Table of Contents:
Cable replacement protocol
The RFCOMM protocol is used for the cable replacement option in Bluetooth. It is a simple transport protocol with additional provisions for emulating the nine circuits of RS232 serial ports over L2CAP part of the Bluetooth protocol stack. It supports large base for applications that uses serial communication. It provides a reliable data stream, multiple connections, flow control and serial cable line settings.
Telephony Control Protocol
Specification (TCS Binary)
The TCS binary protocol defines the call control signaling for establishment of speech and data calls between two Bluetooth devices. It is bit oriented protocol.
The Host Controller Interface (HCI)
The HCI provides a command interface to the base band controller, link manager and access to the hardware status and control registers. The interface provides a uniform method of accessing the Bluetooth baseband capabilities. The Host control transport layer removes transport dependencies and provides a common driver interface. Three interfaces are defined in the core specification: USB, RS-232, and UART.
PPP, TCP, UDP and IP are standard Internet protocols defined by IETF. These are used as the lower layer protocols for transporting packets or data-grams on their specified IP addresses. OBEX
OBEX is a session protocol defined by IrDA. This protocol is also utilized by Bluetooth thus enabling the possibility for application to use either the Bluetooth radio or IrDA technologies.
Bluetooth may be used as a bearer technology for transporting between a WAP client and a nearby WAP server. WAP operates on top of the Bluetooth stack using PPP and the TCP/IP protocol suite.
Each of these protocols is arranged neatly as layers one above the other forming a stack of protocols. A stack is a pile of objects or things arranged neatly.
Hence, Bluetooth is defined as layered protocol architecture because each layer supports the layer above and below it. The complete protocol stack consists of both Bluetooth specific protocols which are clearly defined or developed for Bluetooth like LMP and non-Bluetooth specific that were designed to enable the re-use of existing protocols for various functions. Non-specific protocols can be used with many other platforms like WAP, UDP AND OBEX. These were used to speed up the development of Bluetooth protocol at higher layers at the same time adaptation to work with Bluetooth devices and ensure interoperability. The outline of Bluetooth layers and protocols associated with it are shown below.
Each of the layers specified above is important in Bluetooth communication and has an internal circuitry to perform the desired task. In this section we will deal with internal details of all the layers.