INTRODUCTION OVERVIEW OF OPERATION FREQUENCY HOPPING NETWORKING CONNECTION POWER CONSIDERATIONS CORE ARCHITECTURE RELIABILITY AND SECURITY ADVANTAGES CONCLUSION

Bluetooth wireless technology is a short-range radio technology and makes it possible to transmit signals over short distance between telephones,computers and other devices and thereby simplify communication and synchronization between devices.It is a global standard that eliminates wires and cables between both stationary and mobile devices,facilitates both data and voice communication. It is intended to replace the cables connecting portable and/or fixed electronic devices. The key features of Bluetooth wireless technology are robustness, low power, and low cost . The Bluetooth core system consists of an RF transceiver, baseband, and protocol stack. The system offers services that enable the connection of devices and the exchange of a variety of data classes between these devices.

Bluetooth operates in the 2.45 GHz wireless spectrum band. This range is called the ISM (Industrial,Scientific and Medical) band.World-wide this spectrum range does not require the consumer to get a license and is shared by many cordless telephones and wireless LAN products.

Bluetooth uses the radio waves located in the frequency band of 2.4 GHz. In this band, Bluetooth transmits voice and data at flows lower than 1mbps.Bluetooth devices can function in following two modes:

Circuit switched : Mode for voice communications on land and wireless digital networks and the connection is asynchronous with flow of 57.6 to 721 kbps.

Packet switched : Mode for internet data ,as well as for higher bandwidth mobile communication systems on the horizon ,like GPRS and the connection is synchronous with flow of 64 kbps.

Frequency hopping is the jumping from frequency to frequency within the ISM band.After a Bluetooth device sends or receives a packet, it communicates with “hop” to another frequency before the next packet is sent. This scheme has the following advantages : It allows Bluetooth devices to use the entirely of the available ISM band. It ensures that any interference will be a short-lived. Any packet that doesn’t arrive safely at the destination can be re-sent at the next frequency.

The Bluetooth technology provides both a point-to-point connection and a point-to-multipoint connections.In point-to multipoint connections,the channel is shared among several Bluetooth units.In point-to-point connection, only two units share the connection. Bluetooth protocols assume that a small number of units will participate in communications at any given time.These small groups are called piconets ,and they consist of one master unit and up to seven active slave units. The master is the unit that initiates transmissions,and the slaves are the responding units.

If several piconets overlap a physical area, and members of the various piconets communicate with each other, this network is known as a scatternet.A device can be present inmore than one piconet but cannot be master in both.A mixtureof high and low power devices at different ranges are allowedto form a piconet.

Bluetooth devices are classified according to three different power classes.

POWER CLASS

MAXIMUM OUTPUT

POWER

1 2 3

100 mW 

2.4 mW 

1 mW

20 dBm 

4 dBm 

0 dBm

Most portable Bluetooth deviceswill probably be in power class 1 or 2 due to cost and battery life issues.A power class 1 device provides up to 100m of range, which is sufficient for home networking and other applicationsthat require a greater range.

The Bluetooth core system covers the four lowest layers and associated protocols defined by the Bluetooth specification as well as one common service layer protocol, the service discovery protocol (SDP) and the overall profile requirements are specified in the generic access profile (GAP). A complete Bluetooth application requires a number of additional services and higher layer protocols that are defined in the Bluetooth specification. The lowest three layers are sometimes grouped into a subsystem known as the Bluetooth controller .

• Channel ManagerThe channel manager is responsible for creating, managing, and destroying L2CAP channels for the transport of service protocols and application data streams. • L2CAP Resource ManagerThe L2CAP resource manager block is responsible for managing the orderingof submission of PDU fragments to the baseband and some relative scheduling between channels to ensure that L2CAP channels with QoS commitments are not denied access to the physical channel due to Bluetooth controller resource exhaustion. • Device ManagerThe device manager is the functional block in the baseband that controls the general behavior of the Bluetooth enabled device.

• Link ManagerThe link manager is responsible for the creation, modification, and release of logical links (and, if required, their associated logical transports), as well as the update of parameters related to physical links between devices .• Baseband Resource ManagerThe baseband resource manager is responsible for all access to the radio medium .• Link ControllerThe link controller is responsible for the encoding and decoding of Bluetooth packets from the data payload and parameters related to the physical channel, logical transport and logical link.• RFThe RF block is responsible for transmitting and receiving packets of information on the physical channel.

MODULATION SCHEME :Bluetooth radio modules use Gaussian Frequency Shift Keying (GFSK) for modulation.A binary system is used where a 1 is signified by a positive frequency deviation and a 0 is signified by a negative frequency deviation.The data is transmitted at a symbol rate of 1 Ms/sec.

BLUETOOTH OPERATIONAL STATES :

Bluetooth has three operational states namely, standby,inquiry and paging.• Standby mode is the default state in which the device idles away with only its native clock running.• In the inquiry mode, the device inquires the identity of other devices .• In the paging mode, the device invites another device to join the protocol.

Bluetooth technology also provides fast, secure voice and datatransmissions.The range for connectivity is up to 10 mts,andline of sight is not required.The Bluetooth radio unit ,

• Functions even in noisy radio environments,ensuring audible voice transmission in severe conditions.• Protects data by using error-correction method.• Provides a high transmission rate.• Encrypts and authenticates for privacy.

• It is geared towards voice and data applications .• It can operate over a distance of 10 meters or 100 meters depending on the Bluetooth device class. The peak data rate with EDR is 3 Mbps. • It is able to penetrate solid objects .• It is omni-directional and does not require line-of-sight positioning of connected devices .• The cost of Bluetooth chips is under $3 .

The comparison of Bluetooth technology with othertechnologies can be done by the following advantages:

Bluetooth wireless technology is the simple choice for convenient, wire-free, short-range communication between devices. It is a globally available standard that wirelessly connects mobile phones, portable computers, cars, stereo headsets, MP3 players, and more. Bluetooth enabled products do not need to install driver software. The technology is now available in its fourth version of the specification and continues to develop, building on its inherent strengths — small-form factor radio, low power, low cost, built-in security, robustness, ease-of-use, and ad hoc networking abilities. Bluetooth wireless technology is the leading and only proven short-range wireless technology on the market today shipping over five million units every week .