An Efficient Speech Coding Technique for Secure Mobile Communications

Speech coding for secure mobile communication is a challenging task since encrypting the digitized speech signal adds overheads and randomizes the bit stream to a level where recovery of original signal becomes difficult. The commercially available speech coders are unbefitting for transmission of encrypted speech as it requires a low bit speech coding with preserved speech characteristics so that it can be transmitted over a bandwidth-limited channels with intelligible speech. In this paper, we present an efficient low bit-rate (1.9 kbps) speech coding technique to transmit encrypted speech over Global System for Mobile communications (GSM). Different speech characteristics such as pitch, energy and Line Spectral Frequencies (LSF) are extracted and preserved before compression and encryption speech. Empirical results show that the proposed speech coder can be used effectively in low bit rate applications such as secure voice communications.