Showing papers in "IEEE Transactions on Communications in 1977"
TL;DR: An analysis of an asynchronous phase-coded spread-spectrum multiple-access communication system reveals which code parameters have the greatest impact on communication performance and provides analytical tools for use in preliminary system design.
Abstract: An analysis of an asynchronous phase-coded spread-spectrum multiple-access communication system is presented. The results of this analysis reveal which code parameters have the greatest impact on communication performance and provide analytical tools for use in preliminary system design. Emphasis is placed on average performance rather than worst-case performance and on code parameters which can be computed easily.
1,723 citations
TL;DR: A Fast Discrete Cosine Transform algorithm has been developed which provides a factor of six improvement in computational complexity when compared to conventional DiscreteCosine Transform algorithms using the Fast Fourier Transform.
Abstract: A Fast Discrete Cosine Transform algorithm has been developed which provides a factor of six improvement in computational complexity when compared to conventional Discrete Cosine Transform algorithms using the Fast Fourier Transform. The algorithm is derived in the form of matrices and illustrated by a signal-flow graph, which may be readily translated to hardware or software implementations.
1,301 citations
TL;DR: A statistical model, based on extensive experimental data, was established to characterize the urban radio propagation medium in various urban environments and the peaks of the multipath response were analyzed statistically concerning the distribution of the path strength and the path arrival time.
Abstract: A statistical model, based on extensive experimental data, was established to characterize the urban radio propagation medium in various urban environments. Describing the medium by a linear filter, the peaks of the multipath response were analyzed statistically concerning the distribution of the path strength and the path arrival time. The statistical properties of these quantities depend on the modulation delay time. The resulting model can be used for simulation experiments in order to avoid costly hardware tests of ad hoc systems.
1,013 citations
TL;DR: This paper provides a unified presentation of packet broadcasting theory, derived some properties of power-limited packet broadcasting channels, showing that the throughput of such channels can approach that of equivalent point-to-point channels.
Abstract: Packet broadcasting is a form of data communications architecture which can combine the features of packet switching with those of broadcast channels for data communication networks. Much of the basic theory of packet broadcasting has been presented as a byproduct in a sequence of papers with a distinctly practical emphasis. In this paper we provide a unified presentation of packet broadcasting theory. In Section II we introduce the theory of packet broadcasting data networks. In Section III we provide some theoretical results dealing with the performance of a packet broadcasting network when the users of the network have a variety of data rates. In Section IV we deal with packet broadcasting networks distributed in space, and in Section V we derive some properties of power-limited packet broadcasting channels, showing that the throughput of such channels can approach that of equivalent point-to-point channels.
745 citations
TL;DR: A new global convergence theorem for noncontinuous iteration algorithms is developed that converges, with successive updates of the routing tables, to the minimum average delay over all routing assignments.
Abstract: An algorithm is defined for establishing routing tables in the individual nodes of a data network. The routing table at a node i specifies, for each other node j , what fraction of the traffic destined for node j should leave node i on each of the links emanating from node i . The algorithm is applied independently at each node and successively updates the routing table at that node based on information communicated between adjacent nodes about the marginal delay to each destination. For stationary input traffic statistics, the average delay per message through the network converges, with successive updates of the routing tables, to the minimum average delay over all routing assignments. The algorithm has the additional property that the traffic to each destination is guaranteed to be loop free at each iteration of the algorithm. In addition, a new global convergence theorem for noncontinuous iteration algorithms is developed.
676 citations
TL;DR: In this article, an efficient adaptive encoding technique using a new implementation of the Fast Discrete Cosine Transform (FDCT) for bandwidth compression of monochrome and color images is described.
Abstract: An efficient adaptive encoding technique using a new implementation of the Fast Discrete Cosine Transform (FDCT) for bandwidth compression of monochrome and color images is described. Practical system application is attained by maintaining a balance between complexity of implementation and performance. FDCT sub-blocks are sorted into four classes according to level of image activity, measured by the total ac energy within each sub-block. Adaptivity is provided by distributing bits between classes, favoring higher levels of activity over lower levels. Excellent performance is demonstrated in terms of mean square error and direct comparison of original and reconstructed images. Results are presented for both noiseless and noisy transmission at a total rate of 1 bit and 0.5 bit per pixel for a monochrome image and for a total rate of 2 bits and 1 bit per pixel for a color image. In every case the total bit rate includes all overhead required for image reconstruction and bit protection.
509 citations
TL;DR: This article surveys the modeling, analysis, and design of computercommunication networks developed with the packet-switched Advanced Research Projects Agency Network (ARPANET) in mind, although the principles extend to more general networks.
Abstract: The problem of data transmission in a network environment involves the design of a communication subnetwork. Recently, significant progress has been made in this technology, and in this article we survey the modeling, analysis, and design of such computercommunication networks. Most of the design methodology presented has been developed with the packet-switched Advanced Research Projects Agency Network (ARPANET) in mind, although the principles extend to more general networks. We state the general design problem, decompose it into simpler subproblems, discuss the solutions to these subproblems, and then suggest a heuristic topological design procedure as a solution to the original problem.
385 citations
TL;DR: By using optimum and (locally optimum) detection algorithms (canonically and explicitly derived), substantial savings in signal power and/or spectrum space can be achieved for operation in these highly nonGaussian interference environments.
Abstract: Because communications systems are seldom significantly interfered with by classical white Gaussian noise, it is necessary to consider other, appropriate (and tractable) interference models, if realistic estimates of system performance are to be obtained for the general spectral-use environment. For this purpose, Middleton's recently developed canonical statistical-physical model of "impulsive" interference is applied to real-world communication channels. The principal features of this model are first summarized, including the statistical relations required for the solution of signal detection problems. [Excellent agreement of these model statistics with correspondingly measured statistics is also noted.] The model for narrow-band impulsive interference (Class A noise, a subset of the overall model) is next specifically applied to an important class of coherent signal detection problems. Algorithms for error probabilities in optimum detection are then obtained, along with performance bounds, for the same error probabilities. Since it is known that in order to gain significant improvement over current receivers, the number of (essentially) independent samples of the received interference waveform must be enlarged (i.e., large "processing gains"), the performance results here are given parametrically in the number of samples, or equivalently, in the time-bandwidth product. Performance of current suboptimum receivers is then obtained and compared to the optimum performance. It is shown that very substantial savings in signal power and/or spectrum space can usually be achieved by using the indicated optimal algorithms. Since physical realization of the completely optimum detection algorithms cannot, in general, be economically realized, the somewhat more conservative, corresponding locally optimum Bayes detection (LOBD) receivers are derived. In general, these LOBD structures require adaptive, highly non-linear filters, preceding the conventional correlation detector elements characteristic of optimum receivers for Gaussian interference. Performance for these non-linear, optimum threshold systems is then determined, specifically in Part I for coherent reception.
368 citations
TL;DR: Topological design problems for large-scale topological design systems, including the concentrator location problem, the terminal assignment problem,The terminal layout problem (the constrained minimum spanning tree problem), and the distributed network topological layout problem are discussed.
Abstract: A cost-effective structure for a large network is a multilevel hierarchy consisting of a backbone network and a family of local access networks. The backbone network is generally a distributed network, while the local access networks are typically centralized systems. In special cases, the network may consist primarily of either centralized or distributed portions. This paper discusses topological design problems for such systems, including the concentrator location problem, the terminal assignment problem, the terminal layout problem (the constrained minimum spanning tree problem), the distributed network topological layout problem, and the backbone node location problem. Recent algorithm research, including exact and heuristic problem solutions, are described and computational experience is given. Finally, open problems in large-scale topological design are reported.
295 citations
TL;DR: An analysis of the code sequence parameters that are most important to the communication performance of an asynchronous phase-coded spread-spectrum multiple-access communication system is presented.
Abstract: An analysis of the code sequence parameters that are most important to the communication performance of an asynchronous phase-coded spread-spectrum multiple-access communication system is presented. Previously known bounds and computational techniques for such parameters are surveyed. Some new results on mean-square correlation are included.
288 citations
TL;DR: The mean and variance of the time to acquire for single dwell time PN-type spread-spectrum systems for Markov chain model and the effects of Doppler and other imperfections of the original model are discussed.
Abstract: This paper develops the mean and variance of the time to acquire for single dwell time PN-type spread-spectrum systems. A model is specified, and then exact results are obtained by use of the generating function for the acquisition process. The paper is somewhat tutorial in that the analysis technique is developed in a logical step-to-step manner for the Markov chain model and can be readily used on other models. The effects of Doppler and other imperfections of the original model are discussed. Finally the results of the double dwell time system are presented and the appropriate modifications for Doppler effect are given.
TL;DR: The packet radio network described in this paper is an extension of the basic Hawaii work to a geographically distributed system involving the use of repeaters to achieve area coverage beyond line of sight, and provides added capabilities for authentication, antijam protection, and coexistence with other possibly different systems in the same band.
Abstract: Packet radio communications provides an effective way to interconnect fixed and mobile computer resources. The ALOHA System at the University of Hawaii first introduced this capability in the context of a single-hop system using off-the-shelf RF equipment with all terminals within line of sight of the central station. The packet radio network described in this paper is 1) an extension of the basic Hawaii work to a geographically distributed system involving the use of repeaters to achieve area coverage beyond line of sight, and 2) provides added capabilities for authentication, antijam protection, and coexistence with other possibly different systems in the same band. An overview of the packet radio system concept is given in this paper.
TL;DR: An error control technique that is a basic improvement over ARQ is presented, termed ARQ-with-memory (MRQ), which uses the simple idea of utilizing erroneously received blocks in an ARQ system for error control, retaining most of the other aspects of ARQ.
Abstract: Automatic-repeat-request (ARQ) is one of the most commonly used error control techniques today. In this paper, an error control technique that is a basic improvement over ARQ is presented. The technique uses the simple idea of utilizing erroneously received blocks in an ARQ system for error control, retaining most of the other aspects of ARQ. The technique is termed ARQ-with-memory (MRQ). The general MRQ system is described, and simple upper and lower bounds are derived on the throughput achievable by MRQ. The performance of MRQ with respect to throughput, message delay and probability of error is compared to that of ARQ by simulating both systems using error data from a VHF satellite channel being operated in the ALOHA packet broadcasting mode [9].
IBM1
TL;DR: The present paper is intended to review the state of affairs of analytic methods, queueing analysis techniques in particular, which are essential to modeling of computer communication systems.
Abstract: Modeling and performance prediction are becoming increasingly important issues in the design and operation of computer communications systems. Complexities in their configuration and sophistications in resource sharing found in today's computer communications demand our intensive effort to enhance the modeling capability. The present paper is intended to review the state of affairs of analytic methods, queueing analysis techniques in particular, which are essential to modeling of computer communication systems. First we review basic properties of exponential queueing systems, and then give an overview of recent progress made in the areas of queueing network models and discrete-time queueing systems. A unified treatment of buffer storage overflow problems will be discussed as an application example, in which we call attention to the analogy between buffer behavior and waiting time in the GI/G/1 queue. Another application deals with the analysis of various multiplexing techniques and network configuration. An extensive reference list of the subject fields is also provided.
TL;DR: It is found that CSMA provides excellent stable performance even with as large a population as 1000 terminals, and a simple adaptive retransmission control procedure is studied which provides a significantly improved channel performance which is insensitive to the population size.
Abstract: In two companion papers a method for multiplexing a population of terminals communicating with a central station over a packet-switched radio channel was introduced; this method is known as Carrier Sense Multiple Access (CSMA). CSMA, as with ALOHA multiaccess broadcast channels, has the unfortunate property that the throughput falls to zero as the channel load increases beyond a critical value. The dynamic behavior and stability of slotted ALOHA channels have been studied extensively and have led to a definition of stability. In this paper, similar techniques are used to analyze CSMA, which is shown to have a behavior not unlike that of ALOHA. However, contrary to ALOHA channels where steady-state performance is badly degraded when true stability is to be guaranteed, hence requiring dynamic control, we find that CSMA provides excellent stable performance even with as large a population as 1000 terminals. Furthermore, we study a simple adaptive retransmission control procedure which provides a significantly improved channel performance which is insensitive to the population size.
TL;DR: Several approaches for the evaluation of upper and lower bounds on error probability of asynchronous spread spectrum multiple access communication systems are presented, utilizing an isomorphism theorem in the theory of moment spaces.
Abstract: Several approaches for the evaluation of upper and lower bounds on error probability of asynchronous spread spectrum multiple access communication systems are presented. These bounds are obtained by utilizing an isomorphism theorem in the theory of moment spaces. From this theorem, we generate closed, compact, and convex bodies, where one of the coordinates represents error probability, while the other coordinate represents a generalized moment of the multiple access interference random variable. Derivations for the second moment, fourth moment, single exponential moment, and multiple exponential moment are given in terms of the partial cross correlations of the codes used in the system. Error bounds based on the use of these moments are obtained. By using a sufficient number of terms in the multiple exponential moment, upper and lower error bounds can be made arbitrarily tight. In that case, the error probability equals the multiple exponential moment of the multiple access interference random variable. An example using partial cross correlations based on codes generated from Gold's method is presented.
TL;DR: The processing gain concept is developed as a measure of a well-designed system's robust performance against independent wide-sense stationary interference in an idealized spread-spectrum communication system.
Abstract: This paper describes an idealized spread-spectrum communication system. The processing gain concept is developed as a measure of a well-designed system's robust performance against independent wide-sense stationary interference. Multipath and repeater jammer rejection, partial correlation problems, and security requirements are related to spread-spectrum code properties.
TL;DR: Basic analytical models for problems of dynamic and quasi-static routing in data-communication networks are introduced and control and estimation methods are used to construct algorithms for the solution of the routing problem.
Abstract: Basic analytical models for problems of dynamic and quasi-static routing in data-communication networks are introduced. The models are intended to handle the quantities of interest in an algorithmic form, and as such require only a minimal number of assumptions. Control and estimation methods are used to construct algorithms for the solution of the routing problem.
TL;DR: The Ali-Silvey class of distance measures is applied to the problem of designing quantizers for use in binary detection systems, and necessary conditions are established for the selection of quantizer parameters in this context.
Abstract: The Ali-Silvey class of distance measures is applied to the problem of designing quantizers for use in binary detection systems. To find optimal solutions the notion of quantization must be generalized slightly, and necessary conditions are established for the selection of quantizer parameters in this context. Local, or small-signal, conditions are also derived and these are seen to agree with asymptotic results based on Pitman efficiency. As an example, four-level generalized quantization for detecting a constant signal in additive generalizedGaussian noise is investigated.
TL;DR: It is shown that two useful detection criteria lead to quantization which gives the minimum mean-squared error between the quantized output and the locally optimum nonlinear transform for each data sample.
Abstract: Optimum quantization of data, primarily for signal detection applications, is considered. It is shown that two useful detection criteria lead to quantization which gives the minimum mean-squared error between the quantized output and the locally optimum nonlinear transform for each data sample. This criterion is an extension of the usual minimum distortion criterion for optimum quantizers. Numerical results show that it leads to optimum quantizers which can be considerably better in their performance for non-Guassian inputs than the minimum-distortion quantizers.
NEC1
TL;DR: An adaptive echo canceler with two echo path models is proposed to overcome the false adaptation problem for double-talking and it is shown that virtually complete double- talking protection is actually realizable by the new method.
Abstract: An adaptive echo canceler with two echo path models is proposed to overcome the false adaptation problem for double-talking. The echo canceler possesses two separate echo path models (EPMs), one (background EPM) for adaptively identifying echo path transfer characteristics and the other (foreground EPM) for synthesizing an echo replica to cancel out echo. The parameter values of the foreground EPM are refreshed by those of the background EPM, according to a transfer control logic, when the logic determines that the background EPM is giving a better approximation of echo path transfer characteristics than the foreground EPM. Completely digital hardware implementation is described. Using the hardware, it is shown that virtually complete double-talking protection is actually realizable by the new method.
TL;DR: Analysis and computer simulation over a single-pole channel show that the proposed scheme can reduce the complexity of the MLSE while retaining much of its performance advantages.
Abstract: A decision-feedback equalizer (DFE) is proposed as a prefilter which limits the complexity of a maximum-likelihood sequence estimator (MLSE) implemented by the Viterbi algorithm (VA) for channels having a long impulse response. By imbedding a DFE into the structure of the MLSE, the overall impulse response of the system is truncated to a short duration. With this practical receiver, a compromise may be made between performance and complexity by properly choosing the duration of a desired impulse response. A technique is also developed to estimate the performance of the receiver numerically, taking into account the effect of incorrect decision feedback on the VA. Analysis and computer simulation over a single-pole channel show that the proposed scheme can reduce the complexity of the MLSE while retaining much of its performance advantages.
TL;DR: A theoretical and experimental extension of two-dimensional transform coding and hybrid transform/DPCM coding techniques to the coding of sequences of correlated image frames for Markovian image sources is presented.
Abstract: Two-dimensional transform coding and hybrid transform/DPCM coding techniques have been investigated extensively for image coding. This paper presents a theoretical and experimental extension of these techniques to the coding of sequences of correlated image frames. Two coding methods are analyzed: three-dimensional cosine transform coding, and two-dimensional cosine transform coding within an image frame combined with DPCM coding between frames. Theoretical performance estimates are developed for the coding of Markovian image sources. Simulation results are presented for transmission over error-free and binary symmetric channels.
TL;DR: Modulation and demodulation in the minimum (frequency)-shift keying (MSK) format are reduced to the form of coherent biphase keying, demonstrating the feasibility of synthesizing the one filter that is unique to this signaling scheme.
Abstract: Modulation and demodulation in the minimum (frequency)-shift keying (MSK) format are reduced to the form of coherent biphase keying. Considerable simplification of circuitry is thus effected without sacrifice of performance. When the ratio of the carrier frequency to the bit rate is high, then the technique described here does not require the precise relative phasing of any pair of oscillators in the transmitter. Experimental results demonstrate the feasibility of synthesizing the one filter that is unique to this signaling scheme. In the present instance, the filter is realized as a surface acoustic wave device.
TL;DR: The "Exact" and Monte Carlo calculations are in complete agreement, which allows the Monte Carlo results to be used to calibrate other methods and the relatively simple Chernoff bound is in very good agreement.
Abstract: In this paper four approaches to the calculation of error rates for optical fiber system repeaters are compared ("Exact" calculation, Monte Carlo simulation, Chernoff bounds and the Gaussian approximation). We conclude that the "Exact" and Monte Carlo calculations are in complete agreement. This allows the Monte Carlo results to be used to calibrate other methods. The relatively simple Chernoff bound is in very good agreement with the above, and should be used whenever computational facilities allow. For simpler calculations, or analytical expressions for the effects of parameter variations, the Guassian approximation gives a reasonable good estimate of the receiver sensitivity. However, it tends to underestimate the threshold setting and overestimate the optimal avalanche gain.
TL;DR: In this paper, the authors consider the characteristics of the human visual system as they are related to sensitivity to encoding errors in still achromatic images and present a model based on these experiments for detecting perturbations of an image.
Abstract: This paper considers the characteristics of the human visual system as they are related to sensitivity to encoding errors in still achromatic images. The starting point is a discussion in Section I of the role of a numerical measure of distortion in the determination of optimum encoding. Section II then discusses several ways of determining properties of the human observer and discusses the methodology of psychophysical experiments. Section III then discusses the results of a number of pertinent experiments and presents a model based on these experiments for detecting perturbations of an image. Section IV concludes by discussing how this model can be incorporated into a distortion measure and how this distortion measure might be used. Since the model of the human observer is quite complicated, the mathematical model is not tractable analytically, and results in this last section are as yet fragmentary.
TL;DR: An analysis procedure is developed which explicitly considers the search/lock strategy and the transition from search to lock and a practical example is included to demonstrate the technique.
Abstract: The problem of acquiring and maintaining synchronization of a pseudonoise code, particularly at low signal-to-noise ratios, is analyzed to determine the mean time to acquisition and the mean time to lose lock. An analysis procedure is developed which explicitly considers the search/lock strategy and the transition from search to lock. A practical example is included to demonstrate the technique.
TL;DR: The concepts and techniques of efficient coding for the transmission or storage of two-tone images, such as business documents and weather maps, are reviewed.
Abstract: We review the concepts and techniques of efficient coding for the transmission or storage of two-tone images, such as business documents and weather maps. Digitization considerations are presented first. Then we discuss in detail the basic concepts (both heuristic and mathematical) of efficient coding. This is followed by descriptions of typical coding techniques. Finally, channel errors and buffer requirements are discussed briefly.
TL;DR: The delay performance of a Time Division Multiple Access channel for transmitting data messages is considered and the steady-state probability generating function of the queue size is derived and a formula for the expected message delay is given.
Abstract: The delay performance of a Time Division Multiple Access (TDMA) channel for transmitting data messages is considered. The channel is assumed to be fixed assigned to a station with unlimited buffer capacity and Poisson message arrivals. Each message gives rise to one or more packets for transmission into fixed-length time slots. The steady-state probability generating function of the queue size is derived. A formula for the expected message delay is given. The analysis is then generalized to a nonpreemptive priority queue discipline; expected message delay formulas are given for the priority classes.