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Communications, IEEE Transactions on

Issue 8 • Date Aug. 1990

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Displaying Results 1 - 22 of 22
  • Comments on "The structure of the limit cycles in sigma delta modulation

    Publication Year: 1990
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (114 KB)  

    In the above-titled paper by V. Friedman (see ibid., vol.36, p.972-9, Aug. 1988), noise spectra of single-loop sigma-delta modulators are calculated for DC inputs which are rational fractions of the quantizing steps. The commenter points out that, by using a simple combination of the previously published results, more explicit results are arrived at much more easily.<> View full abstract»

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  • Comments on "Exact results for nonsymmetric token ring systems

    Publication Year: 1990 , Page(s): 1125 - 1127
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (266 KB)  

    The commenters identify and correct errors in some of the equations in the above-titled paper by Ferguson and Aminetzah (see ibid., vol.COM-33, p.223-31, Mar. 1985), particularly those related to gated service discipline. In addition, they compare equivalent gated and exhaustive systems (using the corrected equations) numerically in terms of the mean waiting time behaviors at the various nodes, and in terms of the overall mean and variance of the mean waiting times across the nodes.<> View full abstract»

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  • Analysis of a type II hybrid ARQ scheme with code combining

    Publication Year: 1990 , Page(s): 1133 - 1137
    Cited by:  Papers (108)  |  Patents (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    An analysis is presented of the selective-repeat type II hybrid AR Q (automatic-repeat-request) scheme, using convolutional coding and exploiting code combining. With code combining, at successive decoding attempts for a data packet, the decoder for error correction operates on a combination of all received sequences for that packet rather than only on the two most recent received ones as in the conventional type II hybrid ARQ scheme. It is shown by means of analysis and computer simulations that with code combining, a significant throughput is achievable, even at very high channel error rates View full abstract»

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  • On the detection and classification of quadrature digital modulations in broad-band noise

    Publication Year: 1990 , Page(s): 1199 - 1211
    Cited by:  Papers (87)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1128 KB)  

    Optimal and suboptimal decision rules for the detection of constant-envelope quadrature digital modulations in broadband noise are derived and analyzed. The effect of various stochastic models for the carrier phase is examined in detail, while no epoch or frequency uncertainty is assumed. The delay-and-multiply type of detector is considered. A new binary/quadrature phase shift keying (BPSK/QPSK) classifier is compared to the more traditional ad hoc techniques of a square-law classifier and a phase-based classifier (weighting on the phase histogram). The new classifier is derived by approximating the likelihood-ratio functionals of phase-modulated digital signals in white Gaussian noise, hence is named the quasi-log-likelihood ratio (qLLR) rule. It is shown analytically that its performance is significantly better than that of intuitively designed phase-based rules or the conventional square-law classifier View full abstract»

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  • Improved decoding for a concatenated coding system recommended by CCSDS

    Publication Year: 1990 , Page(s): 1138 - 1144
    Cited by:  Papers (18)  |  Patents (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    The concatenated coding system recommended by CCSDS (Consultative Committee for Space Data Systems) uses an outer (255,233) Reed-Solomon (RS) code based on 8-b symbols, followed by the block interleaver and an inner rate 1/2 convolutional code with memory 6. Viterbi decoding is assumed. Two new decoding procedures based on repeated decoding trials and exchange of information between the two decoders and the deinterleaver are proposed. In the first one, where the improvement is 0.3-0.4 dB, only the RS decoder performs repeated trials. In the second one, where the improvement is 0.5-0.6 dB, both decoders perform repeated decoding trials and decoding information is exchanged between them View full abstract»

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  • Errors-and-erasures coding to combat impulse noise on digital subscriber loops

    Publication Year: 1990 , Page(s): 1145 - 1155
    Cited by:  Papers (10)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (824 KB)  

    The issue addressed is how closely ideal performance can be approached using a practical erasure declaration mechanism. A description is given of a specific practical erasure declaration mechanism, and the resulting coded system performance is investigated on the digital subscriber loop. Results indicate that, by appropriate choice of system parameters, it is possible to closely approach the ideal performance View full abstract»

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  • Broad-band ATM network architecture based on virtual paths

    Publication Year: 1990 , Page(s): 1212 - 1222
    Cited by:  Papers (120)  |  Patents (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1000 KB)  

    Broadband transport techniques and network architectures based on the virtual path concept are examined. ATM (asynchronous transfer mode) techniques, when coupled with recent technological innovations, are expected to pave the way for future universal transport networks. The virtual path concept, which exploits the ATM's capabilities, is proposed to construct an efficient and economic network. The concept matches current and anticipated technological trends well. Characteristics and implementation techniques of virtual paths are discussed. Advantages of the virtual path concept and its impact on the transport network architecture are demonstrated. The virtual path strategy is also shown to provide efficiently for networks with dynamic reconfiguration capability which will enhance network performance. Some basic analytical results on the dynamic control effects of virtual paths are provided View full abstract»

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  • Sequence estimation for class-IV partial-response channels with jitter

    Publication Year: 1990 , Page(s): 1181 - 1189
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    An analysis is presented of the output of class-IV partial-response channels corrupted simultaneously by jitter and additive white noise. The authors analyze the behavior of the least-squares (LS) decoder for this channel. They introduce the projection-minimization (P-M) algorithm and demonstrate that, under favorable conditions, its performance, even when not acceptable on its own, could possibly be beneficial when used in conjunction with the LS decoder in enhancing the reliability of the channel. Implementation of the P-M decoder is rather expensive, and it is not at all clear that combining the P-M algorithm with LS decoding and traditional error control schemes is the best way of dealing with channels corrupted by jitter. It may be possible to avoid the P-M algorithm and instead utilize a more aggressive traditional error correction scheme. Alternatively, it may be possible to choose modulation schemes which utilize pulses whose derivatives at the sampled values are small, and perhaps obtain better results than with partial-response class-IV signaling View full abstract»

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  • Algorithms to determine exact blocking probabilities for multirate tree networks

    Publication Year: 1990 , Page(s): 1266 - 1271
    Cited by:  Papers (31)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    A circuit-switched network consisting of multiple-access links connected to a common link is considered. Each call requires circuits on one access link and on the common link. The network supports multiple classes of calls where each class specifies a bandwidth requirement, an arrival rate, and a holding-time distribution. Based on a product-form solution for these networks, four algorithms are developed to determine the exact blocking probability for each of the classes. The first two algorithms are based on convolution, the third on the fast Fourier transform, and the fourth on a recursion due to J.S. Kaufman (1981) and to J.W. Roberts (1981). Complexity bounds and numerical results demonstrate that these algorithms can determine blocking probabilities in reasonable CPU time for networks with thousands of circuits View full abstract»

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  • Efficient estimators for an HF radio link

    Publication Year: 1990 , Page(s): 1173 - 1180
    Cited by:  Papers (10)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB)  

    A technique for the estimation of the sampled impulse response of an HF radio link was developed several years ago and was shown by computer simulation tests to have a substantial potential advantage in performance over more conventional systems. A number of further developments have led to new channel estimators. In some of these, a Kalman filter is incorporated into the system in such a way that the filter operates on only a few variable quantities and is therefore considerably less complex than a conventional Kalman filter. Three different Kalman filters are studied, two of these being designed for a channel varying linearly (at a constant rate) with time, and the third being a conventional Kalman filter that is designed for a time-invariant or very slowly time-varying channel. All of these employ an exponential window and therefore operate with a fading memory. A description is given of the various estimators, the results of a series of computer simulation tests are presented, and the accuracies of the channel estimates given by the different systems are compared View full abstract»

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  • Finding fixed satellite service orbital allotments with a k-permutation algorithm

    Publication Year: 1990 , Page(s): 1253 - 1259
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (580 KB)  

    A satellite system synthesis problem, the satellite location problem (SLP), is addressed. In SLP, orbital locations (longitudes) are allotted to geostationary satellites in the fixed satellite service. A linear mixed-integer programming model is presented that views SLP as a combination of two problems: the problem of ordering the satellites and the problem of locating the satellites given some ordering. A special-purpose heuristic procedure, a k-permutation algorithm, that has been developed to find solutions to SLPs formulated in the manner suggested is described. Solutions to small example problems are presented and analyzed on the basis of calculated interferences View full abstract»

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  • The use of interleaving for reducing noisy reference loss in trellis-coded modulation systems

    Publication Year: 1990 , Page(s): 1190 - 1198
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    The use of interleaving/deinterleaving in trellis-coded modulation systems to reduce the SNR loss due to imperfect carrier demodulation references is demonstrated. Both the discrete carrier (phase-locked loop) and the suppressed carrier (Costas loop) cases are considered, and the differences between the two are clearly demonstrated by numerical results. The special case of convolutional codes is also treated and illustrated with an example of practical interest View full abstract»

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  • A coding scheme for m-out-of-n codes

    Publication Year: 1990 , Page(s): 1156 - 1163
    Cited by:  Papers (12)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    A scheme for the construction of m-out-of-n codes based on the arithmetic coding technique is described. For appropriate values of n, k, and m, the scheme can be used to construct an (n,k) block code in which all the codewords are of weight m. Such codes are useful, for example, in providing perfect error detection capability in asymmetric channels such as optical communication links and laser disks. The encoding and decoding algorithms of the scheme perform simple arithmetic operations recursively, thereby facilitating the construction of codes with relatively long block sizes. The scheme also allows the construction of optimal or nearly optimal m-out-of-n codes for a wide range of block sizes limited only by the arithmetic precision used View full abstract»

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  • The compression effects of the binary tree overlapping method on digital imagery

    Publication Year: 1990 , Page(s): 1260 - 1265
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    A new method of digital image compression called binary tree overlapping (BTO) is described. With this method, an image is divided into bit planes that are transformed into a binary tree representation in which initial identical portions of different lines in the bit planes are transmitted as one path in the tree. To increase compression, distortion can be introduced by considering two lines which differ in fewer that a preset number of bit positions to be identical. A time efficient method of implementing BTO based on a communication technique called content-induced transaction overlap is outlined. With this technique, only simple, logical operations are needed and the compression time is proportional to the number of bits in the compressed image. Simulation studies indicate that BTO produces good quality images with a compression ratio of about three. In terms of implementation and compression efficiencies, BTO is comparable to first-order DPCM View full abstract»

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  • Calculation of message length transition probabilities in selective reject ALOHA channels

    Publication Year: 1990 , Page(s): 1128 - 1132
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    A method is described for the exact calculation of message length transition probabilities in asynchronous selective reject (SREJ) ALOHA channels with Poisson message arrivals. The formulas derived are used for exact calculation of the throughput characteristics of example SREJ-ALOHA channels which were previously analyzed using bounds or approximate methods View full abstract»

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  • Traffic characterization for integrated services networks

    Publication Year: 1990 , Page(s): 1231 - 1243
    Cited by:  Papers (54)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1056 KB)  

    A discrete-time queuing analysis is presented for integration of multiple traffic types in a packet-switched TDM (time-division multiplexing) system. The correlation of each traffic type is represented in terms of the power spectral density. The general expression obtained for the aggregate mean queue size indicates that slowly varying traffic types exert the largest effect on the queuing process. Also, a lengthy-steady traffic is highly predictable. An adaptive flow control and routing scheme, based on signal prediction, which successively adjusts the short-burst traffic arrival rate at each TDM node, is introduced and analyzed. The analytical results indicate a substantial reduction in the correlation effect on the system queuing behavior View full abstract»

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  • Analysis of quantized feedback low-frequency restoration in digital regenerators

    Publication Year: 1990 , Page(s): 1118 - 1120
    Cited by:  Papers (2)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    Quantized feedback, a DC restoration technique utilizing decision feedback equalization, can be used to compensate for unavoidable low-frequency cutoff in digital regenerators. An analysis is provided of the error probability and sensitivity to timing offsets of quantized feedback for a single-pole high-pass filter regenerator characteristic. Error probability is expressed in terms of the moments of the intersymbol interference (ISI), and these moments are calculated using the Markov chain properties of the ISI. To keep degradations small, the low-frequency cutoff should be no greater than 15% of the bit rate View full abstract»

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  • Error characteristics of fiber distributed data interface (FDDI)

    Publication Year: 1990 , Page(s): 1244 - 1252
    Cited by:  Papers (18)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (944 KB)  

    An analysis is made of the impact of various design decisions on the error detection capability of the fiber distributed data interface (FDDI), a 100-Mb/s fiber-optic LAN standard being developed by the American National Standards Institute (ANSI). In particular, the frame error rate, token loss rate, and undetected error rate are quantified. Several characteristics of the 32-b frame check sequence (FCS) polynomial, which is also used in IEEE 802 LAN protocols, are discussed. The standard uses a nonreturn to zero invert on ones (NRZI) signal encoding and a 4-b to 5-b (4b/5b) symbol encoding in the physical layer. Due to the combination of NRZI and 4b/5b encoding, many noise events are detected by code (or symbol) violations. A large percentage of errors are detected by FCS violations. The errors that escape these three violations remain undetected. The probability of undetected errors due to creation of false starting delimiters, false ending delimiters, or merging of two frames is analyzed. It is shown that every noise event results in two code bit errors, which in turn may result in up to four data bit errors. The FCS can detect up to two noise events. Creation of a false starting delimiter or ending delimiter on a symbol boundary also requires two noise events. This assumes enhanced frame validity criteria. The author justifies the enhancements by quantifying their effect View full abstract»

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  • Design and operation of packet-switched networks with uncertain message requirements

    Publication Year: 1990 , Page(s): 1223 - 1230
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    An important concern when choosing the link design and message routes is the uncertainty regarding future average hourly message requirements between sources and destinations. A model is proposed for this problem which accounts for the uncertain average number of source-destination messages by representing them as random variables. The model also allows use of the public switched telephone network (PSTN) to accommodate some of the message requirements. This is especially important with the advent of ISDN, which will offer high-speed capacity on a universal basis. Most previous research on packet-switched network design and operation has assumed known average message requirements (although actual message requirements vary according to a Poisson process) and has focused exclusively on the use of leased lines without the availability of the PSTN. These leased lines have fixed monthly costs for specific point-to-point transmission, whereas PSTN lines can access any node from a given location. It is shown how to accelerate convergence of the flow-deviation algorithm for solving the model. Computational results are reported View full abstract»

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  • A narrow bandpass microstrip filter for high-speed fiber optic systems

    Publication Year: 1990 , Page(s): 1122 - 1124
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    Transmission systems employing passively retimed regenerators require a bandpass timing filter to extract the timing wave from the data stream. Typically, filters with Q exceeding 100 are necessary in long-haul fiber-optic systems. The fabrication of a microstrip filter with a loaded Q of over 500 and an insertion loss of 8 dB, is reported. The midband return loss in 4.8 dB. The filter is fabricated on a 1-in×1-in×1-in Ba2Ti9 O20 substrate. This material has a dielectric constant of about 39 and can be formulated with temperature coefficients of resonant frequency from -2 to +6 p.p.m./°C. The fabricated device has a temperature coefficient of +2 p.p.m./°C. This combination of material properties facilitates high Q and small filter size and has the potential to compensate for temperature-induced electronic phase shifts between signal and clock recovery paths to the bit-decision circuit View full abstract»

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  • Cellular packet communications

    Publication Year: 1990 , Page(s): 1272 - 1280
    Cited by:  Papers (227)  |  Patents (38)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (900 KB)  

    The future of third-generation wireless networking is discussed. The vision of the third generation is a single set of standards that can meet a wide range of wireless access applications. Third-generation systems, in harmony with broadband integrated services digital networks, will use shared resources to convey many information types. A single network architecture will serve its users efficiently in many environments, including moving vehicles, indoor and outdoor public areas, residences, offices, and factories. A study of a switching architecture, referred to as a cellular packet switch, and a packet transmission technique, referred to as a packet reservation multiple access is discussed. By means of a design example, it is shown how these techniques can work together to meet some of the demands of third-generation systems View full abstract»

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  • On the channel capacity for constant envelope signals with effective bandwidth constraint

    Publication Year: 1990 , Page(s): 1164 - 1172
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    The problem of the optimization of the information rate with an assigned cost function is addressed. In the case of a constant envelope channel with a prescribed effective bandwidth as a cost function, an expression of the channel capacity is derived in the presence of Gaussian noise for large values of signal-to-noise ratio. The analysis of the optimum source statistics has also shown that the source signal is Gaussian, and therefore its autocorrelation function and power spectral density have been determined in terms of the required channel capacity 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