TDSCDMA_DnLnk_RX_ACS

This section provides parameter information for Required Parameters, Basic Parameters, Signal Parameters, and measurement parameters.

Symbol

Description TD-SCDMA downlink RX ACS
Library WTB
Class TSDFTDSCDMA_DnLnk_RX_ACS
Derived From baseWTB_RX

Parameters
Name Description Default Sym Unit Type Range
RequiredParameters            
CE_TimeStep Circuit envelope simulation time step 1/1.28 MHz/8   sec real (0, ∞)
WTB_TimeStep Set CE_TimeStep < = 1/1.28e6/SamplesPerChip.        
FSource Source carrier frequency 1900 MHz   Hz real (0, ∞)
SourcePower Source power dbmtow(-91.0)   W real [0, ∞)
FMeasurement Measurement carrier frequency 1900 MHz   Hz real (0, ∞)
BasicParameters            
SourceR Source resistance 50 Ohm   Ohm real (0, ∞)
SourceTemp Source resistor temperature 16.85   Celsius real [-273.15, ∞)
MeasR Measurement resistance 50 Ohm   Ohm real [10, 1.0e6]
MirrorSourceSpectrum Mirror source spectrum about carrier? NO, YES NO     enum  
MirrorMeasSpectrum Mirror meas spectrum about carrier? NO, YES NO     enum  
TestBenchSeed Random number generator seed 1234567     int [0, ∞)
SignalParameters            
GainImbalance Gain imbalance, Q vs I 0.0   dB real (-∞, ∞)
PhaseImbalance Phase imbalance, Q vs I 0.0   deg real (-∞, ∞)
I_OriginOffset I origin offset (percent) 0.0     real (-∞, ∞)
Q_OriginOffset Q origin offset (percent) 0.0     real (-∞, ∞)
IQ_Rotation IQ rotation 0.0   deg real (-∞, ∞)
SamplesPerChip Samples per chip 8 S   int [2, 32]
ActiveTimeslot Active Timeslot: TS0, TS2, TS3, TS4, TS5, TS6 TS0     enum  
RRC_FilterLength RRC filter length (chips) 12     int [2, 128]
BasicMidambleID Basic midamble index 0     int [0, 127]
MidambleID Midamble index 1     int [1, K]
MaxMidambleShift Max midamble shift 16 K   int {2, 4,6,8,10,12,14,16}
MinSF Minimum spreading factor 16     int {1, 2,4,8,16}
SpreadCode1 Spread code index for first channel 1     int [0, 15]
SpreadCode2 Spread code index for second channel 2     int [0, 15]
AdjChSignalParameters            
AdjChFSourceOffset Adjacent channel carrier frequency offset 1.6 MHz   Hz real [0, ∞)
AdjChPower Adjacent channel power dbmtow(-54.0)   W real [0, ∞)
MeasurementParameters            
DisplayPages RX downlink ACS measurement display pages:        
StartBlock Start block 1     int [0, 1000]
StopBlock Stop block 50     int [1, 1000]
Pin Inputs
Pin Name Description Signal Type
2 Meas_In Test bench measurement RF input from RF circuit timed
Pin Outputs
Pin Name Description Signal Type
1 RF_Out Test bench RF output to RF circuit timed

Setting Parameters

More control of the test bench can be achieved by setting parameters on the Basic Parameters, Signal Parameters, Adjacent Channel Selectivity, and measurement categories.

Basic Parameters

  1. SourceR is the RF output source resistance.
  2. SourceTemp is the RF output source resistance temperature (oC) and sets noise density in the RF output signal to (k(SourceTemp+273.15)) Watts/Hz, where k is Boltzmann's constant.
  3. MeasR defines the load resistance for the RF DUT output Meas signal into the test bench. This resistance loads the RF DUT output; it is also the reference resistance for Meas signal power measurements.
  4. MirrorSourceSpectrum is used to invert the polarity of the Q envelope of the generated RF signal before it is sent to the RF DUT. Depending on the configuration and number of mixers in an RF transmitter, the signal at the input of the DUT may need to be mirrored. If such an RF signal is desired, set this parameter to YES.
  5. MirrorMeasSpectrum is used to invert the polarity of the Q envelope in the Meas_in RF signal input to the test bench (and output from the RF DUT). Depending on the configuration and number of mixers in the RF DUT, the signal at its output may be mirrored compared to the signal generated by the signal source (before any mirroring is done because of the MirrorSourceSpectrum setting). Proper demodulation and measurement of the RF DUT output signal requires that its RF envelope is not mirrored compared to the signal generated by the signal source (before any mirroring is done because of the MirrorSourceSpectrum setting). If the Meas_in RF signal is mirrored, set this parameter to YES. Proper setting of this parameter is required for measurements on the Meas_in signal in RX text benches and results in measurement on a signal with no spectrum mirroring.
  6. TestBenchSeed is an integer used to seed the random number generator used with the test bench. This value is used by all test bench random number generators, except those RF DUT components that use their own specific seed parameter. TestBenchSeed initializes the random number generation. The same seed value produces the same random results, thereby giving you predictable simulation results. To generate repeatable random output from simulation to simulation, use any positive seed value. If you want the output to be truly random, enter the seed value of 0.

Signal Parameters

  1. GainImbalance, PhaseImbalance, I_OriginOffset, Q_OriginOffset, and IQ_Rotation are used to add certain impairments to the ideal output RF signal. Impairments are added in the order described here.
    The unimpaired RF I and Q envelope voltages have gain and phase imbalance applied. The RF is given by:

    where A is a scaling factor that depends on the SourcePower and SourceR parameters specified by the user, V I ( t ) is the in-phase RF envelope, V Q ( t ) is the quadrature phase RF envelope, g is the gain imbalance

    and, φ (in degrees) is the phase imbalance.
    Next, the signal V RF ( t ) is rotated by IQ_Rotation degrees. The I_OriginOffset and Q_OriginOffset are then applied to the rotated signal. Note that the amounts specified are percentages with respect to the output rms voltage. The output rms voltage is given by sqrt(2 × SourceR × SourcePower).
  2. SamplesPerChip sets the number of samples in a chip.
    The default value is set to 8 to display settings according to the 3GPP NTDD. It can be set to a larger value for a simulation frequency bandwidth wider than 8 × 1.28 MHz. It can be set to a smaller value for faster simulation; however, this will result in lower signal fidelity. If SamplesPerChip = 8, the simulation RF bandwidth is larger than the signal bandwidth by a factor of 8 (e.g., simulation RF bandwidth = 8 × 1.28 MHz).
  3. ActiveTimeslot specifies which timeslot is active. The ACS measurement is based on this active timeslot.
  4. RRC_FilterLength shows root raised-cosine (RRC) filter length in chips.
    The default value is set to 12 to transmit TD-SCDMA downlink signals in time and frequency domains based on the 3GPP NTDD standard. It can be set to a smaller value for faster simulation; however, this will result in lower signal fidelity.
  5. BasicMidambleID sets the basic midamble code ID. The basic midamble code is used for training sequences for uplink and downlink channel estimation, power measurements and maintaining uplink synchronization. There are 128 different sequences; the BasicMidambleID range is 0 to 127. In Signal Studio, Basic Midamble ID code has the same meaning as this parameter.
  6. MidambleID is the midamble index which specifies which midamble is used in the physical channel.
  7. MaxMidambleShift is the maximum number of different midamble shifts in a cell that can be determined by maximum users in the cell for the current time slot.
  8. MinSF is the minimum spreading factor which can be used by the physical channel.
  9. SpreadCode1 and SpreadCode2 set spread code indices for the first and second DPCH, respectively. For this signal source, the spreading factor is 16.

Adjacent Channel Selectivity Parameters

  1. AdjChFSourceOffset is the adjacent channel carrier frequency offset.
  2. AdjChPower is the transmit power of the adjacent channel.

Measurement Parameters

This measurement requires setting the MirrorMeasSpectrum parameter such that there is an even number of spectrum mirrorings from the combined test bench source and RF DUT. For example, if MirrorSourceSpectrum = NO and the RF DUT causes its output RF signal to have spectrum mirroring relative to its input signal, then set MirrorMeasSpectrum = YES.

  1. DisplayPages provides Data Display page information for this test bench. It cannot be changed by the user.
  2. StartBlock sets the start block. The block is the unit set of TD-SCDMA subframes for processing channel coding. One block contains four subframes. A value of 0 is the first block.
  3. StopBlock sets the stop block. For example, StopBlock=50 results in a measurement of 51 blocks.

Simulation Measurement Displays

After running the simulation, results will be displayed in the Data Display page as shown in Simulation Results.

Note
Measurement results from a wireless test bench have associated names that can be used in Data Display Expressions. For more information, refer to Measurement Results for Expressions for TD-SCDMA Wireless Test Benches.

The BER must be less than 0.001 for a desired input level of -91 dBm with a -54 dBm adjacent interference as specified for a TD-SCDMA signal with a 12.2 k reference channel.

Simulation Results

Test Bench Variables for Data Displays

Reference variables used to set up this test bench are listed in Test Bench Parameters Exported to the Data Display.

Test Bench Parameters Exported to the Data Display
Data Display Parameter Equation with Test Bench Parameters
RF_FSource FSource
RF_SourcePower_dBm 10*log10(SourcePower)+30
RF_SourceTemp SourceTemp in degrees Celcius

Baseline Performance

Expected ADS Performance

Expected ADS performance is the combined performance of the baseline test bench and the RF DUT Circuit Envelope simulation with the same signal and number of time points. For example, if the RF DUT performance with Circuit Envelope simulation alone takes 2 hours and consumes 200 MB of memory (excluding the memory consumed by the core ADS product), then add these numbers to the Baseline Performance numbers to determine the expected ADS performance. This is valid only if the full memory consumed is from RAM. If RAM is less, larger simulation times may result due to increased disk access time for swap memory usage.

References

  1. 3GPP TS 25.221, "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical channels and mapping of transport channels onto physical channels (TDD) (Release 4)," version 4.5.0, June, 2002.
    http://www.3gpp.org/ftp/Specs/2002-06/Rel-4/25_series/25221-450.zip]
  2. 3GPP TS 25.223, "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Spreading and modulation (TDD) (Release 4)," version 4.4.0, March, 2002.
    http://www.3gpp.org/ftp/Specs/2002-06/Rel-4/25_series/25223-440.zip]
  3. 3GPP TS 25.102, "3rd Generation Partnership Project; Technical Specification Group Radio Access Networks; UE Radio Transmission and Reception (TDD) (Release 4)," version 4.5.0, June, 2002.
    http://www.3gpp.org/ftp/Specs/2002-06/Rel-4/25_series/25102-450.zip]
  4. 3GPP TS 34.122, "3rd Generation Partnership Project; Technical Specification Group Terminal; Terminal Conformance Specification; Radio Transmission and Reception (TDD) (Release 4)," version 4.4.0, June, 2002.
    http://www.3gpp.org/ftp/Specs/2002-06/Rel-4/34_series/34122-440.zip]
    Setting up a Wireless Test Bench Analysis in the Wireless Test Bench Simulation documentation explains how to use test bench windows and dialogs to perform analysis tasks.
    Setting Circuit Envelope Analysis Parameters in the Wireless Test Bench Simulation documentation explains how to set up circuit envelope analysis parameters such as convergence criteria, solver selection, and initial guess.
    Setting Automatic Verification Modeling Parameters in the Wireless Test Bench Simulation documentation explains how to improve simulation speed.
 

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