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3. Bluetooth

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Bluetooth

Introduction

  1. Bluetooth is a wireless communication technology designed for short-range data exchange between electronic devices.
  2. It operates in the unlicensed 2.4 GHz ISM frequency (Industrial, Scientific, and Medical) frequency band.
  3. It was developed by Ericsson and is now standardized under IEEE 802.15
    1. Bluetooth is managed and updated by the Bluetooth Special Interest Group (SIG).
    2. It supports both voice and data transmission.

Bluetooth Network Structure

  1. Bluetooth uses a master-slave architecture to form a network called a piconet.
  2. A piconet - 1 master 7 slave devices max
  3. Multiple piconets can interconnect to form a scatternet, where some devices act as a bridge between piconets.
  4. Devices synchronize their clocks and frequency hopping patterns with the master.

Frequency and Modulation

  1. Bluetooth uses Frequency Hopping Spread Spectrum (FHSS) to minimize interference.
  2. It hops among 79 channels at 1 MHz intervals, 1600 times per second.
  3. The modulation technique used is Gaussian Frequency Shift Keying (GFSK) for basic rate communication.

Device Classes and Range

  1. Bluetooth devices are classified based on power and range:
    • Class 1: Up to 100 meters (100 mW)
    • Class 2: Up to 10 meters (2.5 mW)
    • Class 3: Up to 1 meter (1 mW)
  2. Most consumer devices (like smartphones and headsets) use Class 2.

Versions and Enhancements

  1. Bluetooth has evolved through various versions:

    • Bluetooth 2.0 + EDR: Higher data rate (up to 3 Mbps)
    • Bluetooth 3.0 + HS: High-speed data via Wi-Fi (up to 24 Mbps)
    • Bluetooth 4.0: Introduced Bluetooth Low Energy (BLE) for power-efficient communication
    • Bluetooth 5.0/5.1/5.2: Improved range, speed, broadcast capacity, and support for direction finding

Bluetooth Profiles

  1. Bluetooth profiles define specific applications and behaviors for devices:

    • HFP (Hands-Free Profile): Used in car kits and headsets
    • A2DP (Advanced Audio Distribution Profile): For streaming high-quality audio
    • AVRCP (Audio/Video Remote Control Profile): For media control functions
    • HID (Human Interface Device): Used by keyboards, mice, and game controllers
    • FTP (File Transfer Profile): For wireless file transfer

Security Features

  1. Bluetooth provides several security mechanisms:
    • Pairing: Establishes a trusted relationship between devices
    • Authentication: Confirms device identity
    • Encryption: Ensures secure data transmission
    • Frequency Hopping: Reduces the chance of eavesdropping and interference

Applications

  1. Bluetooth is widely used in:
    • Wireless headsets, speakers, and audio systems
    • File sharing between mobile devices
    • Wireless input devices like keyboards and mice
    • Fitness trackers and wearable health monitors
    • Car infotainment systems and hands-free calling
    • Smart home and IoT device communication

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