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Communications, IEEE Transactions on

Issue 1 • Date Jan 1996

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Displaying Results 1 - 18 of 18
  • A product-coded WDM coding system

    Publication Year: 1996 , Page(s): 43 - 46
    Cited by:  Papers (1)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    Forward error correction is a feasible approach for reducing the bit error floor of lightwave systems, arising from the fact that a simple single-error-correcting code can reduce the error floor from O(P e) to O(Pe2). We propose a novel wavelength demultiplexer (WDM) coding system using a product code to improve the performance of WDM systems with an error floor caused by fiber dispersion or system noise View full abstract»

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  • Average external interference in cellular radio CDMA systems

    Publication Year: 1996 , Page(s): 23 - 25
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    An analytical and numerical evaluation by Gilhoussen et. al.(see IEEE Trans. Veh. Technol, vol.40, no.2, p.303-3121, 1991) of the capacity of a cellular radio CDMA system has been proposed. This evaluation has shown the interest of using spread spectrum techniques in the area of cellular radio systems. However, considering the computations made by Gilhoussen et. al. for the reverse link, we note the following: the calculations lead at a given moment to the evaluation of the average external interference for which a quantity is claimed only intuitively to be an upper bound. We construct a sequence of approximations for the average external interference, where the average external interference is the sequence limit. The claimed upper bound of Gilhoussen is also the first element of this sequence of approximations. We show by numerical means that the sequence is decreasing which justifies the claim of Gilhoussen View full abstract»

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  • Phase and frequency estimation for PSK packets: bounds and algorithms

    Publication Year: 1996 , Page(s): 26 - 28
    Cited by:  Papers (45)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    New Cramer-Rao lower bounds (CRBs) are derived for the estimation of phase offset, and frequency offset, from a block of random BPSK or QPSK symbols at low signal-to-noise (SNR) ratios. These bounds are compared to existing bounds which apply to the unmodulated carrier (or to known PSK symbols), and to the performance of some estimation algorithms View full abstract»

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  • Optimum finite-length equalization for multicarrier transceivers

    Publication Year: 1996 , Page(s): 56 - 64
    Cited by:  Papers (156)  |  Patents (69)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (844 KB)  

    A new criterion for partially-equalizing severe ISI channels to reduce the cyclic prefix overhead of the discrete multitone (DMT) transceiver, assuming a fixed transmission bandwidth, is introduced. The equalized DMT is shown to recover a significant portion of the performance loss incurred because of the use of a moderate-size FFT in the DMT to reduce latency and implementation cost. In particular, equalizers designed using our new criterion result in a higher DMT performance margin than traditional mean-square-error DMT equalizers. Finally, additional promising methods that further enhance the performance of the equalized DMT are investigated View full abstract»

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  • A new approach for evaluating the performance of a symbol timing recovery system employing a general type of nonlinearity

    Publication Year: 1996 , Page(s): 29 - 33
    Cited by:  Papers (21)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    A new technique is presented for evaluating the jitter performance of a symbol timing recovery (STR) subsystem for digital data transmission systems. The STR system consists of any even-symmetric zero-memory nonlinear device followed by a narrowband filter tuned to the pulse repetition frequency. Exact analytical expressions are derived for the mean and the mean-square values of the timing wave, based on iterative computations of high-order moments of the input signal. Then, the root mean-square (RMS) jitter performance is determined as a function of various system parameters such as the power series expansion of the zero-memory nonlinear device, the rolloff factor of the input pulse shape, and the postfiltering. Finally, the numerical results obtained from some specific examples serve to illustrate several aspects of the timing recovery problem View full abstract»

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  • Determination of best shortened linear codes

    Publication Year: 1996 , Page(s): 1 - 6
    Cited by:  Papers (6)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    The quality of a block code is determined by its capability to protect data against undetectable errors and by the number of check bits that are required for that purpose. For a given number of check bits there are codes with optimum bit error detecting capability in shortened block lengths. These codes are determined and tabulated. The residual error characteristics of some of the tabulated codes are compared with those specified in ISO/CCITT or IEC standard data transmission protocols. For block lengths and bit error rates that are typical in process control applications, the residual error rate of the determined codes is more than six orders of magnitude smaller than that of codes specified by widely used standard transmission protocols View full abstract»

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  • A reduced Laplacian pyramid for lossless and progressive image communication

    Publication Year: 1996 , Page(s): 18 - 22
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    The Laplacian pyramid (LP) is appropriate for lossy image compression; conversely, the reduced-difference pyramid (RDP), having as many data as pixels, gives a better performance with lossless encoding. A reduced LP is designed by discarding the anti-aliasing filter and adopting a half-band interpolator, thus retaining three over four of the LP coefficients. Lossless coding outperforms both LP and RDP, especially when dealing with medical images View full abstract»

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  • Feasibility of adding a personal communications network to an existing fixed-service microwave system

    Publication Year: 1996 , Page(s): 76 - 83
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (796 KB)  

    This paper examines the feasibility of adding a personal communication network (PCN) to a frequency band which is already allocated to fixed-service microwave systems. To achieve this goal, spread spectrum techniques are used to spread narrowband PCN signals into wideband. The forward and reverse link performance of PCN users under the influence of the microwave system and the influence of PCN users on the microwave system are both examined. It is proven that spectrum sharing between the PCN network and microwave systems is indeed feasible. Although our analysis is done based upon the consideration of only one microwave system, it can be easily extended to allow the appearance of two or more microwave systems View full abstract»

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  • Buffered or unbuffered: a case study based on logd(N,e,p) networks

    Publication Year: 1996 , Page(s): 105 - 113
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    Two implementation styles (buffered and unbuffered) have been used for constructing multistage interconnection networks for ATM switching. Conventional studies have shown that an unbuffered network, while having a simpler design, produces a lower throughput than a buffered network. But most of these studies, based on the assumption that each cell is routed independently (i.e. per-cell routing), ignored the out-of-sequence transmission problem of a buffered network in a virtual-channel environment. One way to keep the packet sequence for a buffered network without adding additional hardware is to fix the path for each virtual channel. We compute the throughput of this approach in designing nonblocking networks and compare it with that of the unbuffered approach. The base of our comparison is logd(N,e,p) networks. The results show that a fixed-path-routing buffered network will have a throughput even lower than that of an unbuffered network View full abstract»

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  • Some block- and trellis-coded modulations for the Rayleigh fading channel

    Publication Year: 1996 , Page(s): 34 - 42
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1020 KB)  

    The error performance of a modulation code over a channel depends on several distance parameters and the path multiplicity of the code. For the AWGN channel, the error performance of a modulation code depends mainly on its minimum squared Euclidean distance and path multiplicity. For the Rayleigh fading channel, however, the error performance of a modulation code depends strongly on its minimum symbol distance, minimum product distance, and path multiplicity. It depends on the minimum squared Euclidean distance in a lesser degree. This paper is concerned with the construction of block and trellis MPSK modulation codes for the Rayleigh fading channel. In each construction, the distance parameters are chosen to achieve good error performance with reduced decoding complexity View full abstract»

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  • Joint clock recovery and baseband combining for the diversity radio channel

    Publication Year: 1996 , Page(s): 114 - 117
    Cited by:  Papers (2)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    Multipath fading is one of the major impairments encountered in terrestrial digital radio. A common countermeasure to limit the outage time due to multipath is the space diversity technique, which takes its effectiveness from the low correlation between the field samples of two well separated antennas. A very simple and effective blind receiver is proposed for the diversity radio channel. The novelty of the present study is the application of the constant modulus algorithm to joint clock recovery and baseband combining. The effectiveness of our proposal relies upon the synergic action of clock recovery and adaptive baseband combining, which allows optimal equalization of the two-ray diversity channel View full abstract»

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  • On the WMC density as an inverse Gaussian probability density

    Publication Year: 1996 , Page(s): 15 - 17
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    The probability density function (PDF) used to model the statistical behavior of avalanche photodiodes (APD), known as the Webb, McIntyre and Conradi (1974) WMC density, is shown to be an inverse Gaussian density. As a consequence, a closed-form solution for the cumulative distribution function exists. A closed-form for the cumulative distribution of the WMC PDF has not been presented in the literature before. With this result, alternate methods for the generation of WMC PDF distributed random variates are now available. These methods are reviewed and discussed View full abstract»

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  • Effects of fading and partial-band noise jamming on a fast FH/BFSK acquisition receiver with noise-normalization combination

    Publication Year: 1996 , Page(s): 94 - 104
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (960 KB)  

    We present the performance analysis of a fast frequency-hopped (FH) binary orthogonal frequency-shift keying acquisition receiver for communication against adverse environments. The receiver employs noncoherent, noise-normalized, matched-filtered (MF) correlation detection for rapid acquisition in the search mode. Our analysis includes four types of communication environments, namely additive white Gaussian noise (AWGN) channel, AWGN channel with partial-band noise jamming, fading channels, and fading channels with partial-band noise jamming. The considered fading channels include Nakagami-m, Rician, and Rayleigh amplitude models. Based on Beaulieu's (see ibid., vol.38, no.9, p.1463, 1990) convergent series approach, efficient analytical formulas are developed for performance evaluation. Example performance results for various environments are presented in terms of two acquisition probabilities, namely the detection probability and the false alarm probability of the noise-normalized MF detector. It is analytically shown that with a short MF correlation length and with a sufficiently large ratio of signal power to noise power the fast FH diversity combining yields noticeable performance improvement for environments with strong fading. When the MF correlation is lengthened, this improvement tends to fade away and the diversity combining results in performance loss View full abstract»

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  • Scarce-state-transition syndrome-former error-trellis decoding of (n,n-1) convolutional codes

    Publication Year: 1996 , Page(s): 7 - 9
    Cited by:  Papers (1)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    A novel scarce-state-transition (SST) type trellis decoding system for (n,n-1) convolutional codes with coherent BPSK signals is proposed. The new system retains the same number of binary comparisons as the syndrome-former trellis decoding technique. Like the original SST-type encoder trellis technique, the proposed system is also suitable for CMOS VLSI implementation. A combination of the two techniques results in a less complex and low power consumption decoding system View full abstract»

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  • Optimal finite duration pulses for OFDM

    Publication Year: 1996 , Page(s): 10 - 14
    Cited by:  Papers (79)  |  Patents (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    This paper presents pulses of finite duration for use in orthogonal frequency division multiplexing (OFDM) using offset QAM modulation. In such a system the pulses will overlap in both frequency and time without intersymbol or interchannel interference. The pulses are generated by an optimization procedure which minimizes the out-of-band energy under the constraints of zero intersymbol and interchannel interference. Low out-of-band energy is important to achieve high bandwidth efficiency, especially when the number of channels is small. The optimization procedure leads to an integral equation which is solved by expanding the pulse in truncated prolate spheroidal wave functions. Examples of optimized pulses and their spectrum are presented for lengths of 2 and 4 symbol intervals View full abstract»

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  • Propagation delay estimation in asynchronous direct-sequence code-division multiple access systems

    Publication Year: 1996 , Page(s): 84 - 93
    Cited by:  Papers (207)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (976 KB)  

    In an asynchronous direct-sequence code-division multiple access (DS-CDMA) communication system, the parameter estimation problem, i.e., estimating the propagation delay, attenuation and phase shift of each user's transmitted signal, may be complicated by the so-called near-far problem. The near-far problem occurs when the amplitudes of the users received signals are very dissimilar, as the case might be in many important applications. In particular, the standard method for estimating the propagation delays will fail in a near-far situation. Several new estimators, the maximum likelihood, an approximative maximum likelihood and a subspace-based estimator, are therefore proposed and are shown to be robust against the near-far problem. No knowledge of the transmitted bits is assumed, and the proposed estimators can thus be used for both acquisition and tracking. In addition, the Cramer-Rao bound is derived for the parameter estimation problem View full abstract»

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  • RMS bandwidth constrained signature waveforms that maximize the total capacity of PAM-synchronous CDMA channels

    Publication Year: 1996 , Page(s): 65 - 75
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1052 KB)  

    Optimum time-limited signal sets of equal and unequal energies are obtained under root mean square (RMS) bandwidth constraints. The total capacity and the total asymptotic efficiency of the PAM synchronous Gaussian CDMA (PSG-CDMA) channel are considered as the optimality criteria. The latter measure is monotonic with the determinant of the correlation matrix, R, and the former is monotonic with det(I+σ -2R), where σ2 represents the noise level. Average as well as maximum RMS bandwidth constraints are considered in the equal-energy case, and the energy-weighted RMS bandwidth constraint is considered for unequal energy signals. For the equal-energy problem, signal sets are found that simultaneously optimize the total asymptotic efficiency under both average and maximum RMS bandwidth constraints. For the total capacity measure, such simultaneously optimal signal sets are also obtained, albeit under the restriction that the number of signals n be a Hadamard matrix dimension. When the Hadamard dimension is in particular a power of two, we obtain optimum signal sets that are shown to yield equal optimum multiuser detector asymptotic efficiencies for all users of an uncoded PSG-CDMA channel. Unequal energy signal sets are also found under an energy-weighted RMS bandwidth constraint for both optimality criteria View full abstract»

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  • Variable-weight optical orthogonal codes for CDMA networks with multiple performance requirements

    Publication Year: 1996 , Page(s): 47 - 55
    Cited by:  Papers (48)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    An optical orthogonal code (OOC) is a family of (0,1) sequences with good auto- and cross-correlation properties; they are used as a means to obtain code division multiple access (CDMA) on fiber optic networks. Previous work on OOC has assumed that the weight of each codeword is the same. We consider codes when this assumption is removed. We develop bounds on the size of such “variable-weight” OOC's and demonstrate techniques to build them. Furthermore, we provide an analysis of the performance of variable-weight OOC in a CDMA network. Varying the weight of a user's signature sequence affects that user's performance; therefore this approach is useful for CDMA fiber optic networks with multiple performance requirements 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