In one exemplary embodiment, a wireless communication apparatus transmitting data by using several sub-carriers. The wireless communication apparatus comprises a signal modulator, a signal processor, a storage, a computing processor, and a transmitter. The signal modulator generates a modulated signal in time domain based on the data. The signal processor performs signal processing on the modulated signal, and comprises a window module and a filter module. The window module performs windowing operation on the modulated signal to generate a window-operated signal. The filter module performs filtering operation on the window-operated signal to generate a transmitting signal in time domain. The computing processor performs operations of setting up the window module and the filter module according to a window characteristic function and a filter characteristic function. The transmitter transmits the transmitting signal.