BlueTooth Protocol

Introduction To BlueTooth Protocol

Nowadays, technology and engineering both are changing every year and human thinking to seat in a place and everything should be done. To make automatic everything, we are using different electronic devices in our day-to-day life which makes life easy. When the computer developed or any electronic devices, we are supposed to use the wires to connect the devices for data or information transmission or reception. But it not good always to use the wire when there are some dynamic devices or anything. If you’ve ever hooked up a computer and half a dozen peripherals (add-on’s), a digital television and a DVD player, or run your own telephone extensions through the house, you’ll know just what a pain all those cables can be. Wouldn’t it be nice if there were a way of beginning electronic gadgets together so they could share whatever signals they need without any wires at all? To prevent this, the BlueTooth Protocol is the solution for a short range of wireless communication.

History Of BlueTooth Protocol:

The Bluetooth word originated from the name of Harald Blaatand a Danish king who united the Scandinavians in the 10th century. The Bluetooth Wireless Technology (BWT) was developed in 1994 at Ericsson in Sweden. After then they made a Group of members called Bluetooth Special Interest Group (SIG) to maintain the BlueTooth Protocol standard.

The Bluetooth Special Interest Group (Bluetooth SIG) is the standards organization that oversees the development of BlueTooth Protocol standards and the licensing of the Bluetooth technologies and trademarks to manufacturers. The Bluetooth SIG is a not-for-profit, non-stock corporation founded in September 1998.

What is Bluetooth?

The BlueTooth Protocol is similar to RF technology, but it’s mainly designed for communicating over short distances less than about 10m or 30ft. Typically, you might use it to download photos from a digital camera to a PC, to hook up a wireless mouse to a laptop, to link a hands-free headset to your cell-phone so you can talk and drive safely at the same time, and so on. Electronic gadgets that work this way have built-in radio antennas (transmitters and receivers) so they can simultaneously send and receive wireless signals to other Bluetooth gadgets. Older gadgets can be converted to work with the Bluetooth using plug-in adapters (in the form of USB sticks, PCMCIA laptop cards, and so on).

Definition: The BlueTooth is a standardized, short-range, low-power, low-cost, RF-based wireless communication protocol. It is used to send or receive the data over the air between the electronic devices.

How BlueTooth Protocol Works?

The Bluetooth protocol is an RF-based technology that operates at 2.4GHz using frequency hopping spread spectrum in the same unlicensed ISM frequency band where RF protocols like ZigBee and WiFi also exist. There is a standardized set of rules and specifications that differentiates it from other protocols. It can work as a Master, slave, piconet, or scattered.

The Bluetooth sends and receives radio waves in a band of 79 different frequencies nothing but the channels centered on 2.45 GHz bandwidth. The Bluetooth uses this bandwidth which is set apart from radio, television, and cellphones, and reserved for use by industrial, scientific, and medical gadgets. The BlueTooth Protocol devices automatically detect and connect to one another and up to eight of them can communicate at any one time. They don’t interfere with one another because each pair of devices uses a different one of the 79 available channels. If two devices want to talk, they pick a channel randomly and, if that’s already taken, randomly switch to one of the others (a technique is known as spread-spectrum frequency hopping). To minimize the risks of interference from other electrical appliances (and also to improve security), pairs of devices constantly shift the frequency they’re using—thousands of times a second.

Frequency Hopping Spread Spectrum:

Before talking about this let’s go discuss the frequency hopping and spread spectrum separately.

What is Frequency Hopping?

The BlueTooth Protocol using one of the most important technology for changing its frequency for security purposes called frequency hopping. The frequency Hopping is a method of changing the RF signal carrier frequency according to a hopping pattern. Which caused the signal to see a different channel and a different set of interfering signals during each hop. This avoids the problem of the failing communication at a particular frequency, because of a fade or a particular interferer.

Frequency hopping is a technique mainly used to keep two or more RFID readers from interfering with each other while reading RFID tags in the same remote area. Each reader initiates its operating program, and, once it receives a frequency hop trigger signal, the frequency hopping sequence is then selected from the available operating frequencies. The reader then prompts the RF module to switch to a frequency channel described in the hopping sequence and stays there for 0.4 seconds. Once completed, the reader will stop transmitting and store the channel it was using. The reader will then continue to use the same sequence if a new trigger signal arrives in less than 30 seconds. Because of this rapid hopping among various frequencies, multiple readers and tags are allowed to communicate with one another with minimal, if any, reader collision. This method used in the BlueTooth Protocol for the prevention of interfering between the more than one Bluetooth device.

What is Spread Spectrum?

The Spread spectrum is a form of wireless communications in which the frequency of the transmitted is signal deliberately varied. This results in the much greater bandwidth than the signal would have if its frequency were not varied.

What Is Frequency Hopping Spread Spectrum?

Frequency-hopping spread spectrum (FHSS) transmission is the repeated switching of the frequencies during radio transmission to reduce interference and avoid interception. It is useful to counter eavesdropping or to obstruct jamming of telecommunications. And it can minimize the effects of unintentional interference.

BlueTooth Protocol Master-Slave Communication:

In BlueTooth Protocol, the basic communication for two electronic devices is like one will initiate the communication called as a master for sending or receiving the data where is another will respond to others called as a slave. This communication method called Master-Slave communication.

bluetooth protocol master slave communication
Bluetooth Master Slave Communication

BlueTooth Protocol Piconet Communication:

When a group of two or more Bluetooth devices is sharing information together, they form a kind of ad-hoc, mini computer network called a piconet. In each network there is a maximum of 8 devices can be connected to form a piconet. Where one will be the master whereas the other 7 devices will work as slaves in this network.

bluetooth protocol piconet communication
BT Piconet Communication

BlueTooth Protocol scatternet Communication:

Whenever Two or more separate piconets are connecting to join up and share the information called a scatternet.

bluetooth protocol scatternet commnucation
BT Scatternet Communication

Bluetooth Addressing and Naming:

In BlueTooth Protocol, Every single Bluetooth device has a unique 48-bit address. This is usually a 12-digit hexadecimal value. The MSB 24-bit of the address is used to identify the organization unique identifier (OUI), which identifies the manufacturer (OEM). The LSB 24-bit of the address is used to identify the part of the address.

BlueTooth Protocol Connection Process:

To start communication or exchange of information between the two BlueTooth devices three multi-step processes.  These are 1. Inquiry, 2. Paging, 3. Connection.

(1) Inquiry: If two Bluetooth devices are in a remote network in the available range and are powered on the state with unknown to each other, then one must run an inquiry to try to discover the other. One device sends out the inquiry request, and any device listening for such a request will respond with its address, and possibly its name and other information.

(2) Paging: Paging is the process of forming a connection between two Bluetooth devices. Before starting the paging each device needs to know the address of the other by the inquiry process.

(3) Connection:  After a device has completed the paging process, it enters into the connection state. While the connected, a device can either be actively participating or it can be put into a low power sleep mode. Basically, after the successful connection between the two devices, they can stay indifferent 4-modes as Active mode, Sniff mode, Hold Mode, and park model.

(a) Active Mode:  This mode is a normal mode for a device where the device actively transmitting or receiving data.

(b) Sniff Mode: This is the power-saving mode, where the device is less active. It’ll sleep and only listen for transmissions at a set interval (e.g. every 100ms).

(c) Hold Mode:  The Hold mode is a temporary, power-saving mode where a device sleeps for a defined period of time and then returns back to active mode when that interval has passed. The master can command a slave device to the hold.

(d) Park Mode: The Park mode is the deepest of sleep modes. A master can command a slave to “park”, and that slave will become inactive until the master tells it to wake back up.

BlueTooth Protocol Bonding and Pairing:

In BlueTooth Protocol, when two of the Bluetooth devices share a special affinity for each other, they can be bonded together. Bonded devices automatically establish the connection whenever they both are close enough. When I start up my car, for example, the phone in my pocket immediately connects to the car’s Bluetooth system because they share a bond. Here no UI interactions are required.

In BlueTooth Protocol, bonds are created through the one-time process called pairing. When devices pair up, they share their addresses, names, and profiles, and usually, store them in NVM memory. They also share a common secret key, which allows them to bond whenever they’re together in the future.

The pairing usually requires an authentication process where a user must validate the connection between the devices.

BlueTooth Protocol Classes:

The Bluetooth classes are made according to their power consumption with the range between devices. There are 3 classes are:

Class NumberMax Output Power (dBm)Max Output Power (mW)Max Range
Class140 dBm100 mW100 m
Class24 dBm2.5 Mw10 m
Class30 dBm1 mW10 cm
BlueTooth Protocol Classes

What are the types of BlueTooth Protocol Profiles?

The way a device uses BlueTooth Protocol technology depends on its profile capabilities. The profiles provide standards that manufacturers follow to allow devices to use Bluetooth in an intended manner. For the Bluetooth low energy stack according to the Bluetooth 4.0, a special set of profiles applies. The Bluetooth profiles are additional protocols that build upon the basic Bluetooth standard to more clearly define what kind of data a Bluetooth module is transmitting. While the Bluetooth specifications define how the technology works, profiles define how it’s used.

Each profile specification contains information on the following topics:

  1. Dependencies on other formats.
  2. Suggested user interface formats.
  3. Specific parts of the Bluetooth protocol stack used by the profile. To perform its task, each profile uses particular options and parameters at each layer of the stack. This may include an outline of the required service record, if appropriate.

Types Of BlueTooth Protocol Profiles:

  1. Advanced Audio Distribution Profile (A2DP).
  2. Attribute Profile (ATT).
  3. Audio/Video Remote Control Profile (AVRCP).
  4. Basic Imaging Profile (BIP).
  5. Basic Printing Profile (BPP).
  6. Common ISDN Access Profile (CIP).
  7.  Cordless Telephony Profile (CTP).
  8.  Device ID Profile (DIP).
  9.  Dial-up Networking Profile (DUN).
  10.  Fax Profile (FAX).
  11.  File Transfer Profile (FTP).
  12.  Generic Audio/Video Distribution Profile (GAVDP).
  13.  Generic Access Profile (GAP).
  14. Generic Attribute Profile (GATT).
  15.  Generic Object Exchange Profile (GOEP).
  16.  Hard Copy Cable Replacement Profile (HCRP).
  17.  Health Device Profile (HDP).
  18.  Hands-Free Profile (HFP).
  19.  Human Interface Device Profile (HID).
  20.  Headset Profile (HSP).
  21.  Intercom Profile (ICP).
  22.  LAN Access Profile (LAP).
  23.  Mesh Profile (MESH).
  24.  Message Access Profile (MAP).
  25.  OBject EXchange (OBEX).
  26.  Object Push Profile (OPP).
  27.  Personal Area Networking Profile (PAN).
  28.  Phone Book Access Profile (PBAP, PBA).
  29.  Proximity Profile (PXP).
  30.  Serial Port Profile (SPP).
  31.  Service Discovery Application Profile (SDAP).
  32.  SIM Access Profile (SAP, SIM, rSAP).
  33.  Synchronization Profile (SYNCH).
  34.  Synchronization Markup Language Profile (SyncML).
  35.  Video Distribution Profile (VDP).
  36.  Wireless Application Protocol Bearer (WAPB).

Bluetooth Protocol Stack:

The Bluetooth protocol stack is split into two parts: a “controller stack” containing the timing critical radio interface, and a “host stack” dealing with high-level data. The controller stack is generally implemented in the low-cost silicon device containing the Bluetooth radio and a microprocessor. The host stack is generally implemented as part of an operating system, or as an installable package on top of the operating system. For integrated devices such as Bluetooth headsets, the host stack and controller stack can be run on the same microprocessor to reduce mass production costs; this is known as a hostless system.

BlueTooth Protocol Controller Stack

The BlueTooth Protocol Controller stack which connecting the timing critical radio interface, and a “host stack” dealing with high-level data. The controller stack is generally implemented in a low-cost silicon device containing the Bluetooth radio and a microprocessor. The host stack is generally implemented as part of an operating system, or as an installable package on top of an operating system. For integrated devices such as Bluetooth headsets, the host stack and controller stack can be run on the same microprocessor to reduce mass production costs; this is known as a hostless system.

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