Bluetooth
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Bluetooth Introduction A new communication standard is on the horizon which is set to revolutionise the way mobile phones can exchange data with personal computers, printers, scanners, digital cameras, etc. Called Bluetooth, it is a form of wireless networking. Traditionally, data exchange between phones and PCs has been via infra-red (IrDA) links. The downside to this system is that a line-of-sight path is necessary between devices. Any person or object passing through the IR beam interrupts transmission, casuing data corruption. There have also been compatibilty problems between devices, as not every manufacturer has interpreted the IrDA standard the same way.
Bluetooth Networks Bluetooth modules [measuring just a few centimetres across] operate in the 2.4GHz Industrial Scientific Medical (ISM) band and have a range of about 10 metres. The ISM band has been allocated to low power devices and is licence-free, although part of the band may not available in some areas of France, Spain and Japan. Data rates will be around 400kps-1Mbps, faster than a PC's parallel port, but not as fast as a cable-based LAN. Bluetooth can support an asynchronous data channel, up to three simultaneous synchronous voice channels, or a channel which simultaneously supports asynchronous data and synchronous voice. Each voice channel supports a 64kbps synchronous (voice) link. The asynchronous channel can support an asymmetric link of 721kbps in one direction and 57.6kbps in the return direction, or a 432.6kbps symmetric link. Up to eight Bluetooth devices can be linked together to form a 'Piconet' or personal area network. One device in the Piconet will assume the role of 'Master'. Piconets can be combined to form a 'Scatternet', with devices used as bridges to Ethernet systems, etc.
To minimise interference between networks, and other radio users, Bluetooth employs 'spread spectrum' transmission techniques. The method of spread spectrum transmission chosen for Bluetooth is known as 'frequency hopping'. Bluetooth modules will 'hop' frequency at a rate of 1600 hops per second. Although the sequence of channel-hopping will be pseudo random, the sequence will be known all modules in the same piconet. Any data loss caused by two neighbouring piconets transmitting on the same channel should be recoverable by the forward error correction techniques built into Bluetooth. Forward error correction comprises a small amount of additional data added to each data transmission from which the receiving Bluetooth module can use to correct the corrupted data.
Link Management and Security The Link Manager Software is the part of Bluetooth that handles connections and data transfer between modules. It uses a protocol called Link Manager Protocol (LMP) which controls the following functions: •
Sending and receiving data
•
Connection setup
•
Authentication
Before Bluetooth technology can work properly, the software for Bluetoothenabled devices has to change, including computer operating Systems, E-Mail applications and software in PDAs and mobile phones.
Bluetooth itself, must be able to recognise the device it is connecting to and enable the appropriate software. The Bluetooth philosophy is not to develop new standards and protocols, but to utilise existing standards such as TCP/IP, OBEX, etc. Even with a range of 10 metres, it is possible to listen in to other modules. To maintain privacy, the Bluetooth physical layer includes authentication and encryption. There are three levels of security in Bluetooth, which uses a stream chiper key system.
Applications Although Bluetooth was born out of necessity in the world of mobile data communications, the technology can benefit the office and desktop, replacing the myriad of cables between desktop computer, printer, scanner, network port and other peripherals. Bluetooth supports speech channels, and it is expected that the first Bluetooth products will include headset devices. Real-time video is also a possibilty.
Concept Bluetooth Headset In addition to Matsushita, Bluetooth has support from other major players in the computing and communications arena, including Intel, IBM, Microsoft, 3Com, Nokia, Motorola and Ericsson. All are members of the Bluetooth SIG (Special Interest Group). Unit price for Bluetooth modules are initially expected to be around £20. Prices are expected to drop to £3, allowing Bluetooth modules to be standard fitment to the majority of mobile handsets, personal computers and peripherals.
Bluetooth Networks Bluetooth modules [measuring just a few centimetres across] operate in the 2.4GHz Industrial Scientific Medical (ISM) band and have a range of about 10 metres. The ISM band has been allocated to low power devices and is licence-free, although part of the band may not available in some areas of France, Spain and Japan. Data rates will be around 400kps-1Mbps, faster than a PC's parallel port, but not as fast as a cable-based LAN. Bluetooth can support an asynchronous data channel, up to three simultaneous synchronous voice channels, or a channel which simultaneously supports asynchronous data and synchronous voice. Each voice channel supports a 64kbps synchronous (voice) link. The asynchronous channel can support an asymmetric link of 721kbps in one direction and 57.6kbps in the return direction, or a 432.6kbps symmetric link. Up to eight Bluetooth devices can be linked together to form a 'Piconet' or personal area network. One device in the Piconet will assume the role of 'Master'. Piconets can be combined to form a 'Scatternet', with devices used as bridges to Ethernet systems, etc.
To minimise interference between networks, and other radio users, Bluetooth employs 'spread spectrum' transmission techniques. The method of spread spectrum transmission chosen for Bluetooth is known as 'frequency hopping'. Bluetooth modules will 'hop' frequency at a rate of 1600 hops per second. Although the sequence of channel-hopping will be pseudo random, the sequence will be known all modules in the same piconet. Any data loss caused by two neighbouring piconets transmitting on the same channel should be recoverable by the forward error correction techniques built into Bluetooth. Forward error correction comprises a small amount of additional data added to each data transmission from which the receiving Bluetooth module can use to correct the corrupted data.
Link Management and Security The Link Manager Software is the part of Bluetooth that handles connections and data transfer between modules. It uses a protocol called Link Manager Protocol (LMP) which controls the following functions: •
Sending and receiving data
•
Connection setup
•
Authentication
Before Bluetooth technology can work properly, the software for Bluetoothenabled devices has to change, including computer operating Systems, E-Mail applications and software in PDAs and mobile phones.
Bluetooth itself, must be able to recognise the device it is connecting to and enable the appropriate software. The Bluetooth philosophy is not to develop new standards and protocols, but to utilise existing standards such as TCP/IP, OBEX, etc. Even with a range of 10 metres, it is possible to listen in to other modules. To maintain privacy, the Bluetooth physical layer includes authentication and encryption. There are three levels of security in Bluetooth, which uses a stream chiper key system.
Applications Although Bluetooth was born out of necessity in the world of mobile data communications, the technology can benefit the office and desktop, replacing the myriad of cables between desktop computer, printer, scanner, network port and other peripherals. Bluetooth supports speech channels, and it is expected that the first Bluetooth products will include headset devices. Real-time video is also a possibilty.
Concept Bluetooth Headset In addition to Matsushita, Bluetooth has support from other major players in the computing and communications arena, including Intel, IBM, Microsoft, 3Com, Nokia, Motorola and Ericsson. All are members of the Bluetooth SIG (Special Interest Group). Unit price for Bluetooth modules are initially expected to be around £20. Prices are expected to drop to £3, allowing Bluetooth modules to be standard fitment to the majority of mobile handsets, personal computers and peripherals.
