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Bluetooth: Introduction

Bluetooth: Introduction. Reference: Chapter 15, Wireless Communications and Networks , by William Stallings, Prentice Hall. Overview. Initially developed by Ericsson in 1994 Using 2.4 GHz band (up to 720 kbps, 10m ) Provide consumer with the ability to do

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Bluetooth: Introduction

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  1. Bluetooth: Introduction Reference:Chapter 15, Wireless Communications and Networks, by William Stallings, Prentice Hall

  2. Overview • Initially developed by Ericsson in 1994 • Using 2.4 GHz band (up to 720 kbps, 10m) • Provide consumer with the ability to do • Make calls from a wireless headset connected remotely to a cell phone • Eliminate cables linking computers to printers, keyboards, and the mouse • Hook up MP3 players wirelessly • Set up home networks • Call home from a remote location to turn appliances on and off, set the alarm, and monitor activity

  3. Overview (cont) • Bluetooth Applications • Data and voice access points • Cable replacement • Ad Hoc networking

  4. Protocol Architecture

  5. Core Protocols • Radio • Details of the air interface, including frequency, the use of frequency hopping, modulation scheme, and transmit power • Baseband • Concerned with connection establishment within a piconet, addressing, packet format, timing and power control • Link manager protocol (LMP) • Responsible for link setup between BT devices and ongoing link management • Security aspects: authentication and encryption • Control and negotiation of baseband packet sizes

  6. Core Protocols (cont) • Logical link control and adaptation protocol (L2CAP) • Adapts upper-layer protocols to the baseband layer • Provide both connectionless and connection-oriented services • Service discovery protocol (SDP) • Device information, services, and the characteristics of the services can be queries to enable the establishment of a connection between two or more BT devices

  7. Bluetooth Protocols • RFCOMM • Cable replacement protocol • RFCOMM presents a virtual serial port that is designed to make replacement of cable technologies as transparent as possible • Provides for binary data transport and emulates EIA-232 control signals over the BT baseband layer • Telephony control protocol (TCS BIN) • Defines the call control signaling for the establishment of speech and data calls between BT devices

  8. Usage Model

  9. Usage Model (cont)

  10. Usage Model (cont)

  11. Piconets • Piconet • Basic unit of networking in BT • Consisting of a master and from 1 to 7 active slave devices • The radio designated as the master makes the determination of the channel and phase that shall be used by all devices on this piconet • A slave may only communicate with the master and may only communicate when granted permission by the master • A device in one piconet may also exist as part of another piconet and may function as either a slave or master in each piconet

  12. Master/Slave Relationships

  13. Wireless Network Configurations

  14. Wireless Network Configurations

  15. Radio & Baseband Parameters

  16. Radio Specification

  17. Baseband Specification 1600 hops per second

  18. Baseband Specification (cont)

  19. Baseband Specification (cont) • Physical links • Synchronous connection oriented (SCO) • Allocates a fixed bandwidth between a point-to-point connection involving the master and a single slave • The master maintains the SCO link by using reserved slots at regular intervals • The basic unit of reservation is two consecutive slots (one in each transmission direction) • The master can support up to 3 simultaneous SCO linkes, while a slave can support 2 or 3 SCO links • SCO packets are never retransmitted

  20. Baseband Specification (cont) • Asynchronous connectionless (ACL) • A point-to-multipoint link between the master and all the slaves in the piconet • In slots not reserved for SCO links • The master can exchange packets with any slave on a per-slot basis • Only a single ACL link can exist • For most ACL packets, packet retransmission is applied

  21. Baseband Specification (cont)

  22. Baseband Specification (cont)

  23. Baseband Specification (cont)

  24. Baseband Specification (cont) • Packet format • Access code: used for timing synchronization, offset compensation, paging and inquiry • Three types of access codes • Channel access code (CAC): identifies a piconet • Device access code (DAC): used for paging and its subsequent response • Inquiry access code (IAC): used for inquiry purposes • Header: used to identify packet type and to carry protocol control information • Payload: contains user voice or data, and in most cases a payload header

  25. Baseband Specification (cont) • Packet Header • AM_ADDR • 3-bit AM_ADDR contains the “active mode” address (temporary address assigned to this slave in this piconet) of one of the slaves • A transmission from the master to a slave contains that slave’s address • A transmission from a slave contains its address • The value 0 is reserved for a broadcast from the master to all slaves in the piconet • Type • Identifies the type of packet • For SCO: HV1, HV2, HV3 • For ACL: DM1, DM3, DM5, DH1, DH3, DH5

  26. Baseband Specification (cont) • Flow • Provides a 1-bit flow control mechanism for ACL traffic only • ARQN • Provides a 1-bit acknowledgement mechanism for ACL traffic protected by a CRC • If the reception was successful, an ACK (ARQN=1) is returned; otherwise a NAK (ARQN=0) is returned • SEQN • Provides a 1-bit sequential numbering scheme • HEC (Header Error Control) • An 8-bit error detection code used to protect the packet header

  27. Baseband Specification (cont) • Payload format • Payload header • An 8-bit header is defined for single-slot packets, and a 16-bit header is defined for multislot packets • Payload body: user information • CRC: 16-bit CRC code on data payload • Payload header • L_CH: identifies the logical channel • Flow: used to control flow at the L2CAP level • Length: the number of bytes of data in the payload, excluding the payload header and CRC

  28. Baseband Specification (cont) • Error correction • 1/3 rate FEC (forward error correction) • Used on the 18-bit packet header • For the voice field in an HV1 packet • Simply sending three copies of each bit • A majority logic is used • 2/3 rate FEC • Used in all DM packets, in the data field of the DV packets, in the FHS packet, an in the HV2 packet • Hamming code • Can correct all single errors and detect all double errors in each codeword

  29. Baseband Specification (cont) • ARQ (automatic repeat request) • Used with DM and DH packets, and the data field of DV packets • Similar to ARQ schemes used in data link control protocols • 1. Error detection • 2. Positive acknowledgement • 3. Retransmission after timeout • 4. Negative acknowledgement and retransmissions

  30. Baseband Specification (cont) • Logical Channels • Five types of logical data channels designed to carry different types of payload traffic • 1. Link control (LC) • Carries low level link control information: ARQ, flow control, payload characterization • The LC channel is carried in every packet except in the ID packet, which has no packet header • 2. Link manager (LM) • Transports link management information between participating stations • Support LMP traffic and can be carried over either an SCO or ACL link

  31. Baseband Specification (cont) • 3. User asynchronous (UA) • Carries asynchronous user data: normally carried over the ACL link • 4. User isochronous (UI) • Carries isochronous user data: normally carried over the ACL link but may be carried in a DV packet on the SCO link • 5. User synchronous (US) • Carries synchronous user data • This channel is carried over the SCO link

  32. Baseband Specification (cont) State diagram

  33. Baseband Specification (cont) • Inquiry procedure • The first step in establishing a piconet is for a potential master to identify devices in a range that wish to participate in the piconet • Once a device has responded to an Inquiry, it moves to the page scan state to await a page from the master in order to establish a connection • Page procedure • Once the master has found devices within its range, it is able to establish connections to each device, setting up a piconet

  34. Baseband Specification (cont) • Channel state • Standby • The default state, low-power state • Connection • The device is connected to a piconet as a master or a slave • Page • Device has issued a page • Used by the master to activate and connect to a slave • Master sends page message by transmitting slave’s device access code (DAC) in different hop channels • Page scan • Device is listening for a page with its own DAC

  35. Baseband Specification (cont) • Master response • A device acting as a master receives a page response from a slave • Slave response • A device acting as a slave responds to a page from a master • Inquiry • Device has issued an inquiry, to find the identity of the devices within range • Inquiry scan • Device is listening for an inquiry • Inquiry response • A device that has issued an inquiry receives an inquiry response

  36. Baseband Specification (cont) • Connection state • Active • The slave actively participates in the piconet by listening, transmitting and receiving packets • The master periodically transmits to the slaves to maintain synchronization • Sniff • The slave does not listen on every receive slot but only on specified slots for its message • The slave can operate in a reduced-power status the rest of the time

  37. Baseband Specification (cont) • Hold • The device in this mode does not support ACL packets and goes to reduced power status • The slave may still participate in SCO exchanges • Park • When a slave does not need to participate on the piconet but still is to be retained as part of the piconet, it can enter the park mode, which is a low-power mode with very little activity • The device is given a parking member address (PM_ADDR) and loses its active member (AM_ADDR) address • With the use of the park mode, a piconet may have more than seven slaves

  38. Link Manager Specification

  39. Link Manager Specification (cont)

  40. L2CAP

  41. L2CAP Formats

  42. L2CAP Signaling Command Code

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