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How does Bluetooth work

Imagine that you someone near you is talking and you suddenly notice that no third person is there, rather he is talking on the wireless headphone. You might know that he is using Bluetooth technology which is built-in nowadays in all smartphones and other digital devices. If you ask randomly a group of people that how does Bluetooth works, or what is Bluetooth and how does it works, most of them may not answer you.

Although it is a technical field, generally speaking, we can understand it easily after which our use of this technology will be more productive. I am a professional Engineer, and today I am going to explain to you about Bluetooth technology, how Bluetooth technology work, when Bluetooth was invented, How to use Bluetooth technology, advantages and disadvantages of Bluetooth technology

 Bluetooth definition

Bluetooth is a wireless communication technology having small power, for a small distance and low data rate defined by IEEE 802.15.1 protocol. . Bluetooth wirelessly connects digital equipment’s in a master-slave mode from 2 to 8 units. Bluetooth connectivity requires both hardware and software. A small chip is required which is built in most of the cases which transmit and receive Bluetooth radio frequency signals in the range of 2.45 GHz.

In some cases, this chip can be installed separately which is available in the form of plug and play device as in the cases of wireless mouse connectivity to a computer. The frequency used by Bluetooth is set by an international agreement for industrial scientific and medical (ISM) devices. Generally, all digital devices are equipped with Bluetooth technology which includes smartphones, audio speakers, automobiles, medical devices, computers, keyboards, mouse, speakers, headphones, and even toothbrushes, to name just a few.

Now by going through a quick introduction and short definition we are now able to answer what is Bluetooth and how does it works if asked by anyone. Good, it means that now we can understand what blue tooth is and how does it work.

How to connect Bluetooth devices

Most people but not all who own smartphones know How to use Bluetooth. To elaborate on the use of Bluetooth devices let’s review how a Bluetooth device can be connected and data can be transmitted.

To switch on Bluetooth on a mobile phone and connect it with another device.

  1. Swipe down the mobile screen.
  2. Touch and hold the Bluetooth sign.
  3.  Tap pair new device.
  4. If you don’t find any new devices check in the available devices.
  5. Follow on-screen instructions

Once connected or paired with other Bluetooth device, then you can transfer any data between the devices.

Bluetooth specifications and versions

Bluetooth technology is evolved since its inception and a number of versions are available. The main difference in the updated versions is the data transmission speed, Security, and range. All newer versions are compatible with the previous versions.  The Bluetooth technology is based on IEEE 802.15.1 standard.

Bluetooth specifications:

 Bluetooth technology is a wireless transmission technology that uses the globally unlicensed but not unregulated Industrial scientific and medical ISM band which is in the range of 2.4 GHz.  The exact frequency spectrum used in Bluetooth is 2.402 to 2.480 GHZ and 2.4835 which also includes a guard band of 2 MHZ.  Frequency Hopping spread spectrum is used by Bluetooth technology.  There are 79 Bluetooth channels that are used for packet transmission by Bluetooth technology.  In the latest version, Adaptive Frequency-hopping spread spectrum (AFH) technology is used, in which there are 1600 hopes per second.

Bluetooth versions:

Bluetooth technology evolved with time. Initially, version 1 was introduced which was developed with time and updated versions were introduced.  Following is the list of Bluetooth versions along with their different features.

Bluetooth 1.0 and 1.0B

Bluetooth version 1.0 and 1.0B were introduced officially in 1999. These versions were having many problems specifically the ones which were related to interoperability issues faced by different device manufacturers.

One of the issue was Bluetooth mandatory device address transmission in connecting process ie while handshaking which was making anonymity impossible.

Bluetooth version 1.1

Bluetooth version 1.1 was introduced in 2001, in which most of the problems and errors of Bluetooth version 1.0 and Bluetooth version 1.0B were solved by the manufacturers in their devices for this newer version.  This new version i.e. Bluetooth version 1.1 was back compatible with earlier devices that is Bluetooth version 1.0 and Bluetooth Version 1.0B. Received signal strength indicator was first time introduced in this new version. One of the best features of this Bluetooth version 1.1 was authentication.

 In Bluetooth version 1.0B there was a problem of authentication mismatch by both connecting devices because of the conflict of slave and master device declaration issue. This problem was resolved by Bluetooth version 1.1.

There was another issue in Bluetooth version 1.0 and Bluetooth version 1.0B which was using frequencies in the range of 2.4 GHz.  Some countries like Japan, Spain, and France were using this band for military purposes. Therefore they were using a 23 hop spread spectrum instead of 79 hops. In Bluetooth version 1.1, this problem was resolved by requesting those countries to use the standard 79 hops spread spectrum technology.

Another issue in Bluetooth version 1.0 and Bluetooth version 1.0B was that for slave devices it was not possible to inform the master device about the number of slots for communication. This problem was solved in Bluetooth version 1.1 in which the slave can tell the master device about the number of slots for communication.

Bluetooth version 1.2

Bluetooth version 1.2 was introduced in 2003. Bluetooth version 1.2 was the first widely used protocol. Pairing speed, faster discovery, and Adaptive frequency spread spectrum were also introduced in Bluetooth version 1.2. Extended Synchronous Connections known as eSCO was also introduced in Bluetooth version 1.2, which is responsible for good voice quality due to retransmission of corrupted packets.

Bluetooth version 2

Bluetooth version 2 was introduced in 2005. This version of Bluetooth was Branded in the market as Bluetooth 2.0 + (Enhanced Data Rate) commonly known as EDR. Further, three-bit encoding was introduced which enhanced the data rate from 1 to 3 Mbps, however, the actual data rate in Bluetooth version 2 was   2.1 Mbps. This version was having the ability to use less power and interference handling capability. 

Bluetooth  version 2.1

Bluetooth version 2.1 was introduced in 2007. In this version, Secure Simple Pairing (SSP) was added to make the pairing and connection initiation process more secure.  Bluetooth version 2.1 also allow better filtering of devices before connection along with the name of the device, a list of services the device supports, as well as other information like the time of day, and pairing information to increase better QoS. External inquiry response is another feature which was introduced in Bluetooth version 2.1.

Bluetooth version 3

Bluetooth version 3 was introduced in 2009. The brand name marketed for this version was Bluetooth 3.0 + HS (High Speed). This version was having a unique feature, that it normally starts connection via Bluetooth, however, after connection establishment and authentication, it transmits data over Wi-Fi. This version provides a data rate of up to 24 Mbps.

Sniff sub rating is another feature introduced in Bluetooth version 3 which is good for low power consumption. With this feature computer input devices like mouse keyboard, power consumption is reduced.

Another feature that was introduced in this version was NFC. This is basically an automatic Bluetooth connection created between two devices when they are brought up together.

Bluetooth version 4

Bluetooth version 4 was introduced in 2010. This version was designed for low-power consumption and was branded as Bluetooth Smart. Main variations in Bluetooth version 4 included were Classic Bluetooth, Bluetooth high-speed data, and Bluetooth Low Energy consumption (BLE) protocols.

The Bluetooth names Wibree and Bluetooth ULP are commonly known as Ultra Low Power was replaced by BLE. Furthermore, later in 2011, signs of “Bluetooth Smart Ready” for hosts and “Bluetooth Smart” for sensors were introduced as the general-public face of BLE. Four further addendum were introduced in Bluetooth version 4, the last one in February 2013.

Bluetooth version 4.1

Bluetooth version 4.1 was introduced on December 4, 2013. This version was having better coexistence with LTE devices and efficient data exchange rate. This version was basically a software update and not a hardware one. These protocols also allow multiple roles of the same device at the same time ie Master and slave. A main new feature in Bluetooth version 4.1 was,  Mobile wireless service coexistence signaling, generalized interlaced scanning,  low duty cycle directed advertising and audio architecture update, etc.

Bluetooth version 4.2

Bluetooth version 4.2 was introduced in 2014. This version was basically designed for the Internet of Things (IoT). In Bluetooth version 4.2 the payload size in the Bluetooth packet was increased by 10x. This version was also supported the wireless personal area network (WPAN) version of IPv6  due to which it enabled billions of devices to have a unique IP address. The privacy of this version was also strong as compared to its predecessor’s. Bluetooth version 4.2 was also supporting Internet Protocol Support Profile (IPSP) version 6 which makes it ready for Bluetooth Smart things to support connected homes.

Furthermore, Older Bluetooth hardware was able to receive Bluetooth version 4.2 features such as Data Packet Length Extension and improved privacy by updating its firmware.

Bluetooth version  5

Bluetooth version  5 was introduced in 2016. This version was a more robust version with extended battery life for an extended time of use. The major breakthrough of this version was an extension in the transmission range from 50 to 200 meters which was a major demand of the Bluetooth user community. The smart devices to support Bluetooth 5 were the Galaxy S8 and iPhone 8 and X. Bluetooth version 5 also supports BLE that extends the data rate at the expense of speed or can enhance the speed at the expense of data rate.

Major improvements in Bluetooth version 5 were the Slot availability mask, LE long-range, and high duty cycle.

Bluetooth version 5.1

Bluetooth version 5.1 was introduced in January 2019. New features which were introduced in this version were the angle of arrival and angle of departure which are helpful for location services of devices. Further enhancements in Bluetooth version 5.1 slept clock accuracy, HCI support for debugging keys, and periodic advertising sync transfer.

Bluetooth version 5.2

Bluetooth version 5.2 was introduced in December 2019. Low energy radio (LE) was introduced specifically meant for low battery consumption in this version of Bluetooth.

Further features of Bluetooth version 5.2 are LE isochronous channels, LE power control, and Enhanced attribute protocol.

Advantages of Bluetooth

Like other technologies Bluetooth technology is not perfect, It is still evolving and further improvements are being made with time in this technology. Following are the main advantages of Bluetooth.

Simple setup: Bluetooth technology use is very simple. You can set up the connection between two devices very easily.

No interference: The Bluetooth technology avoids interference with other wireless devices as this technology is having a dedicated range of frequencies.

Power consumption: The power consumption of Bluetooth devices and data transfer is very low. Special attention has been made to this feature over time.

Easy up-gradation: Blue tooth devices are easily upgradeable specifically in the case of plug and play devices.

Good range: The range of Blue tooth devices is good as compared to top infrared devices.

Voice and data transfer: Bluetooth is generally used for voice and data transfer over short distances.

Low cost: The cost of Bluetooth devices is very low.

No line of sight communication: There is no need for a line of sight for Bluetooth devices. Thus obstacles cannot hinder the communication of Bluetooth devices. No line of sight hence can connect through any obstacles.

Free usage of Bluetooth: The data transfer using Bluetooth technology is free, unlike Wifi technology. You can transfer your pictures, data and other files through Bluetooth without any cost. Free to use if the device is installed with Bluetooth.

Compatibility:  there are no compatibility issues in Bluetooth devices generally. For example, a headset having Bluetooth can be connected with any device having Bluetooth like a phone, tablet, laptop or iPhone, etc.

Less hardware: The Bluetooth hardware is not bulky. In most cases, the Bluetooth hardware is built-in like in smartphones, iPhones, Tablets, and laptops. In some cases, if not supported then a small dongle can be used as a Bluetooth plug-and-play device which you have seen in Mouse and computer connectivity.

Disadvantages of Bluetooth Technology

Connection lost issues: The Bluetooth devices can lose connection more often when the requirements are not met even during an already established connection.

Low bandwidth: The bandwidth if Bluetooth technology is far less as compared to Wi-Fi.

Short-range: The communication range of Bluetooth technology is very much low as compared to other wireless technologies.

Security: There are security concerns regarding Bluetooth technology as compared to other Wireless technologies.

Security concerns of Bluetooth

Bluetooth is important to all of us when it comes to the connectivity of smartphones to smartphones, mouse and keyboards to computers, Our headsets to our phones, and our phones to our car. However, there exist some security risks related to Bluetooth. We must be aware of those security risks so that we can avoid them by taking the necessary steps in this regard.


 Bluetooth technology while using, we pair our device with another device to whom we want to connect. Sometimes we forgot to switch off our Bluetooth after use. It is now the time for a hacker to connect to our device through Bluetooth without knowledge and permission.  The hacker then steals data from our device. To avoid this type of misshape we need to switch off our Bluetooth after use.

Viruses and worms

Internet is full of viruses and malware. A small mistake and carelessness can make our data easily accessible to hackers. This happens when we download unverified software and apps from the internet which contain malware and versus.  This threat can be avoided by downloading software only from trusted websites.


Eavesdropping is another well-known loophole used by hackers to fetch your valuable data. In Eavesdropping, the hackers normally name their devices like the ones which you use in your office for printers and other well-known and common names. So when you want to pair your devices to another Bluetooth device, you sometimes make mistakes and you overlook the actual name and connect your device to the eavesdropper device mistakenly. This makes your data vulnerable and the hackers then copy your data or inject some viruses and malware into your device for hacking.

To protect yourself from Bluetooth eavesdropping, always cross-check the name of the device to whom you are connecting and pair the device to the one which you know well with correct spelling. Furthermore, always switch off your Bluetooth if you are not using it.

Denial of service

Another severe attack by the hacker through Bluetooth is the denial of service. A hacker once connected to your device through Bluetooth can hack your device by blocking your messages, deactivating your calling, and even can drain your battery. This type of attack is very serious and you can lose your data very easily if you are hit by such an attack.

Bluetooth headsets vulnerability

 This is another vulnerability you can face if you are frequently using Bluetooth for calls and not being cared for by switching off of your Bluetooth connection.  If your Bluetooth device is on, then hackers can pair their Bluetooth headsets and can listen to your conversations, your phone calls, and even your face-to-face conversation.

Frequently Asked Questions (FAQ)

What are the different Bluetooth versions?

Bluetooth’s first version i.e. Bluetooth version 1.1 was introduced in 2001 with basic functionalities. With time, Bluetooth evolved with up-gradation and new features and now Bluetooth 5.2 is in practice.

What is the latest Bluetooth version 2020?

Latest Bluetooth version is Bluetooth version 5.2.

Are all Bluetooth versions fully compatible?

Yes, all Bluetooth versions are fully compatible.

What Bluetooth version is on my PC?

You can check the version of Bluetooth on your PC or Laptop.

Go to device manager, by typing it in the search box of your taskbar.

Select the Bluetooth and expand it.

Select the advanced Tab and see for LMP (Link Manager Protocol). Check the LMP number online to know about the version of Bluetooth.

Select the arrow next to Bluetooth to expand it.

Select the Bluetooth radio listing (yours might simply be listed as a wireless device).

Select the Advanced tab, then look for the LMP (Link Manager Protocol) listing in the Firmware or Firmware version area. That number tells you what LMP version you have on your device.

What is the difference between 4.0 and 4.1 Bluetooth?

The main difference in Bluetooth 4.0, and Bluetooth 4.1 is the increase in packet data transfer rate from  20 bytes to 23 bytes which is a 15 % increase.

What’s the difference between Bluetooth 4 and 5?

The main difference between Bluetooth Version 4 and Bluetooth version 5 is speed. The new version Bluetooth version 5 is faster than Bluetooth 4, having  2Mbps, which is twice the speed of Bluetooth 4 about 1 Mbps. This is also one of the requirements of the Internet of things i.e. IoT. Further, the bandwidth of Bluetooth 5 is 5Mbps  as compared to  2.1 Mbps which is that of Bluetooth version 4.

Can Bluetooth 5 connect to Bluetooth 4?

Yes, all Bluetooth versions are back compatible.

Can I connect a Bluetooth 4.0 smartphone with a Bluetooth 4.1 headphones?

Yes,  all Bluetooth  versions are back compatible.

Is Bluetooth a security risk?

Bluetooth encryption and security is up to the mark. However, there is always a risk of hacking and precautions should be taken to avoid any such instance.

Can you get hacked through Bluetooth?

If you are careless and your Bluetooth is always On, then there is a risk of hacking. Hacker can hack your device, can crash it, can access your files etc.

Is it dangerous to have Bluetooth on all the time?

Yes, it is extremely dangerous, and hackers can connect you if your Bluetooth is always ON, It is recommended to switch off your Bluetooth connection if you are not using it.

Can someone connect to my Bluetooth without me knowing?

In most cases, you are supposed to allow someone to pair with your device. However, if your Bluetooth device is always On, then there is always a risk if your device is of the older version.

Can a computer or Laptop be hacked through Bluetooth?

A recent issue in Bluetooth security was uncovered. In this case, hackers access your computer or Laptop Bluetooth using Key Negotiation of Bluetooth (KNOB) in which your computer is forced to be on the lower side of encryption. This will make the hacker easily connect to your computer and can hack your data.

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