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Communications, IEEE Transactions on

Issue 9 • Date Sep 1989

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Displaying Results 1 - 14 of 14
  • An algorithmic procedure for checking safety properties of protocols

    Publication Year: 1989 , Page(s): 940 - 948
    Cited by:  Papers (14)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (924 KB)  

    A procedure for checking safety properties of communication protocols is presented. A protocol is specified as a collection of communicating finite-state machines (FSMs). Two novel algorithms used in this procedure are described. The first algorithm does incremental composition and reduction of FSMs. It uses three heuristic rules which reduce the number of states in the global FSM by one to two orders of magnitude while maintaining its observational equivalence. The second algorithm checks whether the behavior of one FSM is a subset of another FSM's behavior. This procedure has been applied to the ISDN Q.931 and alternating bit protocols View full abstract»

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  • Power suppression at the Nyquist frequency for pilot-aided PAM and QAM systems

    Publication Year: 1989 , Page(s): 984 - 986
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    Two low-redundancy codes for in-band pilot insertion are introduced. KF10 suppresses the baseband PAM and the modulated QAM signal power at the Nyquist frequency so that the dual-pilot tone calibration technique of recent interest can be arranged to convey both a symbol timing and a carrier reference to the receiver. OF00 suppresses the signal power at zero as well as the Nyquist frequency and allows the utilization of a triple-pilot scheme which provides, in addition to a symbol timing, a carrier reference with no 180° phase ambiguity View full abstract»

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  • Estimation of reliability for communication/computer networks simulation/analytic approach

    Publication Year: 1989 , Page(s): 927 - 933
    Cited by:  Papers (12)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    A general simulation/analytic approach for jointly assessing the reliability and performance of a communication/computer network is proposed. The advantages of this approach are the following: (a) it allows consideration of a variety of performance measures, (b) it allows consideration of a general structure of network components failure distribution, (c) it reduces complexity of the model and related calculations, (d) it is relatively simple to implement, and (e) it can derive sensitivity information about network performance with respect to various parameters-the first step for an effective network optimization algorithm. The method is illustrated in a number of examples using network connectivity and weighted network bandwidth as a measure of performance View full abstract»

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  • A simple series for personal computer computation of the error function Q(·)

    Publication Year: 1989 , Page(s): 989 - 991
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    A simple series for computation of the error function Q(·) is derived. It is well suited for implementation on a personal computer, having six or more significant figure accuracy over a wide range of argument and requiring few lines of code to program. Its advantage over other series is its rapid convergence over a wide range of argument View full abstract»

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  • A baseband residual vector quantization algorithm for voiceband data signals

    Publication Year: 1989 , Page(s): 949 - 955
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    A new approach is presented to the digitization and compression of a class of voiceband modem signals. The approach, baseband residual vector quantization (BRVQ), relies heavily on the simple structure present in a modem signal. After the signal is converted to baseband, the magnitude sequence and the sequence of residuals obtained when the phase within each baud of the baseband signals is modeled by a straight line are separately vector quantized. Carrier frequency estimation and baud-rate classification schemes that were designed to carry out these operations are described. Experimental results show that the performance of the BRVQ system at and below 16 kb/s is better than that of a previously developed vector quantization scheme that has itself been shown to outperform traditional speech-compression techniques such as adaptive predictive coding, adaptive transform coding, and subband coding when these techniques are used to compress modem signals View full abstract»

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  • Optimal circuit access policies in an ISDN environment: a Markov decision approach

    Publication Year: 1989 , Page(s): 934 - 939
    Cited by:  Papers (67)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    The problem of determining optimal access policies for circuit-switched networks that support traffic types with varying bandwidth requirements is addressed. The authors suppose that the network supports K classes of calls where each class is determined by a fixed route and a bandwidth requirement. A Markov decision process (MDP) approach is used to obtain optimal access policies for three models: the flexible scheme access-port model where a single link is shared; the contiguous scheme access-port model where wideband calls are required to occupy specific contiguous regions of the TDM frame; and the network-access model where a call holds several channels in different links simultaneously. Both linear programming and value-iteration MDP algorithms are coupled with a novel state descriptor in order to locate the optimal policy for reasonable-size problems (several T1 carriers in parallel for the access-port case, and small networks of T1 carriers for the network-access case) View full abstract»

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  • A data-derived reference signal technique for adaptive arrays

    Publication Year: 1989 , Page(s): 975 - 983
    Cited by:  Papers (1)  |  Patents (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    A new technique is presented for reference signal generation in adaptive arrays, and it is shown how it can be used in a binary FSK communication system. This method consists of encoding the message bit stream at the transmitter to convert it to a first-order Markov source with a transition probability of p>1/2. Then, in the receiver, each detected bit is used to predict the next bit, and the predicted bits are used to generate a reference signal. The performance of an FSK system based on this concept is analyzed, and an experimental system is described. This experimental system demonstrated that the reference signal generation concept is feasible and showed that this technique could be used to protect an FSK communication system from a CW interference signal View full abstract»

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  • Design of coded CPFSK modulation systems for bandwidth and energy efficiency

    Publication Year: 1989 , Page(s): 897 - 905
    Cited by:  Papers (43)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    Consideration is given to the problems related to the design of M-ary continuous-phase frequency-shift keying (CPFSK) systems with modulation index h=J/M, combined with eternal rate r binary convolution encoders. The following questions are raised and answered: (1) how should different encoder-modulator systems be compared and how can comparable systems be recognized from the system parameters, i.e. M, h, and r?; (2) what are the limits on the information rate per unit bandwidth, versus signal-to-noise ratio, when reliable transmission is required?; (3) how does one choose the system parameters M, h, and r when the overall system has to achieve a specified performance?; and (4) how does one design the external rate r binary convolutional encoder to put in front of the M-ary CPFSK modulation system with h=J/M ? A simple approximation for the bandwidth of a CPFSK signal is given and shown to be sufficiently accurate for system design purposes. The design of the external convolutional encoder is carried out in a novel way that leads to fewer states in the combined encoder-modulator system and thus yields improved performance for a given demodulation-decoding complexity compared to previous approaches for the design of coded CPFSK systems View full abstract»

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  • A new configuration for echo canceller adaptable during double talk periods

    Publication Year: 1989 , Page(s): 969 - 974
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    A three-port echo canceler (EC) configuration is proposed which observes the signal of the near-end side on a two-wire circuit in addition to the four-wire circuit signals. Embedding these signals on hybrid ports into a three-dimensional autoregressive process, echo path and innovations of near- and far-end speeches can be estimated through a three-channel lattice filter. The new configuration is then able to track echo path time variance, even during double talk (DT), and requires no changeover at either the beginning or end of DT, thus eliminating the need for DT detection. Two echo synthesizers utilizing inverse lattice and the echo path estimate possess guaranteed stability without the need for testing View full abstract»

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  • Interference rejection in PN spread-spectrum systems with LS linear phase FIR filters

    Publication Year: 1989 , Page(s): 991 - 994
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    The effects of a narrowband interference present in a pseudonoise (PN) spread-spectrum system can be minimized by using digital whitening techniques. A new efficient block LS algorithm for the design of an FIR filter with linear phase is derived and used as a whitening filter. Simulations are carried out to demonstrate the effectiveness of the LS optimum linear-phase filter in suppressing a narrowband interference in a PN spread-spectrum system. Comparisons to previously used methods are made. The simulations showed an improvement in the output SNR on the order of 4-5 dB over already existing schemes View full abstract»

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  • Adaptive channel estimator for an HF radio link

    Publication Year: 1989 , Page(s): 918 - 926
    Cited by:  Papers (10)  |  Patents (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    A simple estimator designed for a 2400-b/s modem is a development of the conventional gradient estimator and uses a polynomial filter that gives a prediction of the channel response. A description is given of new estimators that are developments of the simple estimator but make no use of any knowledge of the number of different paths. The new estimators have performances intermediate between those of the simple and improved estimators, but are only a little more complex than the simple estimator. The new estimators are studied for a particular QPSK modem that operates at 4800 b/s over voiceband HF radio links. Results of computer simulation tests are presented, comparing the accuracies of the channel estimates given by different estimators, and hence suggesting the most suitable of these View full abstract»

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  • Quantization noise in single-loop sigma-delta modulation with sinusoidal inputs

    Publication Year: 1989 , Page(s): 956 - 968
    Cited by:  Papers (70)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (916 KB)  

    An exact nonlinear difference equation is derived and solved for a simple sigma-delta modulator consisting of a discrete-time integrator and a binary quantizer inside a single feedback loop and an arbitrary input signal. It is shown that the system can be represented as an affine operation (discrete-time integration of a biased input) followed by a memoryless nonlinearity. An extension of the transform method for the analysis of nonlinear systems is applied to obtain formulas for first- and second-order time-average moments of the binary quantization noise, including the sample mean, energy, and autocorrelation. The results are applied to the special case of a sinusoidal input signal to evaluate these time averages and the power spectrum. In the limit of large oversampling ratios, the marginal moments behave as if the quantization noise had a uniform distribution. The spectrum is neither white nor continuous, however, even in the limit of large oversampling ratios View full abstract»

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  • Error detecting capabilities of the shortened Hamming codes adopted for error detection in IEEE Standard 802.3

    Publication Year: 1989 , Page(s): 986 - 989
    Cited by:  Papers (21)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    Investigates the error detecting capabilities of the shortened hamming codes adopted for error detection in IEEE Standard 802.3. These codes are also used for error detection in the data link layer of the Ethernet, a local area network. The authors compute the weight distributions for various code lengths. From the results, they show the probability of undetectable error and that of detectable error for a binary symmetric channel with bit-error rate 10-5⩽ε⩽ 1/2. They also find the minimum distance of the shortened code of length n for 33 ⩽n ⩽12144 and the double-burst detecting capabilities View full abstract»

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  • The power spectrum of run-length-limited codes

    Publication Year: 1989 , Page(s): 906 - 917
    Cited by:  Papers (43)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (792 KB)  

    A novel method is developed for computing formulas for power spectra associated with run-length-limited (RLL) codes. Explicit use is made of a compact description of the run-length process associated with the RLL code. This association simplifies the general derivation of the power spectrum. The calculation of the spectra of several RLL codes popular in data storage applications is presented. Some of the closed-form expressions for the spectra of these widely used codes are new 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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Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia