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Communications, IEEE Transactions on

Issue 8 • Date August 1982

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Displaying Results 1 - 25 of 31
  • [Front cover and table of contents]

    Publication Year: 1982 , Page(s): 0
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  • Comments on "Apsects of PCM Regenerator Design for Crosstalk Limited Enviroments"

    Publication Year: 1982 , Page(s): 2000 - 2002
    Cited by:  Papers (1)
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  • Author's reply

    Publication Year: 1982 , Page(s): 2002
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  • [Back cover]

    Publication Year: 1982 , Page(s): 0
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  • The Effects of Bandpass Limiters on Mth Phase Tracking Systems in the Presence of Sinusoidal Interference and Noise

    Publication Year: 1982 , Page(s): 1842 - 1847
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    The effects of bandpass limiters on M th phase tracking systems in the presence of multiple sinusoidal interferences and additive Gaussian noise are considered. We derive general expressions for the ratio of the output to the input SNR (the SNR ratio) for an M th-power tracking loop with and without a bandpass limiter. The numerical calculations for the squaring limited and fourth-power limited PLL's in the presence of multiple sinusoidal interferences and noise are carried out, and the results are compared to those for similar loops without limiters. It is found that sinusoidal interference causes the limit of the SNR ratio for infinite carrier-to-noise ratio (CNR) to be no longer consistent with that for only Gaussian noise. The SNR ratio is degraded more as the carrier-to-interference ratio (CIR) decreases and the number of sinusoidal interferences increases. Furthermore, it is found that for the fourth-power PLL, the limiter does not always enhance the output SNR at moderate to strong input SNR's in the presence of sinusoidal interference. View full abstract»

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  • Cochannel Interference in High-Capacity Mobile Radio Systems

    Publication Year: 1982 , Page(s): 1973 - 1978
    Cited by:  Papers (42)
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    The probability of cochannel interference is evaluated for a mobile radio system operating in Rayleigh fading and log-normal shadowing environment. All cochannel cells surrounding the base station are taken into consideration in this evaluation. The results obtained are used to calculate the reuse distance and the cluster size (number of cells in a group). The blocking probability, the number of channels in each cell, the protection ratio, and the standard deviation are taken as parameters in this evaluation. The results show that shadowing has a severe effect on the interference level and on the channel reuse distance ratio. View full abstract»

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  • Real-Time Software Simulation of the HF Radio Channel

    Publication Year: 1982 , Page(s): 1809 - 1817
    Cited by:  Papers (12)
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    Modern array processor and digital signal processing technologies have been applied to develop a real-time, software-based system that simulates high-frequency (HF) radio links. This system is called an HF Channel Simulator. In this paper we describe the design features and performance of one such simulator, based on the Floating Point Systems AP-120B array processor. The simulator characteristics are a 4 kHz signal bandwidth and a great flexibility in the selection of link parameters available to the user. All distortions are at least 50 dB below the desired signal output level. View full abstract»

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  • A Further Comment on the Spectral Width of MSK-Type Signaling Waveforms Relative to That of PSK

    Publication Year: 1982 , Page(s): 1983 - 1984
    Cited by:  Patents (1)
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    We show that the width of the center spectral lobe for a wide class of MSK-type signals is lower bounded by that for conventional PSK, and we also provide an expression that can be used to determine the width of the center spectral lobe for MSK. View full abstract»

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  • Sliding-Block and Random Source Coding with Constrained Size Reproduction Alphabets

    Publication Year: 1982 , Page(s): 1859 - 1867
    Cited by:  Papers (16)
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    Recent research has shown that nearly optimum ratedistortion function performance can be obtained in encoding memoryless continuous-amplitude sources using a constrained-size reproduction alphabet. In this paper, we use a four-letter reproduction alphabet in encoding the Gaussian and Laplacian sources with the squared-error distortion measure. We introduce a sliding-block code generator/decoder and perform extensive coding simulations at a rate of one bit/source symbol. The average distortions in those simulations are much below the optimum quantization distortion and, with much smaller search intensity, are about the same or lower than distortions reported previously in comparable research. The slidingblock code results are also compared to those of parallel random coding simulations with the same reproduction alphabet and rate. View full abstract»

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  • Interframe DPCM with Adaptive Quantization and Entropy Coding

    Publication Year: 1982 , Page(s): 1888 - 1899
    Cited by:  Papers (4)
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    The object of this work has been to study encoding of monochrome pictures with a rate of about 1 bit per picture element (pel). Differential pulse code modulation, DPCM, has been chosen to make the system reasonably simple. This motivates the choice of a fixed three-dimensional predictor made separable in time and space. It essentially amounts to encoding the frame difference using a two dimensional predictor. To improve performance, the quantizer is made adaptive and the encoding is combined with delayed decision. A three-level quantizer is being used with an adaptive scheme that works with either forward or backward estimation. The output from the DPCM unit is redundant and we have adopted entropy coding to further reduce the bit rate. The entropy measure is also used to adjust the quantizer parameters to achieve the desired bit rate of 1 bit/pel. Encoding experiments were carried out on a complex videophone scene by means of computer simulations. View full abstract»

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  • Effect of Coding on the Jitter Accumulation in Baseband Digital Transmission

    Publication Year: 1982 , Page(s): 1818 - 1827
    Cited by:  Papers (2)
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    A method is presented to evaluate the effect of line codes on the timing jitter in a chain of PCM repeaters. The timing circuit in each regeneration section consists of a square-law device followed by a resonant circuit tuned to the transmission rate and by a zero-crossing detector. The analysis applies to a broad class of line codes. The results of the paper indicate that the influence of the code on the jitter accumulation is fairly marginal and that the jitter variance is maximum when the symbols are uncorrelated. View full abstract»

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  • Some Experimental Results on In-Band Amplitude Dispersion and a Method for Estimating In-Band Linear Amplitude Dispersion

    Publication Year: 1982 , Page(s): 1875 - 1888
    Cited by:  Papers (16)
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    In-band amplitude measurement was conducted on a 63.4 km test path with an oversea section (normal reflection point was on the ground), using a frequency band from 4440 to 4500 MHz. Results on peak-to-peak amplitude dispersion and linear amplitude dispersion were obtained for both nondiversity and idealized space diversity receptions. Potential improvements by space diversity in terms of reductions of amplitude dispersion were remarkable in the large amplitude dispersion region. An analysis of the in-band amplitude pattern was made in order to identify which multiray is most responsible for amplitude dispersion during multipath fading. The main cause of amplitude dispersion was found to be waves irregularly reflected from the sea surface and waves reflected from the ground, with a long delay but small amplitude. A frequency correlation function for received power, which is necessary for estimating linear amplitude dispersion, was derived theoretically, for the three-path model. The theoretical frequency correlation agrees well with that measured on this path. View full abstract»

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  • Teletraffic Analysis for Multicell Mobile Radio Telephone Systems

    Publication Year: 1982 , Page(s): 1905 - 1909
    Cited by:  Papers (11)
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    New teletraffic formulas are derived for the congestion in multicell mobile radio telephone systems. Fixed, dynamic, and hybrid channel asignment are considered and "tromboning," where mobileto-mobile calls go via a base station, is taken into account. The formulas agree with previously published sumulation results. View full abstract»

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  • Intelligible Crosstalk Between Two FDM/FM Carriers Accessing Double Cascaded Nonlinear Amplifiers

    Publication Year: 1982 , Page(s): 1993 - 2000
    Cited by:  Papers (1)
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    A method of evaluating double intelligible crosstalk between two frequency division multiplexed frequency modulated (FDM/FM) carriers accessing the same earth station high-power amplifier (HPA) and satellite transponder traveling wave tube amplifier (TWTA) has been developed. The analysis takes into consideration the AM/AM and AM/PM characteristics of the two cascaded memoryless nonlinear amplifiers, and the amplitude and group delay variations of transmission paths preceding the first nonlinear amplifier and of the path between the two nonlinear amplifiers. Results of the double intelligible crosstalk evaluation show the existence of significant distortion cross terms caused by the two cascaded nonlinearities and filters, in addition to individual distortion terms by each nonlinearity. Specific illustrative examples are discussed, and some practical suggestions are given for controlling crosstalk impairment effects in satellite channels with double cascaded nonlinear amplifiers. View full abstract»

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  • Integrated Digital Switching System with Queueing Storage Facility

    Publication Year: 1982 , Page(s): 1900 - 1905
    Cited by:  Patents (7)
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    This paper outlines the features of a new integrated switching system for voice and data. It is composed of integrated subscriber terminals, integrated subscriber lines, an integrated digital switching system, and integrated storage facilities. This paper shows that the introduction of the integrated storage facility can create various new service utilities and improve the traffic capacity of the system. View full abstract»

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  • Performance Evaluation Methods for an Integrated Voice/Data Link

    Publication Year: 1982 , Page(s): 1848 - 1858
    Cited by:  Papers (34)
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    This paper presents an approximation method for estimating the average number of data packets in a SENET-concept integrated voice and data system. The method is simple to use and its estimates are found to be in good agreement with simulation results. In general, the method applies to any system that integrates packet traffic with a more slowly varying traffic class that can preempt a portion of the packet transmission capacity. View full abstract»

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  • Performance Analysis of Digital Integrate-and-Dump Filters

    Publication Year: 1982 , Page(s): 1979 - 1983
    Cited by:  Papers (4)
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    Key design parameters associated with the operation of a digital integrate-and-dump filter are identified in this paper. Performance degradation effects associated with the selection of these parameters such as analog-to-digital converter (ADC) gain loading factor, number of bits used, predetection bandwidth, sampling rate, and accumulator length are considered. Numerical results of practical interest are also provided. View full abstract»

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  • 16 QAM Carrier Recovery PLL for Service-Channel Transmission Using FSK Additional Modulation

    Publication Year: 1982 , Page(s): 1918 - 1925
    Cited by:  Patents (5)
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    This paper describes the design and performance of the 16 QAM carrier recovery PLL for service-channel transmission using FSK additional modulation. When FSK additional modulation is applied, tracking phase error occurs and corrupts the 16 QAM signal. To reduce the phase error without widening the loop noise bandwidth is an important issue in the 16 QAM-FSK double modulation scheme. An analytical expression to estimate the peak phase error due to class 4 partial response FSK is established, By using the approximation formula, an optimization of the carrier recovery PLL is presented. Moreover, experiments and computer simulations are carried out for the 200 Mbit/s 16 QAM and 64 kbit/s SC double modulation system. As a result, it is demonstrated that a 0.1 dB 16 QAM equivalent power loss and an 8 dB frequency deviation margin of SC transmission performance can be obtained. View full abstract»

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  • On the Effects of CW Interference on MSK Signal Reception

    Publication Year: 1982 , Page(s): 1925 - 1929
    Cited by:  Papers (7)
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    The probability of error in a minimum (frequency)-shift keying (MSK) system is obtained for the case of Gaussian noise only and for the case of CW interference in addition to Gaussian noise. Analysis is made for the fading channel case assuming Rayleigh fading. The results are compared with those of BPSK. It is found that MSK is more immune to CW interference than BPSK. View full abstract»

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  • Four-Level Pulse Width Modulation for Fiber Optic Communications

    Publication Year: 1982 , Page(s): 1958 - 1963
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    The performance of a digital fiber optical system employing four-level pulse width modulation (PWM) is considered. It is shown that PWM may be an attractive alternative to pulse amplitude modulation (PAM), especially if a wide band channel is used. The probability density function (pdf) of the timing error is obtained in terms of the pdf of the noise amplitude, taking into account the thermal noise of the amplifier and the signal-dependent shot noise introduced by the photodiode detector. Near-Gaussian optical pulse edges at the receiver are assumed. Using typical system parameters, the variation of bit error rate (BER) with power level, and the effects of different bit rates, mean photodetector gain, and system bandwidths are calculated. It is observed that minimum BER's are achieved at moderate values of mean photodetector gain and that increased system bandwidth results in increased receiver sensitivity. View full abstract»

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  • SNR Fluctuation and Nonlinear Distortion in PFM Optical NTSC Video Transmission Systems

    Publication Year: 1982 , Page(s): 1868 - 1875
    Cited by:  Papers (11)  |  Patents (1)
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    The causes of SNR fluctuation and nonlinear distortion, uncovered during field trials of PFM optical video transmission systems, are investigated theoretically and experimentally. Degradations are found to be significant in long distance transmission at a wavelength around 0.85 μm. This is because PFM pulse jitter closely relating to the degradation is caused by laser mode competition and its interaction with fiber material dispersion. However, at a wavelength around 1.3 μm, where fiber material dispersion is negligible, only small nonlinear distortion due to feedback light from connectors is observed. Thus, good picture quality is maintained over long distance transmission. View full abstract»

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  • Comparison of Performance of Digital Modulation Techniques in the Presence of Adjacent Channel Interference

    Publication Year: 1982 , Page(s): 1984 - 1993
    Cited by:  Papers (11)  |  Patents (3)
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    The performance of four digital modulation techniques are compared to one another when each is received in the presence of adjacent channel interference. The interfering waveforms that each modulation format sees are identical to the modulation format under consideration. The four types of modulation are QPSK, 8-PSK, 16QASK, and QPR. Upper bounds to the probability of error are derived and used to evaluate the relative merits of the different schemes. View full abstract»

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  • Optimum FIR Transmitter and Receiver Filters for Data Transmission Over Band-Limited Channels

    Publication Year: 1982 , Page(s): 1909 - 1915
    Cited by:  Papers (45)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    The paper deals with the design of digital transmitter and receiver filters with finite impulse response (FIR) for data transmission over band-limited channels. The filters are matched and satisfy a zero intersymbol interference constraint when cascaded. For baseband transmission, the filters achieve optimum spectral concentration in the frequency range [-(1+\beta )/2T, (1+\beta )/2T] . Mathematically, the filter design leads to a generalized eigenvalue problem which is solved numerically by a projected gradient Procedure. For transmission over bandpass channels by combined amplitude and phase modulation, the design technique is modified so that filters with complex-valued impulse response and optimum spectral concentration in the range of positive bandpass frequencies [f_{c} - (1+\beta )/2T, f_{c} + (1+\beta )/2T] are obtained. In addition, the complex formulation allows the design of impulse responses with enhanced spectral attenuation in the corresponding range of negative frequencies in order to minimize imageband interference. Results are shown in terms of filter coefficients, signal spectra, and spectral concentrations obtained. For example, filters designed for a voiceband data modem operating at a symbol rate of 2400 baud achieve a spectral concentration of 98.5 percent with 24 coefficients and \beta = 0.1 , and with only 0.001 percent of the total energy in the imageband region. View full abstract»

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  • Received Signal Level Measurements on a 160 km Line-of-Sight Radio Link

    Publication Year: 1982 , Page(s): 1963 - 1968
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    This paper discusses measurement of signals received over a 160-km (100-mi) line-of-sight microwave radio link operating at 8.4 GHz. Signals were recorded at both ends of the path at various times over a period of about 18 months. The effects of macroscale meteorological conditions are mentioned, particularly those which are peculiar to the central European location of the path. The data obtained from this measurement effort are presented both in terms of radio link availability, which includes the effects of diversity improvement, and in terms of long-term propagation performance, which considers only single receiver signal level variability. The data were also analyzed to obtain distributions of fade duration for single receivers and for both receivers in a diversity configuration. The study supports the idea that it is possible to achieve reliable propagation at 8 GHz on a link as long as 160 km, and with less than normal or conventional vertical diversity spacing. View full abstract»

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  • Computing the Blocking Probabilities for Spiderweb Channel Graphs

    Publication Year: 1982 , Page(s): 1916 - 1918
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    The problem of computing the blocking probabilities for spiderweb channel graphs is known to be difficult even under the simplifying Lee model. There have been only a few successful cases reported in the literature, all restricted to special types of four-stage channel graphs. In this paper we give an efficient method which computes the exact blocking probabilities (under the Lee model) for a large class of spiderweb channel graphs which are not restricted to four stages. 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