</ | </ | ||
- | |||
- | 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:// | ||
+ | You are now required to establish a record of LoRa coverage. You can certainly unleash your scientific imagination, | ||
- | ===== -. Grading ===== | + | * Direct transmission between the two devices is only considered. |
+ | * 3D distance is computed between devices [[http:// | ||
+ | * PDR must be higher than 10% as computed for 100 packets. | ||
+ | * Supporting live video and screen capture should be used to authenticate the record. | ||
+ | |||
+ | You can use [[https:// | ||
+ | |||
+ | <WRAP center round help 100%> | ||
+ | * Compute the Fresnel zone for your transmission. Comment the result. | ||
+ | * Provide the expression of the link budget and compute the received power using two different path loss models (ITM, Line of sight) with Cloud RF. | ||
+ | * Compare the received power obtained experimentally with the results of the online simulators. | ||
+ | * Prepare a short presentation (5 minutes pitch) to describe your experiment. | ||
+ | </ | ||
+ | |||
+ | <WRAP center round important 75%> | ||
+ | This challenge and the corresponding grading is considered as a part of the final project. | ||
+ | </ | ||
+ | ===== - 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