Agilent Vector Signal Analysis Software Option BHD 3GPP LTE Modulation Analysis. Technical Overview and Self-Guided Demonstration

Transcription

1 Agilent Vector Signal Analysis Software Option BHD 3GPP LTE Modulation Analysis Technical Overview and Self-Guided Demonstration

2 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 Overview of the parameters under Format tab Overview of the parameters under Profi le tab Overview of the parameters under LTE Allocation Editor window Overview of the parameters under LTE Downlink Control Channel Properties window Advanced Digital Demodulation Selective channel analysis...30 EVM for data channels...30 Analyzing individual symbols MIMO analysis...34 LTE uplink signal analysis...37 Summary Glossary Ordering Information...42 Related Literature...44 Web Resources...44

3 Introduction 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 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) , and in the LTE requirements document, TR 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 EN. Before beginning our demonstration, here is some useful information to help explain the LTE downlink and uplink channels and signals. 3

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 name Modulation format Purpose PBCH Physical Broadcast Channel QPSK Carries cell-specific information PDCCH Physical Downlink Control Channel QPSK Scheduling, ACK/NACK PDSCH Physical Downlink Shared Channel QPSK 16QAM 64QAM Payload PMCH PCFICH PHICH DL signals P-SS S-SS RS Physical Multicast Channel Physical Control Format Indicator Channel Physical Hybrid ARQ Indicator Channel Full name Primary Synchronization Signal Secondary Synchronization Signal Reference Signal (Pilot) QPSK 16QAM 64QAM QPSK BPSK with I & Q CDM Modulation sequence One of 3 Zadoff-Chu sequences Two 31-bit M-sequences (binary) Complex I+jQ pseudo random sequence (length-31 Gold sequence) derived from cell ID Payload for Multimedia Broadcast Multicast Service (MBMS) Carries information about the number of OFDM symbols (1, 2 or 3) used for transmission of PDCCHs in a sub-frame. Carries the hybrid-arq ACK/NAK Purpose Used for cell search and identifi cation by the UE. Carries part of the cell ID (one of 3 orthogonal sequences). Used for cell search and identifi cation by the UE. Carries the remainder of the cell ID (one of 168 binary sequences). Used for DL channel estimation. Exact sequence derived from cell ID, (one of 3*168=504). 4

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 name Modulation format Purpose PRACH Physical Random Access Channel u th root Zadoff-Chu Call setup PUCCH Physical Uplink Control Channel BPSK, QPSK Scheduling, ACK/NACK PUSCH Physical Uplink Shared Channel QPSK 16QAM 64QAM Payload UL signals DM-RS Full name Demodulation Reference Signal Modulation sequence u th root Zadoff-Chu S-RS Sounding Reference Signal Zadoff-Chu Purpose Used for synchronization to the UE and UL channel estimation Used to monitor propagation conditions with UE. 5

6 Measurement and Troubleshooting Sequence 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. Spectrum and time domain measurments Get basics right, fi nd major problems Basic digital demodulation Signal quality numbers, constellation, basic error vector measurement Advanced digital demodulation Find specifi c problems and causes Step 1: Spectrum and time domain measurments These 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 demodulation These 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 demodulation These 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 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 VSA software demo CD. 6

7 Setting up the demonstration Table 3 describes the minimum hardware required to run the VSA software. Table 3. System requirements Characteristic CPU Empty slots (desktop) Empty slots (laptop) Microsoft Windows XP Professional 600 MHz Pentium or AMD-K6 > 600 MHz (> 2 GHz recommended) 1 PCI-bus slot (Two recommended VXI hardware only) 1 CardBus Type II slot (Integrated FireWire recommended for VXI hardware only) Microsoft Windows Vista Business, Enterprise, or Ultimate 1 GHz 32-bit (x86) (> 2 GHz recommended) 1 PCI-bus slot (Two recommended VXI hardware only) 1 CardBus Type II slot (Integrated FireWire recommended for VXI hardware 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 Additional drives Interface support CD-ROM to load the software; license transfer requires a 3.5 inch floppy disk drive, network access, or USB memory stick LAN, GPIB, USB, or FireWire 1 interface (VXI HW only) CD-ROM to load the software; license transfer requires a 3.5 inch floppy disk drive, network access, or USB memory stick LAN, GPIB, USB, or FireWire 1 interface (VXI HW only) 1. For a list of supported IEEE-1394 (FireWire) interfaces, visit 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 4 describes the 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 Table 4. Software requirements Version version 9.00 or higher (89601A, 89601AN, 89601N12) Options BHD (89601A, 89601AN only) Basic vector signal analysis Hardware connectivity (required only if using measurement hardware) LTE modulation analysis Table 5. Recall the signal 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 LTE_DL_5MHz_v820.sdf Select the downlink recording Click Open Start the measurement Click (toolbar, left side) Auto scale Trace A Auto scale Trace B Right click Trace A Select Y Auto Scale Right click Trace B Select Y Auto Scale 7

8 Spectrum and time domain measurments Get basics right, fi nd major problems Basic digital demodulation Signal quality numbers, constellation, basic error vector measurement Advanced digital demodulation Find specifi c problems and causes 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. Auto scale Trace A and Trace B Meas Setup > ResBW > ResBW Mode > Arbitrary (pull down menu) Frequency Points >Auto Time (tab) > Main Time Length > 900 usec Click Close Right click in Trace A. Click Y Auto Scale Right click in Trace B. Click Y Auto Scale Note: This first figure 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 figures will not display them. You can toggle them on/off by clicking Display > Appearance > Window 8 Figure 1. Time and spectrum display.

9 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. Table 7. Measuring OBW Display OBW trace Activate OBW Summary table Right-click Trace A Select Show OBW 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. 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. Right-click Trace A De-select Show OBW 9

10 The band power marker feature measures the power of the modulated signal, or channel power, by integrating over a specified bandwidth in the frequency domain. Table 9. Setting up band power marker Select the band power marker tool Drop the band power marker on Trace A Expand the band power marker Click Markers > Tools > Band Power (Or, alternatively, you can click the band power marker button on the menu toolbar) On Trace A, move the mouse to the center frequency of the band to be measured. Click to drop the 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 rightclick 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. 10

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). Activate spectrum display for Trace B Enable the spectrogram display on Trace A Click MeasSetup > Time Set the Main Time Length to 100 usec Set Max Overlap (Avg Off) to 95% Click Close Double click the Trace B title (B: Ch1 Main Time) In the Data: column select Spectrum Right-click Trace A. Select Show Spectrogram Pause the measurement to temporarily halt playback Click the pause/continue button in the toolbar Click on the color bar on the left hand side of the trace (See Figure 4 for reference). 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/spectrogram 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. 11

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 number 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. Re-position the white spectrogram marker so that it is in line with the spots. Place the spectrogram marker on the spots Enable the main trace marker Click on the diamond icon near the top of the menu toolbar Place marker on left spot Add an offset marker Move offset to marker Click and drag offset to right spot Click on the trace where the spot is located to drop a marker on that position Right click on the trace and select Show Offset Right click on the trace and select Move Offset to Mkr Click and drag the vertical white line over to the right until the marker is in line with the other spot 12

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. 13

14 Table 12. Using spectrogram markers to find center frequency Temporarily turn off spectrogram display Increase main time length to obtain a more defined signal Adjust Y-axis settings Adjust the span Right click anywhere on Trace A De-select Show Spectrogram MeasSetup > Time Set the Main Time Length to 900 usec Click Close 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 Double click on the Span value for Trace A (lower right corner of trace) Set the value to 5 MHz Click the Restart button Restart the spectrogram Right click anywhere in Trace A and check Show Spectrogram Note: you should see a distinct line in the center of the spectrogram. If you do not, adjust the color bar as previously instructed until it is more noticeable. Click the Pause button to pause playback. Zoom in on center Place marker on center line 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. Using 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, confirming 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 figure below. Figure 5. Spectrogram display showing center frequency subcarrier. 14 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 Spectrum and time domain measurments Get basics right, fi nd major problems Basic digital demodulation Signal quality numbers, constellation, basic error vector measurement Advanced digital demodulation Find specifi c problems and causes 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 Display > Layout > Grid 2x2 (Or alternatively, Click on the drop down menu near the top of the menu. Change the display to show four traces in a 2x2 grid Select the LTE demodulator Set up the demodulator for downlink analysis See below for descriptions of each tab and the parameters available Select Grid 2x2 from the available options.) MeasSetup > Demodulator > 3G Cellular > LTE 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. Go to Format (tab) Make sure Auto is selected under Cell ID Select automatic detection of Resource Blocks (RB) Begin demodulation Go to Profile (tab) Check RB Auto Detect (Note: This setting is checked by default) Click Close Press Restart Your display should look similar to Figure 6 15

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 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. 16 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

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. 18

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 coupled 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 constellation 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. 19

20 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 measurements, 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. Table 14. Display frame summary information Change Trace C to show the frame summary Auto scale Trace B Double click the Trace C trace title (C: Ch1 OFDM Err Vect Spectrum) In the Data: column select Frame Summary Right click on Trace B Select Y Auto Scale 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. 20

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 VSA is its error analysis. Here we'll look at the wide range of built-in error traces available to you. 21

22 Table 15. View the multiple EVM traces supported Change the display to show six traces Change Trace B to show EVM per Resource Block (RB) Change Trace C to show EVM per subcarrier Change Trace D to show the frame summary Change Trace E to show EVM per time slot Change Trace F to show EVM per symbol Auto scale all traces (except Trace D) Select Grid 3x2 from the layout drop down menu Double click the Trace B title (B: Ch1 Spectrum) In the Data: column select RB Error Mag Spectrum Double click the Trace C title (C: Ch1 Frame Summary) In the Data: column select Error Vector Spectrum Double click the Trace D title (D: Ch1 Error Summary) In the Data: column select Frame Summary Double click the Trace E title (E: Ch1 OFDM Err Vect Time) In the Data: column select RB Error Mag Time Double click the Trace F title (F: Ch1 Frame Summary) In the Data: column select Error Vector Time Right click on each trace and click Y Auto Scale Your display should be similar to what is shown in Figure 12. Figure 12. LTE error traces. 22

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 higher 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. 23

24 Table 16. Reduce the EVM by adjusting the EVM averaging window Turn off Moving Average Filter Choose EVM Window Center Click MeasSetup > Demod Properties > Advanced (tab) and de-select Moving Avg Filter Select EVM Window Center under the Symbol Timing Adjust options 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 17. Return to original setting Turn on Moving Average Filter Choose Max of EVM Window Start / End Click MeasSetup > Demod Properties > Advanced (tab) and select Moving Avg Filter Select Max of EVM Window Start / End under the Symbol Timing Adjust options Click Close 24

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. Table 18. Power per RB and Slot Change Trace C to show Power per RB Change the y-axis scale of Trace C to db Change Trace F to show power per Slot Change the y-axis scale of Trace F to db Double click the Trace C title (C: Ch1 OFDM Err Vect Spectrum) In the Data: column select RB Power Spectrum Double click Lin Mag on y-axis of Trace C In the Format drop down menu, select Log Mag (db) Double click the Trace F title (F: Ch1 OFDM Err Vect Time) In the Data: column select RB Power Time Double click Lin Mag on y-axis of Trace F In the Format drop down menu, select Log Mag (db) 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. 25

26 Advanced Digital Demodulation Spectrum and time domain measurments Get basics right, fi nd major problems Basic digital demodulation Signal quality numbers, constellation, basic error vector measurement Advanced digital demodulation Find specifi c problems and causes 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. Table 19. Selective slot analysis Change Trace C to show EVM per subcarrier Change Trace F to show EVM per symbol Double click the Trace C title (C: Ch1 OFDM RB Power Spectrum) In the Data: column select Error Vector Spectrum Double click the Trace F title (F: Ch1 OFDM RB Power Time) In the Data: column select Error Vector Time Markers > Tools > Select area or use the select area box from the tool bar Zoom on slot #0 (i.e. 1st 7 symbols) of the EVM per symbol trace - Trace F Auto scale Trace F Return mouse cursor to pointer 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 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 Right click on Trace F and click Y Auto Scale Click on the Pointer button in the toolbar Your display for Trace F should look similar to the one shown in Figure

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 occurrence 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. 27

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. Table 20. Marker coupling Turn off the RMS trace (white line across Traces B, C, E and F) Auto scale all traces (except Trace D) Change the amplitude of the P-SS channel to show a different value Couple markers between displays Place marker on P-SS channel Click on Trace B. Under Trace > Digital Demod > uncheck Show 2D Avg Line Click Close Do the same on Traces C, E and F Right click on each trace and click Y Auto Scale 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 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 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 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. 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. 28

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 Change the value of Power Boost for P-SS back to original value 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. MeasSetup > Demod Properties > Profile (tab) 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 Close 29

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: Table 22. Selecting specific channels for analysis Turn off control channels and signals from the analysis MeasSetup > Demod Properties > Profile (tab) Un-check P-SS, S-SS, PBCH, PCFICH, PHICH, PDCCH, and RS Click Close Your display should be similar to the one shown in Figure 17. Figure 17. EVM analysis of data channels only. 30

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. Table 23. Turn the control channel analysis back on Turn the analysis of control channels and signals back to ON MeasSetup > Demod Properties > Profile (tab) Select P-SS, S-SS, PBCH, PCFICH, PHICH, PDCCH, and RS Click Close 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. Figure 18. Demodulation Time tab used to adjust analysis region. For more information on each of these parameters, see the Help Text. analysis start boundary result length measurement interval DL: frame start 0 ms = UL: beginning of first slot measurement offset Time 0 ms = trigger Search Time Raw Main Time Figure 19. LTE analysis regions. 31

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. Table 24. Measuring EVM on specific symbols Change the measurement interval and measurement offset to measure symbol #0 i.e. Reference Signal and PDCCH Change the measurement interval and measurement offset to measure the 7th symbol (i.e. symbol # 6) which contains the PSCH and PDSCH Change Trace B to show Spectrum Auto Scale Trace B Change Trace E to show CCDF Meas Setup > Demod Properties > Time (tab) Change Measurement Interval to 0 Slots. This will automatically 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 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 Double click Trace B title (B: Ch1 OFDM RB Error Mag Spectrum) In the Data: column select Spectrum Right click Trace B and select Y Auto Scale Double click the Trace E title (E: Ch1 OFDM RB Error Mag Time) In the Data: column select CCDF Restart the measurement Click the Restart See Figure 20 below button. 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. 32

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. 33

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 VSA Help text. MIMO analysis The 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 Recall the recoding of a 5 MHz LTE downlink MIMO signal Select the MIMO downlink recording Recall the appropriate setup file Select the MIMO downlink setup file 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 File >Recall > Recall Recording (c:\program Files\Agilent\89600 VSA\Help\Signals) Select LTE_DL_5MHz_4Ant_Port0_v820.sdf Click Open File > Recall > Recall Setup (c:\program Files\Agilent\89600 VSA\Help\Signals) Select LTE_DL_5MHz_4Ant_Port0_v820.set Click Open Restart the recording Click the Restart button. 34

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 transmitting 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 reference antenna port. In this case, since we only have one antenna port transmitting 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 35

36 Follow the steps on the table below to recall a signal that utilizes multiple antennas. Table 26. Recall a multi-antenna MIMO signal Preset the software Recall the recoding of a 5 MHz LTE downlink MIMO signal Select the MIMO downlink recording Recall the appropriate setup file Select the MIMO downlink setup file 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 File >Recall > Recall Recording (c:\program Files\Agilent\89600 VSA\Help\Signals) Select LTE_DL_5MHz_4Ant_v820.sdf Click Open File > Recall > Recall Setup (c:\program Files\Agilent\89600 VSA\Help\Signals) Select LTE_DL_5MHz_4Ant_ v820.set Click Open Restart the recording Click the Restart button. 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. 36

37 LTE uplink signal analysis The 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 File > Preset > Preset All 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 Note: The Menu/Toolbars, Display Appearance, and User Color Map may also be saved in a similar way. Go to the default signal directory Select a 5 MHz LTE uplink recording Recall the appropriate setup file Change display layout to Grid 3x2 Change Trace D to show Frame Summary Change Trace F to show Error Summary File > Recall > Recall Recording (c:\program Files\Agilent\89600 VSA\Help\Signals) Select LTE_UL_Multi_5MHz_v820.sdf Click Open File > Recall > Recall Setup (c:\program Files\Agilent\89600 VSA\Help\Signals) Select LTE_UL_5Mhz_v820.set Click Open Select Grid 3x2 option from the layout drop down menu Double click Trace D title (D: Ch1 Error Summary) In the Data: column select Frame Summary Double click Trace F title (F: Ch1 Frame Summary) In the Data: column select Error Summary 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 When you are fi nished, your display should look similar to the one shown in Figure

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 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. 38

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 demodulation properties Expand information under User 1 Select PUCCH for analysis Auto scale Traces B, C, and E MeasSetup > Demod Properties> Profile (tab) Click the plus box adjacent to User_01 to expand list of channels Click the PUCCH box Click the PUCCH DMRS box Note how the PUSCH select boxes are automatically unchecked Click Close Right Click Trace B and select Y Auto Scale Do the same for Traces C and E See Figure 26 below 39

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. 40