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MSR - Generating a Library Waveform

A Library Waveform is an enhanced carrier type specifically designed for Multi-Standard Radio (MSR). The Waveform Library allows you to manage imported waveforms with resampling and filtering already applied. This enables faster summing of carriers when you change offset frequency or power by eliminating redundant resampling and filtering processes. Generation of Library Waveforms requires Option Jxx.

The initial process for library waveforms is the same as described in the MSR - Generating a Waveform topic and is repeated here for your convenience. This process enables you to generate library waveforms using exported waveforms. Refer to the Using the Waveform Library Manager.

If desired, you can use Imported Waveforms in combination with your Library Waveforms in the Waveform Setup node, but there will be an increase in the time required to generate the waveform. To avoid longer waveform generation times, add any additional Imported Waveforms to the Waveform Library folder using the Closed

Tools dropdown before generating your waveforms in the Waveform Setup node.

Below is a list of the Signal Studio waveforms that can be imported into the MSR feature for LTE signals.

N7600B Signal Studio for W-CDMA/HSPA+
N7601B Signal Studio for cdma2000/1xEV-DO
N7602B Signal Studio for GSM/EDGE/Evo
N7612B Signal Studio for TD-SCDMA/HSDPA
N7617B Signal Studio for WLAN^a
N7624B Signal Studio for LTE/LTE-Advanced FDD (non-MSR waveforms)^b
N7625B Signal Studio for LTE/LTE-Advanced TDD (non-MSR waveforms)^c

Supports high-resolution waveform export, providing better signal quality in the resulting MSR waveform. Requires minor enhancement update (MEU) N7617B-U02 or greater to playback MSR waveforms using the component high-resolution waveform.
Supports high-resolution waveform import and export, providing better signal quality in the resulting MSR waveform. Requires minor enhancement update (MEU) N7624B-U04 or greater to playback MSR waveforms using the component high-resolution waveform.
Supports high-resolution waveform import and export, providing better signal quality in the resulting MSR waveform. Requires minor enhancement update (MEU) N7625B-U04 or greater to playback MSR waveforms using the component high-resolution waveform.

Using the Waveform Library and Library Waveforms:

Before using library waveforms you must first import a waveform () into the Waveform Library Folder from your exported waveforms folder. Refer to the procedure below.

To minimize the waveform generation time, all the Library Waveforms selected to be generated simultaneously should have common sampling ratios. Typically, 30.72 MHz or 61.44 MHz works well. An oversampling rate of 61.44 MHz works best when Frequency Offset values other than 0 are used. To do this, use the Waveform Manager to import your waveforms (

) and select a common sampling rate that corresponds to the different waveforms that are to be generated together in the Waveform Setup node.

Requirements

Licensing

Library Waveforms that are used with the MSR feature must have proper Signal Studio licensing. The MSR waveform comprises all the license requirements for each of the component waveform-types used.

The maximum number of component waveforms that can be imported into an MSR composite waveform is limited by the number of unique licenses required to generate the MSR waveform. For example:

3 Basic waveforms + 1 W-CDMA waveform = 4 waveform component licenses

Typically, up to approximately 11 waveforms can be used in a MSR waveform. If the number of waveforms exceeds the MSR feature's limits, an Closed error message will be displayed.

If your equipment setup requires an E4438C, Option N7625B-Hxx is required. E4438C with Options 400, 401, 402, and 411 are not a substitute for Option N7625B-Hxx licensing for the MSR feature.(Additionally, to use the Waveform Library Manager feature with your Basic MSR LTE and LTE-A waveforms, Options N7625B-Jxx and N7625B-Txx are required.) Using any waveform with the N7625B's MSR feature requires all of that imported waveform's licensing.

Connectivity

To use the MSR feature, you must have the correct waveform options and the correct instrument connectivity.

Example: Using a Basic N7602B waveform with the N7625B's MSR feature requires connectivity with an MXG signal generator (Options N7602B-3xx and N7625B-3xx) and the basic waveform options (Option N7602B-Exx and N7625B-Hxx). Additionally, using the Waveform Library Manager with your MSR LTE and LTE-A waveforms requires Option N7625B-Jxx.

For additional hardware requirements, refer to the "Hardware and System Requirements for the Multi-Standard Radio (MSR)" in the System Requirements.

Memory

Each waveform sample point requires about 25 bytes of hard drive space, so a 1 GSa waveform requires 25 GB of available drive space.

MSR and Library Waveform Generation Procedure

If you want to use high-resolution component waveforms to generate an MSR waveform, refer to Using High-Resolution Waveforms for MSR first.

Using the N7600B, N7601B, N7602B, N7612B, N7617B, N7624B or N7625B software, export each of the required component waveforms using the exported waveform settings below. Refer to your component waveform's help for more information.

Waveform Type	Waveform Length (Recommended) ^{a, c} (N = integer)	Oversampling Rate (OSR) – (Recommended) ^{b, d}	Notes ^h
N7600B W-CDMA/ HSPA+	10 msec * N repetitions (Basic) Number of msec or Number of frames * N repetitions (Advanced)	8x or AUTO (Basic) AUTO (Advanced Single Carrier)	Avoid exporting the PRACH and CELL_FACH carriers. Avoid exporting Multicarrier waveforms. Instead, export the Advanced carriers individually and then import the single carriers using the N7625B, to create a Multicarrier waveform.
N7601B cdma2000/ 1xEV-DO	26.6666 msec * N repetitions (Basic C2K and 1xEV-DO)	25x or AUTO (Basic)	Advanced 1xEV-DO is not recommended (240 msec x N repetitions). Avoid using 26.6666 msec * 4 repetitions. Avoid exporting Multicarrier waveforms. Instead, export the Advanced carriers individually and then import the single carriers using the N7625B, to create a Multicarrier waveform.
N7602B GSM/EDGE/ Evo	60 msec * N repetitions (Basic and Advanced)	128x or AUTO (Basic) AUTO (Advanced Single Carrier)	Default or integer multiple of 13 frames (60 msec) is required to import basic carrier waveform file. Avoid exporting the Control channel carrier. Avoid exporting older default GSM/EDGE 4 frame waveforms (≤ v2.x). Avoid exporting Multicarrier waveforms. Instead, export the Advanced carriers individually and then import the single carriers using the N7625B, to create a Multicarrier waveform.
N7612B TD-SCDMA/ HSDPA	5 msec * N repetitions	24 is recommended (1.28 * 24 = 30.72)	Default or integer multiple of 5 ms is required to import basic carrier waveform file.
N7617B WLAN	10 msec * N repetitions	Set the Oversampling Ratio (located under Waveform Setup) to adjust the ARB Sample Clock value so it is close to an integer multiple of 30.72 Msps (LTE software's base sample rate). This improves waveform quality.	Waveform signal length needs to be integer multiple of 10 msec by adjusting parameters “Idle Interval” and “# of frames" when generating from N7617B. (RF burst + idle interval) x (# of frame) = waveform signal length. Note: “waveform signal length” needs to be integer multiple of 10 msec (in actual time length). “RF burst” length changes by various WLAN parameters including bandwidth. Waveform signal length (in “actual time length”) = (total sample points) / (ARB sample clock) Note: ARB sample clock is affected by bandwidth.
N7624B LTE/LTE-Advanced FDD	For N7624B waveforms: non-MSR (external) waveform files can be imported.	Set the Oversampling Ratio (located under Waveform Setup > Carrier n) to adjust the Waveform Sampling Ratio so it is an integer multiple of 30.72 Msps (LTE software's base sample rate). This is required for the waveform data to be imported into MSR and improves waveform quality. The Waveform Sampling Ratio updates after each waveform generation to show the actual value, so you can use that to fine tune.	To prevent recursive imports, no external MSR files of any type, can be imported.
N7625B LTE/LTE-Advanced TDD	For N7625B waveforms: non-MSR (external) waveform files can be imported.	Set the Oversampling Ratio (located under Waveform Setup > Carrier n) to adjust the Waveform Sampling Ratio so it is an integer multiple of 30.72 Msps (LTE software's base sample rate). This is required for the waveform data to be imported into MSR and improves waveform quality. The Waveform Sampling Ratio updates after each waveform generation to show the actual value, so you can use that to fine tune.	To prevent recursive imports, no external MSR files of any type, can be imported.

ARB Sample Clock ≥ 100 MHz can be used, but performance may be degraded. The ARB Sample Clock parameter is displayed under the Instrument node. It is automatically calculated by the software based on the signal generator's ARB Sample Clock settings. The ARB Sample Clock should be < 100 MHz. If a Frequency Offset is applied to a waveform, the settings should be compatible with the ARB Sample Clock settings on the signal generator.
Higher OSR values will degrade performance once the waveforms are imported into the N7625B's MSR waveform. For Advanced N7600B or N7601B carriers, OSR's = 1 are not recommended while Signal Studio is in Simulation Mode (e.g. use AUTO).
The waveform length is dependent on the resampling ratio:
- The source waveform clock > baseband sampling clock; source waveform will be decimated. This is typically not desirable, but will decrease waveform size.
- The source waveform clock < baseband sampling clock; source waveform will be oversampled. This is typically acceptable, but will increase waveform size.
- Waveform Quality will always degrade on resampling.
The MSR waveform requirements (source wavelength * baseband sampling clock) should be ≥ 1024 sample points and ≤ 1024e6 sample points.
For all of the component waveforms, set the Frequency Offset to 0. Frequency Offset can be set in the N7625B software, after importing all of the waveforms.
For the N7600B, N7601B, N7602B, N7612B, N7624B and N7625B software, to better understand the carrier power level calculations for an exported waveform, refer to Output Power Calculation (Downlink) and Output Power Calculation (Uplink).
Size of exported file must be ≤ 1024 Msa. If the waveforms exceed the maximum allowable, the System Message window is displayed.
There are three different descriptions for the various waveform setups:
- The recommended waveform settings yield the best overall performance with the MSR feature (i.e. faster waveform loading times, minimal intermodulation products, and minimal EVM).
- The waveform settings that are not recommended will work, but with reduced waveform performance (i.e. increased waveform loading times, increased intermodulation products, and degraded EVM).
- The waveform settings that are to be avoided may not work as desired or have some other unpredictable behavior.
The maximum number of component waveforms that can be imported into an MSR composite waveform are limited by the number of unique licenses required to generate the MSR waveform. For example:

3 Basic waveforms + 1 W-CDMA waveform = 4 waveform component licenses

Typically, up to approximately 11 waveforms can be used in a MSR waveform. If the number of waveforms exceeds the MSR feature's limits, an error message will be displayed.

Library Manager: After your waveforms have been exported to your waveforms folder using the settings in step 1 above, use the Library Manager to import and save your exported waveforms as Library Waveforms. Importing and saving your waveforms to the Waveform Library folder as Library Waveforms enables faster waveform generation. Waveforms that are imported into the Waveform Library Manager should meet the criteria in the table below.

For information on how to import a waveform and save it to the Library Folder as a Library Waveform, refer to the MSR - Using the Waveform Library Manager topic.

MSR Waveform Setting Levels	Baseband Sampling Rate ^{a, b}	Frequency Offset ^a	Power (Offset)	Notes
Recommended	AUTO, 61.44 MHz	as required	as required	Where the Frequency Offset = 0, a Baseband Sampling Rate of 30.72 MHz can be used to decrease waveform build time.
Allowable	184.32 MHz	as required	as required	Possible degradation in waveform generation time and in waveform performance quality.

After importing the waveforms into the MSR waveform, the default Baseband Sampling Rate is set to 61.44 MHz. This value is required for non-zero Frequency Offsets and optional for 0 Hz Frequency Offsets. If the Frequency Offset is set to 0 Hz in the N7625B, the Baseband Sampling Rate can be set to 30.72 MHz and the waveform build-time will be faster. The Baseband Sampling Rate of 184.32 MHz can be used, but the waveform's performance may be degraded. The Baseband Sampling Rate = (chip rate * oversampling ratio). For best results, the Baseband Sampling Rate should be < 100 MHz.
To avoid degradation of the signal, in the N7625B software, do not use the default oversampling rate of 1 with MSR waveforms. For best results, use AUTO for the OSR value.
The MSR waveform requirements (source wavelength * baseband sampling clock) should be ≥ 1024 sample points and ≤ 1024e6 sample points.

Library Waveforms: After your Library Waveform files have been imported to the Waveform Library Folder, click the Add to Signal Studio as a new carrier () button to select Library Waveform:

Steps a through d (below) only work if you have previously stored Library Waveforms to your Waveform Library folder. Refer to the MSR - Using the Waveform Library Manager topic.
1. Click Add Carrier to open a Library Waveform.
2. Click Waveform Setup > Carrier n > Source Waveform Name.
3. When the Selects Source Waveform window opens, open the Waveform Library folder where your waveforms are located and click on the desired Library waveform.
  
  For information on the Waveform Item Abstraction parameters, refer to the Library Manager Window topic.
4. Click OK to add the waveform to your Waveform Setup node.
5. To add additional Library Waveforms with different resample targets (sampling ratios) and Filter Ratios, repeat steps a through d.
6. Signal Studio: If necessary, in the Carrier n node, click to change the following:
7. Repeat step f for all of your Carriers. Otherwise, continue to next step.
8. Click Generate Waveform.
9. If you are satisfied with your Library Waveform's configuration and the resulting MSR waveform, proceed to step 4. Otherwise, continue to next step.
10. For best results, if you need to make changes to the Filter Ratio or the Resample Target for the Library values, use the Library Manager window and the Resample... () button.
  
  When you open a Library Waveform and click the Resample... () button to modify the Filter Ratio or Resample Target parameters, any previous resampling values that have been selected for the Library Waveform are grayed out or inactive. These previously selected resample values have already been resampled and are already saved to your Waveform Library folder or subfolders and do not need to be resampled. Here the Import Waveform window is shown, but the Resample Waveform window is very similar.
  
  Changing your waveform's Baseband Sampling Rate, Timing Offset, Power, Initial Phase, and Filter Ratio parameters outside of the Library Manager may potentially increase your waveform generation times.
  1. Optionally, in the Signal Studio's Carrier n node, click Baseband Sampling Rate, Frequency Offset, Power, Timing Offset, Initial Phase, or Filter Ratio to change these parameters.
  2. Click Generate Waveform to update your system to the new settings. Refer to step 4 for waveform output examples.
11. To make additional changes to your waveforms, repeat step j as necessary.
Signal Studio: After all of the component waveform files have been imported, generate and download the waveform by choosing the correct file path for the MSR waveform file. The new multicarrier waveform comprises all the license requirements for each of the component waveform types used. Here is an example of an MSR waveform with five component carriers.
In the MSR composite waveform, the waveforms that have narrower bands — like CW and EDGE waveforms — are displayed with higher power levels. This is because the waveforms' power is defined by its integrated power and not by its power spectral density (PSD).
To minimize spurious images, optimize the channel waveform filtering and frequency offsets for the imported component waveforms. Refer to MSR: Applying a Waveform Channel Filter.