Rohde & Schwarz VSE-K100, VSE-K104, VSE-K102 User Manual
R&S®VSE-K10x (LTE Uplink)
LTE Uplink Measurements
User Manual
(;Úçï2)
1176899702
User Manual
Version 06
This manual applies to the following software, version 1.50 and later:
●
R&S®VSE Enterprise Edition base software (1320.7500.xx / 1320.7951.xx)
●
R&S®VSE Basic Edition base software (1345.1011.06)
This manual describes functionality of the following R&S®VSE options:
●
R&S®VSE-K100 LTE FDD Measurement Application (1320.7545K02)
●
R&S®VSE-K102 LTE Advanced and MIMO Measurement Application (1320.7551K02)
●
R&S®VSE-K104 LTE FDD Measurement Application (1320.7568K02)
© 2018 Rohde & Schwarz GmbH & Co. KG
Mühldorfstr. 15, 81671 München, Germany
Phone: +49 89 41 29 - 0
Fax: +49 89 41 29 12 164
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.
1176.8997.02 | Version 06 | R&S®VSE-K10x (LTE Uplink)
Throughout this manual, products from Rohde & Schwarz are indicated without the ® symbol , e.g. R&S®VSE is indicated as
R&S VSE.
R&S®VSE-K10x (LTE Uplink)
Contents
1 Preface.................................................................................................... 7
1.1 About this Manual......................................................................................................... 7
1.2 Documentation Overview............................................................................................. 7
1.3 Typographical Conventions......................................................................................... 8
2 Welcome to the LTE measurement application.................................10
2.1 Starting the LTE measurement application.............................................................. 10
2.2 Understanding the Display Information.................................................................... 11
3 Measurement Basics........................................................................... 13
3.1 Symbols and Variables...............................................................................................13
3.2 Overview...................................................................................................................... 14
Contents
3.3 The LTE Uplink Analysis Measurement Application................................................14
3.3.1 Synchronization.............................................................................................................15
3.3.2 Analysis.........................................................................................................................16
3.4 Performing Time Alignment Measurements.............................................................18
3.5 SRS EVM Calculation..................................................................................................19
4 Measurements and Result Displays...................................................21
4.1 Selecting Measurements............................................................................................ 21
4.2 Selecting Result Displays.......................................................................................... 21
4.3 Performing Measurements.........................................................................................22
4.4 I/Q Measurements....................................................................................................... 23
4.5 Time Alignment Error Measurements....................................................................... 37
5 Configuration........................................................................................40
5.1 Configuration Overview..............................................................................................40
5.2 Configuring I/Q Measurements..................................................................................42
5.2.1 Defining Signal Characteristics..................................................................................... 43
5.2.2 Configuring MIMO Setups.............................................................................................49
5.2.3 Configuring Subframes................................................................................................. 51
5.2.4 Defining Global Signal Characteristics..........................................................................57
5.2.5 Configuring the Demodulation Reference Signal.......................................................... 58
5.2.6 Configuring the Sounding Reference Signal................................................................. 60
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5.2.7 Defining the PUSCH Structure......................................................................................64
5.2.8 Defining the PUCCH Structure......................................................................................65
5.2.9 Defining the PRACH Structure......................................................................................68
5.2.10 Selecting the Input and Output Source......................................................................... 70
5.2.11 Defining the Frequency................................................................................................. 74
5.2.12 Defining Level Characteristics.......................................................................................75
5.2.13 Configuring the Data Capture....................................................................................... 77
5.2.14 Triggering Measurements............................................................................................. 78
5.2.15 Tracking.........................................................................................................................80
5.2.16 Signal Demodulation..................................................................................................... 81
5.3 Configuring Time Alignment Error Measurements..................................................83
6 Analysis................................................................................................ 84
Contents
6.1 Configuring Tables / Numerical Results................................................................... 84
6.2 Exporting Measurement Results............................................................................... 84
6.3 Evaluation Range........................................................................................................ 85
6.4 Scale.............................................................................................................................88
6.5 Result Settings............................................................................................................ 88
6.6 Markers........................................................................................................................ 90
7 Remote Control.................................................................................... 92
7.1 Common Suffixes........................................................................................................92
7.2 Introduction................................................................................................................. 93
7.2.1 Conventions used in Descriptions.................................................................................93
7.2.2 Long and Short Form.................................................................................................... 94
7.2.3 Numeric Suffixes........................................................................................................... 94
7.2.4 Optional Keywords........................................................................................................ 95
7.2.5 Alternative Keywords.................................................................................................... 95
7.2.6 SCPI Parameters.......................................................................................................... 95
7.3 Remote Commands to Select the LTE Application.................................................. 98
7.4 Configuring the Screen Layout..................................................................................98
7.4.1 General Layout..............................................................................................................98
7.4.2 Configuring the Layout over all Channels..................................................................... 99
7.4.3 Configuring the Layout of a Channel...........................................................................103
7.5 Remote Commands to Read Trace Data.................................................................109
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7.5.1 Using the TRACe[:DATA] Command...........................................................................109
7.5.2 Remote Commands to Read Measurement Results...................................................120
7.6 Remote Commands to Read Numeric Results.......................................................121
7.6.1 Frame Results.............................................................................................................121
7.6.2 Result for Selection..................................................................................................... 125
7.6.3 Time Alignment Error.................................................................................................. 130
7.6.4 Marker Table............................................................................................................... 131
7.6.5 CCDF Table.................................................................................................................134
7.7 Remote Commands to Read Limit Check Results.................................................136
7.7.1 Checking Limits for Numerical Result Display............................................................ 136
7.8 Remote Commands to Configure the Application................................................. 145
7.8.1 General Configuration................................................................................................. 145
7.8.2 Configuring I/Q Measurements................................................................................... 146
Contents
7.8.3 Configuring Time Alignment Measurements............................................................... 196
7.9 Analysis..................................................................................................................... 197
7.9.1 Evaluation Range........................................................................................................197
7.9.2 Y-Axis Scale................................................................................................................ 201
7.9.3 Result Settings............................................................................................................ 202
7.9.4 Markers....................................................................................................................... 204
Annex.................................................................................................. 211
A Annex: Reference...............................................................................211
A.1 Menu Reference.........................................................................................................211
A.1.1 Common R&S VSE Menus..........................................................................................211
A.1.2 LTE Measurement Menus........................................................................................... 213
A.2 Reference of Toolbar Functions.............................................................................. 215
List of Commands..............................................................................219
Index....................................................................................................225
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Contents
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1 Preface
1.1 About this Manual
This User Manual describes information specific to measurements in the LTE measurement application. All other applications are described in the corresponding appli-
cation manuals.
The main focus in this manual is on the measurement results and the tasks required to
obtain them. The following topics are included:
●
Welcome to the R&S VSE
Introduction to and getting familiar with the software
●
Measurements and Results
Descriptions of the measurement types available in the R&S VSE software
●
Controlling Instruments and Capturing I/Q Data
Methods of data acquisition and description of basic instrument control functions
●
LTE Measurements
Description of the settings and functions provided to analyze results with the software and the corresponding remote control commands
●
Remote Commands for LTE Measurements
Remote commands required to configure and perform measurements in a remote
environment, sorted by tasks
Remote commands required to set up the environment and to perform common
tasks in the software, sorted by tasks
Programming examples demonstrate the use of many commands and can usually
be executed directly for test purposes
●
List of Commands
Alphabetical list of all remote commands described in the manual
●
Index
Preface
Documentation Overview
1.2 Documentation Overview
The user documentation for the R&S VSE consists of the following parts:
●
"Getting Started" printed manual
●
Online Help system in the software
●
CD-ROM including the following documentation:
– Getting Started
– User Manuals for base software and options
– Service Manual
– Release Notes
– Data sheet and product brochures
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Online Help
The Online Help is embedded in the software. It offers quick, context-sensitive access
to the complete information needed for operation and programming. Online help is
available using the icon on the toolbar of the R&S VSE.
Getting Started
This manual is delivered with the software in printed form and in PDF format on the
CD. It provides the information needed to set up and start working with the software.
Basic operations and handling are described. Safety information is also included.
User Manuals
User manuals are provided for the base software and each additional (software)
option.
The user manuals are available in PDF format - in printable form - on the CD-ROM
delivered with the software. In the user manuals, all software functions are described in
detail. Furthermore, they provide a complete description of the remote control commands with programming examples.
Preface
Typographical Conventions
The user manual for the base software provides basic information on operating the
R&S VSE in general, and the I/Q Analyzer application in particular. Furthermore, the
software functions that enhance the basic functionality for various applications are
described here. An introduction to remote control is provided, as well as information on
troubleshooting.
In the individual application manuals, the specific software functions of the application
are described in detail. For additional information on default settings and parameters,
refer to the data sheets. Basic information on operating the R&S VSE is not included in
the application manuals.
Release Notes
The release notes describe the installation of the software, new and modified functions,
eliminated problems, and last minute changes to the documentation. The corresponding software version is indicated on the title page of the release notes.
Application Notes
Application notes, application cards, white papers and educational notes are further
publications that provide more comprehensive descriptions and background information. The latest versions are available for download from the Rohde & Schwarz website, at www.rohde-schwarz.com/appnote/.
1.3 Typographical Conventions
The following text markers are used throughout this documentation:
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Convention Description
Preface
Typographical Conventions
"Graphical user interface elements"
[Keys] Key and knob names are enclosed by square brackets.
File names, commands,
program code
Input Input to be entered by the user is displayed in italics.
Links Links that you can click are displayed in blue font.
"References" References to other parts of the documentation are enclosed by quota-
All names of graphical user interface elements on the screen, such as
dialog boxes, menus, options, buttons, and softkeys are enclosed by
quotation marks.
File names, commands, coding samples and screen output are distinguished by their font.
tion marks.
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2 Welcome to the LTE measurement applica-
tion
The LTE measurement application is a firmware application that adds functionality to
perform measurements on LTE signals according to the 3GPP standard to the
R&S VSE.
This user manual contains a description of the functionality that the application provides, including remote control operation. Functions that are not discussed in this manual are the same as in the Spectrum application and are described in the R&S VSE
User Manual. The latest versions of the manuals are available for download at the
product homepage.
http://www2.rohde-schwarz.com/product/vse.html.
● Starting the LTE measurement application............................................................. 10
● Understanding the Display Information................................................................... 11
Welcome to the LTE measurement application
Starting the LTE measurement application
2.1 Starting the LTE measurement application
The LTE measurement application adds a new application to the R&S VSE.
To open the LTE application
1.
Select the "Add Channel" function in the Sequence tool window.
A dialog box opens that contains all operating modes and applications currently
available in your R&S VSE.
2. Select the "LTE" item.
The R&S VSE opens a new measurement channel for the LTE application.
The application is started with the default settings. It can be configured in the "Overview" dialog box, which is displayed when you select the "Overview" softkey from the
"Meas Setup" menu.
For more information see Chapter 5, "Configuration", on page 40.
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2.2 Understanding the Display Information
The following figure shows a measurement diagram during analyzer operation. All different information areas are labeled. They are explained in more detail in the following
sections.
1 2 3 4 5
Welcome to the LTE measurement application
Understanding the Display Information
1 = Window title bar with information about the diagram and its traces
2 = Channel bar with measurement settings
3 = Diagram area
4 = Diagram footer with information about the contents of the diagram
5 = Color code for windows of the same channel (here: red)
Channel bar information
In the LTE measurement application, the R&S VSE shows the following settings:
Table 2-1: Information displayed in the channel bar in the LTE measurement application
Ref Level Reference level
Att Mechanical and electronic RF attenuation
Freq Frequency
Mode LTE standard
MIMO Number of Tx and Rx antennas in the measurement setup
Capture Time Signal length that has been captured
Frame Count Number of frames that have been captured
Selected Slot Slot considered in the signal analysis
Selected Subframe Subframe considered in the signal analysis
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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 VSE Getting Started manual.
Window title bar information
The information in the window title bar depends on the result display.
The "Constellation Diagram", for example, shows the number of points that have been
measured.
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.
Regarding the synchronization state, the application shows the following labels.
●
Sync OK
The synchronization was successful. The status bar is green.
●
Sync Failed
The synchronization was not successful. The status bar is red.
There can be three different synchronization errors.
– Sync Failed (Cyclic Prefix): The cyclic prefix correlation failed.
– Sync Failed (P-SYNC): The P-SYNC correlation failed.
– Sync Failed (S-SYNC): The S-SYNC correlation failed.
Welcome to the LTE measurement application
Understanding the Display Information
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3 Measurement Basics
● Symbols and Variables............................................................................................13
● Overview................................................................................................................. 14
● The LTE Uplink Analysis Measurement Application................................................14
● Performing Time Alignment Measurements............................................................18
● SRS EVM Calculation............................................................................................. 19
3.1 Symbols and Variables
The following chapters use various symbols and variables in the equations that the
measurements are based on. The table below explains these symbols for a better
understanding of the measurement principles.
Measurement Basics
Symbols and Variables
a
l,kâl,k
A
l,k
Δf, Δ
coarse
Δf
res
ζ
H
l,k, l,k
i time index
î
, î
coarse
fine
k subcarrier index
l SC-FDMA symbol index
N
DS
N
FFT
N
g
N
s
N
TX
data symbol (actual, decided)
data symbol after DFT-precoding
carrier frequency offset between transmitter and
receiver (actual, coarse estimate)
residual carrier frequency offset
relative sampling frequency offset
channel transfer function (actual, estimate)
timing estimate (coarse, fine)
number of SC-FDMA data symbols
length of FFT
number of samples in cyclic prefix (guard interval)
number of Nyquist samples
number of allocated subcarriers
N
k,l
n index of modulated QAM symbol before DFT pre-
Φ
l
r
i
R'
k,l
noise sample
coding
common phase error
received sample in the time domain
uncompensated received sample in the frequency
domain
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Measurement Basics
The LTE Uplink Analysis Measurement Application
r
n,l
T duration of the useful part of an SC-FDMA symbol
T
g
T
s
3.2 Overview
The digital signal processing (DSP) involves several stages until the software can present results like the EVM.
The contents of this chapter are structured like the DSP.
equalized received symbols of measurement path
after IDFT
duration of the guard interval
total duration of SC-FDMA symbol
3.3 The LTE Uplink Analysis Measurement Application
The block diagram in Figure 3-1 shows the general structure of the LTE uplink measurement application from the capture buffer containing the I/Q data up to the actual
analysis block.
After synchronization a fully compensated signal is produced in the reference path
(purple) which is subsequently passed to the equalizer. An IDFT of the equalized symbols yields observations for the QAM transmit symbols a
mates â
are obtained via hard decision. Likewise a user defined compensation as
n,l
well as equalization is carried out in the measurement path (cyan) and after an IDFT
the observations of the QAM transmit symbols are provided. Accordingly, the measurement path might still contain impairments which are compensated in the reference
path. The symbols of both signal processing paths form the basis for the analysis.
from which the data esti-
n.l
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Measurement Basics
The LTE Uplink Analysis Measurement Application
Figure 3-1: Block diagram for the LTE UL measurement application
3.3.1 Synchronization
In a first step the areas of sufficient power are identified within the captured I/Q data
stream which consists of the receive samples ri. For each area of sufficient power, the
analyzer synchronizes on subframes of the uplink generic frame structure [3]. After this
coarse timing estimation, the fractional part as well as the integer part of the carrier frequency offset (CFO) are estimated and compensated. In order to obtain an OFDM
demodulation via FFT of length N
lished which refines the coarse timing estimate.
A phase tracking based on the reference SC-FDMA symbols is performed in the frequency domain. The corresponding tracking estimation block provides estimates for
●
the relative sampling frequency offset ζ
●
the residual carrier frequency offset Δf
●
the common phase error Φ
According to references [7] and [8], the uncompensated samples R'
ded domain can be stated as
that is not corrupted by ISI, a fine timing is estab-
FFT
res
l
in the DFT-preco-
k,l
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lk
lTfNNjlkNNjj
lklklk
NeeeHAR
CFOres
resFFTS
SFO
FFTS
CPE
l
,
22
,,
'
,
.
2
,
,,
,
ˆ
~
ln
lnln
kl
aE
ar
EVM
lnlnln
arEVM
,,,
ˆ
~
Equation 3-1:
with
●
the DFT precoded data symbol A
●
the channel transfer function H
●
the number of Nyquist samples NS within the total duration TS,
●
the duration of the useful part of the SC-FDMA symbol T=TS-T
●
the independent and Gaussian distributed noise sample N
Within one SC-FDMA symbol, both the CPE and the residual CFO cause the same
phase rotation for each subcarrier, while the rotation due to the SFO depends linearly
on the subcarrier index. A linear phase increase in symbol direction can be observed
for the residual CFO as well as for the SFO.
Measurement Basics
The LTE Uplink Analysis Measurement Application
on subcarrier k at SC-FDMA symbol l,
k,l
,
k,l
g
k,l
The results of the tracking estimation block are used to compensate the samples R'
completely in the reference path and according to the user settings in the measure-
ment path. Thus the signal impairments that are of interest to the user are left uncompensated in the measurement path.
After having decoded the data symbols in the reference path, an additional data-aided
phase tracking can be utilized to refine the common phase error estimation.
3.3.2 Analysis
The analysis block of the EUTRA/LTE uplink measurement application allows to compute a variety of measurement variables.
EVM
The most important variable is the error vector magnitude which is defined as
Equation 3-2:
for QAM symbol n before precoding and SC-FDMA symbol l. Since the normalized
average power of all possible constellations is 1, the equation can be simplified to
k,l
Equation 3-3:
The average EVM of all data subcarriers is then
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101
0
2
,
1
LB TX
NlN
n
ln
TXDS
data
EVM
NN
EVM
tsjQtsItr
|1|balancegain modulator Q
}1arg{mismatch quadrature Q
S
RB
Tt
Nc
c
RBS
RBabsolute
RBrelative
ftY
NT
Emissions
Emissions
112
2
,
1
Equation 3-4:
for NDS SC-FDMA data symbols and the NTX allocated subcarriers.
I/Q imbalance
The I/Q imbalance contained in the continuous received signal r(t) can be written as
Equation 3-5:
where s(t) is the transmit signal and I and Q are the weighting factors describing the
I/Q imbalance. We define that I:=1 and Q:=1+ΔQ.
The I/Q imbalance estimation makes it possible to evaluate the
Measurement Basics
The LTE Uplink Analysis Measurement Application
Equation 3-6:
and the
Equation 3-7:
based on the complex-valued estimate .
Basic in-band emissions measurement
The in-band emissions are a measure of the interference falling into the non-allocated
resources blocks.
The relative in-band emissions are given by
Equation 3-8:
where TS is a set |TS| of SC-FDMA symbols with the considered modulation scheme
being active within the measurement period, ΔRB is the starting frequency offset
between the allocated RB and the measured non-allocated RB (e.g. ΔRB=1 or ΔRB=-1
for the first adjacent RB), c is the lower edge of the allocated BW, and Y(t,f) is the fre-
quency domain signal evaluated for in-band emissions. NRB is the number of allocated
RBs .
The basic in-band emissions measurement interval is defined over one slot in the time
domain.
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Other measurement variables
Without going into detail, the EUTRA/LTE uplink measurement application additionally
provides the following results:
●
Total power
●
Constellation diagram
●
Group delay
●
I/Q offset
●
Crest factor
●
Spectral flatness
3.4 Performing Time Alignment Measurements
The measurement application allows you to perform time alignment measurements
between different antennas.
Measurement Basics
Performing Time Alignment Measurements
The measurement supports setups of up to two Tx antennas.
The result of the measurement is the time alignment error. The time alignment error is
the time offset between a reference antenna (for example antenna 1) and another
antenna.
The time alignment error results are summarized in the corresponding result display.
A schematic description of the results is provided in Figure 3-2.
Tx Antenna 1 (Reference)
Time
Tx Antenna 2
LTE Frame Start Indicator
Figure 3-2: Time Alignment Error (2 Tx antennas)
Time Alignment Error
Δ2,1
Time
Test setup
Successful Time Alignment measurements require a correct test setup.
A typical test setup is shown in Figure 3-3.
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Tx Ant 1
DUT
Tx Ant 2
Figure 3-3: Hardware setup
For best measurement result accuracy, it is recommended to use cables of the same
length and identical combiners as adders.
In the application, make sure to correctly apply the following settings.
●
Select a reference antenna in the MIMO Configuration dialog box (not "All")
●
Select more than one antenna in the MIMO Configuration dialog box
●
Select Codeword-to-Layer mapping "2/1" or "2/2"
●
Select an Auto Demodulation different to "Subframe Configuration & DMRS"
●
The transmit signals of all available Tx antennas have to be added together
Measurement Basics
SRS EVM Calculation
FSx
+
3.5 SRS EVM Calculation
In order to calculate an accurate EVM, a channel estimation needs to be done prior to
the EVM calculation. However, the channel estimation requires a minimum of two
resource elements containing reference symbols on a subcarrier. Depending on the
current Channel Estimation Range setting, this means that either at least two reference
symbols ("Pilot Only") or one reference symbol and at least one data symbol ("Pilot
and Payload") need to be available on the subcarrier the EVM is to be measured.
For PUSCH, PUCCH and PRACH regions, these conditions are normally fulfilled
because the DMRS (= Demodulation Reference Signal) is already included. However,
the SRS may also be located on subcarriers which do not occupy any other reference
symbols (see Figure 3-4).
Figure 3-4: No EVM can be measured for the SRS
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In this case it is not reasonable to calculate an EVM and no SRS EVM value will be
displayed for the corresponding subframe.
If the SRS subcarriers contain two DMRS symbols (or one DMRS and one PUSCH for
"Pilot and Payload" channel estimation range) the SRS EVM can be measured (see
Figure 3-5).
Measurement Basics
SRS EVM Calculation
Figure 3-5: The EVM of the complete SRS can be measured
The SRS allocation might cover subcarriers which partly fulfill the conditions mentioned
above and partly do not. In this case the EVM value given in the Allocation Summary
will be calculated based only on the subcarriers which fulfill the above requirements
(see Figure 3-6).
Figure 3-6: The EVM for parts of the SRS can be measured
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4 Measurements and Result Displays
The LTE measurement application measures and analyzes various aspects of an LTE
signal.
It features several measurements and result displays. Measurements represent different ways of processing the captured data during the digital signal processing. Result
displays are different representations of the measurement results. They can be diagrams that show the results as a graph or tables that show the results as numbers.
● Selecting Measurements.........................................................................................21
● Selecting Result Displays........................................................................................21
● Performing Measurements......................................................................................22
● I/Q Measurements...................................................................................................23
● Time Alignment Error Measurements..................................................................... 37
4.1 Selecting Measurements
Measurements and Result Displays
Selecting Result Displays
► Select the "Select Meas" menu item from the "Meas Setup" menu.
The application opens a dialog box that contains several buttons.
Each button represents a set of result displays that thematically belong together
and that have a particular display configuration. If these predefined display configurations do not suit your requirements, you can add or remove result displays as
you like. For more information about selecting result displays, see Chapter 4.2,
"Selecting Result Displays", on page 21.
Depending on the button you select, the application changes the way the R&S VSE
captures and processes the raw signal data.
●
When you select "EVM", the application processes the I/Q data of the signal. For
more information on available I/Q result displays, see Chapter 4.4, "I/Q Measure-
ments", on page 23.
When you select one of the result displays available for I/Q measurements, you
can combine the result displays available for I/Q measurements in any way.
Remote command:
CONFigure[:LTE]:MEASurement on page 145
4.2 Selecting Result Displays
► Select the "New Window" menu item from the "Window" menu or select a new win-
dow with the icon in the toolbar. Depending on the number of LTE channels you
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are currently using, there is a submenu that contains all available result displays for
each LTE channel.
In the default state of the application, it shows several conventional result displays.
●
Capture Buffer
●
EVM vs Carrier
●
Power Spectrum
●
Result Summary
●
Constellation Diagram
From that predefined state, add and remove result displays to the channels as you like
from the "Window" menu.
Remote command:
LAYout:ADD[:WINDow]? on page 103
MIMO measurements
When you capture more than one data stream, each result display is made up out of
several tabs.
The first tab shows the results for all data streams. The other tabs show the results for
each individual data stream. By default, the tabs are coupled to one another - if you
select a particular data stream in one display, the application also selects this data
stream in the other result displays (see Subwindow Coupling).
The number of tabs depends on the number of data streams.
Measurements and Result Displays
Performing Measurements
4.3 Performing Measurements
By default, the application measures the signal continuously. In "Continuous Sweep"
mode, the R&S VSE captures and analyzes the data again and again.
●
For I/Q measurements, the amount of captured data depends on the capture time.
●
For frequency sweep measurement, the amount of captured data depends on the
sweep time.
In "Single Sweep" mode, the R&S VSE stops measuring after it has captured the data
once. The amount of data again depends on the capture time.
You can also repeat a measurement based on the data that has already been captured
with the "Refresh" function. Repeating a measurement with the same data can be useful, for example, if you want to apply different modulation settings to the same I/Q data.
For more information, see the documentation of the R&S VSE.
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4.4 I/Q Measurements
Access: "Overview" > "Select Measurement" > "EVM/Frequency Err/Power"
You can select the result displays from the evaluation bar and arrange them as you like
with the SmartGrid functionality.
Capture Buffer...............................................................................................................23
EVM vs Carrier..............................................................................................................24
EVM vs Symbol.............................................................................................................25
EVM vs Subframe......................................................................................................... 26
Power Spectrum............................................................................................................26
Inband Emission............................................................................................................26
Spectrum Flatness........................................................................................................ 27
Spectrum Flatness SRS................................................................................................28
Group Delay..................................................................................................................28
Spectrum Flatness Difference.......................................................................................29
Constellation Diagram...................................................................................................29
CCDF............................................................................................................................ 30
Allocation Summary...................................................................................................... 31
Bit Stream..................................................................................................................... 31
EVM vs Symbol x Carrier..............................................................................................32
Power vs Symbol x Carrier............................................................................................33
Result Summary............................................................................................................33
Marker Table ................................................................................................................ 36
Measurements and Result Displays
I/Q Measurements
Capture Buffer
The "Capture Buffer" shows the complete range of captured data for the last data capture.
The x-axis represents time. The maximum value of the x-axis is equal to the Capture
Time.
The y-axis represents the amplitude of the captured I/Q data in dBm (for RF input).
Figure 4-1: Capture buffer without zoom
A green vertical line at the beginning of the green bar in the capture buffer represents
the subframe start. The diagram also contains the "Start Offset" value. This value is the
time difference between the subframe start and capture buffer start.
When you zoom into the diagram, you will see that the bar is interrupted at certain
positions. Each small bar indicates the useful parts of the OFDM symbol.
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Figure 4-2: Capture buffer after a zoom has been applied
Remote command:
Selecting the result display: LAY:ADD ? '1',LEFT,CBUF
Querying results:
TRACe:DATA?
TRACe<n>[:DATA]:X? on page 119
Querying the subframe start offset: FETCh[:CC<cc>]:SUMMary:TFRame?
on page 129
Measurements and Result Displays
I/Q Measurements
EVM vs Carrier
The "EVM vs Carrier" result display shows the error vector magnitude (EVM) of the
subcarriers. With the help of a marker, you can use it as a debugging technique to
identify any subcarriers whose EVM is too high.
The results are based on an average EVM that is calculated over the resource elements for each subcarrier. This average subcarrier EVM is determined for each analyzed slot in the capture buffer.
If you analyze all slots, the result display contains three traces.
●
Average EVM
This trace shows the subcarrier EVM, averaged over all slots.
●
Minimum EVM
This trace shows the lowest (average) subcarrier EVM that has been found over
the analyzed slots.
●
Maximum EVM
This trace shows the highest (average) subcarrier EVM that has been found over
the analyzed slots.
If you select and analyze one slot only, the result display contains one trace that shows
the subcarrier EVM for that slot only. Average, minimum and maximum values in that
case are the same. For more information, see "Slot Selection" on page 86.
The x-axis represents the center frequencies of the subcarriers. The y-axis shows the
EVM in % or in dB, depending on the EVM Unit.
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Remote command:
Selecting the result display: LAY:ADD ? '1',LEFT,EVCA
Querying results:
TRACe:DATA?
TRACe<n>[:DATA]:X? on page 119
EVM vs Symbol
The "EVM vs Symbol" result display shows the error vector magnitude (EVM) of the
OFDM symbols. You can use it as a debugging technique to identify any symbols
whose EVM is too high.
The results are based on an average EVM that is calculated over all subcarriers that
are part of a certain OFDM symbol. This average OFDM symbol EVM is determined for
all OFDM symbols in each analyzed slot.
The x-axis represents the OFDM symbols, with each symbol represented by a dot on
the line. Any missing connections from one dot to another mean that the R&S VSE
could not determine the EVM for that symbol.
The number of displayed symbols depends on the subframe selection and the length of
the cyclic prefix.
For TDD signals, the result display does not show OFDM symbols that are not part of
the measured link direction.
On the y-axis, the EVM is plotted either in % or in dB, depending on the EVM Unit.
Measurements and Result Displays
I/Q Measurements
Remote command:
Selecting the result display: LAY:ADD ? '1',LEFT,EVSY
Querying results:
TRACe:DATA?
TRACe<n>[:DATA]:X? on page 119
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EVM vs Subframe
The "EVM vs Subframe" result display shows the Error Vector Magnitude (EVM) for
each subframe. You can use it as a debugging technique to identify a subframe whose
EVM is too high.
The result is an average over all subcarriers and symbols of a specific subframe.
The x-axis represents the subframes, with the number of displayed subframes being
10.
On the y-axis, the EVM is plotted either in % or in dB, depending on the EVM Unit.
Measurements and Result Displays
I/Q Measurements
Remote command:
Selecting the result display: LAY:ADD ? '1',LEFT,EVSU
Querying results:
TRACe:DATA?
TRACe<n>[:DATA]:X? on page 119
Power Spectrum
The "Power Spectrum" shows the power density of the complete capture buffer in
dBm/Hz.
The displayed bandwidth depends on the selected channel bandwidth.
The x-axis represents the frequency. On the y-axis, the power level is plotted.
Remote command:
Selecting the result display: LAY:ADD ? '1',LEFT,PSPE
Querying results:
TRACe:DATA?
TRACe<n>[:DATA]:X? on page 119
Inband Emission
The "Inband Emission" result display shows the relative power of the unused resource
blocks (yellow trace) and the inband emission limit lines (red trace) specified in 3GPP
TS36.101.
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The measurement is evaluated over the currently selected slot in the currently selected
subframe. The currently selected subframe depends on your selection. You have to
select a specific subframe and slot to get valid measurement results.
You can also display the inband emissions for the allocated resource block in addition
to the unused resource blocks when you select the Inband Emissions All result display.
Measurements and Result Displays
I/Q Measurements
Remote command:
Selecting the result display: LAY:ADD ? '1',LEFT,IE
Selecting the result display: LAY:ADD ? '1',LEFT,IEA
Querying results:
TRACe:DATA?
TRACe<n>[:DATA]:X? on page 119
Spectrum Flatness
The "Spectrum Flatness" result display shows the relative power offset caused by the
transmit channel.
The measurement is evaluated over the currently selected slot in the currently selected
subframe.
The currently selected subframe depends on your selection.
The x-axis represents the frequency. On the y-axis, the channel flatness is plotted in
dB.
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Note that the limit lines are only displayed if you match the Operating Band to the center frequency. Limits are defined for each operating band in the standard.
The shape of the limit line is different when "Extreme Conditions" on page 49 are on.
Remote command:
Selecting the result display: LAY:ADD ? '1',LEFT,SFL
Querying results:
TRACe:DATA?
TRACe<n>[:DATA]:X? on page 119
Spectrum Flatness SRS
The "Spectrum Flatness SRS" display shows the amplitude of the channel transfer
function based on the sounding reference signal.
The measurement is evaluated over the currently selected slot in the currently selected
subframe. The slot and subframe selection may be changed in the general settings.
Measurements and Result Displays
I/Q Measurements
Remote command:
Selecting the result display: LAY:ADD ? '1',LEFT,SFSR
Querying results:
TRACe:DATA?
TRACe<n>[:DATA]:X? on page 119
Group Delay
This "Group Delay" shows the group delay of each subcarrier.
The measurement is evaluated over the currently selected slot in the currently selected
subframe.
The currently selected subframe depends on your selection.
The x-axis represents the frequency. On the y-axis, the group delay is plotted in ns.
Remote command:
Selecting the result display: LAY:ADD ? '1',LEFT,GDEL
Querying results:
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TRACe:DATA?
TRACe<n>[:DATA]:X? on page 119
Spectrum Flatness Difference
The "Spectrum Flatness Difference" result display shows the level difference in the
spectrum flatness result between two adjacent physical subcarriers.
The measurement is evaluated over the currently selected slot in the currently selected
subframe.
The currently selected subframe depends on your selection.
The x-axis represents the frequency. On the y-axis, the power is plotted in dB.
Measurements and Result Displays
I/Q Measurements
Remote command:
Selecting the result display: LAY:ADD ? '1',LEFT,SFD
Querying results:
TRACe:DATA?
TRACe<n>[:DATA]:X? on page 119
Constellation Diagram
The "Constellation Diagram" shows the in-phase and quadrature phase results and is
an indicator of the quality of the modulation of the signal.
In the default state, the result display evaluates the full range of the measured input
data.
Each color represents a modulation type.
●
●
●
●
●
●
●
You can filter the results by changing the evaluation range.
: RBPSK
: MIXTURE
: QPSK
: 16QAM
: 64QAM
: 256QAM
: PSK (CAZAC)
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The constellation diagram also contains information about the current evaluation
range. It also shows the number of points that are displayed in the diagram.
Remote command:
Selecting the result display: LAY:ADD ? '1',LEFT,CONS
Querying results: TRACe:DATA?
CCDF
The "Complementary Cumulative Distribution Function (CCDF)" shows the probability
of an amplitude exceeding the mean power. For the measurement, the complete capture buffer is used.
The x-axis represents the power relative to the measured mean power. On the y-axis,
the probability is plotted in %.
Measurements and Result Displays
I/Q Measurements
In addition to the diagram, the results for the CCDF measurement are summarized in
the CCDF table.
Mean Mean power
Peak Peak power
Crest Crest factor (peak power – mean power)
10 % Level values over 10 % above mean power
1 % Level values over 1 % above mean power
0.1 % Level values over 0.1 % above mean power
0.01 % Level values over 0.01 % above mean power
Remote command:
Selecting the result display: LAY:ADD ? '1',LEFT,CCDF
Querying results: TRACe:DATA?
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