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What is Bluetooth Technology?
Bluetooth is short range, low power wireless technology standard use to transmit data between devices. It uses Ultra High Frequency (UHF) radio waves to create network and transmit data. Frequency range for Bluetooth is from 2.402 GHz to 2.480 GHz. Bluetooth is use to create personal area network (PAN) called as “Piconet“.
History of bluetooth
In 1989 Nils Rydbeck CTO at Ericsson Mobile in Sweden, started technology research with the aim to develop wireless headphone. Tord Wingren with two member Jaap Haartsen and Sven Mattisson were tasked to develop “short-link” radio technology. In 1997 Örjan Johansson become the project leader. In year 1997 head of IBM ThinkPad product R&D, Adalio Sanchez approached Nils Rydbeck to collaborate on integrating mobile phone in ThinkPad notebook.
At the time engineer were facing problem because of power consumption of ThinkPad notebook were high and to integrating mobile phone in ThinkPad notebook will affects battery life of ThinkPad notebook. This where Ericsson Mobile “short-link” technology comes in the picture. Both IBM and Ericsson Mobile agreed to integrate “short-link” technology in Ericsson’s mobile phones and IBM ThinkPad notebook.
Nils Rydbeck and Adalio Sanchez made this “short-link” technology an open industry stander this was done to capture maximum market share in their respective markets. Stephen Nachtsheim of Intel was recruited further Nokia and Toshiba were also recruited.
In 1996’s meeting Jim Kardach from Intel coined Bluetooth as a temporary code name. In May 1998 Bluetooth Special Interest Group was launched with 5 member: Ericsson, IBM, Intel, Nokia and Toshiba.
In 1999 first consumer Bluetooth was launched. At COMDEX hand-free mobile headset won “Best of show Technology Award”. Ericsson T36 was first Bluetooth mobile phone which was updated version of T39 model which went on sale in 2001. In October 2001 IBM launched their first Bluetooth enable notebook i.e. IBM ThinkPad A30
Bluetooth is name after tenth-century king Harald Bluetooth(King of Denmark and Norway) because he unites many Danish tribes into one single kingdom and Bluetooth does the same with devices, it connect them in one single network.
Working of bluetooth
Bluetooth works on the Master-Slave model, a network created bluetooth devices is known as piconet. Maximum 8 devices can be connected to form piconet i.e. 1 Master and 7 Slaves.
Bluetooth Device Address (BD_ADDR)
All bluetooth devices have their own 48 bits unique address known as BD_ADDR(Bluetooth Devices Address). Most of the manufacturer displays bluetooth device’s address in 12 digit hexadecimal format.
From 48 bits Most Significant 24 bits are used to represent Organizationally Unique Identifier (OUI) and Least Significant 24 bits are used to determine the unique address of bluetooth devices known as Lower Address Part (LAP).
Organizationally Unique Identifier (OUI) is divided into two parts.
- NAP (Non-significant Address Part) : Value of NAP is used in Frequency Hopping Synchronization frames. Its size is 2 bytes and it contains the first 16 bits of OUI.
- UAP (Upper Address Part) : Value of UAP is used for seeding in many Bluetooth specification algorithms. Its size is 1 bytes and it contains the remaining 8 bits of OUI.
Lower Address Part (LAP) : It is used to determine the unique address of bluetooth devices. Its size is 3 bytes. During transmission LAP value is part of access code which uniquely identifies the bluetooth device.
The Significant Address Part (SAP) of the Bluetooth Address is made by LAP and UAP.
In this bluetooth module BD_ADDR is mentioned as MAC NO. which is “00066642942C”. Here “000666” is value of Organizationally Unique Identifier (OUI) and “42942C” is unique ID of bluetooth module which is set by the vendor.
In mobile phones we can change the name of bluetooth more the two devices can share the same name, name can be upto 248 bytes long.
Bluetooth device have to follow certain steps to create connection with another bluetooth device. Following are the steps.
Inquiry: If both the devices are unknown to each other then two discover each other one device must send discover request and another will listen to this request and respond to it by sending address, name and other information
Paging (Connecting): In this step both the devices will form connection.
Connection: Once the paging process is complete then Connection step gets started. Here connected devices can participate in data transmission or it can be put into low power sleep mode.
Following are the modes:
- Active mode
- Sniff mode
- Hold mode
- Park mode
Active mode: This is regular connected mode, here device is active in data transmission process i.e. sending or receiving.
Sniff mode: This is power saving mode, here device is in sleep and only listen for transmission at set time interval. It is power saving mode.
Hold mode: This is also a power saving mode, here device will be in sleep and will get active after set time interval. Master can put slave device in hold mode.
Park mode: This is kind of ultra saving mode, here master can commands slave to switch in park mode and slave will remain in park mode till master commands it to switch in active mode.
Bonding and Pairing in bluetooth devices
When two devices share special empathy towards each other then they can be bounded together. All bonded devices can connect to each other directly when they are in range of each other. Bounding is done after pairing, during paring process both the bluetooth devices share their address, name, profile and other information like comman secret key. They store this information in system and use to connect with each other directly when ever they both are in range of each other.
Pairing process requires authentication where user must validate the connection between devices.
Authentication process varies from device to devices, e.g. if device is headphone then it require just a click to authenticate. But devices like mobile phone we have to use 6-digit numeric code.
In older version V2.0 and below authentication process requires entering of 4 digit number for pairing. Length of common secret code can be vary from 4-digit to 16 alphanumeric characters.
Data transfer speed of Bluetooth 5.0 is 2Mbps. Bluetooth device transmit data using low power radio waves. Frequency from 2.400 GHz to 2.483.5 GHz this frequency band has been set by international agreement for Industries, Science and Medical (ISM) use. Bluetooth communicates on 2.45 GHz, but there are many devices around us which uses same frequency band e.g. mobile phones, earphone, smartwatch, laptops, etc.
Why there is no interference during transmission?
Simple answer is “Frequency Hopping”. Bluetooth device transmit data using low power radio waves. Frequency from 2.400 GHz to 2.483.5 GHz this frequency band has been set by international agreement for Industries, Science and Medical (ISM) use. Bluetooth communicates on 2.45 GHz, but there are many devices around us which uses same frequency band e.g. mobile phones, earphone, smartwatch, laptops, etc.
Even if we have many devices is same radius they never interfere in each other transmission, because of one technique use by Bluetooth is “spread-spectrum frequency hopping”.
In this Bluetooth devices select 79 frequencies randomly, and during transmission, bluetooth devices will change its frequency from one to another between their respective 79 frequencies. It changes frequencies 1600 times in one second. It is rare for bluetooth devices to have same frequency on same time and even though two devices have same same frequency at same time then still it will be for short time frame.
We can connect upto 8 devices at one single time and transfer data between them.
We can create ad hoc Network with bluetooth. This network is known as “Piconet“.
- Bluetooth is use in IoT, to monitor and transmit data between sensor, controller and actuator. e.g. Smartwatch
- Bluetooth can also be use to create ad hoc network of different devices.
- It can also be use in real-time voice and data transmission.