The chirp Z-transform permits large bandwidth (i.e. high speed) analog devices to be used to compute the Discrete Fourier Transform (DFT). Such Implementations are often faster and/or smaller than all digital Fast Fourier Transforms (FFT's), but suffer from accuracy limitations imposed by the analog devices. In this paper, we present a nested algorithm that permits excess bandwidth of the analog device to be exploited in order to compute the DFT more accurately. The nested structure can be realized with a single analog device, and can be trained to the errors associated with the device. Algorithm performance is verified through computer simulations in which DFT accuracy is limited due to fixed tap weight errors in the FIR filter portion of the chirp Z-transform.

Integrated packet-switched networks have potential for providing improved performance by dynamically sharing transmission bandwidths between various users and user types, but new flow control methods are needed to deal with packetized voice traffic. This paper describes a packet voice flow control concept based on embedded speech coding. Results are presented from a computer simulation study of the technique in the context of a multilink wideband packet speech network. Several control methodologies are described, leading to an end-to end feedback approach that achieves stable operation and efficient utilization of network resources by adaptively matching transmitted voice bit rates to prevailing network conditions. Issues in the design of embedded speech coding algorithms are reviewed and a candidate structure based on channel vocoding principles is presented, along with the subjective results of some preliminary listening tests

Voice communication networks have traditionally been designed to provide either analog signal paths or fixed-rate synchronous digital connections between individual subscribers. These designs were aimed at accommodating the "streamlike" character of speech, which has traditionally been considered to flow from source to destination at a more or less constant rate. By way of contrast, interactive and computer-to-computer data transactions tend to be "bursty" in nature, and this has given rise to the development of packet-switching methods for data communications. The dichotomous nature of these two major traffic classes and the apparent conflict between the types of network services they require has resulted in the deployment of separate military communications facilities for voice and data. A challenge in the design of future systems is to achieve overall economy and flexibility in the allocation of resources via the efficient integration of both traffic types in common network facilities. This paper summarizes a number of advanced concepts for switching and flow control of combined voice and data traffic in integrated environments. Performance characteristics are described based on analysis results and computer simulation studies for both multilink terrestrial and broadcast satellite network topologies.

This paper introduces a class of finite-state algorithms which characterize self-similar space-filling curves. The curves enable one to continuously map a line onto anN-dimensional cube, and find application in compressing the bandwidth of arbitrary waveforms. The bandwidth compression is effected in return for an increased susceptibility of the signal to perturbations. The algorithms are represented in a diagrammatic form which enables one to convert theNcoordinates of a point in a cube into a single number representing the distance along a space-filling curve, or vice-versa, merely by visual inspection. The diagrams are always finite in size and may be constructed by following a rather simple numerical procedure.