Home > Articles > Networking > Wireless/High Speed/Optical

Bluetooth FAQs

📄 Contents

  1. Introduction
  2. Bluetooth FAQs According to Miller
  3. Summary
  • Print
  • + Share This

Bluetooth FAQs According to Miller

Can you tell me how the name "Bluetooth" came about?

This is an interesting story that is becoming more commonly known. In our book Bluetooth Revealed, co-author Chatschik Bisdikian and I include a section on this topic (and, in fact, on most of the topics addressed in this FAQ). Briefly, the Bluetooth technology was named after tenth-century Danish King Harald Blåtand, whose surname loosely translates to "blue tooth." King Harald was instrumental in uniting parts of Scandinavia, so some of the people originally involved with the technology thought that it would be neat to name it after him because Bluetooth technology is intended to unite devices, companies, and industries.

Who developed the technology?

The Bluetooth technology, as described in the specification, was developed by the Bluetooth Special Interest Group (SIG). Ericsson is credited with the initial research and invention of the concepts that became Bluetooth technology. The SIG today consists of more than 2,000 member organizations. The core, or "promoter" group, in the SIG is composed of 3Com®, Ericsson®, Intel®, IBM, Lucent®, Microsoft®, Motorola®, Nokia,® and Toshiba®. The official SIG Web site, where much more information can be found, is http://www.bluetooth.com/.

Where is the Bluetooth headquarters?

Because Bluetooth is developed and maintained by a special interest group, there is no Bluetooth corporate entity and thus no "Bluetooth headquarters." The SIG is a group bound by legal agreements, but not a company unto itself. Thus, you can't buy "Bluetooth stock."

What is the range for Bluetooth wireless communication?

The "default" 0dBm Bluetooth radio is intended to operate at a nominal range of 10 meters. A power-amplified 20dBm radio is also specified, with a range of about 100 meters. Of course, because Bluetooth wireless technology uses RF communications, the range can be affected by obstacles in the communication path that might obstruct or refract the radio waves. Most of the usage cases included in the version 1.0 specification assume a 10-meter radio range.

Why don't you just say "Bluetooth" in your writings instead of "Bluetooth wireless communication" or "Bluetooth technology"?

The term Bluetooth is trademarked along with its associated figure mark, or logo. As noted here, Ericsson is the owner of the trademark and licenses it to SIG promoters, associates, and adopters. The Bluetooth word mark and figure mark will play an important role in communicating brand messages to consumers and others. Thus, the SIG has deemed it important to protect the Bluetooth brand image and has developed guidelines for the use of the term Bluetooth and its associated figure mark. Many of these guidelines, noted in the Bluetooth Brand Book, apply primarily for use with products and product packaging. One set of guidelines suggests that Bluetooth be used as a descriptive adjective rather than as a standalone noun, and I always try to be consistent with this guideline.

Aren't there some restrictions on where I can use Bluetooth devices?

Bluetooth technology is designed to operate anywhere in the world. Because they operate within the globally unlicensed 2.4GHz spectrum, Bluetooth devices should be capable of being used unmodified throughout the globe. However, some countries do—or recently did—restrict the use of this spectrum, reserving part of it for special use and making only a portion of the spectrum available for unlicensed use (and thus limiting the number of channels over which Bluetooth communications could occur).

Due partly to discussions in which SIG representatives participated, nearly all of these restrictions have been lifted or will be lifted in the near future. In fact, since the SIG was formed and started to address this issue, several countries, including Japan and France, have made or have announced that they will make the entire 2.4GHz spectrum available for unlicensed use. There are very few remaining cases in which special considerations apply, and even in these cases, partial-spectrum availability primarily just limits bandwidth; thus, the end user might see decreased performance but still should be able to use his or her Bluetooth device.

Given recent reports about possible health issues with cellular phones, are there similar concerns with Bluetooth technology?

Some studies have indicated increased health risk from prolonged exposure to RF radiation, such as might result from the use of cellular phones. Although many may not consider the overall body of available evidence to be conclusive, the main point to keep in mind about Bluetooth technology is that it operates at a significantly lower power output level than do typical cellular phones. Bluetooth transmissions are typically at least an order of magnitude lower in power output than cellular radio transmissions. Of course, medical and radio experts (of which I am neither) are best positioned to discuss details on this subject, but many people feel that by the very nature of its low-power transmissions, Bluetooth technology has different characteristics than cellular radio technology and intuitively might seem to be of less concern.

Are Bluetooth communications secure?

Security tends to be present in degrees rather than in absolute terms. One goal for Bluetooth wireless communication is to enable security at least as good as that provided by typical cables because a primary application of Bluetooth technology is cable replacement. Toward that end, the SIG has specified several security measures that may be employed in various situations, and the Bluetooth profiles suggest when these security measures might be or should be employed in certain usage scenarios.

Specifically, Bluetooth communications can be encrypted over the air—interface and authentication measures are built in to the communications establishment process. The frequency-hopping nature of Bluetooth spread spectrum communication itself offers a degree of protection against eavesdropping because only receivers that know the frequency-hopping pattern can correctly interpret the packets. Some of the higher layers of the protocol stack also include their own security measures, and application developers are free to incorporate even more robust security at the application layer, if deemed necessary. Security is rightly a concern of many device end users, especially in the wireless realm, and the SIG recognizes this and has developed a specification and a white paper (both available at http://www.bluetooth.com/) that address security at some length.

If these Bluetooth devices can start talking to each other automatically when they're in proximity, won't the spectrum be overloaded in densely packed areas such as airports and conference halls?

Bluetooth communication is based upon proximity networking, and scenarios are possible in which Bluetooth devices could automatically establish communication when they come into proximity of each other. However, such operation needs to be explicitly enabled and is usually an application and often an end-user selection.

As described in the specification, Bluetooth radios can be placed into generally discoverable mode, limited discoverable mode, or nondiscoverable mode. Generally discoverable mode allows a given device to be discovered (and thus, presumably, although not necessarily, to be connected to) by most any other Bluetooth device. Limited discoverable mode limits discovery only to certain other well-defined devices, and nondiscoverable mode makes the given device "invisible" to other devices. With the ability of the user to choose which of these modes is used and to determine which other devices he or she wants to connect to, the problem of all the devices in the vicinity attempting to talk to all the other devices in the vicinity generally can be avoided. Indeed, a fairly high degree of control can be established by applications and, ultimately, by the user.

How does Bluetooth relate to IrDA?

The Infrared Data Association's IrDA is a widely deployed short-range wireless technology. Like Bluetooth technology, it operates over short ranges without wires and is especially useful in mobile devices. But there are differences between Bluetooth and IrDA communication, such as RF's capability to penetrate many obstacles, while infrared light generally requires "line of sight" for connectivity.

There are other differences as well, including cost, range, and data rate (many of these are discussed in our aforementioned book, Bluetooth Revealed; in addition, an excellent paper by David Suvak of Extended Systems compares these two technologies ("IrDA and Bluetooth: A Complementary Comparison," found at http://www.extendedsystems.com/prodinfo/white/bt%5vsFir.html).

One important thing to note about the relationship between Bluetooth and IrDA wireless communication is that the SIG has adopted some middleware layers of the IrDA protocol stack and has incorporated them into the Bluetooth protocol stack. Specifically, the IrOBEX and IrMC protocols developed by the IrDA are used in the Bluetooth protocol stack for object exchange, file transfer, and synchronization. This helps to promote application interoperability, with the intent that applications developed for one of these transports ought to work over the other transport with little or no change.

How does Bluetooth relate to IEEE 802.11?

IEEE 802.11 is a wireless LAN standard that is becoming more common. Like the Bluetooth technology, IEEE 802.11 uses the 2.4GHz spectrum. Unlike the Bluetooth technology, IEEE 802.11 is designed for wireless local area networking. One form of IEEE 802.11 uses direct sequence spread spectrum, a different technique than the frequency-hopping spread spectrum used by Bluetooth communication. IEEE 802.11 offers higher data rates but typically consumes more power than does Bluetooth wireless technology.

Essentially, within the rules and conventions governing operation in the 2.4GHz spectrum, IEEE 802.11 and Bluetooth technology each are optimized for different design points. IEEE 802.11 is primarily for data networking in the same fashion as is done with wired LANs today; Bluetooth wireless communication is optimized for personal area voice and data communications, especially with mobile devices. Although not the same as IEEE 802.11, it is interesting to note that a related emerging standard, IEEE 802.15, is actually considering the adoption of a subset of the Bluetooth protocol stack as the basis for the IEEE 802.15 standard.

With all these technologies operating in the 2.4GHz spectrum, are there concerns that they'll all interfere with each other and that the spectrum will become congested?

Because the 2.4GHz spectrum is unlicensed, it is an attractive spectrum for many technologies. In addition to IEEE 802.11 and Bluetooth wireless communications, already noted as participants in this spectrum, the HomeRFTM technology uses 2.4GHz, some new cordless phones use this spectrum, and microwave ovens emit at this frequency also. With all these different technologies operating in this spectrum, there are some valid concerns about interference among the various technologies. Some even believe that the 2.4GHz spectrum will become so congested that it will not be very useful in the future.

However, it should be noted that one of the rules for operating in this spectrum is that interference must be anticipated and dealt with. RF communication technologies operating at 2.4GHz have taken steps to deal with interference. I believe that more study of large-scale overlapping networks is needed, but there is some good evidence to indicate that these technologies probably can coexist in reasonable situations, with the worst-case effects being degradation in throughput when interference becomes significant.

Will different Bluetooth devices from different manufacturers interoperate with each other?

Much of the effort expended around the Bluetooth technology is intended to promote interoperability. The SIG produced more than 400 pages of profiles (published as Volume 2 of the specification) that are intended to promote interoperability. Cross-platform, cross-vendor interoperability is a fundamental objective of the technology and a goal shared by many implementers. One example of this commitment to interoperability is informal testing events called unplugfests, which allow multiple vendors to come together and test their implementations against those of others in an informal, confidential setting. The SIG has endorsed several unplugfests so far, and in general these have been well-attended and viewed as successful.

Can Bluetooth devices be used on airplanes?

Not today. The United States Federal Aviation Administration (FAA) has looked at the Bluetooth technology and continues to investigate it. A body within the SIG that works with regulatory organizations is trying to ensure the safe in-flight use of the Bluetooth technology (in fact, some airlines and aircraft manufacturers are interested in the use of Bluetooth wireless communication within aircraft cabins as one way to reduce the tremendous amount of cabling in aircraft). For now, as a technology that is not yet approved for in-flight use, Bluetooth devices will be subject to the same rules as cellular phones, meaning that they must be turned off during flight. However, it is within the realm of possibility that Bluetooth devices will be permitted to be used—perhaps even be installed in—aircraft in the future.

I know that the SIG is working on new versions of the specification. What will be included?

The SIG did its best to ensure that the version 1.0 specification was sufficient for initial implementations (the version with errata included is called version 1.0B and was published in December 1999). Products coming to the marketplace from several vendors, along with the many prototype demonstrations made at various developers conferences and similar events, offer evidence that the SIG was largely successful in this endeavor. However, there are more usage models that can be accommodated with Bluetooth wireless communication beyond those in the version 1.0 specification, and the SIG is working diligently on many of these.

What is currently being called the "version 2.0" specification is likely to consist of numerous new profiles that address topics such as printing, local positioning, increased data rates for the radio, extended service discovery, automotive applications, and others. In addition, an interim specification called version 1.1 is scheduled to be published in late 2000 and includes several new errata, along with some straightforward enhancements to the version 1.0 specification.

Will the version 1.0 specification be obsolete when updated versions are published?

An overriding goal of the SIG's post-version 1.0 work is to maintain backward compatibility with the version 1.0 specification. In nearly all cases, the charters of the various working groups include an objective for this backward compatibility. One way that this is achieved is through the use of profiles; new usage scenarios can be formalized in (optional) profiles that are added to the specification without affecting the pre-existing profiles or protocol stack. This seems to provide a nice, functional growth plan for the specification. For areas that might affect the core specification (protocol stack), optional enhancements might be used in some cases to accommodate new functions while maintaining compatibility with existing functions. The SIG members recognize the importance of the success of initial products built against the version 1.0 specification and are making efforts to ensure that the version 1.0 specification remains relevant while it continues to be enhanced.

  • + Share This
  • 🔖 Save To Your Account

Related Resources

There are currently no related titles. Please check back later.