Transmission of data on analog speech channel by spread spectrum modulation
Jun Suzuki, B. Hingdi, H. Yashima · 2002
Sometimes it is requested to transmit data together with speech signal through a telephone channel. This paper proposes that low bit-rate of digital data are spread over a speech signal and transmitted through an analog telephone channel. In this method, the speech signal acts as noise for the data channel, and the digital signal acts as noise for the speech channel. Direct sequence modulation is employed for data transmission. A data rate of 22 bps is achieved at the BER of 10/sup -3/ when the noise is almost not perceived.