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 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

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

Protocol Architecture

Core Protocols Radio Baseband Link manager protocol (LMP) 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

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

Bluetooth Protocols RFCOMM Telephony control protocol (TCS BIN) 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

Usage Model

Usage Model (cont)

Usage Model (cont)

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

Master/Slave Relationships

Wireless Network Configurations

Wireless Network Configurations

Radio & Baseband Parameters

Radio Specification

Baseband Specification 1600 hops per second

Baseband Specification (cont)

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

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

Baseband Specification (cont)

Baseband Specification (cont)

Baseband Specification (cont)

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

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

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

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 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

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

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

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

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

Baseband Specification (cont) State diagram

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

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

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

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

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

Link Manager Specification

Link Manager Specification (cont)

L2CAP

L2CAP Formats

L2CAP Signaling Command Code

L2CAP Quality of Service Flow specification Service type Token rate (bytes/second) Token bucket size (bytes) Peak bandwidth (bytes/second) Latency (microseconds) Delay variation (microseconds)

L2CAP Quality of Service