Bluetooth
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Bluetooth. Mohamed Mokdad Ecole d’Ingénieurs de Bienne. What is Bluetooth?. Data transmission standard Between different kinds of terminals E.g. PC, Printer, PDA, Phone, Radio Link Bitrate: Up to 1 mbps Security: It’s secured It’s not intended for permanent connection. History.

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Bluetooth

Bluetooth

Mohamed Mokdad

Ecole d’Ingénieurs de Bienne


What is bluetooth

What is Bluetooth?

  • Data transmission standard

  • Between different kinds of terminals

    • E.g. PC, Printer, PDA, Phone,

  • Radio Link

  • Bitrate: Up to 1 mbps

  • Security: It’s secured

  • It’s not intended for permanent connection


History

History

  • Ericsson starts developping it in 1994

  • Other joined: IBM, Nokia, etc

  • The group is named: Bluetooth SIG

    • SIG = Special Interest Group

  • Bluetooth SIG

    • Specifications

    • Profiles


How it works

How it works?

  • Radio link between 2 terminals

  • On short distances up to 10 meters

  • Special arrangements up to 100 meters

  • Theoritical Bitrate up to 720 kbps

  • 1 Master & 1+ Slave terminals (up to 7)

  • Link: only Master to Slave

    • No slave to slave links

  • Frequency Hopping


The applications

The Applications

  • PC to PDA synchronisation

  • Printing everywhere

  • Headsets

  • Mobile phone to PDA

  • COM Devices


Components overview

Components Overview


The architecture piconet

The architecture: Piconet

Single slave operation

Multi slaves operation

Scatternet operation


Specs radio channel

Specs – Radio Channel

  • 2.4 GHz – Bandwidth 79 MHz

  • 1 MHz frequency hops, i.e. 79 hops

  • Not everywhere available spectrum

    • E.g. France: limitation to 23 MHz bandwidth

  • Reach of 10 m with 2.5 mW

    • 2.5 mW ~ 4 dBm, i.e. Log(2.5mW/1mW)

    • The cell is the Piconet

  • 3 power classes: 1, 2.5 & 100 mW


Radio interface features

Radio interface features

  • Power control with RSSI – LMP

    • Receiver Signal Strength Indicator (dBm)

    • Allows power adjustment for Class 1 (High)

    • Optional for Power Classes 2 and 3

  • Key features of Bluetooth

    • Robustness, low complexity

    • low power, low cost.

  • Frame number 0 to 227-1 & cycles @ 227

  • Master sends in even slots (0, 2, 4, …)


Physical layer

Physical Layer

  • Channel divided in 625 ms slots

  • Every slot @ a different frequency hop

  • A packet can be

    • Less then one slot

    • One slot

    • More then one slot (up to five)

  • Next packet starts on next slot

  • One packet per frequency hop


Packets hops

Packets & Hops


Packets hops1

Packets & Hops


Transmission mode sco

Transmission mode - SCO

  • Synchronous Connection-Oriented

    • SCO

    • Point to point connection in the Piconet

    • Regular reserved transmission slots

    • Speech connections @ 64 kbps

    • Maximum of 3 Master-Slave simultaneous connections


Transmission mode acl

Transmission mode - ACL

  • Asynchronous Connection-Less

    • ACL

    • One single connection

    • No slot reservation

    • More then one connection @ the same time

    • And with more then one slave


Sco acl

SCO & ACL


The packet

The packet

  • Access Code

  • - Channel Access Code:Identifies the Piconet

  • - Device Access Code:     Identifies the access type

  • Inquiry Access Code:     Identifies the request

  • Header for addressing, error correction and flow control

  • Payload for Data 


Overview of major states

Overview of major states

  • Standby state

    • Default state

    • Low power comsuption

    • No interaction with any other terminal

    • Synchronised (Clock active)

  • Connection state

    • Dialog state

    • Master clock for synchronisation


Connection state modes

Connection state modes

  • Active mode

    • Participating to a connection

  • Sniff mode

    • Reduction of the slave listening activity

  • Hold mode

    • No ACL support, but just SCO support

    • Frees capacity for other slaves

  • Park mode

    • Remains synchronised and keeps addresses


Connection modes

Connection modes


Hold mode

Hold Mode


Sniff mode

Sniff Mode


The protocol stack

The protocol stack


Base band

Base Band

  • Physical channels

    • Time slots @ 625 ms

  • Physical links

    • SCO and ACL

  • Packets

    • Access code, packet header and types

  • Error correction

    • 1/3, 2/3 and ARQ scheme


Logical channels

Logical channels

  • Logical channels (5)

    • LC = Link Control

      • Low level link control: ARQ, Flow, etc.

    • LM = Link Manager

      • Peer protocol between Link Mgr (Master/Slave)

    • UA = User Asynchronous Data

      • Different clocks & Synchronization per byte

    • UI = User Isochronous Data

      • Clock in data & mainly no error checking

    • US = User Synchronous Data

      • Synchronized clocks & Error checking


Logical channels ua ui us

Logical channels UA/UI & US

  • UA/UI

    • Carried over ACL links

  • US

    • Carried over SCO links

  • LC mapped in the packet header

  • The other in the payload


Packet hierarchy

Packet Hierarchy

PSM: Protocol Service Multiplexer, i.e. SPD, RFCOMM or TCP


Acl packets

ACL Packets


Sco packets

SCO PAckets


Packets transmit receive

Packets Transmit & Receive

  • Transmit & Receive Routines

    • The standard makes suggestion

    • There is no obligation to implement

  • It looks like V.24 interface

    • Transmit Buffer

    • Receive Buffer

  • It’s however much more complicated


Link manager protocol

Link Manager Protocol


Link manager protocol1

Link Manager Protocol

  • Link Setup

  • Link Control

  • Link Security

  • LM PDU

    • Link Manager Protocol Data Unit

  • LM PDU always sent in the payload and

  • Always as single-slot packets


The procedures

The Procedures

  • General response messages

  • Authentication

  • Pairing

  • Change Link Key

  • Change Current Link Key

  • Encryption

  • Switch of Master-Slave Role

  • QoS


Pairing

Pairing

  • No link key available

  • Generate one based on

    • Random number, BD_ADDR, PIN

  • Initiator and Responder

    • Reject or

    • Accept and create link key


Authentication

Authentication

  • Secret Key

    • Based on Challenge, BD_ADDR, secret link key

  • Claimant and Verifier

    • Has key

    • Has no key


L2cap

L2CAP

  • Logical Link Control & Adaptation Protocol

  • Higher layer protocols

    • Packet Segmentation & Reassembly (SAR)

    • Multiplexing

    • QoS

  • Supports ACL and no SCO Links

  • Simplicity and low overhead

  • Applicable to equipment with low power resources: PDAs, Cellular phones, …


Stack

Stack


L2cap does not support

L2CAP does not support

  • L2CAP does not transport audio designated for SCO links.

  • L2CAP performs no retransmissions or checksum calculations.

  • L2CAP does not perform any CRC Calculation


Payload format

Payload Format

LMP = 1 slot packets

L2CAP = 1 or more slots packets


Channel coding

Channel Coding

To be noted

10 = Start of L2CAP packet

01 = Continuation of L2CAP packet


Channels summary

Channels Summary


Channels types

Channels types


Channels types1

Channels types

  • Connection oriented data channels

    • Both ways connection

    • Normal CID

  • Connectionless channels

    • One way channel

    • Reserved CID

    • E.g Signaling

  • Signaling channel is mandatory


L2cap services

L2CAP Services

8

5

4

1

2

7

6

3


Segmentation

Segmentation

L2CAP over Baseband: segment in Baseband packets to send over the air

L2CAP over HCI:segment in block sized chunks to send to the HCI

This will segment to Baseband packet to send over the air

The scenario is: L2CAP to Baseband to L2CAP


Usb based example

USB based Example


Profiles

Profiles

  • Bluetooth SIG Profiles

    • Different profiles

  • Devices Interoperability

    • Not all Bluetooth devices can interoperate

  • Service and use case

    • Specify the supported services

  • Describe the air interface

    • For the profile


Type of support

Type of support

  • Mandatory

    • Define profile's capabilities

  • Optional

    • Define profile's capabilities that can be used

  • Conditional

    • In conjunction with some other capability

  • eXcluded

    • Should not be used in this profile

  • Not Applicable


Profiles1

Profiles

  • GENERIC ACCESS - @ least

  • SERVICE DISCOVERY APPLICATION

  • CORDLESS TELEPHONY

  • INTERCOM

  • SERIAL PORT

  • HEADSET

  • DIAL-UP NETWORKING

  • FAX

  • LAN ACCESS

  • GENERIC OBJECT EXCHANGE

  • OBJECT PUSH

  • FILE TRANSFER

  • SYNCHRONIZATION


Profile description

Profile description

  • Scope

    • What is its usage: service and use case

  • Dependencies

    • What other profiles are required

  • Stack

    • Which element of the stack are involved

  • The protocols

    • @ the different layers: LM, L2CAP, …


E g generic profile stack

E.g. Generic Profile Stack


E g dial up networking stack

E.g. Dial-Up Networking Stack


E g generic object ex stack

E.g. Generic Object Ex. Stack


Generic access

Generic Access

  • This profile defines the generic procedures related to discovery of Bluetooth devices (idle mode procedures) and link management aspects of connecting to Bluetooth devices (connecting mode procedures). It also defines procedures related to use of different security levels. In addition, this profile includes common format requirements for parameters accessible on the user interface level.


Service discovery application

Service Discovery Application

  • This document defines the features and procedures for an application in a Bluetooth device to discover services registered in other Bluetooth devices and retrieve any desired available information pertinent to these services.


Headset

Headset

  • This profile defines the requirements for Bluetooth devices necessary to support the Headset use case. The requirements are expressed in terms of end-user services, and by defining the features and procedures that are required for interoperability between Bluetooth devices in the Headset use case.


Serial port

Serial Port

  • This profile defines the requirements for Bluetooth devices necessary for setting up emulated serial cable connections using RFCOMM between two peer devices. The requirements are expressed in terms of services provided to applications, and by defining the features and procedures that are required for interoperability between Bluetooth devices.


Dial up networking

Dial-Up networking

  • This profile defines the requirements for Bluetooth devices necessary for the support of the Dial-up Networking use case. The requirements are expressed in terms of enduser services, and by defining the features and procedures that are required for interoperability between Bluetooth devices in the Dialup Networking use case.


Generic object exchange

Generic Object Exchange

  • This profile defines the requirements for Bluetooth devices necessary for the support of the object exchange usage models. The requirements are expressed by defining the features and procedures that are required for interoperability between Bluetooth devices in the object exchange usage models.

Underlying profile


Object push

Object Push

  • This application profile defines the application requirements for Bluetooth devices necessary for the support of the Object Push usage model. The requirements are expressed in terms of end-user services, and by defining the features and procedures that are required for interoperability between Bluetooth devices in the Object Push usage model.

Objects examples: Business Card, Appointment


File transfer

File Transfer

  • This application profile defines the application requirements for Bluetooth devices necessary for the support of the File Transfer usage model. The requirements are expressed in terms of end-user services, and by defining the features and procedures that are required for interoperability between Bluetooth devices in the File Transfer usage model.


Synchronization

Synchronization

  • This application profile defines the application requirements for Bluetooth devices necessary for the support of the Synchronization usage model. The requirements are expressed in terms of end-user services, and by defining the features and procedures that are required for interoperability between Bluetooth devices in the Synchronization usage model.

Synchronization of objects


Lan access

LAN Access

  • This document is a LAN Access Profile for Bluetooth devices. Firstly, this profile defines how Bluetooth-enabled devices can access the services of a LAN using PPP. Secondly, this profile shows how the same PPP mechanisms are used to form a network consisting of two Bluetooth-enabled devices.

PPP = Point-to-Point Protocol


Bluetooth

Fax

  • This profile defines the requirements for Bluetooth devices necessary for the support of the Fax use case. The requirements are expressed in terms of end-user services, and by defining the features and procedures that are required for interoperability between Bluetooth devices in the Fax use case.


Cordless telephony

Cordless Telephony

  • This profile defines the features and procedures that are required for interoperability between different units active in the ‘3-in-1 phone’ use case. The scope of this profile includes the following layers/protocols/ profiles: Bluetooth Baseband, Link Manager Protocol, L2CAP, Service Discovery Protocol, Telephony Control Protocol Specification (TCS-Binary) and the General Access Profile.


Intercom

Intercom

  • This profile defines the requirements for Bluetooth devices necessary for the support of the intercom functionality within the 3-in-1 phone use case. The requirements are expressed in terms of end-user services, and by defining the features and procedures that are required for interoperability between Bluetooth devices in the 3-in-1 phone use case.


Data whitening

Data whitening

  • Randomize the data

    • No redundant patterns

  • Minimize DC bias in the packet

    • To reduce the DC offset

    • i.e. DC value tends to 0

  • Generated with a polynomial

    • As for CRC-16, CRC-32


Packet hierarchy1

Packet Hierarchy

PSM: Protocol Service Multiplexer, i.e. SPD, RFCOMM or TCP


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