WCDMA, LTE, NR, and EV-DO modulation schemes allow you to define several carriers and combine them in arbitrary sets. This is achieved using Carrier Definitions and Carrier Sets.

Carrier Definition and Carrier Sets

A carrier definition is a set of parameters for the chosen modulation scheme. All these parameters are present in the Modulation tab. The modulation parameters of a carrier definition and the filter settings together completely specify the baseband signal expected from this carrier definition. The spectrum of such a baseband signal is a traditional single-carrier case. When RF-modulated, this baseband signal will be exactly centered around the carrier frequency.

In the multi-carrier case, there can be several sets of parameters that specify respective carrier definitions.

Note All carrier definitions share the filter settings, i.e. every carrier definition uses the same filter settings shown in the Filter tab.

To configure the modulation parameters for a carrier definition, perform the following steps:

  1. From the Modulation tab, select a scheme. The New Settings File tab is prompted.
  2. In the New Settings File tab, click OK. The selected modulation scheme window is prompted.
  3. Under the Modulation tab, in the Carrier Definitions panel set the Maximum Number of Carrier Definitions for a link and to copy parameter values from one carrier definition to another.
    Note The copy from Carrier Definition tab is enabled only when value of the Maximum Number of Carrier Definitions is more than 1.

The parameters to configure carrier definitions are as follows.

Maximum Number of Carrier Definitions: The maximum number of carrier definitions that can be defined.

Carrier Definition Number: Sets the current carrier definition number of the definition that you want to configure.

Carrier Definition Name: Enables you to provide a name to the carrier definition. It will reflect in the choice of carrier definition to copy from.

Copy from Carrier Definition: Allows you to select the carrier definition number that you want to copy to the current one.

Note To copy a carrier definition in NR, select the carrier definition to be copied and click Copy to New.

Generating a Multi-Carrier Signal

To generate a multi-carrier signal, you must also configure how the baseband signals of various carrier definitions must be combined.

A carrier set is set of carrier definitions whose signals are to be combined into one baseband signal that can be played from a single instrument. Thus, CFR, IQ impairments and the Graphical display of the output apply to each carrier set.

LTE and NR multi-carrier configuration is slightly different from EV-DO and WCDMA. For more information on LTE Multi-Carrier configuration, refer to the LTE Multi-Carrier and NR Multi-Carrier sections of RFmx Waveform Creator Modulation Schemes. Details for Multi-Carrier configuration of EV-DO and WCDMA can be found in this topic.

Every modulation scheme that integrates multicarrier operation will show a Multi-Carrier tab. By default, this tab will have carrier set 0 with carrier definition 0 mapped to it. All other parameters (frequency offset, gain, phase, and delay) default to 0 as shown in the following image.

The parameters to configure each carrier set, shown in the lower section of the preceding figure are given below.

Randomize Delay Button: Randomizes the time delay of all carriers currently in random delay mode.

Reset Delay Button: Resets the random number generators used to randomize the time delay of each carrier in random mode. After clicking this button, the time delay of these files will return to the first random delay value generated.

Reset Delay Button: Resets the random number generators used to randomize the time delay of each carrier in random mode. After clicking this button, the time delay of these files will return to the first random delay value generated.

Randomize Phase Button: Randomizes the phase of all carriers currently in random phase mode.

Reset Phase Button: Resets the random number generators used to randomize the phases of each carrier currently in random mode. After clicking this button, the phase of these carriers returns to the first random phase value generated.

Oversampling Factor: Sets the oversampling factor. This allows you to increase the default sample rate, which is calculated internally. The default is 1. To manually change the oversampling factor, uncheck the Auto checkbox.

Carrier Set Name: You can use this field to provide a name to the carrier set.

Carrier Set Number: Implies the carrier set index to which the sampling rate and oversampling factor is applied.

Note Different carrier sets may have different sampling rates and oversampling factors depending on the carrier definitions, and their frequency offsets, that are mapped to them.

By clicking Add in this tab, the dialog box as shown in the following image appears.

The parameters in the Add Carrier dialog box are described in the following sections.

Carrier Definition: Implies the definition index. Carrier definition goes from 0 to N-1 where, N is the maximum number of carrier definitions chosen by you in the Modulation tab.

Carrier Set: Depicts which set the carrier number belongs to. For M > 0, you are not allowed to choose carrier set M without also choosing at least one carrier in carrier set (M-1).

Frequency Offset: Represents the frequency offset from carrier by which the signal shifts when mixed. The value can be from -100 MHz to +100 MHz, including 0 Hz.

Phase Continuous: Instructs to calculate the closest cyclic frequency offset to the value in the Frequency Offset control and update the control with the new value. This value will be recalculated each time any carrier is added, modified or removed.

Gain: This is the power level of the current carrier relative to the other carriers you have added or will add later. The value can be from -60 dB to 0 dB.

Delay: Allows you to start the mixing at any point in the carrier and means you can emulate similar signals with different time references.

Random (checkbox next to Delay): In this field, mode automatically generates a time delay. Selecting this checkbox for each carrier in the table will result in a waveform with a lower crest factor.

Carrier Phase: Allows you to adjust the starting phase of the frequency mixer.

Random (checkbox next to Carrier Phase): Selecting this checkbox puts the file into random phase mode. In this mode, will automatically generate a random phase between -180 and +180 degrees. Selecting this checkbox for each carrier in the table will result in a waveform with a lower crest factor.

Example

You can specify five different configurations in five carrier definitions for each of the carriers in the general case, but this can be repetitive because more than one carrier can have the same configuration. In such cases, it is sufficient to specify only the required number of unique carrier definitions and map them to carriers in the respective carrier sets. For example, carrier definition 0 is used twice in the first band and carrier definition 1 is used in both bands. Illustration of carrier definitions and their mapping to carriers in carrier sets is shown in the following figure.

Configuration used in the Multi-Carrier tab are as shown in the following image.

To save the outputs of all carrier definitions when there are more than one defined, you must configure as many carrier sets and have a one-to-one mapping between them and set all other multi-carrier parameters as zero. The center frequency of a carrier set need not correspond to that of any carrier within it. For example, carrier 0 at 1900 MHz and carrier 1 at 1902.5 MHz can be combined in one carrier set at center frequency 1901.25 MHz with carrier 0 and carrier 1 having frequency offsets -1.25 MHz and +1.25 MHz respectively.

Note
  • IQ Impairments, CFR and Graphics tabs are applicable per carrier set. For more information, refer to the IQ Impairments, Crest Factor Reduction, and Plotting Graphs sections respectively.
  • When you have entered a frequency offset which is not cyclic, a warning symbol will appear next to the frequency in the table to notify you of this.
  • All carrier definitions must have the same duration in number of frames.