exploring_lora
Differences
This shows you the differences between two versions of the page.
Both sides previous revisionPrevious revisionNext revision | Previous revisionNext revisionBoth sides next revision | ||
exploring_lora [2018/09/29 13:02] – samer | exploring_lora [2021/10/20 12:51] – [4.2 [Classroom activity] Collisions and Packet Delivery Ratio] samer | ||
---|---|---|---|
Line 9: | Line 9: | ||
</ | </ | ||
- | ===== -. 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:// | ||
Line 22: | Line 22: | ||
* 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: | ||
Line 34: | Line 33: | ||
<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. | ||
Line 44: | Line 45: | ||
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 {{ : | ||
Line 63: | Line 69: | ||
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++> | ||
Line 93: | Line 99: | ||
</ | </ | ||
- | 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 | ||
Line 108: | Line 114: | ||
| | | | ||
| | | | ||
+ | ==== - 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:// | ||
- | ==== -. Time on Air ==== | + | 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 ==== | ||
- | 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 | + | As for the theoretical |
- | * Analyze the obtained results | + | |
- | </ | + | * The Semtech {{ :ds_sx1276-7-8-9_w_app_v5.pdf |specification}} (section 4.1.1.6) |
- | ==== -. Packet Delivery Ratio ==== | + | * An explanatory video: https:// |
+ | * Various calculation tools available online: https:// | ||
- | In this section, you will measure the Packet Error Rate (PER) under the three different radio configurations | + | Note that all messages sent and received |
- | Only for this test, all groups are required | + | * 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%> | ||
- | * 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. | ||
</ | </ | ||
+ | ==== - Collisions and Packet Delivery Ratio ==== | ||
- | ==== -. Coverage ==== | + | 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. | ||
- | In this section, you will measure | + | * What are the advantages |
- | <code c++> | + | Suppose that the packet length is 50 bytes. |
- | rf95.setModemConfig(RH_RF95:: | + | |
- | rf95.setModemConfig(RH_RF95:: | + | * What is the maximum packet generation rate for each spreading factor |
- | rf95.setModemConfig(RH_RF95:: | + | |
- | </ | + | 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. | ||
+ | |||
+ | * 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. | ||
+ | ===== - Coverage Challenge ===== | ||
+ | |||
+ | Start by identifying a set of three geographical locations or Test Points | ||
<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 [[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 [[https:// | ||
<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 ===== | + | | |
- | + | ^ Techniques for Engineering Practice | |
- | | ^ Exemplary | + | ^ Skills for Engineering Practice |
- | ^ Answer | + | ^ Engineering tools | Students showed advanced ability |
- | ^ Design experiments | + | ^ Problem solving |
- | ^ Analyse results | + | ^ Results and analysis |
+ | ^ Motivation, initiative, and creativity | ||
+ | ^ Written communication skills | ||
+ | ^ Scientific referencing |
exploring_lora.txt · Last modified: 2021/10/20 12:52 by samer