Adaptive modem

This paper presents a new adaptive modem prototype. This system generates adaptive waveforms for different communication channels. We have here a signal detection method which uses the discrete Fourier transform (DFT). We use digital modulation schemes in digital data transmission over telecommunication networks and radio channels. Basically we use AM, FM and PM modulation adaptively which means that we can select the best modulation scheme (MFSK, MPSK, QAM) for different channels. The number of transmitted symbols, bit rates, sampling frequencies and symbol times (numbers of samples in DFT) are parameters in our adaptive modem. Our modem tests over radio channels give some ideas for Internet access or tactical military radio access. The data transmission in our system is speech like and promises a greater data throughput than standard solutions of the ITU-T.