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Explain with neat fig the bluetooth protocol stack from wireless communication |
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Answer» • OBEX: Object Exchange • TCS BIN: Telephony control protocol specification – binary • BNEP: Bluetooth network encapsulation protocol • SDP: Service discovery protocol • RFCOMM: Radio frequency comm. Radio Layer • Radio layer defined the carrier frequencies and output power • Bluetooth uses 2.4 GHZ license free band. • Frequency hopping and TDD (time division duplex) is used for transmission with fast hopping rate of 1600 hops/s. • It uses 79 hop carriers equally spaced with 1 MHz. • Gaussian FSK used for modulation. BASEBAND Layer • Baseband layer performs frequency hopping to avoid interference and to access the medium. • Defines physical links and many packet formats. • It CONTROLS: o Device Addressing o Channel control through paging and inquiry methods o Power saving operations o Flow control and synchronization among Bluetooth devices. Link Manager Protocol (LMP) • The Link Manager protocol manages various aspects of the radio link between master and slave. • The following functions are covered by LMP: o Authentication, pairing and encryption o Synchronization o Capability negotiation o QoS negotiation o Power control o Link Supervision o State and transmission mode change Logical Link Control and Adaptation Layer Protocol (L2CAP) • L2CAP is layered over the Baseband Protocol and resides in the data link layer. • L2CAP provides: o Connection-oriented and connectionless data services to upper layer protocols with protocol multiplexing capability. o Segmentation and reassembly operation. o Group abstractions. • L2CAP provides three different types of logical channels that are transported via ACL link between master and slave, these are: o Connectionless used for broadcast o Connection-oriented for data transfer with QoS flow specification. o Signaling used to exchange signaling MESSAGES between L2CAP entities. Host Controller Interface (HCI) • The HCI provides a command interface to the baseband controller and link manager. • It provides access to hardware status and control registers. • Essentially this interface provides a uniform method of accessing the Bluetooth baseband capabilities. • The HCI exists across 3 sections, The Host, Transport Layer, and Host Controller. Each of the sections has a different role to play in HCI system. • HCI defines the set of functions of a Bluetooth module that are accessible to the host and its application. • HCI can be seen as a software/hardware boundary. RFCOMM • The RFCOMM protocol provides emulation of serial ports over the L2CAP protocol. • It is a cable replacement protocol that provides a serial line interface to all the applications. • The protocol is based on the ETSI standard TS 07.10. • It supports multiple serial ports over a single physical channel. Service Discovery Protocol (SDP) • The service discovery protocol helps the applications to discover which services are available and to determine the characteristics of those available services. • SDP defines only the discovery of services, not about their usage. • New service is discovered as follows: o Client SENDS a request to search for an interested service. o Then the server responds to the client with the list of available services that match to the client’s criteria. o The client uses the list to retrieve additional service attribute for the service of interest. Profiles • Profiles are specifications which describe how Bluetooth should be used in a specific application and thus ENSURES that all devices from different manufacturers can seamlessly work with one another. • There are about a dozen profiles: Generic Access, Serial Port, Dial up Networking, FAX, Headset, LAN, Access Point, Generic Object Exchange (OBEX), File Transfer, Object Push, Synchronization, Cordless Telephony, and Intercom. • The profile concept is used to decrease the risk of interoperability problems between different manufacturers’ products. Telephony Control Protocol Specification Binary (TCS-BIN) • To define call control signaling for the establishment of voice and data calls between Bluetooth devices TCS-BIN describes a binary, packet-based, bit-oriented protocol. |
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