Bluetooth
Bluetooth is perhaps the most hyped of all wireless technologies, and justifiably so. It promises to cram an entire wireless system onto a single chip, cheap enough to be built into all mobile phones, PCs, PDAs, and eventually other devices. Rather than a LAN, Bluetooth's advocates describe it as a PAN (Personal Area Network).
These PANs will surround everyone, Bluetooth promoters hope, embracing every device that people carry. They will automatically interface with the refrigerator at home, the security system in the office, and mobile phones on the move. As people interact, their PANs will connect to beam over contact details, data files, or even digital cash.
Bluetooth dates back to an Ericsson project in 1994, which tried to find a way for mobile phones to communicate wirelessly with accessories such as hands-free kits. In May 1998, it joined with Nokia, Intel, Toshiba, and IBM to form the Bluetooth SIG (Special Interest Group), an alliance aimed at developing an open standard. It was named after Harald Bluetooth, a Viking king who unified Denmark and Norway in the tenth century.
The founding five threw the SIG open to new members, and the results were unprecedented. In less than two years, the founding five were joined by nearly 2,000 others, even winning over initial skeptics such as Microsoft. The main condition of membership is that all members of the SIG must let all others use their Bluetooth patents royalty-free, guaranteeing that the standard remains open.
Technology
Despite such heavyweight backing, Bluetooth has run into some problems. Products were originally supposed to appear by the beginning of 2000, but a year later they were still very scant. It is simply such an ambitious project that it has taken far longer than expected.
Bluetooth's stated aim is to create a single-chip radio with a range of 10 meters, a peak throughput of 720 kbps, and a cost under $5. Up to eight Bluetooth devices can be directly connected to one another in a piconet. Networks with more than eight are possible, but in this case not every device will be able to transmit to every other—each one can see only eight. A network of more than eight is known as a scatternet, and must be subdivided into piconets, as shown in Figure 9.7.
Figure 9.7. Scatternet formed from seven piconets
The $5 price point is important; Bluetooth will have to reach this level, and ultimately cheaper, if it is to be fitted to all electronic devices. The first chips cost substantially more and were put inside relatively high-priced PC or CF+ cards for existing laptops or PDAs. These are relatively pointless without other Bluetooth devices, as a far higher-capacity wireless LAN card can be purchased for around the same cost.
Bluetooth has been criticized for the way it uses the crowded 2.4 GHz ISM band. It is based loosely on the frequency hopping technique of the original 802.11 standard, but cycles through frequencies much faster, hopping up to 3,200 times every second. Some in the wireless LAN industry describe it as a "rude radio," because this rapid cycling is almost guaranteed to interfere with other systems. However, this shouldn't harm Bluetooth itself; 802.11, HomeRF, and Bluetooth are all competing for the same spectrum, and the rapid cycling means that Bluetooth is likely to win a head-to-head battle.
More serious questions hang over interoperability, both at the radio layer and between the applications that will actually be using Bluetooth. In this area, it has learned from some of the mistakes made by IrDA. The Bluetooth SIG will not let any devices use the Bluetooth logo until they have been tested for compatibility with the reference design, and some protocols originally developed for IrDA have actually been licensed for Bluetooth.
Profiles
Bluetooth is intended to be used for many futuristic applications, but the first draft of the specification specifies nine. Each application is described by a separate set of protocols and procedures called a profile. Not every Bluetooth device will support every profile, and some may only support one.
The profile system has attracted some criticism because it means that Bluetooth is effectively nine standards, not one, and the number is likely to grow as more profiles are added. However, the SIG says that it is necessary to ensure interoperability. The profiles share many common protocols, which are illustrated in Figure 9.8. This common ground should make it simple to adapt existing hardware for applications when additional profiles are published.
Figure 9.8. Bluetooth protocol stack
The first draft includes 13 profiles, listed below. In addition to the nine applications, there are four "system" profiles (numbers 1, 2, 5, and 10) which include features common to one or more applications.
Generic Access Profile. This is the core Bluetooth profile, responsible for maintaining links between devices. All Bluetooth devices need to include this profile, but in itself it is not sufficient for any useful applications. It includes functions necessary to use all of the core Bluetooth protocols, shaded light gray in Figure 9.8
Service Discovery Application Profile. This profile enables a user to access the SDP (Service Discovery Protocol) directly, to find out which Bluetooth services are available from a given device. SDP is included as part of the core, but without this extra profile it can only be accessed by applications, not by the user directly.
Cordless Telephony Profile. This is designed for what the Bluetooth SIG calls a "3-in-1-phone," meaning a cellphone with a Bluetooth chip that enables it to be used as a cordless phone. It can also be used for cordless-only phones, or for adding cordless telephony functions to any other Bluetooth equipped device such as a digital watch. It runs over the TCS (Telephony Control Service) protocol.
Headset Profile. This profile specifies how Bluetooth can provide a wireless connection to a headset containing earphones and perhaps a microphone, for use with either a computer or a mobile phone. It uses the serial port profile and the AT (Advanced Technology) commands, which were originally designed to control modems and are so-called because they are taken from an IBM computer of the same name.
Dial-up Networking Profile. This profile is designed for computers connecting to the Internet via a cellphone. At present they have to do this through a special cable or perhaps IrDA, but in future they should be able to use Bluetooth. It includes the serial port profile and PPP (Point-to-Point Protocol), which is the same protocol used by ordinary modems connecting to the Internet.
LAN Access Profile. This is potentially the most useful profile. It is intended for IP data networking, enabling Bluetooth equipped PCs to form a small wireless LAN among themselves or to connect to other LANs via a special access point as in Figure 9.7. The SIG envisages these access points being placed within companies' own private networks and in public places so that people will Bluetooth devices will be able to connect to the Internet.
Object Push Profile. This profile governs the exchange of electronic business cards, short files which contain the same information as a regular business card but can automatically be filed into a device's database. The "push" in the name refers to the fact this information must actively be given out by a user; to protect privacy, electronic business cards are usually not just beamed out to every device in range.
File Transfer Profile. This profile allows a device to access files stored on another. It can be used by any application that needs to transfer files between device, from one device to another, or directly by users. Apart from linking two computers together, devices that might use this profile include mp3 players and digital cameras.
Applications
Some analysts have rightly mocked the more extreme claims made for Bluetooth. It turned the much-maligned "Internet toaster" from a joke to a serious proposition, as companies known only for kitchen appliances joined the SIG. Other favorites include a refrigerator that users can dial up from the supermarket to check what groceries they need, or a trashcan that automatically reorders supplies as empty packaging is discarded.
Though these ideas seem over-the-top, there is definitely a market for some networked appliances. Many people would gladly pay extra for a video recorder that could be programmed remotely over their mobile phone, or the ability to access their music collection wherever they are. It could even save lives—doctors are experimenting with Bluetooth pacemakers so that patients' heartbeats can be monitored and even controlled remotely. If a patient suffers a heart attack or other accident, the Bluetooth device could immediately call an ambulance, transmitting the patient's exact location and diagnosis at the same time.
The sheer number of players in the Bluetooth game points towards success; there are few major computer companies on Earth that haven't bet millions of dollars on the technology. Bluetooth will either bring about a revolution in networking or be an even greater embarrassment to the industry than Iridium.
normal: Web ResourcesThe Broadband Radio IP Network, a project set up by the European Commission's IST (Information Society Technologies) program is trying to integrate wireless LANs with the public cellular network so that people will eventually be able to roam from one to the other while maintaining a connection. The Bluetooth SIG, the cross-industry alliance that drives the Bluetooth standard, includes on its site comprehensive technical information, as well as a database of every Bluetooth product. This is the site of the Wireless Ethernet Compatibility Alliance, a vendor organization that certifies interoperability between IEEE 802.11b devices. The Institute of Electrical and Electronics Engineers oversees all Ethernet standards including the 802.11. The Wireless LAN Association is a nonprofit consortium of wireless LAN vendors established to help educate the marketplace about wireless LANs and their uses. WLANA develops educational materials about wireless LAN users' experiences, applications, and industry trends. http://www.hiperlan.com and http://www.hiperlan2.com The Hiperlan Alliance and the Hiperlan2 Global Forum, promoting the two Hiperlan standards. The HomeRF working group site aims to introduce home users to wireless LANs. |