http://www.gsmfavorites.com/documents/bluetooth/introduction/
Bluetooth is an always-on, short-range radio hookup that resides on a microchip. It was initially developed by Swedish mobile phone maker Ericsson in 1994 as a way to let laptop computers make calls over a mobile phone. Since then, several thousand companies have signed on to make
Bluetooth the low-power short-range wireless standard for a wide range of devices. Industry observers expect Bluetooth to be installed in billions of devices by 2005.
The Bluetooth standards are published by an industry consortium known as the Bluetooth SIG
(special interest group).
The concept behind Bluetooth is to provide a universal short-range wireless capability. Using the
2.4 GHz band, available globally for unlicensed low-power uses, two Bluetooth devices within 10 m of each other can share up to 720 Kbps of capacity. Bluetooth is intended to support an open-ended list of applications, including data (such as schedules and telephone numbers), audio, graphics, and even video. For example, audio devices can include headsets, cordless and standard phones, home stereos, and digital MP3 players. Following are some examples of the capabilities that Bluetooth can provide consumers:

Make calls from a wireless headset connected remotely to a cell phone;

Eliminate cables linking computers to printers, keyboards, and the mouse;

Hook up MP3 players wirelessly to other machines to download music;

Set up home networks so that a couch potato can remotely monitor air conditioning, the oven, and children's Internet surfing;

Call home from a remote location to turn appliances on and off, set the alarm, and monitor activity.
Bluetooth Applications
Bluetooth is designed to operate in an environment of many users. Up to eight devices can communicate in a small network called a piconet. Ten of these piconets can coexist in the same coverage range of the Bluetooth radio. To provide security, each link is encoded and protected against eavesdropping and interference.
Bluetooth provides support for three general application areas using short-range wireless connectivity:

Data and voice access points - Bluetooth facilitates real-time voice and data transmissions by providing effortless wireless connection of portable and stationary communications devices;

Cable replacement - Bluetooth eliminates the need for numerous, often proprietary cable attachments for connection of practically any kind of communications device. Connections are instant and are maintained even when devices are not within line of sight. The range of each radio is approximately 10 m, but can be extended to 100 m with an optional amplifier;

 Ad hoc networking - A device equipped with a Bluetooth radio can establish instant connection to another Bluetooth radio as soon as it comes into range.
Bluetooth Standards Documents
The Bluetooth standards present a formidable bulk—well over 1,500 pages, divided into two groups: core and profile. The core specifications describe the details of the various layers of the Bluetooth protocol architecture, from the radio interface to link control. Related topics are also covered, such as interoperability with related technologies, testing requirements, and a definition of various
Bluetooth timers and their associated values.
The profile specifications are concerned with the use of Bluetooth technology to support various applications. Each profile specification discusses the use of the technology defined in the core specifications to implement a particular usage model. The profile specification includes a description of which aspects of the core specifications are mandatory, optional, and not applicable.
The purpose of a profile specification is to define a standard of interoperability, so that products from different vendors that claim to support a given usage model will work together. In general terms, profile specifications fall into one of two categories: cable replacement or wireless audio.
The cable replacement profiles provide a convenient means for logically connecting devices in proximity to one another and for exchanging data. For example, when two devices first come within range of one another, they can automatically query each other for a common profile. This might then cause the end users of the device to be alerted, or cause some automatic data exchange to take place. The wireless audio profiles are concerned with establishing short-range voice connections.
The Bluetooth developer must wade through the many documents with a particular application in mind. The reading list begins with coverage of some essential core specifications plus the general access profile. This profile is one of a number of profiles that serve as a foundation for other profiles and don't specify independently usable functionality. The general access profile specifies how the Bluetooth baseband architecture, defined in the core specifications, is to be used between devices that implement one or multiple profiles. Following a basic set of documents, the reading list splits along two lines, depending on whether the reader's interest is in cable replacement or wireless audio.
Protocol Architecture
Bluetooth is defined as a layered protocol architecture consisting of core protocols, cable replacement and telephony control protocols, and adopted protocols.
The core protocols form a five-layer stack consisting of the following elements:

Radio - Specifies details of the air interface, including frequency, the use of frequency hopping, modulation scheme, and transmit power.

Baseband - Concerned with connection establishment within a piconet, addressing, packet format, timing, and power control.

 Link manager protocol (LMP) - Responsible for link setup between Bluetooth devices and ongoing link management. This includes security aspects such as authentication and encryption, plus the control and negotiation of baseband packet sizes.
 Logical link control and adaptation protocol (L2CAP) - Adapts upper-layer protocols to the baseband layer. L2CAP provides both connectionless and connection-oriented services.
 Service discovery protocol (SDP) - Device information, services, and the characteristics of the services can be queried to enable the establishment of a connection between two or more
Bluetooth devices.
Protocol Architecture
Bluetooth is defined as a layered protocol architecture consisting of core protocols, cable replacement and telephony control protocols, and adopted protocols.
The core protocols form a five-layer stack consisting of the following elements:

Radio - Specifies details of the air interface, including frequency, the use of frequency hopping, modulation scheme, and transmit power.

Baseband - Concerned with connection establishment within a piconet, addressing, packet format, timing, and power control.

Link manager protocol (LMP) - Responsible for link setup between Bluetooth devices and ongoing link management. This includes security aspects such as authentication and encryption, plus the control and negotiation of baseband packet sizes.

Logical link control and adaptation protocol (L2CAP) - Adapts upper-layer protocols to the baseband layer. L2CAP provides both connectionless and connection-oriented services.

Service discovery protocol (SDP) - Device information, services, and the characteristics of the services can be queried to enable the establishment of a connection between two or more
Bluetooth devices.
RFCOMM is the cable replacement protocol included in the Bluetooth specification. RFCOMM presents a virtual serial port that is designed to make replacement of cable technologies as transparent as possible. Serial ports are one of the most common types of communications interfaces used with computing and communications devices. Hence, RFCOMM enables the replacement of serial port cables with the minimum of modification of existing devices. RFCOMM provides for binary data transport and emulates EIA-232 control signals over the Bluetooth baseband layer. EIA-232 (formerly known as RS-232) is a widely used serial port interface standard.
Bluetooth specifies a telephony control protocol. TCS BIN (telephony control specification—binary) is a bit-oriented protocol that defines the call control signaling for the establishment of speech and data calls between Bluetooth devices. In addition, it defines mobility-management procedures for handling groups of Bluetooth TCS devices.

The adopted protocols are defined in specifications issued by other standards-making organizations and incorporated into the overall Bluetooth architecture. The Bluetooth strategy is to invent only necessary protocols and use existing standards whenever possible. These are the adopted protocols:
 PPP - The point-to-point protocol is an Internet standard protocol for transporting IP datagrams over a point-to-point link;
 TCP/UDP/IP - These are the foundation protocols of the TCP/IP protocol suite;
 OBEX - The object exchange protocol is a session-level protocol developed by the Infrared
Data Association (IrDA) for the exchange of objects. OBEX provides functionality similar to that of HTTP, but in a simpler fashion. It also provides a model for representing objects and operations. Examples of content formats transferred by OBEX are vCard and vCalendar, which provide the format of an electronic business card and personal calendar entries and scheduling information, respectively;

WAE/WAP - Bluetooth incorporates the wireless application environment and the wireless application protocol into its architecture.
Usage Models
A number of usage models are defined in Bluetooth profile documents. In essence, a usage model is a set of protocols that implement a particular Bluetooth-based application. Each profile defines the protocols and protocol features supporting a particular usage model. Following are the highest-priority usage models:

File transfer - The file transfer usage model supports the transfer of directories, files, documents, images, and streaming media formats. This usage model also includes the capability to browse folders on a remote device;

Internet bridge - With this usage model, a PC is wirelessly connected to a mobile phone or cordless modem to provide dial-up networking and fax capabilities. For dial-up networking,
AT commands are used to control the mobile phone or modem, and another protocol stack
(such as PPP over RFCOMM) is used for data transfer. For fax transfer, the fax software operates directly over RFCOMM;

LAN access - This usage model enables devices on a piconet to access a LAN. Once connected, a device functions as if it were directly connected (wired) to the LAN;

Synchronization - This model provides a device-to-device synchronization of PIM (personal information management) information, such as phone book, calendar, message, and note information. IrMC (Ir mobile communications) is an IrDA protocol that provides client/server capability for transferring updated PIM information from one device to another;

Three-in-one phone - Telephone handsets that implement this usage model may act as a cordless phone connecting to a voice base station, as an intercom device for connecting to other telephones, and as a cellular phone;

Headset - The headset can act as a remote device's audio input and output interface.
The History of Bluetooth

A long time ago (historians differ on the exact dates, but it was sometime in the 10th Century C.E.) in a country far, far away, (which was mostly Denmark, with a little bit of Norway added in for flavor,) there lived a Viking king who was principally noted for converting to a foreign religion called Christianity. He was known as Harald Bluetooth, son of Gorm the Old, and he united most of
Denmark before his estranged son, Sven Forkbeard, sent him to Valhalla and took over the family business.
A little more than 1000 years later, succumbing to an attack of Scandinavian pride, the giant
Swedish telecom manufacturer Ericsson decided to honor old, weird Harald by naming its new wireless networking standard after him. It convinced founding Special Interest Group co-partners
Nokia, Toshiba, IBM and Intel that Bluetooth was the right name for the thing and, together, they set off to conquer the air.
By December 1, 1999, 3Com, Lucent, Microsoft and Motorola had joined the Promoter Group -- the folks that were willing to spend money to hype the standard -- and in the neighborhood of 1200 other companies had joined the SIG. (Signing up for membership costs nothing, so it isn't exactly an exclusive club.) Between them, they manged to generate a lot of coverage about Bluetooth in the trade press.
Since the computer trade press mainly consists of English and journalism majors with no hands-on technical background, most of whom make a living re-wording press releases, the fanfare meant very little, however. Meanwhile, actual consumers waited for actual products actually to emerge.
As is often the case with consortium-driven standards -- even "open" ones like Bluetooth -- that took a while. And, as is also often the case, the majority of the early products were aimed not at consumers, but at developers.
While the world waited, grass-roots programmers and engineers began playing with a brand new wireless standard: an offshoot of good, old Ethernet called 802.11b. Like Bluetooth, it used the unlicensed 2.4 - 2.48GHz portion of the radio spectrum, so 802.11b products would work anywhere on the planet without any special license from the local authorities. And it was fast -- much faster than Bluetooth's nominal 1Mbps -- and it had about 10 times the range that Bluetooth's Class 3 devices could boast.
Time passed and soon it was 2001, the beginning of a brand-new millenium. The clumsy-sounding
802.11b moniker had since been supplanted by the less-tongue-twisting name "Wi-Fi" and the cost of its hardware was plunging like a dotcom stock option.
The world was still waiting for Bluetooth -- and, to its SIG partners' dismay, Microsoft announced that the initial release of its forthcoming Windows XP would not include Bluetooth support.
Microsoft's stated reason for omitting the Viking technology from the next release of its flagship OS

was the lack of a critical mass of Bluetooth-enabled devices demanding Windows support. That basically translated to the Redmond behemoth simply acknowledging a conspicuous worldwide lack of user demand for the namesake of Gorm the Old's son.
That's not the only problem with Bluetooth, however.
The Unfaithful Servant
First of all, there's the issue of cost. The low end of the cellular phone hardware market is savagely price-competitive and Bluetooth silicon is still much too expensive to be included in the "gimme" phones that entice a substantial segment of cellular consumers to take the plunge. That creates a chicken-or-egg conundrum, since Bluetooth must become ubiquitous in order to achieve the enconomies of scale that would make it affordable to average consumers -- but first it must universally be adopted in order to achieve those very economies of scale.
Then there's the question of Bluetooth's security -- or, more properly, the gaping holes therein.
Although some have tried to wish the problem away, others have taken a more skeptical view of the fundamental weaknesses in Bluetooth's PIN-based generation of a device's initialization key. Juha T.
Vainio of the Helsinki University of Technology's Department of Computer Science and
Engineering quite rightly points out [4] that a 4-digit PIN offers only 10,000 total possible combinations -- making 4-digit PINs highly susceptible to brute-force cracking techniques -- and the problem is further exacerbated by the well-known user laziness factor that results in a large number of 4-digit PINs being set to 0000.
There's also the possibility that one Bluetooth device may use its exchange of unit keys with a second device and third device to eavesdrop on their "private" conversation -- or even falsely to authenticate itself to the one, masquerading as the other.
That's because, when the first two devices exchange unit keys, they can "decide" to use one or the other as a shared "secret" to generate their link key. When a third device then enters into a key exchange with the second device, and also opens a session with the first device, it reveals its unit key to both. The first device now knows both of the others' "secrets" -- and their entirely-public
48-bit BD_ADDRs -- and it's also synched to the same master clock. Now, merely by faking one of the other box's BD_ADDR, it can generate the public keys necessary to listen in on its two neighbors' "private" traffic. Assuming that the first device can eavesdrop on their conversations, it can also authenticate itself as either device to the other, since that imposture requires no additional data.
The above problem is more than simply theoretical. Bell Labs scientists Marcus Jakobsson and
Susanne Wetzel demonstrated exactly that scenario in the lab, as ZDnet reported on the 8th of
September, 2000.

No Expectations
And, of course, even the weak security Bluetooth currently offers is part and parcel of the techology's price problem. Encryption, decryption and key generation all require significant processor power -- especially when the encryption in question has to take place on the fly and simultaneously be at all robust -- and that doesn't come cheap, particularly when the market is still small.
Of course Wi-Fi has its own security issues -- I'll address them another time -- and it can be just as much of a pain in the posterior to configure as is its Scandanavian competitor. But the distinction between the two technologies is perhaps best illustrated by taking a look at their deployment in the real world.
On that score, Wi-Fi wins, hands down.
Oh sure, RegistryMagic (now known as VoiceFlash) and the Wall Street Holiday Inn made a big fuss last February about their demonstration of Bluetooth for guest check-in during the Internet
World Wireless conference, but a quick check of the current Holiday Inn Wall Street Web site shows nary a mention of the thing today. Perhaps the Venetian resort/hotel/casino will be more enthusiastic about Harald's namesake after it tries its own pilot Bluetooth demo during Fall 2001 Comdex in Las
Vegas.
Perhaps not.
Now We're Getting Somewhere
Meanwhile, Wi-Fi networks are springing up like mushrooms in a cow pasture after a warm Spring rain. Starbucks now has one in every store -- albeit with access priced to discourage all but the investment banking crowd. Likewise, airport terminals around the country are installing 802.11b nets to capture traffic from the hordes of passengers waiting for their too-often delayed or canceled flights.
Businesses are also discovering that Wi-Fi makes a lot of sense in office suites where rapid staff expansion -- or contraction -- causes frequent moves and changes. And there is also a rapidly-growing assortment of free nets, mostly built by the open source community with pooled resources, eager to offer access to all comers.
And that really exemplifies the difference in my mind. There aren't any plans for Bluetooth-based open-access-point networks of which I'm aware. The gear itself remains painfully scarce, prohibitively expensive and seemingly destined to wind up joining ISDN in the Museum of Little
Techologies that Couldn't.

Which may explain why developers are turning off to Bluetooth in droves.
Bring it on home
There are, of course, those who disagree with my gloomy assesment, including some right here on dW Wireless. Big Blue itself is still extremely big on the technology. It offers a Bluetooth PCCard for its latest laptops and it has even gone so far as to release a Bluetooth protocol stack for Linux, to enable the Penguin People to make Tux talk Viking.
The thing is, I still can't help but think that, like Harald, the modern Bluetooth is just going to wind up teeing off so many people who are crucial to its survival that, again like him, it will wind up face-down in a muddy field with an arrow in its back.
That would leave Wi-Fi, starring as Sven Forkbeard, to inherit Harald's kingdom of the air -- and to go on to overthrow HomeRF, in its role as Ethelred the Unready.
But that's another story altogether.
How Bluetooth works
The number of ways to wirelessly connect an increasing number of formerly wired devices is becoming confusing. Wi-Fi, 802.11a, 802.11b, 802.11g, GPRS, IrDA and Bluetooth are just some of the terms now being used to describe different types of wireless connectivity.
This article explains the differences between the main types of wireless connectivity, and explains how Bluetooth can be useful for you.
Different Types of Connectivity Compared
To start off the discussion, here is a table to show the major differences between the main types of wireless connectivity and traditional networking.
Type Speed Range Comments
IrDA
Wi-Fi
802.11a
9.6kb - 115kb (- 4Mb) < 6ft
1Mb - 54Mb
1 - 54Mb see below
50ft - 150ft
Infra-red. The two devices must have their IR ports facing each other. For simple data exchange. Uses very little power.
Wi-Fi refers to any of the three 802.11 types of wireless service below, and to future new subcategories yet to be released. Acts like a regular wired network in most respects.
Either built in or available as add-on cards or adapters for desktop computers.
Not commonly used, uses different frequency

802.11b
802.11g
Bluetooth
GPRS
2.5G
3G
Modem
DSL/Cable
LAN
1 - 11Mb
1 - 54Mb
120kb - 723kb
< 115kb variously up to about wherever suitable
128kb cellphone coverage
2Mb stationary, 384kb moving with good wherever suitable signal, 144kb moving cellphone coverage fast/poor signal
< 56kb
100kb - 1.5Mb
10Mb - 100Mb
100ft - 300ft
120ft - 350ft
30ft - 300ft wherever suitable cellphone coverage not wireless not wireless not wireless than 802.11b/g.
Most common version at present.
The latest version, backwardly compatible with 802.11b.
Class 3 devices (eg in most personal computing type devices) have a short 30ft range, high powered Class 1 devices have the longer range. Either built in or available as add-on cards.
Data service used by GSM cellphones and by some add-on cards for laptops and pda's.
Speed typically about 30kb depending on how many users are sharing the service on each cell at any given time. A 2.5G service.
Various compromise new types of 'always on' data service for cell phones that are better than nothing but not nearly as good as the 3G service that all cell phone companies are hoping to introduce when funding and technology allows.
A largely futuristic technology not much deployed (yet) in the US which promises amazingly fast data transfer. Sprint PCS
Vision and AT&T EDGE (100-130kb) are the closest things to 3G in the US at present.
The 'old fashioned' way to dial up from a computer to the internet.
Not wireless.'Broadband' connections to the internet.
Not wireless. Common type of cabled network in most offices.
So What is Bluetooth?
Bluetooth is a very simple type of wireless networking that can allow up to eight devices to be connected together in a mini-network.
It is very short range in operation, and so is considered to be for 'personal' networking. With a range typically under 30ft, this allows enough distance to perhaps communicate across your office, but not any further. This short range is also its major security feature - anyone wishing to eavesdrop on your
Bluetooth communications would not only need special equipment but would also need to be quite

close to you.
It is a moderately slow type of networking, but it can transfer data sufficiently fast enough for most typical applications.
Bluetooth is hoped to be a very low cost type of networking, and, as it becomes more widespread, the cost of adding Bluetooth to devices should drop down to perhaps no more than an extra $5-10 on the selling price.
Bluetooth is designed to be compatible across a range of very different operating systems and devices, including things that you would not normally think of as being 'computer' type items - for example, some types of headset. Bluetooth networking can enable the headset to connect with other devices such as your phone, your MP3 player, your computer, or your PDA.
A Bluetooth enabled headset would mean that you can leave your cellphone in your pocket or briefcase, but still receive incoming phone calls. If your cellphone supports voice recognition for dialing out, you can even place calls as well as receive them, while never needing to reach for your phone. The safety benefits of this, if you're driving, are obvious.
It is probably better from a health point of view to have a very low powered headset close to your head than it is to have a phone that might be generating 100 or even 300 times as much radio energy close to your head.
Bluetooth can also help different devices to communicate with each other. For example, you might have a phone, a PDA, and a computer. If all three devices have Bluetooth capabilities, then (with the appropriate software on each device) you can probably share contact information between all three devices quickly and conveniently. And you can look up a phone number on your PDA (or laptop) and then place a call direct from the laptop or PDA, without needing to touch your cellphone.
Bluetooth is not a magical solution giving universal connectivity between devices. Each device also needs to have the appropriate software as well as the basic Bluetooth communication capability, and so sometimes the promise and theory of what could be possible is not fully matched by the reality.
For best compatibility, devices should support the Bluetooth 1.1 standard. A new standard - 1.2, was formalized in early November 2003 and this will quickly become the dominant standard.
Bluetooth has been slow to become accepted in the market, but now is starting to become increasingly prevalent. Prices are falling and increasing numbers of devices are offering Bluetooth connectivity. Over one million Bluetooth devices are now being sold every week (although mainly outside the US).

Bluetooth Range
Most Bluetooth devices are described as 'Class 2'. These are very low power (typically 1 milliwatt -
1/1000th of a watt) and have a range of about 10 m (33 ft).
Some devices - for example, some plug in 'dongles' that can be added to to laptop computers - are
Class 1. These have range comparable to that of Wi-Fi, ie, 100 m or 330 ft.
With Bluetooth, short range is actually a benefit, because it reduces the chance of interference between your Bluetooth devices and those belonging to other people nearby.
Devices that Use Bluetooth
A limited, but growing number of devices use Bluetooth at present. Devices that are starting to have
Bluetooth connectivity built in include :

Digital cameras and camcorders

Printers

Scanners

Cell Phones

PDAs

Laptops

Keyboards and Mice

Headsets

In-car handsfree kits

GPS navigation receivers

Home appliances (microwaves, washers, driers, refrigerators)
In addition, add on Bluetooth adapters are available for computers (eg with a USB interface) and for
PDAs (eg SD cards).
Bluetooth connections
Bluetooth is a high-speed, low-power microwave wireless link technology, designed to connect phones, laptops, PDAs and other portable equipment together with little or no work by the user.
Unlike infra-red, Bluetooth does not require line-of-sight positioning of connected units. The technology uses modifications of existing wireless LAN techniques but is most notable for its small size and low cost. The current prototype circuits are contained on a circuit board 0.9cm square, with a much smaller single chip version in development. The cost of the device is expected to fall very fast, from $20 initially to $5 in a year or two. It is envisioned that Bluetooth will be included within equipment rather than being an optional extra. When one Bluetooth product comes within range of another, (this can be set to between 10cm and 100m) they automatically exchange address and capability details. They can then establish a 1 megabit/s link (up to 2 Mbps in the second generation of the technology) with security and error correction, to use as required. The protocols will handle

both voice and data, with a very flexible network topography.
This technology achieves its goal by embedding tiny, inexpensive, short-range transceivers into the electronic devices that are available today. The radio operates on the globally-available unlicensed radio band, 2.45 GHz (meaning there will be no hindrance for international travelers using
Bluetooth-enabled equipment.), and supports data speeds of up to 721 Kbps, as well as three voice channels. The bluetooth modules can be either built into electronic devices or used as an adaptor.
For instance in a PC they can be built in as a PC card or externally attached via the USB port.
Each device has a unique 48-bit address from the IEEE 802 standard. Connections can be point-to-point or multipoint. The maximum range is 10 meters but can be extended to 100 meters by increasing the power. Bluetooth devices are protected from radio interference by changing their frequencies arbitrarily upto a maximum of 1600 times a second, a technique known as frequency hopping. They also use three different but complimentary error correction schemes. Built-in encryption and verification is provided.
Moreover, Bluetooth devices won't drain precious battery life. The Bluetooth specification targets power consumption of the device from a "hold" mode consuming 30 micro amps to the active transmitting range of 8-30 milliamps (or less than 1/10th of a watt). The radio chip consumers only
0.3mA in standby mode, which is less than 3 % of the power used by a standard mobile phone. The chips also have excellent power-saving features, as they will automatically shift to a low-power mode as soon as traffic volume lessens or stops.
But beyond untethering devices by replacing the cables, Bluetooth radio technology provides a universal bridge to existing data networks, a peripheral interface, and a mechanism to form small private ad hoc groupings of connected devices away from fixed network infrastructures. Designed to operate in a noisy radio frequency environment, the Bluetooth radio uses a fast acknowledgment and frequency hopping scheme to make the link robust. Bluetooth radio modules avoid interference from other signals by hopping to a new frequency after transmitting or receiving a packet.
Compared with other systems operating in the same frequency band, the Bluetooth radio typically hops faster and uses shorter packets. This makes the Bluetooth radio more robust than other systems.
Short packages and fast hopping also limit the impact of domestic and professional microwave ovens. Use of Forward Error Correction (FEC) limits the impact of random noise on long-distance links. The encoding is optimized for an uncoordinated environment.
Bluetooth guarantees security at the bit level. Authentication is controlled by the user by using a
128 bit key. Radio signals can be coded with 8 bits or anything upto 128 bits. The Bluetooth radio transmissions will conform to the safety standards required by the countries where the technology will be used with respect to the affects of radio transmissions on the human body. Emissions from
Bluetooth enabled devices will be no greater than emissions from industry-standard cordless phones.
The Bluetooth module will not interfere or cause harm to public or private telecommunications

network.
The Bluetooth baseband protocol is a combination of circuit and packet switching. Slots can be reserved for synchronous packets. Each packet is transmitted in a different hop frequency. A packet nominally covers a single slot, but can be extended to cover up to five slots. 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. It is thus possible to transfer the date asynchronously whilst at the same time talking synchronously at the same time.
Each voice channel supports 64 kb/s synchronous (voice) link. The asynchronous channel can support an asymmetric link of maximally 721 kb/s in either direction while permitting 57.6 kb/s in the return direction, or a 432.6 kb/s symmetric link.
Bluetooth Operation Modes
An interesting aspect of the technology is the instant formation of networks once the bluetooth devices come in range to each other. A piconet is a collection of devices connected via Bluetooth technology in an ad hoc fashion. A Piconet can be a simple connection between two devices or more than two devices. Multiple independent and non-synchronized piconets can form a scatternet. Any of the devices in a piconet can also be a member of another by means of time multiplexing. i.e a device can be a part of more than one piconet by suitably sharing the time. The Bluetooth system supports both point-to-point and point-to-multi-point connections. When a device is connected to another device it is a point to point connection. If it is connected to more that one (upto 7 ) it is a point to multipoint connection. Several piconets can be established and linked together ad hoc, where each piconet is identified by a different frequency hopping sequence. All users participating on the same piconet are synchronized to this hopping sequence. If a device is connected to more than one piconet it communicates in each piconet using a different hopping sequence. A piconet starts with two connected devices, such as a portable PC and cellular phone, and may grow to eight connected devices. All Bluetooth devices are peer units and have identical implementations.
However, when establishing a piconet, one unit will act as a master and the other(s) as slave(s) for the duration of the piconet connection. In a piconet there is a master unit whose clock and hopping sequence are used to synchronize all other devices in the piconet. All the other devices in a piconet that are not the master are slave units. A 3-bit MAC address is used to distinguish between units participating in the piconet. Devices synchronized to a piconet can enter power-saving modes called
Sniff and hold mode, in which device activity is lowered. Also there can be parked units which are synchronized but do not have a MAC addresses. These parked units have a 8 bit address, therefore there can be a maximum of 256 parked devices.
Voice channels use either a 64 kbps log PCM or the Continuous Variable Slope Delta Modulation
(CVSD) voice coding scheme, and never retransmit voice packets. The voice quality on the line interface should be better than or equal to the 64 kbps log PCM. The CVSD method was chosen for its robustness in handling dropped and damaged voice samples. Rising interference levels are experienced as increased background noise: even at bit error rates up 4%, the CVSD coded voice is

quite audible.
Bluetooth and the Internet
Bluetooth can be used to connect between a device that has internet connectivity and another device that does not, for example, you might use Bluetooth to connect from your PDA to your laptop, and then your laptop might use Wi-Fi to connect to a Wi-Fi router and from there you would be connected to the internet.
Sometimes when buying a PDA you may find yourself with an apparent 'either//or' choice - either buy a device with Bluetooth; or a device with Wi-Fi capability. In such a case, it would seem at first glance that if you want to connect to the internet - especially while traveling out of your office,
Wi-Fi would be a better choice.
However, this is not quite such a clear choice. Wi-Fi 'hotspots' are few and far between. A much better approach might be to get Bluetooth on your PDA and also on your cellphone and use
Bluetooth to connect to your cellphone and then connect through your cellphone and out to the internet from there. I use T-Mobile's GPRS service - they offer unlimited connect time and unlimited bandwidth usage for only $20/month extra on top of my regular cellphone service (and
GPRS connection time does not count against my monthly minutes - it truly is unlimited for only
$20/month).
In my opinion, this is the perfect solution. GPRS coverage is much more widespread than Wi-Fi coverage, and while it is not fast, it is adequate for simple mail sending/receiving, instant messaging, and occasional web browsing such as you're likely to do on a PDA. Although I also have Wi-Fi in my laptop, these days I never use it, and indeed if I'm sitting in a Starbucks with my laptop, I'll be connecting to the internet not through the Wi-Fi in Starbucks, but via Bluetooth and my cellphone's
GPRS!
Which is better - Bluetooth or Wi-Fi
Wi-Fi is primarily used as an alternate to traditional cable based networks. It has a longer range than
Bluetooth, and supports faster data transfer speeds, and so it might seem better than Bluetooth.
But, in reality, Bluetooth and Wi-Fi have different purposes. Bluetooth is intended for limited data transfer between many different types of devices, Wi-Fi is more focussed on faster data transfer between computers on a network.
One of the distinctive elements of Bluetooth is that is uses very much less power than Wi-Fi. Class
2 devices (such as are in PDAs, phones, headsets, etc) transmit a very low power signal (1 mW) and only transmit intermittently when in standby mode, saving even more power. Wi-Fi, on the other hand, consumes a great deal of power, and so for any type of portable battery operated device,
Bluetooth will allow for substantially more battery life than would Wi-Fi.

If you're simply wanting to swap data between different devices in your office and elsewhere on a casual and occasional basis, then - assuming that the software and Bluetooth hardware is available -
Bluetooth is probably a better choice for you. If you need more range, and higher bandwidth; perhaps if you want to connect computers into your office LAN, then Wi-Fi is a better choice for you.
Bluejacking
Bluejacking is a moderately harmless 'fun' type trick that some people have discovered. It involves sending messages from your Bluetooth device to other people close to you with Bluetooth devices, and surprising the recipient in the process.
The easiest way to Bluejack is to create a new phonebook contact, with the message you want to send in the name field. Then, in a busy place with lots of people (so that there is a chance that someone might have a Bluetooth enabled phone or PDA), choose the option to send your new contact via Bluetooth. Your phone or PDA will then search for all Bluetooth devices in range, and present you with a list. Choose whichever device you wish from the list and send it. The recipient will get a message asking if they wish to accept your contact, and showing the text you entered as the contact's name (eg something like 'Bad weather today isn't it' or whatever else you wish to say).
If you're planning to enjoy Bluejacking (or Toothing, below) you'll probably want to get your eye in to guessing how far away 10 m/33 ft is so as to know how many people and devices might be within range.
Toothing
Harmless Bluejacking didn't take long to evolve into a more goal oriented social activity, now known as 'toothing', whereby people communicate to other Bluetooth equipped people around them, trying to arrange casual and immediate trysts.
Summary
Bluetooth promises to be a low cost, convenient, and simple way of enabling your various computer devices to talk to each other and to their peripherals. The reality has yet to match the promise, but
Bluetooth is becoming more widespread and functional every day. Bluetooth is almost certainly in your future.
Bluetooth is not a competitor to Wi-Fi. It offers different functionality for different purposes.
How Bluetooth Short Range Radio Systems Work
If you have the normal complement of electronic equipment in your home, then you know all of the different ways that devices connect to one another. For example:

 Many desktop computer systems have a CPU unit connected to a mouse, a keyboard, a printer and so on.
 A personal digital assistant (PDA) will normally connect to the computer with a cable and a docking cradle.
 Any TV is normally connected to a VCR and a cable box, with a remote control for all three components.
 A cordless phone connects to its base unit with radio waves, and it may have a headset that connects to the phone with a wire.
 In a stereo system, the CD player, tape player and record player connect to the receiver, which connects to the speaker.
The art of connecting things is becoming more and more complex every day. Oftentimes we feel as if we need a Ph.D. in electrical engineering just to set up the electronics in our houses! We will look at a completely different way to form the connections called Bluetooth. Bluetooth is wireless and automatic, and has a number of interesting features that should simplify our daily lives!
The Problems
When any two devices need to talk to each other, they have to agree on a number of points before the conversation can begin. The first point of agreement is physical: Will they talk over wires, or through some form of wireless signals? If they use wires, how many are required -- 1, 2, 8, 25 or more? Once the physical attributes are decided, several more questions arise:

Information can be sent one bit at a time in a scheme called serial communications, or in groups of bits (usually 8 or 16 at a time) in a scheme called parallel communications. A desktop computer uses both serial and parallel communications to talk to different devices:
Modems, mice and keyboards tend to talk through serial links, while printers tend to use parallel links.

All the parties in an electronic discussion need to know what the bits mean and whether the message they receive is the same message that was sent. In most cases, this means developing a language of commands and responses known as a protocol. Some types of products have a standard protocol used by virtually all companies so that the commands for one product will tend to have the same effect on another. Modems fall into this category. Other product types each speak their own language, which means commands intended for one specific product will seem gibberish if received by another. Printers are like this, with multiple standards like PCL and PostScript.

Companies that manufacture computers, entertainment systems and other electronic devices have realized that the incredible array of cables and connectors involved in their products makes it difficult for even expert technicians to correctly set up a complete system on the first try. Setting up computers and home entertainment systems becomes terrifically complicated when the person buying the equipment has to learn and remember all the details to connect all the parts. In order to make home electronics more user friendly, we need some better way for all the electronic parts of our modern life to talk to each other. That's where Bluetooth comes

in.
Bluetooth Basics
Bluetooth is a new standard developed by a group of electronics manufacturers that will allow any sort of electronic equipment -- from computers and cell phones to keyboards and headphones -- to make its own connections, without wires, cables or any direct action from a user. Bluetooth is intended to be a standard that works at two levels:
 It provides agreement at the physical level -- Bluetooth is a radio-frequency standard.
 It also provides agreement at the next level up, where products have to agree on when bits are sent, how many will be sent at a time and how the parties in a conversation can be sure that the message received is the same as the message sent.

The companies belonging to the Bluetooth Special Interest Group, and there are more than
1,000 of them, want to let Bluetooth's radio communications take the place of wires for connecting peripherals, telephones and computers.
There are already a couple of ways to get around using wires. One is to carry information between components via beams of light in the infrared spectrum. Infrared refers to light waves of a lower frequency than human eyes can receive and interpret. Infrared is used in most television remote control systems, and with a standard called IrDA (Infrared Data Association) it's used to connect some computers with peripheral devices. For most of these computer and entertainment purposes, infrared is used in a digital mode -- the signal is pulsed on and off very quickly to send data from one point to another.
Infrared communications are fairly reliable and don't cost very much to build into a device, but there are a couple of drawbacks. First, infrared is a "line of sight" technology. For example, you have to point the remote control at the television or DVD player to make things happen. The second drawback is that infrared is almost always a "one to one" technology. You can send data between your desktop computer and your laptop computer but not to your laptop computer and your PDA at the same time.
These two qualities of infrared are actually advantageous in some regards. Because infrared transmitters and receivers have to be lined up with each other, interference between devices is uncommon. The one-to-one nature of infrared communications is useful in that you can make sure a message goes only to the intended recipient, even in a room full of infrared receivers.
The second alternative to wires, cable synchronizing, is a little more troublesome than infrared. If you have a Palm Pilot, a Windows CE device or a Pocket PC (a class of computer called Personal
Digital Assistant, or PDA for short), you know about synchronizing data. In synchronizing, you attach the PDA to your computer (usually with a cable), press a button and make sure that the data on the PDA and the data on the computer match. It's a technique that makes the PDA a valuable tool for many people, but synchronizing the PDA with the computer and making sure you have the correct cable or cradle to connect the two can be a real hassle.

Bluetooth is intended to get around the problems that come with both infrared and cable synchronizing systems. The hardware vendors have developed a specification for a very small radio module to be built into computer, telephone and entertainment equipment. From the user's point of view, there are three important features to Bluetooth:
 It's wireless. When you travel, you won't have to worry about keeping track of a briefcase full of cables to attach all your components, and you can design your office without wondering where all the wires will go.
 It's inexpensive.
You don't have to think about it. Bluetooth doesn't require you to do anything special to make it work. The devices find one another and strike up a conversation without any user input at all.
Bluetooth communicates on a frequency of 2.45 gigahertz, which has been set aside by international agreement for the use of industrial, scientific and medical devices (ISM). A number of devices that you may already use take advantage of this same radio-frequency band. Baby monitors, garage-door openers and the newest generation of cordless phones all make use of frequencies in the ISM band.
Making sure that Bluetooth and these other devices don't interfere with one another has been a crucial part of the design process.
Avoiding Interference
One of the ways Bluetooth devices will avoid interfering with other systems is by sending out very weak signals of 1 milliwatt. By comparison, the most powerful cell phones can transmit a signal of
3 watts. The low power limits the range of a Bluetooth device to about 10 meters, cutting the chances of interference between your computer system and your portable telephone or television.
Even with the low power, the walls in your house won't stop a Bluetooth signal, making the new standard useful for controlling several devices in different rooms.
With many different Bluetooth devices in a room, you might think they'd interfere with one another, but it's unlikely that several devices will be on the same frequency at the same time because
Bluetooth uses a technique called spread-spectrum frequency hopping. In this technique, a device will use 79 individual randomly chosen frequencies within a designated range, changing from one to another on a regular basis. In the case of Bluetooth, the transmitters change frequencies 1,600 times every second, meaning that more devices can make full use of a limited slice of the radio spectrum. Since every Bluetooth transmitter uses spread-spectrum transmitting automatically, it's unlikely that two transmitters will be on the same frequency at the same time. This same technique minimizes the risk that portable phones or baby monitors will disrupt Bluetooth devices since any interference on a particular frequency will last only a tiny fraction of a second.
When new Bluetooth-capable devices come within range of one another, an electronic conversation will take place to determine whether they have data to share or whether one needs to control the other. The user doesn't have to press a button or give a command -- the electronic conversation

happens automatically. Once the conversation has occurred, the devices -- whether they're part of a computer system or a stereo -- form a network. Bluetooth systems create a Personal-Area Network
(PAN) or "piconet" that may fill a room or may encompass no more distance than that between the cellphone on a belt-clip and the headset you're wearing. Once a piconet is established, the members randomly hop frequencies in unison so they stay in touch with one another and avoid other piconets that may be operating in the same room.
An Example
Let's take a look at how the Bluetooth frequency hopping and personal-area network keep systems from becoming confused. Let's say you've got a typical modern living room with the typical modern stuff inside. There's an entertainment system with a stereo, a DVD player, a satellite TV receiver and a television; a cordless telephone; and a personal computer. Each of these systems uses
Bluetooth, and each forms its own piconet to talk between main unit and peripheral.
The cordless telephone has one Bluetooth transmitter in the base and another in the handset. The manufacturer has programmed each unit with an address that falls into a range of addresses it has established for a particular type of device. When the base is first turned on, it sends radio signals asking for a response from any units with an address in a particular range. Since the handset has an address in the range, it responds and a tiny network is formed. Now, even if one of these devices should receive a signal from another system, it will ignore it since it's not from within its network.
The computer and entertainment system go through similar routines, establishing networks among addresses in ranges established by manufacturers. Once the networks are established, the systems begin talking among themselves. Each piconet hops randomly through the available frequencies, so all of the piconets are completely separated from one another.
Now the living room has three separate networks established, each one made up of devices that know the address of transmitters it should listen to, and the address of receivers it should talk to.
Since each network is changing the frequency of its operation thousands of times a second, it's unlikely that any two networks will be on the same frequency at the same time. If it turns out that they are, then the resulting confusion will only cover a tiny fraction of a second, and software designed to correct for such errors will weed out the confusing information and get on with the network's business.
Most of the time, a network or communications method either works in one direction at a time, called asynchronous communication, or in both directions simultaneously, called synchronous communication. A speakerphone that lets you either listen or talk, but not both, is an example of asynchronous communication, while a regular telephone handset is a synchronous device. Because
Bluetooth is designed to work in a number of different circumstances, it can be either synchronous or asynchronous. The cordless telephone is an example of a use that will call for a synchronous, or two-way, link, and Bluetooth can send data at more than 64,000 bits per second in a synchronous link -- a rate high enough to support several human voice conversations. If a particular use calls for

an asynchronous link -- connecting to a computer modem, for example -- Bluetooth can transmit up to 721 Kilo bits per second in one direction, with 57.6 Kbps in the other. If the use calls for the same speed in both directions, a link with 432.6 Kbps capacity in each direction can be made.
Computer manufacturers are planning to include Bluetooth in a number of products. Cell phone and entertainment product designers are also making plans for the standard because Bluetooth includes three voice channels in each piconet. Since Bluetooth doesn't require a physical adapter, manufacturers are planning cellular modems, headsets and other devices that tie telephone and data together.
Bluetooth compared to other wireless technologies
Bluetooth technology is one solution for wireless personal area networks (WPANs). Two other technologies of interest, namely IrDA and HomeRF, are described here. The IEEE™ 802.15 standards work also addresses WPANs and the IEEE™ 802.11 working group addresses wireless
LANs; this work is discussed separately in other articles.
We choose to discuss HomeRF and IrDA because they have interesting relationships with Bluetooth wireless technology. Strictly speaking, these technologies are not limited to the WPAN domain, although they can be considered part of it. Certainly there are other technologies that could be employed in the WPAN domain: wearable computing devices are becoming more popular and could be considered WPANs or elements of WPANs. IrDA is relevant for comparison to Bluetooth wireless communications because the two technologies share some similar usage models and protocols. HomeRF, like Bluetooth wireless technology, is a relatively short-range RF communications scheme that operates in the 2.4 gigahertz (GHz) industrial, scientific, and medical
(ISM) band. These technologies are described next, with the objective of providing a context in which Bluetooth wireless communications as a WPAN technology can be better understood.
IrDA and Bluetooth Wireless Communication Compared
IrDA is an infrared wireless communication technology developed by the Infrared Data Association.
Here we compare and contrast specific features of these technologies.
IrDA is a specific use of infrared light as a communications medium; Bluetooth technology is a specific use of radio waves as a communications medium. Like the Bluetooth special interest group
(SIG), the IrDA specifies hardware and software protocols for wireless communication intended to promote interoperable applications.
Although both technologies are wireless, they use different parts of the electromagnetic spectrum with quite different signal propagation characteristics. Because infrared uses the nonvisible infrared light spectrum, IrDA communication is blocked by obstacles that block light (such as walls, doors, briefcases, and people). The signal wavelength used with Bluetooth communication (about 12.5 cm,

at its associated frequency of 2.4GHz) is three orders of magnitude greater than that of IrDA. At this wavelength, radio frequency (RF) communications can penetrate many of these sorts of obstacles.
Recent advances in infrared technology have enabled more diffuse transmission patterns, although much of the IrDA equipment in use today uses a relatively narrowly focused beam, which usually requires that the two devices engaged in IrDA communication be aligned with (pointed at) each other. RF transmission patterns radiate in some pattern (ideally, spherical) around the radio antenna, so any two devices within range can communicate with each other, whether or not they are "pointed at" each other (in fact, the second device might not be visible at all to the user of the first device, as it could be in another room behind doors and walls or even on another floor of a building, for example).
The initial IrDA data rate of 115 kilobits per second (Kbps) has now been enhanced to 1 megabit per second (Mbps), comparable to that of the first Bluetooth radios. Today, IrDA can achieve data rates of up to 4Mbps, with even higher rates already specified and beginning to be implemented.
Bluetooth wireless communication occurs at a raw data rate of 1Mbps, with higher speeds being investigated.
The effective range for Bluetooth wireless communication is about 10 meters using the standard 0 dBm radio. With optional power amplification of up to 20 dBm, range on the order of 100 meters can be achieved. IrDA range is about 1 meter and, as noted already, generally requires a line of sight to establish a connection.
Both Bluetooth wireless technology and IrDA communication are optimized for low power consumption and low cost. Compared to other RF communication technologies, Bluetooth communication consumes very little power and is projected to have very low module costs in the foreseeable future. However, IrDA consumes significantly less power than Bluetooth technology, because far less power is required for infrared transceivers than for RF transceivers. IrDA hardware also already is less expensive than Bluetooth radio modules, owing largely to the maturity and wide deployment of IrDA.
This brief discussion indicates that IrDA technology compares favorably to Bluetooth technology in the areas of cost, power, and data rate. However, Bluetooth technology can add convenience and user mobility by relaxing the device alignment and line of sight requirements of IrDA communications. This illustrates an additional design parameter for WPANs: enhanced device usability enabled by the unconscious application of communications technology. RF technologies are well suited for this aspect of WPANs, and Bluetooth wireless technology further emphasizes device usability characteristics in the profiles. All of these considerations, both objective and subjective, may influence the choice of a WPAN technology for a particular application.
HomeRF and Bluetooth Wireless Communication Compared
HomeRF is a wireless radio communications technology developed by the HomeRF working group,

an industry consortium not unlike the Bluetooth SIG (in fact, several companies participate in both groups). Like Bluetooth wireless communications, HomeRF operates in the 2.4GHz ISM band, using radio waves for relatively short-range voice and data communication among various types of devices. The impetus for developing the HomeRF technology was to provide a solution for wireless in-home networks.
HomeRF and Bluetooth technologies have many parallels. Both were developed at roughly the same time, and both operate in the unlicensed 2.4GHz ISM band for RF communications. Each one enables both voice and data traffic; and each one is designed for relatively short-range, low-power operation. The first products using these technologies were available by 2001.
The two technologies do have differences, though. In addition to technical differences such as packet structure and protocol layers that are not detailed here, other characteristics distinguish them.
HomeRF was designed from the outset for home networking environments, whereas Bluetooth technology is optimized for use with WPANs and mobile. HomeRF communication range is about
50 meters (designed to cover a typical home), which is greater than the 10-meter range of the typical Bluetooth radio. Initially, the data rates of the two technologies were similar at about 1Mbps; recently, HomeRF version 2.0 has specified data rates up to 10Mbps. With all other factors being equal, higher data rates and greater range require more power consumption, so HomeRF often could require more power, although both technologies include power-saving schemes in their respective specifications.
Like any technologies that operate in the same frequency spectrum, HomeRF and Bluetooth wireless communications can interfere with each other. Radio frequency interference is to be expected in the unlicensed 2.4GHz ISM band. One means to mitigate RF interference is the use of frequency-hopping spread-spectrum (FHSS), and both of these technologies use FHSS as a way to deal with undesired interference. Other techniques also can be used to minimize the problem of RF interference among these and other RF emitters in the ISM band.
WPAN Technology Summary
Bluetooth wireless communications is one instance of a WPAN technology. Other technologies also can be used in WPANs, and we reviewed two of these, IrDA and HomeRF.
These and other mechanisms can be employed to implement WPANs, but each is optimized for specific usage, applications, or domains. Although in some respects, certain technologies might be viewed as competing in the WPAN space, we believe that at least the ones discussed here are complementary to each other. Each has specific advantages that make it particularly suitable for certain environments or applications, and we expect that multiple WPAN technologies will exist in the foreseeable future.
Bluetooth FAQ

Q: What is Bluetooth?
A: Bluetooth is the name for a short-range radio frequency (RF) technology that operates at 2.4
GHz and is capable of transmitting voice and data. The effective range of Bluetooth devices is 32 feet (10 meters). Bluetooth transfers data at the rate of 1 Mbps, which is from three to eight times the average speed of parallel and serial ports, respectively.
Q: Why is the technology called Bluetooth?
A: The heart of the Bluetooth brand identity is the name, which refers to the Danish king Harald
"Bluetooth" Blaatand who unified Denmark and Norway. In the beginning of the Bluetooth wireless technology era, Bluetooth was aimed at unifying the telecom and computing industries.
Q: How is Bluetooth used?
A: Bluetooth can be used to wirelessly synchronize and transfer data among devices. Bluetooth can be thought of as a cable replacement technology. Typical uses include automatically synchronizing contact and calendar information among desktop, notebook and palmtop computers without connecting cables. Bluetooth can also be used to access a network or the Internet with a notebook computer by connecting wirelessly to a cellular phone.
Q: What is the future direction of the Bluetooth standard?
A: At this time, we anticipate the Bluetooth SIG to evolve the Bluetooth technology to provide greater bandwidth and distances, thus increasing the potential platforms and applications used in the emerging personal area networking marketplace
Q: Where can I find more information on Bluetooth?
A: The following web sites are useful Bluetooth resources:
www.bluetooth.com
www.xircom.com
www.ericsson.com/bluetooth
Q: How secure is a Bluetooth network?
A: Bluetooth is extremely secure in that it employs several layers of data encryption and user authentication measures. Bluetooth devices use a combination of the Personal Identification
Number (PIN) and a Bluetooth address to identify other Bluetooth devices. Data encryption (i.e.,
128-bit) can be used to further enhance the degree of Bluetooth security. The transmission scheme
(FHSS) provides another level of security in itself. Instead of transmitting over one frequency within the 2.4 GHz band, Bluetooth radios use a fast frequency-hopping spread spectrum (FHSS) technique, allowing only synchronized receivers to access the transmitted data.
Q: What is Frequency-Hopping Spread Spectrum (FHSS)?
A: Frequency-Hopping Spread-Spectrum (FHSS) is a spread spectrum modulation scheme that uses a narrowband carrier that changes frequency in a pattern known to both transmitter and receiver.

Properly synchronized, they maintain a single logical channel. To an unintended receiver, FHSS appears as short-duration impulse noise. More simply, the data is broken down into packets and transmitted to the receiver of other devices over numerous "hop frequencies" (79 total) in a pseudo random pattern. Only transmitters and receivers that are synchronized on the same hop frequency pattern will have access to the transmitted data. The transmitter switches hop frequencies 1,600 times per second to assure a high degree of data security.
Q: Will other RF (Radio Frequency) devices interfere with Bluetooth Devices?
A: No. Bluetooth radios operate on the unlicensed 2.4 GHz (Industrial, Scientific and Medical) frequency band that is shared among other devices (microwave ovens, cordless phones, garage door openers, etc. ). Bluetooth radios switch frequencies at such a rapid pace (1,600 times per second) and the data packets are so small that interference from other RF sources is highly unlikely.
Bluetooth is a robust communication system.
Q: Will Bluetooth and Wireless LAN (WLAN) interfere with each other?
A: No, both Bluetooth and WLAN can co-exist. Since Bluetooth devices use Frequency Hopping and most WLANs use Direct Sequence Spreading techniques they each appear as background noise to the other and should not cause any perceivable performance issues.
Q: What is the data throughput speed of a Bluetooth connection?
A: Bluetooth transfers data at a rate of 721 Kbps, which is from three to eight times the average speed of parallel and serial ports, respectively. This bandwidth is capable of transmitting voice, data, video and still images.
Q: What is the range of Bluetooth transmitter/receivers?
A: Bluetooth is designed for very low power use, and the transmission range will only be 10m, about 30ft. High-powered Bluetooth devices will enable ranges up to 100m (300ft). Considering the design philosophy behind Bluetooth, even the 10m range is adequate for the purposes Bluetooth is intended for. Later versions of the Bluetooth spec may allow longer ranges.
Q: What kind of encryption will be used for Bluetooth security?
A: The Bluetooth specification 1.0 describes the link encryption algorithm as a stream cipher using
4 LFSR (linear feedback shift registers). The sum of the width of the LFSRs is 128, and the spec says "the effective key length is selectable between 8 and 128 bits". This arrangement allows
Bluetooth to be used in countries with regulations limiting encryption strength, and "facilitate a future upgrade path for the security without the need for a costly redesign of the algorithms and encryption hardware" according to the Bluetooth specification. Key generation and authentication seems to be using the 8-round SAFER+ encryption algorithm. The information available suggests that Bluetooth security will be adequate for most purposes; but users with higher security requirements will need to employ stronger algorithms to ensure the security of their data.

Q: Is Bluetooth practical for use with mobile devices?
A: Yes. One concern for mobile computing users is power consumption. Bluetooth radios are very low power, drawing as little as 0.3mA in standby mode and 30mA during sustained data transmissions. Bluetooth radios alternate among power-saving modes in which device activity is lowered to maximize the mobile power supply.
Q: What is a Personal Area Network (PAN)?
A: A Personal Area Network is another name for a Bluetooth Piconet.
Q: What is HomeRF ?
A: HomeRFlike Bluetooth is a specification for connectivity and mobility in a home-like environment. HomeRF Working Group has developed a specification for wireless communications in the home called the Shared Wireless Access Protocol (SWAP). This specification is not free and comes at a cost of $500 . you can find more information at www.homerf.org website.
Q: Are different brands of Bluetooth products compatible?
A: Yes. They have to. The Bluetooth Logo Certification Program requires Bluetooth products to interoperate with products manufactured by other vendors; those products that don't interoperate will not be allowed to use the Bluetooth logo.
Q: Can Bluetooth products be used on aircraft?
A: The Federal Aviation Administration (FAA) and other aviation regulatory bodies worldwide are currently reviewing the use of Bluetooth products on private and commercial aircraft. In the U.S. the FAA is the governing body to grant approval for Bluetooth product use on aircraft; therefore, we must defer to their impending ruling.
Q: What companies are involved in the Bluetooth initiative?
A: Global technology leaders Ericsson, Nokia, IBM, Intel and Toshiba founded the Bluetooth SIG in 1998. These companies are now supported by over 1,000 other organizations with a wide range of expertise, including Widcomm, Inc.
Q: What types of companies are likely to adopt or promote Bluetooth technology?
A: Companies likely to adopt this technology include, but are not limited to, software developers, network vendors, silicon vendors, peripheral and camera manufacturers, mobile PC and handheld device manufacturers, consumer electronics manufacturers and more.
Q: Are there any patents or licenses involved?
A: Yes, there are several patents on different parts of the technology. Because of this, all licensees will have to sign a zero cost license agreement to cover IP and naming.
Q: What is the estimated size of the market?

A: Market research studies at several leading companies involved with Bluetooth technology expect a total of 250 million Bluetooth-enabled devices, ranging from headsets to mobile and desktop computers, will be shipped in 2002.
Q: Where can I get Bluetooth specification ? Is it license free ?
A: Bluetooth specification can be downloaded from Bluetooth.com which has more comprehensive information about Bluetooth.com and its SIG. It is totally free and no license is required to use it.
Q: Is Bluetooth an IEEE standard, like IEEE 802.11 and Ethernet?
A: Being an IEEE standard will be a big plus to widespread adoption of Bluetooth, and IEEE
802.15 working group for personal area networks (PAN) announced that they will be adopting
Bluetooth as the IEEE 802.15 standard.
Q: How much will Bluetooth devices cost?
A: Bluetooth devices are expected to cost $20 initially (first half of 2000); but will drop to around
$5 with widespread adoption and economies of scale.
Q: What is it - a technology, a standard, an initiative, or a product?
A: Bluetooth wireless technology is a de facto standard, as well as a specification for small-form factor, low-cost, short range radio links between mobile PCs, mobile phones and other portable devices. The Bluetooth Special Interest Group is an industry group consisting of leaders in the telecommunications, computing, and networking industries that are driving development of the technology and bringing it to market.