A LabVIEW-Based Implementation of Real-Time Adaptive Modulation for Underwater Acoustic OFDM Communication

Adaptive modulation is appealing for underwater acoustic (UA) communication systems in order to improve the system power and spectral efficiency by varying transmission parameters according to the channel condition. This paper presents a real-time orthogonal frequency-division multiplexing (OFDM) based adaptive UA communication system, implemented using the National Instruments (NI) CompactDAQ device and the LabVIEW software. A self-adapting algorithm is used to select the best modulation mode for time-varying UA channels. The signal-to-noise ratio (SNR) is calculated at the receiver and used as a performance metric to switch the modulation mode which is fed back to the transmitter for data transmission. The proposed software defined implementation is flexible and simplifies the prototype design compared to conventional digital signal processor (DSP)-based design. The experimental results verify the superiority of the adaptive transmission.