Only recently has our technology advanced to the point that commercial application of spread-spectrum signaling is economically feasible. This has motivated a number of companies and individuals to seek new ways to benefit from spread-spectrum techniques in commercial systems and products. In this paper, we give a very brief overview of spread spectrum signaling. We then consider applications to satellite mobile applications as well as indoor wireless applications. An overview is presented of several proposals to provide worldwide personal communications through satellite-based spread-spectrum systems, the tradeoffs to be considered, and the controversies involved. A description of a high-capacity wireless office telephone system serves to illustrate how spread-spectrum signaling may be useful in this environment. Finally, we describe a number of digital processing algorithms and devices that implement spread spectrum signaling in a cost-effective manner.>

In this paper we present a new vocoder called the residual-excited linear prediction (RELP) vocoder. The concept of the RELP vocoder combines the advantages of linear predictive coding (LPC) and voice-excited vocoding. In the RELP system, vocal tract modeling is done by the LPC technique, and the LPC residual signal is used as the excitation signal. After low-pass filtering the residual signal is coded by adaptive delta modulation and is spectrally flattened before being fed in the LPC synthesizer. The range of the transmission rate is typically between 6 and 9.6 kbits/s; the synthetic speech in this range is quite good. As the transmission rate is lowered, the synthetic speech quality degrades very gradually. Since no pitch extraction is required, the vocoder is robust in any operating environment.