Bluetooth Protocol Stack
- Bluetooth uses spread spectrum technologies at the Physical Layer while using both direct sequence and frequency hopping spread spectrum technologies.
- It uses connectionless (ACL–Asynchronous Connectionless Link) and connection-oriented (SCO– Synchronous Connection-oriented Link) links.
- Bluetooth protocol stack can be divided into four basic layers according to their functions.
Bluetooth Core Protocols
- This comprises of baseband, Link Manager Protocol (LMP), Logical Link Control and Adaption Protocol (L2CAP), and Service Discovery Protocol (SDP).
- Baseband: It enables the physical RF link between Bluetooth units forming a piconet.
- This layer uses inquiry and paging procedures to synchronize the transmission with different Bluetooth devices. Using SCO and ACL link different packets can be multiplexed over the same.
- Link Manager Protocol: When two Bluetooth devices come within each other’s range, link managers of either device discover each other.
- LMP then engages itself in the peer-to-peer message exchange. These messages perform various security functions starting from authentication to encryption.
- It also controls the power modes, connection state, and duty cycles of Bluetooth devices in a piconet.
- Logical Link Control and Adaption Protocol (L2CAP): This layer is responsible for segmentation of large packets and the reassembly of fragmented packets.
- L2CAP is also responsible for multiplexing of Bluetooth packets from different applications.
- Service Discovery Protocol (SDP): It enables a Bluetooth device to join a piconet. Using SDP a device inquires what services are available in a piconet and how to access them.
- SDP uses a client-server model where the server has a list of services defined through service records.
- In Bluetooth device there is only one SDP server. If a device provides multiple services, one SDP server acts on behalf of all of them.
Cable Replacement Protocol: ( Bluetooth Protocol Stack )
- This protocol has only one member which is Radio Frequency Communication (RFCOMM).
- Also, RFCOMM: It is a serial line communication protocol and based on ETSI 07.10 specification.
- The “cable replacement” protocol emulates RS-232 control and data signals over Bluetooth Baseband Protocol.
Telephony Control Protocol: ( Bluetooth Protocol Stack )
- It comprises of two protocol stacks, viz., Telephony Control Specification Binary (TCS BIN), and the AT-commands.
- Telephony Control Specification Binary (TCS BIN): It a bit-oriented protocol. It defines all the call control signaling protocol for set up of speech and data calls between Bluetooth devices.
- It also defines mobility management procedures for handling groups of Bluetooth TCS devices. Moreover, It based on the ITU-T Recommendation Q.931.
- AT-Commands: It defines a set of AT-commands by which a mobile phone can use and controlled as a modem for fax and data transfers.
- Moreover, AT commands used from a computer or DTE to control a modem or DC. They based on ITU-T Recommendation V.250 and GSM 07.07.
Adopted Protocols: ( Bluetooth Protocol Stack )
- Also, This has many protocols stacks like Point-to-Point Protocol (PPP), TCP/IP Protocol, OBEX (Object Exchange Protocol), Wireless Application Protocol (WAP), vCard, vCalender, Infrared Mobile Communication (IrMC), etc.
- PPP Bluetooth: This offers PPP over RFCOMM to accomplish point-to-point connections. Point-to-Point Protocol is the means of taking IP packets to/from the PPP layer and placing them onto the LAN.
- TCP/IP: Moreover, This protocol used for communication across the Internet. TCP/IP stacks used in numerous devices including printers, handheld computers, and mobile handsets.
- Also, TCP/IP/PPP used for the all Internet bridge usage scenarios.
- OBEX Protocol: OBEX a session protocol developed by the Infrared Data Association (IrDA) to exchange objects.
- Moreover, OBEX provides the functionality of HTTP in a much lighter fashion. It defines a folder listing object, which can used to browse the contents of folders on remote devices.
- Content Formats: vCard and vCalender specifications define the format of an electronic business card and personal calendar entries developed by the Versit consortium.
- These content formats used to exchange messages and notes. They defined in the IrMC specification.