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Communications, IEEE Transactions on

Issue 3 • Date March 1997

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Displaying Results 1 - 19 of 19
  • Comment on "Maximum likelihood decoding of uncoded and coded PSK signal sequences transmitted over Rayleigh flat-fading channels"

    Publication Year: 1997
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (13 KB)  

    This comment points out some papers published before the paper of Vitetta and Taylor (see ibid., vol.43, no.11, p.2750-58, 1995). These early papers have dealt with the general problem of maximum-likelihood sequence estimation of coded/uncoded phase-shift keying (PSK) and quadrature amplitude modulation (QAM) signals in correlated Rician and Rayleigh-fading channels. These publications did not assume use of interleaving or use of optimal codes, designed for interleaved systems. The statistical properties of the multiplicative fading process have been included in the design of the receivers which were proposed, analyzed, and evaluated. The research contributions documented in these papers have also shown for the first time in the open literature the link between conventional detection techniques and the maximum-likelihood detection of signals in this type of fading channels. View full abstract»

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  • Probability of error for equal-gain combiners over Rayleigh channels: some closed-form solutions

    Publication Year: 1997 , Page(s): 270 - 273
    Cited by:  Papers (77)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    The probability of error of a general equal-gain combiner (EG) in closed form is not available in the literature. By formulating the problem in the framework of signal detection and evaluating the probability of error directly from the characteristic function (CF) of the signal at the combiner output, we obtain closed-form solutions for the probability of error of the EG combiner with two or three branches operating over a Rayleigh-fading channel View full abstract»

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  • Performance of coherent ASK lightwave systems with finite intermediate frequency

    Publication Year: 1997 , Page(s): 344 - 351
    Cited by:  Papers (3)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    The impact of finite intermediate frequency (IF) on the performance of heterodyne ASK lightwave systems is examined and quantified in the presence of laser phase noise and shot noise. For negligible linewidths, it is shown that certain finite choices of IF (R b,3Rb/2,2Rb,5Rb/2, etc.) lead to the same ideal bit-error-rate (BER) performance as infinite choices of IF. Results indicate that for negligible linewidths the worst case sensitivity penalty is 0.9 dB for proper heterodyne detection and occurs when fIF=1.25 Rb. For nonnegligible linewidths (e.g., when ΔνT⩾0.04) the sensitivity penalty is always less than 0.9 dB for finite choices of IF. The analysis presented does lead to a closed-form signal-to-noise ratio (SNR) expression at the decision gate of the receiver which can readily be used for BER and sensitivity penalty computations. The SNR expression provided includes all the key system parameters of interest such as system bit rate (Rb), the peak IF SNR (ξ), laser linewidth (Δν), and the IF filter expansion factor (α). The findings of this work suggest that the number of channels in a multichannel heterodyne ASK lightwave system can be increased substantially by properly choosing a small value for the IF at the expense of a small penalty <1 dB. On the negative side, IF frequency stabilization becomes a more critical requirement in multichannel systems employing small values of IF View full abstract»

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  • Combined equalization and differential detection using precoding

    Publication Year: 1997 , Page(s): 274 - 278
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (108 KB)  

    A new transceiver for data transmission over multipath fading channels employing precoding and differential detection is investigated. This precoding scheme effectively functions as a decision feedback equalizer (DFE) for differentially coherent demodulation. The main advantage of the proposed scheme over the conventional DFE is its ability to compensate for fast channel phase variations View full abstract»

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  • A family of pure digital signal processing bit synchronizers

    Publication Year: 1997 , Page(s): 289 - 292
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

    A sample-correlate-choose-largest (SCCL) algorithm is generalized to design a family of efficient baseband digital signal processing (DSP) bit synchronizers. The common feature among maximal likelihood, minimal likelihood, and zero crossing in designing SCCL type DSP bit synchronizers gives us a possible unified point of view in the general design of synchronizers. Optimal signal waveform of “+---” and “-+++” has been derived for this family of bit synchronizers under the signal bandwidth constraint of four times bit rate along with the performance analysis View full abstract»

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  • An algebraic approach to the unequal-spaced channel-allocation problem in WDM lightwave systems

    Publication Year: 1997 , Page(s): 352 - 359
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    To reduce four-wave-mixing crosstalk in high-capacity, long-haul, repeaterless, wavelength-division multiplexing (WDM) lightwave systems, the use of unequally spaced channels has been proposed. Instead of being solved by integer linear programming, the unequal-spaced channel-allocation problem is treated by constructing suitable optical orthogonal codes in optical code-division multiple-access (CDMA). An “algebraic” framework and three algorithms on finding the frequency locations of unequally spaced WDM channels are introduced, where the constructions are based on generating optical CDMA codewords with a predetermined pulse separation and “aperiodic” autocorrelation sidelobes no greater than one. The algorithms potentially provide a fast and simple alternative to solve the problem, besides the proposed computer-search method View full abstract»

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  • Complex spreading sequences with a wide range of correlation properties

    Publication Year: 1997 , Page(s): 365 - 375
    Cited by:  Papers (66)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    This paper presents a new family of complex valued pseudo-random sequences for use in coded multiple access communication systems. The family offers a very wide range of values for both auto-correlation (AC) and cross-correlation (CC) functions, allowing great flexibility in the selection of characteristics of sequence sets. Based on the measure described in this paper for the mean-square aperiodic AC and CC values of a set of sequences, the correlation properties of sets of these sequences are compared to well-known sequence sets, and it is shown that sets from the new family of sequences have superior qualities. Tables of parameters for various sequence sets are presented to enable the construction and comparison of sets from this new family View full abstract»

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  • Comparison of precoding schemes for digital subscriber lines

    Publication Year: 1997 , Page(s): 334 - 343
    Cited by:  Papers (15)  |  Patents (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    Precoding at the transmitter side is a practicable method for transmission over intersymbol interference channels. In contrast to decision-feedback equalization no error propagation occurs and coded modulation can be applied as for the intersymbol interference free channel. Tomlinson-Harashima (1971, 1972) precoding and flexible precoding are analyzed and compared. The dualities and differences are discussed. The focus of interest is the application of precoding to fast digital transmission over twisted pair lines, such as high-rate or asymmetric digital subscriber lines. It turns out that flexibility-which is not necessary in the specific application, digital subscriber lines-of flexible precoding is paid with a performance loss compared to Tomlinson-Harashima precoding View full abstract»

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  • Cycle slip in clock recovery on frequency-selective fading channels

    Publication Year: 1997 , Page(s): 376 - 383
    Cited by:  Papers (5)  |  Patents (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    The mechanism and fundamental nature of the “cycle slip phenomenon” in clock recovery, which triggers the occurrence of burst-type irreducible errors in frequency-selective fading conditions, are theoretically clarified for PSK transmission systems with a coherent detection scheme. The appropriateness of the theory is identified through measurement by means of a fading simulator and a 64 kb/s QPSK modem. Moreover, a simple formula for predicting the frequency of cycle slip occurrence in Rayleigh-fading environments is developed, the accuracy of which is confirmed by means of computer simulation View full abstract»

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  • Performance of MHPM in Rician and Rayleigh fading mobile channels

    Publication Year: 1997 , Page(s): 279 - 283
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    This paper evaluates the error probability of the rectangular frequency pulse multi-h modulation (MHPM) scheme in slowly-fading, frequency-nonselective or frequency-selective Rician and Rayleigh channels. The evaluation is performed with a method combining analysis and computer simulation. Performance degradations are evaluated for various direct-to-reflected signal ratio, Doppler shifts, and relative time delays in Rician fading channels. Compared with minimum shift keying (MSK), MHPM schemes appear to have retained their coding gains View full abstract»

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  • Sequence estimation in the presence of random parameters via the EM algorithm

    Publication Year: 1997 , Page(s): 300 - 308
    Cited by:  Papers (131)  |  Patents (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    The expectation-maximization (EM) algorithm was first introduced in the statistics literature as an iterative procedure that under some conditions produces maximum-likelihood (hit) parameter estimates. In this paper we investigate the application of the EM algorithm to sequence estimation in the presence of random disturbances and additive white Gaussian noise. As examples of the use of the EM algorithm, we look at the random-phase and fading channels, and show that a formulation of the sequence estimation problem based on the EM algorithm can provide a means of obtaining ML sequence estimates, a task that has been previously too complex to perform View full abstract»

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  • The quasi-random input queueing system with repeated attempts as a model for a collision-avoidance star local area network

    Publication Year: 1997 , Page(s): 360 - 364
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    A performance model is developed and validated for a local area network (LAN) with a star topology. A collision-avoidance network access protocol, as implemented in Hubnet, is considered. The model is based on a single server queueing system with finite sources and with a single buffer. Packets arriving at a full buffer retry their access after a fixed time period. Results for an eight-node network are presented and validated by means of earlier obtained simulation results View full abstract»

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  • Reduced-state sequence estimator with reverse-time structure

    Publication Year: 1997 , Page(s): 265 - 268
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    A modified reduced-state sequencer estimator (RSSE) with a reverse-time structure is proposed for postcursor dominated impulse response channels. This structure can provide significant performance improvements over a conventional RSSE of similar complexity for a well-defined and practically motivated class of channels View full abstract»

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  • A circuit for high-speed time switching

    Publication Year: 1997 , Page(s): 287 - 288
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (40 KB)  

    A method of time switching for time-division communication systems is introduced. A compact shift register-based circuit is used for this purpose in order to achieve high-speed switching View full abstract»

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  • Extended MLSE diversity receiver for the time- and frequency-selective channel

    Publication Year: 1997 , Page(s): 322 - 333
    Cited by:  Papers (24)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    This paper develops a maximum-likelihood sequence estimation (MLSE) diversity receiver for the time- and frequency-selective channel corrupted by additive Gaussian noise when linear constellations (M-ASK, M-PSK, M-QAM) are employed. The paper extends Ungerboeck's derivation of the extended MLSE receiver for the purely frequency-selective channel to the more general channel. Although the new receiver structure and metric assume ideal channel-state information (CSI), the receiver can be used wherever high-quality CSI is available, such as a comb of pilot tones or time-isolated symbols. The major contributions of this paper are as follows: (1) the derivation of a finite-complexity diversity receiver that is maximum likelihood (ML) for all linear channel models and sources of diversity, as long as ideal CSI is available; (2) a benchmark, in that the new receiver's performance is a lower bound on the performance of practical systems, which either lack ideal CSI or are not ML; (3) insight into matched filtering and ML diversity receiver processing for the time- and frequency-selective channels; and (4) bounds on the new receiver's bit-error rate (BER) for ideal CSI and pilot tone CSI, in a fast Rayleigh-fading channel with multiple independently faded paths. The new receiver can seamlessly tolerate square-root Nyquist pulses without a fading-induced ISI error floor View full abstract»

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  • Performance assessment of dc-free multimode codes

    Publication Year: 1997 , Page(s): 293 - 299
    Cited by:  Papers (31)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    We report on a class of high-rate dc-free codes, called multimode codes, where each source word can be represented by a codeword taken from a selection set of codeword alternatives. Conventional multimode codes are analyzed using a simple mathematical model. The criterion used to select the “best” codeword from the selection set available has a significant bearing on the performance. Various selection criteria are introduced and their effect on the performance of multimode codes is examined View full abstract»

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  • Put absolute moment block truncation coding in perspective

    Publication Year: 1997 , Page(s): 284 - 286
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (48 KB)  

    The purpose of this letter is to point out that the Udpikar and Raina (1987) modified block truncation coding (BTC) has been misleading researchers as a different BTC scheme in multiple publications for years. In fact, their algorithm is exactly identical to the second version of the Lema and Mitchell (1984) absolute moment block truncation coding (AMBTC). Mathematical proof is provided View full abstract»

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  • Differentially amplitude and phase-encoded QAM for the correlated Rayleigh-fading channel with diversity reception

    Publication Year: 1997 , Page(s): 309 - 321
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    This paper studies the differentially amplitude and phase-encoded (DAPE) quadrature amplitude modulation (QAM) transmission over correlated Rayleigh channels with diversity reception. Operating over two successive received symbols, the optimum and an asymptotic maximum-likelihood (AML) differentially coherent receiver are developed and compared with a conventional switched diversity combining (SDC) grid receiver. It is shown that the AML and SDC grid receivers are much simpler in complexity than the optimum receiver in that no channel side information is required in their realization. An exact expression of the bit-error probability (BEP) is obtained for the SDC grid receiver. Based on a union bound argument, a BEP upper bound for the AML receiver is also derived and verified by simulation. Numerical results on 16- and 64-point constellations show that the AML receiver exhibits an almost optimum performance and the SDC grid receiver with a small level of diversity is nearly optimum. It is also shown by simulation that the conventional equal-gain diversity receiver is almost optimal for demodulating a 16-point DAPE QAM signal View full abstract»

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  • A Family of Pure Digital Signal Processing Bit Synchronizers

    Publication Year: 1997 , Page(s): 289 - 292
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

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

 

 

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Robert Schober
University of British Columbia