Components and Systems for Communications Research Group

Access and Scoring details

Access details

The remoteUPCLab is a remote PA measurement system that everyone is welcome to use! No registration is required. We just ask you not to overload the system. Our ambition is to have the remoteUPCLab permanently available. However, please respect that we may need to shut it down temporarily for maintenance.

In order to generate the test signal, upload/download the waveforms data files, and provide a score for each experiment, the following scripts and detailed instructions are provided to the user:               

TIME Remote User.zip                                                                                                            (MATLAB scripts)

NOTE: A Matlab version  R2021b or higher, with SFTP connectivity functions, is required.

The previous compressed file contains a simple example on how to call the basic functions of the remoteUPCLab. The user has only to execute the "Main_DPD_TIME_remote_user.m" script to check that the MATLAB functions are running OK (control messages are displayed during the waveform Tx/Rx process) and obtain an initial negative score before applying predistortion.

I. INTRODUCTION

The objective of the T.I.M.E. WEB-LAB 4 ALL project is to develop an effective Digital Predistortion (DPD) algorithm for linearizing a Load Modulated Balanced Amplifier (LMBA). The current LMBA configuration requires one RF input signal.

Users will be granted web-based access to the remoteUPCLab, a remote laboratory environment that enables them to:

  • Upload their predistorted baseband I/Q signal to the ADI board.

  • Retrieve the amplifier’s output and corresponding I/Q signal response, captured via the same ADI board.

Comprehensive information about the measurement setup can be found in the Measurement Setup section.

II. SIGNALS

The test signal consists of up to five 20 MHz or 40 MHz bandwidth, 16-QAM , 64-QAM  or 256-QAM modulated, 5G-like waveforms. The DPD algorithm must be robust enough to handle various configurations of this multi-channel signal, ranging from a single active channel to a composite 100 MHz or 200 MHz waveform with all five channels active simultaneously.

III. SCORING

At each iteration, the DPD linearizer performance will be scored taking into account five different quality metrics:

  • The average output power (dBm)
  • The PA power efficiency (%)
  • The worst channel ACPR value (dB)
  • The worst channel EVM value (%)
  • The number of coefficients of the DPD function

The out-of-band linearity is measured in terms of the adjacent channel power ratio (ACPR), computed for each band as the difference (in dB) between the integrated in-band power and the highest between the right and left, adjacent, integrated out-of-band powers (within the same bandwidth). The time-domain error is measured as error vector magnitude (EVM) computed as the root mean squared (RMS) value of the error in percentage (%) between the ideal constellation of symbols (being originally generated) and the measured output signals at each band. The number of coefficients of the DPD is represented in real-valued or complex-valued coefficients, accordingly to the DPD function employed by the user.

 Scoring trends:

  • ACPR Contribution (Weight: 10): ACPR values below the minimum threshold improve the score, while values above it reduce the score. The minimum ACPR depends on the signal configuration:
      • For 1 or 2 active channels, or the specific case of [0,1,1,1,0]: –45 dB
      • For any configuration with 3 or more active channels: –40 dB
  • EVM Contribution (Weight: 5): EVM values below the minimum threshold improve the score; values above the minimum threshold decrease it.
    • Only considered if the minimum ACPR threshold (–45 dB or –40 dB) is met.
  • Average Output Power (Weight: 10): Output powers above 30 dBm increase the score, while powers below 30 dBm reduce it.
        • Only considered if the minimum ACPR threshold is met.
      • Power Efficiency (Weight: 3):
        • Contributes positively only when the minimum ACPR requirement is satisfied.
      • DPD Model Complexity (Weight: 0.1):
        • Using fewer coefficients than the threshold improves the score; more coefficients reduce it.
        • Complexity thresholds depend on the number of active channels and coefficient type (real or complex):
          • For 1 or 2 channels:
            • Max 50 complex-valued or 200 real-valued coefficients
          • For 3 or more channels:
            • Max 100 complex-valued or 400 real-valued coefficients
        • 1 complex coefficient = 4 real coefficients
        • This contribution is only considered if the minimum ACPR is met.

      where ACPRmin is -45 dB if the signal consists of 2 channels, 1 channel or the [0,1,1,1,0] configuration, otherwise -40 dB. Additionally, ncoeffs,max is 50 if the DPD function operates with complex-valued coefficients, 200 if these coefficients are real and the signal consists of 2 channels or less. Otherwise, for more than 3 channels, ncoeffs,max is 100 if the DPD coefficients are complex-valued or 400 if these are real-valued. Finally, EVMmin =1.5% and Pmin=30 dBm.

      IV. MATLAB FUNCTIONS DESCRIPTION

      The overall procedure can be summarized following these steps:    

      1-Signal generation

      Note: The new signal generation function returns a signal TX.uBB with a scaling factor of 1.32 relative to the legacy version 

      [TX,PARAM] =TIME_generate_signal(Modulation, ChannelBW, config_chan)

      This function provides i) a multi-channel signal composed of 20 MHz or 40 MHz bandwidth, 16-QAM , 64-QAM  or 256-QAM modulated, 5G-like waveforms; and ii) A struct array containing the signal generation and acquisition settings (PARAM). The generated signal always has the same mean power but different PAPR.

       

      Inputs:

      - Modulation - Either 16, 64 or 256 for 16-QAM , 64-QAM  or 256-QAM modulations, respectively. Any other value will default to a 16-QAM.

      - ChannelBW - Either 20 or 40 for 20 MHz or 40 MHz channels, respectively. Any other vallue will default to 40 MHz channels.

      - config_chan - A 5-element binary array indicating the status of each channel (1 for active and 0 for inactive) (e.g., the figure above corresponds to [1,1,1,1,1]). If this input is left blank, i.e., [TX,PARAM] = TIME_generate_signal(Modulation, ChannelBW), a random configuration of active and inactive channels is used for testing.

      Outputs:

      - TX - Structure array containing, among other fields, the generated multi-channel signal.

      - PARAM - is a structure array containing relevant information on the baseband signal processing, for example: OFDM signals bandwidth, frequency bands, length of the data vectors, the sampling frequency.

      1.1-Signal back-off

      - Use code line: uBB=TX.uBB*GainBB

      Line description: This line uses the gain GainBB ranging from 0 to ~1 to set the amplitude of the baseband generated signal and to control the input power. The absolute value of the IQ signals to be sent to the remoteUPCLab must not exceed 1; if the value exceeds 1, the PA will start clipping and generate an error message. All signals are generated with the same average power but different PAPR, so users can select lower gain values if desired to work with higher back-off levels.

       2-Waveform UL-PA excitation-DL

      Note: The absolute value of the TX waveform TX.xBB cannot exceed 1.

      [RX]=TX_RX_Remote_TIME_WebLAB(TX.xBB, MISC, timeout) 

      This function is used to upload the TX.xBB signal to the remoteUPCLab SFTP MATLAB server (in the control PC) for further generation with the VSG. The SSA will then capture the RX waveform at the output of the PA after down conversion and the SFTP Matlab server will send this waveform back to the user through the RX structure which also includes relevant power metrics given by the measurement setup and relevant hardware settings information. 

      Inputs:

      - TX.xBB - Signal to send to the SFTP server. Its absolute value cannot exceed 1, but will be processed if its absolute value does not exceed 2, but please be mindful that PA clipping will occur.

      - MISC - This parameter is used to define further extra parameters:  MISC.n_AVG lets you choose the averaging form 1 to 3, MISC.SigAlignment lets you enable/disable (1/0) baseband signal alignment.

      - timeout - Specifies the time in seconds that the system will wait for the RX response before giving up; adjust it if more time is needed.

      3-Scoring

      [SCORE]= TIME_meas_score(RX,TX,PARAM,iteration);

       Function description: This function provides the SCORE.

      Inputs:

      - RX - Structure array containing, among other fields, the measured output of the PA.

      - TX - Structure array containing, among other fields, the generated multi-channel signal.

      - PARAM - Structure array containing information on the most relevant remoteUPCLAb parameters.

      - iteration - is the current iteration of the DPD algorithm

      Outputs:

      - SCORE - is the numerical value calculated as defined in section III.

      REFERENCES

      [Qua18] R. Quaglia and S. Cripps, "A Load Modulated Balanced Amplifier for Telecom Applications," in IEEE Transactions on Microwave Theory and Techniques, vol. 66, no. 3, pp. 1328-1338, March 2018, doi: 10.1109/TMTT.2017.2766066.

      [Li23] W. Li, G. Montoro, W. Thompson, K. Chuang and P. L. Gilabert, "Digital Shaping and Linearization of a Dual-Input Load-Modulated Balanced Amplifier," 2023 International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMIC), Aveiro, Portugal, 2023, pp. 1-3, doi: 10.1109/INMMIC57329.2023.10321805.

      [Gui22] E. Guillena, W. Li, G. Montoro, R. Quaglia and P. L. Gilabert, "Reconfigurable DPD Based on ANNs for Wideband Load Modulated Balanced Amplifiers Under Dynamic Operation From 1.8 to 2.4 GHz," in IEEE Transactions on Microwave Theory and Techniques, vol. 70, no. 1, pp. 453-465, Jan. 2022. doi: 10.1109/TMTT.2021.3091672.