Rohde&Schwarz R&S®SMW200A OFDM user manual User Manual
R&S®SMW-K114
OFDM Signal Generation
User Manual
(;ÛÌ^2)
1177624602
Version 15
This document describes the following software options:
●
R&S®SMW-K114 OFDM Signal Generation (1414.1985.xx)
This manual describes firmware version FW 5.00.166.xx and later of the R&S®SMW200A.
© 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.
1177.6246.02 | Version 15 | R&S®SMW-K114
The following abbreviations are used throughout this manual: R&S®SMW200A is abbreviated as R&S SMW, R&S®WinIQSIM2 is
abbreviated as R&S WinIQSIM2; the license types 02/03/07/11/13/16/12 are abbreviated as xx.
R&S®SMW-K114
1 Welcome to the OFDM Signal Generation option............................... 5
1.1 Accessing the OFDM Signal Generation dialog.........................................................6
1.2 What's new.....................................................................................................................6
1.3 Documentation overview..............................................................................................6
1.3.1 Getting started manual....................................................................................................6
1.3.2 User manuals and help................................................................................................... 6
1.3.3 Tutorials...........................................................................................................................7
1.3.4 Service manual............................................................................................................... 7
1.3.5 Instrument security procedures.......................................................................................7
1.3.6 Printed safety instructions............................................................................................... 7
1.3.7 Data sheets and brochures............................................................................................. 7
Contents
Contents
1.3.8 Release notes and open source acknowledgment (OSA).............................................. 8
1.3.9 Application notes, application cards, white papers, etc...................................................8
1.4 Scope............................................................................................................................. 8
1.5 Notes on screenshots...................................................................................................8
2 About OFDM Signal Generation option............................................... 9
2.1 Required options...........................................................................................................9
2.2 Overview of modulation schemes............................................................................... 9
2.2.1 OFDM..............................................................................................................................9
2.2.2 f-OFDM......................................................................................................................... 10
2.2.3 GFDM............................................................................................................................10
2.2.4 UFMC............................................................................................................................ 11
2.2.5 FBMC............................................................................................................................ 12
2.2.6 Filtering......................................................................................................................... 13
2.3 Supported multiple access schemes........................................................................ 18
2.4 Physical layer parameterization................................................................................ 21
2.5
Generating configuration files for R&S®VSE-K96....................................................22
3 OFDM Signal Generation configuration and settings.......................24
3.1 General settings.......................................................................................................... 24
3.2 General settings.......................................................................................................... 27
3.2.1 Physical settings........................................................................................................... 27
3User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
3.2.2 Filter settings.................................................................................................................33
3.2.3 Modulation configuration settings..................................................................................35
3.3 Allocation settings...................................................................................................... 37
3.3.1 User settings................................................................................................................. 38
3.3.2 Allocations settings....................................................................................................... 39
3.3.3 SCMA settings.............................................................................................................. 44
3.3.4 Time plan.......................................................................................................................46
3.4 Trigger settings........................................................................................................... 48
3.5 Marker settings............................................................................................................53
3.6 Clock settings..............................................................................................................54
3.7 Local and global connectors settings.......................................................................56
4 Remote-control commands.................................................................57
Contents
4.1 General commands.....................................................................................................58
4.2 Physical settings commands.....................................................................................61
4.3 Filter commands......................................................................................................... 65
4.4 Modulation commands............................................................................................... 68
4.5 User commands.......................................................................................................... 70
4.6 Allocation commands.................................................................................................71
4.7 SCMA commands........................................................................................................78
4.8 Trigger commands......................................................................................................80
4.9 Marker commands...................................................................................................... 86
4.10 Clock commands........................................................................................................ 87
Annex.................................................................................................... 89
A XML settings file...................................................................................89
Glossary: List of terms and abbreviations........................................ 92
Glossary: Specifications, references and further information........ 94
List of commands................................................................................ 95
Index......................................................................................................97
4User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
1 Welcome to the OFDM Signal Generation
Welcome to the OFDM Signal Generation option
option
The R&S SMW-K114 is a firmware application that adds functionality to generate:
●
User-defined OFDM signals
●
Pre-release 5G signals in accordance with the 5GNOW project specification
5GNOW D3.x.
With the provided settings, you can generate any of the specified waveform types and
parameterize the signals. For example, you can select the pulse-shaping filters, the
subcarrier spacing and the number of carriers. Moreover, you can set the used modulation and data content and enable preamble and cyclic prefix generation. Configuration of the sparse code multiple access (SCMA) settings is supported, too.
The generated signal is suitable for testing of components or receivers with userdefined OFDM signals or realistic pre-5G physical layer signals.
The R&S SMW-K114 key features are:
●
Support of GFDM, UFMC, FBMC, f-OFDM and OFDM waveforms
●
Support of the proposed filter types
●
Flexible resource allocation, independent of the frame-type structure
●
Flexibly switching between different modulation formats, filters, symbol rates
●
Support of multiple access schemes such as SCMA
●
Optional use of a cyclic prefix or a preamble
●
Internal signal generator solution, no need for external PC
●
For f-OFDM and OFDM modulations, automatic generation of configuration file for
upload in the R&S®VSE-K96.
●
Optional discrete Fourier transformation spread OFDM (DFT-s-OFDM) for data
allocations
This user manual contains a description of the functionality that the application provides, including remote control operation.
All functions not discussed in this manual are the same as in the base unit and are
described in the R&S SMW user manual. The latest version is available at:
www.rohde-schwarz.com/manual/SMW200A
Installation
You can find detailed installation instructions in the delivery of the option or in the
R&S SMW service manual.
5User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
1.1 Accessing the OFDM Signal Generation dialog
1.2 What's new
Welcome to the OFDM Signal Generation option
Documentation overview
To open the dialog with OFDM Signal Generation settings
► In the block diagram of the R&S SMW, select "Baseband > OFDM Signal Genera-
tion".
A dialog box opens that displays the provided general settings.
The signal generation is not started immediately. To start signal generation with the
default settings, select "State > On".
This manual describes firmware version FW 5.00.166.xx and later of the
R&S®SMW200A.
Compared to the previous version, it provides the new features listed below:
●
Discrete Fourier transform spread OFDM (DFT-s-OFDM) for precoding data allocations, see "DFT-S (skip non-data)" on page 31.
●
All allocated users are automatically active, the user state is removed, see Chap-
ter 3.3.1, "User settings", on page 38.
1.3 Documentation overview
This section provides an overview of the R&S SMW user documentation. Unless specified otherwise, you find the documents on the R&S SMW product page at:
www.rohde-schwarz.com/manual/smw200a
1.3.1 Getting started manual
Introduces the R&S SMW 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.
1.3.2 User manuals and help
Separate manuals for the base unit and the software options are provided for download:
●
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 com-
6User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
1.3.3 Tutorials
Welcome to the OFDM Signal Generation option
Documentation overview
mands with programming examples, and information on maintenance, instrument
interfaces and error messages. Includes the contents of the getting started manual.
●
Software option manual
Contains the description of the specific functions of an option. Basic information on
operating the R&S SMW is not included.
The contents of the user manuals are available as help in the R&S SMW. The help
offers quick, context-sensitive access to the complete information for the base unit and
the software options.
All user manuals are also available for download or for immediate display on the Internet.
The R&S SMW provides interactive examples and demonstrations on operating the
instrument in form of tutorials. A set of tutorials is available directly on the instrument.
1.3.4 Service manual
Describes the performance test for checking compliance with rated specifications, firmware update, troubleshooting, adjustments, installing options and maintenance.
The service manual is available for registered users on the global Rohde & Schwarz
information system (GLORIS):
https://gloris.rohde-schwarz.com
1.3.5 Instrument security procedures
Deals with security issues when working with the R&S SMW in secure areas. It is available for download on the Internet.
1.3.6 Printed safety instructions
Provides safety information in many languages. The printed document is delivered with
the product.
1.3.7 Data sheets and brochures
The data sheet contains the technical specifications of the R&S SMW. It also lists the
options 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/smw200a
7User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
1.3.8 Release notes and open source acknowledgment (OSA)
1.3.9 Application notes, application cards, white papers, etc.
Welcome to the OFDM Signal Generation option
Notes on screenshots
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/smw200a
These documents deal with special applications or background information on particular topics.
See www.rohde-schwarz.com/application/smw200a and www.rohde-schwarz.com/
manual/smw200a
1.4 Scope
Tasks (in manual or remote operation) that are also performed in the base unit in the
same way are not described here.
In particular, it includes:
●
Managing settings and data lists, like saving and loading settings, creating and
accessing data lists, or accessing files in a particular directory.
●
Information on regular trigger, marker and clock signals and filter settings, if appropriate.
●
General instrument configuration, such as checking the system configuration, configuring networks and remote operation
●
Using the common status registers
For a description of such tasks, see the R&S SMW user manual.
1.5 Notes on screenshots
When describing the functions of the product, we use sample screenshots. These
screenshots are meant to illustrate as many as possible of the provided functions and
possible interdependencies between parameters. The shown values may not represent
realistic usage scenarios.
The screenshots usually show a fully equipped product, that is: with all options installed. Thus, some functions shown in the screenshots may not be available in your particular product configuration.
8User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
2 About OFDM Signal Generation option
2.1 Required options
About OFDM Signal Generation option
Overview of modulation schemes
The OFDM Signal Generation option enables you to create waveforms according to
the following modulation schemes OFDM, f-OFDM, GFDM, UFMC and FBMC.
● Required options.......................................................................................................9
● Overview of modulation schemes............................................................................. 9
● Supported multiple access schemes.......................................................................18
● Physical layer parameterization.............................................................................. 21
●
Generating configuration files for R&S®VSE-K96................................................... 22
The basic equipment layout for generating OFDM signals includes the:
●
Standard or wideband Baseband Generator (R&S SMW-B10/-B9)
●
Baseband main module (R&S SMW-B13) or wideband baseband main module
(R&S SMW-B13XT)
●
Frequency option (e.g. R&S SMW-B1003)
●
Digital standard OFDM Signal Generation (R&S SMW-K114)
You can generate signals via play-back of waveform files at the signal generator. To
create the waveform file using R&S WinIQSIM2, you do not need a specific option.
To play back the waveform file at the signal generator, you have two options:
●
Install the R&S WinIQSIM2 option of the digital standard, e.g. R&S SMW-K255 for
playing LTE waveforms
●
If supported, install the real-time option of the digital standard, e.g. R&S SMW-K55
for playing LTE waveforms
For more information, see data sheet.
2.2 Overview of modulation schemes
The section gives a brief overview of the techniques and methods.
2.2.1 OFDM
The OFDM modulation is similar to the f-OFDM modulation. Other as in the f-OFDM,
the OFDM does not use sub-bands and there is no predefined filtering.
Related settings
●
Chapter 3.2.1, "Physical settings", on page 27
●
Chapter 3.2.3, "Modulation configuration settings", on page 35
9User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
2.2.2 f-OFDM
2.2.3 GFDM
About OFDM Signal Generation option
Overview of modulation schemes
The filtered OFDM (f-OFDM) modulation is a technique similar to the UFMC modulation. Other as in the UFMC, in the f-OFDM uses frame-based filtering.
The method is also known as Spectrum Filtered-OFDM.
Related settings
●
Chapter 3.2.1, "Physical settings", on page 27
●
Chapter 3.2.2, "Filter settings", on page 33
●
Chapter 3.2.3, "Modulation configuration settings", on page 35
The Generalized Frequency Division Multiplexing (GFDM) is a method in which the
data is processed on a two-dimensional block structure, both in time and in frequency
domain. The GFDM waveform is a non-orthogonal, asynchronous multi-carrier waveform.
In GFDM, subcarriers are independent single carriers; they can have different bandwidth, pulse shape and modulation. Each subcarrier is shaped with an individual transmit filter and then modulated with the subcarrier center frequency. The modulation is
performed on a per data block, where the data block size is a configurable value. The
commonly used filters are the root raised cosine filters.
The implementation principle is illustrated on Figure 2-1 ([1]).
Figure 2-1: Optimized GFDM transmitter model (from [1])
D = Matrix of input symbols, QPSK, BPSK, or QAM modulated
dk= Input vector
k = Number of active subcarrier
M = Number of symbols (block size)
N = FFT size
WM= FFT matrix
(L)
= Upsampling matrix with upsampling factor L
R
Γ
= Diagonal matrix containing the time samples of the filter pulse on its diagonal; the filtering is an ele-
ment wise multiplication in the frequency domain
(k)
= Permutation matrix that applies a frequency shift and moves the block input vectors to the position of
P
the subcarriers
H
= IFFT matrix that converts the signal from the frequency domain back to the time domain
W
NM
H
x =
W
NM∑k
(k)ΓR(L)
P
WMd
k
10User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
2.2.4 UFMC
About OFDM Signal Generation option
Overview of modulation schemes
As shown on Figure 2-1, in GFDM a time-frequency response is divided into k subcarriers and M symbols.
Related settings
●
Chapter 3.2.1, "Physical settings", on page 27
●
Chapter 3.2.2, "Filter settings", on page 33
●
Chapter 3.2.3, "Modulation configuration settings", on page 35
The Universal Filtered Multi-carrier (UFMC) technique is similar to the known OFDM
technique but the UFMC adds one extra filtering step in the signal processing chain.
In UFMC, several consecutive subcarries are bundled into subbands. All subbands
have an equal size. Each subband is shaped with an individual Dolph-Chebyshev filter.
The modulation uses an optional cyclic prefix for symbol separation.
The system model of UFMC is illustrated on Figure 2-2 ([2]).
Figure 2-2: UFMC system model (from [2])
Subband = Group of consecutive subcarriers
B = Number of subbands
k = Number of active subcarriers
S
IDFT = IFFT operation to transfer the n QAM symbols to the time domain
P/S = Parallel to serial conversion
F
Bk
x
Bk
= Vector of input symbols, QPSK, BPSK, or QAM modulated
Bk
= Subband filters with filter length L
= Output per subband; outputs are added
The resulting UFMC waveform is a non-orthogonal, asynchronous multi-carrier waveform.
Related settings
●
Chapter 3.2.1, "Physical settings", on page 27
●
Chapter 3.2.2, "Filter settings", on page 33
●
Chapter 3.2.3, "Modulation configuration settings", on page 35
11User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
2.2.5 FBMC
About OFDM Signal Generation option
Overview of modulation schemes
In the Filter Bank Multi-Carrier (FBMC) system, the filtering is applied on a per subcarrier basis.
The FBMC uses a synthesis-analysis filter bank method. Different implementations of
FBMC are discussed: Staggered modulated multitone (SMT FBMC), cosine modulated
multitone (CMT FBMC), and filtered multitone (FMT FBMC). The main focus is on the
SMT FBMC implementation.
In FBMS, adjacent subcarriers do overlap. The number of superimposing symbols in
time is referred as overlapping factor K. To maintain the orthogonality between the
adjacent subcarrier, the subcarriers are OQAM pre-processed. The cyclic prefix is
optional.
The implementation principle is illustrated on ([3]).
Figure 2-3: FBMC transmitter model (from [3])
1 = OQAM pre-processing (symbol staggering)
2 = Synthesis filter bank
N = Total number of subcarriers
k = 1,..., N is the subcarrier index
C2R = Complex to real conversion
⊗
= Complex multiplication by a factor Θ: Shifts the in-phase (I) components of the QAM symbols com-
pared to the quadrature (Q) components
IFFT = Inverse fast Fourier transform
Ak(z) = Polyphase filtering per subcarrier
N/2 = Upsampling by the factor N/2
-1
= Individual delays, added on each subcarrier
Z
s[m] = Transmit signal (the sum of all subcarriers)
K = Overlapping factor; defines number of superimposing symbols in time
OQAM pre-processing
Orthogonal QAM is method that shifts the in-phase components of the QAM modulated
symbols by T/2 (a half of the symbol length) compared to the quadrature (Q) components. The shift is applied alternating between the subcarrier. For example, if in the
12User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
2.2.6 Filtering
About OFDM Signal Generation option
Overview of modulation schemes
subcarrier N-1 the I component is shifted, then in the neighbor subcarriers (N-2 and N)
the Q component is shifted.
Related settings
●
Chapter 3.2.1, "Physical settings", on page 27
●
Chapter 3.2.2, "Filter settings", on page 33
●
Chapter 3.2.3, "Modulation configuration settings", on page 35
The modulation methods utilize filtering for signal shaping, but the filters are applied
differently.
Table 2-1: Overview of time and frequency domain filtering per modulation method
Modulation
methods
GFDM Per frame Per subcarrier
UFMC Per symbol Per subband
FBMC Per K overlapping sym-
f-OFDM Per frame Per subband
Time domain filtering Frequency domain filtering
Per subcarrier
bols
(in this implementation,
K = 4)
OFDM none none
Each modulation method proposes a prototype filter with different characteristics, like
filter type and filter length L. The proposed prototype filter types per modulation method
are as follows:
●
GFDM:
Root cosine, root raised cosine, Dirichlet, and rectangular filters
●
UFMC:
13User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
About OFDM Signal Generation option
Overview of modulation schemes
Dolph-Chebyshev filter
●
FBMC:
Root raised cosine, Phydyas filter
●
f-OFDM:
Soft truncation filter
●
OFDM
No default filter
For UFMC, f-OFDM and OFDM, you can also load a user-defined filter described in a
file. See "User filter file format (*.dat files)" on page 16.
Proposed prototype filters
Prototype filters can be designed in several ways, where each approach aims to fully
different requirements. In general, filters are designed to have good spectral characteristics and to be easy to be implemented.
GFDM relies on standard filter types with low complexity but with known drawback. A
prototype filter with rectangular frequency response suffers from an infinitely long
impulse response in time. A root raised cosine filter improves the side lobe suppression.
Figure 2-4: Example of filer characteristics: Root cosine filter with Rolloff Factor = 0.5
A = Filter impulse response
B = Filter frequency response
1 = Main lobe
2 = Side lobe suppression
Adjusting the filter parameters can change the filter shape. For example, changing the
filter rolloff factor influences the steepness of the filter slopes.
14User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
About OFDM Signal Generation option
Overview of modulation schemes
Figure 2-5: Example of the frequency response of a filter with different rolloff factors
In f-OFDM, the side lobe suppression is improved by applying a soft truncation window
function. The modulation uses the commonly known Hamming and Hanning windowing
functions. Optionally, the transient response of the filter is cut at the beginning and the
end of the signal. The drawback of this operation is that it increases the out-of-band
emissions.
Figure 2-6: Effect of the windowing function
1 = Rectangular filter
2 = Hanning window
3 = Hamming window
As shown on Figure 2-6, the soft truncation improves the side lobe suppression but
results in a wider main lobe.
UFMC proposes another windowing function with promising characteristics, the DolphChebischev. The Dolph-Chebischev window is characterized by the filter length L in
time domain and by the stopband attenuation (that is the desirable side lobe suppression) in the frequency domain.
In FBMC, the initial prototype filter is a root raised cosine (RRC) filter with a rolloff factor of 1. The Phydyas project [3] proposes an extra prototype filter designed using frequency sampling technique. This prototype filter is described by a few filter coefficients
that do not depend on the filter length.
For overlapping factor K = 4, the filter coefficients are [[3], 5GNOW D3.x]:
●
P0 = 1
●
P1 = 0.97195981
●
P2 = 1/√(2)
15User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
About OFDM Signal Generation option
Overview of modulation schemes
●
P3 = √(1 - P
2
)
1
The filter time response is calculated as:
Figure 2-7: Phydyas filter: Time response calculation
m = 0 to KNc – 2
K = 4 is the overlapping factor
N = Number of subcarriers
n = Symbol number
T = Symbol period
k = Subcarrier number
The stopband attenuation of the Phydyas filter exceeds 60 dB for the frequency range
of more than 10 subcarrier spacings [[3], 5GNOW D3.x].
User filter file format (*.dat files)
Additionally to the proposed prototype filter, for UFMC, f-OFDM and OFDM, you can
define your own filters.
User filter files are ASCII files with simple format and file extension *.dat.
These files describe filters as a sequence of normalized filter coefficients. Each coefficient is defined as a pair of I and Q samples. The I and Q components alternate at
each file line. The I and Q values vary between - 1 and + 1.
User filter file can contain up to 800 coefficients. Once loaded in the software, the file is
evaluated and the parameter User Filter Length shows the number of coefficients.
You can create user filter files for example with MATLAB, see for example the following
MATLAB script.
16User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
About OFDM Signal Generation option
Overview of modulation schemes
Example: Script that generates user filter file
Function [b, n] = generateUserFilter(filterSets, destPath)
% generateUserFilter returns the filter coefficients of a user-defined (baseband-)filter,
% whose are stored to a .dat file and can be
% loaded as an user filter in R&S SMW
%
% where:
% filterSets.fftSize is the used FFT size that is used for the OFDM modulation
% filterSets.nOccSubcarrier is the number of occupied subcarriers
% filterSets.transRegionRatio controls the steepness of the filter
% with regards to the ratio of fftSize/2
% filterSets.rp passband ripple in percentage
% filterSets.rs stopband attenuation ripple in percentage
%
% Example use:
% [b n] = RsFilt.generateUserFilter(struct('fftSize',4096, 'nOccSubcarrier',3376),'.');
%
% b - complex filter coefficients
% n - filter order
if (~isfield(filterSets,'transRegionRatio'))
filterSets.transRegionRatio = 0.07;
end
if (~isfield(filterSets,'rp'))
filterSets.rp = 0.0001;
end
if (~isfield(filterSets,'rs'))
filterSets.rs = 60;
end
% steepness of filter
transRegion = filterSets.transRegionRatio * filterSets.fftSize/2; %in
%, controls steepness of filter slopes, relative to nyquist frequency
%cutoff frequencies
f = [filterSets.nOccSubcarrier/2 filterSets.nOccSubcarrier/2+transRegion];
%ripples in dB
dev = [(10^(filterSets.rp/20)-1)/(10^(filterSets.rp/20)+1) 10^(-filterSets.rs/20)];
%estimate filter order
[n,fo,ao,w] = firpmord(f,[1 0],dev,filterSets.fftSize);
%make filter symmetric
n = n + mod(n,2)
%generate filter coefficients
17User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
About OFDM Signal Generation option
Supported multiple access schemes
b = firpm(n,fo,ao,w);
% fvtool(b); %displays filter response
%% write filter out into .dat filter coefficient file
coeffsOut = zeros(2*length(b),1);
coeffsOut(1:2:end) = real(b); coeffsOut(2:2:end) = imag(b);
% serialize complex coefficients
if (exist('destPath'))
dlmwrite([destPath '\smw_user_filter_' num2str(length(b))
'taps_' num2str(filterSets.nOccSubcarrier)
'scs_' num2str(filterSets.fftSize) 'fft.dat'],coeffsOut);
end
end
Related settings
●
Chapter 3.2.2, "Filter settings", on page 33
2.3 Supported multiple access schemes
Multiple access schemes are offered to assign the individual allocations to different
users.
Sparse Code Multiple Access (SCMA) is a non-orthogonal multiple access technology
that is considered as a key candidate 5G multiple access scheme. This technique adds
a CDMA (code division multiple access) component to the orthogonal division multiple
access technology OFDMA. SCMA uses multi-layer sparse codewords to separate
users that share common time and frequency resources.
In comparison to LTE, SCMA combines modulation mapping and spreading into one
operation. Each layer corresponds to unique codebook. The binary input data are mapped directly to the multiple layers complex codeword and then spread over the subcarriers.
SCMA encoding and parameters dependency
The example on Figure 2-8 is an illustration of a codebook.
18User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
N
K
J
About OFDM Signal Generation option
Supported multiple access schemes
Figure 2-8: SCMA encoding parameters
M = 4 is the codebook size (that is the number of codewords)
K = 4 is the spreading factor (that is the spread codeword length)
N = 2 is the number of non-zero elements
K-N = 2 is the number of zero elements
The number of layers J (that is also the number of unique codebooks) is calculated as
follows:
The number of layers gives the number of unique combinations that are possible for
the given codeword length (K) and number of non-zero elements (N). For K = 4 and N
= 2, the maximum number of layers is J = 6. In SCMA, one user can be assigned to
several layers, whereas each layer can be assigned to exact one user. Hence, the
maximum number of users corresponds to the number of layers and is also 6.
The example on Figure 2-9 illustrates the principle of the SCMA encoding.
19User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
About OFDM Signal Generation option
Supported multiple access schemes
Figure 2-9: SCMA encoding example (K = 4, N = 2, J = 6)
User#x = 6 users
Codebook#x = 6 codebooks or layers
Bitstream = Binary input data per user, for example User#0 sends bits (0,0)
CWy,x = Codeword#y form codebook#x
∑
= Combining the symbols
In this example, each user is assigned to one layer (codebook). The bits that the users
are transmitting are highlighted. For example, User#0 sends bits (0,0), that corresponds to codeword CW0,0 from the user-specific codebook#0. The 6 codewords of
the 6 users are combined; note that max. 3 symbols overlap. The combined signal of 6
users is spread over the subcarriers; the spreading factor is 4.
SCMA parameterization
The SCMA implementation in R&S SMW-K114 is illustrated Figure 2-8. it uses the following fix parameters:
●
Number of layers = 6
●
Codebook size = 4
●
Spreading factor = 4
Related settings
●
Chapter 3.3.3, "SCMA settings", on page 44
●
Chapter 3.3.2, "Allocations settings", on page 39
20User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
2.4 Physical layer parameterization
About OFDM Signal Generation option
Physical layer parameterization
Data allocation
The input symbols can be modulated in one of the base modulations: BPSK, QPSK,
16QAM, 64QAM, 256QAM and SCMA.
Additionally to the base modulation, you can load files with custom modulated I/Q data
and configure allocations modulated in other modulation shemes, like CAZAC sequences for instance. See "Custom I/Q file format (*.iqw or *.dat files)" on page 21.
Related settings:
●
Chapter 3.3, "Allocation settings", on page 37
Custom I/Q file format (*.iqw or *.dat files)
Custom I/Q files are files in one of the following formats:
●
*.dat files
ASCII files with simple format and file extension *.dat.
The file content is a sequence of pairs of I and Q samples. The I and Q components alternate at each file line. The I and Q values vary between - 1 and + 1.
●
*.iqw files
Binary files containing complex I/Q data of 32-bit floating point data type.
The file contents are I/Q samples described as paired alternating I and Q values
(IQIQIQ).
Related settings:
●
"Modulation" on page 41
Cyclic prefix (CP)
A guard time called cyclic prefix (CP) can optionally be used. Note that the CP calculation depends on the used modulation scheme.
Related settings:
●
"Cyclic Prefix Length" on page 29
●
For f-OFDM, also:
– "Alt. Cyclic Prefix Length" on page 30
– "CP No. Symbols/Alt. CP No. Symbols" on page 31
Sequence length calculation
The sequence length depends on the modulation method. Sequence length can be
expressed as number of symbols or as number of samples.
Calculation of the sequence length as number of samples and per modulation method
is as follows:
●
f-OFDM/OFDM
21User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
About OFDM Signal Generation option
Generating configuration files for R&S®VSE-K96
Sequence Length [Samples] = ("Total Number of Subcarriers"*"Sequence Length"
[Symbols] + "Cyclic Prefix Length"*"CP No. Symbols" + "Alt. Cyclic Prefix
Length"*"Alt. CP No. Symbols")
●
UFMC
Sequence Length [Samples] = "Cyclic Prefix Length" + ("Total Number of Subcarriers" + "Filter Length" - 1)*("Sequence Length" [Symbols]
●
FBMC
– If "Cut Transient Response = Off":
Sequence Length [Samples] = ("Sequence Length" [Symbols] + "Overlap Factor" - 0.5)*"Total Number of Subcarriers" + "Cyclic Prefix Length"
– If "Cut Transient Response = On":
Sequence Length [Samples] = ("Sequence Length" [Symbols] + "Overlap Factor" - 0.5)*"Total Number of Subcarriers" + "Cyclic Prefix Length" - "Total Number of Subcarriers"*"Overlap Factor"
Where "Overlap Factor = 4"
●
GFDM
Sequence Length [Samples] = "Cyclic Prefix Length" + "Total Number of Subcarriers"*"Sequence Length" [Symbols]
2.5
Generating configuration files for R&S
If you generate f-OFDM or OFDM modulated signals, the R&S SMW creates automatically an *.xml settings file. You can use this file for measurements with
Rohde & Schwarz signal analyzer, for example R&S®VSE-K96.
R&S®VSE-K96 processes the waveforms, generated with R&S SMW, differently,
depending on the allocation content:
●
Pilots:
For f-OFDM and OFDM the R&S®VSE-K96 requires pilot allocations for the signal
analysis. The analyzer needs the pilots to decode the channel coding properly.
●
Data:
The data allocations contain the resource elements of the corresponding modulation.
If you use the generated *.xml settings file, the information on the pilots and data
allocations is transmitted automatically.
●
Reserved:
Signal analyzer perceives reserved allocations as general OFDM modulated signals. The allocation content can be any user-defined information.
How to create, transfer and use the settings file
1. In the R&S SMW, configure the signal as required.
®
VSE-K96
2. Enable signal generation ("State > On").
The *.xml settings file is created automatically.
22User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
About OFDM Signal Generation option
®
Generating configuration files for R&S
VSE-K96
It is saved in the user directory as /var/user/K114/
Exported_K114_settings_K96.xml.
3. Connect to the user directory of the R&S SMW via USB, LAN, ftp or any other
access methods.
Open, for example, the \\<R&S SMW IP Address>\share\K114\.
See also, chapter "File and Data Management" in the R&S SMW user manual.
4. Copy the Exported_K114_settings_K96.xml file
5.
Transfer and load it in the R&S®VSE-K96
Required settings are performed automatically, so that you can start analyzing the
signal.
23User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
3 OFDM Signal Generation configuration and
OFDM Signal Generation configuration and settings
General settings
settings
Access:
► Select "Baseband > OFDM Signal Generation".
The remote commands required to define these settings are described in Chapter 3,
"OFDM Signal Generation configuration and settings", on page 24.
Settings:
● General settings......................................................................................................24
● General settings......................................................................................................27
● Allocation settings................................................................................................... 37
● Trigger settings....................................................................................................... 48
● Marker settings........................................................................................................53
● Clock settings..........................................................................................................54
● Local and global connectors settings......................................................................56
3.1 General settings
Access:
► Select "Baseband > OFDM Signal Generation".
This dialog comprises the standard general settings, to the default and the "Save/
Recall" settings, as well as selecting the modulation type and access to dialogs
with further settings.
Settings:
State..............................................................................................................................25
Set to Default................................................................................................................ 25
Save/Recall...................................................................................................................25
24User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
OFDM Signal Generation configuration and settings
General settings
Generate Waveform File...............................................................................................25
Modulation Type............................................................................................................26
Export path for XML settings.........................................................................................26
Set to Modulation Default..............................................................................................27
General Settings…........................................................................................................27
Allocation Settings….....................................................................................................27
State
Activates the standard and deactivates all the other digital standards and digital modulation modes in the same path.
Remote command:
[:SOURce<hw>]:BB:OFDM:STATe on page 59
Set to Default
Calls the default settings. The values of the main parameters are listed in the following
table.
Parameter Values
State Not affected by "Set to Default"
Modulation Type OFDM
Remote command:
[:SOURce<hw>]:BB:OFDM:PRESet on page 59
Save/Recall
Accesses the "Save/Recall" dialog, that is the standard instrument function for storing
and recalling the complete dialog-related settings in a file. The provided navigation
possibilities in the dialog are self-explanatory.
The filename and the directory, in which the settings are stored, are user-definable; the
file extension is predefined.
See also, chapter "File and Data Management" in the R&S SMW user manual.
Remote command:
[:SOURce<hw>]:BB:OFDM:SETTing:CATalog on page 59
[:SOURce<hw>]:BB:OFDM:SETTing:LOAD on page 59
[:SOURce<hw>]:BB:OFDM:SETTing:STORe on page 59
[:SOURce<hw>]:BB:OFDM:SETTing:DEL on page 60
Generate Waveform File
With enabled signal generation, triggers the instrument to save the current settings of
an arbitrary waveform signal in a waveform file with predefined extension *.wv. You
can define the filename and the directory, in that you want to save the file.
Using the ARB modulation source, you can play back waveform files and/or process
the file to generate multi-carrier or multi-segment signals.
Remote command:
[:SOURce<hw>]:BB:OFDM:WAVeform:CREate on page 60
25User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
OFDM Signal Generation configuration and settings
Modulation Type
Selects the modulation type.
"OFDM"
"f-OFDM"
"UFMC"
"GFDM"
"FBMC"
Remote command:
[:SOURce<hw>]:BB:OFDM:MODulation on page 60
You can create your own OFDM signal, for example configure the
allocations as required.
For more information, see Chapter 2.5, "Generating configuration files
for R&S®VSE-K96", on page 22.
Filtered-OFDM
The filtered OFDM (f-OFDM) modulation is a technique similar to the
UFMC modulation.
See Chapter 2.2.1, "OFDM", on page 9.
An *.xml setting file is created for this modulation type, too.
For more information, see Chapter 2.5, "Generating configuration files
for R&S®VSE-K96", on page 22.
Universal Filtered Multi-Carrier
UFMC is similar to OFDM but an additional filter is applied to each
subband. The modulation used an optional cyclic prefix and a DolphChebyshev filter.
See Chapter 2.2.4, "UFMC", on page 11.
Generalized Frequency Division Multiplexing
Data processing is performed on a two-dimensional block structure,
both in time and frequency domain.
Each subcarrier is pulse-shaped with a transmit filter and then modulated.
See Chapter 2.2.3, "GFDM", on page 10.
Filter Bank Multi-Carrier
This modulation uses staggered modulated multitone filter bank (SMT
FBMC) method where the subcarriers are OQAM modulated.
See Chapter 2.2.5, "FBMC", on page 12.
General settings
Export path for XML settings
Accesses a standard "File Select" dialog to specify the output path of the created
*.xml settings file.
26User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
OFDM Signal Generation configuration and settings
General settings
By default, the output path /var/user/K114-Export and output file
Exported_K114_settings_K96.xml is specified.
If modulation "State > On", the *.xml settings file is created automatically. You can
use this file for measurements with Rohde & Schwarz signal analyzer, for example
R&S®VSE-K96.
See also Example "Default "Exported_K114_settings_K96.xml" file" on page 89.
Remote command:
[:SOURce<hw>]:BB:OFDM:OUTPath on page 61
Set to Modulation Default
Calls the default settings for the selected Modulation Type.
Remote command:
[:SOURce<hw>]:BB:OFDM:MODPreset on page 60
General Settings…
Accesses the "General Settings" dialog of the selected modulation.
For description, see:
●
Chapter 3.2.1, "Physical settings", on page 27
●
Chapter 3.2.2, "Filter settings", on page 33
●
Chapter 3.2.3, "Modulation configuration settings", on page 35
Remote command:
n.a.
Allocation Settings…
Accesses the "Allocation Settings" dialog, see Chapter 3.3, "Allocation settings",
on page 37.
Remote command:
n.a.
3.2 General settings
● Physical settings..................................................................................................... 27
● Filter settings...........................................................................................................33
● Modulation configuration settings............................................................................35
3.2.1 Physical settings
Access:
► Select "OFDM Signal Generation > General Settings".
The physical settings are common to all modulation schemes.
27User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
OFDM Signal Generation configuration and settings
General settings
Settings:
Total Number Of Subcarriers.........................................................................................28
Occupied Number of Subcarriers..................................................................................28
Subcarrier Spacing........................................................................................................29
Sequence Length..........................................................................................................29
Cyclic Prefix Length...................................................................................................... 29
Alt. Cyclic Prefix Length................................................................................................ 30
CP No. Symbols/Alt. CP No. Symbols.......................................................................... 31
DFT-S (skip non-data)...................................................................................................31
Sampling Rate...............................................................................................................32
Occupied Bandwidth..................................................................................................... 32
Number Of Left/Right Guard Subcarriers......................................................................32
Total Number Of Subcarriers
Sets the number of available subcarriers, that is the FFT size.
The maximum number of subcarriers depends on the selected "Subcarrier Spacing" as
follows:
"Total Number of Subcarriers" * Subcarrier Spacing ≤ Bandwidth
max
The available baseband bandwidth depends on the installed options, see data sheet.
See also Chapter 2.4, "Physical layer parameterization", on page 21 for an overview of
this cross-reference between the parameters.
Remote command:
[:SOURce<hw>]:BB:OFDM:NSUBcarriers on page 62
Occupied Number of Subcarriers
Sets the number of occupied subcarriers.
The maximum number of occupied subcarriers is calculated as follows:
"Occupied Number of Subcarriers"
= 0.83 * Total Number Of Subcarriers
max
For the UFMC modulation, the "Occupied Number of Subcarriers" has to be a multiple
of the selected Number of Sub-bands.
28User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
OFDM Signal Generation configuration and settings
General settings
See also Chapter 2.4, "Physical layer parameterization", on page 21 for an overview of
this cross-reference between the parameters.
Remote command:
[:SOURce<hw>]:BB:OFDM:NOCCupied on page 62
Subcarrier Spacing
Sets the frequency distance between the carrier frequencies of the subcarriers.
The subcarriers are evenly distributed within the available bandwidth. All subcarriers
span the same bandwidth and there is no frequency gap between adjacent subcarriers.
Hence, the parameter "Subcarrier Spacing" sets also the subcarrier bandwidth.
See also Chapter 2.4, "Physical layer parameterization", on page 21 for an overview of
this cross-reference between the parameters.
Remote command:
[:SOURce<hw>]:BB:OFDM:SCSPace on page 62
Sequence Length
Sets the sequence length of the signal in number of symbols.
See also "Sequence length calculation" on page 21.
Remote command:
[:SOURce<hw>]:BB:OFDM:SEQLength on page 62
Cyclic Prefix Length
Sets the cyclic prefix (CP) length as number of samples.
The maximum number of symbols that can be used as a CP is calculated as follows:
"Cyclic Prefix Length"
= 0.5*Total Number Of Subcarriers
max
The cyclic prefix calculation depends on the modulation scheme:
●
f-OFDM/OFDM
Similar to the calculation in LTE, the cyclic prefix is applied as a cyclic extension to
each symbol.
Figure 3-1: Principle of cyclic prefix calculation in f-OFDM/OFDM (default configuration with CP
CP = Cyclic prefix
CP Length = Selected number of samples
Subcarriers = Total Number Of Subcarriers
Sequence Length = Selected number of symbols; 8 symbols in this example
Total number of samples = Calculated as described in "Sequence length calculation" on page 21
No. Symbols = 0, Alt. Cyclic Prefix Length = 0)
29User Manual 1177.6246.02 ─ 15
R&S®SMW-K114
OFDM Signal Generation configuration and settings
General settings
To apply different CP to a certain number of symbols or to use an alternating CP
pattern, use the combination of the parameters Alt. Cyclic Prefix Length and CP
No. Symbols/Alt. CP No. Symbols.
●
UFMC, GFDM, FBMC
If a "CP Length ≠ 0" is selected, then last samples of the complete signal are prepended to the signal.
Figure 3-2: Principle of cyclic prefix calculation in UFMC, GFDM, and FBMC
CP = Cyclic prefix
CP Length = Selected number of samples
Subcarriers = Total Number Of Subcarriers
Sequence Length = Selected number of symbols; 8 symbols in this example
Total number of samples = Calculated as described in "Sequence length calculation" on page 21
Remote command:
[:SOURce<hw>]:BB:OFDM:CPLength on page 63
Alt. Cyclic Prefix Length
For f-OFDM/OFDM, you can modify the default CP assignment where the same CP is
applied to each symbol and enable additional alternative CP, see Figure 3-3.
Both cyclic prefix (CP) lengths are set as number of samples. The parameters CP No.
Symbols/Alt. CP No. Symbols determine for how many symbols each of the CP is
applied. These parameters thus define a pattern of alternating cyclic prefixes.
Figure 3-3: Dynamic cyclic prefixes in f-OFDM/OFDM (example with Alt. Cyclic Prefix Length
Prefix Length, CP No. Symbols = 1, Alt. CP No. Symbols = 7)
CP = Cyclic prefix
CP Length = CP duration as number of samples, e.g 160 samples
Alt. CP Length = Duration of the alternative CP as number of samples, e.g 144 samples
CP No. Symbol = 1 (number of symbols for that the selected CP length is applied).
Alt. CP No. Symbols = 7 (number of symbols for that the selected Alt. CP length is applied).
≠
Cyclic
30User Manual 1177.6246.02 ─ 15
Loading...