A millimeter-wave system at W-band with sixteen Quadrature Amplitude Modulation (16QAM) optical Orthogonal Frequency Division Multiplexing(OFDM) signals transmission is experimentally demonstrated. Intra-Symbol Frequency-domain Averaging(ISFA) based channel estimation and the Discrete Fourier Transform-Spread(DFT-Spread) techniques are employed to improve the system performance. A 21.2 Gbit/s 16QAM OFDM signal at 84.5 GHz can be successfully transmitted over 2 m wireless delivery under a 7% soft-decision forward-error-correction threshold(bit error rate of 3.8×10-3).