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WLAN IEEE 802.11acIntroduction

Coen van Bergen

Evolution of WLAN 802.11 standards Technologies OFDM, SDMA, MIMO, MU-MIMO Facts about WLAN IEEE 802.11ac Test Solutions for WLAN 802.11ac

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Evolution of WLAN 802.11 Standards

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802.11 WLAN Evolution

under developmentOct. 2009June 2003Sep. 1999Sep. 1999Release

500 Mbps 37.2 to 150 Mbps 26 to 54 Mbps1 to 11 Mbps6 to 54 MbpsData rate 1

SDMA (OFDM)OFDMOFDM, DSSSFDMA, DS-CDMAOFDMAccess method

BPSK, QPSK,16 / 64 / 256 QAM

BPSK, QPSK,16 / 64QAM

DBPSK, DQPSK,DBPSK, DQPSK,BPSK, QPSK

BPSK, QPSK,16 / 64QAMModulation

BCC, LDPC, STBCConvolutionalCoding, LDPC

CCK, PBCC11 chip Barkersequence, CCK,PBCC

Forward errorcorrection coding(convolutional;code rates 1/2, 2/3,3/4)

Coding

4 x 4

20 / 40 MHz

2.4 GHz ISM band,

5 GHz U-NII bands

802.11n

8 x 8111MIMO stream

20 / 40 / 80 / 160 MHz20 MHz20 MHz20 MHzBandwidth

5 GHz U-NII bands

2.4 GHz ISM band2.4 GHz ISM band

5 GHz U-NII bandsCarrier freq.

802.11ac802.11g802.11b802.11a

1 The maximum data rate can be achieved by higher order modulation2 In case of 4 streams the maximum data rate is 600 Mbps3 For 160 MHz and 8 streams theoretically 6.93 Gbps

802.11ac = Backwards compatible with 802.11a and n

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Technologies:

OFD! "DA! IO! #$IO

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Facts about WLAN 802.11ac OFDM

l 802.11ac PHY is based on the well known OFDM (OrthogonalFrequency Division Multiplexing) PHY used for 802.11a and 802.11n

f

duration TS 1/TS

f0 f2f1

fCarrier= f0+n/TS where n is an integer, f = 1/TS , therefore: fn = n x f

The maximum of one carrier is at the zero crossings of all others

f2

f1

f0

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MMO Multi!l" n!ut Multi!l" Out!ut

Throughput:

Data 1

Coding Fading on the air interface

Data 2

100%200%

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M#$MMO % Multi#s"r MMO

SDMA = Spatial Division Multiple Access = Access Method

- Downstream only- Max. 8 Streams- Max 4 Users

- Max 4x4 antennes per user

Beamforming ?

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Facts a%out WLAN IEEE 802.11ac

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Facts about WLAN 802.11ac OFDM

l OFDM Subcarriers

l Subcarrier Rotationreduces Peak to

Average Power Ratio

PAPR

-122 to -2 and 2 to 122, 16 Pilots256 per 80MHz Chan80+80

-250 to-130, -126 to -6,

6 to 126 and 130 to 250, 16 Pilots

512160

-122 to -2 and 2 to 122, 8 Pilots25680

-58 to -2 and 2 to 58, 6 Pilots12840

-28 to -1 and 1 to 28, 4 Pilots6420

Subcarriers Transmitting SignalNumber of SubcarriersBandwidth (MHz)

Same as 80MHzSame as 80 MHz80+80

180 degrees (-1)-192 to -1 and 64160

180 degrees (-1)-6480

90 degrees (j)040

N/A20

Rotation ValueRotated SubcarriersBandwidth

(MHz)

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Facts about WLAN 802.11ac &'ann"li(ation

l Support of 20, 40, 80 MHz, 160 MHz channel bandwidth

l The 80MHz channel will consist of two adjacent, non-overlapping40MHz channels.

l The 160MHz channels will be formed by two 80MHz channelsl adjacent (contiguous)

l non-contiguous

l Europe, Japan and Global Operating Class Channel Allocation

140

136

132

128

124

120

116

112

108

104

100

64

60

56

52

48

44

40

36IEEE channel #

20 MHz

40 MHz

80 MHz

5170

MHz

5330

MHz

5490

MHz

5710

MHz

160 MHz

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Facts about WLAN 802.11ac Fra)" For)at

l All 802.11 devices (L= Legacy) to synchronize to the signal

l L-STF (Short Training Field)

l L-LTF (Long Training Field)l L-SIG (Signal).

l New for 802.11ac: VHT (Very High Throughput.)

l VHT-SIG-A field contains two OFDM symbols (BPSK, 90 rotated BPSK)

l

VHT-STFl VHT-LTFs..

l The VHT-SIG-B is the last field in the preamble

VHT auto-detection

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XLow Density Parity Check (LDPC)

XSpace Time Block Coding (STBC)

X400 ns short guard interval

XMulti-User MIMO (MU-MIMO)

X2 to 8 spatial streams

X80+80 MHz, 160 MHz channels

X256QAM

XBPSK, QPSK, 16QAM, 64QAM

X1 spatial stream

X20 MHz, 40 MHz, 80 MHz channels

OptionalMandatoryProperties

Peak Data Rate ~293 Mbps ~3.5 Gbps

Facts about WLAN 802.11ac Optional/Mandatory

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Facts about WLAN 802.11ac

&alculation of Data *at"

l Mandatory

l 242 carrier 8 pilot carriers = 234 carriers

l Sample Frequency 80 MHz

l Guard Interval 800 ns

l

FFT 256l MCS7, 64 QAM (6 bits), Coding 5/6

l Symbol time: 256/80 MHz + 800 ns = 4 s

l Number of bits 6 x 234 x 5/6 = 1170 bits/symbol

l Maximum data rate: 1170 bits/symbol / 4 s /symbol =l 292.5 Mbit/s

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Facts about WLAN 802.11acOv"rvi"+ of datarat"s d"!"ndin, on M&S

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Facts about WLAN 802.11ac Mar-"t i"+

l First wave of chips will support:

l 80 MHz bandwidth

l

256 QAM support expectedl MIMO support plans vary for customers

Some start with 2x2, some plan 3x3 initially

l Some plan MU-MIMO initially with 2 streams for 2 users

l Next wave will support 160 MHz

l Planned for mid to end of this year

l Some indicating plans for 4x4 MIMO

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&'" Test "olutions WLAN IEEE 802.11ac

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Max. bandwidth 80 MHz

Max. bandwidth 160 MHz

R&S SMU

R&S SMBV

R&S FSQ

R&S FSW

/"st Solutions for 80M( and 10 M(

R&S SMU

R&S SMBV

R&S FSW +R&S FSW-B160

R&S AFQ100A/B

+

R&S SGS

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l Spectral Mask for 20, 40, 80 and 160 MHz Channels

WLAN 802.11ac Analsis +it' *3S FSWTransmiter Specifications Spectrum Measurements with R&S FSW

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l Transmitter Constellation Error

-325/6256-QAM9

-303/4256-QAM8

-275/664-QAM7

-253/464-QAM6

-222/364-QAM5

-193/416-QAM4-161/216-QAM3

-133/4QPSK2

-101/2QPSK1

-51/2BPSK0

RCE (dB)Coding RateModulationMCS

For error < 1dB a residual EVMof < -38 dB for T&M is needed

WLAN 802.11ac Analsis +it' *3S FSWModulation Analysis

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WLAN 802.11ac Analsis +it' *3S FSWModulation Analysis R&S FSW-!"/!"ac

Bandwidth 160 MHz

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WLAN 802.11ac Analsis +it' *3S FSWModulation Analysis R&S FSW-!"/!"ac

Constellation diagram R&S FSW-K91acResidual EVM < -45 dB at 5 GHz

DUT EVM: -33 dBWith -45 dB res. EVM, the result is -32.7 dB

R&S FSW quality is needed, becausewith e.g. -35 dB res. EVM, the result is -30.9 dB,which does not meet the spec.

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WLAN 802.11ac Analsis +it' *3S FSW

M#MO Analysis

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nfor)ation about 802.11ac

l R&S Technology paper 1MA192

l Wikipedia -> http://en.wikipedia.org/wiki/IEEE_802.11ac