What is Bluetooth? : Understanding Bluetooth at a Glance

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Bluetooth

The History of Bluetooth

Bluetooth technology initially began to be developed in 1994 by Ericsson, a communications company in Sweden. The purpose of developing this technology was to unify communication standards between various wireless devices to enable mutual connectivity. Accordingly, companies like Intel, Nokia, and IBM came together to embark on the development for the standardization and commercialization of the technology.

Harald 1st(Haraldr blátönn Gormsson)
Harald 1st(Haraldr blátönn Gormsson)

The need for an official name for this technology arose around 1998, and it was then that Intel researcher Jim Kardach proposed the name ‘Bluetooth’. This proposed name was derived from the nickname of Harald 1st (Haraldr blátönn Gormsson), who is known for uniting Denmark and parts of Norway in the 10th century.

There are various hypotheses about the origin of the nickname ‘Bluetooth’, but the most widely accepted story is that Harald 1st had a fondness for blueberries, causing his teeth to turn blue. This nickname, symbolically representing the ‘integration’ of various devices and communication standards, was considered appropriately fitting for the name of Bluetooth technology.

At the time of proposing this name, Jim Kardach was reading a novel about Vikings called ‘The Long Ships,’ and it is said that this novel influenced the suggestion of the name. His idea symbolically reflected the original purpose of this technology, integrating communication standards through collaboration with various companies.

Ultimately, Bluetooth has become the standard for wireless communication technology by integrating connections and communications between devices, and the fact that the name of this technology came from the nickname of a Nordic king is a very interesting aspect.

Concept of Bluetooth

ISM-2.4GHz

Bluetooth is a technology that enables wireless communication between various devices. This technology utilizes the ISM (Industrial, Scientific, and Medical) band, enabling short-range communication between individuals. It was developed for transmitting data between small personal wireless devices and is being utilized in various aspects of daily life.

How it Works

Bluetooth operates using the Frequency-Hopping Spread Spectrum (FHSS) technology. This allows multiple devices to share the same frequency band, minimizing the impact of interference. Devices change these frequency channels very rapidly, enabling multiple devices to communicate efficiently in the same space. This method prevents channel interference as each device uses different channels hundreds of times per second.

Frequency and Channel

Bluetooth technology uses the 2.4GHz ISM (Industrial, Scientific, and Medical) band. This frequency band is an area that can be used without a license worldwide and is divided into 79 channels. Each channel is arranged at 1MHz intervals, and devices communicate using these channels. This frequency-hopping mechanism allows Bluetooth devices to maintain high communication efficiency and reliability.

Pairing and Security

Bluetooth-paring

Before initiating communication between Bluetooth devices, they perform a process called “pairing,” which involves mutual authentication and the exchange of security keys. This security key is used to ensure the confidentiality of data during communication sessions, aiding in the secure transmission of communications between Bluetooth devices. This pairing process establishes a trustworthy connection between devices and secures wireless communication.

Protocol Stack

Profiles

The protocol stack of Bluetooth is composed of several layers, with each layer performing different roles. The LMP (Link Management Protocol) establishes and manages the physical link, and the L2CAP (Logical Link Control and Adaptation Protocol) frames the data and manages the Quality of Service (QoS). Additionally, the SDP (Service Discovery Protocol) assists devices in discovering each other’s services. These diverse protocols interact to enable Bluetooth communication.

Profile and Functionality

One of the pivotal concepts in Bluetooth technology is the ‘Profile’. A profile defines how two Bluetooth devices interact with each other and what functionalities can be utilized. These profiles are distinguished based on the purpose and functionality of communication.

  • HSP (Headset Profile): HSP is a fundamental profile used for Bluetooth headsets. This profile supports audio and microphone functionality, allowing users to make, receive, and end calls. HSP transmits voice via the Sco (Synchronous Connection-Oriented) channel. Generally, it offers features like receiving and making calls and adjusting volume.
  • HFP (Hands-Free Profile): HFP is a profile defining hands-free call functionality. It offers more advanced features compared to HSP and is primarily used in car hands-free systems and premium headsets. Through this, users can use car stereo, speakers, etc., for calls. Also, calls can be received or rejected through the vehicle’s control buttons.
  • HID (Human Interface Device Profile): The HID profile enables communication between input devices like keyboards, mice, gamepads, etc., and Bluetooth. Utilizing this profile allows wireless command transmissions between devices. This profile enables users to connect various input devices to desktops or laptops and generally uses low power.
  • AVRCP (Audio Video Remote Control Profile): AVRCP allows users to remotely control audio or video devices. This profile enables play, pause, skip, and volume adjustment functionalities to be controlled via Bluetooth devices. It’s used alongside the A2DP profile, offering high-quality audio streaming as well as remote control functionality.
  • A2DP (Advanced Audio Distribution Profile): A2DP enables advanced audio streaming capabilities. Using this profile, stereo audio can be transmitted wirelessly. A2DP is typically used in most Bluetooth speakers and headphones, usually providing high audio quality. This profile supports various audio codecs like SBC, AAC, aptX, ensuring compatibility with a range of audio formats.

Codec and Data Transmission

Bluetooth-Codec-Latency

Audio transmission via Bluetooth primarily occurs in a compressed form. Since CD-quality music has a high bitrate of 1400Kbps, it can’t be transmitted as-is due to Bluetooth’s bandwidth limitations. Codecs are technologies that compress and then restore audio data, enabling high-quality audio transmission within the limited bandwidth of Bluetooth. Therefore, music is compressed and transmitted through a codec, and the receiver decompresses and plays it.

1. SBC (Sub Band Codec)

  • Type: SBC is the standard audio codec of Bluetooth.
  • Features:
    • Bitrate: Up to 345 kbps
    • Audio Quality: Maximum 48 kHz, 16 bit
    • Latency: Approximately between 100ms~200ms.
  • Pros and Cons:
    • Advantage: It has good universality and compatibility.
    • Disadvantage: It may have lower audio quality compared to advanced codecs.

2. AAC (Advanced Audio Codec)

  • Type: AAC is an audio codec boasting high efficiency and quality. It’s the general AAC codec applied in the Bluetooth format, providing similar or superior sound quality to SBC or aptX.
  • Features:
    • Bitrate and Sampling Rate: Typically used at 16 bit 48kHz or below.
    • Power Consumption: Relatively high.
  • Pros and Cons:
    • Advantage: It provides excellent audio quality.
    • Disadvantage: It has relatively high power consumption.

3. aptX

  • Type: An audio codec developed by Qualcomm.
  • Features:
    • Latency: aptX offers low latency and superior audio quality compared to SBC.
    • Power Efficiency: It consumes less power compared to SBC.
    • Usage Example: Sennheiser’s HD250BT headphones offer 25 hours of playback time through the aptX codec.

4. aptX HD

  • Type: This is the high-resolution version of aptX.
  • Features:
    • Audio Quality: Operates at 24 bit 48kHz, allowing for lossless transmission of high-resolution audio.

5. aptX LL (Low Latency)

  • Type: This is the low-latency version of aptX.
  • Features:
    • Latency: This codec reduces the audio delay time to a maximum of 40ms.

6. aptX Adaptive

  • Type: aptX Adaptive dynamically adjusts the bitrate according to the user’s environment and content.
  • Features:
    • This codec offers stable audio connection in various environments.

7. aptX Live

  • Type: This codec is designed for real-time audio applications.
  • Features:
    • Bit Depth and Sampling Rate: Operates at 24 bit 48kHz, guaranteeing 1.8ms of latency.
    • Usage Example: It is used in Sennheiser XSW-D and Rode Wireless GO.

Each of these diverse codecs can perform optimally depending on the specific environment, usage, and device compatibility. Users can choose and use an appropriate codec according to their needs and environment.

Bluetooth Class and Distance

Bluetooth-Class

The class of a Bluetooth device determines its output and communication range.

1. Class 1:

  • Maximum Output: 100mW
  • Maximum Transmission Distance: 100m
  • Usage: This class is primarily used in industrial devices and is not typically found in most mobile devices or general consumer devices. It can be used with an external antenna and consumes a lot of energy due to its high output.

2. Class 2:

  • Maximum Output: 2.5mW
  • Maximum Transmission Distance: 10m
  • Usage: This class is commonly used in most Bluetooth devices such as smartphones, headsets, and laptops. The actual communication distance may vary depending on the surrounding environment. It is generally suitable for consumer devices and is energy efficient.

3. Class 3:

  • Maximum Output: 1.0mW
  • Maximum Transmission Distance: 1m
  • Usage: This class is used in specific devices that require communication over very limited distances. It consumes very little energy, offering the advantage of extended battery life.

4. Class 4:

  • Maximum Output: 0.5mW
  • Maximum Transmission Distance: 50cm
  • Usage: This class is utilized in devices that need communication over extremely short distances.

Each class’s output and communication distance are theoretical maximums, and in a real-world environment, various factors like obstructions, radio interference, and the performance of the device’s antenna can influence them. For example, a Class 2 device may offer a distance of 10m indoors, but the actual communication distance can be much shorter in environments with many obstructions.

The Development of Bluetooth: Auracast

https://www.bluetooth.com/auracast/

In June 2022, Bluetooth v5.2 was announced, introducing a new audio system called Auracast. This technology enables audio to be transmitted simultaneously from one Bluetooth source device to multiple Bluetooth receiving devices. As a result, multiple users can share one audio source. For example, it became possible to stream music from one smartphone to several headphones or speakers.

Use Cases

Bluetooth technology is demonstrating a variety of use cases. It can be used for wireless earphones while exercising, or for hands-free calls while driving a car. Additionally, it’s utilized to control smart home devices, in health tracking, and even as game controllers, among other fields.