What is Bluetooth : Architecture & Its Working

Well-established technology like Bluetooth is used to provide wireless connectivity from wireless headphones to mobile phones, laptops & mice of the wireless computer to a lot of other devices which need a short-range of connectivity. This technology has developed & expanded drastically to provide not only the fixed short-range audio streaming in the applications of M2M communications and mesh connectivity of IoT. This technology provides better flexibility, very fast speed & far more capability. This article discusses an overview of Bluetooth.

What is Bluetooth Technology?

Bluetooth technology is a high-speed low powered wireless technology link that is designed to connect phones or other portable equipment together. It is a specification (IEEE 802.15.1) for the use of low-power radio communications to link phones, computers, and other network devices over short distances without wires. Wireless signals transmitted with Bluetooth cover short distances, typically up to 30 feet (10 meters).

It is achieved by embedded low-cost transceivers into the devices. It supports the frequency band of 2.45GHz and can support upto 721KBps along with three voice channels. This frequency band has been set aside by international agreement for the use of industrial, scientific, and medical devices (ISM).rd-compatible with 1.0 devices.

It can connect up to “eight devices” simultaneously and each device offers a unique 48-bit address from the IEEE 802 standard with the connections being made a point to point or multipoint.

History Of Bluetooth

Bluetooth wireless technology was named after a Danish Viking and King, Harald  Blatand; his last name means “Bluetooth” in English. He is credited with uniting Denmark and Norway, just as Bluetooth wireless technology is credited with uniting two disparate devices.

The Bluetooth technology emerged from the task undertaken by Ericsson Mobile Communications in 1994 to find an alternative to the use of cables for communication between mobile phones and other devices. In 1998, the companies Ericsson, IBM, Nokia, and Toshiba formed the Bluetooth Special Interest Group (SIG) which published the 1st version in 1999.


The first version was 1.2 standard with a data rate speed of 1Mbps. The second version was 2.0+EDR with a data rate speed of 3Mbps. The third was 3.0+HS with a speed of 24 Mbps. The latest version is 4.0.


Generally, the devices which are connected through Bluetooth are very secure from hacking. As they work with different frequencies & the devices which jump between these frequencies were 100s of times for every second which is called the “frequency-hopping spread spectrum”.

This device is frequently used for connecting mobile devices otherwise fixed devices. But it is also working to link a printer otherwise mouse toward a computer. As Bluetooth & Wi-Fi are frequently complementary, so they work at the same time & provides the same connectivity, so you cannot find out which hardware is connected. Most tablets, computers, smartphones simply permit connecting with one device that is Bluetooth enabled at a time.

How Bluetooth Works?

Bluetooth Network consists of a Personal Area Network or a piconet which contains a minimum of 2 to a maximum of 8 BlueTooth peer devices- Usually a single master and upto 7 slaves. A master is a device that initiates communication with other devices. The master device governs the communications link and traffic between itself and the slave devices associated with it. A slave device is a device that responds to the master device. Slave devices are required to synchronize they’re transmit/receive timing with that of the masters.

In addition, transmissions by slave devices are governed by the master device (i.e., the master device dictates when a slave device may transmit). Specifically, a slave may only begin its transmissions in a time slot immediately following the time slot in which it was addressed by the master, or in a time slot explicitly reserved for use by the slave device.

The frequency hopping sequence is defined by the Bluetooth device address (BD_ADDR) of the master device.  The master device first sends a radio signal asking for a response from the particular slave devices within the range of addresses. The slaves respond and synchronize their hop frequency as well as a clock with that of the master device.

Scatternets are created when a device becomes an active member of more than one piconet. Essentially, the adjoining device shares its time slots among the different piconets.

Bluetooth Architecture

The Bluetooth architecture uses two networks like Piconet and Scatternet

Piconet Network

Piconet is one kind of wireless network that includes one main node namely the master node as well as seven energetic secondary nodes are known as slave nodes. So, we can declare that there are eight active nodes totally which are arranged at a10 meters distance. The message between these two nodes can be done one-to-one otherwise one-to-many.

Communication can be possible only among the master and slave but the communication like Slave-slave cannot be possible. It also includes 255 parked nodes which are known as secondary nodes. These cannot communicate until it gets altered to the active condition.

Scatternet Network

The formation of the Scatternet Network can be done through various piconets. On one piconet, a slave is present which acts as a master otherwise it can be called primary within other piconets. So, this type of node gets a message from the master within one piconet & transmits the message toward its slave in another piconet wherever it works like a slave. So, this kind of node is called a bridge-node. In two piconets, a station cannot be master.

Types of Bluetooth

This technology eliminates the necessity of wires and cables. At present, this technology has seen a fast growth of Bluetooth-enabled devices.


The most commonly known device is the Bluetooth headset. Generally, a headset allows a person to make as well as receive calls through a mobile phone without using your hands otherwise wires. These headsets are prepared with voice recognition, thus one can dial & talk without utilizing a mobile handset.

Stereo Headset

The function of a  stereo headset is similar to a normal headset without using wires. The connection of a stereo headset can be done to any Bluetooth-enabled device like the music player. So, it permits the user to hear the music in a short range of your music player device. This headset also supports mobile phones.

Bluetooth System In-Car

An in-car Bluetooth system connects the mobile phone to the sound system in your vehicle. So, you can make & receive phone calls through the speaker system without using a mobile device.


A printer with Bluetooth enabled can get files like pictures and text documents from any device that is equipped with a blue tooth like a PDA or laptop & print the data without using wires. This device must be connected to the printer for the purpose of printing to work properly.


A webcam enabled by Bluetooth mainly works as a usual webcam without the requirement of wires. The wireless capabilities add mobility to the device, unlike traditional webcams, which remain docked onto or near the computer.

GPS Device

A Bluetooth-enabled GPS device is an essential device as compared to normal GPS because it permits you to converse through the device with voice. Once the device is communicated through voice then the device will find the address and also provide the directions over the display using voice command.


A Bluetooth-enabled keyboard mainly works like a normal keyboard, without using wires to connect the device to a PC. This keyboard also functions through particular smartphone devices.


The Bluetooth specifications include the following.

Bluetooth Specification
Bluetooth Specification
  • Core Specifications: It defines the Bluetooth protocol stack and the requirements for testing and qualification of Bluetooth-based products.
  • The Profiles Specification:  It defines usage models that provide detailed information about how to use the Bluetooth protocol for various types of applications.

 The core specifications of Bluetooth consists of 5 layers

  • Radio: Radio specifies the requirements for radio transmission – including frequency, modulation, and power characteristics – for a Bluetooth transceiver.
  • Baseband Layer: It defines physical and logical channels and link types (voice or data); specifies various packet formats, transmit and receive timing, channel control, and the mechanism for frequency hopping (hop selection) and device addressing.It specifies point to point or point to multipoint links. The length of a packet can range from 68 bits (shortened access code) to a maximum of 3071 bits.
  • LMP- Link Manager Protocol (LMP): It defines the procedures for link setup and ongoing link management.
  • Logical Link Control and Adaptation Protocol (L2CAP): It is responsible for adapting upper-layer protocols to the baseband layer.
  • Service Discovery Protocol (SDP): – Allows a Bluetooth device to query other Bluetooth devices for device information, services provided, and the characteristics of those services.

The 1st three layers comprise the Bluetooth module whereas the last two layers make up the host. The interfacing between these two logical groups is called Host Controller Interface.

How Secure Bluetooth Is?

This technology is considered as much secure wireless technology once we used safety measures. Bluetooth-enabled devices also move radio frequencies frequently when connected paired to prevent an easy attack. These devices offer different settings to allow the user for controlling the limit of Bluetooth connections. The security level of a device for a “trusting” this device limits the connections to simply that exact device.

By using the settings of service-level, you can also limit the types of activities allowed by your device to connect in while on a Bluetooth connection. In any wireless technology, there is always some safety risk involved. Hackers have planned different malicious attacks that utilize Bluetooth networking.
For instance, bluesnarfing refers to a hacker gaining official access to data over a device through Bluetooth; “blue bugging” is once an attacker receives from your mobile & all the functions.

Bluetooth Versions & Its Specifications

The different versions as well as their specifications of Bluetooth mainly include the following.

  • For v1.0 to v1.08 Version: Compulsory Bluetooth hardware device & address
  • For  v1.1 Version: IEEE standard 802.15.1-2002
  • For v1.2 Version: Quicker connection
  • For v2.0+EDR Version: Enhanced data rate
  • For v2.1 Version: Safe simple pairing
  • For v3.0 Version: High-speed data transfer
  • For v4.0 Version: Low energy utilization used in apple I – phone 4s

How Bluetooth Operates?

These devices should connect with each other for data exchange in a safe way with encryption. Once the Bluetooth device approaches a range of another device then an electronic conversation can be occurred to decide whether they believe each other or not, so that data can be shared. Here electronic conversion can be done wirelessly without operating a device.

The different peripherals like smartwatches, activity trackers have connected toward similar essential devices like smartphones from a Piconet to a PAN (personal-area network) that may fill a whole building or may include a distance, not above that among the smartphone within your pocket & the smartwatch on your wrist.

Connect with a SmartPhone

The connection of a headset with a smartphone can be done based on the following steps.

  • We need to check the Bluetooth whether that is completely charged or not, switch ON & connect with the phone you wish to connect.
  • Switch ON the phone and search for the Bluetooth feature generally found beneath Settings.
  • Turn ON Bluetooth
  • Once the Bluetooth feature is turned on, the smartphone transmits a signal & begins scanning of other Bluetooth allowed devices.
  • Once the smartphone discovers the headset, then the headset will appear on the devices list. In some situations, you will be requested to connect the devices by providing a PIN number that should appear through your headset.
  • Once both the devices are connected, then automatically all your phone calls will connect to your headset until it is activated. So the pairing process cannot be repeated once again.

Tips for Troubleshooting

Troubleshooting tips for Bluetooth mainly include the following.

  • Switch off everything and do again the pairing procedure.
  • Verify the batteries within your headphone & check whether they are charged completely or not
  • Verify that your headset & phone are well-matched.
  • A Bluetooth-enabled device produces low-power radio transmission signals that can transmit up to 10 meters approximately. However, the distance can change based on the headset. Make sure the range once before you purchase.
    • If you get any issues while connecting your device, check with the manufacturers.


The advantages of Bluetooth include the following.

  • It removes the problem of radio interference by using a technique called Speed Frequency Hopping.  This technique utilizes 79 channels of the particular frequency band, with each device accessing the channel for only 625 microseconds, i.e. the device must toggle between transmitting and receiving data from one-time slot to another.
  • This implies the transmitters change frequencies 1,600 times every second, meaning that more devices can make full use of a limited slice of the radio spectrum. This ensures that the interference won’t take place as each transmitter will be on different frequencies.
  • The power consumption of the chip (consisting of a transceiver) is low, at about 0.3mW, which makes it possible for the least utilization of battery life.
  • It guarantees security at the bit level. The authentication is controlled using a 128bit key.
  • It is possible to use Bluetooth for both transferring data and verbal communication as Bluetooth can support data channels of up to 3 similar voice channels.
  • It overcomes the constraints of the line of sight and one-to-one communication as in another mode of wireless communications like infrared.


The applications of Bluetooth include the following.

Bluetooth Technology
Bluetooth Technology

Cordless Desktop: All (or most) of the peripheral devices (e.g., mouse, keyboard, printer, speakers, etc.) are connected to the PC cordlessly.

Ultimate headset: It can be used to allow one headset to be used with myriad devices, including telephones, portable computers, stereos, etc.

Automatic Synchronization: This usage model makes use of the hidden computing paradigm, which focuses on applications in which devices automatically carry out certain tasks on behalf of the user without user intervention or awareness.

Multimedia Transfer:- Exchanging multimedia data like songs, videos, pictures can be transferred among devices using Bluetooth.

Thus, this is all about an overview of Bluetooth technology which covers working, types, history, architecture, specifications, advantages & its applications. Here is a question for you, what are different wireless technologies available in the market?

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