IEEE Transactions on Communications

To cope with the effects of channel errors, robust adaptive quantization schemes contain a leakage parameter in the step-size adaptation algorithm. Unfortunately, this mechanism also introduces its own distortion in the form of reduced dynamic range of the step size which causes the signal-to-noise ratio to drop appreciably at the far ends of the range of input signal intensities typically associa... View full abstract»

An 11.5 m 30/20 GHz band Cassegrain antenna has been developed for a Japanese domestic satellite communication system earth station. In order to form an economical satellite communication network, the earth station antenna is required to be installed on the top of a telephone office building in a large city. Therefore, interference with terrestrial radio relay systems and antenna load on a buildin... View full abstract»

Lender's partial response baseband system model is analyzed, extended and compared with two other partial response models. The feasibility of each system model in practical implementation is assessed. The effects of filter imperfections and of channel nonlinearities on the performance of QPRS digital radio systems is analyzed by means of computer simulation. View full abstract»

A packetized speech multiplexer differs from a circuitswitched TASI system in that the presence of a packet buffer allows a tradeoff where the TASI advantage can be increased at a cost in packet delay. This tradeoff is investigated via a simulation. Results are presented to show the relations between TASI advantage and delay, for both an average delay criterion and a maximum delay criterion. It is... View full abstract»

In a digital transmission network including 1.5 Mbit/s and higher speed systems, it is desirable to signal service outages of the higher speed systems to the multitude of affected channel banks terminating the 1.5 Mbit/s systems in order to avoid unnecessary maintenance activity. To do this, it is proposed that a special signal be transmitted to the channel banks from the multiplex terminating the... View full abstract»

The effects of fading on the performance of a spread spectrum multiple-access communication system using direct sequence modulation are investigated. General series expansions are developed for the average probability of error and specific results are given for the irreducible error rate associated with propagation over independent Rician fading channels or correlated Rayleigh fading channels. Sim... View full abstract»

Complex protocols are used to coordinate remote activities in computer networks. To insure proper operation, formal techniques of protocol definition and validation have been proposed, and developed to the point that they can be applied to actual protocols. However, much work remains to be done in order to cope with protocols of ever-increasing complexity; in particular, those coordinating the act... View full abstract»

This paper addresses the general problem of estimating the maximum number of PCM systems allowed on one cable repeater section given representative PCM repeater characteristics and cable data. NEXT is analyzed, and a regenerative repeater is characterized by a graph of acceptable NEXT attenuation versus repeater section loss. Crosstalk data are utilized by statistical summation (convolution) using... View full abstract»

Cumulative attenuation distributions for one year and relationships between attenuations at 19 GHz and 28 GHz are presented for an earth-space propagation path terminating at Crawford Hill, New Jersey. An example from the distributions indicates that 20 dB attenuation was exceeded for 0.012% of the year at 19.04 GHz and for 0.06% at 28.56 GHz. For both frequencies the polarization was linear and o... View full abstract»

This paper examines the key issues involved in choosing synchronization techniques applicable to both terrestrial and satellite switching networks. The terrestrial networks considered involve circuit switching, message switching, packet switching, and other integrated voice/data nodal configurations. The satellite networks considered involve time-division multiple access (TDMA) systems and their a... View full abstract»

A combined source-channel coding approach is described for the encoding, transmission and remote reconstruction of image data. The source encoder employs two-dimensional (2-D) differential pulse code modulation (DPCM). This is a relatively efficient encoding scheme in the absence of channel errors. In the presence of channel errors, however, the performance degrades rapidly. By providing error con... View full abstract»

This paper describes a general method for calculating the power spectra of zero substitution coded signals and applies this method to calculate the B3ZS signal spectrum of the DS-3. Many digital radio systems transmit a signal which consists of DS-3 level baseband signals. Therefore, knowledge of the B3ZS spectral characteristics is important in DS-3 level interference and systems studies. The met... View full abstract»

Decision and estimation algorithms for a signal of asynchronous generation are treated with emphasis on waveform estimation. A simplified model for source statistics is assumed. Starting with a supervised learning model, two algorithms of the non-supervised type are derived. Their estimation error performance is studied by computer simulation. View full abstract»

Quadriphase receivers, like biphase receivers, have the ability to false lock on a sideband of the data modulation. The theory associated with this phenomenon for receivers of binary phase-shift-keying (BPSK), using Costas loop demodulation, has recently been documented in the literature. This paper considers the corresponding theory for receivers of balanced quadriphase-shift-keying (QPSK) employ... View full abstract»

An analytical method to predict the data pattern dependent jitter is presented. Results obtained are shown to be in excellent agreement with those obtained by computer simulation and laboratory measurement. In order to find methods that can generate an ISI (intersymbol interference) and jitter-free bandlimited Nyquist signal, a double-intervaled raised cosine and its spectral characteristics are s... View full abstract»