exploring_lora
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exploring_lora [2018/09/29 15:39] – [4.3. Coverage] samer | exploring_lora [2018/10/22 15:17] – [5. Coverage Challenge] samer | ||
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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 ==== | ||
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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 {{ : | ||
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==== -. 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 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 |
[{{ : | [{{ : | ||
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==== -. Time on Air ==== | ==== -. Time on Air ==== | ||
- | In this section, you will measure the Time on Air (ToA) as 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 |
- | For this, you will 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:// |
+ | |||
+ | 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 [[http:// | ||
+ | * 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 ==== | ||
- | ==== -. [Classroom activity] Collisions and Packet Delivery Ratio ==== | + | In this section, you will measure the coverage of LoRa under different radio configurations. |
- | In this section, you will measure the Packet Delivery Ratio (PDR) under different transmission periods. Only for this test, all groups are required | + | Start by identifying a set of five geographical locations or Test Points |
- | + | ||
- | You will start by implementing | + | |
- | + | ||
<WRAP center round help 100%> | <WRAP center round help 100%> | ||
- | * Draw the PER as a function | + | * Draw the test points on a map and motivate your choices. |
- | * What type of mathematical models enables to theoretically compute | + | * Describe the radio configurations you selected and their impact on the reliability |
+ | * Visualise | ||
+ | * Analyze | ||
</ | </ | ||
+ | ==== -. [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 PDR. |
- | In this section, you will measure the coverage of LoRa under the three different radio configurations. Such configurations should ensure different reliability levels. | + | The setting for this experiment is unique: |
- | + | * Only one server is required in the classroom. This server | |
- | For this, you will start by identifying a set of geographical locations or Test Points (TP). These TPs should be astutely chosen to challenge | + | * All groups are required to use the same frequency, spreading factor, and coding rate. |
+ | * The average packet arrival rate is equal for all clients. The delay between two packets is drawn uniformly in a predefined interval. | ||
<WRAP center round help 100%> | <WRAP center round help 100%> | ||
- | * Draw the test points on a map. | + | * Draw the PDR as a function of the average arrival rate. Analyze your results. |
- | * Give a statistical measure | + | * What type of mathematical model enables to theoretically compute |
</ | </ | ||
- | ==== -. Path Loss ==== | + | ===== -. Coverage Challenge ===== |
- | In this section, you will study the properties | + | In this section, you are required to establish a record |
+ | |||
+ | * Direct transmission between | ||
+ | * 3D distance is computed between devices. You can use for example [[https:// | ||
+ | * PDR must be higher than 10% as computed for 100 packets. | ||
+ | * Supporting live video and screen capture | ||
+ | |||
+ | You can use the following online service [[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, | + | * 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