Mixed-signal processing for efficient 5G & beyond transmitters

Responsible: David López

Team members: Nikolaos Bartzoudis, Pepe Rubio, Luis Blanco


Focused R&D area 1

  • Research, fast prototyping and experimental validation of digitally-assisted linearization techniques for 5G and beyond efficient transmitter and PA system architectures.


Related projects

Developed technologies

  • Low-complexity CFR and wideband DPD algorithms based on dimensionality reduction techniques for wideband systems:
    • Application: Ku-band microwave backhaul GaAs PA outdoor unit, C-band backhaul GaN PA indoor unit, up to 112 MHz BW 4ch 1024-QAM.
      • Techniques: Peak cancellation (PC) CFR, closed-loop direct learning (DL) DPD least squares (LS) estimation, principal components analysis (PCA) [1], [2].
    • Application: S-band 4G macrocell access (downlink), GaN PA, 40 MHz BW burst-like OFDM and non-contiguous carrier-aggregated LTE-like signals with up to 70 MHz total BW.
      • Techniques: PC-CFR, DL-DPD LS, amplitude decomposition and long term memory effects modelling, waveform expansion and IQ mesh [3], [4], spectral-weighting orthogonal matching pursuit (SW-OMP) with recursive least squares estimation (RLS) [5].
    • Application: UHF microcell 5G-like access (downlink), Class-J GaN PA, 5-10 MHz LTE-like and up to 80 MHz intra-band contiguous carrier-aggregated FBMC.
      • Techniques: PC-CFR, DL-DPD LS, Rx path BW/Fs reduction [6], CFR+DPD for LTE-FBMC spectral coexistence [7] , block-deflated adaptive PCA with independent parameter estimation based on a modified version of the generalized Hebbian algorithm (CGHA) [8] [9], and dynamic basis selection for DPD adaptation using PCA+PLS [10] [11]
    • Application: L-band RF macrocell access (uplink) with commercial 4G handset PA, 5-10 MHz LTE-like dual-band signal (80 MHz spacing).
      • Techniques: Dual-band envelope tracking (ET) DPD (3D-DPD), combined with multi look-up tables (LUT), partial least squares (PLS) and OMP [12], [13].
  • DPD for massive bandwidth systems and multi-branch efficient transmitter architectures
    • Application: Cable TV PA system, DOCSIS 3.0 up to 1.2 GHz BW.
      • Research and experimental evaluation of CFR & DPD techniques for GHz-BW PA systems with overlapping even and odd in-band distortion and highly efficient PA architectures for multi-channel bandwidth aggregation TXs.

Targeted R&D effort

  • Wideband MIMO DPD algorithms for cost-effective highly-performing 5G (and beyond) digital MIMO and hybrid beamforming BS front-end architectures.
    • Application: Sub-6 GHz and Ka-band mm-wave radio access for BS-like equipment for 100-400 MHz signal bandwidth.
  • Beyond-5G massive bandwidth linearization schemes based on hybrid analog-digital predistortion and multi-branch DPD-assisted efficient transmitter architectures (LMBA, outphasing, etc.).
    • Application: Sub-6 GHz radio access UE/BS, Ka-band mm-wave radio access BS for beyond 400 MHz overall signal bandwidth, E-band backhaul, 5G satellite backhaul GS, and cable distribution systems.
    • Application to massive bandwidth optical and photonic communication systems.


Focused R&D area 2

  • Real-time SoC/RFSoC implementation of wideband digital linearization solutions for 5G radio access and terrestrial/satellite backhaul digital front-ends.


Developed technologies

  • Multidimensional predistorter for 5G terminals with wideband supply-modulated PAs (on-going).
  • Hardware-in-the-loop real-time platform to prototype wideband DPD solutions.
  • Digital Front End (DFE) and system interfacing for a digitally linearized 5G multi-antenna Remote Radio Head (RRH) .
  • FPGA implementation of a wideband DPD for microwave backhaul systems (real-time dual-chain polyphase HDL architecture) [14].

Related projects

Targeted R&D effort

  • Efficient DPD FPGA implementation for dynamic-supply and dynamic-load PA architectures for 5G BS and UEs.
  • Massive BW DPD FPGA implementation through parallelized architectures for mmWave radio access and backhaul.