R&S®FSV3-K91
WLAN Measurements
User Manual
(;ÜìÅ2)
1178945502
Version 09
This manual applies to the following R&S®FSV3000 and R&S®FSVA3000 models with firmware version
1.70 and higher:
●
R&S®FSV3004 (1330.5000K04) / R&S®FSVA3004 (1330.5000K05)
●
R&S®FSV3007 (1330.5000K07) / R&S®FSVA3007 (1330.5000K08)
●
R&S®FSV3013 (1330.5000K13) / R&S®FSVA3013 (1330.5000K14)
●
R&S®FSV3030 (1330.5000K30) / R&S®FSVA3030 (1330.5000K31)
●
R&S®FSV3044 (1330.5000K43) / R&S®FSVA3044 (1330.5000K44)
The following firmware options are described:
●
R&S FSV/A-K91 WLAN 802.11a,b,g (1330.5100.02)
●
R&S FSV/A-K91ac WLAN 802.11ac (1330.5116.02)
●
R&S FSV/A-K91ax WLAN 802.11ax (1346.339902)
●
R&S FSV/A-K91be WLAN 802.11be (1346.4966.02)
●
R&S FSV/A-K91n WLAN 802.11n (1330.5139.02)
●
R&S FSV/A-K91p WLAN 802.11p (1330.5122.02)
© 2022 Rohde & Schwarz GmbH & Co. KG
Muehldorfstr. 15, 81671 Muenchen, Germany
Phone: +49 89 41 29 - 0
Email: info@rohde-schwarz.com
Internet: www.rohde-schwarz.com
Subject to change – data without tolerance limits is not binding.
R&S® is a registered trademark of Rohde & Schwarz GmbH & Co. KG.
Trade names are trademarks of the owners.
1178.9455.02 | Version 09 | R&S®FSV3-K91
Throughout this manual, products from Rohde & Schwarz are indicated without the ® symbol , e.g. R&S®FSV/A3000 is indicated as
R&S FSV/A3000.
R&S®FSV3-K91
1 Documentation overview.......................................................................7
1.1 Getting started manual................................................................................................. 7
1.2 User manuals and help.................................................................................................7
1.3 Service manual..............................................................................................................7
1.4 Instrument security procedures.................................................................................. 8
1.5 Printed safety instructions...........................................................................................8
1.6 Data sheets and brochures.......................................................................................... 8
1.7 Release notes and open-source acknowledgment (OSA).........................................8
1.8 Application notes, application cards, white papers, etc........................................... 9
2 Welcome to the WLAN application.....................................................10
Contents
Contents
2.1 Starting the WLAN application...................................................................................11
2.2 Understanding the display information.................................................................... 11
3 Measurements and result displays.................................................... 14
3.1 WLAN I/Q measurement (modulation accuracy, flatness and tolerance).............. 14
3.2 Frequency sweep measurements..............................................................................62
4 Measurement basics............................................................................69
4.1 Signal processing for multicarrier measurements (IEEE 802.11a, g (OFDM), j, p)
...................................................................................................................................... 69
4.2 Signal processing for single-carrier measurements (IEEE 802.11b, g (DSSS)).... 76
4.3 Signal processing for MIMO measurements (IEEE IEEE 802.11 ac, ax, n, be)...... 82
4.4 Signal processing for high-efficiency wireless measurements (IEEE 802.11ax)..91
4.5 Signal processing for extremely high throughput (EHT) wireless measurements
(IEEE 802.11be)............................................................................................................96
4.6 Channels and carriers................................................................................................ 98
4.7 Recognized vs. analyzed PPDUs...............................................................................99
4.8 Demodulation parameters - logical filters................................................................ 99
4.9 I/Q data import and export....................................................................................... 101
4.10 Basics on input from I/Q data files.......................................................................... 102
4.11 Trigger basics............................................................................................................103
5 Configuration......................................................................................108
5.1 Multiple measurement channels and sequencer function.................................... 108
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5.2 Display configuration................................................................................................110
5.3 WLAN I/Q measurement configuration................................................................... 110
5.4 Frequency sweep measurements............................................................................193
6 Analysis.............................................................................................. 198
7 How to perform measurements in the WLAN application..............199
7.1 How to determine modulation accuracy, flatness and tolerance parameters for
7.2 How to analyze WLAN signals in a MIMO measurement setup............................ 200
7.3 How to determine the OBW, SEM, ACLR or CCDF for WLAN signals..................206
8 Optimizing and troubleshooting the measurement........................ 207
8.1 Optimizing the measurement results...................................................................... 207
8.2 Error messages and warnings.................................................................................208
Contents
WLAN signals............................................................................................................ 199
9 Remote commands for WLAN 802.11 measurements.................... 210
9.1 Common suffixes...................................................................................................... 210
9.2 Introduction............................................................................................................... 211
9.3 Activating WLAN 802.11 measurements.................................................................216
9.4 Selecting a measurement.........................................................................................219
9.5 Configuring the WLAN IQ measurement (modulation accuracy, flatness and toler-
ance)...........................................................................................................................226
9.6 Configuring frequency sweep measurements on WLAN 802.11 signals.............309
9.7 Configuring the result display................................................................................. 313
9.8 Starting a measurement........................................................................................... 333
9.9 Retrieving results......................................................................................................337
9.10 Analysis..................................................................................................................... 391
9.11 Status registers.........................................................................................................394
9.12 Deprecated commands.............................................................................................397
9.13 Programming examples (R&S FSV3 WLAN application).......................................401
Annex.................................................................................................. 407
A Sample rate and maximum usable I/Q bandwidth for RF input..... 407
A.1 Bandwidth extension options.................................................................................. 408
A.2 Relationship between sample rate, record length and usable I/Q bandwidth.....408
A.3 R&S FSV/A without additional bandwidth extension options...............................409
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A.4 R&S FSV/A with I/Q bandwidth extension option B40 or U40.............................. 410
A.5 R&S FSV/A with I/Q bandwidth extension option B200.........................................410
A.6 R&S FSV/A with I/Q bandwidth extension option B400.........................................411
A.7 R&S FSV/A with I/Q bandwidth extension option B600.........................................411
A.8 R&S FSV/A with I/Q bandwidth extension option B1000.......................................411
Contents
List of commands (WLAN)................................................................ 412
Index....................................................................................................422
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Contents
6User Manual 1178.9455.02 ─ 09
R&S®FSV3-K91
1 Documentation overview
1.1 Getting started manual
Documentation overview
Service manual
This section provides an overview of the R&S FSV/A user documentation. Unless
specified otherwise, you find the documents on the R&S FSV/A product page at:
www.rohde-schwarz.com/product/FSVA3000.html/
www.rohde-schwarz.com/product/FSV3000.html
Introduces the R&S FSV/A and describes how to set up and start working with the
product. Includes basic operations, typical measurement examples, and general information, e.g. safety instructions, etc.
A printed version is delivered with the instrument. A PDF version is available for download on the Internet.
1.2 User manuals and help
Separate user manuals are provided for the base unit and the firmware applications:
●
Base unit manual
Contains the description of all instrument modes and functions. It also provides an
introduction to remote control, a complete description of the remote control commands with programming examples, and information on maintenance, instrument
interfaces and error messages. Includes the contents of the getting started manual.
●
Firmware application manual
Contains the description of the specific functions of a firmware application, including remote control commands. Basic information on operating the R&S FSV/A is
not included.
The contents of the user manuals are available as help in the R&S FSV/A. The help
offers quick, context-sensitive access to the complete information for the base unit and
the firmware applications.
All user manuals are also available for download or for immediate display on the Internet.
1.3 Service manual
Describes the performance test for checking the rated specifications, module replacement and repair, firmware update, troubleshooting and fault elimination, and contains
mechanical drawings and spare part lists.
7User Manual 1178.9455.02 ─ 09
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1.4 Instrument security procedures
1.5 Printed safety instructions
Documentation overview
Release notes and open-source acknowledgment (OSA)
The service manual is available for registered users on the global Rohde & Schwarz
information system (GLORIS):
R&S®FSVA3000/FSV3000 Service manual
Deals with security issues when working with the R&S FSV/A in secure areas. It is
available for download on the Internet.
Provides safety information in many languages. The printed document is delivered with
the product.
1.6 Data sheets and brochures
The data sheet contains the technical specifications of the R&S FSV/A. It also lists the
firmware applications and their order numbers, and optional accessories.
The brochure provides an overview of the instrument and deals with the specific characteristics.
See www.rohde-schwarz.com/brochure-datasheet/FSV3000 /
www.rohde-schwarz.com/brochure-datasheet/FSVA3000
1.7 Release notes and open-source acknowledgment (OSA)
The release notes list new features, improvements and known issues of the current
firmware version, and describe the firmware installation.
The open-source acknowledgment document provides verbatim license texts of the
used open source software.
See www.rohde-schwarz.com/firmware/FSV3000 /
www.rohde-schwarz.com/firmware/FSVA3000
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1.8 Application notes, application cards, white papers,
Documentation overview
Application notes, application cards, white papers, etc.
etc.
These documents deal with special applications or background information on particular topics.
See www.rohde-schwarz.com/application/FSV3000 /
www.rohde-schwarz.com/application/FSVA3000
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2 Welcome to the WLAN application
Welcome to the WLAN application
The R&S FSV3 WLAN application extends the functionality of the R&S FSV/A to
enable accurate and reproducible Tx measurements of a WLAN device under test
(DUT) in accordance with the standards specified for the device. The following standards are currently supported (if the corresponding firmware option is installed):
●
IEEE standards 802.11a
●
IEEE standards 802.11ac (SISO + MIMO)
●
IEEE standards 802.11b
●
IEEE standards 802.11be
●
IEEE standards 802.11g (OFDM)
●
IEEE standards 802.11g (DSSS)
●
IEEE standards 802.11j
●
IEEE standards 802.11n (SISO + MIMO)
●
IEEE standards 802.11p
●
IEEE standards 802.11ax (SISO + MIMO)
The R&S FSV3 WLAN application features:
Modulation measurements
●
"Constellation" diagram for demodulated signal
●
"Constellation" diagram for individual carriers
●
I/Q offset and I/Q imbalance
●
Modulation error (EVM) for individual carriers or symbols
●
Amplitude response and group-delay distortion (spectrum flatness)
●
Carrier and symbol frequency errors
Further measurements and results
●
Amplitude statistics ("CCDF") and crest factor
●
FFT, also over a selected part of the signal, e.g. preamble
●
Payload bit information
●
Freq/Phase Err vs. Preamble
This user manual contains a description of the functionality that is specific to the application, including remote control operation.
General R&S FSV/A functions
The application-independent functions for general tasks on the R&S FSV/A are also
available for WLAN 802.11 measurements and are described in the R&S FSV/A user
manual. In particular, this comprises the following functionality:
●
Data management
●
General software preferences and information
The latest version is available for download at the product homepage
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2.1 Starting the WLAN application
Welcome to the WLAN application
Understanding the display information
http://www.rohde-schwarz.com/product/FSV3000.html.
Installation
You can find detailed installation instructions in the R&S FSV/A Getting Started manual
or in the Release Notes.
The WLAN measurements require a special application on the R&S FSV/A.
To activate the WLAN application
1. Select the [MODE] key.
A dialog box opens that contains all operating modes and applications currently
available on your R&S FSV/A.
2. Select the "WLAN" item.
The R&S FSV/A opens a new measurement channel for the WLAN application.
The measurement is started immediately with the default settings. It can be configured
in the WLAN "Overview" dialog box, which is displayed when you select the "Overview"
softkey from any menu (see Chapter 5.3.1, "Configuration overview", on page 111).
2.2 Understanding the display information
The following figure shows a measurement diagram during analyzer operation. All
information areas are labeled. They are explained in more detail in the following sections.
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Welcome to the WLAN application
Understanding the display information
1
2
3
4
5
1 = Channel bar for firmware and measurement settings
2 = Window title bar with diagram-specific (trace) information
3 = Diagram area with marker information
4 = Diagram footer with diagram-specific information, depending on result display
5 = Instrument status bar with error messages, progress bar and date/time display
Channel bar information
In the WLAN application, the R&S FSV/A shows the following settings:
Table 2-1: Information displayed in the channel bar in the WLAN application
Label Description
"Sample Rate Fs" Input sample rate
"PPDU / MCS Index / GI" IEEE 802.11a, ac, g (OFDM), j, n, p:
The PPDU type, MCS index and guard interval (GI) used for the analysis
of the signal; Depending on the demodulation settings, these values are
either detected automatically from the signal or the user settings are
applied.
"PPDU / MCS Index / GI+HELTF"
"PPDU / MCS/ GI+EHT-LTF" WLAN 802.11be:
WLAN 802.11ax: PPDU type, MCS index, sum of guard interval (GI)
length and high efficiency long training field (HE-LTF) length used for the
analysis of the signal
PPDU type, MCS index, sum of guard interval (GI) length and extremely
high throughput long training field (EHT-LTF) length used for the analysis
of the signal
"PPDU / Data Rate" WLAN 802.11b:
The PPDU type and data rate used for the analysis of the signal; Depending on the demodulation settings, these values are either detected automatically from the signal or the user settings are applied.
"Standard" Selected WLAN measurement standard
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Welcome to the WLAN application
Understanding the display information
Label Description
"Meas Setup" Number of Transmitter (Tx) and Receiver (Rx) channels used in the mea-
surement (for MIMO)
"Capt time / Samples" Duration of signal capture and number of samples captured
"Data Symbols" The minimum and maximum number of data symbols that a PPDU may
have if it is to be considered in results analysis.
"PPDUs" [x of y (z)] For statistical evaluation over PPDUs (see "PPDU Statistic Count / No of
PPDUs to Analyze" on page 179):
<x> PPDUs of totally required <y> PPDUs have been analyzed so far.
<z> PPDUs were analyzed in the most recent sweep.
In addition, the channel bar also displays information on instrument settings that affect
the measurement results even though this is not immediately apparent from the display
of the measured values (e.g. transducer or trigger settings). This information is displayed only when applicable for the current measurement. For details see the
R&S FSV/A Getting Started manual.
Window title bar information
For each diagram, the header provides the following information:
5
1
Figure 2-1: Window title bar information in the WLAN application
1 = Window number
2 = Window type
3 = Further measurement settings
4 = Trace color
5 = Trace number
6 = Trace mode
2
3
4
6
Diagram footer information
The diagram footer (beneath the diagram) contains the start and stop values for the
displayed x-axis range.
Status bar information
Global instrument settings, the instrument status and any irregularities are indicated in
the status bar beneath the diagram. Furthermore, the progress of the current operation
is displayed in the status bar. Click on a displayed warning or error message to obtain
more details (see also .
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3 Measurements and result displays
3.1 WLAN I/Q measurement (modulation accuracy, flat-
Measurements and result displays
WLAN I/Q measurement (modulation accuracy, flatness and tolerance)
The R&S FSV3 WLAN application provides several different measurements in order to
determine the parameters described by the WLAN 802.11 specifications.
For details on selecting measurements, see Chapter 5.2, "Display configuration",
on page 110.
● WLAN I/Q measurement (modulation accuracy, flatness and tolerance)................14
● Frequency sweep measurements...........................................................................62
ness and tolerance)
The default WLAN I/Q measurement captures the I/Q data from the WLAN signal using
a (nearly rectangular) filter with a relatively large bandwidth. The I/Q data captured with
this filter includes magnitude and phase information. That allows the R&S FSV3 WLAN
application to demodulate broadband signals and determine various characteristic signal parameters in just one measurement. Modulation accuracy, spectrum flatness, center frequency tolerance and symbol clock tolerance are only a few of the characteristic
parameters.
Other parameters specified in the WLAN 802.11 standard require a better signal-tonoise level or a smaller bandwidth filter than the I/Q measurement provides and must
be determined in separate measurements (see Chapter 3.2, "Frequency sweep mea-
surements", on page 62).
● Modulation accuracy, flatness and tolerance parameters.......................................14
● Evaluation methods for WLAN IQ measurements.................................................. 25
3.1.1 Modulation accuracy, flatness and tolerance parameters
The default WLAN I/Q measurement (Modulation Accuracy, Flatness,...) captures the
I/Q data from the WLAN signal and determines all the following I/Q parameters in a
single sweep.
Table 3-1: WLAN I/Q parameters for IEEE 802.11a, ac, ax, g (OFDM), j, n, p, be
Parameter Description Keyword for remote
query (FETCh:BURSt:)
General measurement parameters
Sample RateFsInput sample rate
PPDU Type of analyzed PPDUs
*) the limits can be changed via remote control (not manually, see Chapter 9.5.9, "Limits", on page 302); in
this case, the currently defined limits are displayed here
PPDU:TYPE
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Measurements and result displays
WLAN I/Q measurement (modulation accuracy, flatness and tolerance)
Parameter Description Keyword for remote
query (FETCh:BURSt:)
MCS Index Modulation and Coding Scheme (MCS) index of the analyzed
PPDUs
Data Rate Data rate used for analysis of the signal
(IEEE 802.11a only)
GI
/ GI+HE-LTF
/ GI+EHT-LTF
Meas Setup Number of Transmitter (Tx) and Receiver (Rx) channels used
Capture time Duration of signal capture
Samples Number of samples captured
Data Symbols The minimum and maximum number of data symbols that a
PPDU parameters
Analyzed
PPDUs
Guard interval length for current measurement
Guard interval and high-efficiency long training field length
(IEEE 802.11ax only)
Guard interval and length of EHT long training field (IEEE
802.11be only)
in the measurement
PPDU can have if it is to be considered in results analysis
For statistical evaluation of PPDUs (see "PPDU Statistic
Count / No of PPDUs to Analyze" on page 179): <x> PPDUs of
the required <y> PPDUs have been analyzed so far. <z> indicates the number of analyzed PPDUs in the most recent
sweep.
MCSindex
GINTerval
Number of recognized
PPDUs
(global)
Number of
analyzed
PPDUs
(global)
Number of
analyzed
PPDUs in
physical channel
TX and Rx carrier parameters
I/Q offset [dB] Transmitter center frequency leakage relative to the total Tx
Gain imbalance [%/dB]
Quadrature
offset [°]
*) the limits can be changed via remote control (not manually, see Chapter 9.5.9, "Limits", on page 302); in
this case, the currently defined limits are displayed here
Number of PPDUs recognized in capture buffer
Number of analyzed PPDUs in capture buffer
Number of PPDUs analyzed in entire signal (if available)
channel power (see Chapter 3.1.1.1, "I/Q offset", on page 19)
Amplification of the quadrature phase component of the signal
relative to the amplification of the in-phase component (see
Chapter 3.1.1.2, "Gain imbalance", on page 19)
Deviation of the quadrature phase angle from the ideal 90°
(see Chapter 3.1.1.3, "Quadrature offset", on page 20).
COUNt
COUNt:ALL
IQOFset
GIMBalance
QUADoffset
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Measurements and result displays
WLAN I/Q measurement (modulation accuracy, flatness and tolerance)
Parameter Description Keyword for remote
query (FETCh:BURSt:)
I/Q skew [s] Delay of the transmission of the data on the I path compared
to the Q path (see Chapter 3.1.1.4, "I/Q skew", on page 21)
PPDU power
[dBm]
Crest factor
[dB]
MIMO Cross
Power [dB]
MIMO Channel Power
[dBm]
Center frequency error
[Hz]
Symbol clock
error [ppm]
Mean PPDU power
The ratio of the peak power to the mean power of the signal
(also called Peak to Average Power Ratio, PAPR).
Sum of RMS power from all cross streams
RMS power for each effective channel path from all active carriers.
Frequency error between the signal and the current center frequency of the R&S FSV/A; the corresponding limits specified
in the standard are also indicated*)
The absolute frequency error includes the frequency error of
the R&S FSV/A and that of the DUT. If possible, synchronize
the transmitter R&S FSV/A and the DUT using an external reference.
See R&S FSV/A user manual > Instrument setup > External
reference
Clock error between the signal and the sample clock of the
R&S FSV/A in parts per million (ppm), i.e. the symbol timing
error; the corresponding limits specified in the standard are
also indicated *)
If possible, synchronize the transmitter R&S FSV/A and the
DUT using an external reference.
See R&S FSV/A user manual > Instrument setup > External
reference
IQSKew
CRESt
MCPower
MCHPower
CFERror
CPE Common phase error
Stream parameters
BER Pilot [%] Bit error rate (BER) of the pilot carriers
EVM all carriers [%/dB]
EVM data carriers [%/dB]
EVM pilot carriers [%/dB]
*) the limits can be changed via remote control (not manually, see Chapter 9.5.9, "Limits", on page 302); in
this case, the currently defined limits are displayed here
EVM (Error Vector Magnitude) of the payload symbols over all
carriers; the corresponding limits specified in the standard are
also indicated*)
EVM (Error Vector Magnitude) of the payload symbols over all
data carriers; the corresponding limits specified in the standard
are also indicated*)
EVM (Error Vector Magnitude) of the payload symbols over all
pilot carriers; the corresponding limits specified in the standard
are also indicated*)
CPERror
BERPilot
EVM:ALL
EVM:DATA
EVM:PILot
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Measurements and result displays
WLAN I/Q measurement (modulation accuracy, flatness and tolerance)
Table 3-2: WLAN I/Q parameters for IEEE 802.11b or g (DSSS)
Parameter Description Keyword for remote
query
(FETCh:BURSt:)
Sample RateFsInput sample rate
PPDU Type of the analyzed PPDU
Data Rate Data rate used for analysis of the signal
Meas Setup Number of Transmitter (Tx) and Receiver (Rx) channels used in
the measurement
Capture time Duration of signal capture
No. of Samples Number of samples captured (= sample rate * capture time)
No. of Data
Symbols
PPDU parameters
Analyzed
PPDUs
Number of recognized
PPDUs
(global)
Number of
analyzed
PPDUs
(global)
The minimum and maximum number of data symbols that a
PPDU can have if it is to be considered in results analysis
For statistical evaluation of PPDUs (see "PPDU Statistic Count /
No of PPDUs to Analyze" on page 179): <x> PPDUs of the
required <y> PPDUs have been analyzed so far. <z> indicates
the number of analyzed PPDUs in the most recent sweep.
Number of PPDUs recognized in capture buffer
Number of analyzed PPDUs in capture buffer
PPDU:TYPE
COUNt
Number of
analyzed
PPDUs in
physical channel
Peak vector
error
PPDU EVM EVM (Error Vector Magnitude) over the complete PPDU includ-
I/Q offset [dB] Transmitter center frequency leakage relative to the total Tx
Gain imbalance [%/dB]
Quadrature
error [°]
Number of PPDUs analyzed in entire signal (if available)
Peak vector error (EVM) over the complete PPDU including the
preamble in % and in dB; calculated according to the IEEE
802.11b or g (DSSS) definition of the normalized error vector
magnitude (see "Peak vector error (IEEE method)"
on page 23);
The corresponding limits specified in the standard are also indicated *)
ing the preamble in % and dB
channel power (see Chapter 3.1.1.1, "I/Q offset", on page 19)
Amplification of the quadrature phase component of the signal
relative to the amplification of the in-phase component (see
Chapter 3.1.1.2, "Gain imbalance", on page 19)
Measure for the crosstalk of the Q-branch into the I-branch (see
"Gain imbalance, I/Q offset, quadrature error" on page 79).
COUNt:ALL
EVM:DIRect
PPDU:EVM:ALL
IQOFset
GIMBalance
QUADoffset
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Measurements and result displays
WLAN I/Q measurement (modulation accuracy, flatness and tolerance)
Parameter Description Keyword for remote
query
(FETCh:BURSt:)
Center frequency error
[Hz]
Chip clock
error [ppm]
Rise time Time the signal needs to increase its power level from 10% to
Fall time Time the signal needs to decrease its power level from 90% to
Frequency error between the signal and the current center frequency of the R&S FSV/A; the corresponding limits specified in
the standard are also indicated*)
The absolute frequency error includes the frequency error of the
R&S FSV/A and that of the DUT. If possible, synchronize the
transmitter R&S FSV/A and the DUT using an external reference.
See R&S FSV/A user manual > Instrument setup > External reference
Clock error between the signal and the chip clock of the
R&S FSV/A in parts per million (ppm), i.e. the chip timing error;
the corresponding limits specified in the standard are also indicated *)
If possible, synchronize the transmitter R&S FSV/A and the DUT
using an external reference.
See R&S FSV/A user manual > Instrument setup > External reference
90% of the maximum or the average power (depending on the
reference power setting)
The corresponding limits specified in the standard are also indicated *)
10% of the maximum or the average power (depending on the
reference power setting)
The corresponding limits specified in the standard are also indicated *)
CFERror
TRISe
TFALl
Mean power
[dBm]
Peak power
[dBm]
Crest factor
[dB]
Mean PPDU power
Peak PPDU power
The ratio of the peak power to the mean power of the PPDU
(also called Peak to Average Power Ratio, PAPR).
PEAK
CRESt
The R&S FSV3 WLAN application also performs statistical evaluation over several
PPDUs and displays one or more of the following results:
Table 3-3: Calculated summary results
Result type Description
Min Minimum measured value
Mean/ Limit Mean measured value / limit defined in standard
Max/Limit Maximum measured value / limit defined in standard
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3.1.1.1 I/Q offset
Measurements and result displays
WLAN I/Q measurement (modulation accuracy, flatness and tolerance)
An I/Q offset indicates a carrier offset with fixed amplitude. This results in a constant
shift of the I/Q axes. The offset is normalized by the mean symbol power and displayed
in dB.
Figure 3-1: I/Q offset in a vector diagram
3.1.1.2 Gain imbalance
An ideal I/Q modulator amplifies the I and Q signal path by exactly the same degree.
The imbalance corresponds to the difference in amplification of the I and Q channel
and therefore to the difference in amplitude of the signal components. In the vector diagram, the length of the I vector changes relative to the length of the Q vector.
The result is displayed in dB and %, where 1 dB offset corresponds to roughly 12 %
difference between the I and Q gain, according to the following equation:
Positive values mean that the Q vector is amplified more than the I vector by the corresponding percentage. For example, using the figures mentioned above:
Figure 3-2: Positive gain imbalance
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Negative values mean that the I vector is amplified more than the Q vector by the corresponding percentage. For example, using the figures mentioned above:
Figure 3-3: Negative gain imbalance
3.1.1.3 Quadrature offset
An ideal I/Q modulator sets the phase angle between the I and Q path mixer to exactly
90 degrees. With a quadrature offset, the phase angle deviates from the ideal 90
degrees, the amplitudes of both components are of the same size. In the vector diagram, the quadrature offset causes the coordinate system to shift.
A positive quadrature offset means a phase angle greater than 90 degrees:
Figure 3-4: Positive quadrature offset
A negative quadrature offset means a phase angle less than 90 degrees:
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3.1.1.4 I/Q skew
Measurements and result displays
WLAN I/Q measurement (modulation accuracy, flatness and tolerance)
Figure 3-5: Negative quadrature offset
If transmission of the data on the I path is delayed compared to the Q path, or vice
versa, the I/Q data becomes skewed.
The I/Q skew results can be compensated for together with Gain imbalance and Quad-
rature offset (see "I/Q Mismatch Compensation" on page 145).
3.1.1.5 I/Q mismatch
I/Q mismatch is a comprehensive term for Gain imbalance, Quadrature offset, and I/Q
skew.
Compensation for I/Q mismatch is useful, for example, if the device under test is
known to be affected by these impairments but the EVM without these effects is of
interest. Note, however, that measurements strictly according to IEEE 802.11-2012,
IEEE 802.11ac-2013 WLAN standard must not use compensation.
3.1.1.6 RF carrier suppression (IEEE 802.11b, g (DSSS))
Standard definition
The RF carrier suppression, measured at the channel center frequency, shall be at
least 15 dB below the peak SIN(x)/x power spectrum. The RF carrier suppression shall
be measured while transmitting a repetitive 01 data sequence with the scrambler disabled using DQPSK modulation. A 100 kHz resolution bandwidth shall be used to perform this measurement.
Comparison to IQ offset measurement in the R&S FSV3 WLAN application
The IQ offset measurement in the R&S FSV3 WLAN application returns the current
carrier feedthrough normalized to the mean power at the symbol timings. This measurement does not require a special test signal and is independent of the transmit filter
shape.
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3.1.1.7 EVM measurement
Measurements and result displays
WLAN I/Q measurement (modulation accuracy, flatness and tolerance)
The RF carrier suppression measured according to the standard is inversely proportional to the IQ offset measured in the R&S FSV3 WLAN application. The difference (in
dB) between the two values depends on the transmit filter shape. Determine it with a
reference measurement.
The following table lists the difference exemplarily for three transmit filter shapes
(±0.5 dB):
Transmit filter – IQ-Offset [dB] – RF-Carrier-Suppression [dB]
Rectangular 11 dB
Root raised cosine, "α" = 0.3 10 dB
Gaussian, "α" = 0.3 9 dB
The R&S FSV3 WLAN application provides two different types of EVM calculation.
PPDU EVM (direct method)
The PPDU EVM (direct) method evaluates the root mean square EVM over one PPDU.
That is the square root of the averaged error power normalized by the averaged reference power:
Before calculation of the EVM, tracking errors in the measured signal are compensated
for if specified by the user. In the ideal reference signal, the tracking errors are always
compensated for. Tracking errors include phase (center frequency error + common
phase error), timing (sampling frequency error) and gain errors. Quadrature offset and
gain imbalance errors, however, are not corrected.
The PPDU EVM is not part of the IEEE standard and no limit check is specified. Nevertheless, this commonly used EVM calculation can provide some insight in modulation
quality and enables comparisons to other modulation standards.
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Figure 3-6: I/Q diagram for EVM calculation
Peak vector error (IEEE method)
The peak vector error (Peak EVM) is defined in section 18.4.7.8 "Transmit modulation
accuracy" of the IEEE 802.11b standard. The phase, timing and gain tracking errors of
the measurement signal (center frequency error, common phase error, sampling frequency error) are compensated for before EVM calculation.
The standard does not specify a normalization factor for the error vector magnitude. To
get an EVM value that is independent of the level, the R&S FSV3 WLAN application
normalizes the EVM values. Thus, an EVM of 100% indicates that the error power on
the I- or Q-channels equals the mean power on the I- or Q-channels, respectively.
The peak vector error is the maximum EVM over all payload symbols and all active
carriers for one PPDU. If more than one PPDU is analyzed the Min / Mean / Max columns show the minimum, mean or maximum Peak EVM of all analyzed PPDUs. This
can be the case, for example, if several analyzed PPDUs are in the capture buffer or
due to the PPDU Statistic Count / No of PPDUs to Analyze setting.
The IEEE 802.11b or g (DSSS) standards allow a peak vector error of less than 35%.
In contrary to the specification, the R&S FSV3 WLAN application does not limit the
measurement to 1000 chips length, but searches the maximum over the whole PPDU.
3.1.1.8 Unused tone error
Similarly to the adjacent channel power requirements for other WLAN standards, the
IEEE 802.11ax standard specifies limits for power leakage into neighboring resource
units (IEEE P802.11ax/D1.2, "Transmitter modulation accuracy (EVM) test" section). In
high-efficiency wireless signals, the subcarriers or frequencies that are not used for
active transmission are referred to as unused tones. Thus, the parameter that indicates
the power leakage into adjacent resource units is referred to as the unused tone error.
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The R&S FSV3 WLAN application provides a dedicated result display for the IEEE
802.11ax standard for HE trigger-based PPDUs.
The region in which the power leakage must be determined depends on the size and
position within the channel of the resource unit being checked. Up to 3 times the number of subcarriers contained in the resource unit are checked on either side of it. Any
remaining subcarriers are checked against the fixed limit of -35 dB. However, only subcarriers in the same channel are evaluated. If the resource unit is at the edge of the
channel, possibly no or not enough adjacent subcarriers are available in the channel.
Assuming the resource unit contains n carriers, the adjacent n subcarriers are
assigned a certain limit, the next n subcarriers have another limit, and the third n subcarriers have yet another limit. All subcarriers beyond that have a fixed limit of -35 dB
in relation to the EVM tolerance limit for the original resource unit ("[IEEE P802.11ax/
D1.2] Equation (28-123)").
Since the n subcarriers can be allocated to several different resource units, we refer to
such a subset as an RU group. The RU group containing the resource unit to be
checked is referred to as RU
are referred to as RU groups RU
remaining subcarriers are referred to as the RU groups -35
. The other subsets evaluated on either side of the RU
Idx
Idx-1
, RU
Idx-2
, RU
, and RU
Idx-3
, RU
Idx+1
dB
LHS (left-hand side)
Idx+2
, RU
Idx+3
Idx
. The
and -35 dB RHS (right-hand side).
The size of the evaluated RU groups corresponds to the size of the RU
, even if the
Idx
actual resource unit allocation in the channel differs. However, the R&S FSV3 WLAN
application measures one unused tone value for each set of 26 subcarriers. For each
RU group, the mean, maximum, and minimum of these values is determined. In the
Unused Tone Error Summary, the "RU Size [RU26]" is indicated as the quotient of the
RU size divided by the RU26 size (see "[IEEE P802.11ax/D1.2] Equation (28-123)").
Thus, the "RU Size [RU26]" also indicates the number of measurement points determined for each RU group.
Figure 3-7 illustrates the RU groups for which the unused tone error is determined for
different RU indexes. The blue dots indicate individual power measurement points in
the channel.
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Figure 3-7: RU groups to be checked for unused tone error for different RU indexes
3.1.2 Evaluation methods for WLAN IQ measurements
The captured I/Q data from the WLAN signal can be evaluated using various different
methods without having to start a new measurement or sweep. Which results are displayed depends on the selected evaluation.
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Result display windows
All evaluations available for the selected WLAN measurement are displayed in SmartGrid mode.
To activate SmartGrid mode, do one of the following:
●
Select the "SmartGrid" icon from the toolbar.
●
Select the "Display Config" button in the configuration "Overview" (see Chapter 5.2,
"Display configuration", on page 110).
●
Press the [MEAS CONFIG] hardkey and then select the "Display Config" softkey.
To close the SmartGrid mode and restore the previous softkey menu select the
"Close" icon in the right-hand corner of the toolbar, or press any key.
The selected evaluation method not only affects the result display in a window, but also
the results of the trace data query in remote control (see TRACe[:DATA]?
on page 373).
The WLAN measurements provide the following evaluation methods:
AM/AM.......................................................................................................................... 27
AM/PM.......................................................................................................................... 28
AM/EVM........................................................................................................................28
Bitstream.......................................................................................................................29
Constellation................................................................................................................. 31
Constellation vs Carrier.................................................................................................33
EVM vs Carrier..............................................................................................................34
EVM vs Chip................................................................................................................. 35
EVM vs Symbol.............................................................................................................35
FFT Spectrum............................................................................................................... 36
Freq. Error vs Preamble................................................................................................37
Gain Imbalance vs Carrier............................................................................................ 38
Group Delay..................................................................................................................39
Magnitude Capture........................................................................................................40
Phase Error vs Preamble..............................................................................................40
Phase Tracking............................................................................................................. 41
PLCP Header (IEEE 802.11b, g (DSSS).......................................................................42
PvT Full PPDU..............................................................................................................43
PvT Rising Edge........................................................................................................... 44
PvT Falling Edge...........................................................................................................45
Quad Error vs Carrier....................................................................................................45
Result Summary Detailed............................................................................................. 46
Result Summary Global................................................................................................ 47
Signal Content Detailed (IEEE 802.11ax, be)............................................................... 49
Signal Field................................................................................................................... 50
└ IEEE 802.11a, g (OFDM), j, p......................................................................... 51
└ IEEE 802.11ac................................................................................................ 52
└ IEEE 802.11n..................................................................................................53
└ IEEE 802.11ax HE SU PPDU (DL/UL), HE Extended Range SU PPDU........54
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└ IEEE 802.11ax HE MU PPDU (DL).................................................................55
└ IEEE 802.11ax HE Trigger-based PPDU (UL)................................................56
└ IEEE 802.11be EHT MU PPDU (DL) / IEEE 802.11be EHT trigger-based
PPDU (UL)......................................................................................................57
Spectrum Flatness........................................................................................................ 58
Spectrum Flatness Result Summary.............................................................................60
Unused Tone Error........................................................................................................60
Unused Tone Error Summary........................................................................................61
AM/AM
This result display shows the measured and the reference signal in the time domain.
For each sample, the x-axis value represents the amplitude of the reference signal and
the y-axis value represents the amplitude of the measured signal.
The reference signal is derived from the measured signal after frequency and time synchronization, channel equalization and demodulation of the signal. The equivalent time
domain representation of the reference signal is calculated by reapplying all the impairments that were removed before demodulation.
The trace is determined by calculating a polynomial regression model of a specified
degree (see "Polynomial degree for curve fitting" on page 186) for the scattered measurement vs. reference signal data. The resulting regression polynomial is indicated in
the window title of the result display.
Note: The measured signal and reference signal are complex signals.
This result display is not available for single-carrier measurements (IEEE 802.11b, g
(DSSS)) or IEEE 802.11ax, be.
Remote command:
LAY:ADD? '1',RIGH,AMAM, see LAYout:ADD[:WINDow]? on page 316
Or:
CONFigure:BURSt:AM:AM[:IMMediate] on page 221
Polynomial degree:
CONFigure:BURSt:AM:AM:POLYnomial on page 326
Results:
TRACe[:DATA]?, see Chapter 9.9.4.1, "AM/AM", on page 379
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AM/PM
This result display shows the measured and the reference signal in the time domain.
For each sample, the x-axis value represents the amplitude of the reference signal.
The y-axis value represents the angle difference of the measured signal minus the reference signal.
This result display is not available for single-carrier measurements (IEEE 802.11b, g
(DSSS)).
Remote command:
LAY:ADD? '1',RIGH,AMPM, see LAYout:ADD[:WINDow]? on page 316
Or:
CONFigure:BURSt:AM:PM[:IMMediate] on page 221
Querying results:
TRACe[:DATA]?, see Chapter 9.9.4.2, "AM/PM", on page 379
AM/EVM
This result display shows the measured and the reference signal in the time domain.
For each sample, the x-axis value represents the amplitude of the reference signal.
The y-axis value represents the length of the error vector between the measured signal
and the reference signal.
The length of the error vector is normalized with the power of the corresponding reference signal sample.
This result display is not available for single-carrier measurements (IEEE 802.11b, g
(DSSS)).
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Remote command:
LAY:ADD? '1',RIGH,AMEV, see LAYout:ADD[:WINDow]? on page 316
Or:
CONFigure:BURSt:AM:EVM[:IMMediate] on page 221
Querying results:
TRACe[:DATA]?, see Chapter 9.9.4.3, "AM/EVM", on page 379
Bitstream
This result display shows a demodulated payload data stream for all analyzed PPDUs
of the currently captured I/Q data as indicated in the "Magnitude Capture" display. The
bitstream is derived from the constellation diagram points using the 'constellation bit
encoding' from the corresponding WLAN standard. See, for example, IEEE Std.
802.11-2012 'Fig. 18-10 BPSK, QPSK, 16-QAM and 64-QAM constellation bit encoding'. Thus, the bitstream is NOT channel-decoded.
For multicarrier measurements (IEEE 802.11a, ac, g (OFDM), j, n, p), the results are
grouped by symbol and carrier.
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Figure 3-8: Bitstream result display for IEEE 802.11a, ac, g (OFDM), j, n, p standards
For MIMO measurements (IEEE 802.11 ac, ax, n, be), the results are grouped by
stream, symbol and carrier.
Figure 3-9: Bitstream result display for IEEE 802.11n MIMO measurements
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