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Communications, IEEE Transactions on

Issue 7 • Date July 1984

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Displaying Results 1 - 19 of 19
  • [Front cover and table of contents]

    Publication Year: 1984 , Page(s): 0
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    Freely Available from IEEE
  • [Back cover]

    Publication Year: 1984 , Page(s): 0
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    Freely Available from IEEE
  • Random Multiple-Access Communication and Group Testing

    Publication Year: 1984 , Page(s): 769 - 779
    Cited by:  Papers (34)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1168 KB)  

    We study the application of group testing to the design of efficient algorithms for random multiple-access communication systems. Both direct transmission and reservation systems are considered for various types of channel feedback. We propose and analyze algorithms based on conventional and generalized group testing techniques. The proposed algorithms outperform TDMA and algorithms based on binary tree search and possess certain optimality properties. View full abstract»

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  • Multiplierless Implementations of MF/DTMF Receivers

    Publication Year: 1984 , Page(s): 839 - 847
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    The ever-increasing use of VLSI in telecommunications systems is leavening the search of new algorithms for task realizations suited to VLSI implementations of systems. Toward this search, the paper presents implementations for MF/DTMF receivers, which are based on multiplierless basic filters or primitive VLSI cells such as (1 + z^{-n}) , (1 - z^{-n}) , and (1 \pm z^{-n} + z^{-2n}) . These implementations require parallel processing and are designed to meet the requirements of a switching system. View full abstract»

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  • Performance of Portable Radio Telephone Using Spread Spectrum

    Publication Year: 1984 , Page(s): 762 - 768
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    A 2 GHz band portable radio telephone has been fabricated using the spread-spectrum technique. We describe the fundamental performance, bit error rates with and without interference, measured using the experimental telephone. The telephone system's user density is estimated by computer simulation under relatively realistic conditions. View full abstract»

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  • Synthesis of Communicating Finite-State Machines with Guaranteed Progress

    Publication Year: 1984 , Page(s): 779 - 788
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1008 KB)  

    We present a methodology to synthesize two communicating finite-state machines which exchange messages over two one-directional, FIFO channels. The methodology consists of two algorithms. The first algorithm takes one machine M , and constructs two communicating machines M' and N' such that 1) M' is constructed from M by adding some receiving transitions to it, and 2) the communication between M' and N' is bounded and free from deadlocks, unspecified receptions, nonexecutable transitions, and state ambiguities. The second algorithm takes the two machines M' and N' which result from the first algorithm, and computes the smallest possible capacities for the two channels between them. Both algorithms require an O(st) time, where s is the number of states in the given machine M , and t is the number of state transitions in M ; thus, the methodology is practical to use. View full abstract»

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  • Hamming Coding of DCT-Compressed Images Over Noisy Channels

    Publication Year: 1984 , Page(s): 856 - 861
    Cited by:  Papers (18)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    Theoretical and simulation results of using Hamming codes with the two-dimensional discrete cosine transform (2D-DCT) at a transmitted data rate of 1 bit/pixel over a binary symmetric channel (BSC) are presented. The design bit error rate (BER) of interest is 10-2. The (7, 4), (15, 11), and (31, 26) Hamming codes are used to protect the most important bits in each 16 by 16 transformed block, where the most important bits are determined by calculating the mean squared reconstruction error (MSE) contributed by a channel error in each individual bit. A theoretical expression is given which allows the number of protected bits to achieve minimum MSE for each code rate to be computed. By comparing these minima, the best code and bit allocation can be found. Objective and subjective performance results indicate that using the (7, 4) Hamming code to protect the most important 2D-DCT coefficients can substantially improve reconstructed image quality at a BER of 10-2. Furthermore, the allocation of 33 out of the 256 bits per block to channel coding does not noticeably degrade reconstructed image quality in the absence of channel errors. View full abstract»

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  • On Optimum and Nearly Optimum Data Quantization for Signal Detection

    Publication Year: 1984 , Page(s): 745 - 751
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    The application of companding approximation theory to the quantization of data for detection of coherent signals in a noisy environment is considered. This application is twofold, allowing for greater simplicity in both analysis and design of quantizers for detection systems. Most computational methods for designing optimum (most efficient) quantizers for signal detection systems are iterative and are extremely sensitive to initial conditions. Companding approximation theory is used here to obtain suitable initial conditions for this problem. Furthermore, the companding approximation idea is applied to design suboptimum quantizers which are nearly as efficient as optimum quantizers when the number of levels is large. In this design, iteration is not needed to derive the parameters of the quantizer, and the design procedure is very simple. In this paper, we explore this approach numerically and demonstrate its effectiveness for designing and analyzing quantizers in detection systems. View full abstract»

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  • Decimations of the Frank-Heimiller Sequences

    Publication Year: 1984 , Page(s): 851 - 853
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    The Frank-Heimiller sequence of period N2with N phases is constructed by writing the N by N discrete Fourier transform matrix by rows. The periodic autocorrelation sidelobes for such a sequence are all zero. Small families of N -phase sequences, with optimal periodic cross correlations, can be formed by judicious selection of decimations of the Frank-Heimiller sequence. View full abstract»

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  • Interference Cancellation System for Satellite Communication Earth Station

    Publication Year: 1984 , Page(s): 796 - 803
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    A new interference cancellation system was devised to suppress the mutual interference between satellite and terrestrial communication systems and to expand the number of potential earth station locations for effective frequency reuse. This system basically adopts the sidelobe canceller concept and has main and auxiliary antennas. The originality of this system lies in that the auxiliary channel signal to be combined with the main channel signal is modulated by a low frequency signal, and the amplitude and phase controlling voltages are obtained by means of envelope detection, to get the envelope of the residue, and then by phase detection, using the envelope signal and the low frequency signal. As a result of experiments, more than 40 dB cancellation was achieved over a 50 MHz range for CW, FM(TP, TV) and PSK signals, even if the desired and interference signals are in the cochannel. In the field test on a 45 km path, sufficient cancellation performance and response were obtained even during fading periods. View full abstract»

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  • Unique-Word Detection in TDMA: Acquisition and Retention

    Publication Year: 1984 , Page(s): 804 - 817
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1120 KB)  

    Establishing frame and burst synchronism in TDMA requires detection of a known, approximately periodic signal corrupted by noise. This paper presents a Markovian modeling approach to analyzing the performance of a sync detector that repeatedly compares the output of an n -bit binary correlator to an acceptance/rejection threshold. The detector is defined to be in one of two modes of operation: INITIAL ACQUISITION, during which it seeks to identify the start of a frame; and RETENTION, in which periodic detection of the frame (and burst) is essential for TDMA operations. During acquisition, the n -bit sync word is assumed embedded in random data, and bit errors are assumed uncorrelated. The acquisition models permit ready computation of acquisition-time statistics and the probability of false acquisition. The retention models identify paths by which synchronism can be lost, their probability of occurrence, and a resulting mean time to loss of synchronism. Unlike the acquisition models, account is taken of the deterministic data pattern immediately preceding the sync word, and sources of timing error that alter the sync word's ideally periodic arrival. The models presented in this paper allow the detector's key performance indexes to be assessed as a function of its external environment: bit-error rate, timing uncertainty, and data pattern preceding the sync word; and internal parameters: sync word pattern, correlation detection threshold, detection aperture widths, number of consecutive detections before acquisition can be declared, and the number of tolerable consecutive sync word misses before synchronism is declared lost. View full abstract»

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  • A Two-Power-Level Method for Multiple Access Frequency-Hopped Spread-Spectrum Communication

    Publication Year: 1984 , Page(s): 853 - 855
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    This paper suggests a technique applicable to chip-synchronous frequency-hopping MFSK multiaccess communication whereby each user has some high-power-level slots and some low-power-level slots. The optimum proportion of high-power slots is slightly less than 1/e where e is the natural logarithm base. For this optimum proportion, the data rate efficiency is improved by about 50 percent for fixed bit error rate in the interference-only case. View full abstract»

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  • Preemphasis/Deemphasis Effect on the Output SNR of SSB-FM

    Publication Year: 1984 , Page(s): 848 - 850
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    The effect of preemphasis/deemphasis on the noise power output of FM detectors for SSB-FM is studied. Two cases are considered: namely, when the modulating signal is assumed to be sinusoidal and when it is a Gaussian random process. For both cases the noise is assumed to be stationary and Gaussian. For a sinusoid modulating signal, the improvement of (S/N)_{0} for SSB-FM detectors is obtained when the modulation index β lies in the interval (0.1-12.0) with negligible improvements for higher β. For a Gaussian modulating signal, improved results are obtained for a modulation index in the interval (0.1-0.6). View full abstract»

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  • The Effectiveness and Efficiency of Hybrid Transform/DPCM Interframe Image Coding

    Publication Year: 1984 , Page(s): 832 - 838
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1048 KB)  

    We seek to evaluate the efficiency of hybrid transform/ DPCM interframe image coding relative to an optimal scheme that minimizes the mean-squared error in encoding a stationary Gaussian image sequence. The stationary assumption leads us to use the asymptotically optimal discrete Fourier transform (DFT) on the full frame of an image. We encode an actual image sequence with full-frame DFT/DPCM at several rates and compare it to previous interframe coding results with the same sequence. We also encode a single frame at these same rates using a full-frame DFT to demonstrate the inherent coding gains of interframe transform DPCM over intraframe coding. We then generate a pseudorandom image sequence with precise Gauss-Markov statistics and encode it by hybrid full-frame DFT/DPCM at various rates. We compare the signal-to-noise ratios (SNR's) of these reconstructions to the optimal ones calculated from the rate-distortion function. We conclude that in a medium rate range below 1 bit/pel/frame where reconstructions for hybrid transform/ DPCM may be unsatisfactory, there is enough margin for improvement to consider more sophisticated coding schemes. View full abstract»

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  • Network Design for a Large Class of Teleconferencing Systems

    Publication Year: 1984 , Page(s): 789 - 796
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (992 KB)  

    This paper introduces a new class of network design problems implementing an integrated teleconferencing environment consisting of a video space showing images of the participants, an audio space providing their voices, and a graphics space providing reference and discussion material for the conference. These various spaces provide services of differing quality and type. The problem posed is to design topologically optimal networks that are least costly and that will have the flexibility to carry conferences of differing service quality and type. The actual networks studied in this paper consist of the design of a private network for a single conference among N identical, but arbitrarily located, sites. Network designs will be minimum link-cost or constrained minimum link-cost optimal, where the first is minimal over all possible network topologies and the second is constrained to consider only those topologies that have the minimum number of links. For terrestrial systems, one of the interesting results is that classical network topologies such as rings and minimum spanning trees are optimal for some conference types. However, no topology is optimal for all types, and some topologies use their capacity very poorly when used for a type for which they were not optimized. Unlike terrestrial networks, satellite networks may be easily configured to have all of their capacity available for all conference types. View full abstract»

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  • On M-ary DPSK Transmission Over Terrestrial and Satellite Channels

    Publication Year: 1984 , Page(s): 752 - 761
    Cited by:  Papers (7)
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    The error rate performance of M -ary DPSK systems is investigated in the presence of phase change offset, noise correlation, and power imbalance. Both the terrestrial channel and the hard-limiting satellite repeater channel are considered. In the satellite repeater case, the noise correlations and power imbalances are assumed to be present on both the up- and downlinks. The emphasis is on exact results, or asymptotic approximations obtained therefrom, as opposed to error rate bounds. Most of the results are given in terms of integrals readily evaluated by quadrature. Performance curves showing the effects of the various impairments are presented. Some specific conclusions which follow from the results are that 1) the phase change offset is relatively unimportant for M \geq 4 , 2) the M -ary case is less sensitive to imbalance than is the binary case, and 3) the satellite link performance depends strongly upon the quality of the uplink. View full abstract»

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  • TSI-OQPSK for Multiple Carrier Satellite Systems

    Publication Year: 1984 , Page(s): 818 - 825
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    The performance of TSI-OQPSK (two-symbol-interval-offset QPSK) modems in nonlinearly amplified (saturated or hard-limited), adjacent channel interference (ACI) satellite earth station environment is studied. In closely spaced mobile satellite channels and higher frequency (≥ 14 GHz) earth stations, the effect of ACI on the P_{e} = f(E_{b}/N_{0}) performance of faded systems may become very significant. Simulation results indicate that for the frequently used close channel spacing case (≤ 77 percent of the bit rate) and a practical fade depth (≥ 12 dB), our new TSI-OQPSK signal (n = 2) has 1 dB less degradation than IJF-OQPSK and 3 dB less than OQPSK, and that conventional QPSK could not operate in such an environment. View full abstract»

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  • A One-Stage Look-Ahead Algorithm for Delta Modulators

    Publication Year: 1984 , Page(s): 861 - 863
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    This paper describes a one-stage look-ahead algorithm for adaptive delta modulators. The algorithm does not require the calculation of two encoding paths nor does it require the decision circuitry to choose the optimum path. View full abstract»

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  • Noise Reduction in Image Sequences Using Motion-Compensated Temporal Filtering

    Publication Year: 1984 , Page(s): 826 - 831
    Cited by:  Papers (80)  |  Patents (31)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (936 KB)  

    Noise in television signals degrades both the image quality and the performance of image coding algorithms. This paper describes a nonlinear temporal filtering algorithm using motion compensation for reducing noise in image sequences. A specific implementation for NTSC composite television signals is described, and simulation results on several video sequences are presented. This approach is shown to be successful in improving image quality and also improving the efficiency of subsequent image coding operations. 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