Bluetooth
Bluetooth is a proprietary open wireless protocol for exchanging data over short distances (using short length radio waves) from fixed and mobile devices, creating personal area networks (PANs). It was originally conceived as a wireless alternative to RS-232 data cables. It can connect several devices, overcoming problems of synchronize.
The word Bluetooth is an anglicised version of Danish Blåtand, the epithet of the tenth-century king Harald I of Denmark and parts of Norway who united dissonant Danish tribes into a single kingdom. The implication is that Bluetooth does the same with communications protocols, uniting them into one universal standard. Although blå in modern Scandinavic languages means blue, during the Viking age it also could mean black. So a historically correct translation of Old Norse Harald Blátönn could rather be Harald Blacktooth than Harald Bluetooth.
Implementation
Bluetooth uses a radio technology called frequency-hopping spread spectrum, which chops up the data being sent and transmits chunks of it on up to 79 bands of 1 MHz width in the range 2402-2480 MHz. This is in the globally unlicensed Industrial, Scientific and Medical (ISM) 2.4 GHz short-range radio frequency band.
In its basic rate (BR) mode, the modulation is Gaussian frequency-shift keying (GFSK). It can achieve a gross data rate of 1 Mbit/s. In extended data rate (EDR) π/4-DQPSK and 8DPSK are used, giving 2, and 3 Mbit/s respectively. Bluetooth provides a secure way to connect and exchange information between devices such as mobile phones, telephones, laptops, personal computers, printers, Global Positioning System (GPS) receivers, digital cameras, and video game consoles.
The Bluetooth specifications are developed and licensed by the Bluetooth Special Interest Group (SIG). The Bluetooth SIG consists of companies in the areas of telecommunication, computing, networking, and consumer electronics.
To be marketed as a bluetooth device, it must be qualified to standards defined by the SIG.
Uses
Bluetooth is a standard communications protocol primarily designed for low power consumption, with a short range (power-class-dependent: 100m, 10m and 1m, but ranges vary in practice; see table below) based on low-cost transceiver microchips in each device. Because the devices use a radio (broadcast) communications system, they do not have to be in line of sight of each other.
| Class | Maximum Permitted Power | Range (approximate) | |
|---|---|---|---|
| mW | dBm | ||
| Class 1 | 100 mW | 20 dBm | ~100 metres |
| Class 2 | 2.5 mW | 4 dBm | ~10 metres |
| Class 3 | 1 mW | 0 dBm | ~1 metres |
In most cases the effective range of class 2 devices is extended if they connect to a class 1 transceiver, compared to a pure class 2 network. This is accomplished by the higher sensitivity and transmission power of Class 1 devices.
| Version | Data Rate | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Version 1.2 | 1 Mbit/s | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Version 2.0 + EDR | 3 Mbit/s |
List of applications
- Wireless control of and communication between a mobile phone and a hands-free headset. This was one of the earliest applications to become popular.
- Wireless networking between PCs in a confined space and where little bandwidth is required.
- Wireless communication with PC input and output devices, the most common being the mouse, keyboard and printer.
- Transfer of files, contact details, calendar appointments, and reminders between devices with OBEX.
- Replacement of traditional wired serial communications in test equipment, GPS receivers, medical equipment, bar code scanners, and traffic control devices.
- For controls where infrared was traditionally used.
- For low bandwidth applications where higher USB bandwidth is not required and cable-free connection desired.
- Sending small advertisements from Bluetooth-enabled advertising hoardings to other, discoverable, Bluetooth devices.
- Wireless bridge between two Industrial Ethernet (e.g., PROFINET) networks.
- Three seventh-generation game consoles, Nintendo's Wii and Sony's PlayStation 3 and PSP Go, use Bluetooth for their respective wireless controllers.
- Dial-up internet access on personal computers or PDAs using a data-capable mobile phone as a wireless modem like Novatel Mifi.
- Short range transmission of health sensor data from medical devices to mobile phone, set-top box or dedicated telehealth devices
Bluetooth vs. Wi-Fi IEEE 802.11 in networking
Bluetooth and Wi-Fi have many applications: setting up networks, printing, or transferring files.
Wi-Fi is intended for resident equipment and its applications. The category of applications is outlined as WLAN, the wireless local area networks. Wi-Fi is intended as a replacement for cabling for general local area network access in work areas.
Bluetooth is intended for non resident equipment and its applications. The category of applications is outlined as the wireless personal area network (WPAN). Bluetooth is a replacement for cabling in a variety of personally carried applications in any ambience.
Wi-Fi is a traditional Ethernet network, and requires configuration to set up shared resources, transmit files, and to set up audio links (for example, headsets and hands-free devices). Wi-Fi uses the same radio frequencies as Bluetooth, but with higher power, resulting in a stronger connection. Wi-Fi is sometimes called "wireless Ethernet." This description is accurate, as it also provides an indication of its relative strengths and weaknesses. Wi-Fi requires more setup but is better suited for operating full-scale networks; it enables a faster connection and better range from the base station.
The nearest equivalent in Bluetooth is the DUN profile, which allows devices to act as modem interfaces.
Bluetooth devices
Bluetooth exists in many products, such as telephones, the Wii, PlayStation 3, PSP Go, Lego Mindstorms NXT and in some high definition watches, modems and headsets. The technology is useful when transferring information between two or more devices that are near each other in low-bandwidth situations. Bluetooth is commonly used to transfer sound data with telephones (i.e., with a Bluetooth headset) or byte data with hand-held computers (transferring files).
Bluetooth protocols simplify the discovery and setup of services between devices. Bluetooth devices can advertise all of the services they provide. This makes using services easier because more of the security, network address and permission configuration can be automated than with many other network types.
Computer requirements
A personal computer must have a Bluetooth adapter in order to communicate with other Bluetooth devices (such as mobile phones, mice and keyboards). While some desktop computers and most recent laptops come with a built-in Bluetooth adapter, others will require an external one in the form of a dongle.
Unlike its predecessor, IrDA, which requires a separate adapter for each device, Bluetooth allows multiple devices to communicate with a computer over a single adapter.
Operating system support
For more details on this topic, see Bluetooth stack.
For Microsoft platforms, Windows XP Service Pack 2 and later releases have native support for Bluetooth. Previous versions required users to install their Bluetooth adapter's own drivers, which were not directly supported by Microsoft.[10] Microsoft's own Bluetooth dongles (packaged with their Bluetooth computer devices) have no external drivers and thus require at least Windows XP Service Pack 2.
GNU/Linux has two popular Bluetooth stacks, BlueZ and Affix. The BlueZ stack is included with most Linux kernels and was originally developed by Qualcomm. The Affix stack was developed by Nokia. FreeBSD features Bluetooth support since its 5.0 release. NetBSD features Bluetooth support since its 4.0 release. Its Bluetooth stack has been ported to OpenBSD as well.
Bluetooth specification
The Bluetooth specification was developed in 1994 by Jaap Haartsen and Sven Mattisson, who were working for Ericsson in Lund, Sweden.The specification is based on frequency-hopping spread spectrum technology.
The specifications were formalized by the Bluetooth Special Interest Group (SIG). The SIG was formally announced on May 20, 1998. Today it has a membership of over 12,000 companies worldwide. It was established by Ericsson, IBM, Intel, Toshiba, and Nokia, and later joined by many other companies.
Bluetooth 1.0 and 1.0B
Versions 1.0 and 1.0B had many problems, and manufacturers had difficulty making their products interoperable. Versions 1.0 and 1.0B also included mandatory Bluetooth hardware device address (BD_ADDR) transmission in the Connecting process (rendering anonymity impossible at the protocol level), which was a major setback for certain services planned for use in Bluetooth environments.
Bluetooth 1.1Ratified
- Many errors found in the 1.0B specifications were fixed.
- Added support for non-encrypted channels.
- Received Signal Strength Indicator (RSSI).
Bluetooth 1.2
This version is backward compatible with 1.1 and the major enhancements include the following:
- Faster Connection and Discovery
- Adaptive frequency-hopping spread spectrum (AFH), which improves resistance to radio frequency interference by avoiding the use of crowded frequencies in the hopping sequence.
- Higher transmission speeds in practice, up to 721 kbit/s, than in 1.1.
- Extended Synchronous Connections (eSCO), which improve voice quality of audio links by allowing retransmissions of corrupted packets, and may optionally increase audio latency to provide better support for concurrent data transfer.
- Host Controller Interface (HCI) support for three-wire UART.
- Ratified as IEEE Standard 802.15.1-2005
- Introduced Flow Control and Retransmission Modes for L2CAP.
Bluetooth 2.0 + EDR
This version of the Bluetooth specification was released on November 10, 2004. It is backward compatible with the previous version 1.2. The main difference is the introduction of an Enhanced Data Rate (EDR) for faster data transfer. The nominal rate of EDR is about 3 megabits per second, although the practical data transfer rate is 2.1 megabits per second.The additional throughput is obtained by using a different radio technology for transmission of the data. Standard, or Basic Rate, transmission uses Gaussian Frequency Shift Keying (GFSK) modulation of the radio signal with a gross air data rate of 1 Mbit/s. EDR uses a combination of GFSK and Phase Shift Keying modulation (PSK) with two variants, π/4-DQPSK and 8DPSK. These have gross air data rates of 2, and 3 Mbit/s respectively.
According to the 2.0 + EDR specification, EDR provides the following benefits:
- Three times the transmission speed (2.1 Mbit/s) in some cases.
- Reduced complexity of multiple simultaneous connections due to additional bandwidth.
- Lower power consumption through a reduced duty cycle.
The Bluetooth Special Interest Group (SIG) published the specification as "Bluetooth 2.0 + EDR" which implies that EDR is an optional feature. Aside from EDR, there are other minor improvements to the 2.0 specification, and products may claim compliance to "Bluetooth 2.0" without supporting the higher data rate. At least one commercial device, the HTC TyTN Pocket PC phone, states "Bluetooth 2.0 without EDR" on its data sheet.
Bluetooth 2.1 + EDR
Bluetooth Core Specification Version 2.1 + EDR is fully backward compatible with 1.2, and was adopted by the Bluetooth SIG on July 26, 2007.It supports theoretical data transfer speeds of up to 3 Mbit/s. This specification includes the following features:
- Extended inquiry response (EIR)
- Provides more information during the inquiry procedure to allow better filtering of devices before connection. This information may include the name of the device, a list of services the device supports, the transmission power level used for inquiry responses, and manufacturer defined data.
- Sniff subrating
- Reduces the power consumption when devices are in the sniff low-power mode, especially on links with asymmetric data flows. Human interface devices (HID) are expected to benefit the most, with mouse and keyboard devices increasing their battery life by a factor of 3 to 10.[citation needed] It lets devices decide how long they will wait before sending keepalive messages to one another. Previous Bluetooth implementations featured keep alive message frequencies of up to several times per second. In contrast, the 2.1 + EDR specification allows pairs of devices to negotiate this value between them to as infrequently as once every 10 seconds.
- Encryption pause/resume (EPR)
- Enables an encryption key to be changed with less management required by the Bluetooth host. Changing an encryption key must be done for a role switch of an encrypted ACL link, or every 23.3 hours (one Bluetooth day) encryption is enabled on an ACL link. Before this feature was introduced, when an encryption key is refreshed the Bluetooth host would be notified of a brief gap in encryption while the new key was generated; so the Bluetooth host was required to handle pausing data transfer (however data requiring encryption may already have been sent before the notification that encryption is disabled has been received). With EPR, the Bluetooth host is not notified of the gap, and the Bluetooth controller ensures that no unencrypted data is transferred while they key is refreshed.
- Secure simple pairing (SSP)
- Radically improves the pairing experience for Bluetooth devices, while increasing the use and strength of security. See the section on Pairing below for more details. It is expected that this feature will significantly increase the use of Bluetooth.
- Near field communication (NFC) cooperation
- Automatic creation of secure Bluetooth connections when NFC radio interface is also available. This functionality is part of SSP where NFC is one way of exchanging pairing information. For example, a headset should be paired with a Bluetooth 2.1 + EDR phone including NFC just by bringing the two devices close to each other (a few centimeters). Another example is automatic uploading of photos from a mobile phone or camera to a digital picture frame just by bringing the phone or camera close to the frame.
- Non-Automatically-Flushable Packet Boundary Flag (PBF)
- Using this feature L2CAP may support both isochronous (A2DP media Streaming) and asynchronous data flows (AVRCP Commands) over the same logical link by marking packets as automatically-flushable or non-automatically-flushable by setting the appropriate value for the Packet_Boundary_Flag in the HCI ACL Data Packet
Bluetooth 3.0 + HS
The 3.0 + HS specification was adopted by the Bluetooth SIG on April 21, 2009. It supports theoretical data transfer speeds of up to 24 Mbit/s, though not over the bluetooth link itself. Instead, the bluetooth link is used for negotiation and establishment, and the high data rate traffic is carried over a colocated wifi link. Its main new feature is AMP (Alternate MAC/PHY), the addition of 802.11 as a high speed transport. Two technologies had been anticipated for AMP: 802.11 and UWB, but UWB is missing from the specification.
- Alternate MAC/PHY
- Enables the use of alternative MAC and PHYs for transporting Bluetooth profile data. The Bluetooth Radio is still used for device discovery, initial connection and profile configuration, however when lots of data needs to be sent, the high speed alternate MAC PHY (802.11, typically associated with Wi-Fi) will be used to transport the data. This means that the proven low power connection models of Bluetooth are used when the system is idle, and the low power per bit radios are used when lots of data needs to be sent.
- Unicast connectionless data
- Permits service data to be sent without establishing an explicit L2CAP channel. It is intended for use by applications that require low latency between user action and reconnection/transmission of data. This is only appropriate for small amounts of data.
- Read encryption key size
- Introduces a standard HCI command for a Bluetooth host to query the encryption key size on an encrypted ACL link. The encryption key size used on a link is required for the SIM Access Profile, so generally Bluetooth controllers provided this feature in a proprietary manner. Now the information is available over the standard HCI interface.
- Enhanced Power Control
- Updates the power control feature to remove the open loop power control, and also to clarify ambiguities in power control introduced by the new modulation schemes added for EDR. Enhanced power control removes the ambiguities by specifying the behaviour that is expected. The feature also adds closed loop power control, meaning RSSI filtering can start as the response is received. Additionally, a "go straight to maximum power" request has been introduced, this is expected to deal with the headset link loss issue typically observed when a user puts their phone into a pocket on the opposite side to the headset.
Bluetooth V4.0 (Ble; low energy protocols)
Main article: Bluetooth low energy
On December 17, 2009, the Bluetooth SIG adopted Bluetooth low energy (Ble) as the hallmark feature of the version 4.0 .The provisional names Wibree and Bluetooth ULP (Ultra Low Power) are abandoned.
On June 12, 2007, Nokia and Bluetooth SIG had announced that Wibree will be a part of the Bluetooth specification, as an ultra-low power Bluetooth technology. Expected use cases include watches displaying Caller ID information, sports sensors monitoring the wearer's heart rate during exercise, and medical devices. The Medical Devices Working Group is also creating a medical devices profile and associated protocols to enable this market. Bluetooth low energy technology is designed for devices to have a battery life of up to one year.
