Scheduled System Maintenance:
On May 6th, single article purchases and IEEE account management will be unavailable from 8:00 AM - 12:00 PM ET (12:00 - 16:00 UTC). We apologize for the inconvenience.
By Topic

Communications, IEEE Transactions on

Issue 9 • Date Sep 1990

Filter Results

Displaying Results 1 - 25 of 45
  • Sequence estimation techniques for digital subscriber loop transmission with crosstalk interference

    Publication Year: 1990 , Page(s): 1367 - 1374
    Cited by:  Papers (9)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    The use of reduced-state sequence estimation techniques in a digital subscriber loop receiver is discussed. These techniques offer a potential performance improvement over conventional equalization techniques such as decision feedback equalization (DFE). Stationary and cyclostationary NEXT noise models are described. The theoretical performance obtainable from a Viterbi algorithm receiver with stationary white Gaussian noise, stationary NEXT, and cyclostationary NEXT noise models is estimated, and the reduced-state decision feedback sequence estimation and M algorithms are reviewed. It is shown that the improvement can be especially significant in the presence of cyclostationary crosstalk because of the freedom that sequence estimation receivers afford in the choice of receiver sampling phase. This advantage is evaluated for Viterbi algorithm receivers. By simulation of two practical reduced-state sequence estimation receivers, it is demonstrated that, in the presence of cyclostationary crosstalk, a substantial increase in maximum loop range (or equivalently, maximum bit rate) may be achievable compared to conventional DFE equalization View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the statistical dependence of hits in frequency-hop multiple access

    Publication Year: 1990 , Page(s): 1483 - 1494
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (800 KB)  

    The statistical dependence of hits due to multiple-access interference in an asynchronous slow-frequency-hop packet radio network in which the radios employ memoryless hopping patterns is described. Models in which hits are conditionally independent given the number of interfering packets are investigated. It is shown that if the conditional probability of a hit is chosen appropriately, the distribution function for the number of hits in a packet for these models can be used to compute upper and lower bounds on the true distribution function for the number of hits. Conditions are described for which these models can be used to compute upper and lower bounds on the codeword and packet error probabilities. It is shown that if the ratio of the number of interfering packets to the number of frequency slots is held constant, hits in the asynchronous frequency-hop network are asymptotically independent in the limit as the number of frequency slots increases. This result suggests that when the number of frequency slots is large, error probabilities can be closely approximated by using the distribution for the number of hits that results from assuming that hits are independent View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Stack algorithms for random multiple-access networks in the presence of asymmetric feedback

    Publication Year: 1990 , Page(s): 1308 - 1313
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    The operation of stack splitting random-access protocols in multiaccess networks in which individual stations may receive asymmetric feedback from the channel (i.e. different stations may observe different, possibly erroneous, outcomes on the channel) is examined. Several possible modifications to the basic stack algorithm are proposed for such environments, and the performances of the various alternatives are reviewed. An approximate Markov chain model is developed to analytically study the time delay versus throughput performance of the various alternatives, and the analytic results are validated through simulation. Representative performance results are given for the alternative stack algorithms. It is found that those algorithms which tend to treat the receipt of corrupted feedback by a station as a collision show superior performance for throughput values greater than approximately 0.2, whereas, at low throughput values, there is relatively little difference between the performances of the various approaches studied. It was noted during the simulation studies that, with an error rate of up to 5%, the algorithms remained stable up to an arrival rate of approximately 0.3 or higher View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Tone interference immunity in a Fourier transform data transmission system

    Publication Year: 1990 , Page(s): 1337 - 1340
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    An algorithm that can minimize the effects of a tone interference in a Fourier transform data transmission (FTDT) system is derived. The algorithm works well even in the presence of additive white Gaussian noise. The error performance of the FTDT system with this tone removal method is discussed. A simulation study shows that this algorithm limits the system error performance deterioration due to a large tone interference to about 0.3 dB. The implementation of this algorithm requires three complex words at the transmitter transform input to be filled with zeros. The observed values at the corresponding location at the receiver transform output are used to evaluate the characteristics of the interfering tone. The effects of the tone interference can then be eliminated View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A new method for Viterbi decoder simulation using importance sampling

    Publication Year: 1990 , Page(s): 1341 - 1351
    Cited by:  Papers (48)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1116 KB)  

    Each simulation run simulates a single error event-that is, a subsequence of incorrect trellis branching decisions-and importance sampling is used to emphasize important nontrivial error events. The fundamental principles of the error event simulation method in conjunction with importance sampling are reviewed. The importance sampling background for coded communications systems is discussed in the context of block codes, because it is easier to present the fundamentals of importance sampling without the additional complexities of Viterbi decoding. The details of the error event simulation method for Viterbi decoders and numerical examples that demonstrate this method are presented. These numerical examples involve both hard and soft decision decoding for the ideal additive Gaussian noise channel. The technique is shown to provide markedly improved efficiency View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Spectral analysis of 49 years of rainfall rate and relation to fade dynamics

    Publication Year: 1990 , Page(s): 1359 - 1366
    Cited by:  Papers (17)  |  Patents (98)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB)  

    The nature of the rainfall rate R(t) as a transient random process is presented in the context of microwave attenuation and fade dynamics. Using 49 years of data recorded in Barcelona, the spectral densities of energy and power and the autocorrelation function are presented, together with their analytical model. Examples for specific rain events are also presented. Several regimes covering a wide range of intensities have been investigated, and it is found that the spectral densities all exhibit a similar form which is independent of the average regime of R considered. This leads to a mean frequency and a spectral width which appear to be universal constants and independent of the regime. Similar features are found for the autocorrelation function. The mathematical models and numerical values found are compared to the Maseng-Bakken model (1981) proposed in earlier work of fade dynamics, and the agreement is good. The method is proposed for modeling the denormalized autocorrelation, and hence the spectrum, using only the measured average rainfall rate during a period of interest. Finally, the average number of crossings per unit of time is modeled and compared to the experimental results, and the agreement is satisfactory View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Rearrangeable operation of large crosspoint switching networks

    Publication Year: 1990 , Page(s): 1616 - 1624
    Cited by:  Papers (6)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (948 KB)  

    A major impediment to building large crosspoint chips for configuring crosspoint switching networks is the simultaneous switching (Delta-I) noise problem that is caused by the switching of a large number of line drivers driving the output pins of the package. This limits the size of the largest crosspoint chips that can be operated reliably. An architectural solution to this problem is presented for networks constructed from one-sided crosspoint switching chips. The approach seeks to minimize the maximum number of active drivers in the individual chips by distributing the active drivers in the network uniformly among the chips by allowing rearrangements of existing connections when a new connection is made. A graph model is used to determine the number and location of rearrangements. An allocation scheme based on a simplified graph model that achieves a 50% reduction in the maximum number of active drivers per chip as compared to a random allocation strategy is presented. A maximum of three rearrangements is sufficient to obtain this reduction View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Overflow analysis for finite waiting room systems

    Publication Year: 1990 , Page(s): 1569 - 1577
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (948 KB)  

    A system of multiple primary queues with finite waiting rooms, where blocked jobs are allowed to overflow onto a common secondary queue, also with finite waiting room, is considered. Poisson arrivals and exponentially distributed service times, possibly different ones, are assumed at each primary service facility. Service facilities consist of a single server or multiple servers. Based on a simple iterative expression for the Laplace-Stieltjes transform of the interoverflow time distribution, the peakedness of the overflow process from primary queues is studied as a function of the number of primary servers and buffers as well as the original primary load. Behaviors and relations are identified for extreme cases (low offered load or large waiting rooms) and illustrated with examples. An approximation consisting of a natural extension of Hayward's formula to finite waiting room systems is proposed to estimate the blocking seen by the overflow traffic offered to the secondary service facility. Numerical examples covering a wide range of systems show that the approximation is good over a wide range of loads for systems with a single primary queue, as well as at high load for systems with multiple primary queues View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A baud-rate full-duplex transmission unit for subscriber loops

    Publication Year: 1990 , Page(s): 1495 - 1503
    Cited by:  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (832 KB)  

    A baud-rate full-duplex digital transmission unit for 144-kb/s basic access over an existing subscriber loop plant is described. The adaptive operations performed include echo cancellation, decision feedback equalization, reference control, and timing recovery. The unit operates at the baud rate, allows a fully digital implementation, and requires no special training sequences. Baud-rate timing recovery is a crucial issue. A method which only estimates timing error when certain data sequences occur is described and applied to subscriber loops. The behavior of this method in a region of incorrect decisions due to intersymbol interference is analyzed as a one-dimensional random walk. This indicates that escape from this region will be rapid when the gain is moderately large. Timing issues at exchange and subscriber ends are discussed. Different start-up strategies involving staggered turn-on plus gear shifting for both ends are proposed to decouple the adaptive loops and yield relatively low convergence times. In particular, at the exchange end, timing recovery is initially decoupled by successively adapting the remaining loops at several instants within the baud period. The instant closest to the optimum is then that instant with a minimum timing estimate variance View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Trellis coded communication systems-colored noise and the swapping technique

    Publication Year: 1990 , Page(s): 1549 - 1556
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    An analytical approach for investigating the effect of noise correlation on the performance of trellis-coded communication systems is described. Several trellis codes are investigated in the presence of colored noise, and computer simulation and real-time experimental results are given to confirm the analysis. In some practical cases, the actual coding gain could be as small as a fraction of 1 dB as opposed to the nominal 4-5 dB of coding gain that can be obtained on additive white Gaussian noise (AWGN) channels. A filter swapping technique which eliminates the performance degradation due to the effect of noise correlation is proposed. It is shown that if the equalizer is moved from the receiver to the transmitter and is scaled to satisfy an average power constraint, then the noise at the Viterbi decoder input is white and the signal-to-noise ratio remains the same. Doing this allows the nominal coding gain to be achieved View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Symbol synchronization for digital signals with multisegment trajectory: digital data transition tracking loop

    Publication Year: 1990 , Page(s): 1637 - 1644
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    The symbol synchronizer presented is an all-digital data transition tracking loop which permits simple implementation and voltage control of the loop bandwidth. The equivalent loop integration constant is changed by changing the threshold level of a comparator at the output of the loop phase error detector. Phase error probability distribution function, its variance, and the average probability of cycle slipping are analyzed analytically for the general case. The theory of finite Markov chains is used to analyze statistical properties of the tracking error, primarily with regard to the phase error distribution and its variance, the average probability of the cycle slipping, the synchronizer time response, and bandwidth. As an example, numerical results for generalized tamed frequency modulation (GTFM with B=0.62 and r=0.36) are presented and discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimal nonlinear interpolative vector quantization

    Publication Year: 1990 , Page(s): 1285 - 1287
    Cited by:  Papers (56)  |  Patents (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    A process by which a reduced-dimensionality feature vector can be extracted from a high-dimensionality signal vector and then vector quantized with lower complexity than direct quantization of the signal vector is discussed. In this procedure, a receiver must estimate, or interpolate, the signal vector from the quantized features. The task of recovering a high-dimensional signal vector from a reduced-dimensionality feature vector can be viewed as a generalized form of interpolation or prediction. A way in which optimal nonlinear interpolation can be achieved with negligible complexity, eliminating the need for ad hoc linear or nonlinear interpolation techniques, is presented. The range of applicability of nonlinear interpolative vector quantization is illustrated with examples in which optimal nonlinear estimation from quantized data is needed for efficient signal compression View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Two new coding techniques for diversity communication systems

    Publication Year: 1990 , Page(s): 1530 - 1538
    Cited by:  Papers (5)  |  Patents (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    In classical diversity techniques used in combating fading and in spread-spectrum systems, the same information is transmitted over m ⩾2 channels, and the overall error probability is reduced by a suitable combination of the m received signals. Two techniques are proposed whereby the signals transmitted over the m channels corresponding to a given message can be encoded through a suitable error-correcting coding operation, thereby enhancing reductions in the receiver-side bit error probability with respect to classical diversity techniques. Gains have also been achieved by introducing a soft decoding operation at the receiver side and, in spread-spectrum systems, by adding side information. Applications to fading-affected communication systems and spread-spectrum systems are discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The effect of phase noise on noncoherent digital communications

    Publication Year: 1990 , Page(s): 1539 - 1548
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    The effect of oscillator phase noise on noncoherent data detection is considered with the objective of relating more specifically than in prior studies the phase noise key parameters (bandwidth, spectral slopes, upper and lower cutoffs, spectral height). The concentration is on binary frequency-shift keying (FSK) and differential phase-shift keying (DPSK). Expressions that relate decoding error probability to the phase noise spectra are derived. It is shown that decoding degradation can be accurately approximated by relatively simple integrals involving the phase noise structure function (the latter obtained directly from the phase spectrum). Examples with reported crystal and cesium oscillator noise are presented. The key phase noise parameters are the spectral bandwidth relative to the bit rate, and the gain level of the phase noise (the latter being dependent on the carrier frequency to which the oscillator is multiplied). Separate results are derived for FSK and DPSK, but the order of the degradation is comparable in both cases View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sequential CFAR detectors using a dead-zone limiter

    Publication Year: 1990 , Page(s): 1375 - 1383
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB)  

    The performances of some proposed sequential constant-false-alarm-rate (CFAR) detectors are evaluated. The observations are passed through a dead-zone limiter, the output of which is -1, 0, or +1, depending on whether the input is less than -c, between -c, and c, or greater than c , where c is a constant. The test statistic is the sum of the outputs. The test is performed on a reduced set of data (those with absolute value larger than c), with the test statistic being the sum of the signs of the reduced set of data. Both constant and linear boundaries are considered. Numerical results show a significant reduction of the average number of observations needed to achieve the same false alarm and detection probabilities as compared to a fixed-sample-size CFAR detector using the same kind of test statistic View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Considerations of periodic traffic in packet switching

    Publication Year: 1990 , Page(s): 1625 - 1629
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    The basic model of packet switching based on a self-routing interconnection network is described. The theory of periodic contention is reviewed, showing that a broadband switch is nonblocking for the periodic traffic type if it is fast enough to avoid the phenomenon of persistent blocking, where an input buffer consistently transmits fewer packets than it is receiving. The necessary and sufficient switch rate for avoiding persistent blocking is determined. This rate turns out to be a more stringent requirement than if the traffic pattern had been Poisson, a usual assumption View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Random-access systems with a time varying channel

    Publication Year: 1990 , Page(s): 1293 - 1297
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A random multiple-access system which employs a collision resolution algorithm for accessing a common time-varying channel is considered. The channel is assumed to be in one of two states. In each state, the channel is characterized by a general discrete memoryless channel and the transitions between the two states are assumed to be Markovian. A set of sufficient conditions for the ergodicity (stability) of the system is established. As an example, the case when the Capetanakis tree algorithm operates with a time-varying noisy channel is examined. The stability of this system is analyzed, and the throughput is evaluated View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The performance of trellis-coded MDPSK with multiple symbol detection

    Publication Year: 1990 , Page(s): 1391 - 1403
    Cited by:  Papers (50)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (876 KB)  

    The idea of using a multiple (more than two) symbol observation interval to improve error probability performance is applied to differential detection of trellis-coded multiple phase-shift keying (MPSK) over an additive white Gaussian noise (AWGN) channels. An equivalent Euclidean distance measure per trellis branch is determined for this detection scheme. This is used to define an augmented (larger multiplicity) trellis code whose distance measure is the conventional squared Euclidean distance typical of conventional trellis-coded modulation on the AWGN. Such an augmented multiple trellis code is a convenient mathematical tool for simplifying the analysis. Results are obtained by a combination of analysis and computer simulation. It is shown that only a slight increase (e.g. one symbol) in the length of the observation interval will provide a significant improvement in bit error probability performance View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Interference modeling in a direct-sequence spread-spectrum packet radio network

    Publication Year: 1990 , Page(s): 1475 - 1482
    Cited by:  Papers (50)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    A technique for characterizing multiuser interference and background noise in a direct-sequence spread-spectrum network is introduced, and packet error probabilities are calculated. The multiuser interference over a packet in the network is modeled as a compound Gaussian multivariate random variable for moderate to large values of the processing gain. The conditional variance is dependent on the number of users and their interference powers. The method works for any interference with statistics of the block interference having a spherically symmetric distribution. The best performance results, in terms of the expected total interference power, are obtained for the case of a large number of interferers with comparable interference powers. As the number of interferers approaches infinity, the performance is the same as that for Gaussian noise. For a small number of interferers, the block error probability curve is broader than that for Gaussian noise. For small values of SNR, the probability of error is smaller than that corresponding to Gaussian noise, and for large values of SNR it is larger. Modifications to the basic direct-sequence scheme that improve performance in the case of one strong interferer are suggested View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A number theoretic approach to time division multiplexing

    Publication Year: 1990 , Page(s): 1504 - 1510
    Cited by:  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    A systematic approach to synchronous time division multiplexing (TDM) in embedded systems employing TDM as a switching fabric in the form of a bus is presented. The benefits of this approach are increased system capacity, individual and unrestricted circuit creation for all channels regardless of their bandwidth, latency ranging from a fraction of a bit to several bits, and independent tracking of timing and control signals for all interfaces requiring such service. The method divides time in such a way that every circuit receives a quantum of time equal to its nominal bandwidth, thus allowing all circuits to be explicitly identified on the switching fabric. The procedure that accomplishes this type of TDM is based on solutions to sets of linear congruences, also known as linear Diophantine equations. This scheme significantly reduces the cost of an embedded interface and allows flexibility for unbundling the subrate channels, thus permitting easy implementation of subrate multiplexing. It also simplifies design of switching fabrics which must carry voice mixed with subrate bit-interleaved or packet mode data and with ISDN nodes View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Coding of optical on-off keying signals impaired by phase noise

    Publication Year: 1990 , Page(s): 1301 - 1307
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The benefits of coding for an optical communication system that employs binary on-off keying and heterodyne detection are quantified. The system is impaired by laser phase noise as well as by additive white Gaussian noise (AWGN). A receiver structure especially designed to mitigate the effects of phase noise in the presence of AWGN is assumed. This special receiver structure requires a wider-band front-end IF filter than would be required for a phase-noise-free signal. The results, computed for several different coding schemes, indicate that the benefits of coding are large and the costs are small. For a linewidth-to-bit-rate ratio (βT) of 0.64 (for example, 45 Mb/s and 29 MHz linewidth), a half-rate binary code that can correct 3 bit errors provides a 50% reduction in the required IF filter bandwidth (and, therefore, the required IF) and about 5 dB of reduction in required laser power. The benefits of coding are greatest under high-βT conditions, corresponding to low bit rates where coders and decoders are most practical to implement View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Precision time-transfer in transport networks using digital cross-connect systems

    Publication Year: 1990 , Page(s): 1325 - 1332
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    A technique for precise synchronization of the time-of-day clocks in networks of digital cross-connect systems (DCSs) is described. This method is intended to enhance the performance of reconfigurable transport networks and is specifically devised to exploit the fine time resolution of the carrier signals to which a DCS has direct access. The resulting scheme is a master-slave, multisite, implicitly delay compensated, nonhierarchical time-transfer method with a theoretical precision of one bit time at the carrier rate. In practice, precision is limited by transmission span delay asymmetries but residual time errors of under 1 μs are predicted. The method is intended for n/ n space-switching DCS, but other DCS properties can be accommodated. Requirements for DCS equipment design are given, including a generic circuit module for DCS hardware support of the time transfer function. The proposed method applies to DS-3 networks or synchronous optical networks and requires no change in the standards. Measurement or improved estimation of characteristic span delay asymmetries is recommended to refine the preliminary performance estimate View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Packet error probabilities in direct-sequence spread-spectrum packet radio networks

    Publication Year: 1990 , Page(s): 1599 - 1606
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    The problem of computing packet error probabilities caused by a combination of noise at the receivers and interference between packet transmissions is discussed. An upper bound on the packet error probability induced in direct-sequence spread-spectrum networks is computed. The bound is valid independently of whether signals arrive with equal or unequal powers at the receiver site. It has a simple form, is easy to compute, and is valid for various classes of forward error correction codes (e.g. BCH, convolutional codes) View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Selective-repeat ARQ: the joint distribution of the transmitter and the receiver resequencing buffer occupancies

    Publication Year: 1990 , Page(s): 1430 - 1438
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    A selective-repeat automatic-repeat request (SR ARQ) system model in which packets arrive at the transmitter according to a general renewal process is analyzed. The overall delay of a packet in a system that operates under the SR ARQ protocol consists of the queuing delay at the transmitter and the resequencing delay at the receiver. The joint distribution of the buffer occupancies at the transmitter and at the receiver is derived, and the tow types of delay are compared using numerical examples View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Application of scale space to image coding

    Publication Year: 1990 , Page(s): 1585 - 1591
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    The continuous formulation of scale space is briefly reviewed. It is shown that deriving a discrete formulation of scale space requires the solution to a more general problem; the optimum approximation of a signal by local patterns. The consequences of the theory for the Laplacian image pyramid are discussed. A pyramid coding scheme based on the discrete scale-space formulation is derived. Preliminary coding results on real images are presented. Down to 1 b/pixel, the quality of the coded images is usually very close to that of the originals. Bit rates below 0.5 b/pixel imply a too coarse quantization, or even deletion, of the prediction error image at the smallest scale and, consequently, always result in images that are noticeably unsharp. In the intermediate region, different degrees of quantization noise and unsharpness are present. At comparable data rates, the linear variation coder generates less quantization noise in uniform regions, while the scale-space coder gives a slightly better edge reproduction View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Transactions on Communications focuses on all telecommunications including telephone, telegraphy, facsimile, and point-to-point television by electromagnetic propagation.

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia