Towards Practical Indoor Positioning Based on Massive MIMO Systems. 2019 IEEE 90th Vehicular Technology Conference (VTC2019-Fall), 1-6, September 2019. [PUMA: extractor;Artificial multiple-output myown from:sdnr (artificial communication;neural nets;telecommunication system;neural extraction arrays;Feature structure;phase measurements;Training;Antenna radio;learning system;user intelligence);MIMO acquisition;feature NN localization communication;indoor neural data networks;channel branch;indoor extraction;indoor systems;indoor scenarios;recall positioning MIMO accuracy;training networks;Antenna information;multiple-input state system;IPS computing;massive task;tailored communication]