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Communication Technology, IEEE Transactions on

Issue 4 • Date August 1970

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Displaying Results 1 - 24 of 24
  • [Front cover and table of contents]

    Publication Year: 1970 , Page(s): 0
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    Freely Available from IEEE
  • Remote Control of Permanent Memory Writing Apparatus Using Data Transmission Over Telephone Lines

    Publication Year: 1970 , Page(s): 271 - 275
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    Development of the No. 1 Electronic Switching System, a stored program system, by Bell Telephone Laboratories has required considerable program debugging and system testing. The bulk of this effort is done in model telephone offices at the Bell Telephone Laboratories locations in Illinois and New Jersey. However, for some actual telephone offices that are the first of a kind, incorporating Hew program or hardware features, system testing is done at the office itself. To facilitate this remote testing, a means of providing an up-to-date copy of the program at the test site had to be provided. This paper describes a means for meeting this need by use of data transmission over telephone lines. The system uses unique terminal units to provide compatibility between magnetic tape units at laboratory locations and memory writing equipment at the test site. Transmission of error check bits with the data and retransmission of data to correct detected transmission errors is provided. View full abstract»

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  • A Universal Threshold Extending Frequency-Modulated Feedback Demodulator

    Publication Year: 1970 , Page(s): 276 - 280
    Cited by:  Patents (1)
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    The results of a program to design, develop, and build a threshold extending frequency-modulated feedback (FMFB) demodulator which can be used as a universal demodulator is discussed. Its design details are described, as well as the method whereby its loop gain and frequency characteristics are changed. Both the methods by which it was tested and also the test results are described. Comparisons of test results and theoretical limits are described. View full abstract»

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  • Effective Application of Forward-Acting Error-Control Coding to Multichannel HF Data Modems

    Publication Year: 1970 , Page(s): 281 - 294
    Cited by:  Papers (4)  |  Patents (16)
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    The results of a recent study to determine and evaluate effective methods of applying forward-acting error-control-coding techniques to multichannel high-frequency (HF) data modems are presented. A unique feature of this study is a conscious exploitation of the fine-grain bit-error behavior, both in time and in frequency, that is characteristic of multichannel HF data transmission systems. Attention is focused on the ability of four promising coding techniques to combat the characteristic error behavior. These techniques involve the use of bit-interleaved binary block codes, diffuse convolutional codes, block-interleaved two-stage concatenated codes with binary-coded inner stages and nonbinary-coded outer stages, and a class of two-stage binary codes with random-error-correcting inner stages and burst-error correcting outer stages. View full abstract»

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  • Carrier Transmission of Binary Data in a Restricted Band

    Publication Year: 1970 , Page(s): 295 - 304
    Cited by:  Papers (74)
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    The spectra of digital frequency modulation (FM) signals have been observed to be narrow compared with the spectra of digital baseband signals or the corresponding amplitude modulation (AM) and phase modulation (PM) signals. This suggests a high efficiency of transmission in terms of occupied bandwidth for binary FM. Here the desirability of digital FM systems is investigated further with an examination of the probability of bit error. The FM receiver considered consists of a predetection filter, a limiter-discriminator, and a postdetection filter. New results are presented on the effect of predetection bandwidth restriction on the error performance of binary FM systems for various frequency deviations. Theoretical results have been obtained by a Fourier analysis of the distorted FM signals and by Rice's click analysis of FM noise. The data presented permits an optimum selection of system parameters such as frequency deviation ratio and predetection filter bandwidth. It is found that in narrow-band operation a peak-to-peak frequency deviation of about 0.7 times the bit rate and a bandpass filter bandwidth of about 1.0 times the bit rate yield a minimum probability of error. Experimental measurements have been made and there is, in general, good agreement with the theory. A comparison of the error performance of noncoherent binary FM, coherent AM, and coherent PM in a restricted band is made. Narrow-band noncoherent FM proves superior to AM in any bandwidth. In narrow-band operation, the noncoherent FM gives a somewhat better error performance than the coherent PM. For example, for an error rate of 10-4and a bandpass filter bandwidth of one times the bit rate, the performance of a noncoherent FM system is 0.7 dB better than that of a coherent PM system. View full abstract»

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  • A New Digital Frequency Detection Scheme

    Publication Year: 1970 , Page(s): 305 - 313
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    A new digital frequency detector for discriminating between the location of a noisy sinusoidal signal in one of two frequency bands is presented. Lower performance bounds of the detector are obtained. It is shown that the detector can discriminate between any two frequencies in a wide frequency band, and that these two frequencies can be arbitrarily close. Furthermore, correct decisions will be made in the presence of interference if maximum displacement of the zero crossings of the received signal due to interference satisfy certain loose bounds. For instance, correct decisions can be made even if there exists a spurious tone interference whose frequency and magnitude are close to those of the information signal. It is also shown that the peak of the impulse noises considered can be close to the peak of the information signal without causing a decision error. The detector can be easily implemented with a small number of standard digital circuits. It operates automatically and nonparametrically without requiring a priori knowledge of the statistics of the signal and interference. View full abstract»

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  • Angle-Modulation Power Spectra

    Publication Year: 1970 , Page(s): 313 - 318
    Cited by:  Papers (1)
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    Exact expressions are obtained for the autocorrelation function of a sinusoidal carrier phase- or frequency-modulated by Butterworth-filtered white Gaussian noise. The corresponding power spectra are obtained numerically, together with bounds on the error resulting from truncation of the Fourier integrals. The spectra are relatively inaccurate in the tail regions, where other methods of calculation are more appropriate. The results are compared with estimates based on Woodward's approximation, and it is concluded that, while the latter are valuable for frequency modulation under a wide range of conditions, their usefulness for phase modulation is limited to wide-deviation modulation by high-order spectra. View full abstract»

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  • Wide-Band Detection of FSK Transmissions in a Three-Component-Two-Path Channel

    Publication Year: 1970 , Page(s): 319 - 332
    Cited by:  Papers (3)
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    The multipath model evaluated is of a three-component-two-path type. In several space channels we have a directtransmission path and a reflected-transmission path. The direct component can be described as specular, while the reflection is a composition of both a specular component and one that is diffuse. The channel bit error probability for noncoherent wide-band frequency-shift keying (FSK) is obtained for such channels. It is shown that parameters such as rate of fade, Doppler, and data rate relative to the delay between the two transmission paths affects the system performance significantly. View full abstract»

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  • Transmission of MFSK Signals in Several Frequency Uncertain Channels

    Publication Year: 1970 , Page(s): 333 - 338
    Cited by:  Papers (1)
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    The performance metric (symbol error rate) of the optimum in-the-limit receivers for the detection of a frequency uncertain M -ary frequency shift-keyed (MFSK) transmission in additive Gaussian noise is derived. By in-the-limit, we mean the limiting cases of high and low signal-to-noise ratio (SNR). The performance of the two receivers are compared for some special cases. The MFSK wide-band receiving (optimum low SNR receiver for the channel Just described) symbol error rate in a three component-two-path channel is derived when the delay between the direct path and reflected path compared with the data rate is very small. View full abstract»

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  • Sequential Block Orthogonal Signaling with Two Noiseless Decision Feedbacks

    Publication Year: 1970 , Page(s): 339 - 344
    Cited by:  Papers (8)
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    A sequential block orthogonal signaling scheme with both an intermittent and a final decision feedback is developed. The reliability function for this communication technique is shown to be bounded below by \alpha _{\max } \bar{C} - R , for 0 \leq R < \bar{C} where αmaxis one-half of the ratio of the maximum transmitted signal average power Ppmaxto the expected transmitted signal average power \bar{P} . The transmitter power advantage of this feedback scheme in a nonasymptotic operational mode is also presented. View full abstract»

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  • Coherency for the Binary Symmetric Channel

    Publication Year: 1970 , Page(s): 344 - 352
    Cited by:  Papers (1)
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    For the purpose of communication system planning, predictions of system performance based upon models of an ideal coherent channel are extensively used. Previous work has demonstrated the deleterious effects of radio frequency (RF) phase error on channel performance by machine computation of an integral derived by statistically averaging over the phase error. The required receiver performance in estimating the RF phase for detecting binary coherent signals is further examined. Upper and lower bounds are generated which measure the inaccuracy of the familiar performance formula derived from the idealized coherent channel model. The bounds are obtained analytically without resorting to machine computation. The Tikhonov probability distribution for the RF reference phase error is used. The principal result is the relation \sigma _{\varpi }^{2} \leq (kE/N_{0})^{-1} where \sigma _{\varpi }^{2} is the variance in the error of the derived carrier phase, E/N_{0} is the energy (per uncoded symbol) to noise density ratio required by the ideal coherent channel, and k is a factor relating to the tolerable degradation in error rate as given by the bounds. If k is on the order of 3 the symbol error rate no more than doubles; in general a k of 10 will suffice for no degradation in error rate. View full abstract»

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  • Carrier Acquisition for Coherent Demodulation of Pulse-Amplitude Modulation

    Publication Year: 1970 , Page(s): 353 - 360
    Cited by:  Papers (1)
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    Phase recovery in vestigial sideband (VSB) data transmission is discussed. Examining a particular aspect of this broad area, attention is focused on the time required to recover carrier phase in order to achieve a satisfactory error rate. We derive the acquisition time for simple models. Our results are exhibited graphically, relating pertinent system parameters. These results indicate that while in double sideband transmission the acquisition time required to achieve a satisfactory error rate is of the order of a few symbol intervals, in VSB transmission this time grows to tens and hundreds of symbol intervals. View full abstract»

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  • Electronic Color Separation with Laser Light Sources

    Publication Year: 1970 , Page(s): 361 - 366
    Cited by:  Patents (1)
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    Improvements in electronic color scanners appear possible by replacing current light sources with coherent radiation from lasers with much higher radiance. This allows higher speeds of operation (subject to mechanical constraints), greater enlargement capability, and the use of lower sensitivity recording films, or other media. These possibilities were verified experimentally by replacing the reading light source in an RCA color scanner by a combination of argon-ion and He-Ne lasers and the writing light source with an argon-ion laser. The light intensity of the writing light source was modulated by an electrooptic modulator driven from the signal output of the color-correction computer. When this signal was pulsed electronically, it was further possible to directly generate a screened halftone image on the scanner. This is due to the fact that a laser can be operated with a Gaussian spatial energy density distribution. When such a distribution is focused onto a high gamma film, dots are produced whose size is related uniquely to the intensity of the light pulse. View full abstract»

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  • The Digital Echo Modulation

    Publication Year: 1970 , Page(s): 367 - 376
    Cited by:  Papers (4)  |  Patents (6)
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    A new technique for the transmission of binary data over band-limited channels is described. The signaling method is a generalization of Nyquist's telegraph theory, it allows pulse modulation without intersymbol interference within a frequency spectrum centered at any multiple of one quarter of the signaling rate. The signals are derived from pulse trains generated by a combination of logic circuits and weighting resistors. The number of pulses constituting a signal element varies typically from 5 to 9 in function of the desired total bandwidth. Signaling at 80 percent of the Nyquist rate has been easily achieved with 40-dB out-of-band attenuation. The digital echo modulation eliminates the need for precise analog filters and minimizes the effects of component instability; in addition, it gives a great flexibility to the design, allowing special features such as efficient half-speed operation. View full abstract»

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  • Adaptive Equalizer for Pulse Transmission

    Publication Year: 1970 , Page(s): 377 - 395
    Cited by:  Papers (18)  |  Patents (1)
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    Results are reported which are of interest in the automatic adaptive equalization of telephone lines or other narrowbandwidth channels where data transmission is limited primarily by intersymbol interference. We describe an algorithm for adjusting the tap gains of a tapped delay line (TDL) equalizer which converges for all channels to the setting, which minimizes the mean-square error (rose) at the filter output due to both noise and intersymbol interference. This algorithm has been implemented using digital microcircuits and metal-oxide semiconductor (MOS) shift registers to construct a 63 tap all-digital TDL filter covering 19.7 ms. The modulation system used is vestigal sideband with bandwidth 1.6 kHz. The data rate is 3200 pulses/s, or 9600 bit/s with 8 data levels. A description of the hardware realization and performance data over various telephone lines is given. View full abstract»

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  • Atmosphere Propagation and Communication Channel Model for Laser Wavelengths

    Publication Year: 1970 , Page(s): 396 - 416
    Cited by:  Papers (18)  |  Patents (1)
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    The advent of the laser has generated much interest in its use for communication. Consideration is given in this paper to obtaining a communication channel model of the atmosphere for laser frequencies. For this purpose a fairly exhaustive, tutorial, and partly critical review of a major part of the extensive literature pertaining to theoretical and experimental results on the propagation of laser signals in the atmosphere is given. Some of the basic characteristics of the channel for Which detailed results are given are 1) channel time spread (or, equivalently, channel coherence bandwidth) due to multipathing and dispersion, 2) channel gain, 3) channel doppler spread and coherence time, 4) channel spatial coherence and amplitude covariance functions. Consideration is given to both point receivers and area receivers, heterodyne and direct detection receivers, nonplanar (i.e., spherical and beam) wave propagation, and infinite plane-wave propagation. The results are given for clear weather conditions. Brief attention is given to additive noise. In reviewing the extensive literature dealing with the propagation of optical signals through a turbulent medium, an attempt is made to put this varied, diverse, and in some instances controversial material into proper perspective; to note where theoretical results derived for one set of conditions were applied to experimental results obtained for another set of conditions; to correct some invalid conclusions drawn from some theoretical results as far as signal degradation effects and parameter variations; and to indicate where out-of-date vertical profile models were used with updated models being given, and where possible the new theoretical predictions based on these models provided. The paper should, as a result, be of help to those familiar with the literature as Well as those who are not. For those not acquainted with the literature, in addition to providing a fairly in-depth knowledge of the characteristics of propagati- on through a turbulent medium and an indication of the status of our understanding of this subject, the paper should provide a stepping stone for obtaining a more thorough understanding of the subject and for doing work in the field. View full abstract»

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  • Level Crossing Rates of an Equal-Gain Predetection Diversity Combiner

    Publication Year: 1970 , Page(s): 417 - 426
    Cited by:  Papers (14)
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    An M branch equal-gain predetection space-diversity combiner is analyzed for the case where the signals received from the individual branches of such a combiner are partially correlated. The level crossing rate (LCR) of the combined signal envelope equals the probability density function times a function of the direction of motion. When a linear antenna array is used on a mobile radio receiver, the direction of motion does not affect the shape of the LCR curve of the combined signal but does affect the absolute values, especially when the antenna spacing d is less than 0.5 λ. There is apparently no effect for d > 1 \lambda View full abstract»

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  • PSK Demodulator with Delay Line for the PCM-TDMA System

    Publication Year: 1970 , Page(s): 427 - 434
    Cited by:  Papers (6)  |  Patents (2)
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    In the pulse-code modulation-time-division-multipleaccess (PCM-TDMA) system for the next global satellite communications, minimization of synchronization bits in each burst is desirable to improve the traffic efficiency. A new phaseshift keyed (PSK) demodulating system with a delay line is proposed to meet the previous requirement, and the design of its scheme and its experimental performance are described. The difference of the error rate performance between theoretical and experimental values was about 0.8 dB, and even in the worst case the error rate of 10-4was assured for an input E/N_{0} of 10.5 dB. View full abstract»

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  • A Digital Channel Vocoder

    Publication Year: 1970 , Page(s): 435 - 442
    Cited by:  Papers (3)  |  Patents (2)
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    An all digital realization of a channel vocoder is described, including both computational algorithms and hardware structures. The machine, constructed almost entirely of digital elements, operates at a 2400 bit/s rate and produces synthetic speech, whose intelligibility and speaker recognition properties are comparable to those of an average telephone line. The extensive use of integrated digital circuitry allows size and cost reductions that are not currently possible in conventional high-quality analog vocoder systems. View full abstract»

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  • The Effects of Self-Noise on Error Voltage of the Delay-Lock Discriminator

    Publication Year: 1970 , Page(s): 443 - 447
    Cited by:  Papers (2)
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    This paper deals with the effects of the correlation self-noise on the error voltage of a radio frequency (RF) delaylock discriminator. The error voltage at the output of the envelope correlation network is determined in terms of the spectral components of the maximal-length sequence and the frequency response of the bandpass filters used in the two channels of the correlation network. The slope of the error voltage in the lock-on state, which is readily obtained from the above analysis, is a quantity of particular interest, because the mean-square tracking error is inversely proportional to the square of the slope. The problem of the mismatch in the two channels of the correlation network is also considered. View full abstract»

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  • Evalution of the Effects of Notch Filters on Digital Data Transmission

    Publication Year: 1970 , Page(s): 447 - 449
    Cited by:  Patents (10)
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    The performance impairment resulting from the insertion of a narrow-band rejection filter (notch filter) in a data transmission channel is evaluated. To isolate the effects of notch filtering, it is assumed that, before inserting the notch filter, the data signal is an idealized pulse amplitude modulation (PAM) signal using a pulse shape which produces no intersymbol interference (Nyquist pulse). The intersymbol interference resulting from the notch is examined in terms of 1) its maximum value and 2) its mean-squared value. It is shown that the maximum interference criterion is inappropriate; since it will always exceed the signal pulse amplitude regardless of the shape or rejection bandwidth of the notch filter (a notch always closes the binary eye pattern). The mean-squared interference is easily evaluated in terms of the notch characteristic, and furthermore, this quantity leads to a simple means for predicting the tolerable notch bandwidth for maintaining a specified error performance with additive Gaussian noise. The mean-squared interference for some simple notch filter realizations is presented. View full abstract»

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  • On the Equivalence in Performance of Several Phase-Locked Loop Configurations

    Publication Year: 1970 , Page(s): 449 - 452
    Cited by:  Papers (1)
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    A double-superheterodyne tracking loop using two frequency converters to provide coherent reference signals for demodulation is analyzed and compared to two other well-known configurations. It is shown that if the loop parameters are defined appropriately, then the dynamic noise performance of the loop is identically equivalent to that of a standard phase-locked loop or a double-superheterodyne tracking loop using a noise-free external reference generator. View full abstract»

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  • Transient Behavior of a Phase-Locked Loop in the Presence of Noise

    Publication Year: 1970 , Page(s): 452 - 456
    Cited by:  Papers (5)
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    Transient behavior of the first-order phase-locked loop in the presence of noise is investigated. Numerical integration is used to obtain solutions for the Fokker-Planck equation which represents loop dynamics, Results illustrate quantitative behavior of the time-varying probability density function of phase error when the input is a constant frequency sinusoid in the presence of additive white Gaussian noise. Several selected values of signal-to-noise ratio (SNR) are considered. View full abstract»

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  • [Back cover]

    Publication Year: 1970 , Page(s): 0
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    Freely Available from IEEE

Aims & Scope

This Transactions ceased publication in 1971. The current retitled publication is  IEEE Transactions on Communications.

Full Aims & Scope