The objective of the IMS2017 Power Amplifier Linearization through DPD SDC#6 is to design an appropriate DPD algorithm for the linearization of a 4G handset power amplifier (PA) with dynamic supply to be used in 4G handsets operating with dual-band OFDM-like waveforms. The students willing to participate may register here before March 31st 2017.
The participants will be able to access via world wide web (www) the remoteUPCLab to upload the predistorted baseband I/Q signals and the supply waveform to the corresponding VSG and retrieve the PA response and the baseband I/Q output signal by the SSA.
The test setup to be employed both for preparing the contest and participating in the competition is detailed in the Measurement setup submenu. In the DPD-Competition, to be held in the IMS2017, the same hardware test setup will be made available to the participating students. They will be able to tune their DPD algorithms and upload their predistorted and supply signals. Each team will have a period of 25 minutes to tune its DPD model. When ready (or at the end of that 25 minutes period), the target input signal will be given to the team and its DPD will generate the predistorted and bias supply signals, which will be uploaded to the signal generator and supply modulator. At that moment, the jury will measure (and register) the performance metrics used to compute the overall score achieved by the team. This last process will be performed 3 times and the best score will be chosen.
The scoring algorithm will reward maximizing the output power, which translates both in system gain and more efficient PA operation, the PA efficiency itself (which is impacted not only by the output power but the modulated supply signal), the adjacent channel power ratio (ACPR) for spectral mask fulfillment, and the normalized square error (NMSE) quantifying the likelihood between the original baseband Tx signal and the signal taken at the output of the PA (after down conversion, time-alignment and gain correction), after applying the DPD.
Rules: In accordance with IMS general rules, it is required that the designed algorithms are principally the work of the students. Undergraduate and graduate students’ DPD algorithms will not be separately judged under two distinct contest levels, but combined. Further information is found here.
Prizes: 1st team gets $1200 and 2nd team $800.
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.
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:
remoteUPCLab_user_IMS2017.zip (MATLAB scripts, last update)
Info_Signals_Scoring_Files_IMS2017_DPD_contest_v5.pdf (instructions, last update)
NOTE: A MATLAB VERSION R2014b OR HIGHER 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 play the “Example_test_IMS2017.m” script to check that the MATLAB functions are running OK (control messages are displayed during waveform Tx/Rx process) and obtain an initial negative score before applying predistortion.
The overall procedure can be summarized following these steps:
- Use the script in: \toolbox.IMS2017\IMS2017_generate_signal.m
- Function call: [gBB,xsupply,PARAM] = IMS2017_generate_signal(GainBB)
- Function description: This function provides i) a baseband user-scaled dual-band signal composed by 2 OFDM signals (of 10 MHz and 5 MHz bandwidth) at -40MHz and 40MHz, relative to the center frequency of the PA (gBB), ii) the “slow envelope” supply signal (xsupply) and iii) a struct array containing the signal generation and acquisition settings (PARAM). The GainBB variable, ranging from 0 to 1, sets the maximum absolute value of the dual-band waveform.
- Note that:
(i) For every new signal generation random data is employed which may lead to different PAPR waveforms.
(ii) A slow version of the original dual-band signal’s envelope will be generated as explained in the user instructions.
(iii) The users MUST AVOID MODIFYING the way the supply envelope is being generated. If they apply modifications to the original baseband signal (i.e. though CFR for instance), they can use the “Supply_Envelope_Generation” function, which is coded inside the “IMS2017_generate_signal” function previously described, to generate the new xsupply signal.
(iv) The participants may also optionally consider time-alignments between the supply envelope and the dual-band I/Q signal sent to the remoteUPCLab
(v) GainBB values higher than 1 are not allowed. The dual band signal power may be increased but the initial power ratio (in dB) between each of the two bands must be kept.
- Use the script in: \toolbox.IMS2017\ IMS2017_PA_meas.p
- Function call: [RX] = IMS2017_PA_meas(xBB,xsupply)
- Function description: This function is used to upload the user’s Tx and slow envelope waveforms to the remoteUPCLab FTP 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 FTP 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.
- Note that:
(i) The code of this script has been obfuscated to protect the FTP server operation and preserve its configuration.
(ii) The sampling process is started in the SSA in a completely random fashion so synchronization is required before using the output data.
(iii) the measurement analog baseband I/Q data is sampled at 122.8 MHz which is also the maximum allowed I/Q signal baseband bandwidth ([-61.44, 61,44] MHz). The Tx, Rx and slow envelope signals have the same waveform length (122880 samples).
(iv) The absolute value of the Tx waveform cannot exceed 1 in which case the PAPR value needs to be higher than 6 dB, and the supply signal PAPR cannot be lower than 3 dB.
- Use the script in: \toolbox.IMS2017\IMS2017_meas_score_May2017.m
- Function call: [SCORE]= IMS2017_meas_score(RX,gBB,PARAM)
- Function description: This function provides the numerical SCORE value of the DPD linearizer for each experiment iteration. It takes into account the overall output power (calculated in dBm), the ACPR and NMSE values (in dBc and dB respectively) calculated on each band, and the PA efficiency (given in %). The RX structure provides the PA output power levels and the power consumption of the complete PA ET evaluation module and the Rx waveform needed to calculate the ACPR and NMSE values.
- Note that:
(i) ACPR values below -45 dBc add points to the score while values above -45 dBc reduce the score.
(ii) Same occurs with the NMSE values considering a -33 dB threshold but, however, the NMSE contribution to the score is only considered if the maximum -45 dBc ACPR value is met. In such a case the NMSE points are weighted by a factor of 0.5.
(iii) Mean PA output power levels in excess of 20 dBm improve the score while those below reduce the score. This parameter is weighted by a factor of 10 but its contribution is only considered when both the ACPR and NMSE minimum requirements are met and the power ratio between the two bands is kept less than or equal to 0.5 dB.
(iv) The efficiency (in percentage points) is also added to the score only when the ACPR and NMSE minimum requirements are fulfilled and the power ratio between the two bands is kept. For further detail on the scoring algorithm read the user instructions.
Our ambition is to have the remoteUPCLab permanently available. However, please respect that we may need to shut it down temporarily for maintenance. Information about planned down-periods will be announced in the News page. Also, we have an indicator on the main page that will indicate whether remoteUPCLab is up and running (or not).