Introduction to Bluetooth technology
It is a short-range wireless communication technology developed by leading computer and communication companies in the world. IBM is one of the five founding companies.
The name Bluetooth comes from the king of Denmark, who controlled Denmark and Norway in the 10th century. We expect that the Bluetooth technology will unite the worlds of cellular phones and data communications as the king did in Scandinavia.

The Bluetooth technology connects nearby devices at a data rate of 1 Mbps. It automatically searches for devices within its radio range (10 m) and connects them. We can get rid of the troublesome operations to find a connector at the back of the PC to plug a cable in it.

Over two thousand companies have adopted the Bluetooth technology for such ease of use.
Some time ago, each of peripheral devices, such as mice, keyboards, and printers, used to require a dedicated cable to be connected to a PC. Now, thanks to the Universal Serial Bus (USB), they only need a standard cable. In near future, the Bluetooth technology will throw all the cables out of our computing environments.

Here are few members of Bluetooth Special Interest Group (SIG).
Founding Members: Ericsson, Nokia, IBM, Intel
Additional Members: 3Com, Lucent, Microsoft, Motorola

The Aim of Bluetooth
The aim has been set quite high. It is to arrive at a specification for a technology that optimizes the usage model of all mobile computing and communications devices, and providing:
  • Global usage
  • Voice and data handling
  • The ability to establish ad-hoc connections
  • The ability to withstand interference from other sources in open band
  • Very small size, in order to accommodate integration into variety of devices
  • Negligible power consumption in comparison to other devices for similar use
  • An open interface standard
  • Low cost of all units, as compared to their non-Bluetooth correspondents.
Here are few key features of bluetooth technological architecture.

Service Discovery Protocol: Service discovery protocol (SDP) features allow for automatic recognition and configuration between two devices of different types and from different manufacturers.
There are two types of discovery within the Bluetooth specification. Device discovery allows one device to query devices within range and acquire, in turn, key information about their general capabilities. This key information includes full address, human-readable name, and general device type (cell phone, laptop personal computer, headset).
Service discovery enables a device to learn the details of supported profiles and to actually browse those profiles to find out how to access certain features. The service discovery concept allows for even more information and access methods to be exchanged.

Ad-Hoc Network: Ad hoc networking is the capability to quickly establish and dissolve small groups of devices with very little user involvement and no permanent address assignment. Several devices establish one network and retain the relationship only for the desired time of interaction. If security is desired, users can type in passwords or personal identification numbers (PINs) for bonding and encryption.
An Ad-hoc network is a simple network where communications are established between multiple stations in a given coverage area without the use of an access point or server.
An ad-hoc network is a network having a dynamic topology where nodes are free to move arbitrarily. Such networks are typically based on wireless communication technologies.
Ad-Hoc networks are not dependent on a single access point, they have extraordinary versatility. Ad-Hoc networking protocols seamlessly create instant networks, reconfiguring on the fly as the user or device moves, or as other devices exit or enter the network. They use smart routing, adapting to changing signal conditions by dynamically switching connection paths among devices to maintain communication.
Bluetooth is a Radio Frequency (RF) specification for short-range, point-to-multipoint voice and data transfer. Bluetooth can transmit through solid, non-metal objects. Its nominal link range is from 10 cm to 10 meters, but can be extended to 100 meters by increasing the transmit power. It is based on short-range radio links, and facilitates ad hoc connections for stationary and mobile communication environments.

Piconet: a collection of devices connected via Bluetooth technology in an ad-hoc fashion. 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 for synchonization purposes, and the other(s) as slave(s) for the duration of the piconet connection.
Scatternet: Two or more independent and non-synchronized piconets that communicate with each other. As shown in figure, a slave as well as a master unit in one piconet can establish this connection by becoming a slave in the other piconet.
Master unit: the device in a piconet whose clock and hopping sequence are used to synchronize all other devices in the piconet.
Slave units: all devices in a piconet that are not the master (up to 7 active units for each master).
Mac address: a 3-bit Media Access Control address used to distinguish between units participating in the piconet.
Parked units: devices in a piconet which are synchronized but do not have MAC addresses.
Sniff and hold mode: devices that are synchronized to a piconet, and which have temporarily entered power-saving modes in which device activity is lowered.
Security Modes: Bluetooth has three security modes. Security mode 1 is an insecure mode. The security functions of encryption and authentication are completely bypassed. Security mode 2 is a service level security. This allows security just after the data link layer provides connectivity to the upper layers of the OSI model. Security mode 3 is a link-level security. This is a device initiating security before the connection is established and is based upon a shared key that is generated when the two devices talk for the first time.

Security in Bluetooth
Bluetooth supports several security features, depending on the application and user requirements. These features range from the protection against eavesdropping inherent to the frequency-hopping spread-spectrum technology, to the use of keys or PIN and password combinations. With the use of PINs (alphanumeric strings of up to 16 characters), the 128-bit SAFER+ encryption algorithm is used to create very strong security and encryption between devices. More security can be added at the application level if desired. This implementation should meet the requirements of systems that must comply with the Health Insurance Portability and Accountability Act of 1996 privacy standards.
Bluetooth security seemed to be adequate only for small ad hoc networks, such as a network of the participants in a meeting. Connecting a PDA to a mobile phone using Bluetooth may also be secure enough. But at the moment Bluetooth may not be secure enough for larger ad hoc networks, money transfers and transferring other sensitive information.

QoS in Bluetooth
Service (QoS) requirements can be judged in terms of bandwidth delay and Security. The Bluetooth technology has originally been developed as a wireless replacement for cables between electronic devices e.g. between a mobile phone and a Laptop computer. However the Bluetooth interface is gradually developing into a full wireless networking solution.
The Bluetooth interface has a gross bitrate of 1 Mbps to support simultaneous voice and data communications. Bluetooth provides both authentication and encryption.
Authentication provides the ability to verify the identity of the claimant through a challenge response algorithm. The Encryption procedure enables encryption of the data sent over the air-interface to prevent unintended eavesdropping.
The Bluetooth interface supports both Point-to-Point and Point-to-Multipoint communications. The Bluetooth architecture supports ad-hoc networking. Bluetooth does not rely on an existing infrastructure to allow wireless communications between devices. Bluetooth devices can discover each other and establish a link, optionally without user interaction. The Bluetooth architecture differs from a cellular network architecture in the sense that there are no specialized nodes, but in principle each Bluetooth device provides the same functionality. In a cellular network different nodes can be identified, where each node has different functions and capabilities (e.g. mobile phone and base station). The ad-hoc networking architecture has obvious advantages, but it is also the main reason that setup times in Bluetooth are long (order of seconds) and handovers are poorly supported. The Bluetooth technology is specifically targeted for devices, which require a low power consumption, such as mobile phones, PDAs, Laptops, computer mouse, keyboards, etc.

The Bluetooth features can be summarized in a few words as a Low-cost, Low-power, Small-sized, Short-range, Robust wireless technology. The low cost makes Bluetooth suitable even to be integrated into low cost devices such as a wireless computer mouse. However the cost price will very much depend on the success of Bluetooth and the subsequent volumes in which the Bluetooth chip will be produced.
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