This paper describes the experimental investigation of orthogonal time-frequency space(OTFS) modulation using a 28 GHz multi-user distributed multiple-input multiple-output(D-MIMO) testbed in over-the-air (OTA) and mobility environments to enhance cellthroughput in a millimeter-wave band. We build the D-MIMO testbed having newlydeveloped OTFS modulator and demodulator, and measured OTFS signals and orthogonalfrequency-division multiplexing (OFDM) signals with up to four user simultaneousconnections on an actual office floor. Additionally, the Doppler effect on OTFS signals ismathematically analyzed and is confirmed in the measurements. OTFS indicates higherrobustness in time-variant channels than OFDM. The error vector magnitude (EVM) andsystem throughput of OTFS are ?22 dB and 1.9 Gbps with 100 MHz signal bandwidth,respectively. To our knowledge, this is a first paper describing the OTA measurements ofEVM, throughput, and spectral efficiency using OTFS modulation on the 28 GHz coherentbeamforming system.
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