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Communications, IEEE Transactions on

Issue 5 • Date May 1999

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Displaying Results 1 - 22 of 22
  • Comments on "Partial parallel interference cancellation for CDMA"

    Publication Year: 1999 , Page(s): 658 - 661
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (103 KB)  

    We comment on partial parallel interference cancellation as discussed in the paper by Divsalar et al. (see ibid. vol.46, p.258-68, 1998). The aforementioned work showed that by multiplying the symbol estimates by a factor less than unity in the early stages of cancellation, the performance of parallel cancellation can be improved relative to full ("brute force") cancellation. In this paper we analyze the improvement of parallel cancellation when using partial cancellation, and provide additional insight into the gains. Specifically, we show that the decision statistic is biased when linear (soft) estimates of the symbol or channel are used for cancellation. Partial cancellation improves the performance in this case by reducing the decision statistic bias. View full abstract»

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  • Corrections to "Detection of Errors Recovered by Decoders for Singal Quality Estimation on Rain Faded AWGN Satellite Channels"

    Publication Year: 1999 , Page(s): 784
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (22 KB)  

    First Page of the Article
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  • Abstracts of forthcoming manuscripts

    Publication Year: 1999 , Page(s): 785 - 786
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    Freely Available from IEEE
  • Spectral efficiency of CDMA systems with linear MMSE interference suppression

    Publication Year: 1999 , Page(s): 722 - 731
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    Code-division multiple-access is a promising technique for communication systems. Many demodulation schemes have been proposed which take account of inherent multiple-access interference. In this paper, linear interference suppression as proposed by for example Madhow and Honig (194), is compared with conventional demodulation based on power-bandwidth plane. This approach is much more general than the comparison of error rates for specific scenarios as used previously. In case of interference suppression, the spectral efficiency is calculated by a combination of analysis and simulation. The coding and modulation scheme used is characterized within the power-bandwidth plane for a single-cell scenario as well as for a cellular system. In the latter case, some statements which are valid for the single-cell scenario have to be revised View full abstract»

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  • Performance analysis of wireless broadband systems employing optical fiber links

    Publication Year: 1999 , Page(s): 715 - 721
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (124 KB)  

    This paper reports an analysis of the performance of wireless broadband communication systems employing fiber-optic links to connect the base station with the control station. Rainfall attenuation on the radio link, and nonlinear distortions arising from the direct modulation of the laser source, besides the noise contributions coming out from both the optical transmitter and receiver, are considered in the analysis. As far as the radio link is concerned, the outage probability, due to the rainfall attenuation, is recounted for relevant cases; while, concerning the optical link, several carrier-to-noise ratio curves versus the optical modulation index of the channels are reported, varying different system parameters. With respect to the previous literature, a complete analysis of the optical link performance, in this type of systems, has been accomplished by taking into account, simultaneously, all the effects influencing the performance View full abstract»

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  • Performance study of a maximum-likelihood receiver for FFH/BFSK systems with multitone jamming

    Publication Year: 1999 , Page(s): 766 - 772
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    We derive the optimum structure of a maximum-likelihood (ML) receiver for a fast frequency-hopped binary frequency-shift-keying (FFH/BFSK) spread-spectrum (SS) communication system operating in the presence of multitone jamming (MTJ) and additive white Gaussian noise (AWGN). It is shown that the side information of noise variance, signal tone amplitude, and multiple interfering tone amplitude at each hop, as well as the computation of nonlinear modified Bessel function are required to implement the optimum ML receiver. We have also derived and analyzed two suboptimum receivers-namely, the ML-I and ML-II receivers-for large and small signal-to-noise ratio (SNR), respectively. Performance comparisons among various receivers show that the ML receiver gives the best performance, while the ML-I and ML-II receivers also outperform the other existing methods under both high and low SNR conditions View full abstract»

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  • Optimal multicast trees in communication systems with channel capacities and channel reliabilities

    Publication Year: 1999 , Page(s): 662 - 663
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (44 KB)  

    Given a source node and a set of destination nodes in a communication system in which there is associated with each channel a channel capacity and a channel reliability, an efficient algorithm is developed for computing a multicast tree which maximizes the capacity with reliability not less than a given threshold View full abstract»

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  • On low complexity stack decoding of convolutional codes

    Publication Year: 1999 , Page(s): 648 - 652
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB)  

    This article presents techniques for improving the distribution of the number of stack entries, for stack sequential decoding over a hard quantized channel, with emphasis on high rate codes. It is shown that, for a class of high rate b/(b+1) codes, a table-based true high rate approach can be easily implemented for obtaining a decoding advantage over the punctured approach. Modified algorithms, which significantly improve the distribution of the number of stack entries and decoding time, are proposed for rate 1/N codes and high rate b/(b+1) codes View full abstract»

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  • Pilot signals improve the performance of a Reed-Solomon errors and erasures decoder in Rayleigh fading channels

    Publication Year: 1999 , Page(s): 689 - 696
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    Errors and erasures decoding has the capability to improve the performance of a Reed-Solomon decoder if each error location is correctly identified, or “flagged”, and is considered as an erasure. However, the erasure flagging must be extremely reliable. In this paper, we present a new way to flag erasures, based on the side information provided by pilot signals. We derive a Bayesian method for optimum character erasure flagging, using both the received data signals and the channel estimates provided by pilot signals, and we present a simpler method which flags erasures on a modulation symbol basis. The simulation results demonstrate that the method results in significant transmit power savings compared to errors-only decoding View full abstract»

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  • Signaling constellations for fading channels

    Publication Year: 1999 , Page(s): 703 - 714
    Cited by:  Papers (66)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    The performance of various coherent 8-ary and 16-ary modulations in additive white Gaussian noise (AWGN) and slowly fading channels are analyzed. New expressions for the exact symbol error rates (SER) in fading with diversity combining are derived for any two-dimensional signaling format having polygonal decision boundaries. Maximal ratio combining, equal gain combining, and selection combining are considered. The SER formulas obtained make it possible for the first time to optimize parameters of various constellations precisely and to determine,which constellation has the lowest probability of error. For example, a star constellation such as that specified in the CCITT V.29 standard can be improved by adjusting the amplitude ratios of the points in the constellation to save about 0.63 dB power in AWGN without sacrificing the phase error tolerance, while maintaining the same error rate. The sensitivity of each constellation to phase error is presented and comparisons are made. Six 8-ary signal sets and 11 16-ary signal sets are examined using the new symbol error probability formulas to determine best signal sets for fading channels View full abstract»

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  • A comparison of slow-frequency-hop and direct-sequence spread-spectrum communications over frequency-selective fading channels

    Publication Year: 1999 , Page(s): 732 - 741
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    Spread-spectrum modulation can provide protection from the selective fading that is typically encountered in mobile radio networks. Because the methods of combating frequency-selective fading are quite different for slow-frequency-hop (SFH) and direct-sequence (DS) spread spectrum systems, these two types of modulation perform very differently. The purpose of this paper is to compare the performance of SFH and DS systems under identical conditions for several models of the wide-band fading channel. Each system has the same bandwidth, transmits over the same frequency-selective Gaussian wide-sense-stationary uncorrelated-scattering channel, and uses error-correction coding to combat thermal noise and fading. The probability of bit error at the output of the decoder is determined for each system by a combination of analysis and simulation. Results are presented for systems with a single transmitter-receiver pair and for networks with multiple simultaneous transmissions (i.e., multiple-access communications). The multiple-access network is distributed, so that control of power by a central terminal, such as a base station, is not possible. The results illustrate the tradeoffs in performance between SFW and DS spread-spectrum systems as a function of the parameters of the signals and the channel model. The performance of the SFH system is shown to be less sensitive to the exact characterization of the channel delay spectrum than the DS system. For most of the channels considered in this paper, SFH spread spectrum gives better performance than DS spread spectrum View full abstract»

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  • Impact of the combined slow and fast fading channel characteristics on the symbol error probability for multipath dispersionless channel characterized by a small number of dominant paths

    Publication Year: 1999 , Page(s): 653 - 657
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    New analytical expressions for the symbol error probability of coherent M-PSK and noncoherent M-FSK in a nondispersive channel modeled by a combination of POCA and log-normal statistics are derived. The POCA-Ln model is shown to be more general than other known models, such as the Suzuki (1977) model, as it can be applied in any environment with a small number of dominant propagation paths View full abstract»

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  • Generic error probabilities

    Publication Year: 1999 , Page(s): 697 - 702
    Cited by:  Papers (29)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    This paper presents new forms for an error probability associated, with the phase angle between two vectors perturbed by Gaussian noise. An interesting consequence of the underlying generic form is a new expression for the symbol error rate in MDPSK that is very similar to its counterpart for MPSK. The generic error probability is further shown to contain as special cases MPSK, MDPSK, CPFSK, and digital FM; and to give a new expression for the Marcum Q-function. The generic error probability also simplifies the error probability expressions in other situations such as nonorthogonal signaling, maximum likelihood differential detection of DPSK with block-by-block detection, and Gray coding of MDPSK View full abstract»

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  • Digital phase-locked loops tracked by a relay sensor

    Publication Year: 1999 , Page(s): 667 - 669
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (80 KB)  

    An optimal algorithm is presented for tracking the phase of a slowly modulating signal by means of digital sampling of its sign. Error bounds and a numerical illustration are given View full abstract»

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  • An extension of pulse shaping filter theory

    Publication Year: 1999 , Page(s): 645 - 647
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (72 KB)  

    The article presents a simple alternative approach to pulse shaping filters with ISI-free matched (white noise case) and unmatched filter properties. A Nyquist (1928) 1 filter in closed form is proved to be ISI-free with or without matched filtering when its complex transfer function is derived from an initially given Nyquist 1 filter. The simplicity of the application of this procedure is illustrated by an example View full abstract»

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  • Reduced complexity iterative decoding of low-density parity check codes based on belief propagation

    Publication Year: 1999 , Page(s): 673 - 680
    Cited by:  Papers (271)  |  Patents (50)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    Two simplified versions of the belief propagation algorithm for fast iterative decoding of low-density parity check codes on the additive white Gaussian noise channel are proposed. Both versions are implemented with real additions only, which greatly simplifies the decoding complexity of belief propagation in which products of probabilities have to be computed. Also, these two algorithms do not require any knowledge about the channel characteristics. Both algorithms yield a good performance-complexity trade-off and can be efficiently implemented in software as well as in hardware, with possibly quantized received values View full abstract»

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  • DSA: a distributed sample-based fast DS/CDMA acquisition technique

    Publication Year: 1999 , Page(s): 754 - 765
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    We propose a new acquisition scheme called distributed sample acquisition (DSA) which is applicable to the direct-sequence code-division multiple-access (DS/CDMA) system with a long-period pseudonoise (PN) sequence. The proposed scheme lays its foundations on an auxiliary PN sequence called the igniter sequence, which has relatively short period, and the distributed sample scrambling (DSS) technique previously developed for the asynchronous transfer mode cell transmission. In the DSA scheme, acquisition is done in three steps. First, the igniter sequence is synchronized, which normally takes a very short time due to its short period. Second, the state samples of the long-period PN sequence generator in the transmitter, which are conveyed to the receiver over the igniter sequence stream, are determined out of the synchronized igniter sequence. Third, the long-period PN sequence is synchronized by applying the state samples to the DSS receiver. Since the operation of each step takes a very short time, the overall acquisition is done very quickly. We analyze the acquisition time performance of the proposed scheme by taking the transform domain approach, confirming that the resulting mean acquisition time is dramatically reduced. If compared with the existing serial-search scheme, the DSA scheme can perform acquisition about 100 times faster when the period of the PN sequence is 215-1. None the less, the additional circuit complexity for its implementation is very small View full abstract»

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  • Adaptive nonlinear filters for narrow-band interference suppression in spread-spectrum CDMA systems

    Publication Year: 1999 , Page(s): 742 - 753
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    This paper presents a novel nonlinear filter and parameter estimator for narrow band interference suppression in code division multiple access spread-spectrum systems. As in the article by Rusch and Poor (1994), the received sampled signal is modeled as the sum of the spread-spectrum signal (modeled as a finite state independently identically distributed (i.i.d.) process-here we generalize to a finite state Markov chain), narrow-band interference (modeled as a Gaussian autoregressive process), and observation noise (modeled as a zero-mean white Gaussian process). The proposed algorithm combines a recursive hidden Markov model (HMM) estimator, Kalman filter (KF), and the recursive expectation maximization algorithm. The nonlinear filtering techniques for narrow-band interference suppression presented in Rusch and Poor and our proposed HMM-KF algorithm have the same computational cost. Detailed simulation studies show that the HMM-KF algorithm outperforms the filtering techniques in Rusch and Poor. In particular, significant improvements in the bit error rate and signal-to-noise ratio (SNR) enhancement are obtained in low to medium SNR. Furthermore, in simulation studies we investigate the effect on the performance of the HMM-KF and the approximate conditional mean (ACM) filter in the paper by Rusch and Poor, when the observation noise variance is increased. As expected, the performance of the HMM-KF and ACM algorithms worsen with increasing observation noise and number of users. However, HMM-KF significantly outperforms ACM in medium to high observation noise View full abstract»

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  • Pilot-aided coherent uplink for mobile satellite CDMA networks

    Publication Year: 1999 , Page(s): 773 - 783
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    A pilot-aided coherent uplink transmission scheme is proposed for mobile satellite communications at L-band. The scheme is designed to enhance link performance as compared to coded noncoherent M-ary orthogonal modulation, while maintaining small envelope fluctuations and low complexity. A rigorous analysis is performed for the proposed technique, when used in conjunction with a direct-sequence code-division multiple-access convolutionally encoded binary phase shift keying link, in a Rice-fading channel with satellite diversity. The pilot-aided scheme has been extensively simulated, accounting for finite interleaving in slow fading and nonideal carrier frequency recovery. The results show a significant performance gain with respect to noncoherent schemes designed for similar links, which goes up to 1.8 dB for 9.6 kb/s services with slow moving users exploiting dual-satellite diversity View full abstract»

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  • On phase-locked loops and Kalman filters

    Publication Year: 1999 , Page(s): 670 - 672
    Cited by:  Papers (29)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (100 KB)  

    Driessen (1994) and Christiansen (1994) independently showed that for a specific dynamic model, the proportional-integral phase-locked loop (PLL) has the same structure as the Kalman filter. In this paper, closed-form expressions of the corresponding Kalman gain values are derived both in acquisition and tracking modes of the PLL View full abstract»

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  • On the effect of imperfect interleaving for the Gilbert-Elliott channel

    Publication Year: 1999 , Page(s): 681 - 688
    Cited by:  Papers (48)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    By using the Gilbert-Elliott (1960, 1963) model to study the performance of block-coded transmission over the land mobile channel, a new analytical expression illustrating the effect of various parameters, e,g., mobile speed, delay constraint, and parameters for the error correcting code, is found. Comparisons between the results obtained by this analytical expression and results obtained by computer simulations show that the analytical results are accurate for a broad range of channel parameters. The Gilbert-Elliott model is then used to compare the performance of different binary BCH codes when the delay constraint does not allow the assumption of infinite interleaving. In contrast to the memoryless case, where the performance typically is improved with increased block length, short codes are found to be as good, or even superior, due to the fact that the interleaver works better for shorter codes View full abstract»

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  • Symbol and superbaud timing recovery in multi-h continuous-phase modulation

    Publication Year: 1999 , Page(s): 664 - 666
    Cited by:  Papers (4)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (88 KB)  

    This paper is concerned with the estimation of two synchronization parameters that play a key role in multi-h continuous-phase modulation receivers-the ordinary symbol timing phase and the so-called superbaud timing phase. The recovery of symbol and superbaud timing is implemented by means of feedforward nondata-aided algorithms. The novelty of the proposed method is that it can be applied to any modulation format, either full or partial response, with binary or multilevel symbols and with arbitrary modulation indices 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