Ericsson devised the Bluetooth idea in 1994, named after King Harold II, nicknamed "Bluetooth", who united Denmark and Norway in the 10th Century. This short range radio communications idea quickly received wide support, with many companies joining to use it royalty free within a few year. Actual working devices were much, much slower to appear.
Originally Ericsson seemed to have the idea it would cheaply replace cables for voice and data in items like hands free handsets for mobile phones. It originally seemed a faster, longer range version of IrDA (which requires line of sight). Extensions to Bluetooth quickly made it a cable designed by a committee.
Bluetooth provides a lot of hype, but to date (2002) I haven't seen many products that seem all that worthwhile. The industry just isn't delivering on promises (and I don't mean just on Bluetooth). The idea is great, but the reality is that Bluetooth suffers from both radio interference and from incompatibility between devices (although qualification tests are intended to prove they can interoperate). In 2003, when many more devices were (finally) available, there were reports that people just couldn't get devices to interoperate. Just how should a Bluetooth mouse interact with a passing cellular phone or with your microwave? Some claimed abilities just plain don't make sense.
There are also regulatory problems. How do you turn off a Bluetooth device when flying? Or when at a service station that requires all transmitters to be switched off when pumping fuel?
Brief Description
Bluetooth runs between 2.402 and 2.480 GHz in the unlicensed industrial band (also used by IEEE 802.11 WiFi networks and microwave ovens). It changes frequency 1600 times a second, and each connection uses 79 different frequencies with a channel separation of 1 MHz. Forward error correction is used to reduce interference from items like microwave ovens, by avoiding frequencies where interference is present.
Data rates are 721 kHz upstream and 57.6 kHz downstream asynchronously, or 432.6 kHz in both directions synchronously (1 mbps total before overheads, or slightly slower than HomeRF and much slower than 802.11). A double speed version may appear later. Voice is sent at 64 kbits in synchronous mode. Up to three voice channels can be used at the same time as a synchronous data channel, which does give it an advantage over other wireless networks for allowing each device to be a wireless phone connection.
Bluetooth transmits a maximum 10 mW, which gives it a range of about 10 metres. Power amplifiers can boost this to 100 mW and a range of 100 metres, at the expense of increased power consumption. This would make it of use for home and small office networks, where it is competing with IEEE 802.11 WiFi and HomeRF. Bluetooth was designed to be cheap, under $10 a device eventually, which would be an advantage over other wireless networks. Cheap versions have not appeared as at 2002, and even at 2003 the prices are way higher than IrDA.
Bluetooth can set up a Piconet of two to eight devices. Devices have a 48 bit unique serial number, and can identify themselves within two seconds. First device identified becomes the master, sets the 1600 frequencies to be used each second, and all other devices lock to this sequence. The master transmits in even slots, the slave responds in odd slots. Active slave devices are assigned an address, and listen for slots addressed them themselves. Slaves may also go into lower power sniff, hold or park modes. In sniff mode a device listens only during specific sniff slots. In hold, a device listens only to determine if it should become active. In park, a device gives up its address.
Several Piconets can join into a Scatternet, making connections via any device that can access both Piconets.
Bluetooth devices listen every 1.28 seconds for other signals. If detected, modules look for communications on 32 frequencies. There are various methods of identifying other Bluetooth modules, putting modules into a low power hold mode, or "sniff" (listen) and "park" modes, where devices use about 2 mW.
Link Management Protocol is used between link managers. A Host Controller Interface may be used to isolate the baseband and link manager from transport protocols such as RS232 and USB, which would allow standard interfaces to Bluetooth without running Bluetooth specific software.
Software protocols include the lowest level L2CAP (Logical Link Control and Adaption Protocol) to the link controller. SDP provides service discovery to L2CAP. RFCOMM provides serial data transfer. Port Emulation Entity allows legacy software to interface. Telephony Control Protocol Specification (TCS) provides voice and call control. Bluetooth supports IrOBEX from IrDA over RFCOMM or TCP/IP, and application profiles include phonebook and calendar synchronising, file transfer, and business card support. It also supports WAP. If you think all of that will work for every device, I have a fine bridge for sale.
Data is transmitted for connection channels in packets with a 32 bit header and a payload of up to 64k bytes. The header provides a 16 bit length integrity check, and a 16 bit destination. Connectionless channels use 0x0002 as the destination and an indication of the originating protocol. There are about thirteen packet types.
The core specifications run over 1000 pages, so those interested in the details should consult them.
Supporting Hardware
The hardware consists of the radio frequency section, the baseband digital signal processing hardware, and the link manager. The link manager firmware performs device discovery, authentication and link configuration.
Bluetooth ICs now generally consist of a bipolar RF device, and a CMOS baseband controlling microcomputer. The computer components can be expected to draw around 40 mA. Most manufacturers are expected to offer a complete package rather than components. Sizes are typically about 10mm x 15mm, but another 20-30 components are also needed. There are a number of such building blocks available, but I don't know of any items for commercial sale as yet (Sept 2000). Costs at present for mass purchase are in the US$25-$35 range, and are not expected to drop to the aimed at US$5 range until at least 2003. This will make Bluetooth too expensive initially for low end devices like mice, joysticks, keyboards and the like.
Claimed Facilities
Bluetooth promises transparent transfer of address and schedule information. As this does not always work between different products, and especially between different computer systems, I have no great confidence that Bluetooth will be any more effective than IrDA, serial cables, or networks. It is relatively easy to transfer files. It is much hard to persuade different programs to make use of the files.
Bluetooth also suffers the disadvantage that a piece of wire is both cheaper and more reliable.
Reported Problems
As one would expect from any wireless system, security concerns appeared. A.L.Digital has developed tools which enable the download of address books and calendars without any normal handshake between devices. Users would be unaware their Bluetooth device was compromised. They report security flaws in Nokia 6310 and 8910 models, and Sony Ericsson R520, T68i, T610 and Z1010. Users would need to switch off Bluetooth or select non-discoverable mode, and check approved connections to protect themselves.
Early Bluetooth Products
- 3Com 3CRWB6096
- Trendy name for a PC Card with XJack antenna. US$149 A$295
- BrainBox BL500 BL-620
- Type II PC Card for Windows. www.brainbox.com
- Ericsson Headset
- Ericsson have a Bluetooth mobile phone headset, compatible with their R320 and T28 mobile phones. I first saw an actual advertisment for the T39 actually available in Australia in November 2001, at A$600.
- Ericsson Bluetooth Local Infotainment Point
- BLIP is a web server hub for up to 7 devices. About US$500 late 2001. Formerly at http://www.ericsson.com/blip
- Ericsson Web Screen H610
- Prototype cordless web screen, for internet phone, email and address book. Touch screen, microphone and speaker. Linux based with Opera. Due early 2002. Sounds interesting.
- GN Netcom Headset
- Bluetooth headset. NiCd battery. US$499 www.headsets.com
- Nokia DTL-1
- PC Card compatible with Nokia 6210 mobile phone.
- Toshiba PC Card
- Toshiba claim the first Bluetooth PC Card size Bluetooth module. I saw it on sale March 2001, at A$339 from Harris Technology.
Bluetooth and Apple Macintosh
The 2004 release of Bluetooth 1.5 for Mac OS X added support for Bluetooth printers (if they support the Bluetooth Hard Copy Replacement Profile - HCRP) and headsets (if they support Bluetooth Headset profile - HP).
Bluetooth Mouse and Apple Macintosh
Because many Apple Macintosh OS X systems have Bluetooth built in, there is considerable interest in using Bluetooth mice.
Apple Bluetooth Mouse works, and goes through a pair of AA batteries in about 45 days. One user suggests using Lithium batteries, as standard batteries give low voltage warnings well before replacement is needed. One user warns it clicks when you pick it up.
Kensington PocketMouse Bluetooth Optical is reported to work. Try http://www.kensington.com/html/5529.html
Logitech MX900 mouse works, however Logitech do not provide Macintosh drivers to support its extra buttons. Reported not to be recognised by a Macintosh when waking from sleep.
Macally BT Mouse Jr scroll mouse is reported to work. Uses 2 AA batteries, and at 120 grams is heavier than the Macintosh BT mouse 95 grams). Battery life was reported to be a rather low one week, but it has a warning flasher. I gather many people are using rechargeable batteries as a result.
MacMice MouseBT is reported (Oct 2004) to have poor range when paired with a G5 tower. Changing batteries may help.
Microsoft INtelliMouse (as of October '04) part of the "Optical Desktop Elite USB for BLUETOOTH" set will not pair with a Mac, contrary to Apple technote #107585. The previous version of this product (called Microsoft Wireless Desktop for Bluetooth) did work (for some people), at least up to OS X 10.3.5. The problem may however be a Macintosh Bluetooth update.
RadTech BT-500 Mobile Mouse is an optical 3 button mouse with a scroll wheel, with on on off switch (most mice do not). It runs on 2 AAA and is smaller than many mice. Has a sleep mode that works with Powerbooks.
Readers should note that many non-Bluetooth wireless keyboards exist (including some from Microsoft and Logitech). These work by simply transmitting keyboard and mouse data to a transceiver that plugs into keyboard and mouse ports (formerly all PS2 for Windows, but now USB). Some of these keyboards are older style infra-red wireless (not the same as IrDA) rather than radio, others are lower radio frequency than Bluetooth. These devices do not and never have required a driver, as they are identical to an ordinary keyboard except for replacing the card with a wireless link. You can make even the old infra-red ones work with a Macintosh by plugging the PS2 connectors from the transceiver into a USB to PS2 converter.
More Information
Other sites with Bluetooth material.
- Bluetooth
- The official site www.bluetooth.com
- Bluetooth introductions
- The official site introductions and guides.
- More on Bluetooth
- A third party site www.anywhereyougo.com/
Alternatives to Bluetooth
There are several realistic alternatives to Bluetooth for short range wireless connectivity. One of them is the slower, line of sight, and vastly underrated IrDA.
In the radio area, check HiperLan2 Formerly http://www.hiperlan2.com/site/home.htm This is a local area network to replace data cabling. It is intended to link VCRs, cameras, printers and PCs. Runs at 5.8 GHz at up to 54Mbit/s.
HomeRF is aimed more at the home and small business, and lacks the capacity for large scale business. SWAP (shared wireless access protocol) is a frequency hopping radio system, like Bluetooth, in the 2.4 GHz band (like Bluetooth). A network supports up to 127 data links and six voice links over a 150 foot range. www.homerf.org
You should also note that most IEEE 802.11 (WiFi) wireless LANs also operate in the same 2.4 GHz band as Bluetooth. Interference is very likely as the density of devices increases. I've seen a 3Com Home Wireless Gateway with 3 wired 10/100 Ethernet ports in May 2001 at A$750 from Harris Technology. Also a 3Com wireless PC Card at A$395. The Wireless Ethernet Compatibility Alliance (WECA) certify 802.11b compatibility and allow use of the WiFi (Wireless fidelity) brand name. 802.11b is 5.5Mbps and 11Mbps instead of the 1 and 2 Mbps of 802.11. The range is 100 or more metres, so it is more a wired local area network replacement. As at 2003, it looked like WiFi had won the radio connection battle, with a variety of much better priced products, even faster variations, and a lot of support. Note that WiFi is inherently insecure, especially as delivered.