Bluetooth Technology Insights – Basic Functionality

By Ravi
Jul 20th, 2012

Some days ago i heard about “Zigbee” from one of my friends. When I was going through Zigbee, I had a strong feeling that IdleBrains readers first should know about “Bluetooth“. Following the same need, Today we have brought basic insights of Bluetooth technology for you.


Bluetooth Logo

In this smartphone era, almost everybody has heard the term “Bluetooth“. I also had some questions when i heard the term Bluetooth, and they kept on increasing as i knew more about it. Let’s find out if we had common questions ?


First thought : What exactly Bluetooth is ?

Bluetooth is a wireless communication standard for exchanging data over short ranges between fixed or mobile devices, by establishing a secure personal area network. No wires are needed, battery life will be almost same and it’s automatic too.

Suppose you have two devices and you want to transfer some song from one to the other, you can use “Bluetooth“. As it’s necessary for every communication to follow a particular set of rules; similarly if we want to use “Bluetooth technology” for the transfer, both devices need to follow the physical as well as protocol level standards defined by “Bluetooth standards“.

What are physical and protocol level standards ?

As we have talked above about physical and protocol level standards, let me explain it. Their meanings are the answers to following questions :

Physical : If we will use wires or it will be wireless ? If wireless, which frequency will be used for communication ? And similar requirements.
Protocol : How many bits will be sent at a time ? What each and every bit will mean and how the devices will confirm they are recieving the proper data or not ? How they will know if they should communicate with any device or not ? And similar requirements.

Bluetooth is a radio frequency standard. It is a network standard which works at both physical as well as protocol level.


Which frequency band Bluetooth operates in ? 

Bluetooth transmits data via low power radio waves. There is a frequency band which has been set aside for the use of ISM (Industrial, Scientific, Medical) devices. Bluetooth communicates on a frequency lying in the same ISM frequency band (Between 2.402 GHz and 2.480 GHz). There are lot of medical and industrial devices already which operate in same frequency band.

How Bluetooth avoids interference with other systems operating in same ISM band ?

This has been a critical part of the Bluetooth standard design. To avoid the interference, Bluetooth sends out very weak, low power (almost 1 milliwatt) signals.

Now the question arises that sending weak signal effects the performance or not?

Even with the low power, Bluetooth signals do not require a line of sight to work. Also low power of Bluetooth signal limits the range of Bluetooth device to 10 meters approx. Short range also cuts the chances of interference with other fixed devices in a way. So low power seems a bad term but in case of Bluetooth it helps the process.

What if many Bluetooth devices are withing 10 meter distance to each other, will they interfere with each other ? If not, why ?

No, Any Bluetooth device doesn’t interfere with other Bluetooth devices in range, whether it’s communicating with them or not. Bluetooth can communicate with 8 devices at a time but ofcourse, they should be within 10 meter range.

Bluetooth uses spread-spectrum frequency hoping which makes sure that no two devices are transmitting data on same frequency, hence avoiding the interference. In this technique, the transmitter uses 79 different frequencies, which are randomly chosen within the designated band and these frequencies change time to time on regular basis. Bluetooth device changes the transmitting frequency 1600 times in a second. This technique enables full use of the radio spectrum as well as minimizes the risk of interference with any other device (in range) transmitting on same frequency. Even if it happens, it lasts just for a fraction of second and doesn’e effect the process of both the devices.

Bluetooth can connect with 8 devices simultaneously, how any of these connection establishes ?

Whenever any Bluetooth device comes in range of other Bluetooth device, an automatic electronic conversation starts between them which determines whether one wants to send data to other or wants to perform any other task on other device. This conversation doesn’t require any user event, it’s fully automatic. Once this conversation is done, the devices form a personal area network (PAN). The devices in a PAN, hope their frequencies in sync to maintain the connection and perform the actions.

Actually while manufacturing of the devices, the manufacturer programs the device to communicate only with the devices having address within a fixed range. There are devices transmitting signals as well as devices which receive them, in any 10 meter area. Whenever any device receives any signal it checks whether it’s coming from a device within it’s allowed address range (remember electronic conversation !). If yes, then it creates a piconet (PAN) with it. Once the network is established, devices starts talking to each other. The devices in piconet change their frequencies randomly on regular basis (remember spread-spectrum frequency hoping !) but in sync with each other. If they receive signals from other devices having address outside the defined range, they ignore it as it is not from their network.

Withing 10 meter range only, there are so many piconets possible. Can they interfere with each other ?

Each of the piconet hope their frequencies and hence there are very minimum chances of interference with other piconet’s frequency. Even if it happens for a fraction of second, there are software checks added in devices to avoid any loss of data or connection due to it.

The connection is automatic as said above, so anybody can connect to my device and take control, how can i avoid such situations ? What if I don’t want to talk to some of the Bluetooth devices ( having address within the allowed address range for my device) ?

Security is a big concern specially when you are transferring data via radio frequencies. Bluetooth is no different. While sending your data through air, there are always chances that some device grabs it and interprets the signal to get the information. So the user needs to make sure while sending sensitive information via Bluetooth that it should not be interpretable by any unauthorised receipient.

The automatic nature of connection in Bluetooth saves our time and efforts but certainly on cost of security. Anybody can send you any file and that too without your information, can take control of your device, spread viruses and so on. To avoid this, Bluetooth offers different security modes. Device manufacturer uses any one of these modes based on the requirement of bluetooth enabled device. There are both service level and device level security measures provided to avoid unwanted connections by bluetooth enabled devices.

What are the possible/suggested security features we could/should use ?

  • We can set trusted users in our device, if device receives connection request from any other device, user needs to approve that.
  • Even after the above approval, user can send files to that device but if user receives any file, needs to approve that also.
  • Also we can put authentication for the use of Bluetooth service on any device so that only identified user with secure password can access Bluetooth or approve any file to be received.
  • Also user can set his device as “non-discoverable”, so that no other devices detect it’s presence.
  • We should enable approval for each connection as well as each received file, to avoid spreading of virus. Due to so many approvals, the viruses can not go very far.
  • There are several issues which get reported from market happening due to security loopholes in devices. For these, time to time firmwares are upgraded by manufacturers. If possible, we shall upgrade them as soon as possible.

Are there any Bluetooth specific security issues reported which we can take care about ?

Yes, there are several issues as Bluejacking, Bluebugging and many more, which are known as Bluetooth specific security problems.

Bluejacking is a process in which some user sends you name/contact card. Once you save it assuming it as some service message, the user is added in your contact list. Now all the messages from this user may get open without permission and can harm your device.

Bluebugging means accessing your device’s contact list remotely, taking control of it and then calls can be made with your device to any number, you will be charged and you won’t even know. It can involve you in fake call scenarios as well.

Car Whisperer software are is a reported threat, which access the audio from a car stereo or sends an audio file to it.

To avoid all such known problems, Bluetooth device manufacturers release firmware upgrades with added security measures for such problems.

After going through all the above information, i didn’t get any direct relation of the name “Bluetooth” with the process, is there any ?

No, you are absolutely right. There is no direct link of the name “Bluetooth” with the process. Bluetooth is the anglicised version of a by-name of a king of Denmark who united several tribes into a kingdom. The interpretation is that “Bluetooth” technology standard also unites several communication standards into one global communication standard.

Can we improve the range, speed and usability of “Bluetooth” ?

Yes, There are several Bluetooth profiles related to different aspects of Bluetooth standard. We can make compatible devices with some or more of these profiles. Also Bluetooth has several versions which are also steps towards better functionality.

What is “Zigbee” then ? Is it same as “Bluetooth” ?

This you will know in our upcoming articles, which will include Wi-Fi as well as Zigbee standard details. In coming weeks, we will get back to you with more information on other wireless communication standards.

We will bring to you details about “Bluetooth Profiles” also till then enjoy Bluetooth services but safely…For more technical articles please visit here.

About the Author

- Co-Founder of IdleBrains. Software engineer by profession, a poet at heart and tech writer by passion. Loves sweet music and cricket. Admirer and follower of Sachin Tendulkar. Follows his hobbies as “TheGhost”. Visit the poet here.

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