WMAN_UL_802_16e_TX

This section provides parameter information for Required Parameters, Basic Parameters, Signal Parameters, and parameters for the various measurements.

Setting Parameters

More control of the test bench can be achieved by setting parameters in the Basic Parameters , Signal Parameters , and measurement categories for the activated measurements.

Note
For required parameter information, see Set the Required Parameters.

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. EnableSourceNoise, when set to NO disables the SourceTemp and effectively sets it to -273.15oC (0 Kelvin). When set to YES, the noise density due to SourceTemp is enabled.
  4. 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.
  5. 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 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.
  2. Bandwidth determines the nominal channel bandwidth.
  3. OversamplingOption indicates the oversampling ratio of transmission signal. There are six oversampling ratios (1, 2, 4, 8, 16, 32) to support in this source.
  4. FFTSize specifies the size of FFT. Sizes 2048, 1024 and 512 are supported.
  5. CyclicPrefix specifies the ratio of cyclic prefix time to "useful" time, whose range is from 0 to 1.
  6. FrameMode determines what will actually be included in the generated waveform. FDD Mode means the entire frame is used for the uplink and the uplink starts at the beginning of the frame. TDD Mode means only the uplink is included in the generated waveform and it starts at some delay from the frame start time based on the Downlink Ratio setting.
  7. DL_Ratio set the percentage (1 to 99) of the frame time to be used for the downlink and also set the start time for the uplink. The parameter is only active when the FrameMode is TDD.
  8. FrameDuration determines the frame durations (ms) of the generated waveform.There are eight frame durations (2ms, 2.5ms, 4ms, 5ms, 8ms, 10ms, 12.5ms, 20ms) to be selected as allowed by the specification.
  9. PreambleIndex specifies the preamble index number (0 to 113). The preamble index value determines the ID Cell values (0 to 31) and segment index (0 to 2) according to Table 309 in the specification.
  10. FrameNumber specifies the starting frame number in the uplink subframe.
  11. FrameIncreased specifies whether the frame number for the uplink subframe is increased. When FrameIncreased is set to YES, then the frame numbers in Frame#0, Frame#1, Frame#2, Frame#3 will be FrameNumber , FrameNumber+1 , FrameNumber+2 , FrameNumber+3 . When FrameIncreased is set to NO, then the frame numbers in Frame#0, Frame#1, Frame#2, Frame#3 will be FrameNumber , FrameNumber , FrameNumber , FrameNumber .
  12. UL_PermBase specifies the permutation base that will be used in this uplink zone. Accepted values are 0 to 69.
  13. For DataPattern:
    • if PN9 is selected, a 511-bit pseudo-random test pattern is generated according to CCITT Recommendation O.153.
    • if PN15 is selected, a 32767-bit pseudo-random test pattern is generated according to CCITT Recommendation O.151.
    • if FIX4 is selected, a zero-stream is generated.
    • if x_1_x_0 is selected (where x equals 4, 8, 16, 32, or 64) a periodic bit stream is generated, with the period being 2 x. In one period, the first x bits are 1s and the second x bits are 0s.
    • if S_QPSK, S_16-QAM or S_64-QAM is selected, sequences below are generated. These are test messages for receiver sensitivity measurement.
      S_QPSK = [0xE4, 0xB1, 0xE1, 0xB4]
      S_16-QAM = [0xA8, 0x20, 0xB9, 0x31, 0xEC, 0x64, 0xFD, 0x75]
      S_64-QAM = [0xB6, 0x93, 0x49, 0xB2, 0x83, 0x08, 0x96, 0x11, 0x41, 0x92, 0x01, 0x00, 0xBA, 0xA3, 0x8A, 0x9A, 0x21, 0x82, 0xD7, 0x15, 0x51, 0xD3, 0x05, 0x10, 0xDB, 0x25, 0x92, 0xF7, 0x97, 0x59, 0xF3, 0x87, 0x18, 0xBE, 0xB3, 0xCB, 0x9E, 0x31, 0xC3, 0xDF, 0x35, 0xD3, 0xFB, 0xA7, 0x9A, 0xFF, 0xB7, 0xDB]
  14. AutoMACHeaderSetting indicates whether the MAC Header is calculated automatically. If it is set to NO, data sequences in parameter MAC_Header will be used before data content, otherwise MAC_Header content will be calculated with parameter DataLength and CID and be used before data content.
  15. MAC_Header specifies 6 bytes of MAC header before the data contents. The cell is only active when the AutoMACHeaderSetting is set to NO.
  16. CRC32_Mode specifies the method for CRC32 calculation appended to MAC PDU.
  17. ZoneType specifies the zone type which can be set to PUSC or OPUSC.
  18. ZoneNumOfSym specifies the number of symbols in the zone. The value must be a multiple of three because the uplink zone is divided into slots of 3 symbols x 1 subchannel (section 8.4.3.1 in 802.16e-2005). The maximum number of symbols available depends on the Bandwidth , FrameDuration , DL_Ratio , FFTSize , and CyclicPrefix .
  19. NumberOfBurst specifies the number of active uplink bursts.
  20. BurstWithFEC specifies the uplink burst FEC.
  21. BurstSymOffset positions each burst on the horizontal axis (x), if necessary, to avoid any burst overlap. The parameter is an array element.
  22. BurstSubchOffset positions each burst on the vertical axis (y), if necessary, to avoid any burst overlap. The parameter is an array element.
  23. BurstAssignedSlot specifies the total available slots in each burst. The parameter is an array element.
  24. DataLength specifies MAC PDU payload byte length for each burst.
  25. CodingType specifies the coding type for each burst. Each coding type can be selected from 0 to 1, whose meaning is shown in The meaning of coding type.
    Coding type meaning
    0 Convolutional coding (CC)
    1 Convolutional turbo coding (CTC)
  26. Rate_ID specifies the rate ID for each burst. Rate_ID, along with CodingType, determines the modulation and coding rate, shown in The relation of Coding type and Rate ID.
    Coding type Rate ID <th
    0 (CC) 0 QPSK CC1/2
    0 (CC) 1 QPSK CC3/4
    0 (CC) 2 16-QAM CC1/2
    0 (CC) 3 16-QAM CC3/4
    0 (CC) 4 64-QAM CC1/2
    0 (CC) 5 64-QAM CC2/3
    0 (CC) 6 64-QAM CC3/4
    1 (CTC) 0 QPSK CTC1/2
    1 (CTC) 1 QPSK CTC3/4
    1 (CTC) 2 16-QAM CTC1/2
    1 (CTC) 3 16-QAM CTC3/4
    1 (CTC) 4 64-QAM CTC1/2
    1 (CTC) 5 64-QAM CTC2/3
    1 (CTC) 6 64-QAM CTC3/4
    1 (CTC) 7 64-QAM CTC5/6
  27. RepetitionCoding specifies the repetition coding for each burst. Each repetition coding can be selected from 0 to 3, whose meaning is shown in The meaning of repetition coding.
    Repetition coding meaning
    0 No repetition coding on the burst
    1 Repetition coding of 2 used on the burst
    2 Repetition coding of 4 used on the burst
    3 Repetition coding of 6 used on the burst
  28. BurstPowerOffset determines the power offset of each burst in dB. The parameter is an array element.

RF Envelope Measurement Parameters

Depending on the values of RF_EnvelopeStart, RF_EnvelopeStop.

  1. RF_EnvelopeDisplayPages provides Data Display page information for this measurement. It cannot be changed by the user.
  2. RF_EnvelopeStart sets the start time for collecting input data.
  3. RF_EnvelopeStop sets the stop time for collecting input data.

For information about TimeStep, see Test Bench Variables for Data Displays".

Constellation Parameters

ConstellationDisplayPages provides Data Display page information for this measurement. It cannot be changed by the user.

Power Measurement Parameters

  1. PowerDisplayPages provides Data Display page information for this measurement. It cannot be changed by the user.
  2. PowerBursts sets the number of bursts over which data will be collected.

Spectrum Measurement Parameters

The Spectrum measurement calculates the spectrum of the input signal.
In the following, TimeStep denotes the simulation time step, and FMeasurement denotes the measured RF signal characterization frequency.

  1. The measurement outputs the complex amplitude voltage values at the frequencies of the spectral tones. It does not output the power at the frequencies of the spectral tones. However, one can calculate and display the power spectrum as well as the magnitude and phase spectrum by using the dBm, mag, and phase functions of the data display window.
    Note that the dBm function assumes a 50-ohm reference resistance; if a different measurement was used in the test bench, its value can be specified as a second argument to the dBm function, for example, dBm(SpecMeas, Meas_RefR) where SpecMeas is the instance name of the spectrum measurement and Meas_RefR is the resistive load.
    The basis of the algorithm used by the spectrum measurement is the chirp-Z transform. The algorithm can use multiple bursts and average the results to achieve video averaging.
  2. SpecMeasDisplayPages is not user editable. It provides information on the name of the Data Display pages in which this measurement is contained.
  3. SpecMeasStart sets the start time for collecting input data.
  4. SpecMeasStop sets the stop time for collecting input data.
  5. SpecMeasResBW sets the resolution bandwidth of the spectrum measurement when SpecMeasResBW>0.
    NENBW = normalized equivalent noise bandwidth of the window
    Equivalent noise bandwidth (ENBW) compares the window to an ideal, rectangular filter. It is the equivalent width of a rectangular filter that passes the same amount of white noise as the window. The normalized ENBW (NENBW) is ENBW multiplied by the duration of the signal being windowed. Window Options and Normalized Equivalent Noise Bandwidth lists the NENBW for the various window options.
    The Start and Stop times are used for both the RF and Meas signal spectrum analyses. The Meas signal is delayed in time from the RF signal by the value of the RF DUT time delay. Therefore, for RF DUT time delay greater than zero, the RF and Meas signal are inherently different and some spectrum display difference in the two is expected.
    TimeStep is defined in the Test Bench Variables for Data Displays section.
  6. SpecMeasWindow specifies the window that will be applied to each burst before its spectrum is calculated. Different windows have different properties, affect the resolution bandwidth achieved, and affect the spectral shape. Windowing is often necessary in transform-based (chirp-Z, FFT) spectrum estimation in order to reduce spectral distortion due to discontinuous or non-harmonic signal over the measurement time interval. Without windowing, the estimated spectrum may suffer from spectral leakage that can cause misleading measurements or masking of weak signal spectral detail by spurious artifacts.
    The windowing of a signal in time has the effect of changing its power. The spectrum measurement compensates for this and the spectrum is normalized so that the power contained in it is the same as the power of the input signal.
    Window Type Definitions:
    • none:

      where N is the window size
    • Hamming 0.54:

      where N is the window size
    • Hanning 0.5:

      where N is the window size
    • Gaussian 0.75:

      where N is the window size
    • Kaiser 7.865:

      where N is the window size,  α = N / 2, and I 0 (.) is the 0th order modified Bessel function of the first kind
    • 8510 6.0 (Kaiser 6.0):

      where N is the window size,  α = N / 2, and I 0 (.) is the 0th order modified Bessel function of the first kind
    • Blackman:

      where N is the window size
    • Blackman-Harris:

      where N is the window size.
      Window and Default Constant NENBW
      none 1
      Hamming 0.54 1.363
      Hanning 0.50 1.5
      Gaussian 0.75 1.883
      Kaiser 7.865 1.653
      8510 6.0 1.467
      Blackman 1.727
      Blackman-Harris 2.021

EVM Measurement Parameters

The EVM measurement is used to measure the EVM of Mobile WiMAX RF signal source with frequency hopping used, and needs no reference signal provided by the source.

  1. EVM_DisplayPages provides Data Display page information for this measurement. It cannot be changed by the user.
  2. EVM_Start sets the start time for collecting input data.
  3. If EVM_AverageType is set to OFF , only one frame is analyzed. If EVM_AverageType is set to RMS ( Video ), after the first frame is analyzed the signal segment corresponding to it is discarded and new signal samples are collected from the input to fill in the signal buffer of length 2 x FrameDuration. A second frame is analyzed and the process repeats until EVM_FramesToAverage frames are processed.
  4. EVM_FramesToAverage sets the frame number used for averaging.
  5. Starting at the time instant specified by the EVM_Start parameter, the component captures a signal segment of length 2 x FrameDuration. If EVM_PulseSearch is set to YES, this signal segment is searched in order for an RF burst to be detected. If the signal has multiple RF bursts in a FrameDuration then the first one detected is the one that will be analyzed. Some 802.16e OFDMA signals do not have RF burst characteristics, rather they look like a series of bursts with no "off" time between them. These signals resemble a "continually on" signal with embedded preambles. To demodulate signals that do not appear to be made up of RF bursts, EVM_PulseSearch should be set to OFF and EVM_Start should be set to the beginning of the uplink subframe you want to analyze. Otherwise, no pulse will be detected and no measurement will be performed.
    After an RF burst is detected, the I and Q envelopes of the input signal are extracted. The I and Q envelopes are passed to a complex algorithm that performs synchronization, demodulation, and EVM analysis. The algorithm that performs the synchronization, demodulation, and EVM analysis is the same as the one used in the Agilent 89600 VSA.
  6. The EVM_SymbolTimingAdjust parameter sets the percentage of symbol time by which we back away from the symbol end before we perform the FFT. Normally, when demodulating an OFDMA symbol, the cyclic prefix time (guard interval) is skipped and an FFT is performed on the last portion of the symbol time. However, this means that the FFT will include the transition region between this symbol and the following symbol. To avoid this, it is generally beneficial to back away from the end of the symbol time and use part of the guard interval. The EVM_SymbolTimingAdjust parameter controls how far the FFT part of the symbol is adjusted away from the end of the symbol time. The value is in terms of percent of the used (FFT) part of the symbol time. Note that this parameter value is negative, because the FFT start time is moved back by this parameter. EVM_SymbolTimingAdjust Definition. explains this concept. When setting this parameter, be careful to not back away from the end of the symbol time too much because this may make the FFT include corrupt data from the transition region at the beginning of the symbol time.

    EVM_SymbolTimingAdjust Definition.
  7. The EVM_TrackAmplitude, EVM_TrackPhase, and EVM_TrackTiming parameters specify whether the analysis will track amplitude, phase, and timing changes in the pilot subcarriers. 802.16e performs demodulation relative to the data in pilot carriers embedded in the signal. These pilot carriers replace data-carrying elements of the signal and allow some kinds of impairments to be removed or "tracked out." Many impairments will be common to all pilot carriers and can be measured as the "common pilot error." When these parameters are set to YES the analysis will track amplitude, phase, and timing changes in the pilot subcarriers and apply corrections to the pilot and data subcarriers.
    The flexibility to allow users to individually enable or disable tracking functions, provides useful troubleshooting capability, since modulation errors can be examined with and without the benefit of particular types of pilot tracking.
  8. The EVM_ExtendFrequencyLockRange parameter allows the user to increase the frequency lock range of the analysis. When set to YES it enables a frequency offset estimation algorithm prior to OFDMA demodulation to increase the frequency lock range of the analysis. This is especially useful when the center frequency drifts more than +/-1 kHz while making multiple measurements or the measurement setup uses multiple DUTs that have a frequency reference variance of greater than +/-1 kHz. The accuracy of the initial frequency offset estimate is dependent on the statistics of the analyzed waveform and may occasionally produce a frequency estimation error beyond the subsequent OFDMA analysis algorithms' capabilities. This will result in a frequency error of multiple kHz and the measurement will be unsynchronized.
  9. The EVM_EqualizerTraining parameter sets the type of training used for the equalizer. When demodulating an 802.16e signal, an equalizer is used to correct for linear impairments in the signal path, such as multi-path.
    When "Chan Estimation Seq Only" is selected the equalizer is trained using the Channel Estimation Sequence in the preamble of the OFDMA burst. After this initialization, the equalizer coefficients are held constant while demodulating the rest of the burst. This equalizer training method complies with the description in the "Transmit constellation error and test method" section (8.4.12.3) of the 802.16-2004 standard. However, for signals whose impairments change during the burst it might result in measured RCE (EVM) values that are higher compared to if the equalizer were trained over the entire burst.
    When "Chan Estimation Seq & Data" is selected the equalizer is trained by analyzing the entire OFDMA burst and using the Channel Estimation Sequence (contained in the preamble) and the all the subcarriers in the Data symbols. This type of equalizer training generally gives a more accurate estimate of the true response of the transmission channel and so results in lower RCE (EVM) measured values. However, it is more complicated and more computationally expensive to implement and therefore less likely to be used in practical receivers.
    When "Chan Estimation Seq & Pilots" is selected the equalizer is trained by analyzing the entire OFDMA burst and using the Channel Estimation Sequence (contained in the preamble) and the pilot subcarriers in the Data symbols. This gives results very similar to the "Chan Estimation Seq & Data" option without the excessive computational complexity.

Simulation Measurement Displays

After running the simulation, results are displayed in Data Display pages for each measurement activated.

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.

Envelope Measurement

The Envelope measurement shows the envelope of the Mobile WiMAX frame. Two signals are tested, the RF source signal at the RF DUT input and the Meas signal at the RF DUT output.
For envelope measurement, the default parameter setting is given in Default Parameter Setting for Measurement.

Parameter Default Setting
RF_FSource 2305.0 MHz
RF_R 50.0 Ohm
RF_Power 10.0 dBm
Bandwidth 10.0 MHz
RateID 5
CyclicPrefix 0.125
Frame_Duration 5.0 msec
TimeStep 44.643 nsec
SamplingFrequency 11.2 MHz
Frame_Mode TDD
DL_Ratio 0.618
Data_Length 710
Meas_FMeasurement 2305.0 MHz
Meas_R 50.0 Ohm

For the RF signal, the time domain envelope of one complete Mobile WiMAX frame is shown in Time Envelope of Mobile WiMAX UL RF Signal for Default Settings (one frame).

Time Envelope of Mobile WiMAX UL RF Signal for Default Settings (one frame)

For the Meas signal test, all measurements are the same as RF signal measurements, except the Meas signal will contain any linear and nonlinear distortions. Envelope measurements for Meas signal are shown in Time Envelope of Mobile WiMAX UL Meas Signal for Default Settings (one frame).

Time Envelope of Mobile WiMAX UL Meas Signal for Default Settings (one frame)

Constellation Measurement

The constellation measurement shows the RF and Meas signal constellations.

RF Signal Constellation


Meas Signal Constellation

Power Measurement

The power measurement shows the CCDF curves of the transmitter and peak-to-average ratios for the RF and Meas signals.
CCDF measurement results for RF and Meas signals are shown in RF Power CCDF and Meas Power CCDF.

Reference CCDF measurements for Gaussian noise can be calculated by calling the function power_ccdf_ref () in the. dds files directly.
Functions for calculating peak-to-average-ratios and results are shown in RF Signal Peak-to-Average-Ratio and Results and Meas Signal Peak-to-Average-Ratio Results.


RF Power CCDF


Meas Power CCDF


RF Signal Peak-to-Average-Ratio and Results


Meas Signal Peak-to-Average-Ratio Results

Spectrum Measurement

The Spectrum measurement is used to verify that the transmitted spectrum meets the spectrum mask according to Reference [3], section 5.3.3. The RF and Meas spectral density must fall within the spectral mask, as shown in RF Spectrum Mask and Meas Spectrum Mask.

RF Spectrum Mask


Meas Spectrum Mask

EVM Measurement

The EVM measurement is a modulation accuracy measurement. EVM measurement results shown in RF Signal EVM and Meas Signal EVM for 64-QAM-2/3 modulation do not exceed -28 dB; therefore the measurements meet the specification requirements.

RF Signal EVM


Meas Signal EVM

Test Bench Variables for Data Displays

Variables listed in Test Bench Variables for Data Displays are used to set up this test bench and data displays.

Data Display Parameter Equation with Test Bench Parameters
RF_FSource FSource
RF_Power_dBm 10*log10(SourcePower)+30
RF_R SourceR
TimeStep 1/SamplingFrequency/(2^OversamplintOption)
SamplingFrequency Bandwidth*n (n is sampling factor)
Bandwidth Bandwidth
RateID Rate_ID
CyclicPrefix CyclicPrefix
Data_Length DataLength
Frame_Duration FrameDuration
Frame_Mode FrameMode
DL_Ratio DL_Ratio
Meas_FMeasurement FMeasurement
Meas_R MeasR

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 for Mobile WiMAX Uplink Transmitter Test

  1. IEEE Std 802.16-2004, Part 16: Air Interface for Fixed Broadband Wireless Access Systems, Section 8.4 WirelessMAN-OFDMA PHY, October 1, 2004.
  2. IEEE Std 802.16e-2005, Amendment 2: for Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands and Corrigendum 1, - Part 16: Air Interface for Fixed Broadband Wireless Access Systems, Section 8.4 WirelessMAN -OFDMA PHY, February 2006.
  3. ETSI EN 301 021 V1.6.1 (2003-07): Fixed Radio Systems; Point-to-multipoint equipment; Time Division Multiple Access (TDMA); Point-to-multipoint digital radio systems in frequency bands in the range 3 GHz to 11 GHz

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 Behavioral Modeling Parameters in the Wireless Test Bench Simulation documentation explains how to improve simulation speed.

 

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