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Agilent 89600 Vector Signal Analysis SoftwareOption BHD 3GPP LTEModulation Analysis

Technical Overview and Self-Guided Demonstration

2

Table of Contents Introduction ............................................................................................................................. 3

Downlink physical layer channels and signals ........................................................... 4

Uplink physical layer channels and signals ................................................................. 5

Measurement and Troubleshooting Sequence ............................................................... 6

Setting up the demonstration ......................................................................................... 7

Spectrum and Time Domain Measurements ................................................................... 8

Measuring occupied bandwidth and power ................................................................ 9

Using the spectrogram display ......................................................................................11

Basic Digital Demodulation ............................................................................................... 15

Overview of the parameters under Format tab ........................................................ 16

Overview of the parameters under Profi le tab ......................................................... 17

Overview of the parameters under LTE Allocation Editor window ..................... 18

Overview of the parameters under LTE Downlink

Control Channel Properties window ........................................................................... 19

Advanced Digital Demodulation ....................................................................................... 26

Selective channel analysis ............................................................................................ 30

EVM for data channels ................................................................................................... 30

Analyzing individual symbols ........................................................................................ 31

MIMO analysis ..................................................................................................................34

LTE uplink signal analysis .............................................................................................. 37

Summary ................................................................................................................................. 41

Glossary .................................................................................................................................. 41

Ordering Information ........................................................................................................... 42

Related Literature .................................................................................................................44

Web Resources .....................................................................................................................44

3

Third-generation UMTS, based on wideband code-division multiple access

(W-CDMA), has been deployed all over the world. To ensure that this system

remains competitive in the future, 3GPP began a project to define the long-term

evolution of UMTS cellular technology in November 2004. The specifications

related to this effort are formally known as the evolved UMTS terrestrial

radio access (E-UTRA) and evolved UMTS terrestrial radio access network

(E-UTRAN), but are more commonly referred to by the project name LTE. The

first version of LTE is documented in Release 8 of the 3GPP specifications.

3GPP’s high-level requirements for LTE include reduced cost per bit, better

service provisioning, flexible use of new and existing frequency bands, simplified

network architecture with open interfaces, and an allowance for reasonable

power consumption by terminals. These are detailed in the LTE feasibility study,

3GPP Technical Report (TR) 25.912, and in the LTE requirements document,

TR 25.913.

For more information on the LTE standard and testing concerns, see 3GPP Long

Term Evolution: System Overview, Product Development, and Test Challenges,

literature publication number 5989-8139EN.

Before beginning our demonstration, here is some useful information to help

explain the LTE downlink and uplink channels and signals.

Introduction

4

Downlink physical layer channels and signals

The DL physical channels are Physical Downlink Shared Channel (PDSCH),

Physical Downlink Control Channel (PDCCH), and Physical Broadcast Channel

(PBCH). The DL physical signals are reference signal (RS) and synchronization

signal. Table 1 below has information on the modulation format and purpose

for each of the downlink channels and signals.

Table 1. LTE downlink channels and signals

DL channels

Full nameModulation format

Purpose

PBCH Physical Broadcast Channel QPSK Carries cell-specific information

PDCCH Physical Downlink Control Channel QPSK Scheduling, ACK/NACK

PDSCH Physical Downlink Shared ChannelQPSK16QAM64QAM

Payload

PMCH Physical Multicast ChannelQPSK16QAM64QAM

Payload for Multimedia Broadcast Multicast Service (MBMS)

PCFICHPhysical Control Format Indicator Channel

QPSK

Carries information about the number of OFDM symbols (1, 2 or 3) used for transmission of PDCCHs in a sub-frame.

PHICHPhysical Hybrid ARQ Indicator Channel

BPSK with I & Q CDM

Carries the hybrid-ARQ ACK/NAK

DL signals

Full nameModulation sequence

Purpose

P-SS Primary Synchronization SignalOne of 3 Zadoff-Chu sequences

Used for cell search and identifi cation by the UE. Carries part of the cell ID (one of 3 orthogonal sequences).

S-SS Secondary Synchronization SignalTwo 31-bit M-sequences (binary)

Used for cell search and identifi cation by the UE. Carries the remainder of the cell ID (one of 168 binary sequences).

RS Reference Signal (Pilot)

Complex I+jQ pseudo random sequence (length-31 Goldsequence) derived from cell ID

Used for DL channel estimation. Exact sequence derived from cell ID, (one of 3*168=504).

5

Uplink physical layer channels and signals

Uplink (UL) physical channels are Physical Uplink Shared Channel (PUSCH),

Physical Uplink Control Channel (PUCCH) and Physical Random Access Channel

(PRACH). Two types of uplink reference signals are supported: demodulation

reference signal (DM-RS) which is associated with transmission of PUSCH

or PUCCH, and sounding reference signal (S-RS) which is not associated

with transmission of PUSCH or PUCCH. Table 2 below has information on the

modulation format and purpose for each of the uplink channels and signals.

Table 2. LTE uplink channels and signals

UL channels

Full nameModulation format

Purpose

PRACH Physical Random Access Channeluth root Zadoff-Chu

Call setup

PUCCH Physical Uplink Control Channel BPSK, QPSK Scheduling, ACK/NACK

PUSCH Physical Uplink Shared ChannelQPSK16QAM64QAM

Payload

UL signals

Full nameModulation sequence

Purpose

DM-RS Demodulation Reference Signaluth root Zadoff-Chu

Used for synchronization to the UE and UL channel estimation

S-RS Sounding Reference Signal Zadoff-ChuUsed to monitor propagation conditions with UE.

6

Measurement andTroubleshootingSequence

When measuring and troubleshooting digitally modulated systems, it is

tempting to go directly to digital modulation and the measurement tools. It is

usually better to follow a measurement sequence: one that begins with basic

spectrum measurements and continues with vector (combined frequency and

time) measurements, before switching to basic digital modulation analysis, and,

finally, to advanced and/or standard-specific analysis. This is the sequence we

will use in this demo guide. This sequence of measurements is especially useful

because it reduces the chance that important signal problems will be missed.

Step 1: Spectrum and time domain measurmentsThese measurements give the basic parameters of the signal in the frequency

and time domain so that correct demodulation can take place in step 2.

Parameters such as center frequency, bandwidth, symbol timing, power,

and spectral characteristics are investigated.

Step 2: Basic digital demodulationThese measurements evaluate the quality of the constellation. Along with

a display of the constellation, they include static parameters such as EVM,

I/Q offset, frequency error, and symbol clock error.

Step 3: Advanced digital demodulationThese measurements are used to investigate the causes of errors uncovered

in the basic modulation parameters, particularly EVM errors. These include

dynamic parameters such as error vector frequency, error vector time, and

selective error analysis.

The 89600 VSA software has the advantage that you can recall saved time

capture recordings and analyze the signal as though you were acquiring data

from hardware. In the following pages, we will recall and analyze LTE signals

available on the 89600 VSA software demo CD.

Spectrum and time domain measurmentsGet basics right, fi nd major problems

Basic digital demodulation

Signal quality numbers, constellation, basic error vector measurement

Advanced digital demodulationFind specifi c problems and causes

7

Setting up the demonstration

Table 3 describes the minimum hardware required to run the 89600 VSA software.

Table 4 describes the 89600 VSA software required to use this demonstration

guide. If you do not already have a copy of the software, you can download

a free trial version at www.agilent.com/find/89600.

Table 3. System requirements

CharacteristicMicrosoft® Windows® XP Professional

Microsoft® Windows® Vista Business, Enterprise, or Ultimate

CPU600 MHz Pentium® or AMD-K6 > 600 MHz (> 2 GHz recommended)

1 GHz 32-bit (x86)(> 2 GHz recommended)

Empty slots (desktop)

1 PCI-bus slot (Two recommended – VXI hardware only)

1 PCI-bus slot (Two recommended – VXI hardware only)

Empty slots (laptop)

1 CardBus Type II slot (IntegratedFireWire® recommended for VXIhardware only)

1 CardBus Type II slot (IntegratedFireWire® recommended for VXIhardware only)

RAM 512 MB (1 GB recommended) 1 GB (2 GB recommended)

Video RAM 4 MB (16 MB recommended) 128 MB (512 MB recommended)

Hard disk 512 MB available 512 MB available

Additionaldrives

CD-ROM to load the software; license transfer requires a 3.5 inch floppy disk drive, network access, or USB memory stick

CD-ROM to load the software; license transfer requires a 3.5 inch floppy disk drive, network access, or USB memory stick

Interfacesupport

LAN, GPIB, USB, or FireWire1 interface (VXI HW only)

LAN, GPIB, USB, or FireWire1 interface (VXI HW only)

Table 4. Software requirements

Version 89600 version 9.00 or higher (89601A, 89601AN, 89601N12)

Options

-200

-300

-BHD

(89601A, 89601AN only)

Basic vector signal analysis

Hardware connectivity (required only if using measurement hardware)

LTE modulation analysis

1. For a list of supported IEEE-1394 (FireWire) interfaces, visit www.agilent.com/fi nd/89600 and search the FAQ's for information on "What type of IEEE-1394 interface can I use in my computer to connect to the 89600S VXI hardware?"

Table 5. Recall the signal

Instructions: 89600 VSA software Toolbar menus

Preset the software

File > Preset > Preset All

Note: Using Preset All will cause all saved user state information to be lost. If this is a concern, save the current state before using Preset All. Click File > Save > Setup

Note: The Menu/Toolbars, Display Appearance, and User Color Map may also be saved in a similar way.

Recall the recording of a 5 MHz LTE downlink signal

File > Recall > Recall Recording(c:\Program Files\Agilent\89600 VSA\Help\Signals)

Select the downlink recording Select LTE_DL_5MHz_v820.sdfClick Open

Start the measurement Click (toolbar, left side)

Auto scale Trace ARight click Trace ASelect Y Auto Scale

Auto scale Trace B Right click Trace BSelect Y Auto Scale

8

The first step in the troubleshooting process is to set up the signal measurement

parameters, such as range and scaling, and verify its spectral and time domain

behavior before demodulation takes place.

It is important to ensure your signal is clear and distinct when you make your

measurements. The following section will show how to measure the occupied

bandwidth. But first we must change the RBW filter and the main time length

so we can view a more detailed signal.





Table 6. Increasing resolution and time length


Change the RBW filter and increase the

frequency points for better resolution.

The auto frequency points selection

chooses the best resolution for the

given time capture. You can change

this if you prefer.

Meas Setup > ResBW > ResBW Mode > Arbitrary

(pull down menu)

Frequency Points >Auto

Time (tab) > Main Time Length > 900 usec

Click Close

Auto scale Trace A and Trace BRight click in Trace A. Click Y Auto Scale

Right click in Trace B. Click Y Auto Scale

Figure 1. Time and spectrum display.

Note: This fi rst fi gure includes

the menu toolbar and status

bar on the top and bottom of

the window, respectively. In

the interest of displaying as

much information as possible,

the remaining fi gures will not

display them. You can toggle

them on/off by clicking Display

> Appearance > Window

9

Table 7. Measuring OBW


Display OBW traceRight-click Trace A

Select Show OBW

Activate OBW Summary table

Double click the Trace B title (B: Ch1 Main Time)

Select Marker from the Type menu on the left-hand side of the box

Select Obw Summary TrcA from the Data menu on the

right-hand side of the box.

Click OK

Measuring occupied bandwidth and band power

The Occupied Bandwidth (OBW) measurement, coupled with the OBW

Summary Table, can quickly and accurately report many useful results. Using

the method described in Table 7, the OBW can be displayed along with the

corresponding table of results shown. Trace B in Figure 2 displays several

important measurements quickly, including the occupied bandwidth, band

power, and power ratio. This signal has a nominal bandwidth of 7.68 MHz to

allow for full viewing of the signal, while the actual bandwidth is measured at

approximately 4.4 MHz. The power ratio is listed, but it is also a user adjustable

feature. By clicking Markers > OBW, the value in the box can be changed to

show the ratio between OBW power and total power.

Your display should look similar to Figure 2.

Figure 2. Occupied bandwidth measurement with summary data table.

Table 8. Clear OBW measurement


Clear OBW display

Double click the Trace B title (B: TrcA OBW Summary Data)

Select Channel 1 from the Type menu on the left-hand side

of the box that appears.

Select Main Time from the Data menu on the right-hand side of

the box.

Click OK

Right-click Trace A

De-select Show OBW

10

The band power marker feature measures the power of the modulated signal,

or “channel power”, by integrating over a specifi ed bandwidth in the frequency

domain.

Table 9. Setting up band power marker


Select the band power marker tool

Click Markers > Tools > Band Power

(Or, alternatively, you can click the band power marker button

on the menu toolbar)

Drop the band power marker on

Trace A

On Trace A, move the mouse to the center frequency of the band

to be measured.

Click to drop the marker.

Expand the band power marker

Place the mouse pointer on the vertical band power marker and

left click to drag/expand the marker so it includes the entire

bandwidth.

Note: You may need to adjust the center of the band power

marker so the entire bandwidth falls within the marker lines.

The band power should be displayed at the bottom of the window. This is the

total power inside the bandwidth of the band power marker. You can expand or

shrink the width of the marker to measure the power over specifi c frequencies.

You can control the band power marker more precisely by opening the Markers

Properties window. Click Markers > Calculation to access user-settable text

boxes for setting the center and width of the band power marker.

Figure 3. Band power display.

We will not need the band power marker any further. To turn it off, simply right-

click anywhere in Trace A and de-select Show Band Power. This shortcut can be

used to toggle the band power marker on/off. You will also need to return your

mouse cursor to a pointer. Click the Pointer button on the toolbar.

11

Using the spectrogram display

The spectrogram is a three-dimensional display that shows the changes in

signal spectrum over time. It is particularly useful when analyzing time-varying

signals. Features of signal transients, OFDM signal structure, and spectral

splatter can all be identifi ed with this display. Using overlap processing

improves its usefulness further. Overlap processing causes the analyzer to

adjust the amount of new data it uses for each time record, and has the effect

of causing the signal to replay in "slow motion." It is particularly useful for

locating and examining transients.

Table 10. Set up spectrogram display


Set the time length to 100 3sec. Set

the overlap processing to 95% (You

can adjust this later to even higher

values to examine the effect of overlap

processing).

Click MeasSetup > Time

Set the Main Time Length to 100 usec

Set Max Overlap (Avg Off) to 95%

Click Close

Activate spectrum display for Trace BDouble click the Trace B title (B: Ch1 Main Time)

In the Data: column select Spectrum

Enable the spectrogram display on

Trace A

Right-click Trace A.

Select Show Spectrogram

Pause the measurement to temporarily

halt playbackClick the pause/continue button in the toolbar

Click on the color bar on the left hand side of the trace (See Figure 4 for refer-

ence). Note: If you cannot see the color bar, your window size may be too small.

Then, scroll up using your mouse scroll wheel or by pressing the up arrow key on

your keyboard. Continue to scroll up until you have a display similar to Figure 4

shown below. An exact replica is not necessary, but for many spectrum/spectro-

gram settings you should be able to see the periodic “ears” in the display, shown

as small peaks on both sides of the spectrogram. These appear at the transitions

between symbols and allow you to see the number and timing of OFDM symbol

transitions.

You may have noticed that Figure 4 has horizontal and vertical white lines. These

are markers, which can be used as another method to measure certain aspects

of the spectrogram, including the center frequency. Follow the steps in Table 11

to set up these markers.

12

Table 11. Setting up spectrogram markers


Enable the spectrogram marker

(Make sure Trace A is active by

clicking anywhere in the trace)

Markers > Spectrogram

Check the Trace Select box, then highlight the Trace num-

ber entry box and move the spectrogram marker using the

down arrow on your keyboard. This marker initially appears as

a while horizontal line at the very bottom of the trace.

Note: Both spectrum traces are connected, so you may have

noticed that as you move the spectrogram marker up and

down along the spectrogram, the spectrum in Trace B will

reflect the correct display of the spectrum in that specific

moment in time.

Play the recording until you see two

abnormal spots of lighter color

Click the pause button in the toolbar to continue

playback on the recording. When a pair of abnormal “spots”

appear in the spectrogram, press the pause button again to

stop the playback. See the figure below for reference.

Place the spectrogram marker on the

spots

Re-position the white spectrogram marker so that it is in line

with the spots.

Enable the main trace marker Click on the diamond icon near the top of the menu

toolbar

Place marker on left spotClick on the trace where the spot is located to drop a marker

on that position

Add an offset marker Right click on the trace and select Show Offset

Move offset to marker Right click on the trace and select Move Offset to Mkr

Click and drag offset to right spotClick and drag the vertical white line over to the right until the

marker is in line with the other spot

13

The “spots” are actually spectral nulls. The middle 72 subcarriers are reserved

for P-SS, S-SS and PBCH channels and signals. In our case, P-SS and S-SS only

occupy 62 of the subcarriers, which leave these spectral nulls unoccupied on

either side of those center 62 subcarriers. Thus, since each subcarrier occupies

15 kHz, 72*15 = 1080 kHz, or approximately 1MHz. Depending on the exact

location of your markers, your offset value should be approximately this value.

Figure 4. Spectrogram display showing LTE signal structure.

Offset markers can also be used to show ∆y values. For example, you could use

this to measure the "ears", or the symbol transitions. To see the ∆y, click and

drag the horizontal white marker lines so they are aligned with the "ears." The

∆y value is shown at the bottom of the window.

In this particular situation, the center frequency was given. However, in some

cases, especially during troubleshooting, the center frequency may not be given

or clearly noticeable. The main trace marker can also be used to measure the

center frequency of the signal.

But fi rst, let us use a new set of markers. Right-click on Trace A and

un-check Show Marker. Then follow the steps in Table 12 below.

14

Table 12. Using spectrogram markers to find center frequency


Temporarily turn off spectrogram

display

Right click anywhere on Trace A

De-select Show Spectrogram

Increase main time length to obtain a

more defined signal

MeasSetup > Time

Set the Main Time Length to 900 usec

Click Close

Adjust Y-axis settings

Double click on the upper left corner axis value on Trace A

In the Y Top pop up window, set the value to -33 dBm

Double click on the center axis value.

(It should read 15 dB/div)

In the Y /Div pop up window, set the value to 6 dB

Adjust the span

Double click on the Span value for Trace A

(lower right corner of trace)

Set the value to 5 MHz

Click OK

Restart the spectrogram

Click the Restart button

Right click anywhere in Trace A and check Show Spectrogram

Note: you should see a distinct line in the center of the spectro-

gram. If you do not, adjust the color bar as previously instructed

until it is more noticeable.

Zoom in on center

Click the Pause button to pause playback.

Click the Select Area tool on the menu toolbar

Click and drag a small square around the center line.

Select Scale X from the menu box that appears.

Click OK

Place marker on center lineUsing the same trace marker as before, place a marker on the line

that you just magnified

At the bottom of the window, the marker value should appear. The value should

read approximately 1GHz, confi rming the value of the center frequency. This line

is actually a null subcarrier that is not transmitted at the center frequency. Since

it is not being transmitted, it has a lower power level at that point, and thus is

shown in a lighter color. Your display should look similar to the fi gure below.

Figure 5. Spectrogram display showing center frequency subcarrier.

Turn off the spectrogram display and marker by right clicking on Trace A and

un-checking both Show Spectrogram and Show Marker.

15

Basic Digital Demodulation

Once you have examined your signal and verified that there are no major spectral

or time problems, the next step is to demodulate it. We'll set up a constellation

display and measure basic I/Q parameters using the LTE demodulator as shown

in Table 13. This recording has all the control channels, plus 3 different data

channels using QPSK, 16 QAM and 64 QAM modulation formats.

LTE downlink signal analysis





Table 13. Set up the LTE demodulator


Change the display to show four traces

in a 2x2 grid

Display > Layout > Grid 2x2

(Or alternatively, Click on the drop down menu near the top of the

menu.

Select Grid 2x2 from the available options.)

Select the LTE demodulator MeasSetup > Demodulator > 3G Cellular > LTE

Set up the demodulator for downlink

analysis

See below for descriptions of each tab

and the parameters available

MeasSetup > Demod Properties > Format (tab)

Click Downlink from the Direction: drop down menu.

Click the Preset to Standard... box and select 5 MHz (25 RB)

from the drop down menu

Go to Profile (tab)

Click the Edit Control Params box

Make sure the PDCCH Allocation field is set to 3 for each

Subframe (Sf) Sf0 thru Sf9

Click OK.

Go to Format (tab)

Make sure Auto is selected under Cell ID

Select automatic detection of Resource

Blocks (RB)

Go to Profile (tab)

Check RB Auto Detect (Note: This setting is checked by default)

Click Close

Begin demodulationPress Restart

Your display should look similar to Figure 6

16

Figure 6. Default measurement traces for LTE demodulation.

The next section gives you information about the different parameters under the Format and Profile tabs in the MeasSetup > Demod Properties menu. You will use this information to help set up the parameters which allow the analyzer to demodulate the signal. This information is available to you in the Help text. Note that the 89600 VSA software allows you to manually set many parameters. You can also use a setup file from Agilent Signal Studio if you are using that product for signal generation. For proper demodulation, the analysis setup must

match the signal transmitted.

Overview of the parameters under Format tab

Figure 7. LTE demodulation Format tab.

Direction: Drop-down list to select LTE direction, either Downlink or Uplink.

Bandwidth: Drop-down list to select LTE bandwidth, ranges between

1.4 MHz to 20 MHz.

Preset to Standard: This button presets all demodulation parameters to default

values, and also presets the demodulator to the specified bandwidth.

Sync Type: Selects the type of Synchronization; Physical Synchronization Signal

(P-SS) or Reference Signal (RS).

17

CP Length: Selects the cyclic prefix used in the transmitted signal. There are two

choices, "Normal" and "Extended." The software can auto-detect which to use,

or let the user specify manually.

Cell ID: Cell ID determines the physical layer cell identity. There are 504 possible

physical layer cell identities. A specific value may be entered, or it may be

automatically determined by selecting “Auto.”

RS-PRS: Selects the Pseudo Random Sequence (PRS) used for the Reference Signal

(RS). The software can auto-detect which to use or it can use a custom setting.

Number of Tx Antenna: Dictates the number of transmit antennas the demodulator

should search for.

TX Antenna: There can be up to four different antenna ports on a downlink

transmitter. The RS sequence for the different antenna ports can be demodulated

to make an analysis on each antenna port.

Antenna Detection Threshold: User-settable dB value such that signals from the

different antenna ports must be above to be detected by the demodulator.

Tx Diversity/MIMO: Transmit Diversity/Multiple-Input Multiple-Output. This

controls additional features including Control Channel Precoding and Shared

Channel Precoding.

Control Chan Precoding: Drop down menu to turn Transmit Diversity (Tx Diversity)

on or off in the control channel.

Shared Chan Precoding: Drop down menu to turn Transmit Diversity (Tx Diversity)

on or off in the shared channel.

Overview of the parameters under Profile tab

Figure 8. LTE demodulation Profile tab.

RB Auto Detect: Enables auto detection of shared channel (user) allocations. The

demodulator groups allocations by modulation type. Note: This setting is checked

by default.

Composite Include: Determine which channels and signals are displayed on traces

and included in EVM and Power composite results.

Edit User Mapping: Click to open LTE Allocation Editor window, shown in Figure 9.

Edit Control Parameters: Click to open LTE Downlink Control Channel Properties,

shown in Figure 10.

18

Overview of the parameters under LTE Allocation Editor window

Figure 9. LTE Allocation Editor window

RB Auto-Detect: Automatically detect the Resource Block (RB) and slot allocation

for each burst based on modulation format used for each downlink shared channel

(PDSCH).

Include: Select or De-Select accompanying modulation format.

Name: Specifies name of modulation format used for the data channel.

PDSCH: Physical Downlink Shared Channel.

RB Start/End: Specifies the RB allocation (in frequency domain) for a particular

data channel.

Slot Start/ End: Specifies time slot allocation (in time domain) for a particular data

channel.

Mod Type: Specifies the modulation format used for the data channel (QPSK, 16

QAM, 64 QAM).

Power Boost (dB): The power of the subcarriers relative to the 0 dB level

determined by the RS power level.

RB mapping for PDSCH: When the resource blocks are not auto-detected, you can

manually add allocations and set specific RB Start/End and Slot Start/End values

for them. These will appear in the RB mapping grid, from which you can click and

drag to reposition or resize allocations.

19

Overview of the parameters under LTE Downlink Control Channel Properties window

Figure 10. LTE Control Channel Properties window.

P-SS: Primary-Synchronization Signal.

S-SS: Secondary-Synchronization Signal.

PBCH: Physical Broadcast Channel.

PCFICH: Physical Control Format Indicator Channel.

RS: Reference Signal.

PDCCH: Physical Downlink Control Channel.

Power Boost: The power of the subcarriers relative to the 0 dB level determined by

the RS power level.

Allocations (Symbols per subframe): Determines the amount of symbols

designated for each subframe.

Subframe: Subframe number; 0-9.

# Symbols: Specifies the number of symbols under each respective subframe.

Const: When selected, the number of symbols specified under Subframe 0 is cou-

pled to the other Subframes. De-select to manually enter individual values.

PHICH: Physical Hybrid ARQ Indicator Channel.

Despread IQ Orthog Seq Index: When selected, the traces display PHICH constel-

lation points after dispreading. This arbitrarily remaps the demodulated values

of individual PHICH sequences on the I and Q value of the subcarriers containing

those sequences. When cleared, PHICH constellation points are displayed as

received, which is the summation of all PHICHs within the same PHICH group.

Allocation (Ng): Determines the number of PHICH groups per subframe;

1/6, 1/2, 1, or 2.

Duration: Tells the demodulator how many symbols per subframe are used by

PHICH; Normal or Extended.

20

Table 14. Display frame summary information


Change Trace C to show the frame

summary

Double click the Trace C trace title (C: Ch1 OFDM Err

Vect Spectrum)

In the Data: column select Frame Summary

Click OK

Auto scale Trace BRight click on Trace B

Select Y Auto Scale

When you turn on digital modulation analysis, you automatically receive the

default measurements in the default locations. But they are easy to change to

display any available trace data in any trace location. As we begin our measure-

ments, let's change one of the traces to show the Frame Summary data next to

the constellation so that you can easily interpret the colors.

But first we need to increase the number of slots in the Measurement Interval.

Click MeasSetup > Demod Properties > Time (Tab). Set the Result Length to 20.

You should have a display similar to the one in Figure 11 below. Let's look at

some of the traces:

Figure 11. LTE constellation and frame summary information.

Trace A: Composite constellation diagram color-coded by the channel type

as shown in Trace C. The RS (pilot) uses Pseudo Random Sequence (PRS) for

modulation, shown in the constellation diagram in cyan (light blue). The P-SS is

transmitted as a Zadoff-Chu sequence and thus appears as irregularly spaced

points on a circle (pink color).

Trace B: Spectrum trace showing pre-demod measurements including center

frequency, span, resolution bandwidth (RBW) and time length. There is no change

to this trace even though we are making demodulation measurements.

21

Trace C: Summary of all active channels including EVM for each channel, their

relative power modulation format and allocated RB for each channel. The color

of the channel mirrors the color-coding used in other displays, such as the

constellation diagram. Below is a list of the channels and their descriptions.

P-SS: Primary-Synchronization Signal.

S-SS: Secondary-Synchronization Signal.

PBCH: Physical Broadcast Channel.

PCFICH: Physical Control Format Indicator Channel.

PHICH: Physical Hybrid ARQ Indicator Channel.

PDCCH: Physical Downlink Control Channel.

RS: Reference Signal.

PDSCH_QPSK: Physical Downlink Shared Channel: QPSK modulation format.

PDSCH_16QAM: Physical Downlink Shared Channel: 16 QAM modulation format.

PDSCH_64QAM: Physical Downlink Shared Channel: 64 QAM modulation format.

Non-alloc: All non-allocated channels.

Trace D: Summary table listing many EVM measurements. Consult the Help text

for a full listing of all possible error summary results.

One of the greatest strengths of the 89600 VSA is its error analysis. Here we'll

look at the wide range of built-in error traces available to you.

22

Your display should be similar to what is shown in Figure 12.

Figure 12. LTE error traces.

Table 15. View the multiple EVM traces supported


Change the display to show six traces Select Grid 3x2 from the layout drop down menu

Change Trace B to show EVM per

Resource Block (RB)

Double click the Trace B title (B: Ch1 Spectrum)

In the Data: column select RB Error Mag Spectrum

Click OK

Change Trace C to show EVM per

subcarrier

Double click the Trace C title (C: Ch1 Frame Summary)

In the Data: column select Error Vector Spectrum

Click OK

Change Trace D to show the frame

summary

Double click the Trace D title (D: Ch1 Error Summary)


Click OK

Change Trace E to show EVM per

time slot

Double click the Trace E title (E: Ch1 OFDM Err Vect Time)

In the Data: column select RB Error Mag Time

Click OK

Change Trace F to show EVM per

symbol

Double click the Trace F title (F: Ch1 Frame Summary)

In the Data: column select Error Vector Time

Click OK

Auto scale all traces (except Trace D) Right click on each trace and click Y Auto Scale

23

Here is information describing the traces you just changed. In some descriptions

you will see "z-axis" mentioned. Access to these z-axis values is possible by

placing a marker on the trace and using the up/down arrow keys to walk through

the points available and see the measurement values.

Trace B: OFDM RB Error Magnitude Spectrum — Shows the EVM of each RB with

respect to frequency, and displays EVM for every slot during that RB. The x-axis

is RB, y-axis is EVM, and z-axis is slot. This example uses a 5 MHz LTE profile

which has 25 RBs as shown on the x-axis. This is a useful display to see the

range of EVM performance per user allocation and is unique to Agilent.

Trace C: OFDM Error Vector Spectrum — Shows the EVM for each subcarrier

and displays the difference between the measured symbols and the reference

symbols for each subcarrier. The x-axis is subcarrier, the y-axis is EVM and the

z-axis is symbol. For a 5 MHz LTE signal, there are 300 subcarriers (25 RB x

12 subcarrier/RB).

Trace E: OFDM RB Error Magnitude Time — Shows the EVM of each RB with

respect to time during the measurement interval and displays EVM for each RB

during that slot. The x-axis is slot, y-axis is EVM, and z-axis is RB. The default

capture interval for the LTE application is 1 frame (20 slots). This trace shows

EVM across the 20 slots as shown on the x-axis.

Trace F: OFDM Error Vector Time — Shows the EVM for each symbol and displays

the difference between the measured symbols and the reference symbols for

each symbol in the measurement interval. The x-axis is symbol, the y-axis is EVM

and the z-axis is subcarrier. The default capture interval for the LTE application

is 20 slots. For signals using a normal cyclic prefix, there are 7 symbols/slot.

This means that for 20 slots there are 140 symbols, as shown here on the x-axis.

This trace clearly shows the different control channels. For example, you can

clearly see the PDCCH channels (shown in a yellow color) occupying the first

3 symbols in each sub-frame.

You may have noticed that the edges of the Error Vector Spectrum traces are high-

er than normal. By default, the software matches the standard’s method of EVM

calculation. It measures the EVM at two points, takes the maximum between the

two and uses that as the EVM at that point. Then, while calibrating the equalizer,

it takes the average over 19 RS (pilots). This will lead to a high EVM if the signal

was transmitted using a bad filter. For our purposes, this high EVM problem can be

resolved by adjusting the appropriate settings under the Advanced tab. Follow the

steps in Table 16 below to do so.

24

Your display should look similar to Figure 13 shown below.

Figure 13. Six display window of various EVM traces.

For our purposes, we will follow the standard. To return to the original settings,

follow the steps below in Table 17.

Table 16. Reduce the EVM by adjusting the EVM averaging window


Turn off Moving Average FilterClick MeasSetup > Demod Properties > Advanced (tab)

and de-select Moving Avg Filter

Choose EVM Window CenterSelect EVM Window Center under the Symbol Timing

Adjust options

Table 17. Return to original setting


Turn on Moving Average FilterClick MeasSetup > Demod Properties > Advanced (tab)

and select Moving Avg Filter

Choose Max of EVM Window

Start / End

Select Max of EVM Window Start / End under the Symbol

Timing Adjust options

Click Close

25

The LTE application also has the ability to measure power in each RB and each

slot. Let's view both EVM and power in each RB and Slot.

When finished, your display should look similar to the one shown in Figure 14.

Figure 14. Power per RB and Slot.

Trace B now shows EVM in each RB, while Trace C shows the Power in each

RB. Similarly, Trace E shows EVM in each time slot, while Trace F shows the

power in each time slot.

Table 18. Power per RB and Slot


Change Trace C to show Power

per RB

Double click the Trace C title (C: Ch1 OFDM Err Vect

Spectrum)

In the Data: column select RB Power Spectrum

Click OK

Change the y-axis scale of Trace C

to dB

Double click Lin Mag on y-axis of Trace C

In the Format drop down menu, select Log Mag (dB)

Click OK

Change Trace F to show power

per Slot

Double click the Trace F title (F: Ch1 OFDM Err Vect Time)

In the Data: column select RB Power Time

Click OK

Change the y-axis scale of Trace F

to dB

Double click Lin Mag on y-axis of Trace F

In the Format drop down menu, select Log Mag (dB)

Click OK

26

Advanced Digital Demodulation

Advanced demodulation techniques allow you to focus in on signal errors, or set

up the analyzer so that more detailed troubleshooting is possible.

To begin with, we'll focus in on slot zero in the OFDM Error Vector Time display

to more carefully analyze our signal and its errors.

Your display for Trace F should look similar to the one shown in Figure 15.





Table 19. Selective slot analysis


Change Trace C to show EVM per

subcarrier

Double click the Trace C title (C: Ch1 OFDM RB Power Spectrum)

In the Data: column select Error Vector Spectrum

Click OK

Change Trace F to show EVM per

symbol

Double click the Trace F title (F: Ch1 OFDM RB Power Time)

In the Data: column select Error Vector Time

Click OK

Zoom on slot #0 (i.e. 1st 7 symbols) of

the EVM per symbol trace - Trace F

Markers > Tools > Select area or use the select area box

from the tool bar

Click and hold to drag a box around the first time slot on Trace F,

less than 10% of the first x-axis grid.

Select Scale X & Y

Click OK

The x-axis should now display symbols 0 to 6. If not, go to

Trace > X Scale > and set Left Reference to 0 Sym and

Right Reference to 6 Sym

Click Close

Auto scale Trace F Right click on Trace F and click Y Auto Scale

Return mouse cursor to pointer Click on the Pointer button in the toolbar

27

Figure 15. OFDM EVM for slot 0 only. Colors shown correspond to channel type.

Looking at slot 0 we can see a lot of information. Remember that there are

7 symbols in a slot. The channel type is color-coded, and matches the color

coding used in the Frame Summary trace.

Symbol 0: RS (cyan color) is transmitted on every 6th subcarrier, while PDCCH

channels (yellow), PCFICH channels (purple), and PHICH channels (light red) are

transmitted on the rest of the subcarriers.

Symbols 1 & 2: More PDCCH channels (yellow).

Symbol 3: All of the subcarriers are used to transmit user data (PDSCHs), as

shown by red (QPSK), orange (16 QAM) and dark green (64 QAM).

Symbol 4: RS (cyan color) is transmitted on every 6th subcarrier. The rest of

the subcarriers are used to transmit user data (PDSCHs) as shown by the

other colors.

Symbol 5: S-SS (blue color) is transmitted on the center 72 subcarriers (only

62 out of the reserved 72 subcarriers are used; the remaining 10 subcarriers are

not used). The rest of the subcarriers are used to transmit user data (PDSCHs),

as shown by the different colors.

Symbol 6: P-SS (pink) is transmitted on the center 72 subcarriers (only 62 out

of the reserved 72 subcarriers are used; the remaining 10 subcarriers are not

used). The rest of the subcarriers are used to transmit user data (PDSCHs), as

shown by the different colors.

Note: Some of the channel colors may not be as noticeable as the others. You

can confirm that certain channels are being transmitted by using the marker tool

and observing the marker information that appears at the bottom of the window.

Also, you may have noticed that PBCH (light green) is not seen in any of the

above symbols. This is because slot 0 does not transmit PBCH. If you change

your scale x-axis to show slot 1 (symbols 7 to 13), you will see the first occur-

rence of PBCH. To do so, right click under Trace F on the x-axis annotation area,

and select X-Scale. Set Left Reference to 7 and Right Reference to 13.

To go back to the full scale, go to Edit > Undo Scale, or Trace > X Scale > Full

Scale.

28

Another useful capability is marker coupling. This allows you to view error sources

from different measurements. For instance, if you see an error and place a marker

on it, you can track that same point in the signal in different error displays.

In the example below, we are going to create an "error" by asking the analyzer to

make a measurement that does not match the actual signal. You will adjust the

P-SS power boost level value, which is used to normalize those channels.

Your display should be similar to the one shown in Figure 16.

Notice that the markers all report data from the same point in time, but in

different error domains. Notice that the marker also gives you information on

channel type. In this situation, since we set the Power Boost level for P-SS

channel to be slightly higher than the rest, it stands out as a higher EVM. Notice

the color-coding throughout the different displays, showing the P-SS (pink) has

been selected and coupled throughout the displays. This method of marker

coupling provides a very convenient troubleshooting method.

Table 20. Marker coupling


Turn off the RMS trace (white line

across Traces B, C, E and F)

Click on Trace B. Under Trace > Digital Demod > uncheck Show 2D Avg LineClick CloseDo the same on Traces C, E and F

Auto scale all traces (except Trace D) Right click on each trace and click Y Auto Scale

Change the amplitude of the P-SS

channel to show a different value

MeasSetup > Demod Properties > Profile (tab)

Click the Edit Control Params… box to open the LTE

Downlink Control Channel Properties window

Set the Power Boost value for P-SS to 0.8 dB

Click OK

Before closing the Demod Properties window, note that, as

a convenience, the power boosting levels for all channels are

shown, including the new value for the P-SS which you just

adjusted.

Click Close to close the Demod Properties window

Couple markers between displays

Right click on Trace A and select Show Marker. Do this for all

traces (except Trace D).

Once the marker is placed in all traces (except Trace D), couple

the markers by going to Markers > Couple Markers

Place marker on P-SS channel

Now click on Trace C so the marker is on one of the P-SS

carriers (Pink).

The markers in all the other displays will show the same point in

time but provide different error views.

29

Figure 16. Markers coupled across traces.

Table 21. Turn off coupled markers and change P-SS Power Boost level back to normal


Turn off the markers in each display

Right click on each trace and uncheck Show Marker .

Note: Coupling Markers will automatically place a marker on

Trace D. Since the Frame Summary trace does not support a

right click, go to Markers and un-check Show Marker, this will

clear the empty marker status line at the bottom of the window.

Change the value of Power Boost for

P-SS back to original value


Click the Edit Control Params button to open the LTE

Downlink Control Channel Properties window

Set the Power Boost value for P-SS to 0.65 dB

Click OK

Click Close

30

Selective channel analysis

This recording signal has 3 downlink shared channels (PDSCHs) using QPSK,

16 QAM and 64 QAM modulation formats. The QPSK channel occupies the

fi rst 9 RBs (subcarrier –150 thru subcarrier –43); the 16 QAM user occupies the

center 8 RBs (subcarrier –42 thru subcarrier 54 excluding DC); and the 64 QAM

user occupies the last 8 RBs (subcarrier 55 thru subcarrier 150). Remember that

each RB has 12 subcarriers, so in each 5 RBs there are 60 subcarriers.

We can clearly see these allocations by making measurements only on the data

channels.

EVM for data channels

The analysis software allows users to make EVM measurement on selected

channels only. Let's set up the analyzer to measure EVM for the data channels,

but not for control channels and signals:

Your display should be similar to the one shown in Figure 17.

Figure 17. EVM analysis of data channels only.

Table 22. Selecting specific channels for analysis


Turn off control channels and signals

from the analysis


Un-check P-SS, S-SS, PBCH, PCFICH, PHICH,

PDCCH, and RS

Click Close

31

Now all the traces and EVM results include only data channels with no control

channels or signals included. You can clearly see the allocation for each user in

terms of RB, slot, subcarrier and symbol. The color coding makes it very easy to

distinguish the different users.

Notice all of the channels are still registered and recognized, seen under the

Frame Summary table, even though we have de-selected the control and reference

channels. This convenient feature allows for specific channel analysis without

forgetting the presence of the other channels.

Let's turn the control channel analysis back on.

Analyzing individual symbols

For in-depth troubleshooting, the analysis software allows users to selectively

measure specific symbols, slots, sub-frames or a frame within the signal. Before

we make measurements on a symbol-by-symbol basis, let's quickly review the

Time tab under MeasSetup > Demod Properties which contains parameters

describing the signal time length, alignment, and measurement region.

For more information on each of these parameters, see the 89600 Help Text.

Figure 18. Demodulation Time tab used to adjust analysis region.

measurementoffset

measurementinterval

result length

analysisstart

boundary

0 ms = trigger

DL: frame start0 ms = UL: beginning of first slot

Time

Raw Main Time

Search Time

Figure 19. LTE analysis regions.

Table 23. Turn the control channel analysis back on


Turn the analysis of control channels

and signals back to ON


Select P-SS, S-SS, PBCH, PCFICH, PHICH, PDCCH, and RS

Click Close

32

The analysis software allows you to modify the following parameters:

Result Length: Determines the signal capture length. This is the data used by

the analyzer for demodulation and signal analysis.

Analysis Start Boundary: This specifies the boundary at which the Result

Length must start. For DL signals, you can choose to begin at the frame,

half-frame, subframe or slot boundary. For UL signals, only the slot boundary

start position is available. This is because there are no sync channels for the

UL signal, so it is difficult to automatically determine frame and sub-frame

boundaries.

Measurement Interval: Determines the time length of Result Length data that

is used for computing and displaying the trace data results.

Measurement Offset: Determines the start position of the Measurement

Interval within the Result Length.

The ability to examine specific symbols individually allows you to make all of

the available measurements on just this symbol. In other words, you can gate

the measurement window to examine only symbol N. The following example

will set up the analyzer to look at only the 7th symbol of slot 0, and perform

EVM measurements on this symbol.

Your display for symbol #0 analysis should look similar to the one shown

in Figure 20. All measurements shown are now made for symbol #0 only,

which contains the reference signal (cyan color), PDCCH (yellow color), and

PCFICH (purple color), all of which use QPSK modulation. It also contains PHICH

(bright red color) which uses BPSK modulation.

Table 24. Measuring EVM on specific symbols


Change the measurement interval and

measurement offset to measure symbol

#0 i.e. Reference Signal and PDCCH

Meas Setup > Demod Properties > Time (tab)

Change Measurement Interval to 0 Slots. This will automati-

cally set the measurement interval to 1 symbol-time. Therefore

analysis will be made on 1st symbol (i.e. symbol #0).

Click Close

See Figure 19 below

Change the measurement interval and

measurement offset to measure the

7th symbol (i.e. symbol # 6) which

contains the PSCH and PDSCH

Meas Setup > Demod Properties > Time (tab)

Change Measurement Offset to 6 symbol-times. This will

move the "measurement window" to measure the 7th symbol (i.e.

symbol #6), which is P-SS plus user data.

Click Close

Change Trace B to show Spectrum

Double click Trace B title (B: Ch1 OFDM RB Error Mag

Spectrum)

In the Data: column select Spectrum

Click OK

Auto Scale Trace B Right click Trace B and select Y Auto Scale

Change Trace E to show CCDF

Double click the Trace E title (E: Ch1 OFDM RB Error Mag Time) In the Data: column select CCDFClick OK

Restart the measurementClick the Restart button.

See Figure 20 below

33

Figure 20. Single symbol measurement showing EVM for Symbol #0.

Figure 21 below shows an analysis of Symbol #6, the last symbol in the 1st

time slot.

Figure 21. Single symbol measurement showing EVM and CCDF analysis for Symbol #6.

34

Here, all measurements are made for symbol #6 which contains the P-SS and all

of the user data channels (PDSCH’s). The P-SS uses a Zadoff-Chu sequence, as

shown by the circle (pink) on the constellation display. The PDSCH channels use

QPSK, 16QAM, and 64 QAM modulation formats. Notice the spectrum display

in Trace B. It shows the spectrum of only the P-SS channel (which occupy the

center 72 subcarriers) and the PDCCH channels (which occupy the 1st 9 RB’s or

108 subcarriers).

The Complementary Cumulative Density Function (CCDF) shows what percentage

of signals are a given amount (in dB) above the RMS average of the signal in

the Measurement Interval.

Trace E shows a gated CCDF measurement; i.e. it is the CCDF of symbol #6 which

contains the P-SS and PDSCH only. While we are only looking at the CCDF of

symbol #6 in this example, we could just as easily make a CCDF measurement

across a time slot or subframe. That would allow us to characterize distortion

across an LTE frame. Some of the LTE timeslots and subframes contain more

channels and signals compared to others. For example, subframe 1 of an LTE

frame contains all of the control channels and signals as well as payload data,

whereas subframe 2 is mostly payload data. Making CCDF measurements

on a symbol, slot or subframe basis allow us to see which symbols, slots or

subframes introduce the most distortion.

For more information on CCDF measurements, see the 89600 VSA Help text.

MIMO analysisThe 89600 LTE analysis software also has the capability to analyze transmit

diversity encoded MIMO signals. Table 25 explains how to recall the proper

recording and setup file for MIMO analysis.

Table 25. Recall a single antenna MIMO signal


Preset the software


Note: Using Preset All will cause all saved user state information

to be lost. If this is a concern, save the current state before using

Preset All. Click File > Save > Setup

Recall the recoding of a 5 MHz LTE

downlink MIMO signal

File >Recall > Recall Recording

(c:\Program Files\Agilent\89600 VSA\Help\Signals)

Select the MIMO downlink recordingSelect LTE_DL_5MHz_4Ant_Port0_v820.sdf

Click Open

Recall the appropriate setup fileFile > Recall > Recall Setup


Select the MIMO downlink setup fileSelect LTE_DL_5MHz_4Ant_Port0_v820.set

Click Open

Restart the recording Click the Restart button.

35

Your display should look similar to Figure 22 below.

Figure 22. LTE downlink MIMO signal.

Trace B shows the Equalizer Channel Frequency Response as decoded by the

Matrix Decoder for each transmitter port. This measures the equalizer frequency

response for the analyzed signal. In this case, there is only one port that is trans-

mitting data, thus showing the single line in the trace.

Trace C displays information about the antenna port transmissions detected

by the demodulator. The first column lists the various measurement results for

each antenna port. One of the antenna ports is always selected as the refer-

ence antenna port. In this case, since we only have one antenna port transmit-

ting data, it is considered to be the reference antenna port. This is why RSPwr,

RSTiming, RSPhase, RSSymClk and RSFreq are set to zero. RSEVM and RSCTE

are the two metrics that cannot be zero because they are error values specific to

each antenna port. In a signal with multiple antenna ports, these metrics would

report information relative to the reference antenna port. Below is a list and

description of the table results found in the MIMO Info table.

RSPwr (dB): Average (RMS) RS Signal Power

RSEVM (%rms or dB): Average (RMS) RS EVM. Units are determined by the

Report EVM in dB parameter

RSCTE (%rms): Average (RMS) RS Common Tracking Error

RSTiming (seconds): RS timing error

RSPhase (degrees): Average (RMS) RS phase error

RSSymClk (ppm): Average RS symbol clock error

RSFreq (Hz): RS frequency shift error

36

Follow the steps on the table below to recall a signal that utilizes multiple

antennas.

Your display should look similar to Figure 23 below.

Figure 23. LTE downlink MIMO signal with multiple ports.

This recording is of a signal that utilizes four antenna ports. Due to window size

constraints, Figure 23 does not show metrics for the fourth antenna port. But

as we discussed earlier, the values for each antenna port, except RSEVM and

RSCTE, are relative to the reference antenna port. In this case, it is Port 0.

Now that you have made a variety of downlink measurements, let's examine LTE

uplink signals as well.

Table 26. Recall a multi-antenna MIMO signal


Preset the software





Recall the recoding of a 5 MHz LTE

downlink MIMO signal

File >Recall > Recall Recording


Select the MIMO downlink recordingSelect LTE_DL_5MHz_4Ant_v820.sdf

Click Open

Recall the appropriate setup fileFile > Recall > Recall Setup


Select the MIMO downlink setup fileSelect LTE_DL_5MHz_4Ant_ v820.set

Click Open

Restart the recording Click the Restart button.

37

When you are fi nished, your display should look similar to the one shown in

Figure 24.

LTE uplink signal analysis

The 89600 LTE analysis software provides both uplink and downlink LTE signal

analysis in a single option. Thus, the uplink analysis has similar features and

capabilities as downlink analysis. Because of that, we'll focus next on what

is unique to uplink measurements.

The most significant differences include:

1) Uplink RB auto-detection behavior

2) User must choose to display either PUSCH or PUCCH

Let's quickly examine an uplink signal and the measurements and displays to

help understand these differences.

Table 27. Uplink signal analysis


Preset the software





Note: The Menu/Toolbars, Display Appearance, and

User Color Map may also be saved in a similar way.

Go to the default signal directoryFile > Recall > Recall Recording


Select a 5 MHz LTE uplink recording Select LTE_UL_Multi_5MHz_v820.sdf

Click Open

Recall the appropriate setup file

File > Recall > Recall Setup


Select LTE_UL_5Mhz_v820.set

Click Open

Change display layout to Grid 3x2 Select Grid 3x2 option from the layout drop down menu

Change Trace D to show Frame

Summary

Double click Trace D title (D: Ch1 Error Summary)


Click OK

Change Trace F to show Error

Summary

Double click Trace F title (F: Ch1 Frame Summary)

In the Data: column select Error Summary

Click OK

Start the measurement Click (toolbar, left side)

Auto scale Traces A, B, C and E Right click on each trace and click Y Auto Scale

38

Figure 24. Uplink signal analysis, showing the combined time domain and

frequency domain composite "constellation."

Trace A: For uplink signals, the demodulation RS (pilot) is in the frequency

domain but the uplink data channel (PUSCH) is in the time domain due to

SC-FDMA scheme used for uplink data channels. The I/Q Meas trace therefore

overlays the time domain and frequency domain display to show both data

channel as well as the DM-RS (pilot) constellation diagram. The DM-RS (pilot)

uses a Zadoff-Chu sequence and is shown by the circle (cyan color). The PUSCH

channels in this example use QPSK and 16 QAM modulation, as shown by the 2x2

and 4x4 constellations, respectively.

Trace B: Trace B shows a combination of PUSCH and PUCCH channels that are

transmitted. For this recording, the signal is defined to have two users: User 1

and User 2. User 1 allocates all 20 slots for RB 5-9 for PUSCH with a modulation

type of QPSK. User 2 allocates all 20 slots for RB 15-19 for PUSCH with a

modulation type of 16QAM. These are the broad, center two spectral peaks. The

narrow, outer spectral peaks are transmitting PUCCH for RB 0 and RB 24. Both

users’ allocations are equally dispersed on both RB 0 and RB 24. Note: Under the

Profile (tab), you will only see User 1 shown. This is because the Auto detection

function has combined the two users and distinguished them by their modulation

type.

Trace E: Note that this trace clearly shows the DM-RS (pilot), cyan color,

occupying symbol #3 of each timeslot.

39

Trace F: You may notice that the Trace F Error Summary table in the figure is

missing some of the table elements. This is due to a smaller window size used in

this demo guide, and can be fully seen by expanding the window size. Figure 25

below shows the Error Summary table with full content. For explanations of all

table results, please refer to the Help text.

Figure 25. Error Summary table

Note: Uplink RB Auto-detect works best when a unique sync slot is identified.

This is due to the fact that there are no sync signals for UL, and this unique sync

slot allows the analysis software to acquire absolute radio frame slot number

alignment, which in turn supports measurement of any individual slot and symbol

within the UL radio frame.

As mentioned earlier, one of the most significant differences between uplink

and downlink signal analysis is for uplink measurements, the control (PUCCH)

and shared (PUSCH) channel cannot be analyzed simultaneously. Let’s explore

this difference by switching between the control (PUCCH) and shared (PUSCH)

channels.

Table 28. Single channel uplink signal analysis


Go to the Profile tab under demodula-

tion propertiesMeasSetup > Demod Properties> Profile (tab)

Expand information under User 1 Click the plus box adjacent to User_01 to expand list of channels

Select PUCCH for analysis

Click the PUCCH box

Click the PUCCH DMRS box

Note how the PUSCH select boxes are automatically unchecked

Click Close

Auto scale Traces B, C, and E

Right Click Trace B and select Y Auto Scale

Do the same for Traces C and E

See Figure 26 below

40

Figure 26. Uplink signal analysis showing PUCCH transmitted.

Trace C: As predicted earlier, since PUCCH has been selected for analysis,

Trace C now shows EVM results for RB 0 and RB 24. You can see that this

trace correlates to Trace B by noticing the coupled markers between the two.

You can switch between PUCCH and PUSCH by selecting the appropriate check

boxes next to the channel names.

41

Summary

Glossary

The 89600 VSA software with Option BHD for LTE modulation analysis provides

the tools necessary to measure and troubleshoot 3GPP LTE uplink and downlink

signals. Comprehensive error measurements allow you to look at error versus

subcarrier, symbol, resource block or slot. Sophisticated analysis is also possible

when focusing on individual channels, symbols, or time. The addition of new

MIMO analysis capabilities continues to enhance the existing advanced digital

demodulation techniques. The 89600 VSA software is supported through a

multitude of platforms, including oscilloscopes, spectrum analyzers, etc. From

baseband to RF, simulation to antenna, it provides the greatest versatility for all

measurements in all possible domains. No matter how simple or complex the

measurement, 89600 VSA software meets all your trouble-shooting needs.

3GPP 3rd Generation Partnership Project

3G 3rd Generation

AMC Adaptive Modulation and Coding

ACK Acknowledgement

CAZAC Constant Amplitude Zero Auto Correlation

CCDF Complementary Cumulative Distribution Function

CP Cyclic Prefix

DL Downlink (base station to subscriber transmission)

DM RS Demodulation Reference Signal

DFTS-OFDM Discrete Fourier Transform Spread - Orthogonal

Frequency Division Multiplexing

EVM Error Vector Magnitude

FDD Frequency Division Duplex

HSDPA High Speed Downlink Packet Access

HSPA High Speed Packet Access

LTE Long Term Evolution

MBMS Multimedia Broadcast Multicast Service

MIMO Multiple Input Multiple Output

NACK Negative Acknowledgement

OFDM Orthogonal Frequency Division Multiplexing

OFDMA Orthogonal Frequency Division Multiple Access

OS Orthogonal Sequence

PAPR Peak-to-Average Power Ratio

P-BCH Physical Broadcast Channel

PCFICH Physical Control Format Indicator Channel

PDCCH Physical Downlink Control Channel

PDSCH Physical Downlink Shared Channel

PHICH Physical Hybrid ARQ Indicator Channel

PMCH Physical Multicast Channel

PRACH Physical Random Access Channel

PRS Pseudo Random Sequence

P-SS Primary - Synchronization Signal

PUCCH Physical Uplink Control Channel

PUSCH Physical Uplink Shared Channel

QAM Quadrature Amplitude Modulation

QPSK Quadrature Phase Shift Keying

RB Resource Block

RS Reference Signal (pilot)

SC-FDMA Single Carrier - Frequency Division Multiple Access

S-SS Secondary - Synchronization Signal

TDD Time Division Duplex

TrCH Transport Channel

TTI Transmission Time Interval

UL Uplink (Subscriber to base station transmission)

W-CDMA Wideband - Code Division Multiple Access

42

89601A Vector signal analysis software

Note: For initial purchases including Option 200, a discount

item, D12, will be applied to provide a discount corresponding

to 1 year of software update service.

Options Option 200 required

89601A-200 Basic vector signal analysis software

89601A-012 12 months bundled software update subscription service

(qualifi es for 12 month discount)

89601A-024 24 months bundled software update subscription service


89601A-300 Hardware connectivity

89601A-AYA Flexible modulation analysis

89601A-B7N 3G modulation analysis bundle

89601A-B7T cdma2000/1xEV-DV modulation analysis

89601A-B7U W-CDMA/HSPA modulation analysis

89601A-B7W 1xEV-DO modulation analysis

89601A-B7X TD-SCDMA modulation analysis

89601A-B7R WLAN modulation analysis

89601A-B7S IEEE 802.16-2004 OFDM modulation analysis

89601A-B7Y IEEE 802.16 OFDMA modulation analysis

89601A-B7Z IEEE 802.11n modulation analysis

89601A-BHA TETRA modulation analysis and test

89601A-BHB MB-OFDM ultra-wideband modulation analysis

89601A-BHC RFID modulation analysis

89601A-BHD LTE modulation analysis

89601A-105 Dynamic link to EEsof/ADS

89601A-106 Dynamic link to The MathWorks Simulink Model-Based Design

Ordering Information

43

89601AN Vector signal analysis software (fl oating license for 1 server)

Note: For initial purchases including Option 200, a discount

item, D12, will be applied to provide a discount corresponding

to 1 year of software update service.

Options Note: multiple quantities of one option may be ordered per

each server. Option 200 required. Every user must have

Option 200, so the maximum quantity of any option may not

exceed the quantity of Option 200. For multiple servers, order

additional 89601AN.

89601AN-012 12 months bundled software update subscription service


89601AN-024 24 months bundled software update subscription service


89601AN-200 Basic vector signal analysis software

89601AN-300 Hardware connectivity

89601AN-AYA Flexible modulation analysis

89601AN-B7N 3G modulation analysis bundle

89601AN-B7T cdma2000/1xEV-DV modulation analysis

89601AN-B7U W-CDMA/HSPA modulation analysis

89601AN-B7W 1xEV-DO modulation analysis

89601AN-B7X TD-SCDMA modulation analysis

89601AN-B7R WLAN modulation analysis

89601AN-B7S IEEE 802.16-2004 OFDM modulation analysis

89601AN-B7Y IEEE 802.16 OFDMA modulation analysis

89601AN-B7Z IEEE 802.11n MIMO modulation analysis

89601AN-BHA TEDS modulation analysis and test

89601AN-BHB MB-OFDM ultra-wideband modulation analysis

89601AN-BHC RFID modulation analysis

89601AN-BHD LTE modulation analysis

89601AN-105 Dynamic link to EEsof/ADS

89601AN-106 Dynamic link to The MathWorks Simulink Model-Based Design

Ordering information (continued)

44

Related Literature

Web Resourses

89600 Series Vector Signal Analysis Software,

Technical Overview, 5989-1679EN

89600 Series Vector Signal Analysis 89601A/89601AN/89601N12 Software,

Data Sheet, 5989-1786EN

89600 Vector Signal Analysis demo software,

CD, 5980-1989E

Understanding the Intricacies of LTE, LTE poster, 5989-7646EN

Move Forward to What's Possible in LTE,

Agilent's LTE Solutions Guide, 5989-7817EN

Hardware Measurement Platforms for the Agilent 89600 Series Vector Signal

Analysis Software, Data Sheet, 5989-1753EN

89600S Series VXI-based Vector Signal Analyzers,

Configuration Guide, 5968-9350E

3GPP Long Term Evolution: System Overview, Product Development, and Test

Challenges, 5989-8139EN

For additional information, visit:

www.agilent.com/find/89600

www.agilent.com/find/LTE

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calibration procedures, automated

repair diagnostics and genuine parts.

You will always have the utmost

confi dence in your measurements.

Agilent offers a wide range of ad-

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For more information on repair and

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For more information on Agilent Technologies’

products, applications or services, please

contact your local Agilent office. The

complete list is available at:

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Canada (877) 894-4414

Latin America 305 269 7500

United States (800) 829-4444

Asia Pacifi c

Australia 1 800 629 485

China 800 810 0189

Hong Kong 800 938 693

India 1 800 112 929

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Korea 080 769 0800

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Singapore 1 800 375 8100

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Thailand 1 800 226 008

Europe & Middle East

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Belgium 32 (0) 2 404 93 40

Denmark 45 70 13 15 15

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*0.125 €/minute

Germany 07031 464 6333**

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Israel 972-3-9288-504/544

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Revised: July 17, 2008

Product specifi cations and descriptions

in this document subject to change

without notice.

© Agilent Technologies, Inc. 2008

Printed in USA, September 15, 2008

5989-7698EN

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