Bluetooth

Bluetooth is an industry specification for wireless personal area networks (WPANs) created by Bluetooth Special Interest Group, Inc. that enables the transmission of voice and data between different devices over a radio frequency link in the 2.4 GHz ISM band.

Objectives

The main objectives to be achieved with this standard are:

• Facilitate communications between mobile equipment.
• Remove the cables and connectors between these.
• Providing the possibility of creating small wireless networks and facilitating data synchronization between personal equipment.

The devices that most frequently use this technology belong to the telecommunications and personal computing sectors, such as mice or computer mice, keyboards, mobile phones, laptops, personal computers, printers, wireless speakers, wireless or semi-wireless headphones, control levers (joystick type) or digital cameras.

Etymology and logo

Contrary to what it might seem, the name bluetooth does not have a technological origin. Nor does it correspond to an acronym or an abbreviation.

The name comes from the Danish and Norwegian king Harald Blåtand, whose English translation is Harald Bluetooth. The king is known for unifying the Danish tribes and converting them to Christianity.

In 1996, Intel developed a system that would allow mobile phones to communicate with computers and unify wireless communication. At the time, Jim Kardach, an engineer at Intel, was reading the historical novel The Long Ships, which recounted the exploits of King Harald Blåtand. Through the parallels between the two concepts, the name Bluetooth was established.

The Bluetooth logo combines the Hagall runes () and Berkana (), which corresponds to the initials of Harald Blåtand.

• Hagall: Runa depicting the letter H in futhark young and futhorc. The H variant in the runes of the old futhark would be the haglaz or dolaz call. It means hail.
• Berkana: Runa depicting the letters B or P in young futhark, and which is considered native to the letter B latina. It means birch.

Uses and applications

Bluetooth is the name given to the communications protocol specially designed for low consumption devices that require short transmission range and based on low cost transceivers.

Devices that incorporate this protocol can communicate with each other when they are within range. Communications are carried out by radio frequency so the devices do not have to be aligned and can even be in separate rooms if the transmission power is sufficient. These devices are classified as "Class 1", "Class 2", "Class 3" or "Class 4" in reference to its transmission power, the devices of a computer box being fully compatible.

In most cases, the effective coverage of a class 2 device is extended when connected to a class 1 transceiver. This is because of the higher sensitivity and transmit power of the class 1 device, it is In other words, the greater transmission power of the class 1 device allows the signal to reach the class 2 device with sufficient energy. On the other hand, the greater sensitivity of the class 1 device allows it to receive the signal from the other device despite being weaker.

Bluetooth-enabled devices can also be classified according to their channel capability:

Bluetooth profiles

To use Bluetooth, a device must implement one of the Bluetooth profiles. These define the use of the Bluetooth channel, as well as channeling to the device to be linked.

Application List

• Connection without cables via OBEX.
• Transfer of contacts, appointments and reminders between devices via OBEX.
• Replacement of traditional cable communication between GPS equipment and medical equipment.
• Remote controls (traditionally dominated by infrared).
• Send small advertising from advertisers to devices with Bluetooth. A business could send advertising to mobile phones whose Bluetooth (those who own it) was activated when passing by.
• The Sony PlayStation 3, PlayStation 4, Microsoft Xbox 360, Xbox One, Wii U and Nintendo Switch consoles incorporate Bluetooth, allowing them to use wireless controllers, although the original Wii U Gamepad connects to the console via Wi-Fi and Wii commands use infrared technology for pointer function.

Specifications and news

The Bluetooth utility was developed, as a cable replacement, in 1994 by Jaap Haartsen and Sven Mattisson, who were working for Ericsson in Lund, Sweden. The utility is based on wide spectrum frequency hopping technology. In its early days, Bluetooth technology could transmit data at a speed of 720 kbps, an incredible capacity for the 1990s, but one that today seems very limited. After more than two decades of improvements, different types of Bluetooth have come to boast speeds of up to 50Mbs. In addition, the connection range is another aspect that has improved a lot. Bluetooth has gone from working at distances of less than one meter to the more than 100 meters that can be reached today.

The features were published by the Bluetooth Special Interest Group (SIG). The SIG formally announced them on May 20, 1998. It was created by Ericsson, IBM, Intel, Toshiba, and Nokia, with many other companies joining later. Today it has a membership of more than 20,000 companies worldwide. All versions of the Bluetooth standards are designed for backwards compatibility, which allows the latest standard to cover all previous versions.

Bluetooth v1.0 and v1.kb

Versions 1.0 and 1.kb have had a lot of problems, and manufacturers had difficulties making their products interoperable. Versions 1.0 and 1.0k include in hardware the address of the Bluetooth device (BD_ADDR) in the transmission (anonymity is made impossible at the protocol level), which was a major setback for some services intended for use in Bluetooth environments.

Bluetooth v1.1 (2002)

• Ratified as IEEE 802.15.1-2002 standard.
• Many errors were corrected in specifications 1.0b.
• Added support for unencrypted channels.
• Signal indicator received (RSSI).

Bluetooth v1.2 (2003)

This version is compatible with USB 1.1 and the main improvements are the following:

• A faster connection and Discovery (detection of other bluetooth devices).
• Expanded spectrum adaptable rate balance (AFH or Adaptive Frequency-hopping In English), which improves resistance to radiofrequency interference, avoiding the use of full frequencies in the jump sequence.
• Increased transmission speed, in practice, than in v1.1, up to 721 kbit/s.
• Extended Synchronic Connections (ESCO), which improve the voice quality of audio links by allowing the retransmission of corrupt packages, and, optionally, can increase audio latency to provide better support for the transfer of simultaneous data.
• Host Controller Interface (HCI), with the support of three UART threads.
• Ratified as IEEE 802.15.1-2005 standard.
• It introduced flow control and L2CAP relay modes.

Bluetooth v2.0 + EDR (2004)

This version of the Core Bluetooth specification was released in 2004 and is backwards compatible with version 1.2. The main difference is in the introduction of an enhanced data rate (EDR: Enhanced Data Rate) to speed up data transfer. EDR's nominal rate is 3 Mbit/s, although the practical data rate is 2.1 Mbit/s. EDR uses a combination of Gaussian Frequency Shift Keying (GFSK).) and Phase Shift Keying (PSK) with two variants, π/4-DQPSK and 8DPSK. EDR can provide lower power consumption through a reduced duty cycle.

The specification is published as "Bluetooth v2.0 + EDR", which implies that EDR is an optional feature. Aside from EDR, there are other small enhancements to the 2.0 specification, and products may advertise Bluetooth v2.0 compliance without including the higher data rate. At least one commercial device is advertised as "no EDR Bluetooth v2.0" in its technical data sheet.

Bluetooth v2.1 + EDR (2007)

Version 2.1 of the Bluetooth Core + EDR specification is fully compatible with 1.2, and was adopted by the Bluetooth SIG (Bluetooth Special Interest Group) on July 26, 2007.

The headline feature of 2.1 is Secure Simple Pairing (SSP): the Bluetooth device pairing experience is improved, while increasing usage and security strength. For more details, see the link section below.

2.1 enables other enhancements, including "extensive research response" (EIR), which provides more information during the investigation procedure to allow better filtering of devices before connection, and smell subrating, which reduces power consumption in low power mode.

Bluetooth v3.0 + HS xxx (2009)

Version 3.0 + HS of the Core Bluetooth specification was approved by the Bluetooth SIG on April 21, 2009. Bluetooth 3.0+HS supports theoretical data transfer rates of up to 24 Mbit/s with each other, but not over the actual Bluetooth link. The native Bluetooth connection is used for negotiation and setup while high-speed data traffic is carried over an 802.11 link.

Its main novelty is AMP (Alternate MAC/PHY), the addition of 802.11 as a high-speed transport. Initially, two technologies were planned to be incorporated into AMP:. 802.11 and UWB, but finally UWB is not in the specification.

In the specification, the incorporation of high-speed transmission is not mandatory and therefore devices marked with "+ HS" They incorporate the 802.11 high-speed data transfer link. A Bluetooth 3.0 device, without the "+ HS" does not support high speed, but only supports a feature introduced in Bluetooth 3.0 + HS (or in CSA1).

Alternative MAC / PHY

Allows the use of MAC and PHY alternatives for the transport of Bluetooth profile data. The Bluetooth radio is being used for device discovery, initial connection and profile setup, however when large amounts of data need to be sent, the 802.11 MAC PHY (typically associated with Wi-Fi) is used to transport the data.. This means that the Bluetooth low energy mode is used when the system is idle, and the 802.11 radio when large amounts of data need to be sent.

Unconnected data Unicast

Service permits data to be sent without establishing an explicit L2CAP channel. It is designed for use in applications that require low latency between user action and data reconnection/transmission. This is only suitable for small amounts of data. Improved power control.

Updated power control function to remove open loop power control and also to clarify ambiguities in power control presented by new modulation schemes added for EDR. Enhanced power control removes ambiguities by specifying the behavior to be expected. This feature also adds closed-loop power control, ie RSSI filtering can start as the response is received. Also, a "go straight to full power" request has been entered. This is expected to address the issue of headset link loss typically seen when a user puts their phone in a pocket on the opposite side of the headset.

The High Speed (AMP) feature of Bluetooth version 3.0 is based on 802.11, but the AMP mechanism was designed to be used with other radios as well. Originally, it was intended for UWB, but the WiMedia Alliance, the body responsible for the flavor of UWB for Bluetooth, announced in March 2009 that it was disbanding. On March 16, 2009, the WiMedia Alliance announced that it would sign a technology transfer agreement for the WiMedia Ultra-Wideband (UWB) specifications. WiMedia has transferred all current and future specifications, including work on the future of high speed and optimization of power implementations, the Bluetooth Special Interest Group (SIG), the Wireless USB Promoter Group, and the USB Implementers Forum. After the successful completion of technology transfer, marketing and related administrative matters, the WiMedia Alliance will cease to operate.

In October 2009, the Bluetooth Special Interest Group discontinued development of UWB as part of the alternative MAC/PHY, Bluetooth 3.0 + HS solution. A small but significant number of former WiMedia members did not have and were not going to sign necessary agreements for the transfer of intellectual property. The Bluetooth SIG is now in the process of evaluating other options for its long-term action plan.

Bluetooth v4.0 (2010)

The Bluetooth SIG has completed the Bluetooth Core Specification at version 4.0, which includes the Bluetooth Classic, Bluetooth High Speed, and Bluetooth Low Energy protocols. High-speed bluetooth is based on Wi-Fi, and classic Bluetooth consists of pre-existing Bluetooth protocols. This version has been adopted on June 30, 2010. Bluetooth Low Energy (Bluetooth Low Energy or BLE) is a subset of Bluetooth v4.0 with a completely new protocol stack for rapidly developing simple links. As an alternative to the standard Bluetooth protocols that were introduced in Bluetooth v1.0 to v4.0 it is targeted at very low power applications powered by a button cell. Chip designs allow for two types of implementation, dual-mode, single-mode, and enhanced previous versions.

• Only the low-energy protocol battery is included in single-mode implementations. CSR, Nordic Semiconductor and Texas Instruments have released only low-energy Bluetooth mode solutions.
• It has an emission speed and data transfer of 32 Mb/s.
• The low-consumption Bluetooth functionality is integrated into an existing classic Bluetooth controller in dual-mode implementations. Currently (March 2011) the following semiconductor manufacturers have announced the availability of chips that comply with this standard: Atheros, CSR, Broadcom and Texas Instruments. The resulting architecture shares the radio and features of the classic Bluetooth, resulting in a despicable cost increase compared to the classic Bluetooth.

On June 12, 2007, Nokia and the Bluetooth SIG announced that Wibree will be part of the Bluetooth specification, as a Bluetooth Very Low Energy technology.

On December 17, 2009, the Bluetooth SIG adopted Bluetooth Low Energy technology as the hallmark of version 4.0. The provisional names Wibree and Bluetooth ULP (Ultra Low Power) were abandoned and the name BLE was used for a time. In late 2011, the new "Smart Bluetooth Ready" for hosts and "Smart Bluetooth" for sensors as the general public face of BLE.

Bluetooth v5.0 (2016-2017)

In mid-2016, the Bluetooth Special Interest Group (SIG) announces the arrival of Bluetooth 5 by the end of 2016 or early 2017 on its official website www.bluetooth.com. They claim that it will have twice the speed, better reliability and coverage range; In addition, it will have 800% greater capacity than its previous version.

Bluetooth v5.1 (2019)

Version 5.1 was released in January 2019. Among the main novelties that it presents is the one that will be able to know the location of other devices to which they are connected. This detection will not be 100% accurate as in the case of GPS, but it will be able to determine a location to within a few centimeters.[1]

Bluetooth v5.2 (2020)

On January 6, 2020, the Bluetooth Special Interest Group presented version 5.2 of the Bluetooth protocol with important improvements in the Bluetooth LE (Low Energy) radio frequency mode. Among other novelties, the new EATT (Enhanced Attribute Protocol) profile is presented, which improves performance when there are several BLE devices connected simultaneously; security is increased by making connections encrypted by default under the EATT profile; consumption is reduced and signal stability is increased by allowing dynamic optimization of transmission power (LE Power Control); and it is allowed to send audio to multiple devices in a synchronized way (LE Isochronous Channels).

Electronic information

The Bluetooth specification defines a communication channel at a maximum of 720 kbit/s (1 Mbit/s raw capacity) with an optimal range of 10 m (optionally 100 m with repeaters).

A portable speaker with Bluetooth technology.

It operates on the radio frequency from 2.4 to 2.48 GHz with wide spectrum and frequency hopping with the possibility of transmitting in full duplex with a maximum of 1600 hops per second. Frequency hopping occurs among a total of 79 frequencies with 1 MHz intervals; This allows security and robustness.

The output power to transmit at a maximum distance of 10 meters is 0 dBm (1 mW), while the long-range version transmits between 20 and 30 dBm (between 100 mW and 1 W).

In order to achieve the goal of low power and low cost, a solution was devised that can be implemented on a single chip using CMOS circuits. In this way, it was possible to create a 9×9 mm solution that consumes approximately 97% less energy than a common cell phone.

The baseband protocol (single channels per line) combines circuit and packet switching. To ensure that packets do not arrive out of order, slots can be reserved for synchronous packets, using a different hop signal for each packet.

Circuit switching can be asynchronous or synchronous. Each channel can support three synchronous data channels (voice) or one synchronous and one asynchronous data channel.

Each voice channel can support a transfer rate of 64 kbit/s in each direction, which is sufficient for voice transmission.

An asynchronous channel can transmit at most 721 kbit/s in one direction and 56 kbit/s in the opposite direction. However, a synchronous connection can support 432.6 kbit/s in both directions if the link is symmetric.

Hardware architecture

The hardware that makes up the Bluetooth device is made up of two parts:

• a radio device, in charge of modular and transmit the signal.
• a digital controller, composed of a CPU, a digital signal processor (DSP - Digital Signal Processor) called Link Controller (or Link Controller) and interfaces with the host device.

The LC or Link Controller is in charge of the base band processing and the handling of the ARQ and FEC protocols of the physical layer; In addition, it handles both asynchronous and synchronous transfer functions, audio encoding, and data encryption.

The CPU of the device is in charge of the instructions related to Bluetooth in the host device, in order to simplify its operation.
To do this, a software called Link Manager runs on the CPU whose function is to communicate with other devices using the LMP protocol.

Bluetooth protocol stack

Bluetooth is defined as a protocol layer architecture that is made up of core protocols, cable replacement protocols, telephony control protocols, and adopted protocols. At a minimum, any Bluetooth protocol stack must have the following protocols: LMP, L2CAP, and SDP. Also, devices that communicate via Bluetooth can almost always use the HCI and RFCOMM protocols.

PML

The Link Control Protocol (Link Management Protocol, LMP) is used for the establishment and control of the radio link between two devices. It is implemented in the controller.

L2CAP

The Logical Link Control and Adaptation Protocol (L2CAP) is used to multiplex multiple logical connections between two devices that use different higher-level protocols. Provides segmentation and reassembly of packets.

In its basic mode, L2CAP provides packets with a configurable payload of up to 64 kB, and with a default MTU of 672 bytes.

In Relay and Flow Control modes, L2CAP can be configured for isochronous data or a reliable data channel using retransmission and CRC checking.

Appendix 1 of the Bluetooth specification adds two additional modes to L2CAP. These new modes make the previous streaming and flow control modes obsolete:

• Improved relay mode (Enhanced Retransmission Mode, ERTM): This mode is an improved version of the original relay mode. Provides a reliable L2CAP channel.
• Mode streaming (Streaming Mode, SM): It is a very simple way, without retransmission or flow control. Provides unreliable L2CAP channel.

Reliability in any of these modes is optionally guaranteed by the BDR/EDR lower layer by configuring the number of retransmissions and the time to wait before dropping packets. The lower layer ensures that the packets arrive in order.

SDP

The Service Discovery Protocol (SDP) allows a device to discover services offered by other devices and their associated parameters. For example, when you use a mobile phone with a Bluetooth headset, the phone uses SDP to determine which Bluetooth profile the headset can use and the multiplexing protocol settings necessary for the phone to connect with the headset. Each service is identified by a UUID (Universally Unique Identifier).

RFCOMM

RFCOMM (Radio Frequency Communications) is a wire replacement protocol used to generate a virtual serial data stream. RFCOMM offers binary data transport and emulates EIA-232 control signals through the Bluetooth baseband layer.

RFCOMM offers a reliable and user-friendly data flow, similar to TCP. It is used by many profiles related to telephony.

Many Bluetooth applications use RFCOMM because of its broad support and the ability to find public APIs on most operating systems. Also, applications that use the serial port to communicate can be easily ported to RFCOMM.

BNEP

Bluetooth Network Encapsulation Protocol (BNEP) is used to transfer data from another protocol stack over an L2CAP channel. Its main purpose is the transmission of IP packets in a personal area network profile. BNEP performs a function similar to that of SNAP in wireless local area networks.

AVCTP

The Audio/Video Control Transport Protocol (AVCTP) is used by the remote control profile to transfer audio/video control commands over an L2CAP channel. The control buttons on a stereo headset use this protocol to control the music player.

Audio/Video Distribution Transport Protocol (AVDTP) is used for Advanced Audio Distribution Profile to transfer music to stereo headphones via an L2CAP channel designed for video distribution.

TCS

The Telephony Control Protocol - Binary (Telephony Control Protocol - Binary, TCS BIN) is the bit-oriented protocol that defines call control signaling for the establishment of voice calls and data between Bluetooth devices.

Adopted protocols

Adopted protocols are those that have been defined by other standards organizations and have been incorporated into the Bluetooth protocol stack, allowing Bluetooth to encode protocols only when necessary. The adopted protocols include:

Point-to-Point Protocol (PPP)

An Internet standard protocol for transporting IP datagrams over a point-to-point link.

TCP/IP UDP

The base protocol of the TCP/IP protocol suite.

Object Exchange Protocol (OBEX)

A session layer protocol for exchanging objects, providing a model for object representation and operations.

Wireless Application Environment/Wireless Application Protocol (WAE/WAP)

WAE specifies an application framework for wireless devices and WAP is an open standard that enables mobile users to access information and telephony services.

Generic Bluetooth Radio Device

Among the tasks performed by the LC and the Link Manager, the following stand out:

• Shipping and Data Reception.
• Pagination and Petitions.
• Establishment of connections.
• Authentication.
• Negotiation and establishment of link types.
• Establishment of the body type of each package.
• Set the device in sniff or hold mode: The first, sniff, means sniffing, but in Spanish and computer it is translated by listening (the middle): in this case is the frequency or frequencies in which the device is working. Thus, any data package sent in that frequency will be "read" by the device, even if it is not addressed to it. You will read all the data that are sent in that frequency by any other Bluetooth device, is what is called package tracking.
  A similar but frequency-level technique is the one used to detect wi-fi networks, usually to find open networks (without password), when scanning all frequencies, information is obtained from each frequency or channel of the available wi-fi networks.
  Hold for its part means keeping, retaining; this means that the device will remain on that frequency even if it does not emit or receive anything, keeping that frequency always available even if other devices use it.

Uses of Bluetooth

Bluetooth is primarily used in a large number of products such as phones, printers, tablets, smartphones, speakers, and headsets. Its use is suitable when there can be two or more devices in a small area without high bandwidth needs. Its most common use is integrated into phones and tablets, either through Bluetooth headphones or in file transfer. You can also make and make links or link different devices together.

Bluetooth simplifies the discovery and configuration of devices, since devices can tell others what services they offer, allowing a quick connection to be established (connection only, not transmission speed).

The Bluetooth SIG

The effectiveness of various wireless transmission protocols, such as Bluetooth and Wi-Fi, can be compared using spatial capacity (bits per second and square meter).

Bluetooth vs. Wi-Fi

Bluetooth and Wi-Fi meet different needs in today's home environments: from networking and printing to transferring files between tablets, smartphones and personal computers. Both technologies operate in unregulated frequency bands (ISM band).

WiFi

Wifi is similar to the traditional Ethernet network and as such the establishment of communication needs a previous configuration. It uses the same frequency spectrum as Bluetooth with a higher output power leading to stronger connections. Wi-Fi is sometimes called the “Wireless Ethernet”. Although this description is not very precise, it gives an idea of its advantages and disadvantages compared to other alternatives. It is best suited for general-purpose networks: it allows for faster connections, a greater range of distances, and better security mechanisms.

Wi-Fi Direct

Wi-Fi Direct is a certification program that allows multiple Wi-Fi devices to connect to each other without the need for an intermediate access point.

When a device comes within range of Wi-Fi Direct, it can connect using the existing ad hoc protocol, and then collect configuration information using a transfer of the same type as Protected Setup. Connection and setup is so simplified that some suggest this could replace Bluetooth in some situations. Since its advantages are a higher transfer speed (11 Gbps of 802.11ax vs. 50 Mbps of Bluetooth 5.0), it covers a greater distance (100 meters vs. 10 meters of Bluetooth) and a higher theoretical security by using 256-bit encryption against the 128 bits of Bluetooth. However, the advantages offered by Bluetooth technology on the other hand are lower power consumption, the possibility of using more than one device at the same time and the reduced distance that minimizes the risk of interference.