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Communications, IEEE Transactions on

Issue 2 • Date Feb 1998

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Displaying Results 1 - 17 of 17
  • Some new twists to problems involving the Gaussian probability integral

    Publication Year: 1998 , Page(s): 200 - 210
    Cited by:  Papers (134)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    Using an alternate form of the Gaussian probability integral discovered a number of years ago, it is shown that the solution to a number of previously considered communication problems can be simplified and, in some cases, made more accurate (i.e. exact rather than bounded). These problems include the evaluation of: (1) the bit-error probability of uncoded phase shift keying (PSK) with Costas loop tracking; (2) word-error probability of antipodal modulation in the presence of fading; (3) bit-error probability of coded M-ary PSK (MPSK) over the memoryless fading channel with given channel-state information; (4) conditional symbol-error probability of MPSK in the presence of carrier synchronization error; and (5) the average error probability for the binary additive white Gaussian noise (AWGN) intersymbol interference channel. Also obtained is a generalization of this new alternate form to the case of a two-dimensional Gaussian probability integral with arbitrary correlation which can be used to evaluate the symbol-error probability of MPSK with I-Q unbalance View full abstract»

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  • Performance evaluation of DS-CDMA systems on multipath propagation channels with multilevel spreading sequences and RAKE receivers

    Publication Year: 1998 , Page(s): 244 - 257
    Cited by:  Papers (7)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    Performance of small-cell wireless direct sequence code-division multiple access (DS-CDMA) systems with multilevel spreading sequences is investigated. An analytical methodology to evaluate both outage probability and mean bit error probability is presented; and its results are compared to those obtained with a semianalytical Monte Carlo based approach. Multipath propagation, the exact correlation properties of spreading codes, and both the simple correlator and RAKE receivers are taken into account in the analysis, which is oriented to asynchronous and synchronous environments. The spreading sequences investigated include multilevel sequences with complex isomorphic mapping, as well as some well-known two-level sequences. The numerical results show the impact of multilevel sequences on system performance, the improvements found in the absence of multiple access interference by using them rather than binary sequences, and the agreement between analytical and semianalytical evaluation View full abstract»

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  • Error probability performance of L-branch diversity reception of MQAM in Rayleigh fading

    Publication Year: 1998 , Page(s): 179 - 181
    Cited by:  Papers (47)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    New exact expressions involving hypergeometric functions are derived for the symbol-error rate (SER) of M-ary quadrature amplitude modulation (MQAM) for L branch diversity reception in Rayleigh fading and additive white Gaussian noise (AWGN). The diversity combining techniques considered are maximum ratio combining (MRC) and selection combining (SC). MRC with identical channels and dissimilar channels are analyzed View full abstract»

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  • Set partitioning for multilevel codes on a Rayleigh-fading channel

    Publication Year: 1998 , Page(s): 161 - 163
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    On a Rayleigh-fading channel, multilevel codes achieve larger Hamming distances than single-level codes at comparable decoder complexity and bandwidth efficiency by employing a multistage decoder. Typically, multilevel codes are designed using Ungerboeck's (1982) set partitioning. This results in a large path multiplicity that degrades the code performance significantly. In order to overcome the performance degradation, we propose a set partitioning method that greatly reduces the path multiplicity View full abstract»

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  • MLSE for correlated diversity sources and unknown time-varying frequency-selective Rayleigh-fading channels

    Publication Year: 1998 , Page(s): 169 - 172
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (172 KB)  

    Yu and Pasupathy (see ibid., vol.43, p. 1534-44, 1995) derived a maximum-likelihood sequence estimation (MLSE) receiver structure for unknown time varying frequency-selective Rayleigh-fading channels and uncorrelated diversity sources. This receiver design is extended to the case of correlated diversity sources. Correlated diversity sources typically arise with space diversity, where constraints on antenna volume require that diversity antennae be placed too closely together. Analytic and simulated bit-error rate (BER) curves are presented for receivers which exploit and ignore the correlation. In the former case, we find a small BER improvement that reduces with decreasing correlation. However, for a fixed receiver complexity, superior performance is achieved when the correlation is ignored View full abstract»

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  • Maximum-likelihood synchronization, equalization, and sequence estimation for unknown time-varying frequency-selective Rician channels

    Publication Year: 1998 , Page(s): 211 - 221
    Cited by:  Papers (23)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    This paper develops a receiver structure to perform jointly maximum-likelihood (ML) synchronization, equalization, and detection of a linearly modulated signal transmitted over a time-varying frequency-selective Rician-faded channel, corrupted by additive white Gaussian noise (AWGN). The receiver is particularly suited to a fast-fading channel, where other receivers that rely on estimating the channel cannot track it quickly enough. The signal mean and autocovariance are needed, and a scheme is proposed for estimating these quantities adaptively. The receiver processes the specular and diffuse components (corresponding to the signal mean and autocovariance) separately. Processing the known specular component is the classical detection problem. The unknown diffuse component is processed by predictors. We show that the predictors can achieve synchronization in a novel manner, if synchronization is required. A union bound on the receiver's bit-error rate (BER) is derived, and it tightly bounds simulated BERs in fast-fading at high signal-to-noise ratios (SNRs) View full abstract»

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  • Bit allocation for discrete signal detection

    Publication Year: 1998 , Page(s): 173 - 175
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (124 KB)  

    This paper considers a system in which observations at a remote sensor are sampled and quantized, and then transmitted to a processor for signal detection. A constraint on the transmission rate is assumed. The problem of bit allocation among different samples is studied and illustrated by means of an example View full abstract»

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  • Mean-square crosstalk approach to CPM

    Publication Year: 1998 , Page(s): 176 - 178
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (88 KB)  

    The maximum-likelihood sequence estimator (MLSE) for continuous phase modulation (CPM) signals in an additive white Gaussian noise (AWGN) channel is a very efficient method of detection. This paper describes an extension of a relatively simple crosstalk approach for the performance analysis of linear quadrature receivers with cochannel interference (CCI) and adjacent channel interference (ACI) present to the MLSE receiver. Many CPM signals are analyzed, including those using new baseband modulating pulses. One of the new schemes allows an ACI signal to be 62 dB greater than the desired user signal at a frequency separation of one-and-a-half times the bit rate, with just a 2-dB degradation in required Eb/N0 View full abstract»

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  • Coding and stability in frequency-hop packet radio networks

    Publication Year: 1998 , Page(s): 191 - 199
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    A fully connected radio network is considered in which packets are sent using slow frequency-hop (FH) modulation, slotted ALOHA random access, and Reed-Solomon (RS) error-control coding. For this network, the dependence of throughput, delay, and drift on the code rate and block length is examined. It is shown that the drift approaches a simple limiting form as the block length becomes large. This form suggests that, in a bistable FH network, the undesirable stable point can usually be eliminated without increasing the delay or reducing the throughput at the desirable stable point. In particular, bistability can be eliminated by increasing the code block length and retransmission delay, and does not require the use of decentralized control or channel traffic estimates View full abstract»

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  • Improved parallel interference cancellation for CDMA

    Publication Year: 1998 , Page(s): 258 - 268
    Cited by:  Papers (345)  |  Patents (41)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    This paper introduces an improved nonlinear parallel interference cancellation scheme for code-division multiple access (CDMA) that significantly reduces the degrading effect on the desired user of interference from the other users that share the channel. The implementation complexity of the scheme is linear in the number of users and operates on the fact that parallel processing simultaneously removes from each user a part of the interference produced by the remaining users accessing the channel the amount being proportional to their reliability. The parallel processing can be done in multiple stages. The proposed scheme uses tentative decision devices at the multiple stages to produce the most reliably estimated received data for generation and cancellation of user interference. Simulation results are given for a multitude of different situations, in particular, those cases for which the analysis is too complex View full abstract»

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  • Worst-case error probability of a spread-spectrum system in energy-limited interference

    Publication Year: 1998 , Page(s): 286 - 296
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    We consider a communication channel corrupted by thermal noise and by an unknown and arbitrary interference of bounded energy. For this channel, we derive a simple upper bound to the worst-case error probability suffered by a direct sequence (DS) communication system with error-correction coding, pseudorandom interleaving, and a correlation receiver. This bound is exponentially tight as the block length of the error correcting code becomes large. Numerical examples are given that illustrate the dependence of the bound on the choice of error correcting code, the type of interleaving used, and the relative energy of the Gaussian noise and arbitrary interference View full abstract»

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  • Block adaptive techniques for channel identification and data demodulation over band-limited channels

    Publication Year: 1998 , Page(s): 232 - 243
    Cited by:  Papers (8)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    A new approach to the problem of data detection for communications over band-limited channels with unknown parameters is introduced. We propose a new way to implement the Viterbi algorithm (VA) for maximum-likelihood data sequence estimation (MLSE) in a known channel environment and utilize it to derive block adaptive techniques for joint channel and data estimation, when the channel-impulse response (CIR) is unknown. We show, via simulations, that we can achieve a probability of error very close to that of the known channel environment and nearly reach a mean-square error in the channel estimate as predicted by analytical bounds, operating on static channels, which exhibit deep nulls in their magnitude response and nonlinear phase. The proposed schemes accomplish channel acquisition after processing a few hundred symbols while operating without a training sequence, whereas linear blind equalizers, such as Sato's (1975) algorithm, fail to converge at all. The application of block processing to adaptive MLSE is also investigated for time-varying frequency-selective Rayleigh-fading channels, which are used for modeling mobile communication systems. In such environments it is shown that the proposed scheme exhibits improved performance compared to the conventional adaptive MLSE receiver using tentative delayed decisions View full abstract»

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  • Joint transmitter-receiver optimization in synchronous multiuser communications over multipath channels

    Publication Year: 1998 , Page(s): 269 - 278
    Cited by:  Papers (48)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    Transmitter optimization, in addition to receiver optimization, contributes significantly to efficient interference suppression in multiple access and multipath channels. The system design is based on the joint optimization of the transmitter and the receiver in a synchronous multiuser channel characterized by multipath propagation. Joint optimization is represented by a linear transformation of the transmitted signals at the transmitter and a linear transformation of received signals at each receiving site that minimize the effect of multiple access and multipath interference. The minimum mean squared error between the true bit value and its estimate at the output of the receiver is taken as the cost function, subject to average and peak transmit power constraints. It is shown that joint transmitter-receiver optimization outperforms significantly either transmitter optimization or receiver-based techniques. The crucial assumption, in the case of multipath channels, is that the transmitter knows the multipath characteristics of all channels and that the channel dynamics are sufficiently slow so that multipath profiles remain essentially constant over a block of preceded bits. The practical applications can be found in indoor and cellular communications, satellite communications, or military communications where nonorthogonal signature waveforms are employed View full abstract»

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  • A new method for determining “unknown” worst-case channels for maximum-likelihood sequence estimation

    Publication Year: 1998 , Page(s): 164 - 168
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    We derive a series of upper and lower bounds for the minimum distance between two noise-free output sequences over unknown channels with fixed-energy finite-duration impulse responses. Using these bounds, we develop a method for determining the minimum distance. Such distance is crucial for determining the worst possible performance of maximum likelihood sequence estimation (MLSE) View full abstract»

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  • The use of WMC distribution for performance evaluation of APD optical communication systems

    Publication Year: 1998 , Page(s): 279 - 285
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    In the analysis of the bit-error rate (BER) of an optical communication system with avalanche photodiode (APD) detectors, the Webb, McIntyre, Conradi (1974) distribution has been often used to approximate the APD receiver output statistics. This paper presents new simple and closed form BER expressions as well as an importance sampling technique for optical systems employing APD receivers when the WMC model is used. Comparison of the WMC model with the exact model is also carried out. In particular, it is shown that the WMC distribution is quite accurate and has the advantage of simplicity for both simulation and analysis View full abstract»

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  • Performance analysis of Viterbi decoding for 64-DAPSK and 64-QAM modulated OFDM signals

    Publication Year: 1998 , Page(s): 182 - 190
    Cited by:  Papers (48)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    The multilevel modulation techniques of 64-quadrature amplitude modulation (QAM) and 64-differential amplitude and phase-shift keying (DAPSK) have been proposed in combination with the orthogonal frequency-division multiplexing (OFDM) scheme for digital terrestrial video broadcasting (DTVB). With this system a data rate of 34 Mb/s can be transmitted over an 8-MHz radio channel. A comparison of these modulation methods in the uncoded case has been presented by Engels and Rohling (see European Trans. Telecommun., vol.6, p.633-40, 1995). The channel coding scheme proposed for DTVB by Schafer (see Proc. Int. Broadcasting Convention, Amsterdam, The Netherlands, p.79-84, 1995) consists of an inner convolutional code concatenated with an outer Reed-Solomon (RS) code. In this paper the performance of the convolutional codes is analyzed for the two modulation techniques. This analysis includes soft decision Viterbi (1971) decoding of the convolutional code. For soft decision decoding of DAPSK modulated signals a new metric is developed View full abstract»

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  • A sequence-based approximate MMSE decoder for source coding over noisy channels using discrete hidden Markov models

    Publication Year: 1998 , Page(s): 222 - 231
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    In previous work on source coding over noisy channels it was recognized that when the source has memory, there is typically “residual redundancy” between the discrete symbols produced by the encoder, which can be capitalized upon by the decoder to improve the overall quantizer performance. Sayood and Borkenhagen (1991) and Phamdo and Farvardin (see IEEE Trans. Inform. Theory, vol.40, p.186-93, 1994) proposed “detectors” at the decoder which optimize suitable criteria in order to estimate the sequence of transmitted symbols. Phamdo and Farvardin also proposed an instantaneous approximate minimum mean-squared error (IAMMSE) decoder. These methods provide a performance advantage over conventional systems, but the maximum a posteriori (MAP) structure is suboptimal, while the IAMMSE decoder makes limited use of the redundancy. Alternatively, combining aspects of both approaches, we propose a sequence-based approximate MMSE (SAMMSE) decoder. For a Markovian sequence of encoder-produced symbols and a discrete memoryless channel, we approximate the expected distortion at the decoder under the constraint of fixed decoder complexity. For this simplified cost, the optimal decoder computes expected values based on a discrete hidden Markov model, using the wellknown forward/backward (F/B) algorithm. Performance gains for this scheme are demonstrated over previous techniques in quantizing Gauss-Markov sources over a range of noisy channel conditions. Moreover, a constrained delay version is also suggested View full abstract»

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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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Editor-in-Chief
Robert Schober
University of British Columbia