Implementation of OFDM acoustic modem using TMS320VC5416

This paper presents the design and implementation result of a real-time acoustic OFDM modem transmitted over the air using TMS320VC5416 DSP. The system uses PC speaker and vocal dynamic microphone as the transducers. The sampling frequency is 48 kHz with 128 sub-carriers using 256 points FFT. The system uses selective mapping method (SLM) as PAPR reduction technique to reduce the signal clipping and ABPL techniques to equalize the received CNR on all sub-carriers so that the symbol error probability are also equalized. The test results show that these techniques are working as expected. The Eb/No curve are close to QAM64 even if the channel are severely distorted. The system can transmit at 66250 bits/sec with bit error rate 1.0×10-5 at Eb/No 16.72 dB. The system has not included the carrier synchronization yet. This will be the future work.