How does bluetooth works ? | Bluetooth protocol stack/layers

Our life becomes easier and easier with the advancement of technology and blutooth is the one of them. Bluetooth technology is now available almost everywhere - in our laptops, mobile phones, watches, earphones and even in our cars. But lots of us don't know how bluetooth actually works.

Bluetooth works by using radio waves to send or receive data from another device wireless within a short distance. Bluetooth uses different types of protocol for different purposes.

What is Bluetooth ?

Bluetooth refers to the wireless technology which is used to exchange data between the devices like - mobile phones, watch,etc. over a short distance using radio waves. The radio waves signals operates within a frequency of 2.402 GHz to 2.480 GHz which falls in the category of industrial, scientific and medical radio band.

How does Bluetooth works ?

Bluetooth technology works by dividing the transmitted data into a packets and then transfer each packets using the one of the 79 bluetooth channel using radio waves. Bluetooth uses a technique called Frequency-hopping spread spectrum, under which bluetooth performs 1600 hops per second to avoid crowded frequency in a hopping sequence.

Bluetooth adapter is responsible for sending and receiving the data over radio waves. Bluetooth adapter can be of some particular range and noticed the another adapter if it is present in that range. If two bluetooth adapter are able to found each other, then they are able to exchange data. When two bluetooth device are connected to each other, it means they are sharing common frequency.

Master / slave architecture

Network of devices connected to each other using bluetooth devices is called piconet. Piconet can range from minimum 2 to maximum 8 devices - one is the master and upto seven are slaves. Master can communicate with his slaves within a piconet. Master governs the slaves and slave listen to the master.

Bluetooth protocol stack / layers

Radio layer

• Deals with radio transmission and modulation.
• Moves data from master to slave and vice-versa
• Uses GFSK (Gaussian frequency shift key) method to convert binary data to signal.

Baseband layer

• Enable physical connection between bluetooth devices.
• Control frequency hopping.
• Control synchronization.

Link manager protocol layer (LMP)

• Establish link between the devices.
• Handle authentication and encryption.
• Management of power consumption.

Logical link control and adaption protocol layer (L2CAP)

• Situated over a baseband layer and beside link manager protocol.
• Multiplexing - It supports multiple protocols like :- SDP, RF comm, etc.
• Segmentation :- division of data into packets before transmission.

Host controller interface (HCI)

• Provides command interface for the link manager and controller.
• Discover other bluetooth devices that are in range.

Service discovery protocol

• Discover services offered by other bluetooth devices.

Radio frequency communications (RFCOMM)

• Serial port emulation.
• Emulates RS-232 control and data signal over a baseband layer.

Telephony control protocol

• Defines call control signalling for the establishment of voice and data calls between the bluetooth devices.

Audio / video control transport protocol (AV/C)

• Music control buttons uses this protocol to control the playing music.

OBEX (object exchange)

• Facilitates binary transfer between the bluetooth devices.

Classes of bluetooth

Range of the bluetooth depends upon the class of the bluetooth. There are 4 types of classes :-

1. Class 1 :- Maximum output power 100 mW with a range of 100 meters. Mainly used in industrial devices
2. Class 2 :- Maximum output power 2.5 mW with a range of 10 meters. Mainly used in mobile phones and related devices.
3. Class 3 :- Maximum output power 1 mW with a range of 1 meters.
4. Class 4 :- Maximum output power 0.5 mW with a range of 0.5 meters.

Applications uses bluetooth

• Uses in PC input and output devices like printer, mouse, keyboard.
• Uses in car to wireless control between phone and bluetooth compatible car stereo system.
• Use to unlock door, by communicating wirelessly between smartphone and smart lock.
• Uses to exchange multimedia data like - videos, music, images, contacts, etc.
• Uses for streaming music wirelessly using bluetooth headphone.

How does Bluetooth works in car ?

Bluetooth car stereo system works using short-range, low power radio waves signals to transmit data. All you have to do is to open your smartphone bluetooth and connects it with your car stereo system.

In order to minimize the interference from other wireless devices smartphone and car stereo system changes their frequency 1600 times per second. 

How does a Bluetooth headset works ?

Bluetooth devices works by using low power radio waves signals. These signals will operates within the frequency of 2.402 - 2.480 GHz and can travel the distance upto 10m. Bluetooth headset has a tiny bluetooth chip which contains hardware and software for making connectivity with the phone.

Bluetooth headsets are very convenient for conversation on mobile phones. In order to use headset with your mobile phone make sure you device is compatible with your mobile phone. You can connect it by switching on the bluetooth of both the devices.

Is Bluetooth safe for health ?

Yes (probably), it is much safer than smartphone. Maximum power output of bluetooth is 100 mW, which is much much lower the that is phones. If you use bluetooth headphones to receive the call, it is less risky than that of receiving the call directly from phone.

Is bluetooth secure ?

Bluetooth is much secure as it uses a technology called frequency hopping. Under which, it changes it frequency 1600 times per second. If the hacker wants to hack it, he must need to know these frequency.

You can also turn off the bluetooth discover device mode So that no other devices can see you.

How data send between two Bluetooth devices ?

Data tranfer over the bluetooth using the radio waves signals. Two devices are able to connects with each other when they are sharing common frequency with each other.

How Bluetooth pairing works ?

• In order to connect 2 or more devices,keep the devices within the bluetooth range and open the bluetooth of all the devices. Let say, device A and device B.
• Set one of the device (device A) in discoverable mode from the bluetooth settings.
• In device B, see the list of discovered devices and select device A from the list.
• Then, enter a password when device B prompt you to set the password. 
• Then, enter the same password in device A, when ask.
• If the password is correct, connection established between the devices.

Advantages of Bluetooth

• Low power consumption
• No radio interference from other wireless devices.
• Available at very cheap price.

History of Bluetooth

Bluetooth technology was named after a Danish king, King Harald Blatand. His last name "Blatand" means "Bluetooth" in English. He was known for uniting Denmark and Norway in one nation, just as bluetooth technology unites two devices.

Bluetooth technology was invented by Swedish telecommunications company "Ericsson" to find the alternative of cable for communication between the devices. In may 1998, the bluetooth special interest group (SIG) was launched with companies Ericsson, Intel, Nokia, IBM, and Toshiba which published first consumers bluetooth device (hand free mobile headset) in the year 1999.

Evolution of Bluetooth

Bluetooth has evolved through version - 1.0, 1.1, 1.2, 2.0, 2.1, 3.0, 4.0, 4.1, 4.2, 5.0, 5.1 and currently at version 5.2.

Bluetooth version 2.0 + EDR 

• Enhance data rata (EDR) for transferring data faster. Bit rate of EDR is maximum 3 Mbit/s. 
• Reduction in power consumption.

Bluetooth  Version 2.1 + EDR 

• Released in year 2007.
• Improves pairing system.
• Enhanced security.

Bluetooth Version 3.0+ HS

• Released in year 2009.
• High speed (HS) data tranfer at 24 Mbits/s.
• Enhanced power control feature.
• Uses Wi-Fi radio.

Bluetooth Version 4.0

• Released in year 2010.
• Improves connectivity and range.
• Introduction of low energy protocol.

Bluetooth Version 4.1

• Released in year 2013.
• Better device power management, by pairing that allow automatic power up and down.
• Allow devices to acts as both hub and end points simultaneously so peripherals can communicate independently.

Bluetooth Version 4.2

• Released in year 2014.
• Increase speed and privacy.
• Increases the length of data packets.
• Enhanced security feature.

Bluetooth Version 5.0

• Released in the year 2016.
• Twice the speed of data transfer.
• Improvisation of long-range transfer
• Increases capacity.

Bluetooth Version 5.1

• Released in the year 2019.
• You can see the direction of your connected devices.
• Enhance advertising feature.

Bluetooth Version 5.2

• Released in the year 2020.
• Enhanced attribute protocol 
• LE Isochronous Channels
• LE power control - consumes less power with the help of dynamic power management to connects the devices.

Bluetooth Vs wi-fi

1. Bluetooth operates at a frequency of 2.4 GHz, while wi-fi operates at a frequency of 2.4 GHz, 3.6 GHz and 5 GHz.
2. Cost of bluetooth is low as compared to wi-fi.
3. Wi-fi can transfer data faster than bluetooth.
4. Consumption of power in bluetooth is less as compared to wi-fi.
5. Bluetooth is mainly used in speakers, mouse, keyboard, headphones, mobile, etc. While, wi-fi is mainly used in laptops, smartphones, TV, etc.
6. Bluetooth bandwidth is low as compared to wi-fi.

Conclusion

I hope you like this article, and now you know what is bluetooth, how does it works, bluetooth protocol stack, advantages, applications, history and evolution, how does bluetooth works in car , how bluetooth headset works and much more.