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Communications, IEEE Transactions on

Issue 4 • Date April 1983

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

    Publication Year: 1983 , Page(s): 0
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    Freely Available from IEEE
  • [Back cover]

    Publication Year: 1983 , Page(s): 0
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    Freely Available from IEEE
  • The Performance of FSK in Frequency-Selective Rayleigh Fading

    Publication Year: 1983 , Page(s): 568 - 572
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    This paper presents measured error-rate performance of binary FSK with discriminator detection in simulated Rayleigh fading with time delay spread. Measured relations between error rate and carrier-to-noise ratio are shown for a range of time delay spreads. We have verified that the effect of time delay spread on error rate can be described by only one parameter, the ratio of the rms delay spread to the transmitted baud time. Intersymbol interference from time delay spread causes an irreducible error rate for FSK, even for infinite carrier-to-noise ratio. For 64 kbit/s binary FSK, the 2.6μs rms delay spread typical of the urban environment produces an irreducible error rate of 3 percent. The measured irreducible error rate for binary FSK with discriminator detection is proportional to the fourth power of the ratio of rms delay spread to baud time. This functional dependence is identical to that predicted analytically for FSK with incoherent matched-filter detection. View full abstract»

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  • Dynamic Frame Length ALOHA

    Publication Year: 1983 , Page(s): 565 - 568
    Cited by:  Papers (131)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    Adding frame structure to slotted ALOHA makes it very convenient to control the ALOHA channel and eliminate instability. The frame length is adjusted dynamically according to the number of garbled, successful, and empty timeslots in the past. Each terminal that has a packet to transmit selects at random one of the n timeslots of a frame. Dynamic frame length ALOHA achieves a throughput (expected number of successful packets per timeslot) of 0.426 which compares favorably with the 1/e (\approx 0.368) upper bound of ordinary slotted ALOHA. View full abstract»

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  • Modulation Methods Related to Sine-Wave Crossings

    Publication Year: 1983 , Page(s): 503 - 508
    Cited by:  Papers (5)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    A bounded band-limited signal may be represented by its sine-wave crossings, i.e., by a set of points on the time axis at which it crosses a reference sinusoid. If, at these points, pulses of a standard shape are generated, we obtain a position modulated pulse train. This pulse train is analyzed in detail. Two other modulation methods related to sine-wave crossings are also discussed, namely, edge position modulation of a square wave and bipolar pulse duration modulation. In all cases, the modulated waves may be expressed as sums of an infinite number of sinusuidal carriers amplitude modulated by Chebyshev polynomials of modulating signals. View full abstract»

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  • The Laplacian Pyramid as a Compact Image Code

    Publication Year: 1983 , Page(s): 532 - 540
    Cited by:  Papers (1644)  |  Patents (212)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1200 KB)  

    We describe a technique for image encoding in which local operators of many scales but identical shape serve as the basis functions. The representation differs from established techniques in that the code elements are localized in spatial frequency as well as in space. Pixel-to-pixel correlations are first removed by subtracting a lowpass filtered copy of the image from the image itself. The result is a net data compression since the difference, or error, image has low variance and entropy, and the low-pass filtered image may represented at reduced sample density. Further data compression is achieved by quantizing the difference image. These steps are then repeated to compress the low-pass image. Iteration of the process at appropriately expanded scales generates a pyramid data structure. The encoding process is equivalent to sampling the image with Laplacian operators of many scales. Thus, the code tends to enhance salient image features. A further advantage of the present code is that it is well suited for many image analysis tasks as well as for image compression. Fast algorithms are described for coding and decoding. View full abstract»

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  • Acquisition and Tracking Performance of a PLL Using a Class of Nonlinear Filters

    Publication Year: 1983 , Page(s): 493 - 502
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    A class of nonlinear filters was proposed in [1] as an alternative loop filter of a PLL. This paper examines further aspects of the performance of a PLL incorporating such a nonlinear filter. The acquisition performance due to frequency offsets and the steadystate tracking performance in the presence of noise and frequency offsets are analyzed and compared with experimental and simulation results. The noise analysis is based on techniques using the FokkerPlanck equation. The effect of the nonlinearity in the loop filter is approximated using a quasi-linearization approach. A modification to the original nonlinear filter structure is proposed in order to obtain the best noise performance in the presence of frequency offsets. The overall improvement in performance of a PLL with a nonlinear filter is evaluated and compared with a conventional PLL and other methods of improved acquisition performance such as the sweep method. The necessary graphs and formulas are presented for the design of a PLL with a nonlinear filter. The extra available design parameter enables the compromise between acquisition and noise performance to be overcome to a significant degree. View full abstract»

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  • Strategies for Weather-Dependent Data Acquisition

    Publication Year: 1983 , Page(s): 509 - 517
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (824 KB)  

    A strategy for data acquisition from a very distant spacecraft is presented, when the system performance can be severely degraded by the earth's weather due to the high microwave frequency being used. Two cases are considered, one in which there is a certain minimum data rate to be maintained and one in which there is not. The goal is to maximize expected data return, where we assume that there are always new data, or a backlog of old data, that can be sent if conditions are favorable. When there is no minimum rate to be maintained, the optimum strategy is typically the greedy strategy, which always transmits at that single rate which maximizes the expected data returned. If there is a minimum data rate which we strive to maintain even in adverse conditions, the optimum strategy transmits simultaneously at the minimum or base data rate and typically at a bonus data rate. We use a coding system designed for the bandwidthconstrained degraded broadcast channel. The optimum version of this system can, under realistic assumptions, save on the order of 5 dB over the conservative strategy of just transmitting at a single lower data rate. View full abstract»

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  • Soft Decision Demodulation and Transform Coding of Images

    Publication Year: 1983 , Page(s): 572 - 577
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1016 KB)  

    This paper describes a transform image coding system that uses soft decision demodulation to control channel errors. In soft decision demodulation, if certain received bits of a codeword representing a coefficient are unreliable, then the codeword is rejected and the corresponding coefficient is replaced with an estimate. By monitoring the three highest energy DCT coefficients, the reconstructed image quality can be improved for a channel with a bit error probability of 10-2. View full abstract»

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  • Design of Coding and Modulation for Power-Efficient Use of a Band-Limited Optical Channel

    Publication Year: 1983 , Page(s): 560 - 565
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    We show that Q -ary pulse-position modulation with raised cosine pulses minimizes the average power (photons/s) required to communicate at a specified throughput rate (nats/s) over a band-limited, noisy optical channel. The best choice of Q is identified, as are other encoder parameters. View full abstract»

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  • Capacity Limit of the Noiseless, Energy-Efficient Optical PPM Channel

    Publication Year: 1983 , Page(s): 546 - 548
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    The energy-efficient capacity of the noiseless optical PPM channel is examined. It is shown that, although the capacity per photon can be made to increase without bound, the capacity per channel use (for best energy efficiency) is always less than 2 nats and approaches 2 nats/symbol as the bandwidth expansion factor goes to infinity. View full abstract»

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  • Go-Back-N ARQ Schemes for Point-to-Multipoint Satellite Communications

    Publication Year: 1983 , Page(s): 583 - 589
    Cited by:  Papers (26)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    The conventional go-back- N ARQ is modified so as to be applicable to point-to-multipoint communication by using a control block that indicates the occurrence of retransmission to all the receivers. This paper also presents a "tandem error control scheme," in which the up-link and the down-links use separate go-back- N ARQ's. The throughput efficiency of the tandem go-back- N ARQ is analyzed. Specifically, the mathematical formula for the throughput efficiency is obtained for cases in which there is a single receiver. The throughput efficiencies of these schemes are also evaluated by simulation. View full abstract»

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  • Representation of Intermodal Dispersion in Multimode Fiber Links

    Publication Year: 1983 , Page(s): 528 - 531
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    This paper analyzes statistical aspects of intermodal dispersion in multimode fiber links using a linear systems model. It is shown that the dependence of the response of a fiber section on the power distribution in the input modes leads to uncertainties in the characterization of the rms time dispersion of the section when it forms a part of a fiber link. Analytical expressions for the link dispersion in terms of three section parameters are derived, and a recursive method for computing link dispersions when these parameters are known for each section of the link is outlined. Calculations indicating the applicability of the method are also presented. View full abstract»

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  • Design of an Economical Multidrop Network Topology with Capacity Constraints

    Publication Year: 1983 , Page(s): 590 - 591
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    This paper compares several algorithms for designing economical multidrop network topologies with capacity constraints. Sharma's algorithms, the outside-to-inside-city approach (OICCA, which happens to be a special case of the Esau-Williams algorithm) and the Exchange algorithm (predecessor of several "greedy" algorithms), are then compared to the Esau-Williams algorithm (EWA) and to EWA plus Sharma's exchange algorithm for some practical network applications. View full abstract»

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  • Rejection of CW Interference in QPSK Systems Using Decision-Feedback Filters

    Publication Year: 1983 , Page(s): 473 - 483
    Cited by:  Papers (10)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB)  

    In this paper, the performance of QPSK systems using complex transversal filters with additional decision-feedback taps, in the presence of Gaussian noise and a single CW interferer, is analyzed. Both one-sided (with lagging taps) and two-sided transversal filters with additional decision-feedback taps are considered. Analytic expressions for the tap weights and the minimum mean square errors are obtained. The effect of error propagation on the error probability is discussed and an approximate solution for the error probability is obtained. The transient behavior of the filters using the LMS adaptation algorithm is analyzed. It is shown that if the filter is used for rejecting CW interference only, the one-sided decision-feedback filter is preferred. View full abstract»

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  • The Optimum Closed-Loop Transfer Function of a Phase-Locked Loop Used for Synchronization Purposes

    Publication Year: 1983 , Page(s): 549 - 553
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    This paper presents an expression for the optimum closed-loop transfer function of a phase-locked loop (PLL) which estimates the phase of an unmodulated sinuosoid corrupted by an additive random disturbance. This matter has been extensively treated (e.g., [1, ch. 4]) in the conventional PLL theory, where the disturbance is a stationary noise process. However, for an important class of synchronizers operating on a PAM waveform corrupted by stationary noise, the disturbance at the input of the PLL cannot be treated as a stationary process. In this case we show that the PLL transfer function which is optimized according to the conventional PLL theory is far from optimum. Therefore, we derive the closed-loop transfer function which is optimum for a more general disturbance. This extension of the conventional PLL theory applies to most synchronizers. View full abstract»

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  • Pulse-Position Modulation for Transmission Over Optical Fibers with Direct or Heterodyne Detection

    Publication Year: 1983 , Page(s): 518 - 527
    Cited by:  Papers (26)  |  Patents (31)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    The best monomode optical fiber links have bandwidths orders of magnitude greater than that of the information currently transmitted over them. This excess bandwidth can be exploited using digital PPM to improve receiver sensitivity. This paper analyzes the receiver sensitivity of an optical PPM system over a slightly dispersive channel, i.e., where both "wrong slot" and "false alarm" errors are important. It is shown that receiver sensitivity of better than 100 photons per binary bit-time is theoretically possible using direct detection and uncoded PPM. Ideal heterodyne detection should reduce this to below 5 photons per binary bit-time. Timing extraction and a digital modulation method are discussed. View full abstract»

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  • A Self-Organizing Random Array Communications Relay

    Publication Year: 1983 , Page(s): 484 - 492
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (904 KB)  

    A sparse random array with self-organizing properties is proposed as a communications relay. The relay consists of N randomly deployed, low-power transmit/receive elements with capabilities for phasing their retransmissions to arrive coherently at the ultimate destination. Signal-to-noise ratio results for conventional modulation schemes corrupted with additive noise are given, together with possible system block diagrams. It is concluded that, in spite of the complexity, practical systems can be built with extremely low electromagnetic radiation densities with point-to-point characteristics at least as good as with conventional systems employing high power relays. The novel characteristics make the proposed system particularly suitable for tactical military communication, and variants thereof may find application in urban communication. View full abstract»

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  • Performance Analysis of FIR ADM Digital Filters

    Publication Year: 1983 , Page(s): 577 - 583
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    Performance and realization of finite impulse response (FIR) digital filters that use an adaptive delta modulator as an analog/ digital converter have been studied. These filters require no multiplication and offer many advantages over conventional PCM filters including low power consumption, small size, and cost effectiveness. Analytical formulas have been derived for the expected mean-squared errors and also for the word length necessary to achieve the desired performance. Computer simulation has been done to optimize the parameter values and to verify the results of performance analysis. In addition, design of FIR ADM digital filters for processing single and multichannel signals has been considered. View full abstract»

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  • A Spectral Analysis of M-ary Direct Sequence Spread-Spectrum Multiple Access Communication Systems

    Publication Year: 1983 , Page(s): 541 - 546
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    This paper presents the power spectrum of the transmitted signal in a synchronous spread-spectrum communication system in which the users' information symbol sequences are encoded into M -ary channel symbol sequences. Furthermore, when maximal-length shift register sequences are used as the spreading code sequences of the system, the average power spectrum over all possible sets of the allowable simultaneous users is presented. It is shown that distribution of the spectrum is influenced considerably by the spreading code and the channel symbol sequences. View full abstract»

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  • Analysis of a Digital Bit Synchronizer

    Publication Year: 1983 , Page(s): 554 - 560
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    A simple digital bit synchronizer utilizing discrete phase control is discussed. The proposed system is intended for operation with NRZ coded binary signals. A finite state Markov chain model is used to evaluate the steady-state phase jitter performance of the bit synchronizer in the presence of additive white Gaussian noise. The theoretical results are confirmed by computer simulation. The same mathematical model is used to investigate the transient (acquisition) performance of the synchronizer. Finally, the performance of the synchronizer as a data detector is discussed and the error probability performance is compared with that of the optimum detector. 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