| || |
Bluetooth Basic Concepts -
December 10th, 2006
Bluetooth: How we are connected
Bluetooth technology is a global standard that eliminates wires and cables between both stationary and mobile devices. It also facilitates both data and voice communication and offers the possibility of ad hoc networks and delivers the ultimate synchronicity between all personal devices.
The idea that resulted in the Bluetooth wireless technology was born in 1994 when Ericsson Mobile Communications decided to investigate the feasibility of a low-power, low-cost radio interface between mobile phones and their accessories. The Bluetooth wireless technology comprises hardware, software and interoperability requirements. It has been adopted not only by all major players in the telecom, computer and home entertainment industry, but also in such diverse areas as the automotive industry and healthcare, automation and toys, etc. – almost all sectors of the economy.
The Bluetooth Specification defines a short (around 10 m) or optionally a medium range (around 100 m) radio link capable of voice or data transmission to a maximum capacity of 720 kbps per channel. The Bluetooth technology supports both point-to-point and point-to-multipoint connections.
Radio frequency operation is in the unlicensed industrial, scientific and medical (ISM) band at 2.4 to 2.48 GHz, using a spread spectrum, frequency hoping, full-duplex signal at up to 1600 hops/sec. The signal hops among 79 frequencies at 1 MHz intervals to give a high degree of interference immunity. RF output is specified as 0 dBm (1 mW) in the 10m-range version and -30 to +20 dBm (100 mW) in the longer-range version.
When producing the radio specification, high emphasis was put on making a design enabling single-chip implementation in CMOS circuits, thereby reducing cost, power consumption and the chipsize required for implementation in mobile devices.
Voice: Up to three simultaneous synchronous voice channels are used, or a channel which simultaneously supports asynchronous data and synchronous voice. Each voice channel supports a 64 kbps synchronous (voice) channel in each direction.
Data: The asynchronous data channel can support maximal 723.2 kbps asymmetric (and still up to 57.6 kbps in the return direction), or 433.9 kbps symmetric.
* a Master can share an asynchronous channel with up to 7 simultaneously active Slaves in a Piconet.
* by swapping active and parked slaves out respectively in the piconet, 255 slaves can be virtually connected using the PM_ADDR and to park even more slaves the BD_ADDR can be used.
Slaves can participate in different piconets and a master of one piconet can be the slave in another, this is known as a Scatternet. Up to 10 piconets within range can form a Scatternet, with a minimum of collisions.
Bluetooth architecture overview
This section describes the Bluetooth architecture. The complete protocol stack comprises, as seen in Figure 1, of both Bluetooth specific (non-shaded) protocols and non-Bluetooth specific (shaded) protocols.
Different applications may run over different protocol stacks. Nevertheless, each one of these different protocol stacks uses a common Bluetooth data link and physical layer. The main principle in designing the protocols and the whole protocol stack has been to maximize the re-use of existing protocols for different purposes.
Bluetooth core protocols
The Baseband and Link Control layer enable the physical RF link between Bluetooth units forming a piconet. This layer controls the Bluetooth unit’s synchronization and transmission frequency hopping sequence. The two different link types defined in Bluetooth, Synchronous Connection Oriented, SCO, and Asynchronous Connectionless, ACL, are also managed by this layer.
Audio transmissions can be performed between one or more Bluetooth units, using different usage models. Audio data do not go through the L2CAP layer but go directly between two Bluetooth units.
The Host Controller Interface (HCI) provides a uniform interface method for accessing the Bluetooth hardware capabilities. It contains a command interface to the Baseband controller and link manager and access to hardware status. Finally, it contains control and event registers.
The Link Manager Protocol (LMP) is responsible for link set-up between Bluetooth units. It handles the control and negotiation of packet sizes. The LMP also handles management of power modes, state of a Bluetooth unit in a piconet and control of link and encryption keys for authentication and encryption.
The Bluetooth Logical Link Control and Adaptation Protocol (L2CAP) provides connection-oriented and connectionless data services to upper layers with protocol multiplexing capability, segmentation and reassembly operation, and group abstractions.
The Service Discovery Protocol (SDP) defines how a Bluetooth client’s application shall act to discover available Bluetooth servers’ services and their characteristics such as searching for a service, discovery of new services and detection of a no longer available service.
Cable replacement protocol
The RFCOMM protocol is a serial port emulation protocol. The protocol covers applications that make use of the serial ports of the unit. RFCOMM emulates RS-232 control and data signals over the Bluetooth baseband and provides transport capabilities for upper services (e.g. OBEX).
Telephony control protocol
The Telephony Control protocol – Binary (TCS Binary or TCS BIN) is a bit-oriented protocol, which defines the call control signaling for the establishment of speech and data calls between Bluetooth devices. In addition, it defines mobility management procedures for handling groups of Bluetooth TCS devices.
Besides TCS, a number of Telephony Control AT-commands are supported for transmitting control signals for telephony control. These use the serial port emulation, RFCOMM, for transmission.
The IETF Point-to-Point protocol (PPP) in the Bluetooth technology is designed to run over RFCOMM to accomplish point-to-point connections.
The TCP/UDP/IP standards are defined to operate in Bluetooth units allowing them to communicate with other units connected, for instance, to the Internet. Hence, the Bluetooth unit can act as a bridge to the Internet. The TCP/IP/PPP protocol configuration is used for all Internet Bridge usage scenarios in Bluetooth 1.0 and for OBEX (Object Exchange Protocol) in future versions. The UDP/IP/PPP configuration is available as transport for WAP (Wireless Application Protocol).
IrOBEX, shortly OBEX, is an optional application layer protocol designed to enable units supporting infrared communication to exchange a wide variety of data and commands in a resource-sensitive standardized fashion. OBEX uses a client-server model and is independent of the transport mechanism and transport API.
The Wireless Application Protocol (WAP) is a wireless protocol specification that works across a variety of wide-area wireless network technologies bringing the Internet to mobile devices. Bluetooth can be used like other wireless networks with regard to WAP; it can be used to provide a bearer for transporting data between the WAP Client and its adjacent WAP Server.
Bluetooth Usage Models and Profiles
In this section, a number of usage models identified by the Bluetooth SIG as fundamental are described. Each usage model is accompanied by a Profile. Profiles define the protocols and protocol features supporting a particular usage model. There are four general profiles that are widely utilized by these usage model oriented profiles. These are the generic access profile (GAP), the serial port profile, the service discovery application profile (SDAP), and the generic object exchange profile (GOEP).
The File Transfer usage model offers the capability to transfer data objects from one Bluetooth device to another. The model also offers the possibility of browsing the contents of the folders on a remote device.
The Internet Bridge usage model describes how a mobile phone or cordless modem provides a PC with dial-up networking capabilities without the need for physical connection to the PC. This scenario requires a two-piece protocol stack, one for AT-commands to control the mobile phone and another stack to transfer payload data.
The LAN Access usage model is similar to the Internet Bridge usage model except that the LAN Access model does not use the protocols for AT-commands. The usage model describes how data terminals use a LAN access point as a wireless connection to a Local Area Network.
The synchronization usage model provides the means for automatic synchronization between, for instance, a desktop PC, a mobile phone and a notebook. It requires business card, calendar and task information to be transferred and processed by computers, cellular phones and PDAs utilizing a common protocol and format.
The Three-in-One Phone usage model describes how a telephone may act as a cordless telephone connecting to the public switched telephone network, as a “walkie-talkie” or handset extension connecting directly to other telephones, or as a cellular telephone connecting to the cellular infrastructure.
The Ultimate Headset usage model defines how a Bluetooth equipped wireless headset can be connected, to act as a remote unit’s audio input and output interface. As for the Internet Bridge usage model, this model requires a two-piece protocol stack.
There are a number of competitors to the Bluetooth technology such as IrDA, implementations based on IEEE 802.1, Ultra-Wideband Radio (UWB) and Home RF. However, the Bluetooth concept offers several benefits compared with those techniques . The main advantages of Bluetooth are the minimal hardware dimensions, the low price on Bluetooth components and the low power consumption for Bluetooth connections. The diversity in product offerings from companies in the Bluetooth SIG and their broad support for the technique creates a unique market position. It is estimated that before year 2002, Bluetooth will be a built-in feature in more than 100 million mobile phones and in several million other communication devices, ranging from headsets and portable PC’s to desktop computers and notebooks.
1.READ RULES CAREFULLY BEFORE POSTING.REFER FAQS.
2.USE SEARCH OPTIONS.DO NOT ASK TO MAIL PROJECTS.
3.DO NOT POST YOU MAIL IDS.
4.CLICK ON THANKS BUTTON TO THANK A PERSON.
5.DO NOT POST REGARDING HOW INFORMATIVE/HELPFUL A THREAD WAS, RATE IT.
6.POST IN CORRECT SECTIONS.DO NOT SPAM.