About Bluetooth
Contents
1. About the name
2. General information
2.1. Embedded Bluetooth
3. Features by version
3.1. Bluetooth 1.0 and 1.0B
3.2. Bluetooth 1.1
3.3. Bluetooth 1.2
3.4. Bluetooth 2.0
4. Future Bluetooth uses
5. Bluetooth profiles
About the name
The system is named after a Danish king Harald Blatand ( Harold Bluetooth in English), King of Denmark and Norway from 935 and 936 respectively, to 940 known for his unification of previously warring tribes from Denmark, Norway and Sweden . Bluetooth likewise was intended to unify different technologies like computers and mobile phones . The Bluetooth logo merges the Nordic runes for H and B.
General information
The latest version currently available to consumers is 2.0, but few manufacturers have started shipping any products yet. Apple Computer, Inc. offered the first products supporting version 2.0 to end customers in January 2005. The core chips have been available to OEMs (from November 2004 ), so there will be an influx of 2.0 devices in mid-2005. The previous version, on which all earlier commercial devices are based, is called 1.2.
Bluetooth is a wireless radio standard primarily designed for low power consumption, with a short range (up to 10 meters) and with a low-cost transceiver microchip in each device.
It can be used to wirelessly connect peripherals like printers or keyboards to computers, or to have PDAs communicate with other nearby PDAs or computers.
Cell phones with integrated Bluetooth technology have also been sold in large numbers, and are able to connect to computers, PDAs and, specifically, to handsfree devices. BMW was the first motor vehicle manufacturer to install handsfree Bluetooth technology in its cars, adding it as an option on its 3 Series , 5 Series and X5 vehicles. Since then, other manufacturers have followed suit, with many vehicles, including the 2004 Toyota Prius and the 2004 Lexus LS 430. The Bluetooth car kits allow users with Bluetooth-equipped cell phones to make use of some of the phone's features, such as making calls, while the phone itself can be left in a suitcase or in the boot/trunk, for instance.
The standard also includes support for more powerful, longer-range devices suitable for constructing wireless LANs .
A Bluetooth device playing the role of "master" can communicate with up to 7 devices playing the role of "slave". At any given instant in time, data can be transferred between the master and one slave; but the master switches rapidly from slave to slave in a round-robin fashion. (Simultaneous transmission from the master to multiple slaves is possible, but not used much in practice). These groups of up to 8 devices (1 master and 7 slaves) are called piconets .
The Bluetooth specification also allows connecting two or more piconets together to form a scatternet , with some devices acting as a bridge by simultaneously playing the master role in one piconet and the slave role in another piconet. These devices have yet to come, though are supposed to appear within the next two years.
Any device may perform an "inquiry" to find other devices to which to connect, and any device can be configured to respond to such inquiries.
Pairs of devices may establish a trusted relationship by learning (by user input) a shared secret known as a "passkey". A device that wants to communicate only with a trusted device can cryptographically authenticate the identity of the other device. Trusted devices may also encrypt the data that they exchange over the air so that no one can listen in.
The protocol operates in the license-free ISM band at 2.45 GHz . In order to avoid interfering with other protocols which use the 2.45 GHz band, the Bluetooth protocol divides the band into 79 channels (each 1 MHz wide) and changes channels up to 1600 times per second. Implementations with versions 1.1 and 1.2 reach speeds of 723.1 kbit /s. Version 2.0 implementations feature Bluetooth Enhanced Data Rate (EDR), and thus reach 2.1 Mbit /s. Technically version 2.0 devices have a higher power consumption, but the three times faster rate reduces the transmission times, effectively reducing consumption to half that of 1.x devices (assuming equal traffic load).
Bluetooth differs from Wi-Fi in that the latter provides higher throughput and covers greater distances but requires more expensive hardware and higher power consumption. They use the same frequency range , but employ different multiplexing schemes. While Bluetooth is a cable replacement for a variety of applications, Wi-Fi is a cable replacement only for local area network access. A glib summary is that Bluetooth is wireless USB whereas Wi-Fi is wireless Ethernet .
Many USB Bluetooth adapters are available, some of which also include an IrDA adapter.
Bluetooth devices and modules are increasingly being made available which come with an embedded stack and a standard UART port. The UART protocol can be as simple as the industry standard AT protocol, which allows the device to be configured to cable replacement mode. This means it now only takes a matter of hours (instead of weeks) to enable legacy wireless products that communicate via UART port.
Features by version
Versions 1.0 and 1.0B had numerous problems and the various manufacturers had great difficulties in making their products interoperable. 1.0 and 1.0B also had mandatory Bluetooth Hardware Device Address (BD_ADDR) transmission in the handshaking process, rendering anonymity impossible at a protocol level, which was a major set-back for services planned to be used in Bluetooth environments, such as Consumerium .
In version 1.1 many errata found in the 1.0B specifications were fixed. There was added support for non-encrypted channels.
This version is backwards compatible with 1.1 and the major enhancements include
- Adaptive Frequency Hopping (AFH), which improves resistance to radio interference by avoiding using crowded frequencies in the hopping sequence
- Higher transmission speeds in practice
- extended Synchronous Connections (eSCO), which improves voice quality of audio links by allowing retransmissions of corrupted packets.
- Received Signal Strength Indicator (RSSI)
- Host Controller Interface (HCI) support for 3-wire UART
- HCI access to timing information for Bluetooth applications.
This version is backwards compatible with 1.x and the major enhancements include
- Non-hopping narrowband channel(s) introduced. These are faster but have been criticised as defeating a built-in security mechanism of earlier versions; however frequency hopping is hardly a reliable security mechanism by today's standards. Rather, Bluetooth security is based mostly on cryptography.
- Broadcast/ multicast support. Non-hopping channels are used for advertising Bluetooth service profiles offered by various devices to high volumes of Bluetooth devices simultaneously, since there is no need to perform handshaking with every device. (In previous versions the handshaking process takes a bit over one second.)
- Enhanced Data Rate (EDR) of 2.1 Mbit /s.
- Built-in quality of service.
- Distributed media-access control protocols.
- Faster response times.
- Halved power consumption due to shorter duty cycles.
Future Bluetooth uses
One of the ways Bluetooth technology may become useful is in Voice over IP . When VOIP becomes more widespread, companies may find it unnecessary to employ telephones physically similar to today's analogue telephone hardware. Bluetooth may then end up being used for communication between a cordless phone and a computer listening for VOIP and with an infrared PCI card acting as a base for the cordless phone. The cordless phone would then just require a cradle for charging. Bluetooth would naturally be used here to allow the cordless phone to remain operational for a reasonably long period.
Bluetooth profiles
In order to use Bluetooth, a device must be able to interpret certain Bluetooth profiles. These define the possible applications. Following profiles are defined:
- Generic Access Profile (GAP)
- Service Discovery Application Profile (SDAP)
- Cordless Telephony Profile (CTP)
- Intercom Profile (IP)
- Serial Port Profile (SPP)
- Headset Profile (HSP)
- Dial-up Networking Profile (DUNP)
- Fax Profile
- LAN Access Profile (LAP)
- Generic Object Exchange Profile (GOEP)
- Object Push Profile (OPP)
- File Transfer Profile (FTP)
- Synchronisation Profile (SP)
This profile allows synchronisation of Personal Information Manager (PIM) items. As this profile originated as part of the infrared specifications but has been adopted by the Bluetooth SIG to form part of the main Bluetooth specification, it is also commonly referred to as IrMC Synchronization.
- Hands-Free Profile (HFP)
- Human Interface Device Profile (HID)
- Hard Copy Replacement Profile (HCRP)
- Basic Imaging Profile (BIP)
- Personal Area Networking Profile (PAN)
- Basic Printing Profile (BPP)
- Advanced Audio Distribution Profile (A2DP)
- Audio Video Remote Control Profile (AVRCP)
- SIM Access Profile (SAP)
