4.4 WIRELESS LANS
4.4.1 The 802.11 Architecture
• WIRELESS LANS:
– informal name: Wifi
– IEEE group number : 802.11
• The 802.11 architecture
– infrastructure mode: each client is connected with
an AP (Access Point)
– ad hoc mode: no access point
• Since there is no Internet access, ad hoc networks are
not very popular.
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infrastructure mode
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ad hoc mode
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4.4.1 The 802.11 Protocol Stack
• The data link layer:
– the MAC (Medium Access Control) sublayer:
determines how the channel is allocated, that is,
who gets to transmit next.
– the LLC (Logical Link Control) sublayer: hide the
differences between the different network
technologies
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4.4.1 The 802.11 Protocol Stack (Cont.)
• The physical layer(deals with transmission
techniques):
– Infrared
– frequency hopping
– spread spectrum
– OFDM (Orthogonal Frequency Division
Multiplexing) scheme
• All above transmission techniques generally
use the unlicensed frequency Band 2.4 GHz
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4.4.1 The 802.11 Protocol Stack
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4.4.5 Services
• The association service : to connect mobile
stations to APs.
• The Reassociation service : lets a station
change its preferred AP
• The Authentication service : database to
determine if the station is allowed to access
the network.
– The recommended scheme, called WPA2 (WiFi
Protected Access 2)
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4.4.5 Services
• The integration service : handles any translation
that is needed for a frame to be sent outside the
802.11 LAN, or to arrive from outside the 802.11
LAN.
• Data delivery service: lets stations transmit and
receive data
• The privacy service : manages the details of
encryption and decryption
• A companion service : provides higher-layer timer
synchronization
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4.5 BROADBAND WIRELESS
broadband
• broadband refers to telecommunication in
which a wide bandwidth of frequencies that
are available to transmit information.
• Broadband can allow remote stations(devices)
to connect to a central station at high speeds.
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Example on Broad Band Technologies
• Telephone System Broad Band Technologies
– Plain old telephone service (POTS)
– Integrated Services for Digital Network (ISDN)
– Digital subscriber line (DSL)
• Cable Television Technology
• Satellites Technology
• Cellular Communication Technology
– (BroadBand Wireless)
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4.5 BROADBAND WIRELESS
• informal name: WiMax
• IEEE group number : 802.16
• Comparison of 802.16 with 802.11 (similarities):
– 802.11, 802.16 is based on OFDM technology
– 802.11, 802.16 transmission medium is the radio waves
• Comparison of 802.16 with 802.11 (differences)
– 802.16 base stations uses more power and better antennas
– 802.16 base stations perform more processing to handle errors
and weaker signals over larger distances.
– 802.16 base station carefully schedules transmissions for each
subscriber
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4.5.2 The 802.16 Architecture
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4.5.2 The 802.16 Protocol Stack
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4.5.2 The 802.16 Protocol Stack
• The physical layer ( deals with transmission
techniques)
•
• The data link layer:
– Security layer: deals with privacy and security
– MAC common layer: determines how the channel is
allocated, that is, who gets to transmit next.
– The service-specific convergence sublayer (like LLC) :
hide the differences between the different network
technologies
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4.6 BLUETOOTH
Wireless Networks
PAN
802.15.x
10m
LAN
802.11
100m
MAN
802.16
2-6km
WAN
2G, 3G
2km/link
national
areas
Overview of wireless networks
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Bluetooth
• IEEE group number of Wireless PAN (Personal
Area Network including Bluetooth) : 802.15
• The key features of Bluetooth technology are:
–
–
–
–
Short Range and Small Networks
Robustness (high levels of security)
low power,
and low cost.
• Bluetooth uses the unlicensed 2.4 GHz ISM band
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What does Bluetooth do for you?
Landline
Cable
Replacement
Data/Voice
Access Points
Personal Ad-hoc
Networks
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4.6.1 Bluetooth Architecture
• The basic unit of a Bluetooth system
is a piconet;
• A Piconet: it consists of a master
node (for synchronization purposes)
and up to seven active slave nodes
nodes within a distance of 10 meters.
• there can be up to 255 parked nodes
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4.6.1 Bluetooth Architecture (cont.)
• A Scatternet : is interconnected
collection of piconets.
• Multiple piconets can be connected via
a bridge slave node
• The reason for the master/slave design
is to facilitate the implementation of
cheap complete Bluetooth chips
• direct slave-slave communication is not
possible: the slaves just do whatever
the master tells them to do.
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4.6.1 Bluetooth Architecture
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