Mobile WiMAX Downlink Transmitter Test

The WMAN_DL_802_16e_TX transmitter test bench provides a way for users to connect to an RF circuit device under test (RF DUT) and determine its performance by activating various test bench measurements. This test bench provides signal measurements for RF envelope, signal power (including CCDF), constellation, spectrum, and EVM.

The signal and most of the measurements are designed according to References [1] and [2].

The Mobile WiMAX downlink frame structure is illustrated in Mobile WiMAX DL frame structure.

Mobile WiMAX DL frame structure

The downlink subframe starts with one preamble which consists of an OFDM symbol. Then the PUSC zone where FCH, DL-MAP and UL-MAP are allocated. The FCH information will be sent on the first four adjacent subchannels with successive logical subchannel numbers in the PUSC zone. The DL-MAP message immediately follows FCH. The UL-MAP message is always allocated on the third and fourth OFDM symbols if ULMAP_Enable is set to YES.

If ZoneType is DL_PUSC, then a single PUSC zone is defined (a in Mobile WiMAX DL frame structure). If ZoneType is DL_FUSC or DL_OFUSC, then two zones are defined: one is the PUSC zone where FCH is allocated, the other is the FUSC or OFUSC zone for allocating data bursts (b in Mobile WiMAX DL frame structure). ZoneNumOfSym is defined as the number of OFDM symbols for the zone which is allocated data bursts. One downlink frame contains maximum 8 data bursts except FCH, DL-MAP and UL-MAP, and each burst contains only one MAC PDU. Among these bursts, only one burst is FEC-encoded which is randomized, CC coded and interleaved. Other bursts will be provided PN sequences as their coded source respectively.

For DL_PUSC, the total number of symbols in the downlink subframe is ( 1+ZoneNumOfSym ); For DL_FUSC or DL_OFUSC, the total number of symbols in the downlink subframe is ( 1+2+ULMAP_Enable�2+ZoneNumOfSym ), where 1 is for the preamble, the first 2 are for the FCH and DL-MAP, the second 2 are for the UL-MAP, ULMAP_Enable is 1 when set to YES and 0 when set to NO.

Test Bench Basics

Mobile WiMAX DL Transmitter Test Bench

The basics for using the test bench are:

• Replace the DUT (Amplifier2 is provided with this template) with an RF DUT that is suitable for this test bench.
• CE_TimeStep, SourcePower, and FMeasurement parameter default values are typically accepted; otherwise, set values based on your requirements.
• Activate/deactivate measurements based on your requirements.
• Run the simulation and view Data Display page(s) for your measurement(s).

Test Bench Details

The following sections provide details for setting up a test bench, setting measurement parameters for more control of the test bench, simulation measurement displays, and baseline performance.
Open and use the WMAN_DL_802_16e_TX_test template:

1. In an Analog/RF schematic window, choose Insert > Template .
2. In the Insert > Template dialog box, choose WMAN_DL_802_16e_TX_test , click OK ; click left to place the template in the schematic window.

Test bench setup is detailed here.

1. Replace the DUT (Amplifier2 is provided with this template) with an RF DUT that is suitable for this test bench.
   For information regarding using certain types of DUTs, refer to RF DUT Limitations.
2. Set the Required Parameters.

   Note Refer to WMAN_DL_802_16e_TX for a complete list of parameters for this test bench.

   Generally, default values can be accepted; otherwise, values can be changed by the user as needed.

   • Set CE_TimeStep.
     Cosimulation occurs between the test bench (using ADS Ptolemy Data Flow simulation technology) and the DUT (using Agilent Circuit Envelope simulation technology). Each technology requires its own simulation time step with time-step coordination occurring in the interface between the technologies.
     CE_TimeStep defines the Circuit Envelope simulation time step to be used with this DUT. The CE_TimeStep must be set to a value equal to or a submultiple of (less than) WTB_TimeStep; otherwise, simulation will stop and an error message will be displayed.
     Note that WTB_TimeStep is not user-settable. Its value is derived from other test bench parameter values. The value is displayed in the Data Display pages as TimeStep.
     WTB_TimeStep = 1/(RF_SamplingRate × Ratio)
     where
     The RF_SamplingRate (Fs) implemented in the design is decided by Bandwidth and related sampling factor () as follows,

     sampling factor n	bandwidth
     8/7	For channel bandwidths that are a multiple of 1.75 MHz
     28/25	else for channel bandwidths that are a multiple of 1.25 MHz, 1.5 MHz, 2 MHz or 2.75 MHz
     8/7	else for channel bandwidths not otherwise specified

     Bandwidth is the user-settable value (default 10 MHz)
     Ratio is the oversampling ratio related to OversamplingOption as Ratio = 2 ^{OversamplingOption} .

   • Set SourcePower, and FMeasurement.
     • SourcePower defines the power level for FSource. SourcePower is defined as the peak power during the non-idle time of the signal frame.
     • FMeasurement defines the RF frequency output from the DUT to be measured.
3. Activate/deactivate ( YES / NO ) test bench measurements (refer to WMAN_DL_802_16e_TX). At least one measurement must be enabled:
   • RF_EnvelopeMeasurement
   • Constellation
   • PowerMeasurement
   • SpectrumMeasurement
   • EVM_Measurement
4. More control of the test bench can be achieved by setting Basic Parameters , Signal Parameters , and parameters for each activated measurement. For details, refer to Setting Parameters.
5. The RF modulator of WMAN_DL_802_16e_TX (shown in the block diagram in Mobile WiMAX DL Transmitter Test Bench) uses SourcePower ( Required Parameters ), GainImbalance, PhaseImbalance( Signal Parameters ).
   The RF output resistance uses SourceR, SourceTemp, and EnableSourceNoise ( Basic Parameters ). The RF output signal source has a 50-ohm (default) output resistance defined by SourceR.
   RF output (and input to the RF DUT) is with the specified source resistance (SourceR) and with power (SourcePower) delivered into a matched load of resistance SourceR. The RF signal has additive Gaussian noise power set by resistor temperature (SourceTemp) (when EnableSourceNoise=YES).
   Note that the Meas point of the test bench provides a resistive load to the RF DUT set by the MeasR value (50-ohm default) ( Basic Parameters ).
   The Meas signal contains linear and nonlinear signal distortions and time delays associated with the RF DUT input to output characteristics.
   The DSP block of WMAN_DL_802_16e_TX (shown in the block diagram in Mobile WiMAX DL Transmitter Test Bench) uses other Signal Parameters .
6. More control of Circuit Envelope analysis can be achieved by setting Envelope controller parameters. These settings include Enable Fast Cosim, which may speed the RF DUT simulation more than 10×. Setting these simulation options is described in Setting Fast Cosimulation Parameters and Setting Circuit Envelope Analysis Parameters in the Wireless Test Bench Simulation documentation.
7. To run a simulation, choose Simulate > Simulate in the Schematic window.
   For details on Running a Simulation refer to the Wireless Test Bench Simulation documentation.
8. Simulation results will appear in a Data Display window for each measurement. Simulation Measurement Displays describes results for each measurement available for this test bench.

For details on Viewing Results refer to the Wireless Test Bench Simulation documentation.