Introduction to 802.11ac WLAN Technology and Testing · including 256QAM - BCC and LDPC coding, STBC - 1-8 spatial streams, up to 8 Tx antennas - Single-user and multi-user MIMO

© 2012 Agilent Technologies

Wireless Communications

Greater insight. Greater confidence. Accelerate next-generation wireless.

Introduction to 802.11ac WLAN Technology and Testing

Presented by: Mirin Lew, Agilent Technologies



Agenda

• WLAN Market Update

• IEEE 802.11 Standards Evolution

• Overview of 802.11ac

– Performance Goals and Timeline

– Review of 802.11n

– New Enhancements for 802.11ac

• Design and Test Challenges

• Transmitter Tests

• Receiver Tests

• Summary of Measurement Solutions

2



WLAN Market Update

WLAN retail and enterprise market growth rate for 2010 estimated at 12%

(IDC) to 23% (Infonetics). For first 3 quarters of 2011, IDC estimated

quarterly growth rates of 16% to > 20% year-over-year.

Growth drivers:

• Integration of WLAN into more consumer products: smartphones,

digital cameras, e-readers, media players, gaming consoles, Blu-ray

players, HDTVs

• Increasing adoption and use of WLAN in companies, small

office/home office, hospitals, etc. Enterprise market growing faster

than retail market.

• Use of WLAN to offload data from cellular networks

• New applications: health/fitness, medical, smart meters, home

automation

Multi-format chipsets are increasingly common, mostly WLAN + Bluetooth or

WLAN + Bluetooth + FM today, some include cellular, WiMAX, and/or GPS:

need to test multiple technologies/formats and avoid interference

3



New Applications for WLAN

Growth of high-definition video and desire for wireless connections is

driving need for higher data rates for applications such as:

• Wireless display

• Distribution of video/media content throughout the home or office

• Rapid file upload/download (sync devices, movie kiosks)

Example data rates:

4

Application Data Rate (Mbps)

Interactive videoconferencing 0.38 to 0.5

Internet video streaming 2.5 to 8

HDTV 19.4 to 25

Blu-Ray 40

Uncompressed video, “good” quality

(8-bits/color, 1920x1080p, 24 fps, 4:2:2)

796

Uncompressed video, “best” quality

(10-bits/color, 1920x1080p, 60 fps, 4:4:4)

3730



IEEE 802.11 Standards Evolution

5

WLAN

802.11-1997

2 Mbps, DSSS, FHSS

802.11b11 Mbps, CCK, DSSS

802.11a54 Mbps,

OFDM, 5 GHz

802.11g54 Mbps,

OFDM, 2.4 GHz

802.11n600 Mbps with

4x4 MIMO, 20/40 MHz BW,

2.4 or 5 GHz

802.11ac

802.11ad

802.11p27 Mbps, 10 MHz

BW, 5.8 GHz

802.11af

TVWS

Wireless Gigabit (WiGig)

Very High Throughput, 60 GHz

Very High Throughput, <6 GHz

TV WhiteSpaces

Wireless Access for Vehicular Environment (WAVE/DSRC)

DSRC = Dedicated Short-Range Communications



Introduction to 802.11ac Standard:

Enhancements for Very High Throughput (VHT)

• Standard under development by IEEE 802.11ac Task Group (TGac)

- Draft 1.4 released in November 2011

- Standard completion planned for Dec. 2013

• Minimum “very high throughput” goal of 1 Gbps

• Wi-Fi Alliance task group defining market requirements for 802.11ac. Expects

certification to launch by late 2012, prior to standard being finalized

• ABI Research (Sept. 2011):

- 802.11ac shipments will begin in 2012, becoming dominant Wi-Fi protocol by

2014

- Most products will be 802.11n/802.11ac dual-band chipsets

- 1x1 802.11ac chipsets will remain dominant until 2015 when they will be

surpassed by 2x2 and 3x3 chipsets

• In-Stat (Jan. 2012): Expect nearly 500 million 802.11ac devices by 2015, including

184 million notebooks and 165 million smartphones

• 802.11ac products announced by Quantenna, Broadcom, Redpine, Trendnet.

Broadcom is marketing 802.11ac as “5G WiFi” (www.5gwifi.org).

6



Review of 802.11n: Basis for 802.11ac

7

Feature Mandatory Optional

Transmission method OFDM

Channel bandwidth 20 MHz 40 MHz

FFT size 64 128

Data subcarriers / pilots 52 / 4 108 / 6

Subcarrier spacing 312.5 kHz

OFDM symbol duration 4 s (800 ns guard interval) 3.6 s (with 400 ns short guardinterval)

Modulation types BPSK, QPSK, 16QAM, 64QAM

Forward error correction Binary convolutional coding (BCC) Low density parity check (LDPC)

Coding rates 1/2, 2/3, 3/4, 5/6

MCS supported 0 to 7, 0 to 15 for access points 8 to 76, 16 to 76 for APs

Spatial streams and MIMO 1, 2 for access points direct mapping

3 or 4 streamsTx beamforming, STBC

Operating mode / PPDU format

Legacy/non-HT (802.11a/b/g)Mixed/HT-mixed (802.11a/b/g/n)

Greenfield/HT-Greenfield (802.11n only)



Changes and Enhancements for 802.11ac

• Wider channels

• Higher-order modulation

• More spatial streams and antennas (up to 8)

• Multi-user MIMO

•

8

Feature Mandatory Optional

Channel bandwidth 20 MHz, 40 MHz, 80 MHz 160 MHz, 80+80 MHz

FFT size 64, 128, 256 512

Data subcarriers / pilots 52 / 4, 108 / 6, 234 / 8 468 / 16

Modulation types BPSK, QPSK, 16QAM, 64QAM 256QAM

MCS supported 0 to 7 8 and 9

Spatial streams and MIMO 1 2 to 8Tx beamforming, STBC

Multi-user MIMO (MU-MIMO)

Operating mode / PPDU format Very high throughput / VHT

Data rates: 1.56 Gbps (80 MHz, 4 Tx, MCS9) “reasonable” case

6.93 Gbps (160 MHz, 8 Tx, MCS9, short GI) best case



802.11ac Channelization

• Operates in 5-6 GHz band only, not in 2.4 GHz band

• Mandatory support for 20, 40, and 80 MHz channels

• 40 MHz same as 802.11n. 80 MHz has more than 2x data subcarriers: 80 MHz has 234

data subcarriers + 8 pilots vs. 108 data subcarriers + 6 pilots for 40 MHz

• Optional support for contiguous 160 MHz and non-contiguous 80+80 MHz transmission and

reception. 160 MHz tone allocation is the same as two 80 MHz channels.

• U.S. region frequency allocation (shown below) includes 5710-5835 MHz channels not

available elsewhere. (Need to avoid weather radars in some areas)

These frequencies

are not available in

Europe, Japan and

other regions

Adapted from Specification Framework, IEEE 802.11-09/0992r15,

Updated based on 802.11ac/D1.0

245 MHz

Page 9



802.11ac VHT PPDU Format: New VHT Preamble

• L-STF, L-LTF, and L-SIG:• Similar to same fields in 802.11a/b/g (clause 17 in 802.11 standard)

• Transmitted first for backwards compatibility

• Fields are duplicated over each 20 MHz sub-band with appropriate phase rotation (see 22.3.7 in

standard). Subcarriers are rotated by 90 or 180 degrees in certain sub-bands to reduce PAPR.

• Cyclic shift delay applied to each transmit chain when applicable

• VHT-SIG-A

• 1st symbol of VHT-SIG-A is BPSK, while 2nd symbol is BPSK with 90 degrees rotation (QBPSK) to

enable auto-detection of VHT

• Contains info required to interpret VHT packets (BW, number of streams, STBC used, guard interval,

BCC or LDPC coding, MCS, beamforming)

L-STF L-LTF L-SIG VHT-SIG-A VHT-STF VHT-LTFs VHT Data

2 symbols 2 symbols 1 sym BPSK,

1 sym QBPSK1 symbol,

BPSK1 symbol 1 symb/LTF,

8 LTFs max

VHT-SIG-B

1 symbol

802.11acVHT PPDU

L-STF L-LTF L-SIG HT-SIG HT-STF HT-LTFs HT Data

2 symbols 2 symbols 2 symbols,

QBPSK

1 symbol,

BPSK1 symbol 1 symbol/LTF,

4 LTFs max

802.11nPPDU

(Mixed Mode)1 symbol = 4 s

“PPDU” = PLCP Protocol Data Unit

“PLCP” = Physical Layer Convergence Procedure

Page 10

October 2011



802.11ac VHT PPDU Format: New VHT Preamble

• VHT Short Training Fields (VHT-STF): – Used to improve automatic gain control estimation in MIMO transmission

• VHT Long Training Fields (VHT-LTF)– Long training fields: may include 1, 2, 4, 6, or 8 VHT-LTFs.

– Mapping matrix for 1, 2, or 4 VHT-LTFs (same as in 802.11n) or 6 or 8 VHT-LTFs (added for

802.11ac).

• VHT-SIG-B: – Describes length of data and MCS for multi-user mode. Bits are repeated for each 20 MHz sub-

band.

L-STF L-LTF L-SIG VHT-SIG-A VHT-STF VHT-LTFs VHT Data

2 symbols 2 symbols 1 sym BPSK,

1 sym QBPSK1 symbol,

BPSK1 symbol 1 symb/LTF,

8 LTFs max

VHT-SIG-B

1 symbol

802.11acVHT PPDU

L-STF L-LTF L-SIG HT-SIG HT-STF HT-LTFs HT Data

2 symbols 2 symbols 2 symbols,

QBPSK

1 symbol,

BPSK1 symbol 1 symbol/LTF,

4 LTFs max

802.11nPPDU

(Mixed Mode)1 symbol = 4 s

Page 11

October 2011



Diversity

Improve robustness

Spatial Expansion

(Transmit Diversity)

Receive Diversity

Multiple Antenna Techniques in 802.11ac

Space-time block

coding (STBC)

X1, X2

-X2, X1*

y1, y2

Spatial division multiplexing

(direct mapping)Multi-user MIMO

Transmit Beamforming

Spatial multiplexing

Improve user throughput

Multi-userIncrease system

efficiency

MIMO

MIMO (4x2)

Matrix

4 streams, 3 usersX1

X2

y1

y2

Downlink only

Up to 4 users

Up to 4 streams/user

Total 8 streams max



Transmitter Block Diagram, Single User

1 to 8 outputs BCC or LDPC

used, not both

1 to 8 inputs

From Figure 22-6, IEEE P802.11ac/D1.4

PH

Y P

ad

din

g

Scra

mb

ler

En

co

der

Pars

er

FE

C E

nco

der

FE

C E

nco

der

Str

eam

Pars

er

BCC

Interleaver

BCC

Interleaver

BCC

Interleaver

Constellation

mapper

Constellation

mapper

Constellation

mapper

LDPC

tone

mapper

LDPC

tone

mapper

LDPC

tone

mapper

Sp

ace t

ime b

lock c

od

ing

(S

TB

C)

CSD

CSD

Sp

ati

al M

ap

pin

g

IDFT

IDFT

IDFT

Insert GI

and

Window

Insert GI

and

Window

Insert GI

and

Window

Analog

and RF

Analog

and RF

Analog

and RF

. . .

. . .

. . .

. . .

. . .

. . .

. . .



Transmitter Block Diagram, Multi-User MIMO

1 to 8 inputs

Str

eam

Pars

er

BCC

Interleaver

Constellation

mapper

Constellation

mapper

Constellation

mapper

LDPC

tone

mapper

LDPC

tone

mapper

ST

BC

CSD

CSD

Sp

ati

al M

ap

pin

g IDFT

IDFT

IDFT

Insert GI

and

Window

Insert GI

and

Window

Insert GI

and

Window

Analog

and RF

Analog

and RF

Analog

and RF

. .

. . .

.

. . .

. . .

. . .P

HY

Pad

din

g

Scra

mb

ler

En

co

der

Pars

er

BC

C

En

co

der

BC

C

En

co

der

BCC

Interleaver

Constellation

mapperCSD

PH

Y P

ad

din

g

Scra

mb

ler

LD

PC

En

co

der

Str

eam

Pars

er

ST

BC

. .

. . .

. . .

.

User 1 (Using LDPC)

User N (Using BCC)

. .

.

1 to 4 users,

Up to 4 streams per user

Maximum 8 streams totalFrom Figure 22-7, IEEE P802.11ac/D1.4



Design Challenges: 256QAM Modulation

256QAM requires better error vector magnitude (EVM) performance

Transmitter relative constellation error (EVM) spec for 256QAM is -32 dB

vs. -28 dB for 64QAM

Achieving better EVM requires better linearity and phase noise

Errors may be due to imperfections in IQ modulator, phase noise or error

in LO, or amplifier nonlinearity

Some phase noise can be removed by phase tracking in receiver, but

phase changes faster than a symbol period will not be tracked: will

impact EVM

Agilent design tools:

• SystemVue W1917 WLAN Baseband Verification Library can

simulate effects of various errors to assist in optimizing design

• 89600 VSA software can help identify causes of EVM



Simulate Errors and Optimize System Design with

SystemVue W1917 WLAN Baseband Verification Library

16

• 2011.10 version includes signal processing blocks and

802.11ac reference designs for transmitter and receiver

• Allows early system architecture simulation and analysis,

algorithm development, or troubleshooting

• Go from design to test: generate I/Q waveform files for

download to signal generator, or analyze signals using

89600 VSA software

• Supported features:

- All channel bandwidths, modulation types and MCS

including 256QAM

- BCC and LDPC coding, STBC

- 1-8 spatial streams, up to 8 Tx antennas

- Single-user and multi-user MIMO

- Spatial mapping: direct mapping, spatial expansion, or

user defined

- WLAN TGac channel model

- Receiver supports timing and frequency sync, channel

estimation and phase tracking, demapping and decoding



• Option BHJ 802.11ac

Modulation Analysis supports

all bandwidths and modulation

types, up to 4x4 MIMO

• 89600 VSA software provides

flexible display for optimal

viewing of MIMO results:

– Up to 20 simultaneous traces

and up to 20 markers per

trace

– Arbitrary arrangement and

size of windows

• Supports variety of hardware

configurations for the

performance, bandwidth, and

number of channels you need

802.11ac Signal Analysis with 89600 VSA

17

EVM vs. Symbol

EVM vs.

Subcarrier

Metrics per STSChannel Matrix

Channel Frequency

Response



Example: Troubleshooting EVM with 89600 VSA

“V” shape of EVM vs.

carrier indicates

problem with IQ

timing skew

EVM improved from

-44.4 dB to -49.7 dB

after IQ skew

adjustment

OFDM Error

Summary display

shows IQ offset,

quadrature error,

gain imbalance, and

timing skew



Improving PA Linearity with Digital Predistortion

SystemVue W1716 DPD Builder

simplifies and automates digital

predistortion (DPD) design for power

amplifiers

DPD requires 3-5 times the signal BW

of the PA under test: need wideband

signal generation and analysis

1. Stimulus waveform downloaded to

wideband AWG, upconvert to RF

with MXG or ESG signal generator

2. PA’s response captured using

M9392A and 89600 VSA software

3. W1716 compares PA’s response vs.

desired signal and creates DPD

model

4. W1716 creates waveform with DPD

and downloads to AWG. PA

response measured to verify DPD.

Green = original signal

Blue = PA without DPD

Red = PA with DPD



Test Challenge:

Generating Wider Bandwidth Signals

802.11ac Waveform Creation Software

• SystemVue W1917 WLAN Baseband Verification Library

– 2011.10 release includes 802.11ac reference designs for transmitter and

receiver

– Supports BCC and LDPC coding, all channel bandwidths and MCS, SU-

MIMO and MU-MIMO with up to 8 spatial streams, channel model

• N7617B Signal Studio for WLAN

– Basic option for component test, advanced option for receiver test

– Supports BCC and LDPC coding, all MCS, up to 4 spatial streams, and SU-

MIMO or MU-MIMO

– Create 20, 40, and 80 MHz BW signals with N5182A MXG, E4438C ESG,

E8267D PSG, and N5106A PXB

– Create 80+80 MHz signals with two ESGs or MXGs (RF summing)

20



Hardware for Generating 80 MHz Signals

Sampling rate limitations

• Max sample rate for many RF signal generators cannot support 2x oversampling

for 80 MHz bandwidth signals

• 1x oversampling results in images at band edges from aliasing: need to use

fractional oversampling to allow filtering of images

• Recommended HW: N5182A MXG (better EVM performance than E4438C ESG)

21

1x OSR Signal from N5182A MXG with images at band edges

N7617B Signal Studio Waveform from N5182A MXG: no images



Hardware for Generating 160 MHz Signals

Use wideband arbitrary waveform

generator (AWG) to create analog I/Q

signal, apply to external I/Q inputs in

RF signal generator

Need I/Q adjustments (example: IQ

skew, gain balance)

Recommended Agilent wideband AWGs:

• 81180A: 12 bits, up to 4.2 Gsa/s, 1

GHz BW/channel, 64MSa memory

• M8190A: 12 or 14 bits, up to 12 Gsa/s,

5 GHz analog BW, 2GSa memory,

AXIe form factor

22

81180A M8190A

160 MHz signal from 81180A and N5182A MXG



Test Challenge:

Analyzing Wider Bandwidth Signals

Need to analyze 40, 80, and 160 MHz BW signals

Digital predistortion may require measuring 3 to 5 times the BW of

desired signal: up to 800 MHz for 160 MHz signal

Software: all channel BWs supported by 89600 VSA

Hardware for single-channel measurements:

• N9030A PXA signal analyzer: up to 160 MHz demodulation BW,

best performance

• N9020A MXA signal analyzer: up to 40 MHz demod BW

• M9392A PXI Microwave VSA: up to 250 MHz BW

• Infiniium or Infiniivision oscilloscopes: 1 GHz or wider BW

23



Test Challenge:

Analyzing Wider Bandwidth Signals (MIMO)

Hardware for MIMO measurements:

• N7109A PXIe Multi-Channel Signal Analysis System: 2

or 4 channels, 40 MHz demodulation BW, 20 MHz to 6

GHz

• M9392A PXI Microwave VSA: 2 channels, up to 250 MHz

BW

• PXI MIMO System, includes M9362A-D01 Quad

Microwave Downconverter, M9202A digitizers, M9368C

attenuator, M9352A IF amp/attenuator, M9302A LO:

PXIe, 1 GHz BW, up to 4 channels

• Infiniium or Infiniivision oscilloscopes: 1 GHz or wider BW,

4 channels

24



802.11ac Signal Analysis Solutions

89600 VSA Software

N7109A Multi-Channel

Signal Analysis System

Infiniium

Oscilloscopes

PXA/MXA/EXA

Signal Analyzers

M9392A PXI Microwave

VSA (250 MHz BW)

PXI MIMO System

(800 MHz BW)

20 or 40

MHz BW

>40 MHz

BW

Single Channel 2x2 MIMO 3x3, 4x4 MIMO

PXA Signal Analyzer

(160 MHz BW)

N7109A Multi-Channel

Signal Analysis System

Infiniium

Oscilloscopes

• Supports all 802.11ac channel BWs

• Up to 4x4 MIMO

MXA/EXA

(25 MHz BW)

Infiniium

Oscilloscopes

Page 25

M9392A PXI Microwave

VSA (250 MHz BW)

Infiniium

Oscilloscopes

PXI MIMOSystem

(800 MHz BW)



Transmitter Tests Section 22.3.19 in 802.11ac Standard

Transmit spectrum mask

Spectral flatness

Transmit center frequency tolerance

Packet alignment

Symbol clock frequency tolerance

Modulation accuracy

• Transmit center frequency leakage

• Transmitter constellation error (EVM)

26

Most tests are similar to 802.11n; next slides will review

some differences and specification changes



Transmit Spectrum Mask

Spectral mask for 20 and 40 MHz are same as for 802.11n, except as shown in table

80 MHz spectral mask is an extension of 40 MHz mask

Measured with 100 kHz resolution bandwidth, 30 kHz video bandwidth

27

dBr = dB relative to maximum spectral density of the signal

Signal BW Offset Frequency 802.11n 802.11ac

20 MHz > 30 MHz Max of -45 dBr or -53 dBm/MHz Max of -40 dBr or -53 dBm/MHz

40 MHz > 60 MHz Max of -45 dBr or -56 dBm/MHz Max of -40 dBr or -56 dBm/MHz

80/160 MHz > 120/240 MHz Not applicable Max of -40 dBr or -59 dBm/MHz

40 MHz Channel

80 MHz Channel



Transmit Spectrum Mask for 160 and 80+80 MHz

160 MHz spectral mask is an extension of 40 and 80 MHz masks

For 80+80 MHz, mask is linear sum of the separate 80 MHz masks for values

from -20 dBr to -40 dBr. For values from 0 to -20 dBr, use higher value.

28

Example spectral mask for 80+80 MHz signals, with center frequencies separated by 160 MHz

160 MHz Channel



Spectral Flatness

Specified as deviation in power of each tested subcarrier from the average power

over a set of subcarriers with specified range of indices (same method as 802.11n)

Limits relaxed by 2 dB from the max/min values allowed for 802.11n: allows more

in-band filter ripple for better out-of-band rejection for transmitters

±2 dB +2,

-4 dB

±4 dB+4,

-6 dB

802.11ac 802.11a/n

middle ~70% of subcarriers

160 MHz

20,40,80 MHz

Page 29

October 2011



Transmitter Relative Constellation Error (RCE)or Error Vector Magnitude (EVM)

Test method same as 802.11n:

• Channel estimation (equalizer training) based on preamble only

• Pilots used for phase tracking

• Minimum 16 data symbols in frame, RMS average over at least 20 frames

30

Modulation Coding Rate 802.11nRCE (dB)

802.11acRCE (dB)

BPSK 1/2 -5 -5

QPSK 1/2 -10 -10

QPSK 3/4 -13 -13

16QAM 1/2 -16 -16

16QAM 3/4 -19 -19

64QAM 2/3 -22 -22

64QAM 3/4 -25 -25

64QAM 5/6 -28 -27

256QAM 3/4 N/A -30

256QAM 5/6 N/A -32



Receiver Tests Section 22.3.20 in 802.11ac Standard

Minimum input level sensitivity

Adjacent channel rejection

Nonadjacent channel rejection

Receiver maximum input level

Clear Channel Assessment (CCA) sensitivity

Again, most tests are similar to 802.11n; focus on key differences

31



Receiver Minimum Input Level Sensitivity

At input levels listed below, packet error rate shall be less than 10% for a PSDU

length of 4096 octets.

Applies to non-STBC modes, 800 ns guard interval, BCC coding.

Specs same as 802.11n, with additions for 802.11ac MCS and bandwidths.

32

Modulation Coding Rate

Minimum Sensitivity Level (dBm)

20 MHz 40 MHz 80 MHz 160 or 80+80 MHz

BPSK 1/2 -82 -79 -76 -73

QPSK 1/2 -79 -76 -73 -70

QPSK 3/4 -77 -74 -71 -68

16QAM 1/2 -74 -71 -68 -65

16QAM 3/4 -70 -67 -64 -61

64QAM 2/3 -66 -63 -60 -57

64QAM 3/4 -65 -62 -59 -56

64QAM 5/6 -64 -61 -58 -55

256QAM 3/4 -59 -56 -53 -50

256QAM 5/6 -57 -54 -51 -48



Adjacent & Nonadjacent Channel Rejection

Test procedure:

• Desired signal set to 3 dB above minimum sensitivity level.

• Apply interfering signal of same BW in adjacent or nonadjacent channel.

Interferer is a conformant OFDM signal that is unsynchronized with desired

signal, with minimum duty cycle of 50%.

• Interfering signal power increased until 10% PER occurs for PSDU length of

4096 octets.

• Power difference between interfering and desired signal is the rejection.

For 80+80 MHz, test done for channel below lower 80 MHz segment and

channel above higher 80 MHz segment; use smaller rejection value.

33



Adjacent & Nonadjacent Channel Rejection

34

Modulation Coding Rate Adjacent Channel Rejection (dB)

Nonadjacent Channel Rejection (dB)

20/40/80/160 MHz

80+80 MHz 20/40/80/160 MHz

80+80 MHz

BPSK 1/2 16 13 32 29

QPSK 1/2 13 10 29 26

QPSK 3/4 11 8 27 24

16QAM 1/2 8 5 24 21

16QAM 3/4 4 1 20 17

64QAM 2/3 0 -3 16 13

64QAM 3/4 -1 -4 15 12

64QAM 5/6 -2 -5 14 11

256QAM 3/4 -7 -10 9 6

256QAM 5/6 -9 -12 7 4

Minimum Adjacent and Nonadjacent Channel Rejection Levels

Specs same as 802.11n, with additions for 802.11ac MCS and bandwidths.



Summary

802.11ac new PHY features will include:

• Wider channel bandwidths: 40 and 80 MHz mandatory, 160 and 80+80

MHz optional

• Higher order modulation: 256QAM

• More spatial streams and antennas: up to 8

• Multi-user MIMO on downlink: up to 4 users, up to 4 streams per user, 8

streams total

Design challenges to deal with wider BW signals that require better EVM to

support 256QAM

Transmitter and receiver tests mostly the same as 802.11n with additions

for new bandwidths and modulation/coding rates

Agilent tools are available to address challenges from system simulation

and design to test, covering all 802.11ac bandwidths including 160 MHz.

35



SystemVueW1917 WLAN LibraryW1716 DPD Builder

N5182A MXGSignal Generator

Agilent 802.11ac Test Solutions

89600 VSA Software

N7617B Signal Studio

E4438C ESG Signal Generator

N7109A Multi-Channel Signal

Analysis System

N5106A PXB Baseband Generator and Channel

Emulator

Infiniium & Infiniivision

Oscilloscopes

PXA/MXA/EXASignal Analyzers

81180A Wideband AWG

M8190AWideband AWG

M9392A PXI Microwave VSA

Signal Generation Signal Analysis

PXI MIMO System



For More Information

Agilent Resources

• 802.11ac application and product info: www.agilent.com/find/802.11ac

• MIMO application and product info: www.agilent.com/find/mimo

• 89600 VSA product information: www.agilent.com/find/vsa

• Additional Webcasts and events: www.agilent.com/find/events

IEEE 802.11ac Standard

• Task group updates: http://www.ieee802.org/11/Reports/tgac_update.htm

• 802.11 working group project timelines:

http://www.ieee802.org/11/Reports/802.11_Timelines.htm

• 802.11ac working group documents:

https://mentor.ieee.org/802.11/documents?is_group=00ac

37

http://www.agilent.com/find/802.11ac

http://www.agilent.com/find/mimo

http://www.agilent.com/find/vsa

http://www.agilent.com/find/events



Appendix:

Additional Product Information

38



SystemVue W1917 WLAN Baseband Verification

Library

39

• 2011.10 version includes signal processing blocks and

802.11ac reference designs for transmitter and receiver

• Generate I/Q waveform files for download to instrument, or

analyze signals using 89600 VSA software

• Supported features:

- 20, 40, 80, 80+80, and 160 MHz BW

- BCC and LDPC coding, STBC

- 1-8 spatial streams, up to 8 Tx antennas

- All modulation types and MCS including 256QAM

- Cyclic shift insertion

- Single-user and multi-user MIMO

- Spatial mapping: direct mapping, spatial expansion, or

user defined

- WLAN TGac channel model

- Receiver supports timing and frequency sync, channel

estimation and phase tracking, demapping and decoding

• Price: SystemVue starts at $17,000 (U.S. list price). W1917 is

$15,600.



N5182A MXG and E4438C ESG

RF Vector Signal Generators

E4438C ESG

• 250 kHz to 6 GHz

• 64 MSa baseband memory

• 80 MHz modulation BW with

internal baseband generator

• ~200 MHz BW using external I/Q

inputs

N5182A MXG

• 100 kHz to 6 GHz

• 64 MSa baseband memory

• 100 MHz modulation BW with

internal baseband generator

• ~200 MHz BW using external I/Q

inputs

• Opt. 012 provides LO in/out for

phase coherency for MIMO

40



81180A 12-bit Arbitrary Waveform Generator

41

• Variable sample rate from 10 MSa/s to 4.2 GSa/s

• 1 or 2 channels, coupled and phase coherent or uncoupled

• 1 GHz modulation bandwidth per channel (2 GHz IQ

modulation)

• 1.5 GHz carrier frequency

• Up to 64 MSa memory

• Advanced sequencing capabilities

• 2 markers with adjustable width and levels



M8190A 12 GSa/s Arbitrary Waveform Generator

42

Precision AWG with two DAC settings- 14-bit resolution up to 8 GSa/s

- 12-bit resolution up to 12 GSa/s

• Variable sample rate from 125 MSa/s to 8 / 12 GSa/s

• Spurious-free-dynamic range (SFDR) up to 80 dBc typical

• Harmonic distortion (HD) up to-72 dBc typical

• Up to 2 GSa arbitrary waveform memory per channel with

advanced sequencing

• Analog bandwidth 5 GHz (direct DAC out)

• AXIe modular form factor



M9330A and N8241A Arbitrary Waveform

Generators

M9330A: PXI, 15-bits, 1.25 GSa/s

N8241A: LXI module, 15-bits, 1.25 GSa/s or 625

MSa/s

• Up to 500 MHz BW per channel for 1.25 Gsa/s, 250

MHz per channel for 625 Msa/s

• < -65 dBc spurious-free dynamic range

• 8 or 16 Msamples waveform memory per channel

• Supports sequencing

M9330A

N8241A

Note: These products are not recommended for

802.11ac due to lack of an adjustment for IQ skew,

resulting in poor EVM in the RF signal.



Agilent Wideband Arbitrary Waveform Generators

M8190A 81180A N8241A / M9330A

Max Sample Rate 8 GSa/s and 12 GSa/s

(variable)

4.2 GS/s (variable) 1.25 GS/s (fixed)

Resolution 14-bit 8 GSa/s, 12-bit 12 GSa/s 12 bit – 4 Markers 15 bit – 4 Markers

Sample Memory 128 MSa, 2 GSsa 16 / 64 MSa 8 / 16 MSa

Max. Bandwidth per

channel

5 GHz 1 GHz (1.5 GHz RF) 500 MHz

Spurious-free

Dynamic Range

<-80 dBc , (fout = 100 MHz,

measured DC to 1 GHz)

-68 dBc (fout = 10-3000 MHz)

< -50 dBc

(up to 500 MHz, with optional

reconstruction filter)

< -75 dBc (1 kHz - 500 MHz)

Harmonic Distortion <- 72 dBc (fout = 100 MHz, fs

= 7.2 GHz, 700 mVpp direct

DAC output)

< -58 dBc (SClk 4.2 GHz, 32 pt

sine waveform)

< -65 dBc (DC - 500 MHz)

Phase Noise / Floor - 90 dBc/Hz -90 dBc/Hz @10 kHz -115 dBc/Hz @10 kHz

Output

amplitude/Offset

DAC: 700 mVpp

DC: 1 Vpp, in – 1 V to + 3 V

window

AC: + 10 dBm

500 mVpp; +/- 1.5 V Offset,

DC amp: 2 Vpp

500 mVpp; +/- 0.2 V Offset

Sequencing 256K segments, 4M loops

granularity: 48/64,

2 loop levels

16K Segments, 1M loops

16K Sequences,

1K Scenario Table

512K Segments, 1M loops

32K Sequences, Infinite

16K Scenarios Table

Form factor Modular, AXIe Stand-alone instrument Modular, PXI, LXI

Price range $76K (1ch, 128M, no SEQ,

AMP)

$148K (2ch fully loaded)

$46K (1ch, 16 MS memory)

$81K (2ch, 64 MS memory)

$40K (2 ch, 8M)

$68K (2 ch, 16M, Seq, DDS)



Agilent MIMO Transmitter Test Solutions

Key Specs Conditions N7109A Infiniium 90000X Infiniium 90000 MXA/EXA

Max Channels4 Rx Channels

(phase coherent)

4 Rx Channels

(phase coherent)

4 Rx Channels

(phase coherent)

2 Rx channels

(with 2 MXA/EXA)

Frequency Range 20 MHz to 6 GHz DC to 16 GHz,32 GHz DC to 6 GHz,13 GHz20 Hz to

3.6,8.4/7,13.6, 26.5 GHz

Typical EVM

(2GHz, 20 MHz BW)

802.11n, 2x2

802.16e, 2x2

LTE, 2x2

LTE, 4x4

-44 dB

-42 dB

-44 dB (0.6%)

-41 dB (0.9%)

-

-

-

-43 dB (0.7%)

-44 dB

-39 dB

-46 dB (0.5%)

-41 dB (0.9%)

-47 dB

-45 dB

-50 dB (0.3%)

N/A

Measurement Speed Sec/update 0.2 – 1.8 3 - 490 3 - 490 0.2 – 1.3

3rd Order Intercept 6 GHz +6 dBm TBD TBD +18/+17 dBm

Displayed Average

Noise Level2 GHz -158 dBm/Hz TBD TBD

-151/-148 dBm

-166/-161 dBm (w/ preamp)

Phase Noise

1 GHz Carrier

Typical Offsets

10 kHz

100 kHz

1 MHz

-100 dBc/Hz

-99 dBc/Hz

-115 dBc/Hz

TBD TBD

-106/-102 dBc/Hz

-117/-114 dBc/Hz

-136/-135 dBc/Hz

Amplitude Accuracy1 GHz

6 GHz

± 1 dB typical

± 2 dB typicalTBD TBD

± 0.23/±0.27 dB

± 0.5 dB calculated

Analysis Bandwidth 40 MHz 16-32 GHz 6-13 GHz 25 MHz, 40 MHz Opt.

Preselected Tuner Yes No No No

Max Time Capture Msamples64 Msa/ch (1 or 2-ch)

32 Msa/ch (4-ch)2 GSa 1 GSa -

Pricing (Hardware)2-ch

4-ch

$77K

$96K$131K+ $67K+

$104K/$73K (2-ch only)

(8.4GHz,40MHz BW)

http://www.home.agilent.com/agilent/product.jspx?cc=US&lc=eng&nid=-34711.749314&imageindex=1



4-channel MIMO Rx

With M9202A, M9302A

and M9362A-D01

46

M9362A-D01

Downconvert

er

100 MHz Out1

100 MHz Out2

Video Trigger This

Channel

9 Slots for 4 Channels

16 Slots for 8 Channels

Notes:With M9302A LO, minimum RF frequency will be 2.25 GHz.M9362A-D01 has maximum input level of ~ -5 dBm and 0 dB gain.Input level to M9202A should be – 2 dBm.No gain control in M9362A-D01 or M9202A

Documents

Introduction to 802.11ac WLAN Technology and Testing · including 256QAM - BCC and LDPC coding, STBC - 1-8 spatial streams, up to 8 Tx antennas - Single-user and multi-user MIMO