R&S®FSV-K10x (LTE Downlink)
LTE Downlink Measurement
Application
User Manual
(;ÚÚË2)
1176766102
User Manual
Version 06
This manual describes the following firmware applications:
●
R&S®FSV-K100 EUTRA / LTE FDD Downlink Measurement Application (1308.9006.02)
●
R&S®FSV-K102 EUTRA / LTE MIMO Downlink Measurement Application (1309.9000.02)
●
R&S®FSV-K104 EUTRA / LTE TDD Downlink Measurement Application (1309.9422.02)
This manual describes the following R&S FSVA/FSV models with firmware version 3.30 and higher:
●
R&S®FSVA4 (1321.3008K05)
●
R&S®FSVA7 (1321.3008K08)
●
R&S®FSVA13 (1321.3008K14)
●
R&S®FSVA30 (1321.3008K31)
●
R&S®FSVA40 (1321.3008K41)
●
R&S®FSV4 (1321.3008K04)
●
R&S®FSV7 (1321.3008K07)
●
R&S®FSV13 (1321.3008K13)
●
R&S®FSV30 (1321.3008K30)
●
R&S®FSV40 (1321.3008K39/1321.3008K40)
It also applies to the following R&S®FSV models. However, note the differences described in Chapter 1.4,
"Notes for Users of R&S FSV 1307.9002Kxx Models", on page 13.
●
R&S®FSV3 (1307.9002K03)
●
R&S®FSV7 (1307.9002K07)
●
R&S®FSV13 (1307.9002K13)
●
R&S®FSV30 (1307.9002K30)
●
R&S®FSV40 (1307.9002K39/1307.9002K40)
© 2019 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.
1176.7661.02 | Version 06 | R&S®FSV-K10x (LTE Downlink)
The following abbreviations are used throughout this manual: R&S®FSV/FSVA is abbreviated as R&S FSV/FSVA.
R&S®FSV-K10x (LTE Downlink)
Contents
1 Preface.................................................................................................... 9
1.1 Documentation Overview............................................................................................. 9
1.1.1 Quick Start Guide............................................................................................................9
1.1.2 Operating Manuals and Help.......................................................................................... 9
1.1.3 Service Manual............................................................................................................... 9
1.1.4 Instrument Security Procedures....................................................................................10
1.1.5 Basic Safety Instructions...............................................................................................10
1.1.6 Data Sheets and Brochures.......................................................................................... 10
1.1.7 Release Notes and Open Source Acknowledgment (OSA).......................................... 10
1.1.8 Application Notes, Application Cards, White Papers, etc..............................................10
1.2 Conventions Used in the Documentation.................................................................10
Contents
1.2.1 Typographical Conventions...........................................................................................10
1.2.2 Conventions for Procedure Descriptions.......................................................................11
1.2.3 Notes on Screenshots................................................................................................... 11
1.3 How to Use the Help System......................................................................................11
1.4 Notes for Users of R&S FSV 1307.9002Kxx Models................................................ 13
2 Introduction.......................................................................................... 14
2.1 Requirements for UMTS Long-Term Evolution........................................................ 14
2.2 Long-Term Evolution Downlink Transmission Scheme.......................................... 16
2.2.1 OFDMA......................................................................................................................... 16
2.2.2 OFDMA Parameterization............................................................................................. 17
2.2.3 Downlink Data Transmission.........................................................................................19
2.2.4 Downlink Reference Signal Structure and Cell Search.................................................19
2.2.5 Downlink Physical Layer Procedures............................................................................21
2.3 References...................................................................................................................21
3 Welcome............................................................................................... 23
3.1 Installing the Software................................................................................................23
3.2 Application Overview..................................................................................................23
3.3 Support........................................................................................................................ 25
4 Measurement Basics........................................................................... 26
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4.1 Symbols and Variables...............................................................................................26
4.2 Overview...................................................................................................................... 27
4.3 The LTE Downlink Analysis Measurement Application...........................................27
4.3.1 Synchronization.............................................................................................................27
4.3.2 Channel Estimation and Equalization........................................................................... 29
4.3.3 Analysis.........................................................................................................................29
4.4 Performing Time Alignment Measurements.............................................................30
4.5 Performing Transmit On/Off Power Measurements.................................................32
5 Measurements and Result Displays...................................................35
5.1 Numerical Results.......................................................................................................35
5.2 Measuring the Power Over Time................................................................................38
5.3 Measuring the Error Vector Magnitude (EVM)..........................................................42
Contents
5.4 Measuring the Spectrum............................................................................................ 46
5.4.1 Frequency Sweep Measurements................................................................................ 46
5.4.2 I/Q Measurements.........................................................................................................50
5.5 Measuring the Symbol Constellation........................................................................ 53
5.6 Measuring Statistics................................................................................................... 54
5.7 3GPP Test Scenarios.................................................................................................. 56
6 Configuring and Performing the Measurement.................................59
6.1 Performing Measurements.........................................................................................59
6.2 Defining General Measurement Characteristics...................................................... 60
6.2.1 Defining Signal Characteristics..................................................................................... 61
6.2.2 Configuring the Input Level........................................................................................... 62
6.2.3 Configuring the Data Capture....................................................................................... 64
6.2.4 Configuring On/Off Power Measurements.................................................................... 65
6.2.5 Triggering Measurements............................................................................................. 66
6.3 Configuring MIMO Setups.......................................................................................... 67
6.4 Configuring Spectrum Measurements...................................................................... 68
6.4.1 General ACLR and SEM Configuration.........................................................................69
6.4.2 Configuring SEM Measurements.................................................................................. 69
6.4.3 Configuring ACLR Measurements................................................................................ 71
6.5 Defining Advanced Measurement Characteristics.................................................. 72
6.5.1 Controlling I/Q Data.......................................................................................................73
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6.5.2 Controlling the Input...................................................................................................... 73
6.5.3 Configuring the Digital I/Q Input.................................................................................... 74
6.6 Configuring the Signal Demodulation.......................................................................75
6.6.1 Configuring the Data Analysis.......................................................................................75
6.6.2 Compensating Measurement Errors............................................................................. 78
6.6.3 Configuring MIMO Setups.............................................................................................79
6.7 Configuring Downlink Frames................................................................................... 80
6.7.1 Configuring TDD Signals...............................................................................................80
6.7.2 Configuring the Physical Layer Cell Identity..................................................................81
6.7.3 PDSCH Subframe Configuration...................................................................................82
6.8 Defining Advanced Signal Characteristics...............................................................85
6.8.1 Defining the PDSCH Resource Block Symbol Offset....................................................85
6.8.2 Configuring the Reference Signal................................................................................. 86
Contents
6.8.3 Configuring the Synchronization Signal........................................................................ 86
6.8.4 Configuring the Control Channels................................................................................. 87
6.8.5 Configuring the Shared Channel...................................................................................91
7 Analysis................................................................................................ 93
7.1 Signal Part Selection.................................................................................................. 93
7.2 Measurement Units..................................................................................................... 94
7.3 Miscellaneous Analysis..............................................................................................94
7.4 Constellation Diagram Filter...................................................................................... 95
7.5 Y-Axis Scale.................................................................................................................96
7.6 Markers........................................................................................................................ 96
8 File Management..................................................................................99
8.1 File Manager................................................................................................................ 99
8.2 SAVE/RECALL Key....................................................................................................100
8.3 Test Models................................................................................................................100
9 Remote Commands........................................................................... 102
9.1 Common Suffixes......................................................................................................102
9.2 Introduction............................................................................................................... 103
9.2.1 Conventions used in Descriptions...............................................................................103
9.2.2 Long and Short Form.................................................................................................. 104
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9.2.3 Numeric Suffixes......................................................................................................... 104
9.2.4 Optional Keywords...................................................................................................... 104
9.2.5 Alternative Keywords.................................................................................................. 105
9.2.6 SCPI Parameters........................................................................................................ 105
9.3 General Configuration.............................................................................................. 107
9.4 Measurement Control................................................................................................111
9.5 Numeric Result Query...............................................................................................113
9.6 Measurement Result Query......................................................................................122
9.6.1 Using the TRACe[:DATA] Command...........................................................................122
9.6.2 Reading Results..........................................................................................................133
9.7 General Settings........................................................................................................137
9.7.1 Defining Signal Characteristics................................................................................... 137
9.7.2 Configuring the Input Level......................................................................................... 139
Contents
9.7.3 Configuring the Data Capture..................................................................................... 142
9.7.4 Configuring On/Off Power Measurements.................................................................. 144
9.8 MIMO Setups............................................................................................................. 144
9.9 Advanced Settings....................................................................................................145
9.9.1 Controlling I/Q Data.....................................................................................................145
9.9.2 Controlling the Input.................................................................................................... 146
9.9.3 Configuring the Digital I/Q Input.................................................................................. 147
9.10 Trigger Configuration............................................................................................... 148
9.11 Spectrum Measurements......................................................................................... 151
9.12 Signal Demodulation................................................................................................ 156
9.12.1 Configuring the Data Analysis.....................................................................................156
9.12.2 Compensating Measurement Errors........................................................................... 159
9.12.3 Configuring MIMO Setups...........................................................................................160
9.13 Frame Configuration.................................................................................................160
9.13.1 Configuring TDD Signals.............................................................................................160
9.13.2 Configuring the Physical Layer Cell Identity................................................................161
9.13.3 Configuring PDSCH Subframes..................................................................................163
9.14 Advanced Signal Characteristics............................................................................ 166
9.14.1 Defining the PDSCH Resource Block Symbol Offset..................................................166
9.14.2 Configuring the Reference Signal............................................................................... 166
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9.14.3 Configuring the Synchronization Signal...................................................................... 167
9.14.4 Configuring the Control Channel.................................................................................168
9.14.5 Configuring the Shared Channel.................................................................................172
9.15 Measurement Result Analysis................................................................................. 173
9.15.1 Selecting Displayed Data............................................................................................ 173
9.15.2 Selecting Units............................................................................................................ 175
9.15.3 Using Markers............................................................................................................. 176
9.15.4 Using Delta Markers....................................................................................................178
9.15.5 Scaling the Vertical Diagram Axis............................................................................... 181
List of Commands..............................................................................183
Index....................................................................................................187
Contents
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Contents
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R&S®FSV-K10x (LTE Downlink)
1 Preface
1.1 Documentation Overview
This section provides an overview of the R&S FSVA/FSV user documentation. Unless
specified otherwise, you find the documents on the R&S FSVA/FSV product page at:
www.rohde-schwarz.com/manual/FSVA
1.1.1 Quick Start Guide
Introduces the R&S FSVA/FSV and describes how to set up and start working with the
product. Includes basic operations, typical measurement examples, and general information, e.g. safety instructions, etc. A printed version is delivered with the instrument.
A PDF version is available for download on the Internet.
Preface
Documentation Overview
1.1.2 Operating Manuals and Help
Separate operating manuals are provided for the base unit and the firmware applications:
●
Base unit manual
Contains the description of all instrument modes and functions. It also provides an
introduction to remote control, a complete description of the remote control commands with programming examples, and information on maintenance, instrument
interfaces and error messages. Includes the contents of the getting started manual.
●
Firmware application manual
Contains the description of the specific functions of a firmware application. Basic
information on operating the R&S FSVA/FSV is not included.
The contents of the operating manuals are available as help in the R&S FSVA/FSV.
The help offers quick, context-sensitive access to the complete information for the
base unit and the firmware applications.
All operating manuals are also available for download or for immediate display on the
Internet.
1.1.3 Service Manual
Describes the performance test for checking the rated specifications, module replacement and repair, firmware update, troubleshooting and fault elimination, and contains
mechanical drawings and spare part lists.
The service manual is available for registered users on the global Rohde & Schwarz
information system (GLORIS, https://gloris.rohde-schwarz.com).
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1.1.4 Instrument Security Procedures
Deals with security issues when working with the R&S FSVA/FSV in secure areas. It is
available for download on the Internet.
1.1.5 Basic Safety Instructions
Contains safety instructions, operating conditions and further important information.
The printed document is delivered with the instrument.
1.1.6 Data Sheets and Brochures
The data sheet contains the technical specifications of the R&S FSVA/FSV. It also lists
the firmware applications and their order numbers, and optional accessories.
The brochure provides an overview of the instrument and deals with the specific characteristics.
Preface
Conventions Used in the Documentation
See www.rohde-schwarz.com/brochure-datasheet/FSV
1.1.7 Release Notes and Open Source Acknowledgment (OSA)
The release notes list new features, improvements and known issues of the current
firmware version, and describe the firmware installation.
The open source acknowledgment document provides verbatim license texts of the
used open source software.
See www.rohde-schwarz.com/firmware/FSV
1.1.8 Application Notes, Application Cards, White Papers, etc.
These documents deal with special applications or background information on particular topics.
See www.rohde-schwarz.com/application/FSV
1.2 Conventions Used in the Documentation
1.2.1 Typographical Conventions
The following text markers are used throughout this documentation:
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Convention Description
Preface
How to Use the Help System
"Graphical user interface elements"
[Keys] Key and knob names are enclosed by square brackets.
Filenames, 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.
Filenames, commands, coding samples and screen output are distinguished by their font.
tion marks.
1.2.2 Conventions for Procedure Descriptions
When operating the instrument, several alternative methods may be available to perform the same task. In this case, the procedure using the touchscreen is described.
Any elements that can be activated by touching can also be clicked using an additionally connected mouse. The alternative procedure using the keys on the instrument or
the on-screen keyboard is only described if it deviates from the standard operating procedures.
The term "select" may refer to any of the described methods, i.e. using a finger on the
touchscreen, a mouse pointer in the display, or a key on the instrument or on a keyboard.
1.2.3 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.
1.3 How to Use the Help System
Calling context-sensitive and general help
► To display the general help dialog box, press the [HELP] key on the front panel.
The help dialog box "View" tab is displayed. A topic containing information about
the current menu or the currently opened dialog box and its function is displayed.
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For standard Windows dialog boxes (e.g. File Properties, Print dialog etc.), no contextsensitive help is available.
► If the help is already displayed, press the softkey for which you want to display
help.
A topic containing information about the softkey and its function is displayed.
If a softkey opens a submenu and you press the softkey a second time, the submenu
of the softkey is displayed.
Contents of the help dialog box
The help dialog box contains four tabs:
●
"Contents" - contains a table of help contents
●
"View" - contains a specific help topic
●
"Index" - contains index entries to search for help topics
●
"Zoom" - contains zoom functions for the help display
Preface
How to Use the Help System
To change between these tabs, press the tab on the touchscreen.
Navigating in the table of contents
●
To move through the displayed contents entries, use the [UP ARROW] and [DOWN
ARROW] keys. Entries that contain further entries are marked with a plus sign.
●
To display a help topic, press the [ENTER] key. The "View" tab with the corresponding help topic is displayed.
●
To change to the next tab, press the tab on the touchscreen.
Navigating in the help topics
●
To scroll through a page, use the rotary knob or the [UP ARROW] and [DOWN
ARROW] keys.
●
To jump to the linked topic, press the link text on the touchscreen.
Searching for a topic
1. Change to the "Index" tab.
2. Enter the first characters of the topic you are interested in. The entries starting with
these characters are displayed.
3. Change the focus by pressing the [ENTER] key.
4. Select the suitable keyword by using the [UP ARROW] or [DOWN ARROW] keys
or the rotary knob.
5. Press the [ENTER] key to display the help topic.
The "View" tab with the corresponding help topic is displayed.
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Changing the zoom
1. Change to the "Zoom" tab.
2. Set the zoom using the rotary knob. Four settings are available: 1-4. The smallest
size is selected by number 1, the largest size is selected by number 4.
Closing the help window
► Press the [ESC] key or a function key on the front panel.
1.4 Notes for Users of R&S FSV 1307.9002Kxx Models
Users of R&S FSV 1307.9002Kxx models should consider the following differences to
the description of the newer R&S FSVA/FSV 1321.3008Kxx models:
●
Functions that are based on the Windows 10 operating system (e.g. printing or setting up networks) may have a slightly different appearance or require different settings on the Windows XP based models. For such functions, refer to the Windows
documentation or the documentation originally provided with the R&S FSV instrument.
●
The R&S FSV 1307.9002K03 model is restricted to a maximum frequency of
3 GHz, whereas the R&S FSVA/FSV1321.3008K04 model has a maximum frequency of 4 GHz.
●
The bandwidth extension option R&S FSV-B160 (1311.2015.xx) is not available for
the R&S FSV 1307.9002Kxx models. The maximum usable I/Q analysis bandwidth
for these models is 28 MHz, or with option R&S FSV-B70, 40 MHz.
Preface
Notes for Users of R&S FSV 1307.9002Kxx Models
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2 Introduction
Currently, UMTS networks worldwide are being upgraded to high speed downlink
packet access (HSDPA) in order to increase data rate and capacity for downlink packet
data. In the next step, high speed uplink packet access (HSUPA) will boost uplink performance in UMTS networks. While HSDPA was introduced as a 3GPP Release 5 feature, HSUPA is an important feature of 3GPP Release 6. The combination of HSDPA
and HSUPA is often referred to as HSPA.
However, even with the introduction of HSPA, the evolution of UMTS has not reached
its end. HSPA+ will bring significant enhancements in 3GPP Release 7. The objective
is to enhance the performance of HSPA-based radio networks in terms of spectrum
efficiency, peak data rate and latency, and to exploit the full potential of WCDMAbased
5 MHz operation. Important features of HSPA+ are downlink multiple input multiple output (MIMO), higher order modulation for uplink and downlink, improvements of layer 2
protocols, and continuous packet connectivity.
In order to ensure the competitiveness of UMTS for the next 10 years and beyond,
concepts for UMTS long term evolution (LTE) have been investigated. The objective is
a high-data-rate, low-latency and packet-optimized radio access technology. Therefore,
a study item was launched in 3GPP Release 7 on evolved UMTS terrestrial radio
access (EUTRA) and evolved UMTS terrestrial radio access network (EUTRAN). LTE/
EUTRA will then form part of 3GPP Release 8 core specifications.
Introduction
Requirements for UMTS Long-Term Evolution
This introduction focuses on LTE/EUTRA technology. In the following, the terms LTE or
EUTRA are used interchangeably.
In the context of the LTE study item, 3GPP work first focused on the definition of
requirements, e.g. targets for data rate, capacity, spectrum efficiency, and latency. Also
commercial aspects such as costs for installing and operating the network were considered. Based on these requirements, technical concepts for the air interface transmission schemes and protocols were studied. Notably, LTE uses new multiple access
schemes on the air interface: orthogonal frequency division multiple access (OFDMA)
in downlink and single carrier frequency division multiple access (SC-FDMA) in uplink.
Furthermore, MIMO antenna schemes form an essential part of LTE. In an attempt to
simplify protocol architecture, LTE brings some major changes to the existing UMTS
protocol concepts. Impact on the overall network architecture including the core network is being investigated in the context of 3GPP system architecture evolution (SAE).
● Requirements for UMTS Long-Term Evolution....................................................... 14
● Long-Term Evolution Downlink Transmission Scheme........................................... 16
● References..............................................................................................................21
2.1 Requirements for UMTS Long-Term Evolution
LTE is focusing on optimum support of packet switched (PS) services. Main requirements for the design of an LTE system are documented in 3GPP TR 25.913 [1] and
can be summarized as follows:
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●
Data Rate: Peak data rates target 100 Mbps (downlink) and 50 Mbps (uplink) for
20 MHz spectrum allocation, assuming two receive antennas and one transmit
antenna are at the terminal.
●
Throughput: The target for downlink average user throughput per MHz is three to
four times better than Release 6. The target for uplink average user throughput per
MHz is two to three times better than Release 6.
●
Spectrum efficiency: The downlink target is three to four times better than Release
6. The uplink target is two to three times better than Release 6.
●
Latency: The one-way transit time between a packet being available at the IP layer
in either the UE or radio access network and the availability of this packet at IP
layer in the radio access network/UE shall be less than 5 ms. Also C-plane latency
shall be reduced, e.g. to allow fast transition times of less than 100 ms from
camped state to active state.
●
Bandwidth: Scaleable bandwidths of 5 MHz, 10 MHz, 15 MHz, and 20 MHz shall
be supported. Also bandwidths smaller than 5 MHz shall be supported for more
flexibility.
●
Interworking: Interworking with existing UTRAN/GERAN systems and non-3GPP
systems shall be ensured. Multimode terminals shall support handover to and from
UTRAN and GERAN as well as inter-RAT measurements. Interruption time for
handover between EUTRAN and UTRAN/GERAN shall be less than 300 ms for
realtime services and less than 500 ms for non-realtime services.
●
Multimedia broadcast multicast services (MBMS): MBMS shall be further enhanced
and is then referred to as E-MBMS.
●
Costs: Reduced CAPEX and OPEX including backhaul shall be achieved. Costeffective migration from Release 6 UTRA radio interface and architecture shall be
possible. Reasonable system and terminal complexity, cost, and power consumption shall be ensured. All the interfaces specified shall be open for multivendor
equipment interoperability.
●
Mobility: The system should be optimized for low mobile speed (0 to 15 km/h), but
higher mobile speeds shall be supported as well, including high speed train environment as a special case.
●
Spectrum allocation: Operation in paired (frequency division duplex / FDD mode)
and unpaired spectrum (time division duplex / TDD mode) is possible.
●
Co-existence: Co-existence in the same geographical area and co-location with
GERAN/UTRAN shall be ensured. Also, co-existence between operators in adjacent bands as well as cross-border co-existence is a requirement.
●
Quality of Service: End-to-end quality of service (QoS) shall be supported. VoIP
should be supported with at least as good radio and backhaul efficiency and
latency as voice traffic over the UMTS circuit switched networks.
●
Network synchronization: Time synchronization of different network sites shall not
be mandated.
Introduction
Requirements for UMTS Long-Term Evolution
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2.2 Long-Term Evolution Downlink Transmission Scheme
2.2.1 OFDMA
The downlink transmission scheme for EUTRA FDD and TDD modes is based on conventional OFDM.
In an OFDM system, the available spectrum is divided into multiple carriers, called subcarriers, which are orthogonal to each other. Each of these subcarriers is independently modulated by a low rate data stream.
OFDM is used as well in WLAN, WiMAX and broadcast technologies like DVB. OFDM
has several benefits including its robustness against multipath fading and its efficient
receiver architecture.
Figure 2-1 shows a representation of an OFDM signal taken from 3GPP TR 25.892 [2].
In this figure, a signal with 5 MHz bandwidth is shown, but the principle is of course the
same for the other EUTRA bandwidths. Data symbols are independently modulated
and transmitted over a high number of closely spaced orthogonal subcarriers. In
EUTRA, downlink modulation schemes QPSK, 16QAM, and 64QAM are available.
Introduction
Long-Term Evolution Downlink Transmission Scheme
In the time domain, a guard interval may be added to each symbol to combat interOFDM-symbol-interference due to channel delay spread. In EUTRA, the guard interval
is a cyclic prefix which is inserted prior to each OFDM symbol.
Figure 2-1: Frequency-Time Representation of an OFDM Signal
In practice, the OFDM signal can be generated using the inverse fast Fourier transform
(IFFT) digital signal processing. The IFFT converts a number N of complex data symbols used as frequency domain bins into the time domain signal. Such an N-point IFFT
is illustrated in Figure 2-2, where a(mN+n) refers to the nth subchannel modulated data
symbol, during the time period mTu < t ≤ (m+1)Tu.
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Figure 2-2: OFDM useful symbol generation using an IFFT
The vector sm is defined as the useful OFDM symbol. It is the time superposition of the
N narrowband modulated subcarriers. Therefore, from a parallel stream of N sources
of data, each one independently modulated, a waveform composed of N orthogonal
subcarriers is obtained, with each subcarrier having the shape of a frequency sinc
function (see Figure 2-1).
Introduction
Long-Term Evolution Downlink Transmission Scheme
Figure 2-3 illustrates the mapping from a serial stream of QAM symbols to N parallel
streams, used as frequency domain bins for the IFFT. The N-point time domain blocks
obtained from the IFFT are then serialized to create a time domain signal. Not shown
in Figure 2-3 is the process of cyclic prefix insertion.
Figure 2-3: OFDM Signal Generation Chain
In contrast to an OFDM transmission scheme, OFDMA allows the access of multiple
users on the available bandwidth. Each user is assigned a specific time-frequency
resource. As a fundamental principle of EUTRA, the data channels are shared channels, i.e. for each transmission time interval of 1 ms, a new scheduling decision is
taken regarding which users are assigned to which time/frequency resources during
this transmission time interval.
2.2.2 OFDMA Parameterization
A generic frame structure is defined for both EUTRA FDD and TDD modes. Additionally, an alternative frame structure is defined for the TDD mode only. The EUTRA
frame structures are defined in 3GPP TS 36.211. For the generic frame structure, the
10 ms radio frame is divided into 20 equally sized slots of 0.5 ms. A subframe consists
of two consecutive slots, so one radio frame contains 10 subframes. This is illustrated
in Figure 2-4 (Ts expresses the basic time unit corresponding to 30.72 MHz).
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Figure 2-4: Generic Frame Structure in EUTRA Downlink
Figure 2-5shows the structure of the downlink resource grid for the duration of one
downlink slot. The available downlink bandwidth consists of subcarriers with a
spacing of Δf = 15 kHz. In the case of multi-cell MBMS transmission, a subcarrier
spacing of Δf = 7.5 kHz is also possible. can vary in order to allow for scalable
bandwidth operation up to 20 MHz. Initially, the bandwidths for LTE were explicitly
defined within layer 1 specifications. Later on a bandwidth agnostic layer 1 was introduced, with for the different bandwidths to be specified by 3GPP RAN4 to meet
performance requirements, e.g. for out-of-band emission requirements and regulatory
emission limits.
Introduction
Long-Term Evolution Downlink Transmission Scheme
Figure 2-5: Downlink Resource Grid
One downlink slot consists of OFDM symbols. To each symbol, a cyclic prefix (CP)
is appended as guard time, compare Figure 2-1. depends on the cyclic prefix
length. The generic frame structure with normal cyclic prefix length contains = 7
symbols. This translates into a cyclic prefix length of TCP≈5.2μs for the first symbol and
TCP≈4.7μs for the remaining 6 symbols. Additionally, an extended cyclic prefix is
defined in order to cover large cell scenarios with higher delay spread and MBMS
transmission. The generic frame structure with extended cyclic prefix of T
CP-E
≈16.7μs
contains = 6 OFDM symbols (subcarrier spacing 15 kHz). The generic frame struc-
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Introduction
Long-Term Evolution Downlink Transmission Scheme
ture with extended cyclic prefix of T
spacing 7.5 kHz). Table 2-1 gives an overview of the different parameters for the
generic frame structure.
Table 2-1: Parameters for Downlink Generic Frame Structure
Configuration
Normal cyclic prefix Δf=15 kHz 7 160 for first symbol
Extended cyclic prefix Δf=15 kHz 6 512 16.7 µs
Extended cyclic prefix Δf=7.5 kHz 3 1024 33.3 µs
Number of Symbols
2.2.3 Downlink Data Transmission
Data is allocated to the UEs in terms of resource blocks. A physical resource block
consists of 12 (24) consecutive subcarriers in the frequency domain for the Δf=15 kHz
(Δf=7.5 kHz) case. In the time domain, a physical resource block consists of DL N
consecutive OFDM symbols, see Figure 2-5.
bols in a slot. The resource block size is the same for all bandwidths, therefore the
number of available physical resource blocks depends on the bandwidth. Depending
on the required data rate, each UE can be assigned one or more resource blocks in
each transmission time interval of 1 ms. The scheduling decision is done in the base
station (eNodeB). The user data is carried on the physical downlink shared channel
(PDSCH). Downlink control signaling on the physical downlink control channel
(PDCCH) is used to convey the scheduling decisions to individual UEs. The PDCCH is
located in the first OFDM symbols of a slot.
≈33.3μs contains = 3 symbols (subcarrier
CP-E
Cyclic Prefix
Length in Samples
144 for other symbols
Cyclic Prefix
Length in µs
5.2 µs for first symbol
4.7 µs for other
symbols
is equal to the number of OFDM sym-
symb
2.2.4 Downlink Reference Signal Structure and Cell Search
The downlink reference signal structure is important for cell search, channel estimation
and neighbor cell monitoring. Figure 2-6 shows the principle of the downlink reference
signal structure for one-antenna, two-antenna, and four-antenna transmission. Specific
predefined resource elements in the time-frequency domain carry the reference signal
sequence. Besides first reference symbols, there may be a need for second reference
symbols. The different colors in Figure 2-6 represent the sequences transmitted from
up to four transmit antennas.
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Introduction
Long-Term Evolution Downlink Transmission Scheme
Figure 2-6: Downlink Reference Signal Structure (Normal Cyclic Prefix)
The reference signal sequence carries the cell identity. Each reference signal
sequence is generated as a symbol-by-symbol product of an orthogonal sequence r
(three of them existing) and a pseudo-random sequence r
PRS
(170 of them existing).
Each cell identity corresponds to a unique combination of one orthogonal sequence r
and one pseudo-random sequence r
PRS
, allowing 510 different cell identities.
OS
OS
Frequency hopping can be applied to the downlink reference signals. The frequency
hopping pattern has a period of one frame (10 ms).
During cell search, different types of information need to be identified by the handset:
symbol and radio frame timing, frequency, cell identification, overall transmission bandwidth, antenna configuration, and cyclic prefix length.
Besides the reference symbols, synchronization signals are therefore needed during
cell search. EUTRA uses a hierarchical cell search scheme similar to WCDMA. This
means that the synchronization acquisition and the cell group identifier are obtained
from different synchronization signals. Thus, a primary synchronization signal (PSYNC) and a secondary synchronization signal (S-SYNC) are assigned a predefined
structure. They are transmitted on the 72 center subcarriers (around the DC subcarrier)
within the same predefined slots (twice per 10 ms) on different resource elements, see
Figure 2-7.
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Figure 2-7: P-SYNC and S-SYNC Structure
As additional help during cell search, a common control physical channel (CCPCH) is
available which carries BCH type of information, e.g. system bandwidth. It is transmitted at predefined time instants on the 72 subcarriers centered around the DC subcarrier.
In order to enable the UE to support this cell search concept, it was agreed to have a
minimum UE bandwidth reception capability of 20 MHz.
Introduction
References
2.2.5 Downlink Physical Layer Procedures
For EUTRA, the following downlink physical layer procedures are especially important:
●
Cell search and synchronization
See above.
●
Scheduling
Scheduling is done in the base station (eNodeB). The downlink control channel
PDCCH informs the users about their allocated time/frequency resources and the
transmission formats to use. The scheduler evaluates different types of information,
e.g. quality of service parameters, measurements from the UE, UE capabilities,
and buffer status.
●
Link adaptation
Link adaptation is already known from HSDPA as adaptive modulation and coding.
Also in EUTRA, modulation and coding for the shared data channel is not fixed, but
rather is adapted according to radio link quality. For this purpose, the UE regularly
reports channel quality indications (CQI) to the eNodeB.
●
Hybrid automatic repeat request (ARQ)
Downlink hybrid ARQ is also known from HSDPA. It is a retransmission protocol.
The UE can request retransmissions of incorrectly received data packets.
2.3 References
[1] 3GPP TS 25.913: Requirements for E-UTRA and E-UTRAN (Release 7)
[2] 3GPP TR 25.892: Feasibility Study for Orthogonal Frequency Division Multiplexing
(OFDM) for UTRAN enhancement (Release 6)
[3] 3GPP TS 36.211 v8.3.0: Physical Channels and Modulation (Release 8)
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R&S®FSV-K10x (LTE Downlink)
[4] 3GPP TS 36.300: E-UTRA and E-UTRAN; Overall Description; Stage 2 (Release 8)
[5] 3GPP TS 22.978: All-IP Network (AIPN) feasibility study (Release 7)
[6] 3GPP TS 25.213: Spreading and modulation (FDD)
[7] Speth, M., Fechtel, S., Fock, G., and Meyr, H.: Optimum Receiver Design for Wireless Broad-Band Systems Using OFDM – Part I. IEEE Trans. on Commun. Vol. 47
(1999) No. 11, pp. 1668-1677.
[8] Speth, M., Fechtel, S., Fock, G., and Meyr, H.: Optimum Receiver Design for
OFDM-Based Broadband Transmission – Part II: A Case Study. IEEE Trans. on Commun. Vol. 49 (2001) No. 4, pp. 571-578.
Introduction
References
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R&S®FSV-K10x (LTE Downlink)
3 Welcome
The LTE measurement application uses the I/Q capture functionality of the following
spectrum and signal analyzers to enable LTE TX measurements conforming to the
3GPP specification.
●
R&S FSV
This manual contains all information necessary to configure, perform and analyze such
measurements.
● Installing the Software.............................................................................................23
● Application Overview...............................................................................................23
● Support....................................................................................................................25
3.1 Installing the Software
Welcome
Application Overview
For information on the installation procedure see the release notes of the R&S FSVA/
FSV.
3.2 Application Overview
Starting the application
Access the application via the "Mode" menu.
► Press the [MODE] key and select "LTE".
Note that you may have to browse through the "Mode" menu with the "More" softkey to find the LTE entry.
Second LTE channel
The application provides a second LTE channel that you can access via the Mode
menu with the softkey labeled "LTE2".
This second channel has the same functionality as the LTE channel. You can use it to
perform measurements on two LTE channels with a different configuration, for example
to test carrier aggregation.
Presetting the software
When you first start the software, all settings are in their default state. After you have
changed any parameter, you can restore the default state with the [PRESET] key.
CONFigure:PRESet on page 109
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Elements and layout of the user interface
The user interface of the LTE measurement application is made up of several elements.
Welcome
Application Overview
1 = Channel Bar: contains all currently active measurement applications
2 = Table Header: shows basic measurement information, e.g. the frequency
3 = Result Display Header: shows information about the trace
4 = Result Display Screen A: shows the measurement results
5 = Result Display Screen B: shows the measurement results
6 = Status Bar: shows the measurement progress, software messages and errors
7 = Softkeys: open settings dialogs and select result displays
The status bar
The status bar is located at the bottom of the display. It shows the current measurement status and its progress in a running measurement. The status bar also shows
warning and error messages. Error messages are generally highlighted.
Display of measurement settings
The header table above the result displays shows information on hardware and measurement settings.
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Table 3-1: Information displayed in the channel bar in the LTE measurement application
Freq The analyzer RF frequency.
Mode Link direction, duplexing, cyclic prefix and maximum number of physical
Meas Setup Number of transmitting and receiving antennas.
Welcome
Support
resource blocks (PRBs) / signal bandwidth.
Sync State The following synchronization states can occur:
Ext. Att External attenuation in dB.
Capture Time Capture length in ms.
3.3 Support
If you encounter any problems when using the application, you can contact the
Rohde & Schwarz support to get help for the problem.
To make the solution easier, use the "R&S Support" softkey to export useful information for troubleshooting. The R&S FSVA/FSV stores the information in a number of files
that are located in the R&S FSVA/FSV directory
C:\R_S\Instr\user\LTE\Support. If you contact Rohde & Schwarz to get help on
a certain problem, send these files to the support in order to identify and solve the
problem faster.
●
OK The synchronization was successful.
●
FAIL (C) The cyclic prefix correlation failed.
●
FAIL (P) The P-SYNC correlation failed.
●
FAIL (S) The S-SYNC correlation failed.
Any combination of C, P and S can occur.
Remote command:
[SENSe:]SYNC[:CC<cc>][:STATe]? on page 112
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4 Measurement Basics
● Symbols and Variables............................................................................................26
● Overview................................................................................................................. 27
● The LTE Downlink Analysis Measurement Application...........................................27
● Performing Time Alignment Measurements............................................................30
● Performing Transmit On/Off Power Measurements................................................32
4.1 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
b
l,k
Δf, Δ
coarse
Δf
res
ζ
H
l,k, l,k
i time index
î
, î
coarse
fine
k subcarrier index
l OFDM symbol index
N
FFT
N
g
N
s
N
RE
n subchannel index, subframe index
data symbol (actual, decided)
boosting factor
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)
length of FFT
number of samples in cyclic prefix (guard interval)
number of Nyquist samples
number of resource elements
n
l,k
Φ
l
r(i) received sample in the time domain
r
, r'
, r''
l,k
l,k
l,k
T useful symbol time
noise sample
common phase error
received sample (uncompensated, partially compensated, equalized) in the frequency domain
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R&S®FSV-K10x (LTE Downlink)
Measurement Basics
The LTE Downlink Analysis Measurement Application
T
g
T
s
guard time
symbol time
4.2 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.
4.3 The LTE Downlink Analysis Measurement Application
The block diagram in Figure 4-1 shows the EUTRA/LTE downlink measurement application from the capture buffer containing the I/Q data to the actual analysis block. The
outcome of the fully compensated reference path (orange) is the estimate â
transmitted data symbols a
received samples r''
of the measurement path (blue) still contain the transmitted sig-
l,k
. Depending on the user-defined compensation, the
l,k
nal impairments of interest. The analysis block reveals these impairments by comparing the reference and the measurement path. Prior to the analysis, diverse synchronization and channel estimation tasks have to be accomplished.
of the
l,k
4.3.1 Synchronization
The first of the synchronization tasks is to estimate the OFDM symbol timing, which
coarsely estimates both timing and carrier frequency offset. The frame synchronization
block determines the position of the P-/S-Sync symbols in time and frequency by using
the coarse fractional frequency offset compensated capture buffer and the timing estimate î
the reference signal is used for synchronization. The fine timing block prior to the FFT
allows a timing improvement and makes sure that the EVM window is centered on the
measured cyclic prefix of the considered OFDM symbol. For the 3GPP EVM calculation according to 3GPP TS 36.211 (v8.9.0), the block “window” produces three signals
taken at the timing offsets , and . For the reference path, only the signal taken at
the timing offset is used.
to position the window of the FFT. If no P-/S-Sync is available in the signal,
coarse
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R&S®FSV-K10x (LTE Downlink)
kl
lTfNNjlkNNjj
klklkl
NeeeHAR
CFOres
resFFTS
SFO
FFTS
CPE
l
,
22
,,,
.
Measurement Basics
The LTE Downlink Analysis Measurement Application
Figure 4-1: Block diagram for the LTE DL measurement application
After the time to frequency transformation by an FFT of length N
, the phase syn-
FFT
chronization block is used to estimate the following:
●
The relative sampling frequency offset ζ (SFO)
●
The residual carrier frequency offset Δf
●
The common phase error Φl (CPE)
(CFO)
res
According to 3GPP TS 25.913 and 3GPP TR 25.892, the uncompensated samples can
be expressed as
Equation 4-1:
where
●
The data symbol is a
●
The channel transfer function is H
●
The number of Nyquist samples is Ns within the symbol time T
●
The useful symbol time T=Ts-T
●
The independent and Gaussian distributed noise sample is n
, on subcarrier k at OFDM symbol l
l,k
l,k
g
s
l,k
Within one OFDM 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.
The results of the tracking estimation block are used to compensate the samples r
l,k
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R&S®FSV-K10x (LTE Downlink)
2
,
,
,
,
''
,
,
ˆ
kl
kl
kl
klkl
kl
b
a
Eb
ar
EVM
kl
kl
kl
ln
b
ar
EVM
,
,
''
,
,
ˆ
Whereas a full compensation is performed in the reference path, the signal impairments that are of interest to the user are left uncompensated in the measurement path.
After having decided the data symbols in the reference path, an additional phase tracking can be utilized to refine the CPE estimation.
4.3.2 Channel Estimation and Equalization
As shown in Figure 4-1, there is one coarse and one fine channel estimation block.
The reference signal-based coarse estimation is tapped behind the CFO compensation
block (SFO compensation can optionally be enabled) of the reference path. The coarse
estimation block uses the reference signal symbols to determine estimates of the channel transfer function by interpolation in both time and frequency direction. A special
channel estimation (
coarse estimation results are used to equalize the samples of the reference path prior
to symbol decision. Based on the decided data symbols, a fine channel estimation is
optimally performed and then used to equalize the partially compensated samples of
the measurement path.
Measurement Basics
The LTE Downlink Analysis Measurement Application
) as defined in 3GPP TS 36.211 is additionally generated. The
4.3.3 Analysis
The analysis block of the EUTRA/LTE downlink measurement application allows to
compute a variety of measurement variables.
EVM
The error vector magnitude (EVM) measurement results 'EVM PDSCH QPSK/16QAM/64-QAM' are calculated according to the specification in 3GPP TS 36.211.
All other EVM measurement results are calculated according to
Equation 4-2:
on subcarrier k at OFDM symbol l, where b
power of all possible constellations is 1 when no boosting is applied, the equation can
be rewritten as
is the boosting factor. Since the average
l,k
Equation 4-3:
The average EVM of all data subcarriers is then
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R&S®FSV-K10x (LTE Downlink)
l k
kl
REdata
data
data
data
EVM
N
EVM
2
,
1
tsjQtsItr
|1|balancegain modulator Q
}1arg{mismatch quadrature Q
Equation 4-4:
Measurement Basics
Performing Time Alignment Measurements
The number of resource elements taken into account is denoted by N
RE data
.
I/Q imbalance
The I/Q imbalance can be written as
Equation 4-5:
where s(t) is the transmit signal, r(t) is the received signal, and I and Q are the weighting factors. We define that I:=1 and Q:=1+ΔQ.
The I/Q imbalance estimation makes it possible to evaluate the
Equation 4-6:
and the
Equation 4-7:
based on the complex-valued estimate .
Other measurement variables
Without going into detail, the EUTRA/LTE downlink measurement application additionally provides the following results.
●
Total power
●
Constellation diagram
●
Group delay
●
I/Q offset
●
Crest factor
●
Spectral flatness
4.4 Performing Time Alignment Measurements
The measurement application allows you to perform time alignment measurements
between different antennas.
The measurement supports setups of up to four 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.
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