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Communications, IEEE Transactions on

Issue 2 • Date February 1982

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  • [Front cover and table of contents]

    Publication Year: 1982 , Page(s): 0
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    Freely Available from IEEE
  • Comment on "Tracking Performance of the Filter and Square Bit Synchronizer"

    Publication Year: 1982 , Page(s): 407 - 410
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (327 KB)  

    The method for evaluating the tracking performance in the above paper obliterates the contribution to the mean square error which is due to the cyclostationarity of the disturbances. Beside this, the pattern-dependent jitter has not been considered in the paper. Our results include the effect of cyclostationarity and the pattern-dependent jitter. View full abstract»

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  • [Back cover]

    Publication Year: 1982 , Page(s): 0
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    Freely Available from IEEE
  • A Measurement of the MARISAT L-Band Signals at Low Elevation Angles Onboard Mobil Aero

    Publication Year: 1982 , Page(s): 359 - 365
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    The MARISAT-to-ship L -band signals used in maritime mobile satellite communications service are degraded by fading and scintillation at low elevation angles. These degradations are attributed to multipath effects arising from ionospheric, tropospheric, and/or sea surface diffractions. To characterize such degradations, measurements were made at the Southbury earth station and onboard the S.S. Mobil Aero while the ship was en route from Norfolk, VA, to Texas City, TX. Measurements include monitoring the carrier-to-noise ratio ( C/N ) of time-division multiplex/time-division multiple access (TDM/TDMA) voice carriers and measuring the bit error rate (BER) of 2400/1200 bit/s digital data transmissions through a voice channel. Results indicated that both C/N and BER are severely degraded at elevation angles below 5° due to propagation anomalies. Information useful for design considerations of future maritime communications systems is summarized. View full abstract»

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  • The Limit-Switched Loop: A Phase-Locked Loop for Burst Mode Operation

    Publication Year: 1982 , Page(s): 396 - 407
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (928 KB)  

    In a time-division or burst mode communications systems, synchronization must be achieved within a short preamble time at the beginning of each burst. When used in such a system, a conventional phase-locked loop (PLL) occasionally exhibits a prolonged phase acquisition transient. This effect, known as hangup, occurs at a large value of phase error and may cause loss of a data burst. The present paper investigates a modification of a PLL known as a limit-switched loop (LSL). The LSL offers faster phase acquisition and better hangup immunity than a PLL. The LSL estimates its position in the phase plane at the beginning of acquisition and, if hangup is about to occur, makes a phase correction so as to forestall its occurrence. The structure and properties of the LSL are investigated in this paper. View full abstract»

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  • Minimizing Packet Waiting Time in a Multibeam Satellite System

    Publication Year: 1982 , Page(s): 305 - 316
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1048 KB)  

    In this paper, we examine the problem of time-slot assignment in an SS/TDMA system operating in a packet-switched environment. We seek to assign time slots in order to minimize average packet waiting time and in order to maximize transponder utilization. We show that an assignment which achieves both objectives exists and develop a branch-and-bound algorithm to find it. In addition, we suggest several heuristics which require much less computational effort and give very close to optimal results. We derive theoretical bounds on the performance of these heuristics and perform simulation trials to show that, on average, the heuristics are very much better than their bounds suggest, and are, in fact, extremely close to optimal. View full abstract»

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  • Power Spectrum of Angle Modulated Correlated Digital Signals

    Publication Year: 1982 , Page(s): 389 - 396
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (792 KB)  

    The paper deals with the spectral analysis of both phase and frequency modulated digital signals with correlated messages, where correlation is obtained by encoding. Also, a possible general filtering of the baseband digital signal is taken into account. The method of computation is fast, since the computational complexity increases linearly with the baseband pulse duration. The main result is concerned with frequency modulation. It is shown that for some well-known baseband encoding schemes, such as bipolar, pair selected ternary, high density bipolar, and bipolar with n zeros substitution, the spectrum exhibits lines no matter what the value of the modulation index. View full abstract»

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  • On the Impact of HDLC Zero Insertion and Deletion on Link Utilization and Reliability

    Publication Year: 1982 , Page(s): 375 - 381
    Cited by:  Papers (3)  |  Patents (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    In HDLC, a zero is inserted after every five consecutive "ones" in order to resolve ambiguity about the location of delimiters. In this paper, we generalize the number "five" as an arbitrary positive integer n and study the impacts of n on the link utilization for a noiseless channel and on the reliability for a noisy channel. The entropy of the sequence after this generalized zero insertion is found for a noiseless channel. An expression for the optimal n that maximizes a quantity called the delimiter efficiency is also found in terms of the frame size. It is shown that n = 5 achieves a delimiter efficiency close (within 2 percent) to that achievable by the optimal n . For a noisy channel, the reliability of HDLC is derived. It is shown that the probability of an undetectable error in HDLC is dominated by the errors that propagate through a created flag or incorrect zero deletion, and is in the neighborhood of 10-7for typical parameters. Increasing n by 8 is shown to improve the reliability by two orders of magnitude. It is proposed to use a two byte flag and a four byte frame check sequence to improve the reliability by seven orders of magnitude. View full abstract»

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  • Maximum Power Transmission in Mass-Limited Radio Systems

    Publication Year: 1982 , Page(s): 414 - 417
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    A simple fundamental relationship is derived between antenna gain and transmitter power which maximizes the effective radiated power in mass-limited satellite systems. In the most common case, maximum effective radiated power is achieved when the payload mass is divided equally between the antenna system and the power system. Although this may have been known intuitively to satellite designers, to the author's knowledge this relationship has never been published. Example calculations show that considerable increases in performance can be expected for satellites which employ high-gain multibeam antennas. View full abstract»

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  • Detection of Coherent Optical Signals in Generalized Gaussian Noise

    Publication Year: 1982 , Page(s): 367 - 372
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    Results of receiver performance for the detection of a coherent light signal in the presence of background radiation are obtained and compared for two different types of background noise: a Gaussian field and a Gaussian field whose complex analytic signal is not circularly symmetric. It is pointed out that the randomness in the noise radiation does not significantly diminish the probability of correct detection. View full abstract»

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  • A Study of Fairness in Packet-Switching Networks

    Publication Year: 1982 , Page(s): 346 - 353
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    The use of channel scheduling to improve a measure of fairness in packet-switching networks is investigated. This fairness measure is based on mean end-to-end delays derived from Kleinrock's classical model. The network designer can incorporate any desired relative delay among user classes into this fairness measure. It is found that scheduling is helpful in reallocating delay among user classes and can be used to improve the fairness of a network. It is also shown that a parameterized queueing discipline can be used to further improve fairness. A conservation theorem characterizing the effects of scheduling on overall mean end-to-end delay is established. The results are applicable to both fixed and random routing and are found to be relatively insensitive to fluctuations in traffic. View full abstract»

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  • Carrier Reference Error Sensitivity of a Viterbi Detector for PAM Data Transmission

    Publication Year: 1982 , Page(s): 410 - 414
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    In this paper we extend the probability of error analysis for Viterbi detectors for PAM data transmission to include the effects of steady-state carrier reference errors. It has earlier been found that the Viterbi detector is sensitive to the effects of constant carrier phase errors. However, for two reasonably complicated voiceband pulses taken from the literature, we find that the Viterbi detector is no more sensitive to random carrier phase errors than is a standard quantizing detector. View full abstract»

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  • FM Nonlinearity Due to Harmonic Distortion in the Carrier Path

    Publication Year: 1982 , Page(s): 365 - 367
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    The intermodulation noise in FM transmission caused by harmonic distortion in the carrier path is calculated by deriving the second- and third-order terms of the distorted signal. Explicit relations are given in terms of filter delays, harmonic levels, and modulation transfer parameters. View full abstract»

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  • Further Clarification on the Use of Bessel Function Expansion to Approximate TWTA Nonlinear Characteristics

    Publication Year: 1982 , Page(s): 418 - 419
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    The Bessel function expansion has been used [1] to approximate the TWTA nonlinear characteristics to assist in the evaluation of intelligible crosstalk between FDM/FM carriers using the Shimbo-Pontano method [2]. In particular, the arbitrary constant α was chosen to be in the range of 100-1000. This correspondence presents a further theoretical clarification on the selection of suitable values for α, which was briefly explained in [3]. In this analysis, it is shown that the suitably chosen values for α (as given in the main text) cannot be large (roughly, \alpha \leq 1.6 ). View full abstract»

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  • An Adaptive Capacity Allocation Scheme in Telephone Networks

    Publication Year: 1982 , Page(s): 354 - 359
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    This paper discusses adaptive capacity allocation for high-usage groups (direct routes) in telephone networks so as to best maintain performance for each hour's traffic load. We present two algorithms for this adaptive allocation scheme. The first, called a capacity allocation algorithm, determines capacity allocation in a manner that minimizes the maximum value of point-to-point blocking probabilities for each hour's traffic load. The second, called a frame assignment algorithm, determines the channel connection pattern with a minimum of changes from the old pattern, for a new capacity allocation. View full abstract»

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  • On the Probability of Undetected Error for Linear Block Codes

    Publication Year: 1982 , Page(s): 317 - 325
    Cited by:  Papers (58)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    The problem of computing the probability of undetected error is considered for linear block codes used for error detection. The recent literature is first reviewed and several results are extended. It is pointed out that an exact calculation can be based on either the weight distribution of a code or its dual. Using the dual code formulation, the probability of undetected error for the ensemble of all nonbinary linear block codes is derived as well as a theorem that shows why the probability of undetected error may not be a monotonic function of channel error rate for some poor codes. Several bounds on the undetected error probability are then presented. We conclude with detailed examples of binary and nonbinary codes for which exact results can be obtained. An efficient technique for measuring an unknown weight distribution is suggested and exact results are compared with experimental results. View full abstract»

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  • Artificial Signals and Identification Methods to Evaluate the Quality of Speech Coders

    Publication Year: 1982 , Page(s): 325 - 335
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1088 KB)  

    Objective quality measures provide an economic and practical alternative to tedious and expensive subjective tests. Furthermore, some recently proposed measures predict quality values which correlate quite well with the subjective ones. The objective measures are particularly useful to test the influence of design parameters during the laboratory development of codec algorithms. In this paper the architecture of a measuring equipment to conduct objective quality measures on speech waveform coders is presented and discussed. Only the input and output signals from the coder are needed and an identification algorithm is used to separate the distortion effects introduced by the coder from other effects such as gains, time shifts, low-pass filtering, and so on. The choice of the most appropriate kind of signal for the identification and measurement steps is a problem also investigated. Particularly, results concerning mathematically defined speech-like signals are reported. The performance of the method is investigated under different conditions and the correlations with subjectively determined results are also reported for a number of ADPCM coders with widely varying parameters. View full abstract»

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  • Digital Voice Storage in a Microprocessor

    Publication Year: 1982 , Page(s): 336 - 345
    Cited by:  Papers (5)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1184 KB)  

    We describe digital encoding and automatic silenceediting techniques for PCM and ADPCM voice storage in the MC68000 microprocessor. We give program details for encoding, silence elimination, storage of active speech bursts and reconstitution of the signal upon read-back. Coding rates in the range 64 down to 16 kbits/s are implemented. We find that silent intervals corresponding, typically, to 20-40 percent of the duration of continuous input speech can be usefully eliminated. Available storage is thereby used more efficiently. The eliminated intervals are automatically reinserted upon read-back. We further demonstrate automatic scaling of the silent intervals in the reconstituted output. We confirm that a variation of ± 50 percent in the reinserted silent intervals is typically acceptable. This latitude can significantly alleviate buffer requirements in a packet transmission system for voice. View full abstract»

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  • Vector Quantizers and Predictive Quantizers for Gauss-Markov Sources

    Publication Year: 1982 , Page(s): 381 - 389
    Cited by:  Papers (65)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    Low-rate vector quantizers are designed and simulated for highly correlated Gauss-Markov sources and the resulting performance is compared with Arnstein's optimized predictive quantizer and with Huang and Schultheiss' optimized transform coder. Two implementations of vector quantizers are considered: full search vector quantizers-which are optimal but require large codebook searches-and tree searched vector quantizers-which are suboptimal but require far less searching. The various systems are compared on the basis of performance, complexity, and generality of design techniques. View full abstract»

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  • A New Approach to the Design of a Phase Modulator with Low Nonlinear Distortion

    Publication Year: 1982 , Page(s): 372 - 375
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    Phase modulation can most directly be effected by a device whose output is a sinusoidal function of its input. In this paper a phase modulator is described in which a linear segmental approximation of the sinusoidal function is used. Performance results in terms of a phase difference from perfect linearity ( \Delta \Phi ) and signal-to-distortion ratio (SDR) are given. For eight-segment approximation \Delta \Phi is 0.06° and SDR is 62.3 dB in the range \pm90\deg . 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