Bluetooth and Layer of Bluetooth:

• Bluetooth wireless technology is a short-range radio technology, which is developed for Personal Area Network (PAN).
• Bluetooth wireless technology eliminates wires and cables between both stationary and mobile devices.
• It facilitates both data and voice communication, offers the possibility of adhoc networks and delivers the ultimate synchronicity between all your personal devices.
• It provides agreement at the physical level.

Radio (Layer 1):

• The Radio layer defines the requirements for a Bluetooth transceiver operating in the 2.4 GHz ISM band.
• This is the lowest layer in the Bluetooth protocol stack.
• Bluetooth uses a technique called frequency hopping in establishing radio links with other Bluetooth devices.
• It gives the necessary protection to the transmitted data and avoids tampering.
• The Transmitter characteristics are as follows: Each device is classified into 3 power classes, Power Class1, 2 & 3.
  Power Class 1: It is designed for long range (~100m) devices, with a max output power of 20 dBm.
  Power Class 2: It is designed for ordinary range devices (~10m) devices, with a max output power of 4 dBm.
  Power Class 3: It is designed for short range devices (~10cm) devices, with a max output power of 0 dBm.

Baseband (Layer 2):

• The Baseband layer describes the specification of the Bluetooth Link Controller (LC), which carries out the baseband protocols and other low-level link routines.
• It specifies Piconet/Channel definition, Low-level packet definition and channel sharing.
• The baseband is the digital engine of a Bluetooth system.
• It is responsible for constructing and decoding packets, encoding and managing error correction, encrypting and decrypting for secure communications, calculating radio transmission frequency patterns, maintaining synchronization, controlling the radio, and all of the other low level details necessary to realize Bluetooth communications.
• Bluetooth operates in the 2.4 GHz ISM band.

.

LMP (Layer 3):

• LMP stands for Link Manager Protocol.
• It is responsible for managing the physical details for Bluetooth connections.
• It is responsible for creating the links, monitoring their health, and terminating them gracefully upon command or failure.
• The link manager is implemented in a mix of hardware and software.
• The Link Manager Protocol (LMP) is used by the Link Managers on either side for link set-up and control.

HCI:(Layer 4)

• HCI stands for Host Controller Interface.
• It provides a command interface to the Baseband Link Controller and Link Manager, and access to hardware status and control registers.
• It is the layer of the stack that contains the firmware that is the software that actually controls all the activities happening in the Baseband and Radio layers.
• It provides a common interface between the Bluetooth host and a Bluetooth module.
• It manages the hardware links with the scatternets. It contains the drivers for the hardware devices used in the connection.
• The BIOS is loaded in the HCI Layer.

L2CAP: (Layer 5):

• L2CAP stands for Logical Link Control and Adaptation Protocol.
• It supports higher level protocol multiplexing, packet segmentation, reassembly and conveying of quality of service information.
• L2CAP provides connection oriented and connectionless data services to upper layer protocols with protocol multiplexing capability, segmentation and group abstractions.
• It is layered over the Baseband Protocol and resides in the data link layer.

RFCOMM (Layer 6):

• RFCOMM stands for Radio Frequency Communication(s).
• The protocol provides emulation of serial ports over the L2CAP protocol. The protocol is based on the ETSI standard TS 07.10.
• It takes care of the communication channel between two devices or between a master and a slave.
• RFCOMM basically has to accommodate two kinds of devices: Communication end-points such as computers or printer and devices that are a part of communication channel such as Modems.

SDP (Layer 7):

• SDP stands for Service Discovery Protocol (SDP).
• It provides a means for applications to discover, which services are provided by or available through a Bluetooth device.
• It also allows applications to determine the characteristics of those available services.
• A specific Service Discovery protocol is needed in the Bluetooth environment.