Bluetooth is the name for an emerging technology that uses short-range radio links instead of cables to connect portable electronic devices. This allows a wide range of devices to communicate with one another without actually being physically connected to one another.
Some of the most notable features of Bluetooth technology are the facts that it is relatively inexpensive (this is first and foremost for many potential consumers); it is not extremely fragile, it is very user friendly, and has low power consumption. Bluetooth can be used to create wireless Personal Access Networks (PANs) while offering fast and reliable transmission of both voice and data. Bluetooth offers wireless access to the Internet (for home access as well as laptops, PDAs, and other hand held devices), cell phone services, and local access networks.
A complete Bluetooth system requires an RF portion in order to send or receive data; a module for processing, a memory module, and an interface to the electronic device it is to communicate with (such as a phone, Palm, or camera).
The lower-layer protocols can typically be found within the baseband module and the host processor must support the protocols of the upper-layer. Simply put, the RF-baseband solution supplies the means necessary in order to communicate with the host. This additionally requires an interface by which they can connect as well as the 'upper-layer' protocols in order to actually apply the applications the product is designed to support.
The higher upper layers of Bluetooth technology are referred to as Bluetooth Profiles. These profiles are literally a set of protocols that are optimized in order to complete specific tasks or applications. If you wish to share files between two linked devices they must be compatible devices that have similar applications across the spectrum of devices.
The Bluetooth stack has the following components:
1) RF portion. This is necessary for reception and transmission.
2) Baseband portion.
3) Link Control Unit4) Link Manager. This supports lower layer protocols.
5) Interface. This allows a connection to the host device.
6) Host processor. This will support upper layer protocols.
7) L2Cap. This also supports upper layer protocols.
The Radio Frequency (RF) supplies the Digital Signal Processing (DSP) element to the system while the baseband microcontroller processes the signals. The link controller supports the link manager and controls the baseboard functions by sending and receiving data, identifying the device sending data, performing authentication, and determining the frame to which the transmission should be sent. The link controller also directs the way devices communicate with each other as well as enabling the power saving sleep mode when not being directly used.
The link manager is responsible for setup, authentication, the configuration of links, and other lower layer protocols. The baseband and link manager work together in order to establish connections for the network.
The Host Controller Interface (HCI) allows the communication of lower layer protocols to the host (which contains a processor) device. The L2Cap supports upper layer protocols and enables communication with the lower layers. The higher-upper layer protocols are often very specific tasks and applications that require integration with the lower layer applications. The ability of all these components to work together and communicate adequately is very important to Bluetooth technology.
Core Protocols in Bluetooth technology:
1) Baseband. This layer combined with the link control layer enables an RF link to form while offering two distinct physical links with corresponding baseband packets. These links are Synchronous Connection-Oriented and Asynchronous Connectionless. Synchronous Connection-Oriented connections can contain either audio or a combination of data and audio while Asynchronous Connectionless packets can only be used for the purpose of transmitting data.
2) Link Manager Protocol. This is responsible for establishing links between Bluetooth devices including but not limited to security functions such as authentication and encryption keys as well as the negotiation duty cycles for the Bluetooth device and the device on the receiving end.
3) Logical Link Control and Adaptation Protocol. This adapts the upper layer protocols over the baseband.
4) Service Discovery Protocol. This allows device information, services and characteristics of services to be queried. Once queried, a connection can be made between two or more Bluetooth devices.
Telephony and Cable Replacement Protocols:
1) Telephony Control Protocol. This is a bit oriented protocol that defines the control signal for the call and establishes speech and data cells between the devices.
2) RFCOMM. This is a serial line emulation protocol. It is based on European Telecommunications Standardization Institute's specifications and emulates control over Bluetooth baseband. This provides not only transport capabilities but also allows for upper level services that use serial lines as transport mechanisms.
Adopted Protocols:
1) PPP: PPP is the point-to-point protocol. PPP Networking is the act of taking IP packets from the PPP layer and putting them on the Local Access Network.
2) TCP/UDP/IP: TCP/IP/PPP this is used for all Internet bridge purposes. It is also available as transport for the WAP.
3) OBEX Protocol. This is a session protocol that is designed to exchange data simply and automatically.
Advantages:Bluetooth technology makes the use of peer-to-peer connectivity simpler by enabling all manner of devices to communicate freely and automatically. Bluetooth also allows for fast, secure voice and data transmissions. While the range for connectivity is only about 30 feet, line of sight is not necessary for the signals to be received and transmitted.
Bluetooth is also capable of functioning in noisy radio environments while ensuring audible voice transmissions even in less than ideal situations. It can correct data through use of error correction methods while providing a high transmission rate. You also have the ability to use encryption in order to provide added layers of security.
Bluetooth may also be used to create ad hoc networking among personal devices in order to quickly exchange information.
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