exploring_lora
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exploring_lora [2018/09/27 16:35] – [4.1. Time on Air] samer | exploring_lora [2019/10/15 22:11] – [4.1. Time on Air] samer | ||
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As defined by Semtech, [[http:// | As defined by Semtech, [[http:// | ||
- | In this lab, you will implement a prototype of LoRa communication between two wireless | + | In this lab, you will implement a prototype of LoRa communication between two wireless |
<WRAP center round help 100%> | <WRAP center round help 100%> | ||
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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: | ||
- | * RadioHead: The Packet Radio library for embedded microprocessors can be downloaded from [[http://www.airspayce.com/mikem/ | + | * RadioHead: The Packet Radio library for embedded microprocessors can be downloaded from [[https://github.com/samerlahoud/ |
* Arduino IDE: Specific OS versions can be downloaded from [[https:// | * Arduino IDE: Specific OS versions can be downloaded from [[https:// | ||
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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 ==== | ||
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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 |
- | </WRAP> | + | For Arduino Duemilanove, |
+ | [[https:// | ||
+ | </ | ||
===== -. Theoretical Study ===== | ===== -. Theoretical Study ===== | ||
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<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 {{ : | ||
</ | </ | ||
+ | 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 ==== | ||
- | Start by setting | + | Download |
+ | |||
+ | Take a look at the source code in '' | ||
+ | |||
+ | * Central frequency | ||
+ | * Spreading Factor | ||
+ | * Bandwidth | ||
+ | * Coding Rate | ||
+ | * Transmit power | ||
+ | |||
+ | <code c++> | ||
+ | rf95.setFrequency(frequency); | ||
+ | // Setup Power,dBm | ||
+ | rf95.setTxPower(13); | ||
+ | |||
+ | // Setup Spreading Factor (6 ~ 12) | ||
+ | rf95.setSpreadingFactor(7); | ||
+ | |||
+ | // Setup BandWidth, option: 7800, | ||
+ | //Lower BandWidth for longer distance. | ||
+ | rf95.setSignalBandwidth(125000); | ||
+ | |||
+ | // Setup Coding Rate: | ||
+ | rf95.setCodingRate4(5); | ||
+ | </ | ||
+ | |||
+ | In order to reduce collisions between simultaneous experiments, | ||
^ Group Number | ^ Group Number | ||
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| | | | ||
| | | | ||
- | |||
- | For this, open the '' | ||
- | |||
- | <file cpp RH_RF95.cpp> | ||
- | setFrequency(86X.Y); | ||
- | </ | ||
- | |||
- | The typical configuration for LoRa modules consists of 125 kHz sub-channels, | ||
- | |||
- | * Bw125Cr45Sf128 | ||
- | * Bw125Cr48Sf4096 | ||
- | * Bw31_25Cr48Sf512 | ||
- | |||
- | Radio configuration is applied in '' | ||
- | <file cpp RH_RF95.cpp> | ||
- | setModemConfig(Bw125Cr45Sf128); | ||
- | </ | ||
==== -. Running Basic Sketches ==== | ==== -. Running Basic Sketches ==== | ||
- | Download the {{ : | + | Now you can compile and upload |
[{{ : | [{{ : | ||
[{{ : | [{{ : | ||
- | |||
- | In the remainder of this lab, you will conduct measurements to validate the obtained theoretical receiver sensitivity. | ||
===== -. 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:// | ||
==== -. Time on Air ==== | ==== -. 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. The ToA is the time necessary to send a message | + | In this section, you will measure the Time on Air (ToA) that is given by the time necessary to transmit |
- | 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:// | + | Start by implementing a function on the client that measures the time necessary for sending a packet. You can have recourse to the [[https:// |
- | <WRAP center round help 100%> | + | For example, the scenario |
- | * Join commented extracts of your code and explain your approach | + | |
- | * Draw a box plot of the ToA under the three different radio configurations and for three different | + | |
- | * Analyze the obtained results | + | |
- | </ | + | |
- | ==== -. Packet Delivery Ratio ==== | + | |
- | In this section, you will measure | + | As for the theoretical computation of the ToA, you can refer to the the following documents : |
- | Only for this test, all groups | + | * 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: | ||
+ | * 0 to 251 octets DATA | ||
+ | * CRC (handled internally by the radio) | ||
<WRAP center round help 100%> | <WRAP center round help 100%> | ||
- | * Draw the PER as a function of the transmission period | + | * Describe |
- | * What type of mathematical models enables to theoretically compute | + | * Join commented extracts of your code and raw data in attached files. |
+ | * Visualise the experimental results by plotting the ToA as a function of each one of the different parameters. | ||
+ | * Analyze the obtained results and compare with the theoretical computations. You can superpose the theoretical results and the experimental ones on the same graph. | ||
</ | </ | ||
+ | ==== -. [Classroom activity] Collisions and Packet Delivery Ratio ==== | ||
- | ==== -. Coverage ==== | + | In this section, you will measure 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: | ||
+ | * 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. | ||
- | In this section, you will measure | + | <WRAP center round help 100%> |
+ | * Draw the PDR as a function | ||
+ | * What type of mathematical model enables to theoretically compute | ||
+ | </WRAP> | ||
+ | ===== -. Coverage Challenge ===== | ||
- | <code c++> | + | Start by identifying a set of three geographical locations or Test Points |
- | rf95.setModemConfig(RH_RF95:: | + | |
- | rf95.setModemConfig(RH_RF95:: | + | |
- | rf95.setModemConfig(RH_RF95:: | + | |
- | </ | + | |
<WRAP center round help 100%> | <WRAP center round help 100%> | ||
- | * Draw the test points on a map. | + | * Draw the test points on a map and motivate your choices. |
- | * Give a statistical measure of the PER and the RSSI for each TP with each of the different | + | * Describe |
+ | * Visualise the experimental results by plotting the PDR for each TP and each radio configuration. | ||
+ | * Analyze the obtained results. | ||
</ | </ | ||
- | ==== -. Path Loss ==== | ||
- | In this section, you will study the properties of the radio channel | + | 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 |
+ | |||
+ | * Direct transmission between | ||
+ | * 3D distance is computed between devices. You can get the elevation from this [[ http:// | ||
+ | * PDR must be higher than 10% as computed for 100 packets. | ||
+ | * Supporting live video and screen capture should be used to authenticate | ||
+ | |||
+ | You can use the [[https:// | ||
+ | |||
+ | <WRAP center round todo 60%> | ||
+ | Take a look at this tool [[http:// | ||
+ | </ | ||
<WRAP center round help 100%> | <WRAP center round help 100%> | ||
- | * Provide | + | * Compute |
- | * Draw the RSSI values as a function | + | * Provide |
- | * What is the path loss exponent? | + | * Compare the received power obtained |
- | * Using regressions, compute a value of the path loss exponent. Analyze the result. | + | * Prepare a short presentation (5 minutes pitch) to describe your experiment. |
- | * Compare the obtained | + | |
</ | </ | ||
- | |||
- | 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:// | ||
- | ===== -. Coverage Challenge ===== | ||
- | |||
+ | <WRAP center round important 75%> | ||
+ | This challenge and the corresponding grading is considered as a part of the final project. | ||
+ | </ | ||
===== -. 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