By Topic

Communications Systems, IRE Transactions on

Issue 2 • Date June 1962

Filter Results

Displaying Results 1 - 16 of 16
  • [Front cover and table of contents]

    Page(s): 0
    Save to Project icon | Request Permissions | PDF file iconPDF (129 KB)  
    Freely Available from IEEE
  • The Process of Communication System Design

    Page(s): 151 - 153
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (187 KB)  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Techniques for Incoherent Scatter Communication

    Page(s): 154 - 160
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    Special radiometric-detection procedures are appropriate when communication signals are severely distorted by a rapidly fluctuating, noisy, time-dispersive channel. This paper presents a performance analysis of some digital communication techniques that can be used when most other techniques fail. Error-probability expressions are derived and evaluated for a wide range of possible operating conditions. Effective use of available signal power is found to be possible on badly behaved channels, provided there is sufficient bandwidth available for the optimization of performance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Influence of Fading Spectrum on the Binary Error Probabilites of Incoherent and Differentially Coherent Matched Filter Recievers

    Page(s): 160 - 168
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (820 KB)  

    Previous derivations of the influence of fading on the error probabilities of binary data transmission systems have assumed that the fading rate is so slow that fluctuations within a bit may be ignored. This slow fading assumption is removed in the present paper which derives general expressions for the binary error probabilities of incoherent and differentially coherent matched filter receivers employing post-detection diversity combining. In the analysis it is assumed that the transmitted signals occupy a bandwidth much smaller than the coherence bandwidth of the medium so that "flat" fading may be assumed. In addition, it is assumed that the amplitude and phase fluctuations produced by the medium have the same statistical character as those of narrow-band Gaussian noise. The general analytical results are specialized to the cases of frequency shift keying using incoherent detection, and phase shift keying using differentially coherent detection, and to the cases of exponential and Gaussian fading correlation functions. For these special cases, signal-to-noise degradation curves are given as a function of fading bandwidth. The PSK system is degraded more rapidly with increasing fading bandwidth than is the FSK system. Curves are given which show the error probabilities and corresponding fading bandwidths for which the noncoherent FSK and the differentially coherent PSK systems break even. For lower error probabilities or higher fading bandwidths, the FSK system becomes superior to the PSK system in the sense of being able to provide the same error probability with less signal-to-noise ratio. The existence of an irreducible error probability is demonstrated for the incoherent and differentially coherent matched filter receivers. Thus, in general, an increase in transmitted signal power cannot reduce the error probability below a certain value depending upon the fading spectrum and order of diversity. Theoretical curves of irreducible error probability are given for- the incoherent FSK and differentially coherent PSK systems. An important result of the analysis is that the shape of the fading spectrum can make a significant difference in the amount of signal-to-noise degradation. The results of the analysis also indicate that care must be exercised in employing a "slow fading" assumption since, if low bit error probabilities are desired, significant degradations in performance can occur even though the fading rate is quite low relative to the data rate. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Comparative Performance of Digital Data Transmission Systems in the Presence of CW Interference

    Page(s): 169 - 177
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (911 KB)  

    During the last decade there has been a considerable amount of work done on the analysis of digital data transmissions in an interference environment. With few exceptions, the type of additive interference considered is normal noise. This paper treats the case where the interference consists of CW that falls within the pass band of the receiver. The results obtained can also be utilized to ascertain system performance in the presence of interference from similar systems and for certain classes of interrupted CW (ICW) interference. The performance of differential phase-shift, coherent phase-shift, amplitude-keyed, frequency-shift and time-shift binary digital data transmissions is determined. The average digit error probability is taken as the measure of system performance. The element of uncertainty involved in the CW interference analysis is due to random variation in the phase angle between the signal and interference. The performance of systems employing angle modulation is found to be independent of this phase angle for certain values of the interference frequency. In general, it is shown that the digit error probability varies as the arc cosine of a function of the signalto-interference ratio, the function being dependent on the system under consideration. It is shown that, of the systems investigated, coherent phaseshift keying is the best transmission technique in the face of CW interference. The digit error probability in a differential phaseshift-keyed transmission is found to be a sensitive function of the frequency of the interfering tone, and depending on this frequency, can be quite different from that obtained in a coherent phase-shiftkeyed transmission. Frequency-shift keying is found to exhibit the lowest threshold of the noncoherent systems considered, while time-shift keying is found to give an improvement of approximately 4 db over a simple amplitude-keyed system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Theoretical Diversity Improvement in Multiple Frequency Shift Keying

    Page(s): 177 - 184
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    Multiple frequency shift keying (MFSK) is a modulation suitable for transmitting digital data under fading conditions. A quantitative analysis of MFSK-with-diversity is presented. The MFSK signals on the several diversity channels are presumed to be perturbed independently by Rayleigh fading and additive white Gaussian noise. Also, it is assumed that fading is slow and that envelope, cross-correlation (matched filter) detection is used. The diversity combining method is chosen so that the receiver performs a likelihood-ratio test in deciding which one of K frequencies was transmitted. This optimum comibining method is to square and add the detected outputs of corresponding filters from each diversity channel. Theoretical error probability as a function of signal-energy-per-bit received is derived, and curves are plotted for two-, four-, and eight-frequency MFSK-with-diversity. Bandwidth requirements, as a function of type and order of diversity, are determined. Eight-frequency MFSK with triple diversity has a 21.8-db advantage over simple FSK for transmitting 6-bit characters with a 0.001 error probability. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the Optimum Performance of N-ary Systems Having Two Degrees of Freedom

    Page(s): 185 - 192
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (649 KB)  

    A digital transmission system with n possible transmitted symbols is considered. If the time between transmitted symbols is T0seconds and the bandwidth is W , the n possible symbols correspond to n vectors in a 2WT_{0} dimensional signal space. This paper considers the theoretical properties of a class of digital systems where the signal space is two-dimensional. Such systems are both amplitude-and phase-modulated. Approximate expressions are derived for the average probability of error for these systems as a function of the placement of the n symbol vectors in the twodimensional signal space. Optimum placements are then given which minimize this probability of error for a given average or peak power SNR constraint. It is shown that the optimum channel structure is a function of the alphabet size n , and the type of power constraint, as well as the SNR. In general the optimum system is a phase-modulated system for low SNR's and for alphabet sizes n \leq 16 in the high SNR region. The performance of this optimum system in terms of channel capacity and probability of error is then compared with the performance of one-dimensional systems, AM-only and PM-only, in a complete set of curves for both peak and average power. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • TV Broadcast from Earth Satellite

    Page(s): 193 - 201
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (803 KB)  

    This paper considers the need for and the feasibility of direct continental TV broadcast to conventional home receivers from an orbiting stationary satellite. Among the factors considered are time and language differences of the potential audience, the lack of suitable programming material, and frequency allocation problems. Required transmitter and primary power have been calculated for several coverage situations on both a VHF and a UHF channel. These powers are significantly above previous estimates published elsewhere, and above the power capability of even the proposed SNAP 8, 60-kw nuclear reactor except for coverage of limited areas on the ground. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • AFC for Frequency Hopping Systems

    Page(s): 202 - 208
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    An AFC system has been developed for stabilizing the frequency of a voltage-tunable oscillator near any one of many discrete frequencies. A delay line takes the place of the conventional cavity in the discriminator. The discrete steps correspond to the electrical length of the delay line, e.g., 2 Mc in the S-band system reported herein. Slow frequency fluctuations inherent in the oscillator are reduced; a stabilization factor of 100 has been achieved in a system for jumping frequency rapidly by stepping the tuning voltage. The nature of the hysteresis loops and means for their reduction are discussed. The system is significant for improving the stability and the spectrum of wide-band tunable oscillators as used in frequency hopping apparatus. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Carrier-Operated Echo Suppressor and Control Device

    Page(s): 208 - 214
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    Of the numerous distortions affecting high quality facsimile reception, noise and echo represent the most troublesome offenders. This paper describes a device which fills the critical need for suppression of noise and echo currents on two-way multipoint facsimile networks. Laboratory test data as well as operational performance results, gathered during field trials of two prototype units, are presented. Additional applications for the device, including TONLOC, disabling of compandors during picture transmission, and possible application to data transmission systems are discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Recovery of Randomly Sampled Time Sequences

    Page(s): 214 - 216
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (329 KB)  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On Comparing N-ary Systems

    Page(s): 216 - 217
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (253 KB)  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • [Back cover]

    Page(s): 0
    Save to Project icon | Request Permissions | PDF file iconPDF (428 KB)  
    Freely Available from IEEE

Aims & Scope

This Transactions ceased publication in 1962. The current retitled publication is  IEEE Transactions on Communications.

Full Aims & Scope