부산대학교 도서관

One of the most important objectives in mobile communication systems is secure data communication (including text, picture, video and voice) especially. in high bit rate. For this reason, in this paper, a new procedure is proposed in which the intended data or voice is modulated onto speech-like waveforms; Then the modulated waveforms are transmitted over the global system for mobile communications (GSM) voice channel. Then, these waveforms are demodulated at the receiver. Finally, the input data to the modulator is compared to the output data from the demodulator based on bit error rate (BER). In this work, we propose an appropriate modem for the GSM Full Rate (FR) speech codec by mapping data onto the fundamental parameters related to formants in a speech-like waveform including phases, frequencies, energy of frame and pitch frequencies. The proposed model has been evaluated for a GSM-to-GSM connection. Conducting different simulations we observed that the proposed approach results in a bit error rate (BER) of 0.005% when Signal-to-Noise Ratio (SNR) is 10 dB in a 0.8kbps channel. As a result, proposed method can be considered as a favorable choice for robustness to additive noise.