Dual Directional Antenna Based Localization

Overview

This project implements a dual directional antenna–based RF localization system using ESP32, LoRa RF modules, Mosquitto MQTT, and a React (Vite) dashboard. The system estimates the relative direction and position of a transmitter by analyzing received signal characteristics from directional antennas connected to spatially separated receiver nodes.

Mosquitto MQTT Broker Setup with ESP32 and React Dashboard on Windows

This guide will help you set up a Mosquitto MQTT broker on Windows, connect ESP32 devices for IoT communication, and run a React dashboard for monitoring and control in a dual directional antenna-based localization system.

Project Structure

project-root/
├── dashboard/             # Vite React web application
│   ├── package.json
│   ├── src/
│   └── ...
├── receiver/
│   └── receiver.ino      # ESP32 receiver code
├── transmitter/
│   └── transmitter.ino   # ESP32 transmitter code
└── README.md

Hardware Setup

Signal Generation and Reception

• LoRa RF modules are used for both transmission and reception

• Operates in sub-GHz ISM bands (e.g., 433 MHz, 868 MHz, 915 MHz)

• Chosen for:

  • Long-range capability
  • Robust link budget
  • RSSI and SNR reporting

ESP32 Configuration

• Transmitter ESP32

  • No WiFi required
  • RF-only operation
  • Board-specific identifier

• Receiver ESP32

  • WiFi enabled
  • MQTT client
  • Publishes RF measurements to broker

Power Supply

• Buck converter strongly recommended
• Avoid powering ESP32 directly from linear regulators
• Prevents brownout during WiFi transmission peaks

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Antenna Design and Optimization

Transmission Frequency

• The system operates at 433 MHz, chosen for its availability in the ISM band and compatibility with LoRa modules.

Antenna Selection

• A Yagi–Uda antenna was designed and built for the transmitter.

• Design goals:

  • Directional radiation pattern for localization
  • High gain with moderate beamwidth
  • Minimized side and back lobes

Simulation and Optimization

• 4NEC2 software was used to simulate antenna parameters and optimize performance.

• Simulations included:

  • Element lengths and spacing
  • Radiation pattern (gain, beamwidth, front-to-back ratio)
  • Impedance characteristics

• Optimization aimed to achieve:

  • Maximum forward gain
  • VSWR < 2:1 at 433 MHz
  • Balanced element excitation

Reference Design

• Balanis’ “Antenna Theory: Analysis and Design” was used to determine:

  • Uncompensated element lengths
  • Compensated lengths after accounting for practical construction factors

• These calculations ensured theoretical guidance aligned with practical design. See page number 594 - 597

Reference:
C. A. Balanis, Antenna Theory: Analysis and Design, 4th Edition, John Wiley & Sons, 2016.

Optimized Uncompensated Lengths of Parasitic Elements for Yagi-Uda Antennas

• Uncompensated element lengths
• Compensated lengths after accounting for practical construction factors
• These calculations ensured theoretical guidance aligned with practical design.

Impedance Matching

• A matching circuit was calculated using 4NEC2 to ensure proper impedance matching between the Yagi antenna and the 50 Ω LoRa transmitter.

• Goals:

  • Minimize reflection coefficient
  • Maximize power transfer to the antenna

• Typical approach included LC network optimization.

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Balun Considerations

• A balun (balanced-to-unbalanced transformer) is recommended for Yagi antennas to:

  • Suppress common-mode currents on the feedline
  • Maintain radiation pattern integrity
  • Ensure balanced operation between antenna and coax

• While not yet implemented, a 1:1 or 4:1 current balun can be added at the feedpoint for improved performance.

Summary

radiation-pattern-and-impedance-matching

• The final antenna design combines simulation-based optimization, practical corrections, and matching network design to achieve reliable RF transmission at 433 MHz.
• Future improvements include balun implementation to further reduce feedline radiation and improve impedance matching.

Software Setup

Prerequisites

• Windows 10/11
• ESP32 development board(s)
• Arduino IDE or PlatformIO
• Node.js (for React dashboard)
• WiFi network access

Step 1: Install Mosquitto on Windows

1. Download Mosquitto

   • Visit mosquitto.org/download
   • Download the Windows installer (64-bit recommended)
   • Run the installer as administrator

2. Add Mosquitto to System PATH

   • Open System Properties → Advanced → System Variables
   • Add C:\Program Files\mosquitto to your PATH variable

Step 2: Create Required Directories

Create the following directories for Mosquitto data and logs:

mkdir C:\mosquitto\data
mkdir C:\mosquitto\log

Step 3: Configure Mosquitto

1. Navigate to C:\Program Files\mosquitto
2. Open mosquitto.conf file (create if it doesn't exist)
3. Add the following configuration at the end of the file:

# Allow anonymous connections
allow_anonymous true

# Plain MQTT (ESP32, MQTT clients)
listener 1883
protocol mqtt

# WebSockets (browser dashboard)
listener 9002
protocol websockets

# Persistence & logging
persistence true
persistence_location C:\mosquitto\data\
log_dest file C:\mosquitto\log\mosquitto.log

Step 4: Start Mosquitto Service

Open Command Prompt as administrator and run:

net start mosquitto

Expected output:

The Mosquitto Broker service is starting.
The Mosquitto Broker service was started successfully.

Step 5: Find Your PC's IP Address

Open Command Prompt and run:

ipconfig

Note your IPv4 address (e.g., 10.214.162.1)

Step 6: ESP32 Setup

Power Supply Recommendation

Important: For reliable operation, it's recommended to use a buck converter for powering ESP32 boards instead of the onboard voltage regulator. This ensures stable power delivery and prevents brownouts during WiFi transmission.

Transmitter Setup

1. Open Arduino IDE or PlatformIO
2. Load the transmitter/transmitter.ino file
3. Update the following variables in the code:
   • ANTENNA_FREQUENCY: Set your desired antenna frequency design (e.g., 433E6 for 433MHz, 915E6 for 915MHz)
   • BOARD_ID: Set to "board1" or "board2" depending on which transmitter this is
4. Upload the code to your ESP32 transmitter device

Note: The transmitter does not require WiFi or MQTT configuration as it communicates directly via radio frequency.

Receiver Setup

1. Load the receiver/receiver.ino file
2. Update the following variables in the code:
   • ssid: Your WiFi network name
   • password: Your WiFi password
   • mqtt_server: Your PC's IP address (from Step 5)
   • ANTENNA_FREQUENCY: Set to match your transmitter's frequency (e.g., 433E6 for 433MHz, 915E6 for 915MHz)
   • BOARD_ID: Set to "board1" or "board2" to match the corresponding transmitter
3. Upload the code to your ESP32 receiver device

Step 7: React Dashboard Setup

Install Dependencies

1. Navigate to the dashboard directory:

cd dashboard

2. Install the required packages:

npm install

Run the Development Server

Start the React development server:

npm run dev

The dashboard should now be accessible at http://localhost:5173 (or the port specified by Vite).

Step 8: Testing the System

Monitor ESP32 Communication

Open Command Prompt and run:

mosquitto_sub -h 10.214.162.1 -t "esp32/+"

This will subscribe to all ESP32-related topics and show data received from the transmitter via the receiver.

Test Individual Topics

Monitor receiver status and data:

mosquitto_sub -h 10.214.162.1 -t "esp32/receiver/status"
mosquitto_sub -h 10.214.162.1 -t "esp32/receiver/data"

Monitor board-specific data:

mosquitto_sub -h 10.214.162.1 -t "esp32/board1/+"
mosquitto_sub -h 10.214.162.1 -t "esp32/board2/+"

Control receiver via MQTT:

mosquitto_pub -h 10.214.162.1 -t "esp32/receiver/control" -m "reset"

Note: The transmitter communicates via RF only and does not publish directly to MQTT. All MQTT communication comes through the receiver.

Command Breakdown

mosquitto_sub Commands

mosquitto_sub -h 10.214.162.1 -t "esp32/+"

• -h 10.214.162.1: Specifies the MQTT broker's IP address
• -t "esp32/+": Subscribes to all topics starting with "esp32/" (wildcard subscription)

mosquitto_pub Commands

mosquitto_pub -h 10.214.162.1 -t "esp32/transmitter/control" -m "start"

• -h 10.214.162.1: Specifies the MQTT broker's IP address
• -t "esp32/transmitter/control": Sets the target topic
• -m "start": Sends the message "start" to the topic

Development Workflow

Starting the Complete System

1. Start Mosquitto Broker:

   net start mosquitto

2. Start React Dashboard:

   cd dashboard
   npm run dev

3. Flash and Connect ESP32 Devices:

   • Upload transmitter.ino to transmitter ESP32 (configure ANTENNA_FREQUENCY and BOARD_ID)
   • Upload receiver.ino to receiver ESP32 (configure WiFi, MQTT, ANTENNA_FREQUENCY, and BOARD_ID)
   • Transmitter will start broadcasting via RF
   • Receiver will connect to WiFi and MQTT broker, forwarding received RF data

4. Access Dashboard:

   • Open browser to http://localhost:5173
   • Monitor real-time localization data from ESP32 devices
   • Send commands through the web interface

Dashboard Features

The React dashboard provides:

• Real-time MQTT message monitoring from receiver
• Localization data visualization and tracking
• Device status indicators for receiver and connected transmitters
• Interactive controls for receiver device
• WebSocket connection to Mosquitto (port 9002)
• Board-specific data visualization (board1, board2)
• RF signal strength and directional antenna monitoring
• Real-time positioning and triangulation display
• Responsive design for desktop and mobile

Troubleshooting

Common Issues

1. Mosquitto service won't start:

   • Check if port 1883 is already in use
   • Run Command Prompt as administrator
   • Verify configuration file syntax

2. ESP32 devices can't connect:

   • Receiver issues:
     • Ensure receiver ESP32 and PC are on the same network
     • Check Windows Firewall settings (allow ports 1883, 9002)
     • Verify the IP address is correct in receiver code
     • Make sure Mosquitto service is running
   • Transmitter issues:
     • Check antenna frequency configuration matches receiver
     • Verify BOARD_ID is properly set and unique
     • Ensure proper power supply (use buck converter)
     • Check RF transmission range

3. React dashboard won't start:

   • Ensure Node.js is installed
   • Run npm install in the dashboard directory
   • Check for port conflicts (default: 5173)

4. WebSocket connection fails:

   • Verify Mosquitto is configured for WebSockets (port 9002)
   • Check browser console for connection errors
   • Ensure firewall allows port 9002

Firewall Configuration

Allow Mosquitto through Windows Firewall:

1. Open Windows Defender Firewall
2. Click "Allow an app or feature through Windows Defender Firewall"
3. Add mosquitto.exe and allow both private and public networks
4. Ensure ports 1883 and 9002 are open

File Structure Details

C:\Program Files\mosquitto\
├── mosquitto.conf          # Configuration file
├── mosquitto.exe          # Main executable
└── ...

C:\mosquitto\
├── data\                  # Persistence data
└── log\                   # Log files
    └── mosquitto.log

project-root/
├── dashboard/             # React dashboard
│   ├── package.json
│   ├── vite.config.js
│   ├── src/
│   │   ├── App.jsx
│   │   ├── components/
│   │   └── ...
│   └── dist/             # Built files (after npm run build)
├── receiver/
│   └── receiver.ino      # ESP32 receiver firmware
└── transmitter/
    └── transmitter.ino   # ESP32 transmitter firmware

Additional Commands

Stop Services

# Stop Mosquitto
net stop mosquitto

# Stop React dev server
# Press Ctrl+C in the terminal running npm run dev

View Logs

# View Mosquitto logs
type C:\mosquitto\log\mosquitto.log

# View real-time logs
tail -f C:\mosquitto\log\mosquitto.log

Build Dashboard for Production

cd dashboard
npm run build

Security Notes

This configuration allows anonymous connections for testing purposes. For production use, consider:

• Setting up username/password authentication
• Using SSL/TLS encryption
• Configuring proper access control lists
• Disabling anonymous access
• Using environment variables for sensitive data

Note: Transmitter boards communicate via RF to the receiver, which then publishes the data to appropriate MQTT topics based on BOARD_ID.

License

This setup guide is provided as-is for educational and development purposes.