ECE 6160: Advanced Computer Networks Wireless LAN and Bluetooth - PowerPoint PPT Presentation

Loading...

PPT – ECE 6160: Advanced Computer Networks Wireless LAN and Bluetooth PowerPoint presentation | free to view - id: 22789-NjA3N



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

ECE 6160: Advanced Computer Networks Wireless LAN and Bluetooth

Description:

Future appliances may include cameras, automobiles, pets, security systems, ... two nodes, hidden from each other, transmit complete frames to base station ... – PowerPoint PPT presentation

Number of Views:85
Avg rating:3.0/5.0
Slides: 49
Provided by: iwebT
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: ECE 6160: Advanced Computer Networks Wireless LAN and Bluetooth


1
ECE 6160 Advanced Computer NetworksWireless
LAN and Bluetooth
  • Instructor Dr. Xubin (Ben) He
  • Email Hexb_at_tntech.edu
  • Tel 931-372-3462

2
Prev
  • multimedia applications and requirements
  • making the best of todays best effort service
  • scheduling and policing mechanisms
  • next generation Internet Intserv, RSVP, Diffserv

3
Why Wireless?
  • Human freedom
  • Portability v. Mobility
  • Objective anything, anytime, anywhere
  • Mobility
  • Size, weight, power
  • Functionality
  • Content
  • Infrastructure required
  • Cost
  • Capital, operational

4
Wireless Links
  • The wave of the future for networking wireless
    links
  • Examples of end systems
  • Portable PCs, PDAs, airport hubs, wireless
    telephony (such as the cellphone pictured)
  • Future appliances may include cameras,
    automobiles, pets, security systems, kitchen
    appliances, and plants.
  • IEEE 802.11b most popular standard wireless
    LANs
  • Bluetooth new standard that allows devices to
    communicate with each other
  • Three classifications
  • Power, range, data rate
  • Bluetooth low, short, low
  • 802.11 high, medium, high

5
(No Transcript)
6
Wireless LAN Configurations
CLIENT AND ACCESS POINT
WIRELESS PEER-TO-PEER
BRIDGING WITH DIRECTIONAL ANTENNAS
MULTIPLE ACCESS POINTS ROAMING
UP TO 17 KM !
SOURCE PROXIM.COM
7
Wireless Standards
  • 802.11b (2.4 GHz 300 radius 11 Mbps)
  • 802.11a (5 GHz 54 Mbps incompatible with b)
  • 802.11g (2.4 GHz 54 Mbps backward compatible with
    b)
  • 802.20 (1 Mbps _at_250 kph)
  • BlueTooth (2.4 Ghz 30 radius)
  • GSM (9.6 Kbps) GPRS (28.8 Kbps up to 60 Kbps )
  • 3G (UMTS 1.1 Mbit/s shared typically giving 80
    Kbit/s )
  • 4G 2010? (10 Mbs? )
  • UWB potential to deliver 500 Mbps over short
    distances

SOURCE JOHN DOWNARD
8
(No Transcript)
9
IEEE 802.11 Wireless LAN
  • 802.11b
  • Currently most popular form of wireless LAN
    wireless Ethernet, Wi-Fi
  • 2.4 GHz unlicensed radio spectrum
  • up to 11 Mbps
  • physical layer and Media Access Control (MAC)
    layer for wireless local area network
  • direct sequence spread spectrum (DSSS) in
    physical layer
  • all hosts use same chipping code
  • widely deployed.

10
IEEE 802.11 Wireless LAN
  • Other wireless LAN standards
  • 802.11a operates on 5.1-5.8GHz range and uses
    OFDM (orthogonal frequency-division
    multiplexing), Speeds can get up to 54Mbps
  • 802.11g operates at 2.4GHz, Speeds up to 54Mbps
  • All use CSMA/CA for multi-access and have base
    stations and ad-hoc network versions

11
Base station approach (Infrastructure)
  • Wireless host communicates with a central base
    station (AP)
  • Basic Service Set (BSS) (a.k.a. cell) contains
  • wireless hosts (wireless stations)
  • access point (AP) central base station
  • BSSs combined to form distribution system (DS)

12
(No Transcript)
13
Ad Hoc Network approach
  • No AP (i.e., central base station)
  • wireless hosts communicate with each other
  • to get packet from wireless host A to B may need
    to route through wireless hosts X,Y,Z
  • Applications
  • laptop meeting in conference room, car
  • interconnection of personal devices
  • battlefield
  • IETF MANET (Mobile Ad hoc Networks) working
    group

14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
IEEE 802.11 multiple access
  • Collision if 2 or more nodes transmit at same
    time
  • CSMA makes sense
  • get all the bandwidth if youre the only one
    transmitting
  • shouldnt cause a collision if you sense another
    transmission
  • Collision detection doesnt work hidden terminal
    problem

19
IEEE 802.11 MAC Protocol CSMA/CA
  • 802.11 CSMA sender
  • - if sense channel idle for DISF sec.
  • then transmit entire frame (no collision
    detection)
  • -if sense channel busy then binary backoff
  • 802.11 CSMA receiver
  • - if received OK
  • return ACK after SIFS
  • (ACK is needed due to hidden terminal problem)

20
Collision avoidance mechanisms
  • Problem
  • two nodes, hidden from each other, transmit
    complete frames to base station
  • wasted bandwidth for long duration !
  • Solution
  • small reservation packets
  • nodes track reservation interval with internal
    network allocation vector (NAV)

21
(No Transcript)
22
Collision Avoidance RTS-CTS exchange
  • sender transmits short RTS (request to send)
    packet indicates duration of transmission
  • receiver replies with short CTS (clear to send)
    packet
  • notifying (possibly hidden) nodes
  • hidden nodes will not transmit for specified
    duration NAV

23
Collision Avoidance RTS-CTS exchange
  • RTS and CTS short
  • collisions less likely, of shorter duration
  • end result similar to collision detection
  • IEEE 802.11 allows
  • CSMA
  • CSMA/CA reservations
  • polling from AP

24
More Info
  • Wireless Communications and Networks, by William
    Stallings, Part Four, Prentice Hall, 2002
  • Wireless LANs Status Today and Visions for
    Future, by Anand R. Prasad, Lucent.
  • Wireless Glossary

25
A word about Bluetooth (802.15)
  • Interference from wireless LANs, digital cordless
    phones, microwave ovens
  • frequency hopping helps
  • MAC protocol supports
  • error correction
  • ARQ
  • Low-power, small radius, wireless networking
    technology
  • 10 meters or so
  • Interconnects gadgets
  • 2.4-2.5 GHz unlicensed radio band
  • up to 721 kbps

26
Bluetooth
  • A standard permitting for wireless
    connection of
  • Personal computers
  • Printers
  • Mobile phones
  • Handsfree headsets
  • LCD projectors
  • Modems
  • Wireless LAN devices
  • Notebooks
  • Desktop PCs
  • PDAs

27
Bluetooth Devices
ALCATEL One TouchTM 700 GPRS, WAP
ERICSSON R520 GSM 900/1800/1900
ERICSSON BLUETOOTH CELLPHONE HEADSET
NOKIA 9110 FUJI DIGITAL CAMERA
ERICSSON COMMUNICATOR
28
Bluetooth Application Areas
  • Bluetooth provides support for 3 general
    application areas using short range wireless
    connectivity
  • Data and voice access points
  • Real-time voice and data transmissions
  • Cable replacement
  • Eliminates need for numerous cable attachments
    for connection
  • Ad hoc networking
  • Device with Bluetooth radio can establish
    connection with another when in range

29
Profiles Bluetooth usage models
  • Set of protocols to implement a particular
    Bluetooth-based application, defined as profile.
  • File transfer
  • Internet bridge
  • LAN access
  • Synchornization phone book, task lists
  • Three-in-one phone
  • Headset act as a remote devices audio I/O

30
The ultimate headset
  • Bluetooth removes the cable between the headset
    and the telephone.
  • The user of a headset is not physically tied to
    the audio device and is free to roam about the
    area.
  • The same headset can be used with multiple
    devices.
  • The same headset used with
  • a telephone might also be used
  • with a cordless telephone base
  • station and could be used for
  • audio interaction with computers.
  • Using voice recognition it may
  • be possible to place telephone
  • calls using only headset as
  • the user interface.

31
The three in one phone
  • The three in one usage model allows a mobile
    telephone to be used
  • as a cellular phone in the standard manner.
  • As a cordless phone connecting to a voice access
    point.
  • As a an walkie-talkie for direct phone-to-phone
    communication with another device in proximity
    (why to use it when you can shout ?).

32
File Transfer
  • In an interactive conference room scenario,
    business cards and files could be exchanged among
    the participants.

33
Dial-up networking
  • Todays usage models for dial-up networking
    require a cable between the computer and
    telephone.
  • Even when a mobile telephone is used, a cable
    between a computer and the mobile telephone is
    required.
  • If computer and telephone support dial-up
    networking profile the connection can be wireless.

34
Direct network access
  • It is possible to implement LAN bridges where one
    port has Bluetooth interface instead of the wired
    serial access.

35
Piconets and Scatternets
  • Piconet
  • Basic unit of Bluetooth networking
  • Master and one to seven slave devices
  • Master determines channel and phase
  • Scatternet
  • Device in one piconet may exist as master or
    slave in another piconet
  • Allows many devices to share same area
  • Makes efficient use of bandwidth

36
Scatternet
Piconet B
Piconet A
Active slave A1
Active slave B1
Master B
Active slave A2 Active slave B3
Master A
Active slave B2
Active slave A3
37
(No Transcript)
38
Master and Slave roles in piconet
  • A given master may communicate with up to 7
    active slaves and up to 255 parked slaves.
  • All slaves communicating with a single master
    form a piconet.
  • There can be only one master in a single piconet.
  • In the higher protocol layers, devices operate
    as peers

Slave1
Master
Slave2
piconet
Slave3
39
(No Transcript)
40
Communications topology
  • The Bluetooth network model uses peer-to-peer
    communications based on proximity.
  • The slaves within the area of proximity can form
    a piconet.

Proximity sphere
Active slave
Standby slave
Parked slave
Master
sniff slave
Standby slave
hold slave
Active slave
Piconet
41
Communications topology
  • It is possible for a device to take part in more
    than one piconet.
  • When two or more piconets at least partially
    overlap in time and space a scatternet is formed.
  • Each piconet has its own hopping pattern
    determined by the master.
  • A slave could participate in multiple piconets by
    establishing connections with different masters
    in proximity.
  • A single device might act as a slave in one
    piconet but be the master in another piconet.

42
Physical Links between Master and Slave
  • Synchronous connection oriented (SCO)
  • Allocates fixed bandwidth between point-to-point
    connection of master and slave
  • Master maintains link using reserved slots
  • Master can support three simultaneous links
  • Asynchronous connectionless (ACL)
  • Point-to-multipoint link between master and all
    slaves
  • Only single ACL link can exist

43
(No Transcript)
44
Bluetooth Packet Fields
  • Access code used for timing synchronization,
    offset compensation, paging, and inquiry
  • Header used to identify packet type and carry
    protocol control information
  • Payload contains user voice or data and payload
    header, if present

45
Frequency Hopping in Bluetooth
  • Provides resistance to interference and multipath
    effects
  • Provides a form of multiple access among
    co-located devices in different piconets

46
Frequency Hopping
  • Total bandwidth divided into 1MHz physical
    channels
  • FH occurs by jumping from one channel to another
    in pseudorandom sequence
  • Hopping sequence shared with all devices on
    piconet (FH channel)
  • Piconet access
  • Bluetooth devices use time division duplex (TDD)
  • Access technique is TDMA
  • FH-TDD-TDMA

47
ARQ Scheme Elements
  • Error detection destination detects errors,
    discards packets
  • Positive acknowledgment destination returns
    positive acknowledgment
  • Retransmission after timeout source retransmits
    if packet unacknowledged
  • Negative acknowledgment and retransmission
    destination returns negative acknowledgement for
    packets with errors, source retransmits

48
More info
  • http//www.palowireless.com/bluetooth/
  • http//www.bluetooth.org
  • http//www.tutorial-reports.com/wireless/bluetooth
    /
About PowerShow.com