A novel speech-like symbol design for data transmission through GSM voice channel

This paper introduces a new approach to design speech-like (SL) symbols in order to transmit digital data through global system for mobile communications (GSM) voice channel. Using these symbols leads to design a GSM voice channel data modem to modulate and demodulate data on enhanced full rate voice codec. Designing a set of time-symbols is an offline procedure with the aim of minimizing symbol detection error. This modem could be useful in the situations where real-time data communication with high priority is needed. Data is encoded into SL symbols to be transmitted through GSM voice channel. At the receiver side, the received SL symbols are decoded back to data. We present a full procedure of symbols design and implement it in a real system. We achieved a bit rate of 2 kbps with 1.5 × 10^-5 symbol error rate (SER) using the proposed method.