T3 wireless.ppt [Modo de compatibilidad] · 2009-09-24 · Free-space loss and frequency dependency ... Omni-Directional Antenna "A hypothetical, lossless antenna having equal radiation

http://www.redes.upv.es/ralir/en/

3.- Wireless technologies

�Basics

� Applications

� The physical media

� Free-space loss and frequency dependency

� The IEEE 802 specification family

� Comparison between different wireless technologies (PHY and

Local Area Networks/School of Engineering in Computer Science/2009-2010


� Comparison between different wireless technologies (PHY and MAC layers)

� IEEE 802.11

�Bluetooth

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Sci

enceWireless? Why?

� Mobility (anytime)

� Coverage (anywhere)

� New applications potential (services)� Healthcare

� Lab administration

� People with disabilities

� Point-of-Care testing

� Homecare administration

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� Homecare administration

� Controlling patient data

� Education

� More efficient learning methods

�Wireless is ideal for campus-wide coverage

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Some Application Areas

� Retail� Direct inventory management

� Mobile POS

� Self-checkout

� Mobile scanners

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� Manufacturing� Field based data collections

� Product management

� Inventory visibility and planning

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Vehicular Networks

� Safety and transport efficiency� In Europe around 40,000 people die and more than 1.5 millions are injuredevery year on the roads

� Traffic jams generate a tremendous waste of time and of fuel

� Most of these problems can be solved by providing appropriateinformation to the driver or to the vehicle

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http://www.redes.upv.es/ralir/en/4

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Vehicle Communication (VC)

� VC promises safer roads,

� … more efficient driving,

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Vehicle Communication (VC)

� … more fun,

� … and easier maintenance.

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Rural communications

� Rural communications on the global agenda� Connecting villages with Information and Communication Technologies (ICT) and establishing community access points

� Benefits� E-business and e-commerce could play an important role in enabling local artisans to reach national and international markets

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Yasuhiko Kawasumi, “Rural communications on the global agenda,” Global Survey on Rural Communications for the ITU-D on Communications for rural and remote areas.

Over 40% of the world’s population lives in rural and remote areas of developing countries and have difficult or no access to even basic telecommunications services. Development of telecommunications in rural and remote areas, therefore forms an important mission of the ITU Development sector.

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Rural populations and their ICT needs

� Needs of rural people in connection with e-services � E-health, e-education and e-administration top the list as primary needs

� E-business and e-banking also scored highly

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ITU-D global survey, Doc 111/SG2

For many rural areas, electricity supply is simply non-existent or insufficient

Telemedicine Training in Bhutan by Tokai University:Telemedicine Training in Bhutan by Tokai University: Tokai University Institute of Medical Sciences donated the medical equipments with ICT functions and provided the training on the use of equipments. Tokai University Second Opinion center provides the assistance service over the internet when requested by the Bhutanese ends.

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About the “Wireless Internet”

WWAN (3G,4G?)

WLAN (Wi-Fi)

WMAN (Wi-Max)

BluetoothRFID

High throughput, short range

Low throughput, Long range

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Low throughput, short range WPAN

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Big Picture – WPAN’s

� WPAN technologies – RFID, Bluetooth

� RFID used in tagging applications, restricted environments (supermarkets, institutions)

� 10 billion RFID tags to be sold by the end of 2005 (source: Deloitte & Touche)

� Bluetooth – technology has matured

� 56% of mainstream devices commercialised will have Bluetooth

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� 56% of mainstream devices commercialised will have Bluetooth support by 2008 (Source: IDC)

� Poor interoperability between vendors restricts the wide use of Bluetooth

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Big Picture – WLAN’s

� WLAN – based on WiFi (802.11x)

� Adoption rate increased worldwide� Up 51% more units sold globally in 2004 compared to 2003 (source: Infonetics Research)

� European cities’ infrastructure facilitates the adoption of WiFi against wired alternatives

� Old buildings

� High population density

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� High population density

� Poor telecommunications infrastructure

� Wi-Fi mesh infrastructure:� Current backend implementations of Wi-Fi mesh infrastructure are based on proprietary solutions

� Usage: wireless coverage of WLANs, blanketing large areas with hot-spot coverage

� Coverage: 100m to 10km

� Data rate:54Mbps- 100Mbps

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Big Picture –WMAN’s

� WiMax (Worldwide Interoperability for Microwave Access)

� Standards-based technology

� Deployment of broadband wireless networks based on the IEEE 802.16 standard

� Enables the delivery of last mile wireless broadband access as an alternative to cable and DSL

� Some characteristics of the 802.16- 2004 standard:

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� Some characteristics of the 802.16- 2004 standard:� Improve user connectivity

� Higher quality of services

� Full support for WMAN service

� Robust carrier-class operation

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Big Picture –WMAN’s Mobile Networks Evolution

UMTS

HSDPA

Download

Speed

1-10 Mbps

250-384 kbps

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GPRS

EDGE

19951995 2015201520052005

90-180 kbps

40 kbps



�Basics

� Applications








� IEEE 802.11

�Bluetooth

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Sci

enceAntennas basics

� Directional Antenna

� "An antenna having the property of radiating or receiving electromagnetic waves more effectively in some directions than others".

YAGI Directional Antenna

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� Omni-Directional Antenna

� "A hypothetical, lossless antenna having equal radiation intensity in all directions". For a WLAN antenna, the gain in dBi is referenced to that of an omni-directional (isotropic) antenna (which is defined as 0 dBi).

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Directional antennasLo

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Yagi antenna (13,5 dBi)

reach: 6 Km at 2 Mb/s

2 Km at 11 Mb/sParabolic antenna (20 dBi)

reach: 10 Km at 2 Mb/s

4,5 Km at 11 Mb/s

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More antennas examplesLo

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Horizontal Radiation

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ISM frequency bands

ISM (Industrial, Scientific and Medical) frequency bands:

• 900 MHz band (902 … 928 MHz)

• 2.4 GHz band (2.4 … 2.4835 GHz)

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• 2.4 GHz band (2.4 … 2.4835 GHz)

• 5.8 GHz band (5.725 … 5.850 GHz)

Anyone is allowed to use radio equipment for transmitting in these bands (provided specific transmission power limits are not exceeded) without obtaining a license.

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ISM frequency band at 2.4 GHz

The ISM band at 2.4 GHz can be used by anyone as long as (in Europe...)

Transmitters using FH (Frequency Hopping) technology:

• Total transmission power < 100 mW

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• Power density < 100 mW / 100 kHz

Transmitters using DSSS technology:


• Power density < 10 mW / 1 MHz

ETSI

EN 300 328-1 requirements

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Sci

enceFree-space loss

The free-space loss L of a radio signal is:

2 24 4d df

Lc

π π

λ

= =

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cλ

where d is the distance between transmitter and receiver, λ is the rf wavelength, f is the radio frequency, and c is the speed of light. The formula is valid for d >> λ , and does not take into account antenna gains (=> Friis formula) or obstucting elements causing additional loss.

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Power budget graphical representationLo

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�Basics

� Applications








� IEEE 802.11

�Bluetooth

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IEEE 802 wireless network technology options

Network definition

Wireless personal area network (WPAN)

IEEE standard

IEEE 802.15.1

Known as

Bluetooth

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Low-rate WPAN (LR-WPAN)

Wireless local area network (WLAN)

Wireless metroplitan area network (WMAN)

IEEE 802.15.4

IEEE 802.11

IEEE 802.16

ZigBee

WiFi

WiMAX

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IEEE 802 standardisation framework

802.1

Manage-ment

802.3 802.5

802.2 Logical Link Control (LLC)

802.11 Medium Access Control (MAC)

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MAC

802.3

PHY

MAC

802.5

PHY

802.11

PHY

802.11a

PHY

802.11b

PHY

802.11g

PHY

CSMA/CD

(Ethernet)

CSMA/CA

Token

RingCSMA/CA (Wireless LAN)

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CSMA/CA Wireless LAN


CSMA/CA = Carrier Sense Multiple Access with Collision Avoidance

Unlike wired LAN stations, WLAN

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802.11

PHY

802.11a

PHY

802.11b

PHY

802.11g

PHY

CSMA/CAstations, WLAN stations cannot detect collisions

=>

avoid collisions A common MAC layer, but many

PHY options

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WLAN physical layer (1)


The original physical layer specified in 802.11 defines two signal formats:

FHSS (Frequency Hopping Spread

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802.11

PHY

802.11a

PHY

802.11b

PHY

802.11g

PHY

CSMA/CA

Hopping Spread Spectrum)

DSSS (Direct Sequence Spread Spectrum)

Data rates supported: 1 and 2 Mbit/s. ISM band: 2.4 … 2.4835 GHz

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The first widely implemented physical layer was 802.11b that uses:

DSSS (Direct Sequence Spread

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802.11

PHY

802.11a

PHY

802.11b

PHY

802.11g

PHY

CSMA/CA

Sequence Spread Spectrum) like in 802.11 but with larger bit rates:1, 2, 5.5, 11 Mbit/s

Automatic fall-back to lower speeds in case of bad radio channel.

ISM band: 2.4 … 2.4835 GHz

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802.11a operates in the 5.8 GHz band.

The signal format isOFDM (Orthogonal

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802.11

PHY

802.11a

PHY

802.11b

PHY

802.11g

PHY

CSMA/CA

5 GHz frequency band

OFDM (Orthogonal Frequency Division Multiplexing)

Data rates supported: Various bit rates from 6 to 54 Mbit/s.

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802.11g is the most recent physical layer, operating in the same band as 802.11b

The signal format isOFDM (Orthogonal

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802.11

PHY

802.11a

PHY

802.11b

PHY

802.11g

PHY

CSMA/CA

ISM band: 2.4 … 2.4835 GHz

OFDM (Orthogonal Frequency Division Multiplexing)

Data rates supported: Various bit rates from 6 to 54 Mbit/s (same as 802.11a)

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Wireless Fidelity (WiFi)


The WiFi certification program of the Wireless EthernetCompatibility Alliance (WECA) addresses compatibility of IEEE 802.11 equipment

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802.11

PHY

802.11a

PHY

802.11b

PHY

802.11g

PHY

CSMA/CA

WiFi

802.11 equipment

=>

WiFi ensures interoperability of equipment from different vendors. WiFi5

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Wireless Personal Area Network (WPAN)

802.1

Manage-ment

802.3

MAC

802.5

MAC

802.15.1

802.2 LLC

802.11

MAC

802.15.4 802.16

Data rates up

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MAC

802.3

PHY

MAC

802.5

PHY

802.11

PHY

MAC

+

PHY

MAC MAC

+

PHY

MAC

+

PHY

Bluetooth Special Interest Group (SIG)

ISM band: 2.4 … 2.4835 GHz

Data rates up to 700 kbit/s (2.1 Mbit/s)

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Low-rate WPAN (LR-WPAN)

802.15.1 802.15.4 802.16

802.1

Manage-ment

802.3

MAC

802.5

MAC

802.2 LLC

802.11

MAC

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MAC

+

PHY

MAC

+

PHY

MAC

+

PHY

MAC

802.3

PHY

MAC

802.5

PHY

802.11

PHY

MAC

ISM band: 2.4 … 2.4835 GHz

ZigBee Alliance

Data rates up to 250 kbit/s

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Wireless Metropolitan Area Network (WMAN)

802.15.1 802.15.4 802.16

802.1

Manage-ment

802.3

MAC

802.5

MAC

802.2 LLC

802.11

MAC Various data

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MAC

+

PHY

MAC

+

PHY

MAC

+

PHY

MAC

802.3

PHY

MAC

802.5

PHY

802.11

PHY

MAC

Various frequency bands (not only ISM)

WiMAX

Various data rates up to 100 Mbit/s and more



�Basics

� Applications








� IEEE 802.11

�Bluetooth

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Possible architectures

� Independent Basic Service Set (IBSS)

� Decentralized structure

� Flexible:

� Permanent and temporary networks

� Allows to control power consumption

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� infrastructure Basic Service Set (BSS)

� Components:

� Station (STA)

� Access Point (AP)or Point Coordinator (PC)

� Basic Service Set (BSS)

� Extended Service Set (ESS)

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The Extended Service Set (ESS)

BSS

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BSS

AP

WLAN LAN

� The standard does not define the implementation

details� exists a proposal by a

group of industries:Inter-acces point protocol (IAPP)

Distribution System (DS)

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Task Group f

� Scope of Project: to develop recommended practices for an Inter-Access Point Protocol (IAPP) which provides the necessary capabilities to achieve multi-vendor Access Point interoperability across a Distribution System supporting IEEE P802.11 Wireless LAN Links.

� Purpose of Project: ... including the concepts of Access Points and Distribution Systems. Implementation of these concepts where purposely not defined by P802.11 ... As 802.11 based systems have grown in popularity, this limitation has become an impediment to WLAN market growth.

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WLAN market growth.

This project proposes to specify the necessary information that needs to be exchanged between Access Points to support the P802.11 DS functions. The information exchanges required will be specified for, one or more Distribution Systems; in a manner sufficient to enable the implementation of Distribution Systems containing Access Points from different vendors which adhere to the recommended practices

� Status: Work has been completed and is now part of the Standard as a recommended practice.

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enceFrames structure

Types of addresses:

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• management (00)• control (01), • data (10), • reserved (11)

• Source address (SA)

• Destination Address (DA)

• Transmitter Address (TA)

• Receiver Address (RA)

• BSS identifier (BSSID)

SADATARA11Wireless DS

-DASARA = BSSID01To the AP

-SABSSIDRA = DA10From the AP

-BSSIDSARA = DA00IBSS

Addr. 4Addr. 3Addr. 2Addr. 1From DS

To DS

Función

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BSSID y SSID

� BSSID (Basic Service Set Identity)� BSS: AP’s MAC address� Ad-Hoc: 46 bit random number

� SSID (Service Set ID)� Known as the Network Name� Length: 0~32 bytes

� 0: is the broadcast SSID

� Handled either manually or automaticallyShould be unique; used to distinguish WLAN

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� Should be unique; used to distinguish WLAN� Access point and station that would like to form a unique WLAN should use the same SSID

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Addressing and DS bits

DA

DS

RA (BSSID)SA/TA

ClientAP SA

AP

AP

TA

Client

RA

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SADATARA11Wireless DS

-DASARA = BSSID01To the AP

-SABSSIDRA = DA10From the AP

-BSSIDSARA = DA00IBSS

Addr. 4Addr. 3Addr. 2Addr. 1From

DS

To

DS

Función

Server

DA

Server

ClientDA

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Services

� The IEEE 802.11 architecture defines 9 services: for the station and for the distribution

� Station services:� Authentication

� Deauthentication

� Privacy � WEP

� Data delivery

� Distribution services:

Similar to connect/disconnect a

cable to a traditional network

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� Distribution services:� Association � generates a connection between a STA and a AP

� Disassociation

� Reassociation � like association but informing about the previous AP

� Distribution

� integration � connects the WLAN with other LANs;

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State variables and services

State 1:

unauthenticated,

unassociated

State 2:

Successful authentication Deauthentication notification

Class 1 & 2

Class 1frames

Deauthentication notification

In a IBSS there is neither auth., nor ass.

Data service is allowed

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State 2:

authenticated,

unassociated

State 3:

authenticated,

associated

Disassociation notificationSuccessful authenticationor reassociation

Class 1, 2 & 3 frames

Class 1 & 2 frames

Deauthentication notification

A STA can be

authenticated with

various AP but it

can be associated

with only one AP

A STA can be

authenticated with

various AP but it

can be associated

with only one AP

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Scanning

� Parameters: BSStype, BSSID, SSID, ScanType, ChannelList, ProbeDelay, Min/MaxChannelDelay

� ScanType: Passive� The stations wait for the APs beacons

� ScanType: Active� Stations send probe requests

� scan report are generated

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� The following phase is joining; this phase precedes the sequence of actions up to association

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The MAC: reliable data delivery

� CSMA/CA with binary exponential backoff

� The minimum protocol consists of two frames: the data and the ACK

Point Coordination

Function (PCF)

Distributed Coordination Function (DCF)

MAC

No contentionWith contention

The 5 timing values:• Slot time• SIFS: short interframe space (< slot

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DIFS DIFS

PIFS

SIFS

Contention window

defer access

busy medium

slot

• SIFS: short interframe space (< slot time)

• PIFS: PCF interframe space (=SIFS+1slot)• DIFS: DCF interframe space (=SIFS+2slots)• EIFS: extended interframe space

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� The back off values are chosen inside the congestion window. That is, inside the interval [0, CW]

� CW can vary between 31 slots (CWmin) and 1023 slots (CWmax)

� CW is incremented after every failed sending and reset after every successful transmission

B1 = 5B1 = 25

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data

wait

B1 = 5

B2 = 15

data

wait

B2 = 20

� B1 and B2 are the back off interval at STA 1 and 2� CW = 31

B2 = 10

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Problematic configurations

Exposed nodeHidden node

AA

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B

C

BC

D

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RTS/CTS mechanism

� Based on the network allocation vector (NAV)

RTS

DIFS

datasource

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CTS

SIFS

ACK

SIFS SIFS

DIFS

NAV (RTS)

NAV (CTS)

destination

other STA

defer access

Contention window

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PCF: Point Coordination Function

Data+Poll

DATA+ACKBeacon

Data+Poll

ACK

CF-End

PIFS SIFS SIFS SIFS SIFS

SIFS

(no response)

PIFS

CP

PC

STA1

Contention Free Period CP

Data+Poll

SIFS

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Station 2 sets NAV(Network Allocation Vector)STA2 NAV

Reset

TimeSTA3 Station 3 is hidden to the PC, it does not set the NAV.

It continues to operate in DCF.

• Beacons are used to keep timers in the stations synchronized and to

send control information

• The AP generates beacons at regular intervals

• Stations know when the following beacon is arriving

�The target beacon transmission time (TBTT) is announced in the previous beacon

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PCF: the superframe

� There is an repetition of contention-free (CFP) and contention (CP) periods

� A CFP and the following CP form a superframe.

CF-PollCF-End

802.11 periodic Superframe

CFP(Contention Free Period) CP(Contention Period)

PC

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BeaconDATA DATA DATA DATA DATA DATASTAs

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enceBroadcast trafic

� It is not possible to fragment frames whose destination is a group address

� Acknowledgement are not sent

� MAC does not offer any retransmission service to broadcast or multicast frames

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� The standard defines 14 channels, 22 MHz wide

� FCC only uses the first 11

� In Spain only channel 10 and 11

� 3 channel do not overlap (1, 6,11)

� data rate is 11 Mbps

51



�Basics

� Applications








� IEEE 802.11: SECURITY

�Bluetooth

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Wireless LAN Security Issues

Issue

� Wireless sniffer can view all WLAN data packets

� Anyone in AP coverage area can get on WLAN

802.11 WEP Solution

� Encrypt all data transmitted between client and AP

� Without encryption key, user cannot transmit or receive data

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Wireless LAN (WLAN)

Wired LAN

Goal: Make WLAN security equivalent to that of wired LANs (Wired Equivalent Privacy)

client access point (AP)

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WEP – Protection for 802.11b

� Wired Equivalent Privacy� No worse than what you get with wire-based systems.

� Criteria:� “Reasonably strong”

� Self-synchronizing – stations often go in and out of coverage

� Computationally efficient – in HW or SW since low MIPS CPUs might be used

� Exportable – US export codes (relaxed in Jan 2000 / “Wassenaar

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� Exportable – US export codes (relaxed in Jan 2000 / “Wassenaar Arrangement”)

� Optional – not required to used it

� Objectives:� confidentiality

� integrity

� authentication

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WEP – How It Works

� Secret key (40 bits or 104 bits)

� can use up to 4 different keys

� Initialization vector (24 bits, by IEEE std.)

� total of 64 or 128 bits “of protection.”

� RC4-based pseudo random number generator (PRNG)

� Integrity Check Value (ICV): CRC 32

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IV

(4 bytes)

Data (PDU)

(≥ 1 byte)

Init Vector(3 bytes)

1 byte

Pad6 bits

Key ID2 bits

Frame headerICV

(4 bytes)FCS

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WEP Encryption Process

1) Compute ICV using CRC-32 over plaintext msg.

2) Concatenate ICV to plaintext message.

3) Choose random IV and concat it to secret key and input it to RC4 to produce pseudo random key sequence.

4) Encrypt plaintext + ICV by doing bitwise XOR with key sequence to produce ciphertext.

5) Put IV in front of cipertext.

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5) Put IV in front of cipertext.

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InitializationVector (IV)

Secret Key

Plaintext

Integrity Algorithm

Seed WEP PRNG

KeySequence

Integrity Check Value (ICV)

IV

CiphertextMessage

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WEP Decryption Process

1) IV of message used to generate key sequence, k.

2) Ciphertext XOR k � original plaintext + ICV.

3) Verify by computing integrity check on plaintext (ICV’) and comparing to recovered ICV.

4) If ICV ≠ ICV’ then message is in error; send error to MAC management and back to sending station.

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IV

Ciphertext

Secret Key

Message

WEP PRNG

Seed

Key

Sequence

Integrity Algorithm

Plaintext

ICV’

ICV

ICV’ - ICV

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WEP Station Authentication

� Wireless Station (WS) sends Authentication Request to Access Point (AP).

� AP sends (random) challenge text T.

� WS sends challenge response (encrypted T).

� AP sends ACK/NACK.

WS APAuth. Req.

Challenge Text

Challenge Response

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Challenge Response

Ack

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Sci

enceWEP Weaknesses

� Forgery Attack� Packet headers are unprotected, can fake src and dest addresses.

� AP will then decrypt data to send to other destinations.

� Can fake CRC-32 by flipping bits.

� Replay � Can eavesdrop and record a session and play it back later.

� Collision (24 bit IV; how/when does it change?)� Sequential: roll-over in < ½ day on a busy net

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� Sequential: roll-over in < ½ day on a busy net

� Random: After 5000 packets, > 50% of reuse.

� Weak Key� If ciphertext and plaintext are known, attacker can determine key.

� Certain RC4 weak keys reveal too many bits. Can then determine RC4 base key.

� Well known attack described in Fluhrer/Mantin/Shamir paper� “Weaknesses in the Key Scheduling Algorithm of RC4”, Scott Fluhrer, Itsik

Mantin, and Adi Shamir

� using : http://www.aircrack-ng.org/59

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Ways to Improve Security with WEP

� Use WEP(!)

� Change wireless network name from default

� any, 101, tsunami

� Turn on closed group feature, if available in AP

� Turns off beacons, so you must know name of the wireless network

� War Driving in New Orleans (back in December 2001)

� Equipment

� Laptop, wireless card, software

� GPS, booster antenna (optional)

� Results

� 64 Wireless LAN’s

� Only 8 had WEP Enabled (12%)

� 62 AP’s & 2 Peer to Peer

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network

� MAC access control table in AP

� Use Media Access Control address of wireless LAN cards to control access

� Use 802.11i support if available in AP

� Define user profiles based on user name and password

� 62 AP’s & 2 Peer to Peer Networks

� 25 Default (out of the box) Settings (39%)

� 29 Used The Company Name For ESSID (45%)

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War Driving in New Orleans (back in December 2001)

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Sci

enceOther solutions

� VPN Connectivity � PPTP

� L2TP

� Third Party

� IPSec� Many vendors

� Password-based Layer 2 Authentication� Cisco LEAP

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� Cisco LEAP

� RSA/Secure ID

� IEEE 802.1x PEAP/MSCHAP v2

� Certificate-based Layer 2 Authentication� IEEE 802.1x EAP/TLS

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WLAN Security TypeSecurity Level

Ease of Deployment

Usability and Integration

IEEE 802.11 Low High High

WLAN Security ComparisonsLo

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VPN Medium Medium Low

Password-based Medium Medium High

IPSec High Low Low

IEEE 802.1x TLS High Low High

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802.1X

� Defines port-based access control mechanism� Works on anything, wired and wireless

� Access point must support 802.1X

� No special encryption key requirements

� Allows choice of authentication methods using EAP� Chosen by peers at authentication time

� Access point doesn’t care about EAP methods

� Manages keys automatically

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� Manages keys automatically� No need to preprogram wireless encryption keys

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Wi-Fi Protected Access (WPA)

� A specification of standards-based, interoperable security enhancements that strongly increase the level of data protection and access control for existing and future wireless LAN systems

� Goals� Enhanced Data Encryption (TKIP)

� Provide user authentication (802.1x)

� Be forward compatible with (802.11i)

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� Be forward compatible with (802.11i)

� Provide non-RADIUS solution for Small/Home offices WPA-PSK

� Typically a software upgrade and Wi-Fi Alliance began certification testing for interoperability on Wi-Fi Protected Access products in February 2003

� WPA2

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Wi-Fi Protected Access (WPA)

� WEPs IV only 24 bits and so are repeated every few hours �

WPA increased IV to 24 bits repeated 900 years

� WPA alters values acceptable as IVs

� Protects against forgery and replay attacks� IV formed MAC address

� TSC

� TKIP: New password generated every 10,000 packets

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� WPA-PSK � Passphrase

� WPA 802.ii1 recommend 20-character password

� Crack is brute force based

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�Basics

� Applications








� IEEE 802.11: CONFIGURATION

�Bluetooth

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Linksys Wireless-G Access PointLo

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�Bluetooth



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enceBluetooth 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

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� 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

� Currently (July 2007): release 2.1+EDR

� Next specification (2Q08) will include ability to utilize additional radio technologies to enable high speed Bluetooth applications.

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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

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� 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.

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� Lower Power Consumption� Reduced 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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enceBluetooth usage

� Low-cost, low-power, short range radio � a cable replacement technology� Common (File transfer, synchronisation, internet bridge, conference table)

� Hidden computing (background synchronisation, audio/video player)

� Future (PC login, remote control)

� Why not use Wireless LANs?� power

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� cost

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Bluetooth RF

� 1 Mb/s symbol rate

� Normal range 10m (0dBm)

� Optional range 100m (+20dBm)

� Normal transmission power 0dBm (1mW)

� Optional transmission power -30 to +20dBm (100mW)

� Receiver sensitivity -70dBm

� Frequency band 2.4Ghz ISM band

� Gross data rate 1Mbit/s

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� Gross data rate 1Mbit/s

� Max data transfer 721+56kbps/3 voice channels

� Power consumption 30uA(max), 300uA(standby), ~50uA(hold/park)

� Packet switching protocol based on frequency hop scheme with 1600 hops/s

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Bluetooth Power Class Table

50m16m4dBm2.5mWClass 2

300m42m20dBm100mWClass 1

Range inFree Space

Expected RangeMax Output PowerMax Output PowerPower Class

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30m10m0dBm1mWClass 3

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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.

o Scatternet: A Scatternet is a group of Piconets linked via a slave device in one Piconet which plays master role in other Piconet.

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oone Piconet which plays master role in other Piconet.

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M

S

i) Piconet (Point-to-Point)

M

SS

S

S

ii) Piconet (Multipoint)

M

S S S

M

S S

Master/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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Bluetooth stack: short version

L2CAP

SDPRFCOMM

Applications

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RF

Baseband

Link Manager

L2CAP

HCI

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Transport Protocol Group (contd.)

� 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

� 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.

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� Enforcing Fairness among slaves.

� Power Management

� Logical Link Control & Adaptation Protocol

� Handles multiplexing of higher level protocols

� Segmentation & reassembly of large packets

� Device discovery & QoS

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

BLUETOOTH SPECIFICATION, Core Version 1.1 page 543

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ence End to End Overview of Lower Software Layers to

Transfer Data

BLUETOOTH SPECIFICATION, Core Version 1.1 page 544

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Physical Link Definition

� Synchronous Connection-Oriented (SCO) Link� circuit switching

� symmetric, synchronous services

� slot reservation at fixed intervals

� Asynchronous Connection-Less (ACL) Link� packet switching

� (a)symmetric,

� asynchronous services

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� asynchronous services

� polling access scheme

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enceACL data rates

Packet type Name Symmetric (kbps)

Asymmetric (kbps)

1 slot + FEC DM1 108.8 108.8 108.8

1 slot DH1 172.8 172.8 172.8

3 slot + FEC DM3 256.0 384.0 54.4

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3 slot + FEC DM3 256.0 384.0 54.4

3 slot DH3 384.0 576.0 86.4

5 slot + FEC DM5 286.7 477.8 36.3

5 slot DH5 432.6 721.0 57.6

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Multi-slot packets

Single slot

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

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Three slot

Five slot

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Symmetric single slot

fn fn+1 fn+2 fn+3 fn+4 fn+5 fn+6 fn+7 fn+8 fn+9 fn+10 fn+11 fn+12

Master

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Master

Slave

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Mixed Link Example

MASTER

SLAVE 1

ACL ACLSCO SCO SCO SCO ACLACL

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SLAVE 2

SLAVE 3

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Sci

ence Polling on ACL links

� Slave is allowed to send only after it has been polled.

� Master polls slave at least Npoll slots (negotiated).

� Master may send at will.

� Polling algorithm is proprietary.

Master

DataPOLL

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time

Master

Slave

Data

Slot

TDD frame

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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

A

CHB

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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)

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E

G

H

D

I

CF

Master

Bluetooth Connection States

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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

Master

Inquiry

Inquiry Scan

Inquiry Response

Slave

3

2

1

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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.

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Page

Page Scan

Slave Response

Master Response

Connection

Connection

3

4

5

7

6

Forming a Piconet Procedures

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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

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� 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, or

� Browse 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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Sci

encePacket Structure

Control packets Data/voice packets

data

ID*NullPoll

72 bits 54 bits 0 - 2745 bits

Access Code Header Payload Guard

220µs

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Voicedata

HV1HV2HV3DV

(136 bits) DM1DM3DM5

DH1DH3DH5 (2712 bits)

PollFHSDM1

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

DataHeader CRC

•ARQ

•CRC

•FEC (optional)

•No retries

•No CRC

•FEC (optional)

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Documents

T3 wireless.ppt [Modo de compatibilidad] · 2009-09-24 · Free-space loss and frequency dependency ... Omni-Directional Antenna "A hypothetical, lossless antenna having equal radiation