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Communications, IEEE Transactions on

Issue 7 • Date July 1981

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Displaying Results 1 - 25 of 26
  • [Front cover and table of contents]

    Publication Year: 1981 , Page(s): 0
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    Freely Available from IEEE
  • Correction to "A New Teletext Channel"

    Publication Year: 1981 , Page(s): 1074
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (108 KB)  

    First Page of the Article
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  • [Back cover]

    Publication Year: 1981 , Page(s): 0
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    Freely Available from IEEE
  • Do All MSK-Type Signaling Waveforms Have Wider Spectra Than Those for PSK?

    Publication Year: 1981 , Page(s): 1071 - 1072
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    For all MSK-type signals proposed until now, the main lobes of their power spectral densities were observed to be always wider than those for conventional PSK. Although it is intuitively believed that this observation can be extended to cover all other MSK-type signals not yet found, no formal proof has been reported yet. The present paper attempts to give such a proof. View full abstract»

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  • Design of Economic PCM Arrays with a Prescribed Grade of Service

    Publication Year: 1981 , Page(s): 925 - 935
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (976 KB)  

    This paper deals with the design of economically structured PCM switching arrays for traffic distribution. The presented switching arrays are symmetrically structured, and have one up to six stages and use different combinations of time stages T and space stages S , respectively. It is shown how such arrays can be designed for a required grade of service having a prescribed number of terminations and a prescribed carried traffic per time slot. Their relative costs per termination equal to that per time slot are calculated. These are costs for the gates and costs for memory bits, i.e., speech memories and all control memories. All presented PCM switching arrays are mapped into the corresponding space division multiplex (SDM) arrays. This allows a simple comparison with SDM link systems and an easy calculation of the point-to-point loss. The paper concludes comparing the traffic behavior and costs of the various PCM switching arrays. Finally, new "PCM charts" are developed as useful means for the design of economic PCM switching arrays. A second paper of this congress [14] compares traffic equivalent PCM and SDM switching arrays, respectively, with regard to their economic design, their traffic behavior, and their costs per termination. View full abstract»

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  • Digital Optical Receiver Sensitivity Degradation Caused by Crosstalk in Bidirectional Fiber Optic Systems

    Publication Year: 1981 , Page(s): 1012 - 1016
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    Receiver sensitivity degradation caused by Rayleigh backscattering and coupler reflections is investigated for bidirectional digital transmission systems. Experimental values for APD receiver sensitivity degradation in a system operating at a bit rate of 10 Mbits/s and at a wavelength of 830 nm were found to be within 2 to 3 dB (optical) of the values predicted by a simple theoretical model. View full abstract»

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  • Design Choices for Selective-Repeat Retransmission Protocols

    Publication Year: 1981 , Page(s): 944 - 953
    Cited by:  Papers (7)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1112 KB)  

    The design of selective-repeat retransmission protocols to provide reliable transfer of large data files is discussed. The transmission system is assumed capable of losing, distorting, or reordering the transmitted data frames and acknowledgment frames. The principle design considerations center on methods for managing the finite sequence number space and methods for managing the finite-sized receiver buffer. Under the assumption that there exists a maximum time from transmission of a frame to receipt of an acknowledgment for that frame, methods are described for safe reuse of frame sequence numbers. Previous results by Metzner and Morgan on buffer overflow control are extended to cover non-FIFO transmission systems. A two-dimensional space of design parameters is explored by way of Monte Carlo simulations. For appropriate designs, it is shown that significant increases in throughput over that achieved by the Go-Back- N protocol are possible on high-rate long-delay channels. View full abstract»

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  • An Orthogonally Multiplexed QAM System Using the Discrete Fourier Transform

    Publication Year: 1981 , Page(s): 982 - 989
    Cited by:  Papers (147)  |  Patents (95)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB)  

    An orthogonally multiplexed QAM (O-QAM) system is a multichannel system with a baud rate spacing between adjacent carrier frequencies; this property is desirable to digitally implement the system using the discrete Fourier transformation (DFT). This paper provides a novel digital signal processing method based on an N /2-point DFT processing in the O-QAM system. A complexity comparison between a digital O-QAM system and a digital singlechannel QAM system shows that the digital O-QAM system using the new method is more economical than the digitally implemented conventional single-channel data transmission system. View full abstract»

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  • Phasing Multitone Signals to Minimize Peak Factors

    Publication Year: 1981 , Page(s): 1072 - 1074
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    To maximize the average power of a multitone bandpass signal under a peak power constraint, the tones must be phased so as to minimize the RF peak factor. Results are given here for M = 3, 5, 7, and 9 where the M tones are of equal power and uniformly spaced in frequency. The two methods of phasing studied lead to similar minimized peak factors of roughly 6 dB. Optimum parameter values, improvements over worst case peak factors, and sensitivities to phasing errors are given, and extensions to other values of M are discussed. View full abstract»

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  • The Performance Characteristics of Two Extensions of the Sign Detector

    Publication Year: 1981 , Page(s): 1038 - 1044
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    Two related techniques have been proposed in the past for improving the performance of the sign detector through higherorder data quantization. The fixed-threshold m -interval detector and the generalized sign detector using a conditional test are both nonparametric detectors which are fairly simple to implement. In this paper we compare the asymptotic and finite-sample, finite-signal performance characteristics of these two detectors, and point out their relative advantages and disadvantages. View full abstract»

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  • Design of DPCM Quantizers for Video Signals Using Subjective Tests

    Publication Year: 1981 , Page(s): 990 - 1000
    Cited by:  Papers (22)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1472 KB)  

    The application of differential pulse code modulation (DPCM) for broadcast color television signals requires a design which produces no visible impairments under normal viewing conditions. This paper describes a quantizer design which is based on measured visibility thresholds of the various kinds of DPCM impairments such as granular noise, edge busyness, and slope overload. The visibility thresholds are determined by subjective tests based on comparisons of DPCM and PCM encoded pictures. Constructions of quantizers are carried out such that the number of levels is minimized without exceeding the measured visibility thresholds. Besides nonadaptive quantizers, adaptive quantizers are also constructed which are controlled by the signal changes of surrounding picture elements. These investigations show that for component coding of color video signals with two-dimensional prediction, a transmission rate of 31.7 Mbits/s is possible for natural types of test pictures without visible impairments using constant word length coding. View full abstract»

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  • Approximate FM Demodulation Using Zero Crossings

    Publication Year: 1981 , Page(s): 1061 - 1065
    Cited by:  Papers (4)  |  Patents (103)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    This paper deals with approximate methods for demodulating FM signals using their zero crossings. A first-order (linear) interpolation method is devised and analyzed. Computer programs were then prepared to compare this first-order interpolator to the more usual zero-order interpolator. Higher order interpolation is briefly discussed, and the results of using a second-order interpolator are compared to those using the lower order methods. View full abstract»

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  • A Statistical Analysis of ARQ Protocols Operating in a Nonindependent Error Environment

    Publication Year: 1981 , Page(s): 971 - 981
    Cited by:  Papers (35)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (880 KB)  

    In this paper the behavior of the Stop and Wait and Go Back- N error detection and retransmission (ARQ) protocols in an environment characterized by nonrandom errors are studied. Analytic models are developed for the case that the error process is modeled as a Markovian process. These models may be used to predict performance measures such as expected queue length and expected delay for the case of the Stop and Wait protocol and the Go Back- N protocol when N is very large. The models can also be used to determine maximum throughputs for both protocols. The results of these models are compared with simulation results for the Selective Repeat ARQ protocol. View full abstract»

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  • An Incremental Adaptive Quantizer: A Novel Quantization Scheme

    Publication Year: 1981 , Page(s): 1056 - 1061
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    Adaptive quantizers for PCM and DPCM coding of speech have been of great interest, and several excellent quantization strategies have evolved [1], [2]. In this paper we propose another algorithm for the step-size change in a quantizer. In the present strategy the quantizer is always a linear one except for the fact that the step size can be changed by a fixed amount at each sampling instant. This fixed value is also the minimum allowed step size. Hence, we have the name incremental adaptive quantizer. The quantizer has been simulated on a computer and its performance has been compared with that of Jayant's adaptive quantizer (JAQ), both in PCM and DPCM coders. The figure of merit used in the comparison is the signal-to-noise ratio (SNR) with a correlated sequence as the input. The preliminary results indicate that the new design can perform very well. However, it has the drawback of not being able to respond to very fast changes in the input. It can be easily realized in an integrated form using ROM's. View full abstract»

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  • On the Accuracy of the Shimbo Approach to Intermodulation and Crosstalk Calculations

    Publication Year: 1981 , Page(s): 1076 - 1082
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    To simplify the mathematics involved and to facilitate derivations of intermodulation and crosstalk formulas, the Shimbo approach uses a double Fourier transformation and represents the characteristics of a memoryless nonlinear device by a Bessel function series. Such an approach seems to be a very brave approximation as the approximated characteristics vary wildly with respect to the number of Bessel function terms L and with the amount of actual characteristic data used (A_{F}) . However, it is shown here that the approach works well for the case involving two carriers with equal constant amplitudes, provided that one chooses L and AFproperly. View full abstract»

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  • Erlang and Normal Distribution in Telex Traffic

    Publication Year: 1981 , Page(s): 1036 - 1038
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    ESS exchanges provide the means of exact accurate measurements of telecommunication traffic. The results of these measurements prove the validity of certain theoretical propositions. Therefore, it is possible to base the short- and long-range planning of network growth, adjusted for time and place, on the conclusions obtained. View full abstract»

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  • Anti-Intercept Margins of Relay-Augmented Data Links

    Publication Year: 1981 , Page(s): 936 - 943
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    A quantitative measure of the anti-intercept improvement (or margin) of a relay data net is described. It is assumed that the link relays are located to obtain the maximum anti-jam advantage against a line-of-sight jammer. The anti-intercept margin is defined as the ratio of the respective spatial power densities available to the intercept receiver when no relay and relays are used, and can be as large as 10-20 dB. It is shown that the relay anti-intercept (AI) margin for a spatially uniform jamming field intensity is lower than for a single jammer environment, and requires the same form of relay spacing needed to maximize the AI margin in the absence of jamming. It is also shown that operation in a lossy medium offers an opportunity for enhancing anti-intercept capability. A measure of overall AI performance that illustrates this enhancement is discussed. View full abstract»

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  • A New Demodulation Method Improving FM System Interference Immunity

    Publication Year: 1981 , Page(s): 1001 - 1011
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (944 KB)  

    As a result of investigation of interference into FM systems, a new algorithm for the process of demodulation is proposed. When compared to the method using the conventional limiter-discriminator, it offers better immunity against the baseband interference noise. Desired signal processing is performed by the functional devices added to the conventional limiter-discriminator in such a way that this new demodulator can be optimized in the sense of the minimum baseband interference noise. The statistics of the wanted and interfering signals must be known. Several examples involving interference problems in FDM-FM radio-relay systems carrying multichannel telephone signals are elaborated to illustrate the performances of the proposed demodulator. FDM-FM, PSK, or FSK systems are considered the cause of the interference. The noise power ratio (NPR) at the output of the conventional limiter-discriminator and the improvement factor offered by the new demodulator, obtained on digital computer, are presented versus baseband frequency in the form of diagrams. Different IF filters in FDM-FM receiver and transmit filters in the interfering systems are taken into account. The improvement offered by the proposed demodulator is of such a degree that some of the important restrictions in planning different radio systems could be relaxed. View full abstract»

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  • A Quick-Look Decoder with Isolated Error Correction and Node Synchronization

    Publication Year: 1981 , Page(s): 1074 - 1076
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    In a low-noise environment, a simple inversion circuit can be used for quick-look decoding of a convolutional code. The bit error performance of the raw inversion circuit is improved by a simple pattern-recognition technique operating on the syndrome stream, which is also used to acquire node sync. View full abstract»

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  • GMSK Modulation for Digital Mobile Radio Telephony

    Publication Year: 1981 , Page(s): 1044 - 1050
    Cited by:  Papers (333)  |  Patents (56)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (800 KB)  

    This paper is concerned with digital modulation for future mobile radio telephone services. First, the specific requirements on the digital modulation for mobile radio use are described. Then, premodulation Gaussian filtered minimum shift keying (GMSK) with coherent detection is proposed as an effective digital modulation for the present purpose, and its fundamental properties are clarified with the aid of machine computation. The constitution of modulator and demodulator is then discussed from the viewpoints of mobile radio applications. The superiority of this modulation is supported by some experimental test results. View full abstract»

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  • Optimum Allocation of Servers to Two Types of Competing Customers

    Publication Year: 1981 , Page(s): 1051 - 1055
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    We consider the problem of optimal dynamic allocation of a limited number of processors to service the demands from different types of users. The types are differentiated by the rates at which they enter requests for service and the mean length of time they occupy a single processor. The decision to accept or reject a request for service may be based on the number of processors occupied by each type. Throughput, or utilization of processors, weighted differently for each type may be used as a performance measure. While the optimum allocation question is formulated for any finite number of customer types, our solution is limited to the case of two competing customer classes. For two types of users we show that among a large class of policies, the optimum is the easily implemented policy of restricting the maximum number of processors that one of the two types can occupy at any time. The requests from the other type are always honored as long as a processor is available for service. It is intuitively reasonable that, despite the complex interactivity permitted in some policies and the multidimensional characterization of a customer type, one of the customer types should have a relative advantage and be permitted open access while a hard limitation is enforced on the competition. The crux of the proof involves a policy space perturbation argument relying on the structure of the equilibrium density. View full abstract»

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  • Bottleneck Flow Control

    Publication Year: 1981 , Page(s): 954 - 962
    Cited by:  Papers (143)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1000 KB)  

    The problem of optimally choosing message rates for users of a store-and-forward network is analyzed. Multiple users sharing the links of the network each attempt to adjust their message rates to achieve an ideal network operating point or an "ideal tradeoff point between high throughput and low delay." Each user has a fixed path or virtual circuit. In this environment, a basic definition of "ideal delay-throughput tradeoff" is given and motivated. This definition concentrates on a fair allocation of network resources at network bottlenecks. This "ideal policy" is implemented via a decentralized algorithm that achieves the unique set of optimal throughputs. All sharers constrained by the same bottleneck are treated fairly by being assigned equal throughputs. A generalized definition of ideal tradeoff is then introduced to provide more flexibility in the choice of message rates. With this definition, the network may accommodate users with different types of message traffic. A transformation technique reduces the problem of optimizing this performance measure to the problem of optimizing the basic measure. View full abstract»

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  • Speckle Noise Reduction in Fiber Optic Analog Video Transmission Using Semiconductor Laser Diodes

    Publication Year: 1981 , Page(s): 1017 - 1024
    Cited by:  Papers (27)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    This paper investigates the effects of speckle noise on analog video transmission systems using semiconductor laser diodes. The system linearity degradation due to speckle noise is examined using different fiber types. Then this paper proposes a new modulation technique employing a superimposed pulse scheme to reduce speckle noise. It is experimentally confirmed that the proposed modulation method is effective in reducing speckle noise. Based on the above investigations, analog video transmission experiments are performed using single-mode fibers, step-index multimode fibers, and graded-index multimode fibers in the 0.8 and 1.3 μm wavelength regions. The results of the transmission tests have confirmed the feasibility of analog video transmission using semiconductor laser diodes. View full abstract»

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  • A General Multibeam Satellite Switching Algorithm

    Publication Year: 1981 , Page(s): 1025 - 1036
    Cited by:  Papers (37)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (968 KB)  

    In this paper we consider an SS/TDMA system with M uplink beams, N downlink beams, and K connection points. We first assume that the downlink is α times faster than the uplink, and a simple time multiplexing scheme is employed. An optimal time slot assignment algorithm for any M, N,\alpha , and K , 1 \leq K \leq \min (M, \alpha N) , and for any traffic matrix is presented, where optimality means achieving the minimal possible total transmission time for the given traffic matrix. The number of switching matrices generated by the algorithm never exceeds MN + K\alpha + 1 . Extensive simulation results on randomly generated matrices are carried out, showing that the average number of switching matrices generated is substantially lower than the upper bound. The case when the uplink is faster than the downlink is also considered. View full abstract»

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  • Tolerable Q-Factor Variations in PCM Lines

    Publication Year: 1981 , Page(s): 1066 - 1070
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    This paper makes a theoretical assessment of the performance impairments that may be caused on PCM lines by the use of different timing extraction bandwidths in tandem. Two basic situations are examined: 1) random transmitted pattern, and 2) transition between two repetitive patterns. In both cases, the analysis of jitter propagation and acceptance indicates that there is a limited degree of bandwidth inconsistency that may be tolerated. The amount of tolerable inconsistency is derived in both cases, according to different criteria that are established for convenience in each case. The effect of systematic line jitter on the correlation between a repeater performance in the field and in bench tests is also discussed. The study is based on a well-known model of jitter propagation introduced by Byrne et al. [1]. The general conclusion of the paper is that Q -factor variations in a PCM line should be kept lower than a factor of two in order to avoid errors during pattern transitions and lower than 1.5 in order to avoid noise immunity loss. 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