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Communications, IEEE Transactions on

Issue 8 • Date Aug. 2003

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

    Publication Year: 2003 , Page(s): 1409
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    Freely Available from IEEE
  • Performance evaluation of a switch using priority-based dynamic capacity allocation scheme

    Publication Year: 2003 , Page(s): 1399 - 1408
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (857 KB) |  | HTML iconHTML  

    Performance-analysis of a switching system using priority-based dynamic capacity allocation is presented. The system provides connectivity between a number of point-to-multipoint communication access clusters. The scheduling of traffic transmission at each access cluster is based on a priority scheme with priority given to real-time (rt) traffic over nonreal-time (nrt) traffic. An analytical model is developed to evaluate the covariance functions of both rt and nrt traffic arriving at the output ports. Aggregate traffic arrival streams are approximated to 2-state Markov-modulated Poisson processes (MMPPs) by matching their statistical characteristics. Analytical and simulation results on performance of an example 4 × 4 switch for different traffic loads are discussed. View full abstract»

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  • Optimization of spatially adaptive reciprocal multipoint communication networks

    Publication Year: 2003 , Page(s): 1254 - 1257
    Cited by:  Papers (10)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (365 KB) |  | HTML iconHTML  

    A mathematical framework for a duplex multiple-input-multiple-output, multipoint network is presented and used to develop uplink and downlink network objective functions based on information theoretic "waterfilling" capacity arguments. It is shown that these objective functions possess equal local optima in reciprocal networks where the internode channel responses between uplink and downlink reception nodes are reciprocal, e.g., in time-division duplex networks. This mathematical framework can be used to develop locally enabled global optimization algorithms that use only local information available at each transceiver. A numerical experiment reveals an order-of-magnitude capacity improvement over conventional single-antenna systems, and/or a several-orders-of-magnitude improvement in required transmission power. View full abstract»

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  • Performance analysis of triple selection diversity over exponentially correlated Nakagami-m fading channels

    Publication Year: 2003 , Page(s): 1245 - 1248
    Cited by:  Papers (33)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (330 KB) |  | HTML iconHTML  

    An approach to the performance analysis of a triple selection-diversity system over exponentially correlated Nakagami-m fading channels is presented. Closed-form expressions of converged sums for both outage and average error probabilities are derived. Numerical results are presented to point out the effect of the fading correlation, the fading severity, as well as the improvement achieved by the triple selection combining compared with the corresponding dual diversity case. View full abstract»

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  • A new algorithm for "hard" iterative decoding of concatenated codes

    Publication Year: 2003 , Page(s): 1229 - 1232
    Cited by:  Papers (7)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB) |  | HTML iconHTML  

    A new hard iterative decoding algorithm to decode the serial concatenation of two block codes separated by an interleaver is presented. The new scheme is based on the use of erasures as a sort of extrinsic information to be exchanged between the two decoders. Extensive simulations highlight the coding gain of the new algorithm with respect to standard hard iterative decoding. View full abstract»

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  • Performance analysis of coded modulation with generalized selection combining in Rayleigh fading

    Publication Year: 2003 , Page(s): 1348 - 1357
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (653 KB) |  | HTML iconHTML  

    We consider coded modulation with generalized selection combining (GSC) for bandwidth-efficient-coded modulation over Rayleigh fading channels. Our results show that reception diversity with generalized selection combining can conveniently trade off system complexity versus performance. We provide a number of new results by calculating the cutoff rate, and by deriving analytical upper bounds on symbol-interleaved trellis-coded modulation (TCM) and bit-interleaved-coded modulation (BICM) with GSC. All are verified by simulation. We show that our new bounds on TCM with GSC, which includes maximum ratio combining and selection combining as special cases, are tighter than the previously derived bounds. A new asymptotic analysis on the pairwise error probability, which can be used as a guideline for designing coded modulation over GSC channels, is also given. Finally, we show that BICM with iterative decoding (BICM-ID) can achieve significant coding gain over conventional coded modulation in a multiple-receiving-antenna channel. View full abstract»

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  • Joint channel estimation and data detection in space-time communications

    Publication Year: 2003 , Page(s): 1266 - 1270
    Cited by:  Papers (69)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (403 KB) |  | HTML iconHTML  

    The paper considers joint channel estimation and data sequence detection for multipath radio channels with multiple antennas at the transmitter and/or receiver. An iterative space-time receiver based on the expectation-maximization algorithm is proposed. We examine the performance of this receiver for transmit diversity and space-time coding methods over Rayleigh fading channels. Simulation results show that the receiver can often achieve near-coherent performance with modest complexity and using very few pilot symbols. View full abstract»

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  • Performance bounds for coded free-space optical communications through atmospheric turbulence channels

    Publication Year: 2003 , Page(s): 1233 - 1239
    Cited by:  Papers (91)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (466 KB) |  | HTML iconHTML  

    Error-control codes can help to mitigate atmospheric turbulence-induced signal fading in free-space optical communication links using intensity modulation/direct detection (IM/DD). Error performance bound analysis can yield simple analytical upper bounds or approximations to the bit-error probability. We first derive an upper bound on the pairwise codeword-error probability for transmission through channels with correlated turbulence-induced fading, which involves complicated multidimensional integration. To simplify the computations, we derive an approximate upper bound under the assumption of weak turbulence. The accuracy of this approximation under weak turbulence is verified by numerical simulation. Its invalidity when applied to strong turbulence is also shown. This simple approximate upper bound to the pairwise codeword-error probability is then applied to derive an upper bound to the bit-error probability for block codes, convolutional codes, and turbo codes for free-space optical communication through weak atmospheric turbulence channels. We also discuss the choice of interleaver length in block codes and turbo codes based on numerical evaluation of our performance bounds. View full abstract»

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  • On the multivariate Nakagami-m distribution with exponential correlation

    Publication Year: 2003 , Page(s): 1240 - 1244
    Cited by:  Papers (83)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (397 KB) |  | HTML iconHTML  

    Capitalizing on the proof of a theorem presented by L.E. Blumenson and K.S. Miller (see Ann. Math. Statist., vol.34, p.903-10, 1963), we propose a useful closed formula for the exponentially correlated n-variate Nakagami-m probability density function. Moreover, an infinite series approach for the corresponding cumulative distribution function is presented. Bounds on the error resulting from the truncation of the infinite series are also derived. Finally, in order to check the accuracy of the proposed formulation, numerical results are presented. View full abstract»

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  • GMSK with limiter-discriminator detector in Nakagami fading channel with and without selection combining

    Publication Year: 2003 , Page(s): 1271 - 1273
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (302 KB) |  | HTML iconHTML  

    We derive an equation for the bit-error probability (BEP) of Gaussian minimum-shift keying with limiter discriminator detection in Nakagami-m fading channels including selection and switch-and-stay combining. We compute the BEP for various selections of system parameters. View full abstract»

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  • A simple and general parameterization quantifying performance in fading channels

    Publication Year: 2003 , Page(s): 1389 - 1398
    Cited by:  Papers (436)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB) |  | HTML iconHTML  

    We quantify the performance of wireless transmissions over random fading channels at high signal-to-noise ratio (SNR). The performance criteria we consider are average probability of:error and outage probability. We show that as functions of the average SNR, they can both be characterized by two parameters: the diversity and coding gains. They both exhibit identical diversity orders, but their coding gains in decibels differ by a constant. The diversity and coding gains are found to depend on the behavior of-the random SNR's probability density function only at the origin, or equivalently, on the decaying order of the corresponding moment generating function (i.e., how fast the moment generating function goes to zero as its argument goes to infinity). Diversity and coding gains for diversity combining systems are expressed in terms of the diversity branches' individual diversity and coding gains, where the branches can come from any diversity technique such as space, time, frequency, or, multipath. The proposed analysis offers a simple and unifying approach to evaluating the performance of uncoded and (possibly space-time) coded transmissions over fading channels, and the method applies to almost all digital modulation schemes, including M-ary phaseshift keying, quadrature amplitude modulation, and frequency-shift keying with coherent or noncoherent detection. View full abstract»

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  • Code acquisition in transmit diversity DS-CDMA systems

    Publication Year: 2003 , Page(s): 1378 - 1388
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (734 KB) |  | HTML iconHTML  

    In this paper, two code acquisition schemes are studied for use in conjunction with transmit diversity direct-sequence code-division multiple access (DS-CDMA). One is a training-based single-user maximum-likelihood (SUML) estimator, which can achieve code acquisition very fast at low computational complexity. The other is a blind estimator based on the multiple signal classification (MUSIC) algorithm. Two recently proposed transmit diversity schemes known as orthogonal transmit diversity simulcast (OTD-S) and space-time selective spreading transmit diversity (STSTD) are considered. While the advantages of transmit diversity from the detection standpoint are well known, less is known about how code acquisition performance is affected by the use of transmit diversity. Through the analysis in this paper, it is proven that the SUMI. estimator should give the same performance in both the OTD-S and STSTD schemes in a single-user environment. In a multiple-user environment, simulation results show that the STSTD system offers slightly better code acquisition performance. It is also seen that the SUML estimators provide significantly better code acquisition performance than the MUSIC estimators in either transmit diversity system. From the standpoint of robustness to carrier frequency offset, it Is found that the training-based SUML estimator is very sensitive to frequency offset, while the MUSIC estimator is quite robust. A simple frequency offset estimator to be used in conjunction with the SUML estimator is also proposed and is shown to make the timing estimator quite tolerant of substantial frequency offsets. View full abstract»

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  • Tight exponential upper bounds on the ML decoding error probability of block codes over fully interleaved fading channels

    Publication Year: 2003 , Page(s): 1296 - 1305
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (681 KB) |  | HTML iconHTML  

    We derive tight exponential upper bounds on the decoding error probability of block codes which are operating over fully interleaved Rician fading channels, coherently detected and maximum-likelihood decoded. It is assumed that the fading samples are statistically independent and that perfect estimates of these samples are provided to the decoder. These upper bounds on the bit and block error probabilities are based on certain variations of the Gallager bounds. These bounds do not require integration in their final version and they are reasonably tight in a certain portion of the rate region exceeding the cutoff rate of the channel. By inserting interconnections between these bounds, we show that they are generalized versions of some reported bounds for the binary-input additive white Gaussian noise channel. View full abstract»

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  • Adaptive channel partitioning and modulation for linear time-varying channels

    Publication Year: 2003 , Page(s): 1313 - 1324
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (789 KB) |  | HTML iconHTML  

    We present a novel channel partitioning and modulation technique for linear time-varying (LTV) channels using adaptive bases of localized complex exponentials. We show that localized complex exponentials are approximate eigenfunctions of underspread LTV channels. A basis of localized complex exponentials that approximately diagonalizes the LTV channel is selected adaptively by the receiver during a training period. The basis selection process is equivalent to matching the support intervals of the localized complex exponentials to the rate of the channel time variation. The receiver sends information regarding the selected basis to the transmitter which modulates the subsequent data stream in this basis. The adaptive modulation technique performs significantly better than conventional orthogonal frequency-division multiplexing systems for rapidly varying LTV channels such as time-frequency-selective mobile radio channels. View full abstract»

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  • Soft decoding in optical systems

    Publication Year: 2003 , Page(s): 1258 - 1265
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (487 KB) |  | HTML iconHTML  

    We consider the application of concatenated codes with interleaver and iterative decoding to optical communication systems. We show how to obtain the optimum log-likelihood ratio to be provided to the soft decoder in the optical channel environment, and compare the performance of a decoder using it with the one employing a Gaussian approximation of the optical channel. Simulation results refer to practical turbo-product codes, and encompass the effect of quantization on the log-likelihood ratio. The results show that the Gaussian assumption in computing the log-likelihood ratio for the optical channel leads to significant losses. View full abstract»

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  • Design of serial concatenated MSK schemes based on density evolution

    Publication Year: 2003 , Page(s): 1283 - 1295
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (763 KB) |  | HTML iconHTML  

    We consider the design of convolutional codes and low density parity check (LDPC) codes with minimum-shift keying (MSK) when the receiver employs iterative decoding and demodulation. The main idea proposed is the design of coded schemes that are well matched to the iterative decoding algorithm being used rather than to hypothetical maximum-likelihood decoding. We first show that the design is crucially dependent on whether the continuous phase encoder (CPE) is realized in recursive form or in nonrecursive form. We then consider the design of convolutionally coded systems and low density parity check codes with MSK to obtain near-capacity performance. With convolutional codes, we show that it is possible to improve the performance significantly by using a mixture of recursive and nonrecursive realizations for the CPE. For low density parity check codes, we show that codes designed for binary phase shift keying are optimal for MSK only if the nonrecursive realization is used; for the recursive realization, we design new LDPC codes based on the concept of density evolution. We show that these codes outperform the best known codes for MSK and have lower decoding complexity. View full abstract»

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  • Iterative threshold decoding without interleaving for convolutional self-doubly orthogonal codes

    Publication Year: 2003 , Page(s): 1274 - 1282
    Cited by:  Papers (29)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (765 KB) |  | HTML iconHTML  

    A novel iterative error control technique based on the threshold decoding algorithm and new convolutional self-doubly orthogonal codes is proposed. It differs from parallel concatenated turbo decoding as it uses a single convolutional encoder, a single decoder and hence no interleaver, neither at encoding nor at decoding. Decoding is performed iteratively using a single threshold decoder at each iteration, thereby providing good tradeoff between complexity, latency and error performance. View full abstract»

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  • Analysis of a type II hybrid ARQ strategy in a DS-CDMA packet transmission environment

    Publication Year: 2003 , Page(s): 1249 - 1253
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (327 KB) |  | HTML iconHTML  

    A type II hybrid automatic repeat request scheme is considered as a retransmission strategy in a direct-sequence code-division multiple-access packet mobile radio network. An analysis based on equilibrium point analysis is presented to model the behavior of the system in a message-based traffic generation model. A simulation approach is introduced to validate the proposed analytical model, obtaining results that closely match those derived theoretically. View full abstract»

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  • Large-system performance of iterative multiuser decision-feedback detection

    Publication Year: 2003 , Page(s): 1368 - 1377
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (651 KB) |  | HTML iconHTML  

    The large-system performance of iterative multiuser decision-feedback detectors (DFDs) is studied for synchronous coded direct-sequence code-division multiple access. Both successive and parallel demodulation of users are considered. The filters are optimized according to the minimum mean-squared error criteria, assuming perfect feedback. We first consider Viterbi decoding with hard decision feedback, and compute union bounds on the large-system error rate. We then consider maximum a posteriori (MAP) decoding with soft decision feedback, and evaluate the error rate semianalytically by assuming the log-likelihood ratios computed by the MAP decoder are Gaussian random variables. Performance is studied numerically as a function of noise level, spectral efficiency, and code rate. Results show that soft decision feedback gives substantial gains relative to hard decision feedback. At moderate spectral efficiencies (users divided by bandwidth expansion less than 0.9), the iterative DFDs with soft decision feedback based on a posteriori probabilities can achieve near-single-user performance at an Eb/N0 close to the large-system capacity bound. View full abstract»

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  • Iterative decoding and channel estimation for space-time BICM over MIMO block fading multipath AWGN channel

    Publication Year: 2003 , Page(s): 1358 - 1367
    Cited by:  Papers (27)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (597 KB) |  | HTML iconHTML  

    In this paper, we consider a generic model of space-time bit-interleaved coded modulation (ST-BICM) on a multiple-input multiple-output (MIMO) Rayleigh fading multipath channel. A practical low-complexity receiver structure performing iteratively MIMO data detection, channel decoding and channel estimation, is presented. The MIMO data detection, employing a reduced-state list-type soft output Viterbi algorithm enables to cope with severe channel intersymbol interference (ISI) without MIMO prefiltering. Among other results, simulations show that our approach can dramatically improve the downlink performance of time-division multiple access (TDMA) systems with high order modulation, keeping a reasonable complexity at the receiver side. View full abstract»

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  • Multislot estimation of frequency-selective fast-varying channels

    Publication Year: 2003 , Page(s): 1337 - 1347
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (756 KB) |  | HTML iconHTML  

    In mobile communications, the movement of terminals renders the multipath channel time varying. Even though the faded amplitudes are fast varying, the delays can be considered as stationary on a large temporal scale. We propose a new subspace-based method that estimates the channel response from multiple slots by capitalizing on these different varying rates without explicitly computing the delays of the multipath. The temporal subspace is obtained from multiple single-slot training-based estimates of the (single-user or multiuser) channel response. Provided that the number of slots is large enough, the time basis can be calculated with some accuracy. As a consequence, the mean-square error of the channel response depends only on the number of fast-varying parameters that have to be estimated in a slot-by-slot fashion. Performance analysis and simulations confirm the expected benefits of the multislot approach in improving the efficiency of systems with short training sequences. View full abstract»

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  • Adaptive Bayesian and EM-based detectors for frequency-selective fading channels

    Publication Year: 2003 , Page(s): 1325 - 1336
    Cited by:  Papers (23)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (667 KB) |  | HTML iconHTML  

    The problems of adaptive maximum a posteriori (MAP) symbol detection for uncoded transmission and of adaptive soft-input soft-output (SISO) demodulation for coded transmission of data symbols over time-varying frequency-selective channels are explored within the framework of the expectation-maximization (EM) algorithm. In particular, several recursive forms of the classical Baum-Welch (BW) algorithm and its Bayesian counterpart (often referred to a Bayesian EM algorithm) are derived in an unified way. In contrast to earlier developments of the BW and BEM algorithms, these formulations lead to computationally attractive algorithms which avoid matrix inversions while using sequential processing over the time and trellis branch indices. Moreover, it is shown how these recursive versions of the BW and BEM algorithms can be integrated with the well-known forward-backward processing SISO algorithms resulting in adaptive SISOs with embedded soft decision directed (SDD) channel estimators. An application of the proposed algorithms to iterative "turbo-processing" receivers illustrates how these SDD channel estimators can efficiently exploit the extrinsic information obtained as feedback from the SISO decoder in order to enhance their estimation accuracy. View full abstract»

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  • A new chaotic secure communication system

    Publication Year: 2003 , Page(s): 1306 - 1312
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB) |  | HTML iconHTML  

    The paper proposes a digital chaotic secure communication by introducing a magnifying glass concept, which is used to enlarge and observe minor parameter mismatch so as to increase the sensitivity of the system. The encryption method is based on a one-time pad encryption scheme, where the random key sequence is replaced by a chaotic sequence generated via a Chua's circuit. We make use of an impulsive control strategy to synchronize two identical chaotic systems embedded in the encryptor and the decryptor, respectively. The lengths of impulsive intervals are piecewise constant and, as a result, the security of the system is further improved. Moreover, with the given parameters of the chaotic system and the impulsive control law, an estimate of the synchronization time is derived. The proposed cryptosystem is shown to be very sensitive to parameter mismatch and hence the security of the chaotic secure communication system is greatly enhanced. View full abstract»

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Aims & Scope

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

 

 

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Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia