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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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

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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

12

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