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Communications, IEEE Transactions on

Issue 2 • Date February 1980

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Displaying Results 1 - 25 of 28
  • [Front cover and table of contents]

    Publication Year: 1980 , Page(s): 0
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    Freely Available from IEEE
  • Comments on "The vector space formulation of the rain crosspolarization problem and its compensation"

    Publication Year: 1980 , Page(s): 311 - 312
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    In the above paper (ibid., vol. COM-27, pp. 502-509, Feb. 1979) L.S. Lee proposes a method to compensate for the rain-induced cross polarization in a dual-polarization zation link. This method is based on a model of Chu, in which the effect of rain on two orthogonal linear polarizations, along unit vectors is represented by a given matrix. The idea is that the medium is characterized by two orthogonal axes which are, the eigenvectorsof the matrix. If these vectors are used as a new basis, the matrix takes the diagonal form. The compensation is obtained by rotating the emitted linear polarizations of an angle, which is necessary to align them with the eigenvectors. The Lee claims that a similar compensation is applicable to the case of circular polarizations. It is here shown that the two signals are linearly polarized along the principal axes given by the eigenvectors. This means that the antenna does not radiate circular polarizations in space, but linear ones as a result of the addition in each channel of two equal and opposite circularly polarized signals. The proposed compensation actually is an elegant method to perform the rotation of the linear polarizations by first transforming them to circular polarizations, then introducing a phase shift, and finally converting them back to linear polarizations. View full abstract»

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  • Author's Reply

    Publication Year: 1980 , Page(s): 312
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    It is noted that the commentor has made a new interesting interpretation of the mathematical formulation in the paper, which is different from the original idea presented in it. In the original work the two "signals" are first passed through the network, which forms their sum and difference and introduces phase shift, before entering the antenna feed and being radiated in form of "polarized waves." The antenna does radiate two opposite-sensed circular polarizations but the two radiated circular polarizations, in fact, form two orthogonal linear polarizations in the free space with amplitudes proportional to the circular polarization amplitudes and directions aligned with the eigenvectors. View full abstract»

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  • [Back cover]

    Publication Year: 1980 , Page(s): 0
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    Freely Available from IEEE
  • Packet Radio Performance Over Slow Rayleigh Fading Channels

    Publication Year: 1980 , Page(s): 279 - 286
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    Expressions for the throughput and average packet delay for a Pure-ALOHA single-hop packet radio system operating in slow Rayleigh fading are derived. For noncoherent frequency-shift-keying (NCFSK), an exact closed form expression is presented. For coherent phase-shift-keying (CPSK) an excellent approximation for large packet sizes is derived. This approximation technique is valid in general for other modulation schemes and for other fading channel statistical characterizations. The packet length which maximizes the useful data throughput in slow Rayleigh fading is found. The results of this investigation indicate that a packet radio system can be designed with a modest link margin for fading and achieve identical throughput performance over a nonfading channel and a fading channel with only a small increase in average packet delay for the fading channel. View full abstract»

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  • Dynamic Flow Control in Store-and-Forward Computer Networks

    Publication Year: 1980 , Page(s): 263 - 271
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (976 KB)  

    In a recent paper we presented an analysis of flow control in store-and-forward computer communication networks using a token mechanism. The analysis assumed equilibrium conditions for a selected set of system parameters which were not dynamically adjusted to stochastic fluctuations in the system load; this mechanism was referred to as "static flow control." In this paper we study a "dynamic flow control" in which parameters of the system are dynamically adjusted to match the availability of resources in the network. Based on Markov decision theory, an optimal policy to dynamically select the number of tokens is formulated. Because an exact solution to the problem is extremely difficult, an effective heuristic solution to the problem is presented. Numerical results are given and it is shown that the throughput-delay performance of a network is better with dynamic control than with static control. View full abstract»

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  • A Fast Computational Algorithm for the Discrete Sine Transform

    Publication Year: 1980 , Page(s): 304 - 307
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    A sparse-matrix factorization is developed for the discrete sine transform (DST). This factorization has a recursive structure and leads directly to an efficient algorithm for implementing the DST, a feature most desirable and very similar ot that of the DCT. This algorithm requires fewer arithmetic operations compared to that for the discrete cosine transform (DCT). View full abstract»

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  • Filters for the Detection of Binary Signaling: Optimization Using the Chernoff Bound

    Publication Year: 1980 , Page(s): 257 - 259
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The probability of error in the detection of binary signaling by a linear receiver is upper bounded by the Chernoff bound, and a general relationship is obtained whose solution gives a receiver filter and threshold which minimize this bound. As an example, the detection of Poisson signaling in the presence of additive white-Gaussian noise is considered and the resulting filter lies between the optimum filter for Poisson signaling and a matched filter. View full abstract»

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  • Batch Throughput Efficiency of ADCCP/HDLC/SDLC Selective Reject Protocols

    Publication Year: 1980 , Page(s): 187 - 195
    Cited by:  Papers (18)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    The batch throughput efficiency is studied for three variants on selective reject protocols that operate in a full duplex asynchronous response mode and that adhere to the common architectural features of ADCCP, HDLC, and SDLC. In these architectures, the receiver of information frames may use the REJ supervisory frame to request the sender of information frames to back up to an earlier point in the send sequence. Alternatively, the receiver of information frames may issue the SREJ supervisory frame, which requests resending of a single previous information frame followed by continuation of the ongoing send sequence. The first protocol discussed here uses SREJ as the principle method for recovering lost frames but reverts to REJ recovery if certain combinations of errors occur. The second protocol uses SREJ as the only means for recovery. The third protocol uses SREJ for "isolated" frame losses; if a second frame loss occurs within a specified time after the first, then recovery of the first loss is done by REJ. Results plotted for transmission via satellite at 1.544 Mbits/s show that the selective reject protocols permitted by the current versions of ADCCP, HDLC, and SDLC outperform the simpler REJ protocol only for bit error rates in a narrow range. Thus, it may be worthwhile to consider modifications to these architectures that will permit more flexible selective reject protocols. View full abstract»

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  • Commutativity and Application of Digital Interpolation Filters and Modulators

    Publication Year: 1980 , Page(s): 244 - 249
    Cited by:  Papers (1)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    Interpolation filters are being widely used in a variety of communication applications. An equivalent realization of an interpolation FIR filter is shown to be a cascade combination of a hold and a periodically varying filter. It is also shown that the periodicity of the filter results in the Commutativity of the filter and a sinusoidal modulator. An application of such a scheme to TDM-FDM transmultiplexer is also presented. View full abstract»

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  • Optimal Segmented Compression Characteristic for Speech

    Publication Year: 1980 , Page(s): 301 - 302
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    The minimax optimization criterion for the segmented compression characteristic is formulated. For speech signal, the optimal seven segment compression characteristic is given. View full abstract»

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  • On Soft-Decision Demodulation for PCM- and DPCM- Encoded Speech

    Publication Year: 1980 , Page(s): 308 - 311
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    In a simulation of soft decision demodulation-interpolation for digital speech transmission, it has been noted that signal-to-noise ratio gains due to the technique are greater with nonadaptive and periodically adaptive quantizers than with instantaneously adaptive quantizers; further, the gains are greater with PCM than with differential PCM. Our results for nonadaptive PCM reinforce those in a recent analytical paper by Sundberg [1]. View full abstract»

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  • Analysis of a Two-Hop Centralized Packet Radio Network--Part II: Carrier Sense Multiple Access

    Publication Year: 1980 , Page(s): 208 - 216
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    We continue in this paper our study of two-hop centralized packet radio networks in view of understanding the behavior of these systems. Traffic originates at terminals, is destined to a central station, and requires for its transport the relaying of packets by store-and-forward repeaters. We consider here that all devices employ the nonpersistent carrier sense multiple-access mode. System capacity and through-put-delay tradeoffs are derived and compared to those obtained for slotted ALOHA in Part I [l]. View full abstract»

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  • Static Flow Control in Store-And-Forward Computer Networks

    Publication Year: 1980 , Page(s): 271 - 279
    Cited by:  Papers (39)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (944 KB)  

    In this paper we develop an analytic model for end-to-end communication protocols and study the window mechanism for flow control in store-and-forward (in particular message-switching) computerbased communication networks. We develop a static flow control model in which the parameters of the system are not dynamically adjusted to the stochastic fluctuation of the system load. Numerical results are presented and it is shown that the throughput-delay performance of a network can be improved by proper selection of the design parameters, such as the window size, the timeout period, etc. View full abstract»

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  • Nonlinearity and Its Compensation of Semiconductor Laser Diodes for Analog Intensity Modulation Systems

    Publication Year: 1980 , Page(s): 297 - 300
    Cited by:  Papers (8)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Experimental investigation was carried out on nonlinear video distortions of differential gain and differential phase in various optical transmitters using laser diode structures having a single transverse mode operation. It was observed that the measured nonlinearity of laser diodes was comparable to that of a typical LED. A simple linearizing technique for improving the nonlinearity, using an emphasis principle, is proposed and was experimentally examined, yielding promising results. View full abstract»

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  • Spectral Characteristics of Convolutionally Coded Digital Signals

    Publication Year: 1980 , Page(s): 173 - 186
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1272 KB)  

    The power spectral density of the output symbol sequence of a convolutional encoder is computed for two different input symbol stream source models, namely, an NRZ signaling format and a first-order Markov source. In the former, the two signaling states of the binary waveform are not necessarily assumed to occur with equal probability. The effects of alternate symbol inversion on this spectrum are also considered. The mathematical results are illustrated with many examples corresponding to optimal performance codes. It is demonstrated that only for the case of a purely random input source (e.g., NRZ data with equiprobable symbols) and a particular class of codes is the output spectrum identical to the input spectrum except for a frequency scaling (expansion) by the reciprocal of the code rate. In all other cases, the output spectrum is sufficiently changed relative to the input spectrum that the commonly quoted statement "a convolutional encoder produces a bandwidth expansion by a factor equal to the reciprocal of the code rate" must be exercised with care. View full abstract»

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  • New Code Acquisition Techniques in Spread-Spectrum Communication

    Publication Year: 1980 , Page(s): 249 - 257
    Cited by:  Papers (11)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    New techniques for acquiring the codes used in frequency hopping (FH), hybrid frequency hopping/time hopping (FH/TH), and frequency hopping/direct sequence (FH/DS) spread-spectrum systems are presented. Autoregressive spectral estimation is employed to recover the FH code, quadrature processing is used for the DS code, while the TH gating code is recovered by a simple threshold test used in conjunction with the adaptive filter used for the spectral estimation. A wide margin of spectral estimation errors can be tolerated since an acquisition logic is used to estimate the FH code phase. The proposed techniques require acquisition times only of the order of the shift-register generator lengths, whereas other schemes of serial and parallel search require acquisition times of the order of the code lengths. Detailed simulation results will identify the working carrier-to-noise ratio (CNR) range for the different techniques presented as well as the various thresholds involved. View full abstract»

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  • Discrete-Time Queueing Systems and Their Networks

    Publication Year: 1980 , Page(s): 260 - 263
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    Queueing systems in descrete time that can model certain computer communication systems are considered. First, a single-resource model consisting of a geometric server with feedback facility, to which packets arrive in independent bulks, is analyzed. Then, it is shown that a network of such geometric resources with packets arriving in independent Bernoulli streams (which, in a sense, is a discrete analog of Jackson's network) does not possess the independence property. A byproduct of this result is the fact that output of a geometric resource fed by two or more independent Bernoulli streams is not an independent Bernoulli stream. View full abstract»

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  • Error Probability and Bandwidth of Digital Modulation

    Publication Year: 1980 , Page(s): 287 - 290
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    The bandwidth in which 99 percent of the power is contained is presented for ASK, QASK, OQASK, PSK, FSK, and MSK. An example is given in which the bandwidth of FSK is one eighth the bandwidth of ASK and of the modulating signal. Error probability is presented for the various types of modulation with various detectors, detector filters and Butterworth receiver filters of order N = 4 or \infty . Comparisons are made between the performance and bandwidth efficiency of the various systems. View full abstract»

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  • Error Event Statistics for Convolutional Codes

    Publication Year: 1980 , Page(s): 302 - 304
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    Viterbi (1971) introduced a structure generating function T(D,N,L) for convolutional codes and used it to bound the probability of a decoding error P(\bar{e}) . Viterbi's result is used to approximate the probability function P(l, \bar{e}) on error events of length l . Using P(l,\bar{e}) , approximate values are found for the error event statistics E {D} , the expected number of symbol errors in an error event; E{N} , the expected number of branch errors in an error event; and E{L} , the expected length (in branches) of an error event. The statistics are technically approximate, but are practically upper bounds, loose at high channel error rates, and tightening as the channel error rate drops. The per-unit-length statistics E{N | l} and E {D | l} appear to be of use in finding good codes. View full abstract»

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  • K-Band Mobile Earth Station for Domestic Satellite Communications System

    Publication Year: 1980 , Page(s): 291 - 294
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    Design considerations of a K -band (30/20 GHz) mobile earth station for a domestic satellite communications system are described. A Japanese Medium Capacity Communication Satellite which utilizes K and C satellite communication bands was considered for the system design. Transmitting power control method, statistical link quality estimation, and equipment description are given. View full abstract»

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  • Laser Mode Partition Noise Evaluation for Optical Fiber Transmission

    Publication Year: 1980 , Page(s): 238 - 243
    Cited by:  Papers (62)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    An evaluation of the influence of mode partition noise on error rate performance in a high bit rate optical fiber transmission system is presented. First, it is experimentally clarified that the intensity in each longitudinal mode of a laser diode fluctuates, although the intensity for the total mode is constant. It is also established that this fluctuation causes degradation of the error rate performance after transmission through a long optical fiber. The fluctuation is named "mode partition noise." Next a simple model for the fluctuation is proposed. The characteristics of the fluctuation are discussed on the basis of this model. Optical waveform fluctuation is found to be introduced by mode partition noise in the course of transmission through a long despersive transmission medium. This optical waveform fluctuation and its frequency spectrum are calculated. Finally, the error rate performance is evaluated and specifications required for a laser spectrum to attain a given repeater spacing are clarified. View full abstract»

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  • Recursive Algorithms for Computing End-to-End Blocking in a Network with Arbitrary Routing Plan

    Publication Year: 1980 , Page(s): 153 - 164
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1008 KB)  

    This paper presents three recursive algorithms for computing end-to-end blocking probabilities in a network with alternate routing, based on link blocking probabilities. The only assumption made is the statistical independence of link blocking probabilities. The first algorithm applies to arbitrary routing plans. The second algorithm applies to single-loss-route routing plans which include predictive routing plans used in advanced private networks. The second algorithm is also applicable to solving the terminal-pair reliability problem. The third algorithm applies to tandem-node-matrix-generated routing plans which include hierarchical routing plans similar to those used in North American public toll network, AT&T's CCSA, EPSCS, and ETN networks. These three algorithms are progressively more efficient. View full abstract»

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  • Multilevel Signaling over Step-Index Fibers

    Publication Year: 1980 , Page(s): 294 - 297
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    This paper investigates the effects of a multilevel signal applied in an optical communication system with a step-index fiber. The model for description of the fiber impulse response used here is more accurate than previously used models, which influenced conclusions significantly. It is found that multilevel signals can improve performances of a digital optical system when intersymbol interference is significant. View full abstract»

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  • Analysis of a Two-Hop Centralized Packet Radio Network--Part I: Slotted ALOHA

    Publication Year: 1980 , Page(s): 196 - 207
    Cited by:  Papers (41)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1008 KB)  

    The design of packet radio systems involves a large number of design variables that interact in a very complex fashion. As this design problem in its general form is quite complex, a viable approach is to analyze some simple but typical configurations in an attempt to understand the behavior of these systems. In this paper, a two-hop centralized configuration is considered in which traffic originates at terminals, is destined to a central station, and requires for its transport the relaying of packets by store-and-forward repeaters. The through-put-delay performance is derived, and its dependence on such key system variables as the network topology, the transmission protocol, and the repeaters' storage capacities, is given. In this part, devices are assumed to be utilizing the slotted ALOHA access mode. Carrier sense multiple access is treated in Part II of this series [1]. View full abstract»

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Aims & Scope

IEEE Transactions on Communications focuses on all telecommunications including telephone, telegraphy, facsimile, and point-to-point television by electromagnetic propagation.

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia