Mô tả:
Internet & Mobile Communications
Wireless LANs
Characteristics
Wi-Fi Research
IEEE 802.11
Mobile Internet 2010
Introduction
PHY
MAC
Management
Wi-Fi Alliance and IEEE 802.11
Need for standardisation
2
Mobility frequency regulation between
countries is necessary : common frequency
band
Limitation of battery usage
Limitation of interferences among different
equipments (antennas can help)
configuration as seamless as possible
Compatibillity with existing LAN technologies
Seamless for users and applications (location
aware applications…)
Mobile Internet 2010
Characteristics of wireless LANs
Advantages
–
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very flexible within the reception area
Ad-hoc networks without previous planning possible
(almost) no wiring difficulties (e.g. historic buildings, firewalls)
more robust against disasters like, e.g., earthquakes, fire - or
users pulling a plug...
Disadvantages
–
–
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typically very low bandwidth compared to wired networks
(1-10 Mbit/s)
many proprietary solutions, especially for higher bit-rates,
standards take their time (e.g. IEEE 802.11)
products have to follow many national restrictions if working
wireless, it takes a vary long time to establish global solutions
like, e.g., IMT-2000
3
Mobile Internet 2010
Design goals for wireless LANs
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–
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global, seamless operation
low power for battery use
no special permissions or licenses needed to use the LAN
robust transmission technology
simplified spontaneous cooperation at meetings
easy to use for everyone, simple management
protection of investment in wired networks
security (no one should be able to read my data), privacy (no
one should be able to collect user profiles), safety (low
radiation)
transparency concerning applications and higher layer
protocols, but also location awareness if necessary
4
7.2.1
Mobile Internet 2010
Comparison: infrared vs. radio transmission
Infrared
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Advantages
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IrDA (Infrared Data Association)
interface available everywhere
Mobile Internet 2010
experience from wireless
WAN and mobile phones
can be used
coverage of larger areas
possible (radio can
penetrate walls, furniture
etc.)
Disadvantages
–
–
typically using the license
free ISM band at 2.4 GHz
Advantages
Example
–
5
simple, cheap, available in many
mobile devices
no licenses needed
simple shielding possible
interference by sunlight, heat sources
etc.
many things shield or absorb IR light
low bandwidth
Radio
–
Disadvantages
–
uses IR diodes, diffuse light, multiple
reflections (walls, furniture etc.)
very limited license free
frequency bands
shielding more difficult,
interference with other
electrical devices
Example
–
WaveLAN, HIPERLAN,
Bluetooth
Internet & Mobile Communications
Wireless LANs
Characteristics
Wi-Fi Research
IEEE 802.11
Mobile Internet 2010
Introduction
PHY
MAC
Management
Wi-Fi Alliance and IEEE 802.11
Wifi Research
Andrew Miles - CISCO
Research shows 802.11 (aka Wi-Fi)
is becoming an essential part of our
everyday lives
–
Research in the US reveals some
factoids about the impact of Wi-Fi …
–
80% say Wi-Fi is more essential than
their iPod
81% would rather see their favourite
team lose than give up Wi-Fi for a week
90% would rather do without their daily
Starbucks than their Wi-Fi
… the bottom line is that Wi-Fi is
affecting real people in their everyday
lives
Source: WFA/Kelton Research,
July & October 2006
7
Mobile Internet 2010
Andrew Miles - CISCO
Wifi Research
Andrew Miles - CISCO
Wi-Fi has become popular
based on products that are
not optimised for wireless
use …
–
.. with apologies to all those
in the PC industry
8
Mobile Internet 2010
Not very usable while on
the move
Not really suitable for many
voice applications
Until recently, laptops were
mainly an enterprise style
product
Wifi Research
Andrew Miles - CISCO
200
Devices (million)
160
–
120
–
80
–
40
9
… and yet the Wi-Fi
market reached over 200
millions chipsets per year
in 2006
0
Source: In-Stat
2005
Mobile Internet 2010
2006
In 1997, the first IEEE
802.11 standard was ratified
In 2005, over 150 million
Wi-Fi devices were sold
In 2006, over 200 million
Wi-Fi devices were sold
(33% growth rate)
Enterprise APs
Home/SOHO
CE
Phones
PCs
Wifi research
Andrew Miles - CISCO
Wi-Fi is now being implemented in a wide
variety of more interesting devices …
Microsoft Zune
10
Sony mylo
Mobile Internet 2010
Nabaztag
Nikon Coolpix
Nokia N series
Sony PS3
… including lots of Wi-Fi & Wi-Fi/cellular
converged phone devices …
Andrew Miles - CISCO
11
Mobile Internet 2010
Wifi Research
Andrew Miles - CISCO
… with some of the new devices
actually used for voice (and not just
data) …
–
–
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Numerous Wi-Fi carrier voice and data deployments
are underway, and others expected during 2007 and
2008
Wi-Fi with UMA is the predominant voice approach
today, although SIP solutions also exist
Examples of voice deployments include:
12
Mobile Internet 2010
BT Fusion:voice & data in the home/office network at
more than 2,000 Openzone hotspots
Orange Unik for Professionals: provides Wi-Fi to GSM
handoff, and includes unlimited use for Wi-Fi calls
NTT DoCoMo: SIP-based voice for large enterprise
customers
Wi-Fi Research
Andrew Miles - CISCO
… based on access in many
locations outside the home
or office …
–
143k+ hot spots in 132 countries
–
500+ muni deployments in 29
countries
–
Source: JiWire (12 March 2007)
Other sources indicate 200k+ hot
spots
Source: Tropos & WFA
82% of US hotels offer Wi-Fi
Source: American Hotel & Lodging
Melbourne
Assn
13
Mobile Internet 2010
Wi-Fi Research
Andrew Miles - CISCO
700
Not far from 1B!
Devices (million)
600
500
400
CE
… which means the
promise of one billion
chipsets sold in a year
might not be far off!
–
Voice
–
300
–
200
100
14
0
2006
Mobile Internet 2010
2010
Both CE and Voice are forecast to
make a big impact by 2010
They will enable even more use of
Wi-Fi both in all market segments
One billion chipsets is forecast by
2012 Enterprise APs
Home/SOHO
CE
Phones
PCs
Internet & Mobile Communications
Wireless LANs
Characteristics
Wi-Fi Research
IEEE 802.11
Mobile Internet 2010
Introduction
PHY
MAC
Management
Wi-Fi Alliance and IEEE 802.11
Introduction IEEE 802.11
L'IEEE
(Institute of Electrical and
Electronics Engineers) has
normalised several categories of
local area networks
– Ethernet
(IEEE 802.3)
– Token Bus (IEEE 802.4)
– Token Ring (IEEE 802.5)
16
Mobile Internet 2010
Introduction IEEE 802.11
1990: launching of the project to create a
wireless LAN - WLAN (Wireless Local Area
Network)
–
Goals:
to offer a wireless connectivity to fixed workstations of
mobile workstations
to allow fast deployment inside a local area
To permit the use of different frequency bands
–
17
2001: publication of the first International standard
for wireless LAN developped by the IEEE
organisation.
Mobile Internet 2010
Introduction IEEE 802.11
Frequencies are chosen in the 2,4 GHz Band (as for
Bluetooth technology)
–
–
No need for licensing
Band in not completely free in many countries
Communications
–
Can be direct from terminal to terminal
–
It is then impossible to relay frames from one terminal to another
With an Access Point which relays all the traffic
Transmission rates vary depending on coding technics
which are used and of the bandwidth allocated.
18
Mobile Internet 2010
Introduction IEEE 802.11
Access Method to the physical layer (MAC
protocol - Medium Access Control)
–
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Quite complex
Many available options on the radio interface
Access Technics derived from CSMA/CD
Carrier Sense Multiple Access/Collision Detection, used to
define the access in wired networks
Problem: In wireless networks it is impossible to detect
collisions as for Ethernet LANs.
–
Introduction of a new protocol : CSMA/CA (Carrier Sense
Multiple Access/Collision Avoidance)
19
Mobile Internet 2010
IEEE 802.11
802.11 - Main Standard (june 1997)
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802.11x - Amendements
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20
Le groupe de travail concentre maintenant ses efforts pour produire
des standards pour des WLAN à grande vitesse
802.11b - speed up to 11 Mbits/s (ISM band)
802.11a - speed up to 54 Mbits/s (UN-II band)
802.11g - speed up to 54 Mbits/s (bande ISM)
802.11h – dynamic selection of frequencies and power control (UN-II
band)
802.11e - Quality of service
802.11f - Roaming
802.11i - security improvements
802.11n - MIMO
…
802.11v - goal : create an interface of the higher layer which allow to
manage wireless devices.
Mobile Internet 2010
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