Bluetooth

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Contents

Overview

Bluetooth is an open, wireless communication standard for radio-based data exchange over short distances and PANs. It is manages by the Bluetooth Special Interest Group.


Technical Details

Bluetooth operated from 2402-2480 MHz using up to 79 bands utilizing frequency-hopping spread spectrum technology. This band is within the unlicensed ISM (Industrial, Science, Medical) 2.4GHz band. However, there are various classifications of Bluetooth devices as follows:

ClassMax. PowerMax. Range
Class 1100 mW~100m
Class 22.5 mW~10m
Class 31 mW~1m


Original specifications use Gaussian frequency-shift keying (GFSK) modulation to function. However, Bluetooth 2.0+EDR allows the use of π/4-DQPSK and 8DPSK (Phase Key Shifting techniques). GFSK is classified as Basic Rate (BR), while π/4-DQPSK and 8DPSK are classified as Endhanced Data Rate (EDR).

SpecificationDate Rate
GFSK~1 Mbit/s
π/4-DPSK~2 Mbit/s
8DPSK~3 Mbit/s

Bluetooth operates with a master/slave structure. A master can communicate with up to 7 slaves. Slave devices operate off of the master device's clock. Packets are sent based on clock-time, at 312.5 µs intervals, with each slot taking two intervals. The master will transmit in even slots and the slaves will transmit in odd slots. Packets can be 1, 3, or 5 slots long.

Devices have the ability to switch roles at any time, so any slave can become the master device, but in a given period data can only be transferred between the master and one other device. The master chooses one device at a time, and typically allocates data equally between all connected devices, looping through each device (Round-Robin scheduling). Each small network (piconet) can connect to other piconets to create a scatternet. In this case devices can act as bridges, where one device will be a master for one network while simultaneously being the slave in another.


Interface

Bluetooth contains several mandatory core protocols: LMP (Link Management Protocol), L2CAP (Logical Link Control & Adaptation Protocol), and SDP (Service Discovery Protocol). The HCI (Host/Controller Interface) and RFCOMM (Serial Port Emulation) protocols are widely implemented. A Bluetooth Stack is a particular implementation of the various protocols.

Controller Stack Protocols

  • Asynchronous Connection-Criented [Logical Transport] (ACL)
  • Synchronous Connection Criented (SCO) link
  • Link Management Protocol (LMP)
  • Host/Controller Interface (HCI)
  • Low Energy Link Layer (LE LL)

Host Stack Protocols

  • Logical Link Control and Adaptation Protocol (L2CAP)
  • Bluetooth Network Encapsulation Protocol (BNEP)
  • Radio Frequency Communication (RFCOMM)
  • Service Discovery Protocol (SDP)
  • Telephony Control Protocol (TCP)
  • Audio/visual Control Transport Protocol (AVCTP)
  • Audio/visual Data Transport Protocol (AVDTP)
  • Object Exchange (OBEX)
  • Low Energy Attribute Protocol (ATT)
  • Low Energy Security Manager Protocol (SMP)

Versions

The Bluetooth Special Interest Group has defined several different Bluetooth versions:

  • Bluetooth v1.0 and v1.0B
  • Bluetooth v1.1
  • Bluetooth v1.2
  • Bluetooth v2.0 + EDR (Enhanced Data Rate)
  • Bluetooth v2.1 + EDR (Enhanced Data Rate)
  • Bluetooth v3.0 + HS
  • Bluetooth v4.0


Links


This page is an Article on bildr. Articles are pages that define or explain a concept, method, or generic item.

NOTE: All information contained within this article is pure opinion. Although this article is intended to help people, it may contain faulty or misleading information. This article is not to be considered professional opinion or advice, and is in no way a replacement for reading all safety/instructional documentation. Always remember to protect yourself when handling/using hazardous materials, as well as test new techniques before using them on projects/work intended to be handed in or used.

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