Post on 09-Feb-2022
IEEE 802.11 WLAN Standards for Wi-Fi Solutions
Today and TomorrowIEEE 802 Wireless Standards Educational Workshop
November 30, - December 1, 2007
Al PetrickVice-Chairman IEEE 802.11 WG
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Outline• IEEE 802.11 History• Current Projects• Industry Alliances• Highlights of Key Projects 802.11n, 802.11s• Questions
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IEEE 802 Organization
Standards Activities Board
IEEE Standards Association
802.3CSMA/CDEthernet
802.5Token
Passing Ring
802.11WirelessWLAN
802.15WirelessPersonal
Area Networks
802.20Mobile
BroadbandWirelessAccess
802.19Co-existence
TAG
SponsorIEEE 802
Local and Metropolitan Area Networks(LMSC)
Sponsor Sponsor Sponsor
802.17ResilientPacketRing
802.18Radio
RegulatoryTAG
802.16Broadband
WirelessBroadband
Access
802.21Media
IndependentHandoff
802.1HigherLayerLAN
Protocols
802.22WirelessRegional
AreaNetworksIEEE 802.11: ~500 Participants
Voting Members ~259www.ieee802.org/11
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History - Milestones• 1989: ISM frequency Bands 900MHz, 2.4GHz and 5GHz• 1990: IEEE 802 starts 802.11 project – extension 802.3• 1994: 1st wireless radios - Inventory control• 1997: IEEE 802.11 standard approved (2.4GHz – 1Mbps)• 1998: UNII (Unlicensed National Information Infrastructure)
Band - 5 GHz• 1999: IEEE 802.11 standard achieved ISO/IEC approval• 1999: IEEE 802.11a (5GHz – 54Mbps) - approved
IEEE 802.11b (2.4GHz- 11Mbps)- approved • 1999: Formation of WECA (now Wi-Fi Alliance)• 2001: IEEE 802.11d Regulatory Domains - approved• 2003: IEEE 802.11g (Higher rate 2.4GHz PHY) – approved
IEEE 802.11i (Security) - approvedIEEE 802.11h (Spectrum Mgmt) - approvedIEEE 802.11f (interaccess point protocol) – approved
• 2005: IEEE 802.11e (MAC enhancements – QoS) – approvedNovember 2007 - 106th Session!
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IEEE 802.11 Standard and Amendments
• Since 1990 the IEEE 802.11 working group has initiated 27 Projects (Task Groups)– IEEE Std 802.11, 802.11a, 802.11b, 802.11b-Cor1,
802.11d, 802.11e, 802.11F, 802.11g, 802.11h, 802.11i, 802.11j, 802.11k, 802.11m, 802.11ma, 802.11-REVma, 802.11mb, 802.11n, 802.11p, 802.11r, 802.11s, 802.11T, 802.11v, 802.11u, 802.11w, 802.11y, 802.11z, 802.11.1 and 802.11.2
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802.11 Current Projects
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IEEE 802.11 – Key Technical Attributes
• Specifications for the Physical and MAC Layers
• Backward compatibility with legacy 802.11 standard
• Maximize spectral efficiency and performance
• Co-existence with other device sharing the 2.4GHz and 5Ghz frequency bands
2 1154
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400
500
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802.11 802.11b 802.11a/g 802.11n
20/25 MHz40 MHz
802.11 Physical layerData Rates – Mbps
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Example 802.11 Radio Architecture
• 802.11 specifies physical and MAC layer parameters– PHY: Regulatory requirements, modulation, TX power, RxSense, PER, Timing
and Switching parameters– MAC: Protocol timing primitives, QoS, Security, and legacy control/management
paramters• IEEE 802.11 does NOT specify implementation, or physical interfaces
MAC
RF/MixedSignal
Transceiver(MODEM)
LNA
PA
AntSW
Filtering2.4GHz5.0GHz3.65GHz- 3.7GHz
Host Processor andDisplay Interface
Ethernet Controller
MAC ProcessorARM – VoiceMIPS - Video
BasebandProcessor
Physical Layer MAC Layer
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WI-Fi Alliance
– Founded in 1999 as WECA– Chartered to certified
multi-vendor WLAN equipment “interoperability” based on IEEE 802.11 standard and amendments
– Liaison representation from the Wi-Fi Alliance
– www.wifialliance.org
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Wi-Fi Forecast
0
100
200
300
400
500
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2006 2010
Dev
ices
(mill
io
Enterprise APsHome/SOHOCEPhonesPCsSource: In-Stat
– Both Consumer Electronics and Voice (VoIP) are forecast to make a huge impact by 2010
– They will enable even more use of Wi-Fi both in all market segments
– ~One billion chipsets is forecast by 2010
ConsumerElectronics
Voice
600M
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Wi-Fi 802.11n Certification
• Draft 802.11n• Started
– June 2007• Certifications
– Draft 802.11n based on D2.0– Handheld and Consumer Electronics
profile in 2008– Currently 82 products certified
based on 802.11n draft 2.0
• Observations– The market has demanded a
certification on baseline 11n as as 11n closes in on ratified
– New Look and Feel
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Wi-Fi Hotspot Public Access
– 143K+ hot spots in 132 countries• Source: JiWire (12 March 2007)• Other sources indicate 200k+ hot spots
– 500+ muni deployments in 29 countries
• Source: WFA
– 82% of US hotels offer Wi-Fi• Source: American Hotel & Lodging Assn
Melbourne
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IEEE 802.11n• Current approved draft is 2.0• IEEE 802.11 WG completed draft 3.0 in Oct 2007• Wi-Fi CERTIFIED products shipping today support draft 2.0• Standard is expected to be completed early 2009• Data rate: >100Mbps• Modulation: OFDM• Channel BW: 20Mhz / 40MHz • Support: WPA and WPA2 (AES) Security• Based on MIMO technology Based using Spatial multiplexing and coding
to achieve higher throughput• Operates in the existing 2.4GHz and 5GHz band and is backwards
compatible with 802.11g and 802.11b products
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Driving Applications for 802.11n• 802.11n WLAN systems are expected to be an
upgrade to existing 802.11g WLANs– Consumer electronics, Residential, SOHO, Hotspots,
Enterprise networks
• Application Drivers– DV Audio/video, SDTV, HDTV, DVD– Internet Streaming video/audio– VoIP, Video phone, Video Conf– Content download (photo camera)– Internet File transfer (email, web, chat)– Interactive Gaming
(((((
Media Server
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Higher Throughput Higher Frequencies Beyond 802.11n…..for tomorrow!!
• Very High Throughput (VHT) Study Group• Leveraging input from WFA liaison to define usage models
– Wireless docking– In Home Distribution of HDTV and other content– Rapid Upload and Download of large files to/from server– Backhaul Traffic (e.g. for Meshing, Enterprise, Small Office)
• Frequency band options: 5GHz, 50GHz, (275GHz – 3,000GHz)Terahertz?
– Terahertz spectrum…satellite and amateur radio services• Data rates => 1.5Gbps….for uncompressed streaming video
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IEEE 802.11 n
High ThroughputPHY Layer Highlights
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MIMO
• MIMO: multiple input (to the environment), multiple output (from the environment
• MIMO means has different meanings• A transmit beamforming antenna array
and/or multiple receive diversity antennas qualifies as MIMO by some
• These systems improve robustness and increase the rate at a given range, but they do not increase the maximum data rate
Tx Rx
hh
• Spatial division multiplexing (SDM): transmit independent data streams on different antennas
• The maximum data rate increases as a function of the number of transmit antennas
• The number of receive antennas is least the number of data streams with a linear equalizer
Tx Rx
hh
…
xN
x1… y1… …
yM
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802.11n - High Throughput
• 20 & 40 MHz channelization• 1 to 4 spatial streams
– 1 stream for Client (Mandatory)– 2 stream for Access Point (Mandatory)
• ½ GI• 56 tones (in 20MHz)• 5/6 coding• Green Field preamble
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Spectrum Allocation in US and Europe
• Existing 2.4Ghz World-Wide Spectrum• Existing 5GHz Spectrum
– UNII lower• Four 20MHz channels• 5.15-5.25 GHz
– UNII middle• Four 20MHz channels• 5.25-5.35 GHz
• ETSI bands– Ten 20MHz channels– 5.5-5.7GHz
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802.11n - 20MHz Channel Mask
• New 20MHz spectral mask• Same as IEEE 802.11a Mask• Modified signal floor at 30MHz
– From -40dBr to -45dBr
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802.11n - 40MHz Channel Mask
• 40MHz Spectral Mask– Adjacent channel interference performance is very similar between two
neighboring 40MHz devices as between two neighboring 20MHz devices• Adjacent channel interference between neighboring 20MHz and 40MHz
devices is yet to be determined• 40MHz channels best suited for 5GHz Frequency band
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802.11a PPDU Phy - Header
• Short training field (STF) start-of-packet detection, AGC setting, initial frequency offset estimation,time synchronization
• Long training field (LTF) used for accurate frequency offset estimation, time synchronization, and channel estimation
• Signal field (SIG) contains rate and length information– SIG has only one parity bit which leads to false detects– A reserve bit in the signal field has been used by some manufactures
for more parity• First 16 bits of the data field is the service field - contains reserve
bits and scrambler init. bits
Data FieldLong TrainingField
Short TrainingField
SignalField
ServiceField
8usec 8usec 4usec 16-bits
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Mixed Format High Throughput Preamble
• Mixed Format (MF) high throughput preamble starts with the legacy 11a preamble
• Followed by high throughput training fields
L-LTFL-STF L-SIG
HT-SIG2
HT-SIG1
HT-STF
HT-LTF1
HT-LTFN
HTData
LegacyPreamble
HTPreamble
ServiceField
HT – SIG8 µsec
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High Throughput Signal Field
• Mixed Format (MF) high throughput bit 7 of HT-SIG1 distinguishesbetween 20 vs 40MHz channels
Smoothing,LDPC, GI……CRC…TailLSB0……………………………MSB23
Modulation Code 20/40 BW (HT Length)LSB0 ………….6 MSB 7..(LSB8……… MSB23)
HT – SIG1 HT- SIG2HT – SIG 8 µsec
Bit 8,9 # of Spatial Stream
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Interoperable PPDU Format with 11a/g Legacy OFDM Devices
• Mixed Format (MF) preamble specified to provide PHY interoperability with legacy OFDM devices
• The beginning of the MM preamble consists of legacy (L) training identical to 11a– Contains L-STF, L-LTF, and L-SIG field as 11a such that legacy devices can detect the
preamble• How do we transmit the single stream legacy part of the MM preamble with a multiple
antenna device? – It is desirable to transmit the legacy training from all antennas for maximum power and range– However, this may cause unintentional and undesirable beamforming effects since we are
transmitting the same signal from each antenna• Cyclic shifts are applied to additional antennas to decorrelate transmission paths
– Legacy devices with cross correlation receivers are sensitive to delay spread, which will be exacerbated by long cyclic shifts
– Shorter shifts are used on the legacy training part of the MM preamble to conserve detection properties: maximum of 200nsec
– Cyclic shifts occur symbol by symbol basis
High throughput training fieldL-LTFL-STF L-SIG
8usec 8usec 4usec
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MCS Set One Spatial Stream
65.058.552.039.026.019.513.06.5
800ns GI
20MHz Data rate (Mbps)
72.265.057.843.328.921.714.47.2
400ns GI
150.0135.0120.090.060.045.030.015.0
400ns GI
135.0121.5108.081.054.040.527.013.5
800ns GI
40MHz Data rate (Mbps)
5/664-QAM7¾64-QAM62/364-QAM5¾16-QAM4½16-QAM3¾QPSK2½QPSK1½BPSK0
RModulationMCS Index
PHY bit rates
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Two Spatial Streams
• A two antenna device with optional 40MHz mode and R= ½ GI can achieve 300Mbps
130.0117.0104.078.052.039.026.013.0
800ns GI
20MHz Data rate (Mbps)
144.444130.000115.55686.66757.77843.33328.88914.444
400ns GI
300.0270.0240.0180.0120.090.060.030.0
400ns GI
270.0243.0216.0162.0108.081.054.027.0
800ns GI
40MHz Data rate (Mbps)
5/664-QAM15¾64-QAM142/364-QAM13¾16-QAM12½16-QAM11¾QPSK10½QPSK9½BPSK8
RModulationMCS Index
PHY bit rates
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Three Spatial Streams
195.0175.5156.0117.078.058.539.019.5
800ns GI
20MHz Data rate (Mbps)
216.7195.0173.3130.086.765.043.321.7
400ns GI
450.0405.0360.0270.0180.0135.090.045.0
400ns GI
405.0364.5324.0243.0162.0121.581.040.5
800ns GI
40MHz Data rate (Mbps)
5/664-QAM23¾64-QAM222/364-QAM21¾16-QAM20½16-QAM19¾QPSK18½QPSK17½BPSK16
RModulationMCS Index
PHY bit rates
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130Mbps Mode; Channel Model D
0.001
0.01
0.1
1
20 25 30 35 40SNR (dB)
PER
2x22x3
Improved Robustness with Receive Diversity
• 2x2 system, the required SNR may be beyond transmitter or receiver capability
• Additional receive antennas reduce required SNR
• Receive diversity enables signal reception of the peak two stream data rate at a feasible SNR
8 dB
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MIMO Performance Improvement with Receive Diversity
• Added robustness from receive diversity enables longer ranges at a given throughput
• At a given range, add robustness achieves higher throughputs
• MIMO increases peak data rates with additional data streams
• At lower data rates, MIMO systems may rate adapt to single stream modes, equivalent to 1x2 receive diversity, for added robustness and increased range
20MHz; Channel Model D
0
20
40
60
80
100
120
0 10 20 30 40 50 60 70Range (m)
Ove
r-th
e-ai
r Th
roug
hput
(Mbp
s)
legacy 1x111n 2x211n 2x3
Better Range
MoreThroughput
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Space-Time Block Coding (STBC)
y1x2
x1
(x1)*
-x2
y2
y3x4
x3
(x3)*
-x4
y4
• Space-time block coding combines signals over two OFDM symbols between multiple antennas for transmit diversity gain
• This provides gain equivalent to receiveddiversity
• STBC has a transmit power penalty with respect to receive diversity
• Configurations include 2x1, 3x2, 4x2, 4x3
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130Mbps Mode; Channel Model D
0.001
0.01
0.1
1
20 25 30 35 40SNR (dB)
PER
2x24x2
Improved Robustness with STBC Transmit Diversity
• Transmit diversity gain from STBC enables high data rates at a reasonable SNR received by a device with few receive antennas
• Benefits clients that are size and power constrained
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IEEE 802.11s
MESH
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Why Mesh?
• What’s so good about Mesh?– Enables rapid deployment with lower-cost backhaul– Easy to provide coverage in hard-to-wire areas– Self-healing, resilient, extensible– Under the right circumstances:
• Greater range due to multi-hop forwarding• Higher bandwidth due to shorter hops• Better battery life due to lower power transmission
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802.11s Project Scope• In brief, produce an amendment to the 802.11 standard to
create a Wireless Distribution System with automatic topology learning and dynamic wireless path configuration.
– Target number of packet forwarding nodes: ~32– Support unicast and broadcast/multicast traffic– Use 802.11i security or an extension thereof– Extensible routing to allow for alternative forwarding path
selection metrics and/or protocols– Use the 802.11 four-address frame format or an extension– Interface with higher layers and connect with other networks
using higher layer protocols• Current Draft 802.11s d1.07
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802.11s Project Scope (cont.)
No Redesign of Existing PHY(.11a/b/g/n)
802.11s is an amendment to the
802.11 MAC
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Classic 802.11 Wireless LAN
= radio link
BSS = Basic Service Set
AP
STASTA
STASTA
STA STA
STA
STA
Wired Infrastructure
ESS = Extended Service Set≈ SSID
AP
AP
AP
Wireless Paradox: WLAN Access Points are Typically Wired
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Unwire the WLAN with Mesh
MeshAP
STASTA
STASTA
STA STA
STA
STA
Wired Infrastructure
= mesh radiolink
ESS = Extended Service Set≈ SSID
MeshAPMesh
Point
MeshAP
MeshAP
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Example 802.11s Mesh Networking Deployment Scenarios
802.11s Expected to be Used Across Many Diverse Applications802.11s Expected to be Used Across Many Diverse Applications
Residential
Office Campus/Public Access
Public Safety/Military
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Device Classes in a WLAN Mesh Network
• Mesh Point (MP): establishes peer links with MP neighbors, full participant in WLAN Mesh services
– Light Weight MP participates only in 1-hop communication with immediate neighbors (routing=NULL)
• Mesh AP (MAP): functionality of a MP, collocated with AP which provides BSS services to support communication with STAs
• Mesh Portal (MPP): point at which MSDUs exit and enter a WLAN Mesh (relies on higher layer bridging functions)
• Station (STA): outside of the WLAN Mesh, connected via Mesh AP
PortalMP
STA
External Network
MPAP
MPAP
STA
MP
STA STA
Mesh PointMesh Portal
Mesh AP
Station
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802.11s MAC• Mandatory MAC Functions
– Enhanced Distributed Channel Access (EDCA)• Re-use of latest MAC enhancements from 802.11 (i.e. 802.11e)• Compatibility with legacy devices• Easy to implement, providing reasonable efficiency in simple
Mesh WLAN deployments• Optional MAC Enhancements
– Mesh Deterministic Access (MDA)• Reservation-based deterministic mechanism
– Common Channel Framework (CCF)• Multi-channel operation mechanism
– Intra-mesh Congestion Control– Power Management
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(Optional) Mesh Addressing
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Mesh Data Frame Format
Frame Control
Octets:2
Dur
2
Address 1
RA
6
Address 2
TA
6
Address 3
DA
6
Seq Control
2
Address 4
SA
6
Mesh Header
4~16 4
FCS
0-tbd
Mesh E2E Seq Number
2
Time To Live
1
Mesh Flags
Octets: 1
2
Qos Control
Payload
These fields are always present in mesh frames.
Bit 0: Address Extension (AE)
Bits 1-7: Reservedfor future use
Mesh Header
Address 5(6 octets)
Address 6(6 octets)
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6-Address Scheme
11s MAC Header(up to Mesh TTL field) Frame Body FCS
Address5
Address6
SADAMesh SAMesh DATARA111
N/PN/PSADATARA011
N/PN/PN/ADATA=SARA=BSSID001
N/PN/PN/ASATA=BSSIDRA=DA010
N/PN/P*N/ABSSIDTA=SARA=DA000
Address 6Address 5
Address 4Address 3Address 2Address 1AE Flag
From DS
To DS
* N/P = Not Present
When the AE flag = 0, all fields have their existing meaning, and there exist no “Address 5” and “Address 6” fields – this assures compatibility with existing hardware and/or firmware.
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• The ordering of the addresses should be from the innermost to the outermost “connections”– Address 1 & 2 for endpoints of a link between RX and TX– Address 3 & 4 for endpoints of a mesh path between a destination and a
source MP• Including MPPs and MAPs
– Address 5 & 6 for endpoints of an (end-to-end) 802 communication• A series of mesh paths connected at MPPs (e.g., TBR in HWMP) or• An 802 path between legacy STAs (including nodes outside the mesh) or• Any mixture of them (e.g., an MP to an STA or vice versa).
6-Address Scheme – Address Mapping Principle
802.11 STA MAP STAMP MPP
link link link link
mesh path
End-to-end 802 communication
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STA1
Example: 802.11 STA to External STA
STA3
Address 3
N/ASTA1MAP1
Address 4Address 2Address1
MAP1
STA3
Address 5*
MAP1
Address 4
MPP
Address 3
STA1MAP1MP2
Address 6*Address 2Address1
MP2
STA3
Address 5
MAP1
Address 4
MPP
Address 3
STA1MP2MPP
Address 6Address 2Address1
MPP
STA3
MPP**STA3SADA
* Intermediate MPs (here MP2) don’t have to process these fields.** Ethernet address of MPP’s interface to a wired network
Non-802.11 (i.e., Ethernet) frame
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Internet
Mesh AP Station
PortalMobile Station
Some Challenges in Mesh networks
• Support for path selection
• Mobility aware– Clients served– Network itself
(e.g. Military and Public Safety)
• Set of direct Neighbors
• Exposed & hidden nodes
= Set of indirect NeighborsInterference Awareness needed
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Summary• Wireless LAN Standards for the
Physical and MAC Layers• Backward compatibility
with legacy 802.11 standard and maintain Co-existence (good neighbor) in current spectrum
• Provide mechanisms to interface to networks outside 802.11
• Today 2007 – 802.11n –– 802.11s new infrastructure – Existing spectrum
• Tomorrow 2010 – New applications– Higher data rates >1Gbps– Protocol advancements– Expand into new frequencies, 50GHz
60GHz, and Terahertz
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802.11 Physical layerData Rates – Mbps
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Thank you !
Al PetrickVice-Chairman IEEE 802.11 WGJones-Petrick and Associates, LLCOrlando, Floridawww.jpasoc.comEmail: al@jpasoc.comPhone: +1.321.235.3269
IEEE 802.11 Handbook A Designer’s Companion
ISBN 0-7381-4449-5