redes inalámbricas – tema 2.b wireless pans: bluetooth

REDES INALÁMBRICAS Máster de Ingeniería de Computadores-DISCA

Redes Inalámbricas – Tema 2.BWireless PANs: Bluetooth

Bluetooh Acknowledgments: Foo Chun Choong, Ericsson Research / Cyberlab

Singapore, and Open Source Software Lab, ECE Dept, NUS

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IEEE 802.15 Working Group for WPAN

IEEE Std 802.15.1™-2002 - 1Mb/s WPAN/Bluetooth v1.x derivative work

802.15.2™- Recommended Practice for Coexistence in Unlicensed Bands

802.15.3™ - 20+ Mb/s High Rate WPAN for Multimedia and Digital Imaging

802.15.3a™ - 110+ Mb/s Higher Rate Alternative PHY for 802.15.3

802.15.4™ - 200 kb/s max for interactive toys, sensor and automation needs ZigBee

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Bluetooth Market

Installed base of Bluetooth enabled products reached 1 Billion devices in November of 2006.

Every week, 13 million Bluetooth units are shipped. (~675 million per year or 21 every second)

Every working day, more than five new Bluetooth enabled products are qualified. (~1300 per year)

Broad surveys have shown that the Bluetooth brand is recognized by more than 75% of respondents world-wide. (Millward Brown internet survey for Bluetooth SIG: Bluetooth.org)

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4 The Bluetooth Wireless Experience

Replaces cables connecting portable and/or fixed devices while maintaining high levels of security,

Robust, low power, low cost solution, Any Bluetooth enabled device, almost everywhere in the

world, can connect to other Bluetooth enabled devices in proximity,

Bluetooth enabled devices with common profiles work together to provide a uniform user experience.

http://bluetooth.com/Bluetooth/Press/SIG/Bluetooth_SIG_LAUNCHES_NEW_PROGRAM_FOR_ENHANCED_VISIBILITY_OF_IBLUETOOTHI_FUNCTIONALITY.htm

HEADSET PRINTING TRANSFER MUSIC HID

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Bluetooth history De facto standard - open specifications.

publicly available on Bluetooth.com: http://bluetooth.com/Bluetooth/Technology/Works/

Bluetooth specs developed by Bluetooth SIG. February 1998: The Bluetooth SIG is formed

promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba May 1998: The Bluetooth SIG goes “public” July 1999: 1.0A spec (>1,500 pages) is published December 1999: ver. 1.0B is released December 1999: The promoter group increases to 9

3Com, Lucent, Microsoft, Motorola February 2000: There are 1,500+ adopters

Versions: 0.7 0.9 1.0A 1.0B 1.1 …

November 2003: release 1.2 November 2004: release 2.0+EDR

(EDR or Extended Data Rate) triples the data rate up to about 3 Mb/s July 2007: release 2.1+EDR April 2009: release 3.0+HS

http://bluetooth.com/Bluetooth/Technology/Works/

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Versions

The 1.2 version, unlike the 1.1, provides a complementary wireless solution to co-exist Bluetooth and Wi-Fi in the 2.4 GHz spectrum without interference between them. uses the technique "Adaptive Frequency Hopping (AFH), which runs a

more efficient transmission and a more secure encryption. offers voice quality (Voice Quality - Enhanced Voice Processing) with less

noise, and provides a faster configuration of communication with other Bluetooth devices within range of reach.

Version 2.0, created to be a separate specification, mainly incorporates the technique "Enhanced Data Rate (EDR)” that allows you to improve transmission speeds up to 3Mbps while trying to solve some errors specification 1.2.

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Release 2.1 Near Field Communication (NFC) Technology

NFC may also be used in the new pairing system, enabling a user to hold two devices together at a very short range to complete the pairing process.

Lower Power ConsumptionReduced power consumption means longer battery life in devices like

mice and keyboards. Bluetooth Specification Version 2.1 + EDR can increase battery life by up to five times.

Improved Security For pairing scenarios that require user interaction, eavesdropper protection

makes a simple six-digit passkey stronger than a 16-digit alphanumberic character random PIN code. Improved pairing also offers "Man in the Middle" protection that in reality eliminates the possibility for an undetected middle man intercepting information.

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Release 3.0

It supports theoretical data transfer speeds of up to 24 Mbit/s. Its main new feature is AMP (Alternate MAC/PHY), the addition

of 802.11 as a high speed transport. Two technologies had been anticipated for AMP: 802.11 and

UWB, but UWB is missing from the specification. Alternate MAC/PHY

Enables the use of alternative MAC and PHYs for transporting Bluetooth profile data. The Bluetooth Radio is still used for device discovery, initial connection and profile configuration, however when lots of data needs to be sent, the high speed alternate MAC PHY (802.11, typically associated with Wi-Fi) will be used to transport the data.

And also: Unicast connectionless data Read encryption key size Enhanced Power Control

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Bluetooth Power Class Table

Power Class Max Output Power

Max Output Power

Expected Range

Range inFree Space

Class 1 100mW 20dBm 42m 100m

Class 2 2.5mW 4dBm 16m 50m

Class 3 1mW 0dBm 10m 30m

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10 Bluetooth Network Topology

Bluetooth devices have the ability to work as a slave or a master in an ad hoc network. The types of network configurations for Bluetooth devices can be three. Single point-to-point (Piconet): In this topology the network consists of

one master and one slave device. Multipoint (Piconet): Such a topology combines one master device and

up to seven slave devices in an ad hoc network. Scatternet: A Scatternet is a group of Piconets linked via a slave device

in one Piconet which plays master role in other Piconet.

M

Si) Piconet (Point-

to-Point)

M

SS S

S

ii) Piconet (Multipoint)

M

S S S

M

S SMaster/Slave

iii) Scatternet

The Bluetooth standard does not describe any routing protocol for scatternets and most of the hardware available today has no capability of forming scatternets. Some even lack the ability to communicate between slaves of one piconet or to be a member of two piconets at the same time.

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11 Bluetooth Protocol Stack: Transport Protocol Group

Radio Frequency (RF) Sending and receiving modulated

bit streams Baseband

Defines the timing, framing Flow control on the link.

Link Manager Managing the connection states. Enforcing Fairness among slaves. Power Management

Logical Link Control & Adaptation Protocol (L2CAP) Handles multiplexing of higher level

protocols Segmentation & reassembly of

large packets Device discovery & QoS

The Radio, Baseband and Link Manager are on firmware.

The higher layers could be in software.

The interface is then through the Host Controller (firmware and driver).

The HCI interfaces defined for Bluetooth are UART, RS232 and USB.

Source: Farinaz Edalat, Ganesh Gopal, Saswat Misra, Deepti Rao

BLUETOOTH SPECIFICATION, Core Version 1.1 page 543

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12 Bluetooth Protocol Stack: Middleware Protocol Group

RFBaseband

AudioLink ManagerL2CAP

Data

SDP RFCOMMIP

Cont

rol

Applications

Middleware Protocol Group

Additional transport protocols to allow existing and new applications to operate over Bluetooth. Packet based telephony control signaling protocol also present. Also includes Service Discovery Protocol.


Service Discovery Protocol (SDP) Means for applications to discover device info,

services and its characteristics.TCP/IP

Network Protocols for packet data communication, routing

RFCOMM Cable replacement protocol, emulation of serial

ports over wireless network

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13 Bluetooth Protocol Stack: Application Group

Application Group

RFBaseband

AudioLink ManagerL2CAP

Data

SDP RFCOMMIP

Cont

rol

Applications

Consists of Bluetooth aware as well as un-aware applications.


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14 SCO (Synchronous Connection-Oriented) payload types

Bluetooth offers two types of links: Synchronous connection-oriented link for classical telephone (voice)

connections: HV (High quality Voice), DV (Data and Voice) Asynchronous connectionless link for typical data applications: DM1

(Data Medium rate) and DH3 (Data High rate) with 3 slots

payload (30)

audio (30)

audio (10)

audio (10)

HV3

HV2

HV1

DV

FEC (20)

audio (20) FEC (10)

header (1) payload (0-9) 2/3 FEC CRC (2)

(bytes)

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15 ACL (Asynchronous connectionless Link) Payload types

payload (0-343)

header (1/2) payload (0-339) CRC (2)

header (1) payload (0-17) 2/3 FEC

header (1) payload (0-27)


header (2) payload (0-183)


header (2) payload (0-339)DH5

DM5

DH3

DM3

DH1

DM1

header (1) payload (0-29)AUX1

CRC (2)

CRC (2)

CRC (2)

CRC (2)

CRC (2)

CRC (2)

(bytes)

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16 Channel access Bluetooth devices use a Time-Division Duplex (TDD) scheme Channel is divided into consecutive slots (each 625 s) One packet can be transmitted per slot Subsequent slots are alternatively used for transmitting and

receiving Strict alternation of slots b/t the master and the slaves Master can send packets to a slave only in EVEN slots Slave can send packets to the master only in the ODD slots


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17 Multi-slot packets

Single slot

Three slot

Five slot

fn fn+1 fn+2 fn+3 fn+4 fn+5

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18 Mixed Link Example

MASTER

SLAVE 1

SLAVE 2

SLAVE 3

ACL ACLSCO SCO SCO SCO ACLACL

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19 Throughput

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20 Bluetooth Connection States There are four Connection states on

Bluetooth Radio: Active: Both master and slave

participate actively on the channel by transmitting or receiving the packets (A,B,E,F,H)

Sniff: In this mode slave rather than listening on every slot for master's message for that slave, sniffs on specified time slots for its messages. Hence the slave can go to sleep in the free slots thus saving power (C)

Hold: In this mode, a device can temporarily not support ACL packets and go to low power sleep mode to make the channel available for things like paging, scanning etc (G)

Park: Slave stays synchronized but not participating in the Piconet, then the device is given a Parking Member Address (PMA) and it loses its Active Member Address (AMA) (D,I)

E

A

G

H

C

D

I

H

C

B

F

Master

Bluetooth Connection States

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21 Bluetooth Forming a Piconet Inquiry: Inquiry is used to find the

identity of the Bluetooth devices in the close range.

Inquiry Scan: In this state, devices are listening for inquiries from other devices.

Inquiry Response: The slave responds with a packet that contains the slave's device access code, native clock and some other slave information.

Page: Master sends page messages by transmitting slave's device access code (DAC) in different hop channels.

Page Scan: The slave listens at a single hop frequency (derived from its page hopping sequence) in this scan window.

Slave Response: Slave responds to master's page message

Master Response: Master reaches this substate after it receives slave's response to its page message for it.

Master

Inquiry

Inquiry Scan

Inquiry Response

Page

Page Scan

Slave Response

Master Response

ConnectionConnection

Slave

3

2

4

1

5

7

6

Forming a Piconet Procedures

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22 Inquiry time

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23 SDP - Service Discovery

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

Some Bluetooth SDP Requirements (partial list) Search for services based upon service attributes and service classes Browse for services without a priori knowledge of services Suitable for use on limited-complexity devices Enable caching of service information

How it works? Establish L2CAP connection to remote device Query for services

Search for specific class of service, orBrowse for services

Retrieve attributes that detail how to connect to the service Establish a separate (non-SDP) connection to use the service

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24 Bluez

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25 Usage models

A number of usage models are defined in Bluetooth profile documents. A usage model is described by a set of protocols that implement a particular Bluetooth-based application. Some examples are shown on the following slides: File transfer LAN access Wireless headset Cordless (three-in-one) phone.

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26 File transfer application

Using the file transfer profile: A Bluetooth device can browse the file system of another Bluetooth device, can manipulate objects (e.g. delete objects) on another Bluetooth device, or - as the name implies - files can be transferred between Bluetooth devices.

SDP

RFCOMM

OBEX

File transfer application

L2CAP

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27 LAN access application

Using the LAN profile: A Bluetooth device can access LAN services using (for instance) the TCP/IP protocol stack over Point-to-Point Protocol (PPP).Once connected, the device functions as if it were directly connected (wired) to the LAN.

SDP

RFCOMM

PPP

LAN access application

L2CAP

TCP/IP (e.g.)

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28 Wireless headset application

Using the headset profile: According to this usage model, the Bluetooth-capable headset can be connected wirelessly to a PC or mobile

SDPRFCOMM

Headset application

L2CAP

Audio

phone, offering a full-duplex audio input and output mechanism.This usage model is known as the ultimate headset.

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29 Cordless (three-in-one) phone application

Using the cordless telephone profile: A Bluetooth device using this profile can set up phone calls to users in the PSTN (e.g. behind a PC acting as voice base

SDPTCS BIN

Cordless phone application

L2CAP

Audio

station) or receive calls from the PSTN. Bluetooth devices implementing this profile can also communicate directly with each other.

redes inalámbricas – tema 2.b wireless pans: bluetooth

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