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Communications, IEEE Transactions on

Issue 9 • Date September 1985

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Displaying Results 1 - 21 of 21
  • [Front cover and table of contents]

    Publication Year: 1985 , Page(s): 0
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    Freely Available from IEEE
  • [Back cover]

    Publication Year: 1985 , Page(s): 0
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    Freely Available from IEEE
  • Studies on Loss Aging in Submarine Coaxial Cable During Storage

    Publication Year: 1985 , Page(s): 945 - 954
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1000 KB)  

    Attenuation loss change in submarine coaxial cables during 4 years of storage has been measured. Attenuation loss is shown to increase for one year after manufacturing. Then, loss is also shown to increase during summer (May to October) and to stay constant or to decrease during winter (November to April of the next year). This work concentrates on the causes and an estimation method of loss aging. The first part of the paper covers experimental results on the cable aging phenomenon. The second part discusses various factors affecting loss aging, and shows that fretting corrosion on the outer conductor tape will be a main factor. The third part describes an estimation method for and countermeasures to avoid loss aging during cable storage. View full abstract»

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  • Spatial TDMA: A Collision-Free Multihop Channel Access Protocol

    Publication Year: 1985 , Page(s): 934 - 944
    Cited by:  Papers (125)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (960 KB)  

    In this paper we define a broadcast channel access protocol called spatial TDMA, which is designed specifically to operate in a multihop packet radio environment where the location of the nodes of the network is assumed to be fixed. The defined protocol assigns transmission rights to nodes in the network in a local TDMA fashion and is collisionfree. Methods for determining slot allocations are developed, and an approximate solution is given for determining the assignment of capacities for the links of the network that minimizes the average delay of messages in the system. View full abstract»

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  • Motion Compensated Interframe Image Prediction

    Publication Year: 1985 , Page(s): 1011 - 1015
    Cited by:  Papers (69)  |  Patents (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    Interframe motion estimation of subblocks based on improved search techniques is developed. These techniques are based on minimizing the mean difference between the subblock in question in the present frame and the displaced subblock in the previous frame. The performance of the motion compensated prediction developed here is investigated for various block sizes and is compared to other techniques. View full abstract»

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  • New Results on Mean Time-to-First-Slip for a First-Order Loop

    Publication Year: 1985 , Page(s): 897 - 903
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    Approximate results are derived from a new expression for the mean time-to-first-slip for a first-order loop with arbitrary periodic equivalent phase detector characteristic in the presence of frequency detuning. They are accurate for loop signal-to-noise ratios greater than 3 dB or less than 0 dB. The approximations found serve to provide insight into the mean first slip time dependence on the shape of the equivalent phase detector characteristic and the frequency detuning, and dependence on loop parameters. The new expression itself is also of theoretical interest, since it allows one to explicitly express the stationary phase error probability density function and probability current in terms of the mean first slip time. This sheds further light on the interconnections between the conventional modulo-2π approach and the renewal theory approach to the Fokker-Planck method. Extensions to nonperidic equivalent phase detector characteristics are also considered. View full abstract»

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  • Tree-Based Multiaccess Protocols Where Collision Multiplicities Are Known

    Publication Year: 1985 , Page(s): 999 - 1001
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    We compute the stability region and mean packet delay for a class of tree-based, multiaccess protocols proposed recently in the literature for an ALOHA-type channel when collision multiplicities are known, and Show that within the stability region, all the moments of the delay distribution are finite. We also show that the main advantage, of knowing the collision multiplicities is being able, in effect, to detect conflicts in two groups in a single slot. View full abstract»

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  • Analysis of a Priority Polling System for Two-Way Traffic

    Publication Year: 1985 , Page(s): 1001 - 1006
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    Polling systems are a common mechanism for packet transmission in switching systems with distributed control, and computer communication systems, where data and signaling packets must be passed between a set of peripheral device controllers and a central control facility. Presented in this paper is the queueing analysis of the transmission delays for the two-way data traffic between the central control and a set of peripheral controllers, where the communication is based on a complex polling cycle giving effective priority to outgoing packets from the central control. The analysis takes fully into account the mutual dependence between incoming and outgoing packet delays. The delay analysis for the high-priority outgoing packets is exact, and for the lowpriority incoming packets it is approximate. Numerical results are presented to illustrate the analysis method, and are validated against computer simulations. View full abstract»

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  • Weak-Signal DPSK Detection in Narrow-Band Impulsive Noise

    Publication Year: 1985 , Page(s): 1008 - 1011
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The weak-signal receiver for binary differential phase-shift keying (DPSK) in additive noise is derived, and its performance in terms of the error probability in the most general narrow-band impulsive (nonGaussian) noise model, Middleton's class A noise, is analyzed. View full abstract»

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  • Communication Using Pseudonoise Modulation on Electric Power Distribution Circuits

    Publication Year: 1985 , Page(s): 964 - 974
    Cited by:  Papers (42)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1008 KB)  

    Localized communication networks for office automation, security monitoring, environmental management of buildings, computer communications, and other applications enjoy every increasing demand. This paper considers communication of data and analog message signals over electric power distribution circuits for such applications, using pseudonoise (PN) modulation. Advantages of power distribution circuits include reasonably universal coverage and easy access via a standard wall plug. Disadvantages include limited communication bandwidth, relatively high noise levels, and varying levels of impedance, noise, and attenuation. PN (spread-spectrum) signaling provides immunity to narrow-band signal impairments and casual eavesdropping, multiplexing capability, addressing capability, and easily implemented error rate versus data rate tradeoffs. The primary disadvantage is synchronization delay and hardware cost normally associated with PN code synchronization at the receiver. Our prototype modem avoids these difficulties by using the 60 Hz power line frequency for carrier, code, and data-bit synchronization. Design issues discussed include processing gain optimization, modem impedance specification, carrier frequency selection, and PN code selection. Prototype modem circuitry costing less than $30.00 is described. Measurements on actual power distribution circuits indicate a bit-error probability p = 10^{-4} or less at data rate R_{B} = 6 kbits/s for single users or at R_{B} = 60 bits/s for M \simeq 22 simultaneous users. Performance calculations for analog message signals are included. View full abstract»

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  • Stack Algorithm Speech Encoding with Fixed and Variable Symbol Release Rules

    Publication Year: 1985 , Page(s): 1015 - 1018
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    Tree codes find wide use in a variety of problems such as source encoding, sequential decoding, pattern recognition, and related fields. Efficient algorithms exist to explore the code trees and are well documented in the literature. All of these algorithms search code trees in an incremental manner, releasing a path map symbol at a time. A recent work has investigated the effect of releasing multiple symbols on the performance of the (M, L) algorithm used with speech. Here we investigate the effect of multiple symbol release rules on the performance of the stack algorithm in the context of speech encoding. We show that significant computational reduction can result with the use of such rules. We use an efficient data structure, the AVL tree data structure, to store code tree paths. View full abstract»

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  • The N-Phase Digital Tanlock Loop for Tracking Suppressed-Carrier N-ary PSK Signals

    Publication Year: 1985 , Page(s): 904 - 910
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    In this paper, the performance of an N -phase digital tanlock loop (DTL) in the presence of phase error disturbance is studied. The N phase DTL is a digital loop for tracking suppressed-carrier N -ary phaseshift keyed (PSK) signals. It has linear phase characteristics in the modulo- 2\pi/N sense as a result of using the \tan^{-1}[.] function in the phase error detector. We first obtain the probability density function of phase error of the phase detector output and verify it by computer simulation. Then, we consider the optimum bandwidths of the bandpass filters in the loop that yield the minimum variance of the phase error. Also, the finite word length effect on the performance of the N -phase DTL is investigated by computer simulation. In addition, the performance of the N -phase DTL is compared to that of the digital N -phase I-Q loop which has sinusoidal phase characteristics. It has been found that the first-order Nphase DTL has wider lock range than the first-order N -phase I-Q loop in the absence of noise. View full abstract»

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  • An Analysis of the Sensitivity of Digital Modulation Techniques to Frequency-Selective Fading

    Publication Year: 1985 , Page(s): 986 - 992
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB)  

    This Paper investigates the sensitivity to frequency-selective fading of different modulation techniques commonly used in digital radio systems. The modulation methods considered are phase-shift-keying ( M ary PSK), nonoffset and offset quadrature amplitude modulation ( M -ary QAM), and quadrature partial response signaling (QPRS). The performances of these methods during multipath fading are compared on the basis of the "signatures" calculated for idealized systems. Results are presented from which the relative outage probability was determined, assuming a propagation channel with frequency-selective Rician fading. View full abstract»

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  • Virtual Time CSMA: Why Two Clocks Are Better than One

    Publication Year: 1985 , Page(s): 919 - 933
    Cited by:  Papers (38)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1704 KB)  

    A new carrier sense multiple access (CSMA) algorithm, called virtual time CSMA, is described and analyzed. This algorithm uses a novel approach to granting access to the shared broadcast channel based on variable-rate clocks. Unlike other CSMA algorithms, the operation of virtual time CSMA reduces to the ideal case in the zero propagation time limit: a work-conserving, first-come first-served M/G/1 queueing system. The algorithm does not appear to be difficult to implement, but offers better throughput-delay performance than existing CSMA algorithms. A simple closed form technique for estimating the mean message delay is presented. This technique is of independent interest because of its applicability to certain "sliding window" tree conflict resolution algorithms. Extensive numerical results for the algorithm are presented, including comparisons with simulation and with other CSMA algorithms. View full abstract»

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  • Design of Smearing Filters for Data Transmission Systems

    Publication Year: 1985 , Page(s): 955 - 963
    Cited by:  Papers (9)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    In this paper, we introduce a new approach to design smearing and desmearing filters for data transmission systems to suppress pulse-like disturbances inserted in the communication channel. Our method is based on time domain considerations. It consists of the optimization of two merit factors defined for the impulse response functions of the filters. The first one is a measure of the smearing efficiency, and the second one is a measure of the amount of intersymbol interference caused by the insertion of the two filters in the transmission system. Our method will be applied to smearing and desmearing filters for baseband signals as well as for passband signals. In particular, we show that our method leads to filters having a better smearing efficiency and a simpler implementation than the filters obtained by the classical frequency domain approach. View full abstract»

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  • A Postfiltered DPCM Scheme

    Publication Year: 1985 , Page(s): 1019 - 1021
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    Quantization noise constitutes the limiting factor on DPCM performance. For a low number of levels in the quantizer, this noise is also correlated. In this correspondence we present a technique for improving the performance of the DPCM system at a very modest cost. The technique involves the use of an adaptive transversal filter at the receiver output to reduce the effects of quantization noise. The filter is trained at the transmitter and periodic updates sent to the receiver. View full abstract»

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  • On the Probability Density Function of the Squared Envelope of a Sum of Random Phase Vectors

    Publication Year: 1985 , Page(s): 993 - 996
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    A recursive solution is presented for the probability density function of the sum of N independent, random phase vectors. The recursion parameter is N , the number of vectors in the sum. This approach allows one to rapidly compute a complete set of these density functions for values of N = 2, 3, ..., N_{\max } , where Nmaxtypically corresponds to the total number of system users in a multiuser FHMA/MFSK application, or one plus the total number of jamming tones in an FH/MFSK spread-spectrum application. Such evaluations are necessary for exact calculation of the average error probability performance of such systems. View full abstract»

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  • Digitally Phase Modulated (DPM) Signals

    Publication Year: 1985 , Page(s): 911 - 918
    Cited by:  Papers (15)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB)  

    Some properties of digitally phase modulated (DPM) signals are presented. Phase modulation with (overlapping) pulses generated by a digital FIR filter belong to this class, which may be considered to be a practical approximation to continuous phase modulated (CPM) signals. The power spectra of DPM signals are derived analytically. The ability of these signals to operate through an additive white Gaussian noise channel is assessed by calculating their minimum Euclidean distance. Their noise and spectral properties are found to be similar to those of CPM signals. Assuming that a Viterbi decoder is used to resolve symbol interference, the out-of-band power tends to decrease as the pulse duration increases, and the noise immunity is enhanced. At the same time the receiver complexity grows exponentially. Hence, noise immunity and spectrum compactness are achieved at the cost of higher received complexity. Modems for DPM signals are believed to be easier to implement than those for CPM signals. This is because filter design is simple and a residual carrier component can be retained to facilitate carrier regeneration. Furthermore, the accumulated carrier phase does not need to be continuously evaluated in order to perform matched filtering. The analytic results derived are supported by measurements and simulations. View full abstract»

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  • A Simple, Approximate Method of Generating Baseband-Serial MSK

    Publication Year: 1985 , Page(s): 1006 - 1008
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    An alternate derivation of the serial formulation of the MSK signal leads to an approximate implementation that is based on filtering an easily generated three-level data signal through a high- Q , two-pole filter whose low-pass and bandpass outputs are modulated onto quadrature carriers. View full abstract»

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  • On the Availability of Multilevel CPFSK Systems with Modulation Pulse Shaping During Multipath Propagation

    Publication Year: 1985 , Page(s): 975 - 985
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1072 KB)  

    The behavior of CPFSK systems with modulation pulse shaping and limiter-discriminator detection is tested in the prsence of multipath fading. With the aim of determining the eye-closure domain, a theoretical analysis is presented for a generic number of modulation levels. It is shown that, by suitably varying the maximum angular frequency deviation ωd, control of outage probability Poutis possible. Moreover, the choice of duty-cycle in the modulation pulse \tau /T < 1 leads to a lower value of Poutwith respect to the conventional case \tau /T = 1 , if we fix, as happens in practice, an upper bound in the transmitted power. This promising characteristic deeply differentiates the CPFSK from the PSK, DCPSK, and QAM systems: CPFSK systems, with a fixed number of modulation levels, allow us to obtain decreasing values of Poutat the cost of increasing transmission power by suitably varying the set of signal parameters, even in the absence of diversity techniques and/or adaptive equalization. View full abstract»

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  • A Comparison of Some Error Detecting CRC Code Standards

    Publication Year: 1985 , Page(s): 996 - 998
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    Many data communication systems make use of cyclic redundancy check (CRC) codes for error detection purposes. In this paper, an asymptotic result concerning the undetected error probability P(\epsilon) of CRC codes is derived. The P(\epsilon) 's of a number of CRC codes which have been adopted as international standards are also examined. 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.

 

 

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Editor-in-Chief
Robert Schober
University of British Columbia