Download Interoperability Standards

Wireless LANs
802.11
Presentation Material
• Overview of 802.11
– Overview
– Key amendments
• 802.11n
– PHY
– MAC
– Performance
• Important upcoming amendments
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802.11p
802.11r
802.11s
802.11y
Overview of 802.11
802.11 PHY Standards
http://grouper.ieee.org/groups/802/11/
In progress
Approved
External
802.11 MAC Standards
http://grouper.ieee.org/groups/802/11/
In progress
Approved
External
WiFi Alliance
•
Industrial consortium that promotes
802.11
Millions of WiFi Chipset Shipped
– www.wi-fi.org
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Certifies interoperability between
vendors’ products
Certifies consistency with standards
Fills in the gap when 802.11 standards
process is too slow (draft n)
WiFi success owes significant debt to
WiFi Alliance
Line between 802.11 standards
community and WiFi Alliance has
gotten very blurry
Certifications
– 802.11a/b/g/n
WiFi
– 802.11e Wireless Multimedia
– Draft 2.0 n
Wi-Fi Alliance, Introducing Wi-Fi Protected Setup™, January 3, 2007
802.11 Terminology
• Basic Service Set (BSS):
– A set of stations controlled by a
single “Coordination Function” (=the
logical function that determines
when a station can transmit or
receive)
• Independent Basic Service Set
(IBSS):
BSS
http://wireless.ictp.trieste.it/school_2002/lectures/ermanno/802.11_
Architecture.ppt
– A Basic Service Set (BSS) which
forms a self-contained network in
which no access to a Distribution
System is available
IBSS
• Extended Service Set (ESS):
– A set of one or more Basic Service
Sets interconnected by a
Distribution System (DS)
• Many different deployment
scenarios, want common MAC
BSS
Di
st
Sy ribu
st tio
em n
BSS
Distributed Coordination Function
(DCF)
• Intended to combat “hidden
nodes” in an uncoordinated
network and generate fair
access to channel
• Basic components:
–After waiting DIFS after last
detected transmission, source
sends Request to Send (RTS)
–Destination replies with Clear to
Send (if OK)
–Data is then transferred and
ACKed
–If an error occurs (e.g., collision),
then station has to wait for DIFS +
random backoff.
• Random backoff grows with # of
collisions
• Network allocation vector
– Acts as virtual carrier sense
– Duration given in RTS/CTS
fields
• DIFS = DCF Interframe Space
• SIFS = Short Interframe Space
Point Coordination Function (PCF)
• Intended to provide service
more appropriate for real-time
applications
– Not widely utilized initially
• Basic steps
– Access node (AN) implementing
PCF “wins” the channel by
cheating (SIFS < PIFS < DIFS)
– AN announces contention free
period in Beacon (realized in NAV)
to lock out DCF
– Polls each client in its polling list
• Frames separated by PIFS
• If client fails to respond within
PIFS, AN moves onto next
– At end of contention-free period a
contention free message is sent
ending the contention free period
– DCF holds until AN initiates
another contention free period
• Various ratios permitted between
contention based and contention
free
802.11 overhead
• Significant overhead involved
in 802.11
– RTS/CTS/ACK SIFS
– TCP, IP, MAC framing
– Real throughput is rarely come
close to PHY raw rate
http://www.cs.tut.fi/kurssit/TLT-6556/Slides/Lecture4.pdf
wireless.ictp.trieste.it/school_2002/lectures/ermanno/System_Performance.ppt
802.11 Alphabet Soup
Jun 1997
Sep 1999
Sep 1999
Oct 2001
Jun 2003
Jun 2003
Oct 2003
Jun 2004
Oct 2004
Sep 2005
Dec 2007
Mar 2008
Mar 2008
Sep 2008
Jan 2009
Feb 2009
Mar 2009
Aug 2009
Aug 2009
Sep 2009
802.11
802.11a
802.11b
802.11d
802.11f
802.11g
802.11h
802.11i
802.11j
802.11e
802.11k
802.11r
802.11y
802.11n
802.11u
802.11w
802.11p
802.11s
802.11.2
802.11v
2 Mbps ISM
54 Mbps UNII
11 Mbps ISM
global roaming
interoperability
54 Mbps ISM
spectrum management
security
Japanese spectrum
real time QoS
RRM measurements
fast roaming
US 3.65 GHz
100 Mbps
external networks
packet security
vehicular (5.9)
mesh networks
test recommendations
network management
Past dates are standards approval
dates.
Future dates from 802.11 working
group timelines
Letters are working group (WG)
designations.
Letters assigned alphabetically as
groups created.
No WG/ WG document
802.11c MAC Bridging
work incorporated into 802.1d
802.11l “typologically unsound”
802.11m doc maintenance
802.11o “typologically unsound”
802.11q too close to 802.1q
802.11x generic 802.11 standard
802.11t (test) will produce 802.11.2
http://grouper.ieee.org/groups/802/11/Reports/802.11_Timelines.htm
802.11 a/b/g
• Common MAC
– RTS/CTS scheme to handle hidden nodes
– Random backoffs to handle collisions
802.11b PHY
2.4 GHz (ISM)
14 overlapping channels
802.11g PHY
2.4 GHz (ISM)
14 overlapping channels
802.11a
5 GHz (UNII)
23 orthogonal channels
802.11e (Sept 2005)
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Enhances QoS for Voice over Wireless IP (aka Voice
over WiFi ) and streaming multimedia
Changes changes
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Enhanced Distributed Coordination Function (EDCF)
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Hybrid Coordination Function
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Shorter random backoffs for higher priority traffic
Defines traffic classes
In contention free periods, access point controls medium access
Stations report to access info on queue size.
Schedules as it sees fit
WMM (WiFi MultiMedia)
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WiFi Alliance profile of 802.11e
Available Sept 2004 (Cisco, IBM, Netgear, Atheros)
Handoff problems (to be addressed by 802.11r?)
Spectralink moving away from proprietary voice over WiFi
implementation
802.11j and spectrum (Oct
2004)
• Opens up
Japanese spectrum
for 5 GHz operation
– New Logic Support
Jan 05
• US 5.47 – 5.725
GHz released in
Nov 2003
• Alternate
bandwidths
2.4 GHz
Lower Upper
U.S.
2.402 2.48
Europe 2.402 2.48
Japan
2.473 2.495
Spain
2.447 2.473
France 2.448 2.482
5 GHz
US
UNII Low 5.15 – 5.25 (4) 50 mW
UNII Middle 5.25 – 5.35 (4) 250 mW
UNII Upper 5.725-5.825 (4) 1 W
5.47 – 5.725 GHz released in Nov 2003
Europe
5.15-5.35 200 mW
5.47-5.725 1 W
Japan
4.9-5.091
5.15-5.25 (10 mW/MHz) unlicensed
802.11h (Oct 2003)
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Make 802.11h act like
Hiperlan2
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Avoid radars in 5 GHz
band
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Avoid radars
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Listens and discontinues
use of a channel if a
radar is present
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Interference reduction
Range control
Power consumption
Savings
Bounded by local
regulatory conditions
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http://cisco.com/en/US/netsol/
ns340/ns394/ns348/netqa090
0aecd802570a1.html
New Logic (IP company) has
chips
Uniform channel utilization
Transmit Power Control
(TPC)
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Mandated in Europe beginning
2005
Cisco support in 1Q 05
(claimed March 05)
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Dynamic Frequency
Selection (DFS)
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http://www.newlogic.com/pres
s_room/press_releases/20050
120083419.shtml
Probably killed off HiperLAN/2
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PHY similar to 802.11a
MAC like ATM
Phillips decided to not make
any HiperLAN/2 chips
http://www.eetuk.com/bus/ne
ws/st/showArticle.jhtml?article
ID=16503607
Security
• Original WEP security was
flawed
• Fixed by 802.11i which
– Defined secure (but slow)
handoff procedures
– Added AES for encryption
– CCMP
• WPA - WiFi Protected Access
– WiFi Alliance “brand”
(http://www.wi-fi.org)
• TKIP
• 802.1x
– Products began Spring 2003
• WPA-2
– WiFi Alliance “brand”
– Implements 802.11i
– Products beginning Sept 2004
• WiFi Certified EAPs (for
WPA, WPA2)
– EAP-TLS (previously
tested)
– EAP-TTLS/MSCHAPv2
– PEAPv0/EAP-MSCHAPv2
– PEAPv1/EAP-GTC
– EAP-SIM
– All non-proprietary EAPs
(e.g., no LEAP -Cisco)
WLAN Summary
• Wildly successful because of ease of
deployment, price
• Moving to OFDM/MIMO (802.11n)
• Moving into additional bands (802.11y, 802.11j)
• New applications (802.11e)
• Extending capabilities with numerous PHY and
MAC amendments
• Building interoperability with other standards
(802.11u, 802.21)