Bluetooth Presentation

CONTENTs 1. History & Introduction 2. Architecture and Throughputs 3. Physical Layer and Physical Channels 4. Baseband Layer 5. Link Manager Protocol 6. Logical Link Control and Adaptation Protocol 7. RFCOMM Protocol 8. Service Discovery Protocol 9. Host Control Interface 10. Profiles 11. Conclusion

Why Bluetooth? Ø Ø Ø Ø

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Cable replacement between devices. Supported by major companies Low power consumption Connection can be initiated without user interaction. Devices can be connected to multiple devices at the same time.

1. History & Introduction Ø

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Bluetooth is a short-range wireless network originally intended to replace the cable(s) connecting portable and/or fixed electronic devices. Such a network is also sometimes called a PAN (Personal Area Network) Invented in 1994 by L. M. Ericsson, Sweden The first version was released July 1999. Named after Harald Blaatand “Bluetooth”, king of Denmark 940-981 A.D. Bluetooth SIG founded by Ericsson, IBM, Intel, Nokia and Toshiba in Feb 1998 More than 2100 members today Bluetooth version 1.0 and 1.1 2 have been released

2. Architecture and Throughputs 2.1 Architecture Ø

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In principle each unit is a peer with the same hardware capabilities Two or more Bluetooth units that share a channel form a piconet Only one master in a piconet. Upto 7 slaves A group of overlapping piconets is called a scatternet Users in a piconet share a 1 Mbps channel – individual throughput decreases drastically as more units are added The aggregate and individual throughput of users in a scatternet is much greater than when each user participates on the same piconet

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Piconets and Scatternet

Bluetooth Specification Protocol Stack

– Lower layer protocols: Baseband, LMP, L2CAP, service discovery protocol (SDP) – Interfacing protocols: RFCOMM – Applicative control specifications: TCS Binary, AT Commands – Applicative protocols: PPP, TCP/IP, OBEX, WAP, vCard, VCal, WAE

2.2 Throughputs and Versions Ø

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Several versions of the specifications exist.Version 1.0 offers a maximum bandwidth less than 1 Mbps for a range of about 10 m. The range depends on the equipment class. Three classes and hence three transmission powers are defined – Class 1: it is designed for high-range devices such as Bluetooth Access points (∼100 m), power characteristics: 20 dBm (100 mW) – Class 2: for normal PCs and portable plugged devices (∼10 m), power characteristics 4 dBm (2.5 mW) – Class 3: for low power devices (range less than 1 m), power characteristics: 0 dBm (1 mW) Version 2 offers a maximum bandwidth ranging from 2 to 3 Mbps. When Bluetooth goes to higher ranges it faces other standards such as Wimedia

3. Physical Layer and Physical Channels

Ø The physical layer is based, for the basic rate, on frequency hopping with GFSK modulation. The modulation produces 1M symbols for a total throughput of 712 Kbps. In this kind of modulation we generate a binary one by a positive frequency deviation, and a binary zero by a negative frequency deviation. The advantage of this technique is that it does not require complex demodulation

3.1 Frequency Bands and RF Channels Ø

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Bluetooth operation is in the 2.4 GHz ISM band. In most countries we have 83.5MHz that should be dedicated to this protocol. 79 channels are hence possible in this range with a bandwidth of 1 MHz per channel. Global Availability and License Free

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79

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83.5 Mhz

4. Baseband Layer Ø

Baseband is a layer that implements a very large amount of procedures linking the data transmission to the radio coding and modulation. Clock, data packet formats, master/slave roles, connection/sleep state machine management, link control and audio transmission and forward error correction (FEC) (coding also) are defined here.

4.1 Physical Characteristics Physical Channels. 1.

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It is represented by the pseudo-random sequence hopping the chosen 79or 23 among channels RF available in the 2.4 GHz band. The hopping sequence is unique for each piconet The channel is divided into intervals of time or slots Each interval of time corresponds to an RF frequency among the hopping sequence so that two consecutive slots correspond to two frequencies The multiplexing technique uses time division duplex (TDD), i.e. the master and slaves transmit alternatively (a master transmits in the even slots and the slaves in the odd slots). The intervals of time or slots are numbered and last 625 μs each one. A packet corresponds to the juxtaposition of 1–5 consecutive time slots when a packet has a size higher than 1 time slot (3 or 5 slots), one speaks about multi-slot transmission

Logical Links. Ø

Several types of links can be established between a master and one (or several) slave. We enumerate the used most here: -Synchronous connection oriented (SCO) SCO are used for: – Voice communications in circuit mode – Synchronous and symmetrical services

- Extended SCO (ESCO) ESCO are asymmetric links and they offer more packet types supported on their communications.

- Asynchronous connection oriented (ACL) ACL links are used for: – Data communication – Symmetrical and asymmetrical asynchronous services – Discovery and paging

4.2 Addressing Ø

Four types of addresses are used between Bluetooth devices

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BD_ADDR: Bluetooth device fixed address.

It is provided by the manufacturer.Each device must have a unique address. The length is 48 bits.corresponds to an MAC address Ø

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LT_ADDR: the address of the active Bluetooth member It is a 3-bit wide. number and it elucidates the secret behind the maximum number of eight nodes in a piconet.

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PM_ADDR: it is an address reserved to the non-active members. This address is on 8 bits and is valid only if the slave is parked.

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AR_ADDR: access request address

4.3 Bluetooth Packets Ø

There are several kinds of packets that are related to the different link types.According to the application, we identify globally three kinds of packets.

– Control packets: they are used between the server and slaves to carry information related to the radio (frequency hopping, clock) to the link (establishment, security) or to the connection (connection requests). – Synchronous packets SCO: they are used by the connection oriented links to carry voice. – Asynchronous packets ACL: they are used for ACL connections, so mainly best effort data traffic.

For each one of these types, several subcategories exist. The various types of packets which result from this list are shown hereafter.

– Voice data packets DV , DM x packets (x = 1,3 or 5) , DH y packet types (y = 1,3 or 5) , 2-DH1, 3-DH1 , ….

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Packet Formats.

Access code

Header

Payload

control packets In all, there are five types of control packets (ID, POLL, NULL, FHS, DM1)that are used for control of the channel Ø ID Packet It consists of the device access code (DAC) or inquiry access code .(IAC) and has a fixed length of 68 bits. It contains the node address an inquiry code to ask for a node with specific conditions

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Ø FHS Packet The FHS packet contains the MAC address of the sender It is coded with 2/3 FEC rate.This packet is used in the answers to the

page requests and Inquiry ones before the creation of the PICONET or when there is a role change.

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Access Code. – Channel access code (CAC) – Device access code (DAC) – Inquiry access code (IAC)

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Packet Header.

4.4 Error Control

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Error Control Codes. Header Error Check. CRC. 1/3 FEC Coding. 2/3 FEC Coding. Automatic Repeat Request (ARQ).

5. Link Manager Protocol As shown in Figure the Paging procedure triggers the device to get into connected state and triggers all possible LMP messages. This is done through LMP message. There are several states: – Standby – Page – Page scan – Master Response – Slave Response

– Inquiry – inquiry scan – Inquiry Response – Connection – Park

State diagram of bluetooth

Some LMP Procedures. Ø

LMP Host Connection Req, LMP Setup Complete :The basic connection establishment procedure is the connection request. Ithappens after paging a node.

6. Logical Link Control and Adaptation Protocol There are three types of L2CAP links: – Bidirectional channel links for signalling. – Data connection for bidirectional traffic. – Unidirectionnel multicast connections. This means that L2CAP manages multicast communications for Bluetooth

Some L2CAP Functions Ø Ø Ø Ø

Multiplexing Control Frame Format Quality of Service. Segmentation and Reassembly.

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Connection Establishment Two step process : Inquiry – to get device addr Paging – for Synchronization Inquiry : Uses the Inquiry hop sequence and the IAC Paging : Uses the Paging hop sequence and the DAC of the device to be paged

Connection Establishment Inquiry No master and slaves at this point

Inquiry

Inquiry pkt

Inquiry Scan FHS pkt

Device A

Inquiry Response

Device B

Connection Establishment Paging Master

Slave Page

Page pkt

Page Scan ID pkt

Master Page Response Assigns active addr

FHS pkt ID pkt

Slave Page Response Uses FHS to get CAC and clk info

POLL NULL

Connected

Connected

Connection Establishment times

Inquiry

Paging

Typical

5.12 s

0.64 s

Max

15.36 s

7.38 s

Connected

RFCOMM Ø

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Provide support for legacy applications that use serial cables The scope is point-to-point communication between Bluetooth-equipped devices. A serial cable emulation protocol Performs all the necessary functions for transferring serial data as well as modem control signals

SDP - Service Discovery Ø

Focus Ø Ø Ø

Service discovery within Bluetooth environment Optimized for dynamic nature of Bluetooth Services offered by or through Bluetooth devices

Typical Usage of SDP Ø

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Establish L2CAP connection to remote device Query for services Ø Ø

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Search for specific class of service, or Browse for services

Retrieve attributes that detail how to connect to the service

9.Host Controller Interface (HCI) Ø

HCI provides an interface with methods for uniform access to baseband functions and independent from the upper interface. Today we have USB, PCMCIA,PCI, RS232 and WAP interfaces already defined

10.profiles Ø Ø Ø Ø Ø Ø Ø Ø Ø

Service discovery application profile (SDAP), Cordless telephony profile (CTP), Serial Port Profile (SPP). Headset (HS) Dial-up networking profile (DNP), Fax FP (Fax Profile). Local area network profile (LAP), Generic object exchange profile (GOEP), File transfer profile (FTP),

Bluetooth Products

Bluetooth Mobile Phone, headset, PDAs

Cordless Bar code Scanner

Bluetooth printer and laptop with bluetooth adapter

11. Conclusion Ø

Bluetooth technology has certain assets: low power consumption, high level of integration, profiles, native management of the voice and it includes mechanisms for simple QoS and error control

Thank You