WPANs: A Capsule View of Bluetooth

This section provides an overview of Bluetooth and is based on openly available information from the Bluetooth Special Interest Group (SIG). The Bluetooth SIG (www.bluetooth.com) is an industry group consisting of leaders in the telecommunications, computing, and networking industries that are driving the development of the technology and bringing it to market.^[9]

Overview

Bluetooth wireless technology is a low-cost, low-power, short-range radio link for mobile devices and WAN/LAN APs. It offers fast and reliable digital transmissions of both voice and data over the globally available 2.4 GHz ISM band. The Bluetooth wireless technology is set to advance the personal connectivity market by providing freedom from wired connections (see Table 3-4 for a comparison). It is a specification for a small-form-factor, low-cost radio solution providing links between mobile computers, mobile phones, and other handheld devices, and connectivity to the Internet. The Bluetooth Specification defines a short (around 10 meters) or optionally a medium-range (around 100 meters) radio link that is capable of voice or data transmission up to a maximum capacity of 720 Kbps per channel.

Table 3-4. Comparison of Bluetooth and cabled connections

	Bluetooth	Regular Cable
Topology	Supports up to seven simultaneous links	Each link requires another cable.
Flexibility	Goes through walls, bodies, cloths, and so on	LOS or modified environment.
Data rate	1 megasamples per second (MSPS), 720 Kbps	Varies with use and cost.
Power	0.1 watts active power	0.05 watts active power or higher.
Size and weight	25 mm + 13 mm + 2 mm, several grams	Size is equal to range. Typically 1—2 meters. Weight varies with length (ounces to pounds).
Cost	Long-term $5 per endpoint	~$3—100 per meter (end-user cost).
Range	10 meters or less Up to 100 meters with PA	Range is equal to size. Typically 1—2 meters.
Universal	Intended to work anywhere in the world	Cables vary with local customs.
Security	Link layer security, SS radio	Secure (a cable).

Products are now beginning to be delivered and Ericsson anticipated that by the 2002, tens of millions of Bluetooth wireless technology devices will be around. Cahners-Instat projects that close to 700 million Bluetooth devices will ship annually in 2005.

The raw throughput of Bluetooth wireless technology is 1 Mbps with an actual data rate of 728 Kbps. One of the key requirements in the design of the air interface for Bluetooth wireless technology is that it must be able to operate worldwide. The only frequency band that satisfies these requirements is at 2.4 GHz at the ISM band. The ISM band is also license free and open to any radio system. To avoid interference from other devices operating in the ISM band, Bluetooth wireless technology uses FHSS to make the link robust. The radio transceiver hops to a different frequency after each transmission and reception (1,600 hops per second). The system hops among 79 frequencies at 1 MHz intervals. Up to seven simultaneous connections can be established and maintained. Devices can form piconets with up to 256 units (one master and seven slaves with the balance in standby modes). Devices automatically modify transmitting power in relation to distance and activity.

Bluetooth wireless technology is used to connect computing and telecommunication devices without the need of cables. It delivers opportunities for rapid ad hoc connections and the possibility of automatic connections between devices for synchronizing calendars and so on. It creates the possibility of using mobile data in a different way for different applications such as a cordless connection between a headset and the mobile phone, and the cordless transfer of files between two laptops. It also enables you to use the mobile phone for three functions: intercom, portable, and cellular. See Figure 3-10 for an example.

Figure 3-10: Bluetooth applications Source: Tom Siep, TI, and Chatschik Bisdikian, IBM

An important aspect is that Bluetooth products do not have to incorporate the entire Bluetooth specification. To get compatible products out more rapidly, the Bluetooth SIG has developed the concept of profiles. Profiles describe how the implementation of user models can be supported. As long as they share the same Bluetooth profiles, devices from different manufacturers can communicate anywhere in the world. A profile is defined as a combination of protocols and procedures that are used by devices to implement specific services. The profiles are described in the Bluetooth Specification. A vendor that wants its chip to interact with headsets can just support the Headset Profile; it will not need to look into compatibility tests for other profiles.^[8] There are four fundamental profiles:

• Generic Access Profile (GAP Profile) for discovery and link management

• Service Discovery Application Profile (SDAP Profile) for discovering services and retrieving information

• Serial Port Profile (SPP Profile) for emulating serial cable connections

• Generic Object Exchange Profile (GOEP Profile) for synchronization, file transfer, or object push

There are nine usage profiles:

• Cordless Telephone Profile (CTP Profile) for telephony features

• Intercom Profile (IP Profile) for intercom functionality (also referred to as the walkie-talkie usage)

• Headset Profile (HS Profile)

• Dial-up Networking Profile (DNP Profile) for modems, mobile phones, and so on

• Fax Profile (FP Profile)

• LAN Access Profile (LAP Profile) for LAN access using the Point-to-Point Protocol (PPP)

• Object Push Profile (OPP Profile) for the push/pull of data objects between devices

• File Transfer Profile (FTP Profile)

• Synchronization Profile (SP Profile)

Bluetooth wireless technology has built-in encryption and authentication and thus is seen as being secure in any environment. In addition, as noted, a frequency-hopping scheme with 1,600 hops per second is employed. All of this, together with an automatic output power adaptation to reduce the range exactly to the requirement, makes the system difficult to eavesdrop, according to proponents.

Bluetooth wireless technology is a layer 1 and 2 standard for wireless communication between devices. However, this should not be confused with Wireless Application Protocol (WAP). WAP is an application-oriented standard for communication. WAP does not deal with the lower layers of the Open Systems Interconnection (OSI) model like Bluetooth wireless technology does. WAP can be successfully used in combination with Bluetooth wireless technology in e-commerce applications, for example. WAP is discussed in detail in Chapter 7, “Wireless Application Protocol (WAP).”

The following sections from “Bluetooth Technical Summary” through “Licensing Technologies” (except for “Constituent Products”) have been reprinted from the “Beginner’s Guide” from Ericsson’s web site at www. ericsson.com/bluetooth/training.^[9]

^[9]Information in this section is taken from promotional materials promulgated by the Bluetooth SIG (www.bluetooth.com) and Ericsson (www.ericsson.com).

^[8]A list of qualified products can be found at http://qualweb.opengroup.org/Template.cfm?LinkQualified=QualifiedProducts .

^[9]Information in this section is taken from promotional materials promulgated by the Bluetooth SIG (www.bluetooth.com) and Ericsson (www.ericsson.com).