By Topic

Communications, IEEE Transactions on

Issue 4 • Date April 2000

Filter Results

Displaying Results 1 - 23 of 23
  • Abstracts of forthcoming manuscripts

    Publication Year: 2000 , Page(s): 716 - 722
    Save to Project icon | Request Permissions | PDF file iconPDF (18 KB)  
    Freely Available from IEEE
  • Multidimensional signal space partitioning using a minimal set of hyperplanes for detecting ISI-corrupted symbols

    Publication Year: 2000 , Page(s): 637 - 647
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    A signal space partitioning technique is presented for detecting symbols transmitted through intersymbol interference channels. The decision boundary is piecewise linear and is made up of several hyperplanes. The goal here is to minimize the number of hyperplanes for a given performance measure, namely, the minimum distance between any signal and the decision boundary, Unlike in Voronoi partitioning, individual hyperplanes are chosen to separate signal clusters rather than signal pairs. The convex regions associated with individual signals, which together form the overall decision region, generally overlap or coincide among in-class signals. The technique leads to an asymptotically optimum detector when the target distance is set at half the minimum distance associated with the maximum-likelihood sequence detector. Complexity and performance can be easily traded as the target distance is a flexible design parameter View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultra-wide bandwidth time-hopping spread-spectrum impulse radio for wireless multiple-access communications

    Publication Year: 2000 , Page(s): 679 - 689
    Cited by:  Papers (1326)  |  Patents (67)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    Attractive features of time-hopping spread-spectrum multiple-access systems employing impulse signal technology are outlined, and emerging design issues are described. Performance of such communications systems in terms of achievable transmission rate and multiple-access capability are estimated for both analog and digital data modulation formats under ideal multiple-access channel conditions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Base station placement for in-building mobile communication systems to yield high capacity and efficiency

    Publication Year: 2000 , Page(s): 658 - 669
    Cited by:  Papers (35)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    A study is made of the problem of placing base stations to yield high capacity and efficiency in an in-building direct-sequence code-division multiple-access wireless communication system. A key requirement for solving this problem is a reliable but simple model of in-building propagation. A number of propagation models are considered as part of a system's performance analysis and are found to produce widely ranging levels of accuracy. Correlated shadowing is identified as being a `key'in-building propagation characteristic that has the potential to strongly influence the system's performance. Propagation models that included correlated shadowing are shown to produce the most accurate estimates of outage probability when there are a number of interferers facing a user. Base station deployment is shown to be a dominant factor influencing the levels of correlated shadowing, and consequently, base station deployment is shown to have major implications on the system's performance. The system's performance for a variety of base station deployment strategies has been determined. The results indicate that there is a tradeoff between system simplicity and performance View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multihop packet scheduling in WDM/TDM networks with nonnegligible transceiver tuning times

    Publication Year: 2000 , Page(s): 692 - 703
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    This paper addresses the design of packet transmission schedules in photonic slotted wavelength-division multiplexing/time-division multiplexing broadcast-and-select networks with W wavelengths and N nodes. Nodes are equipped with one tunable-wavelength transmitter with nonnegligible tuning times and one fixed-wavelength receiver. A new scheduling algorithm that exploits multihop packet transfer to shorten the duration of scheduling periods is first proposed. A single-hop scheduling algorithm that performs slightly better than previous proposals is then described. A simulation-based analysis of the two algorithms shows that they jointly lead to significant improvements in both throughput and delay with respect to previous single-hop schedules View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive importance sampling for performance evaluation and parameter optimization of communication systems

    Publication Year: 2000 , Page(s): 557 - 565
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    We present new adaptive importance sampling techniques based on stochastic Newton recursions. Their applicability to the performance evaluation of communication systems is studied. Besides bit-error rate (BER) estimation, the techniques are used for system parameter optimization. Two system models that are analytically tractable are employed to demonstrate the validity of the techniques. As an application to situations that are analytically intractable and numerically intensive, the influence of crosstalk in a wavelength-division multiplexing (WDM) crossconnect is assessed. In order to consider a realistic system model, optimal setting of thresholds in the detector is carried out while estimating error rate performances. Resulting BER estimates indicate that the tolerable crosstalk levels are significantly higher than predicted in the literature. This finding has a strong impact on the design of WDM networks. Power penalties induced by the addition of channels can also be accurately predicted in short run-times View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Efficient computation of erfc(x) for large arguments

    Publication Year: 2000 , Page(s): 529 - 532
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    A new, infinite series representation for the error function is developed. It is especially suitable for computing erfc(x) for large x. For instance, for any x⩾4, the error function can be evaluated with a relative error less than 10-10 by using only eight terms. Similarly, the error function can be evaluated with a relative error less than 8×10-7 for any x⩾2 using just six terms. An analytical bound is derived to show that the total error due to series truncation and undersampling rapidly decreases as x increases. Comparisons with two other series are provided View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Blind self-noise-free frequency detectors for a subclass of MSK-type signals

    Publication Year: 2000 , Page(s): 704 - 715
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    Frequency offset due to Doppler shift and/or oscillator instabilities degrade the receiver performance. A family of frequency detectors for frequency offset estimation and compensation in digital receivers is introduced. The proposed detectors are best suited for frequency offset compensation of a subclass of binary continuous phase modulation with h=1/2 that includes modulation schemes with nonnegative frequency pulses. For the considered modulation schemes, the modulation-induced self-noise term is absent from the variance of the frequency estimate. The estimator is nondata- and nontiming-aided and its estimation range is either half or a quarter of the bit rate (R). With larger frequency offsets, the estimators that have a ±R/2 estimation range introduce a frequency ambiguity of R that is of no relevance to the performance of a differential detection based receiver View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • MAP algorithms for decoding linear block codes based on sectionalized trellis diagrams

    Publication Year: 2000 , Page(s): 577 - 587
    Cited by:  Papers (9)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The maximum a posterioriprobability (MAP) algorithm is a trellis-based MAP decoding algorithm. It is the heart of turbo (or iterative) decoding that achieves an error performance near the Shannon limit. Unfortunately, the implementation of this algorithm requires large computation and storage. Furthermore, its forward and backward recursions result in a long decoding delay. For practical applications, this decoding algorithm must be simplifled and its decoding complexity and delay must be reduced. In this paper, the MAP algorithm and its variation's, such as log-MAP and max-log-MAP algorithms, are first applied to sectionalized trellises for linear block codes and carried out as two-stage decodings. Using the structural properties of properly sectionalized trellises, the decoding complexity and delay of the MAP algorithms can be reduced. Computation-wise optimum sectionalizations of a trellis for MAP algorithms are investigated. Also presented in this paper are bidirectional and parallel MAP decodings View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Code acquisition in coherent optical pulse CDMA systems utilizing coherent correlation demodulation

    Publication Year: 2000 , Page(s): 611 - 621
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    A code acquisition technique based on active optical correlation detection is introduced for coherent optical pulse code-division multiple-access (CDMA) systems implemented through coherent correlation demodulation. Passive matched filter acquisition, commonplace in most radio CDMA systems, does not translate directly into the optical domain since synchronization between the incoming optical signal and a local optical code of the intended user at the receiver has to take place in several picosecond duration. Parallel and serial acquisition schemes under the same search algorithm are described and the effect of optical device noise, partial autocorrelation, and multiuser interference on acquisition performance is theoretically analyzed. Numerical results are given for Gold codes. In general, the degree of parallelism inherent in code acquisition techniques for radio systems allows a tradeoff between acquisition speed and hardware cost; however, in optical acquisition schemes, increasing the degree of parallelism with the concomitant hardware cost penalty does not necessarily reduce the time to acquisition. This is due to optical power budget limitations brought about by the need to split the optical signal, although optical amplifier technology can improve the performance of these parallel search schemes. The expressions for the partial correlation and multiuser interference derived in the paper can also be utilized for the analysis of other radio and optical acquisition schemes View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An analytic technique to separate cochannel FM signals

    Publication Year: 2000 , Page(s): 543 - 546
    Cited by:  Papers (9)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (96 KB)  

    A new technique is presented to separate two cochannel frequency modulation signals. Two candidate solutions for the phases are analytically derived, and a sequence of phase solutions is chosen to match the expected power spectral density of each constituent signal. This is accomplished with a one-step linear predictor and a simple two-state Viterbi algorithm. Simulations on recorded radio frequency data indicate improved separation capability over other techniques such as the joint Viterbi algorithm and cross-coupled phase-locked loop View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Diversity order gain for narrow-band multiuser communications with pre-combining group detection

    Publication Year: 2000 , Page(s): 533 - 536
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    In narrow-band multiuser communication systems with fading diversity, it is shown that pre-combining group detection can bridge the diversity-order gap in performance between the optimum and linear detectors. For a system with M diversity channels, the group detector diversity order is M-|G|, where |G| is the interfering group size, a design parameter. Group detection thus provides a more substantial improvement in performance in narrow-band channels over linear detection than in wide-band channels in which the diversity orders of the optimal and linear detectors are equal. Here, the complexity of the receiver is a new parameter which, in addition to the number of antennas, can be used to control the diversity order. Exact formulas for the pairwise-error probabilities and bounds for the bit-error rate are obtained, and numerical results are shown View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimal transmission ranges and code rates for frequency-hop packet radio networks

    Publication Year: 2000 , Page(s): 670 - 678
    Cited by:  Papers (26)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    We consider a frequency-hopping multihop packet radio network using M-ary frequency-shift keying modulation in a Rayleigh fading environment. Each node transmits packets using an extended (n, k) Reed-Solomon code and the slotted ALOHA channel access protocol. For this network, we determine the optimum transmission range, optimum code rate, and optimum slotted ALOHA transmission probability to be used by each node in the network. Tradeoffs in choosing the transmission range and code rate, and the spectral efficiency of the network are captured in a new performance measure, information efficiency, which is analogous to expected forward progress. Maximizing the information efficiency yields the optimum desired network parameters View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On antenna array receiver principles for space-time-selective Rayleigh fading channels

    Publication Year: 2000 , Page(s): 648 - 657
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    Optimum (in the sense of minimum-error probability) single-symbol diversity detection for fading, noisy channels is too complex for practical implementation. A simplified, near-optimum array receiver is proposed, which is based on the statistics (i.e., the covariance-function matrix) of the fading channel. This detector is then analyzed by calculating the exact error probability. When there is a spread of the direction of arrival of the incident radio waves, the proposed detector significantly gains over an adaptive antenna array (which forms a weighted sum of the received antenna signals). Also, for this adaptive array, a fundamental difference between maximum-likelihood weights and least-mean-square weights is observed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Digital precompensation of imperfections in quadrature modulators

    Publication Year: 2000 , Page(s): 552 - 556
    Cited by:  Papers (15)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    Residual carrier, balance, and quadrature error imperfections that are normally present in phase/quadrature modulators limit the use of direct modulation techniques in some applications. The classical precompensation techniques are revised and an adaptive solution proposed that improves performance by some order of magnitude View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Digital-to-RF conversion for a vector modulator

    Publication Year: 2000 , Page(s): 540 - 542
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    Digital technology lacks sufficient speed to support many high data rate applications at microwave frequencies. This is unfortunate since areas such as higher order modulation, predistortion, equalization, and demodulation could benefit in flexibility, modularity, and performance from digital architectures. However, use of radio frequency microwave technology permits the implementation of digital functions at these higher speeds and frequencies. This paper describes the implementation of a nonrecursive (finite-impulse response) filter in microwave technology View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The design and performance of a neural network for predicting turbo decoding error with application to hybrid ARQ protocols

    Publication Year: 2000 , Page(s): 566 - 576
    Cited by:  Papers (6)  |  Patents (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    It is shown that a neural network can be trained to observe the cross entropy of the outputs of component decoders in a turbo error control system and to accurately predict the presence of errors in the decoded data. The neural network can be used as a trigger for retransmission requests at either the beginning or the conclusion of the decoding process, providing improved reliability and throughput performance at a lower average decoding complexity than turbo decoding with cyclic redundancy check error detection View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Valuation of the effects of intersymbol interference in decision-feedback equalizers

    Publication Year: 2000 , Page(s): 629 - 636
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

    For channels which suffer predominantly from additive noise and intersymbol interference, the decision-feedback equalizer has provided a relatively simple solution for reducing the effects of interfering symbols at the input to the decision device. A technique is developed that enables fast, accurate calculation of the error performance of decision-feedback equalization for a number of channel models. The method is to calculate the n-step transition probability for an associated Markov process and then use this transition probability as an approximation to the stationary probability distribution. For systems with finite memory, it is proved that the method converges. If the signal-to-noise ratio (SNR) is high and the signal amplitude is more than twice the worst-case interference, it is shown that the convergence is rapid. Numerical results indicate that the convergence is rapid enough to make this an efficient method of calculation, even for channels for which the interference does not fully satisfy this condition. Two examples are given here, but the technique has been tested on most of the examples that have been presented in the literature. The method yields results in closer agreement with simulation results than previous results obtained using bounding techniques, especially at low to moderate SNRs, and requires less computation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Generalized Markov modeling for flat fading

    Publication Year: 2000 , Page(s): 547 - 551
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    This paper investigates the properties of a method for obtaining Markov models of unspecified order to be applied to narrow-band fading channels with additive white Gaussian noise. The models are obtained by applying the context tree pruning algorithm to experimental or simulated sequences. Fading environments are identified in which the extension from first-order to higher order models is justified. The paper presents, as examples, the evaluation of the covariance function and the packet error distribution View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Housekeeping for prefix coding

    Publication Year: 2000 , Page(s): 622 - 628
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    We consider the problem of constructing and transmitting the prelude for Huffman (1952) coding. With careful organization of the required operations and an appropriate representation for the prelude, it is possible to make semistatic coding efficient even when S, the size of the source alphabet, is of the same magnitude as m, the length of the message being coded. The proposed structures are of direct relevance in applications that mimic one-pass operation through the use of semistatic compression on a block-by-block basis View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Best short rate 1/2 tailbiting codes for the bit-error rate criterion

    Publication Year: 2000 , Page(s): 597 - 610
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    We give a method of finding convolutional codes with minimum bit-error rate (BER) that combines ideas of importance sampling, Monte Carlo integration, and maximum a posteriori probability decoding. The method is applied to rate 1/2 tailbiting convolutional coding, both feedforward and feedback systematic. Tables of BER-minimizing encoders are given for memories 2-5 and tailbiting size 5-40, over a range of good and bad binary symmetric and additive white Gaussian noise channels. The best generators for these cases are in general all different and are not necessarily the generators that optimize distance. The best generators for bad channels are always systematic. The best when the channel quality is known are usually feedforward, but when it is unknown, they are feedback systematic. The best generators in good channels are predicted by a union bound technique View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the performance of iterative noncoherent detection of coded M-PSK signals

    Publication Year: 2000 , Page(s): 588 - 596
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    Differential encoding is often used in conjunction with noncoherent demodulation to overcome carrier phase synchronization problems in communication systems employing M-ary phase-shift keying (M-PSK). It is generally acknowledged that differential encoding leads to a degradation in performance over absolutely encoded M-PSK systems with perfect carrier synchronization. In this paper, we show that when differential encoding is combined with convolutional encoding and interleaving, this degradation does not necessarily occur. We propose a novel noncoherent receiver for differentially encoded M-PSK signals that is capable of significantly outperforming optimal coherent receivers for absolutely encoded M-PSK using the same convolutional code. This receiver uses an iterative decoding technique and is based on a multiple differential detector structure to overcome the effect of the carrier phase error. In addition, to better illustrate the benefits of the powerful combination of convolutional encoding, interleaving, and differential encoding, we also present an iterative coherent receiver for differentially encoded M-PSK View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Online adaptive reinitialization of the constant modulus algorithm

    Publication Year: 2000 , Page(s): 537 - 539
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (44 KB)  

    An adaptive reinitialization algorithm for the constant modulus algorithm is proposed that relies on the similarities between the constant modulus and the Wiener equalizer and expands the capabilities of a previous algorithm. The proposed algorithm determines adaptively if the CMA will benefit through reinitialization, and if so, it will calculate new equalizer coefficients leading to the global minimum 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