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Papers by Marc Moeneclaey

Research paper thumbnail of Synchronization for MIMO systems

Research paper thumbnail of The IAP-MOTION project: mobile multimedia communication systems and networks

Research paper thumbnail of Exact BER analysis for QAM transmission on arbitrary fading channels with maximal-ratio combining and imperfect channel estimation

2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications, 2008

In this contribution, we investigate the effect of imperfect channel estimation on the bit error ... more In this contribution, we investigate the effect of imperfect channel estimation on the bit error rate (BER) performance of uncoded quadrature amplitude modulation (QAM) with maximal-ratio combining (MRC) multichannel reception. The propagation channels from the transmitter to each of the Nr receive antennas are assumed to be affected by (possibly correlated) flat block fading with an arbitrary fading distribution. The MRC receiver makes use of estimated channel coefficients, obtained from known pilot symbols sent among the data. The resulting average BER for QAM can easily be written as an expectation over 4Nr random variables, but the computing time needed for its numerical evaluation increases exponentially with Nr. We point out that the BER can be expressed in terms of the distribution of the norm of the channel vector, rather than the joint distribution of all channel coefficients. This allows to reduce the BER expression to an expectation over only 4 random variables, irrespective of the number of receive antennas. Moreover, we show that for real-valued constellations and/or real-valued channels, the BER expression reduces to an expectation over less than 4 variables. For practical BER levels, the numerical evaluation of the BER is much less time-consuming than a straightforward computer simulation. The presented BER expression is useful not only when the fading distribution is given in closed form, but also when only experimental data (e.g. a histogram) on the fading are available.

Research paper thumbnail of The modified Cramer-Rao bound for channel estimation in quantize-and-forward cooperative systems

2013 IEEE Wireless Communications and Networking Conference (WCNC), 2013

ABSTRACT

Research paper thumbnail of Outage probability minimization for cooperative cognitive radio with best-relay selection under an average interference power constraint

2013 IEEE 24th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), 2013

ABSTRACT

Research paper thumbnail of Low-Density Graph Codes for slow fading Relay Channels

Computing Research Repository, 2009

We study Low-Density Parity-Check (LDPC) codes with iterative decoding on block-fading (BF)Relay ... more We study Low-Density Parity-Check (LDPC) codes with iterative decoding on block-fading (BF)Relay Channels. We consider two users that employ coded cooperation, variant of decode-and-forward with a smaller outage probability than the latter. An outage probability analysis for discrete constellations shows that full-diversity can be achieved only when the coding rate does not exceed a maximum value that depends on the

Research paper thumbnail of Universal LDPC codes for cooperative communications

2010 6th International Symposium on Turbo Codes & Iterative Information Processing, 2010

Cooperative communication is a well known technique to yield transmit diversity in the case of fa... more Cooperative communication is a well known technique to yield transmit diversity in the case of fading channels and to increase the spectral efficiency in the case of Gaussian channels. Error-correcting codes have to be carefully designed to achieve the promised gains. Good LDPC codes are known for fading channels and for Gaussian channels, but an LDPC code ensemble that performs well on both channels has not yet been presented in the literature. This paper merges two families of LDPC codes into a universal LDPC code ensemble for both fading channels and Gaussian channels. Furthermore, the new universal LDPC code ensemble outperforms previously proposed codes on the block fading channel, which is explained through a fading space analysis. Simulation of the word error rate performance of the new proposed family of LDPC codes shows that it performs well on both fading channels and Gaussian channels.

Research paper thumbnail of Sensitivity of Multicarrier Systems to Synchronization Errors

In this contribution, we give an overview of the sensitivity of a number of multicarrier systems ... more In this contribution, we give an overview of the sensitivity of a number of multicarrier systems to carrier and symbol synchronization errors. A comparison is made between orthogonal frequency-division multiplexing/multiple access (OFDM(A)) and two combinations of the orthogonal multicarrier (MC) transmission technique with the code-division multiple access technique (CDMA), i.e. multicarrier CDMA (MC- CDMA), where the spreading is accomplished in

Research paper thumbnail of Digital Modems using Non-synchronized Sampling: Matched Filter + Interpolator versus Interpolator + Matched Filter

Research paper thumbnail of Increasing CDMA capacity using multiple orthogonal spreading sequence sets and successive interference cancellation

IEEE International Conference on Communications, 2002

In this paper, we present a code-division multiple access (CDMA) system with a spreading factor o... more In this paper, we present a code-division multiple access (CDMA) system with a spreading factor of N that can accommodate up to mN users, where m≥2. The m sets of orthogonal spreading sequences are constructed by overlaying the same N orthogonal Walsh-Hadamard sequences with a set-specific pseudo-noise (PN) sequence. Interference between user signals from different sets is cancelled by means

Research paper thumbnail of Synchronization at low SNR: performance bounds and algorithms

This contribution compares several types of feed-forward synchronization algorithms when applied ... more This contribution compares several types of feed-forward synchronization algorithms when applied to powerful error-correcting codes. As such codes operate at very low SNR, conventional synchronization algorithms often prove to be unreliable. By exploiting the code properties we may improve the synchronization performance. We investigate a code-aided synchronizer that operates according the EM algorithm. This synchronizer is applied to the problem of carrier phase and timing synchronization. Lower bounds on the estimator performance are derived: we express the true Cramer-Rao Bound for the system as a function of the marginal posterior probabilities of the coded symbols. Various synchronization algorithms are compared in terms of their estimation error variance and their effect on the BER.

Research paper thumbnail of New Factor Graph Based Multiuser Detector for Spectrally Efficient CPM

This paper presents a new iterative multiuser detection algorithm for asynchronous spectrally-eff... more This paper presents a new iterative multiuser detection algorithm for asynchronous spectrally-efficient M -ary continuous-phase modulation in additive white Gaussian noise. This detection algorithm is closely related to another algorithm that was recently proposed by the same authors, but it follows from applying the sum-product algorithm to a different factor graph of the same multiuser detection problem. This, in turn, results in a different way to approximate the marginal bit a-posteriori probabilities that are used to perform minimum bit error rate multiuser detection. The girth of the factor graph considered in this contribution is twice as large, which is known to be potentially beneficial for the accuracy of the a-posteriori probabilities. The size of the largest factor graph variable alphabets also multiplies with M , rendering the straightforward application of the sum-product algorithm more complex. Through approximating a suitable set of sum-product messages by a Gaussian distribution, this complexity is significantly reduced. For a set of system parameters yielding high spectral efficiency, the resulting algorithm significantly outperforms the previously proposed solution.

Research paper thumbnail of way can improve the overall accuracy and performance of the system

| The introduction of turbo and low-density paritycheck (LDPC) codes with iterative decoding that... more | The introduction of turbo and low-density paritycheck (LDPC) codes with iterative decoding that almost attain Shannon capacity challenges the synchronization subsystems of a data modem. Fast and accurate signal synchronization has to be performed at a much lower value of signal-to-noise ratio (SNR) than in previous less efficiently coded systems. The solution to this issue is developing specific synchronization techniques that take advantage of the presence of the channel code and of the iterative nature of decoding: the so-called turbo-synchronization algorithms. The aim of this paper within this special issue devoted to the turbo principle is twofold: on the one hand, it shows how the many turbo-synchronization algorithms that have already appeared in the literature can be cast into a simple and rigorous theoretical framework. On the other hand, it shows the application of such techniques in a few simple cases, and evaluates improvement that can be obtained from them, especially in the low-SNR regime.

Research paper thumbnail of CARRIER PHASE TRACKING AT LOW SIGNAL-TO-NOISE RATIO: A PERFORMANCE COMPARISON OF A PARITY-CODE-AIDED AND A PILOT- SYMBOL-ASSISTED APPROACH

Research paper thumbnail of Digital Communication Receivers: Synchronization

... Collaborative Colleagues: Heinrich Meyr: colleagues. Marc Moeneclaey: colleagues.Stefan Fecht... more ... Collaborative Colleagues: Heinrich Meyr: colleagues. Marc Moeneclaey: colleagues.Stefan Fechtel: colleagues. The ACM Portal is published by the Association for Computing Machinery. Copyright © 2010 ACM, Inc. Terms of ...

Research paper thumbnail of Mobile multimedia communication systems and networks

Research paper thumbnail of IEEE COMMUNICATIONS LETTERS, VOL. 7, NO. 5, MAY 2003 207 The Cramer-Rao Bound for Phase Estimation From

In this letter, we express the Cramer-Rao Bound (CRB) for carrier phase estimation from a noisy l... more In this letter, we express the Cramer-Rao Bound (CRB) for carrier phase estimation from a noisy linearly modulated signal with encoded data symbols, in terms of the marginal a posteriori probabilities (APPs) of the coded symbols. For a wide range of classical codes (block codes, convolutional codes, and trellis-coded modulation), these marginal APPs can be computed efficiently by means of the Bahl--Cocke--Jelinke--Raviv (BCJR) algorithm, whereas for codes that involve interleaving (turbo codes and bit interleaved coded modulation), iterated application of the BCJR algorithm is required. Our numerical results show that when the BER of the coded system is less than about 10 3 , the resulting CRB is essentially the same as when transmitting a training sequence.

Research paper thumbnail of The true Cramer-Rao bound for phase-independent

This contribution considers the Cramer-Rao bound (CRB) related to phase-independent carrier frequ... more This contribution considers the Cramer-Rao bound (CRB) related to phase-independent carrier frequency estimation from a noisy PSK signal. Instead of estimating the frequency jointly with the carrier phase, we treat the phase as a nuisance parameter. Ideal symbol timing is assumed. Both cases of known data (training sequence) and random data are considered. We show that frequency estimation irrespective of the carrier phase yields a larger CRB than does joint frequency and phase estimation; the penalty resulting from the former strategy vanishes with increasing observation interval.

Research paper thumbnail of The True Cramer-Rao Bound For Carrier And Symbol

This contribution considers the Cramer-Rao bound (CRB) related to estimating the synchronization ... more This contribution considers the Cramer-Rao bound (CRB) related to estimating the synchronization parameters (carrier phase, carrier frequency and time delay) of a noisy linearly modulated signal with random data symbols. We explore various scenarios, involving the estimation of a subset of the parameters while the other parameters are either considered as nuisance parameters or a priori known to the receiver. In addition, some results related to the CRB for coded transmission will be presented.

Research paper thumbnail of Some TDMA and OFDM/CDMA receiver structures for communication over the return path of the CATV network

This paper deals with the derivation and comparison of some promising TDMA and OFDM/CDMA receiver... more This paper deals with the derivation and comparison of some promising TDMA and OFDM/CDMA receiver structures for communication over the return path channel of the cable TV (CATV) network. Regarding TDMA, it is shown that the performance substantially improves by using equalization. Given the slowly varying, frequency selective nature of the ingress noise, OFDM seems an interesting possible access technique

Research paper thumbnail of Synchronization for MIMO systems

Research paper thumbnail of The IAP-MOTION project: mobile multimedia communication systems and networks

Research paper thumbnail of Exact BER analysis for QAM transmission on arbitrary fading channels with maximal-ratio combining and imperfect channel estimation

2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications, 2008

In this contribution, we investigate the effect of imperfect channel estimation on the bit error ... more In this contribution, we investigate the effect of imperfect channel estimation on the bit error rate (BER) performance of uncoded quadrature amplitude modulation (QAM) with maximal-ratio combining (MRC) multichannel reception. The propagation channels from the transmitter to each of the Nr receive antennas are assumed to be affected by (possibly correlated) flat block fading with an arbitrary fading distribution. The MRC receiver makes use of estimated channel coefficients, obtained from known pilot symbols sent among the data. The resulting average BER for QAM can easily be written as an expectation over 4Nr random variables, but the computing time needed for its numerical evaluation increases exponentially with Nr. We point out that the BER can be expressed in terms of the distribution of the norm of the channel vector, rather than the joint distribution of all channel coefficients. This allows to reduce the BER expression to an expectation over only 4 random variables, irrespective of the number of receive antennas. Moreover, we show that for real-valued constellations and/or real-valued channels, the BER expression reduces to an expectation over less than 4 variables. For practical BER levels, the numerical evaluation of the BER is much less time-consuming than a straightforward computer simulation. The presented BER expression is useful not only when the fading distribution is given in closed form, but also when only experimental data (e.g. a histogram) on the fading are available.

Research paper thumbnail of The modified Cramer-Rao bound for channel estimation in quantize-and-forward cooperative systems

2013 IEEE Wireless Communications and Networking Conference (WCNC), 2013

ABSTRACT

Research paper thumbnail of Outage probability minimization for cooperative cognitive radio with best-relay selection under an average interference power constraint

2013 IEEE 24th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), 2013

ABSTRACT

Research paper thumbnail of Low-Density Graph Codes for slow fading Relay Channels

Computing Research Repository, 2009

We study Low-Density Parity-Check (LDPC) codes with iterative decoding on block-fading (BF)Relay ... more We study Low-Density Parity-Check (LDPC) codes with iterative decoding on block-fading (BF)Relay Channels. We consider two users that employ coded cooperation, variant of decode-and-forward with a smaller outage probability than the latter. An outage probability analysis for discrete constellations shows that full-diversity can be achieved only when the coding rate does not exceed a maximum value that depends on the

Research paper thumbnail of Universal LDPC codes for cooperative communications

2010 6th International Symposium on Turbo Codes & Iterative Information Processing, 2010

Cooperative communication is a well known technique to yield transmit diversity in the case of fa... more Cooperative communication is a well known technique to yield transmit diversity in the case of fading channels and to increase the spectral efficiency in the case of Gaussian channels. Error-correcting codes have to be carefully designed to achieve the promised gains. Good LDPC codes are known for fading channels and for Gaussian channels, but an LDPC code ensemble that performs well on both channels has not yet been presented in the literature. This paper merges two families of LDPC codes into a universal LDPC code ensemble for both fading channels and Gaussian channels. Furthermore, the new universal LDPC code ensemble outperforms previously proposed codes on the block fading channel, which is explained through a fading space analysis. Simulation of the word error rate performance of the new proposed family of LDPC codes shows that it performs well on both fading channels and Gaussian channels.

Research paper thumbnail of Sensitivity of Multicarrier Systems to Synchronization Errors

In this contribution, we give an overview of the sensitivity of a number of multicarrier systems ... more In this contribution, we give an overview of the sensitivity of a number of multicarrier systems to carrier and symbol synchronization errors. A comparison is made between orthogonal frequency-division multiplexing/multiple access (OFDM(A)) and two combinations of the orthogonal multicarrier (MC) transmission technique with the code-division multiple access technique (CDMA), i.e. multicarrier CDMA (MC- CDMA), where the spreading is accomplished in

Research paper thumbnail of Digital Modems using Non-synchronized Sampling: Matched Filter + Interpolator versus Interpolator + Matched Filter

Research paper thumbnail of Increasing CDMA capacity using multiple orthogonal spreading sequence sets and successive interference cancellation

IEEE International Conference on Communications, 2002

In this paper, we present a code-division multiple access (CDMA) system with a spreading factor o... more In this paper, we present a code-division multiple access (CDMA) system with a spreading factor of N that can accommodate up to mN users, where m≥2. The m sets of orthogonal spreading sequences are constructed by overlaying the same N orthogonal Walsh-Hadamard sequences with a set-specific pseudo-noise (PN) sequence. Interference between user signals from different sets is cancelled by means

Research paper thumbnail of Synchronization at low SNR: performance bounds and algorithms

This contribution compares several types of feed-forward synchronization algorithms when applied ... more This contribution compares several types of feed-forward synchronization algorithms when applied to powerful error-correcting codes. As such codes operate at very low SNR, conventional synchronization algorithms often prove to be unreliable. By exploiting the code properties we may improve the synchronization performance. We investigate a code-aided synchronizer that operates according the EM algorithm. This synchronizer is applied to the problem of carrier phase and timing synchronization. Lower bounds on the estimator performance are derived: we express the true Cramer-Rao Bound for the system as a function of the marginal posterior probabilities of the coded symbols. Various synchronization algorithms are compared in terms of their estimation error variance and their effect on the BER.

Research paper thumbnail of New Factor Graph Based Multiuser Detector for Spectrally Efficient CPM

This paper presents a new iterative multiuser detection algorithm for asynchronous spectrally-eff... more This paper presents a new iterative multiuser detection algorithm for asynchronous spectrally-efficient M -ary continuous-phase modulation in additive white Gaussian noise. This detection algorithm is closely related to another algorithm that was recently proposed by the same authors, but it follows from applying the sum-product algorithm to a different factor graph of the same multiuser detection problem. This, in turn, results in a different way to approximate the marginal bit a-posteriori probabilities that are used to perform minimum bit error rate multiuser detection. The girth of the factor graph considered in this contribution is twice as large, which is known to be potentially beneficial for the accuracy of the a-posteriori probabilities. The size of the largest factor graph variable alphabets also multiplies with M , rendering the straightforward application of the sum-product algorithm more complex. Through approximating a suitable set of sum-product messages by a Gaussian distribution, this complexity is significantly reduced. For a set of system parameters yielding high spectral efficiency, the resulting algorithm significantly outperforms the previously proposed solution.

Research paper thumbnail of way can improve the overall accuracy and performance of the system

| The introduction of turbo and low-density paritycheck (LDPC) codes with iterative decoding that... more | The introduction of turbo and low-density paritycheck (LDPC) codes with iterative decoding that almost attain Shannon capacity challenges the synchronization subsystems of a data modem. Fast and accurate signal synchronization has to be performed at a much lower value of signal-to-noise ratio (SNR) than in previous less efficiently coded systems. The solution to this issue is developing specific synchronization techniques that take advantage of the presence of the channel code and of the iterative nature of decoding: the so-called turbo-synchronization algorithms. The aim of this paper within this special issue devoted to the turbo principle is twofold: on the one hand, it shows how the many turbo-synchronization algorithms that have already appeared in the literature can be cast into a simple and rigorous theoretical framework. On the other hand, it shows the application of such techniques in a few simple cases, and evaluates improvement that can be obtained from them, especially in the low-SNR regime.

Research paper thumbnail of CARRIER PHASE TRACKING AT LOW SIGNAL-TO-NOISE RATIO: A PERFORMANCE COMPARISON OF A PARITY-CODE-AIDED AND A PILOT- SYMBOL-ASSISTED APPROACH

Research paper thumbnail of Digital Communication Receivers: Synchronization

... Collaborative Colleagues: Heinrich Meyr: colleagues. Marc Moeneclaey: colleagues.Stefan Fecht... more ... Collaborative Colleagues: Heinrich Meyr: colleagues. Marc Moeneclaey: colleagues.Stefan Fechtel: colleagues. The ACM Portal is published by the Association for Computing Machinery. Copyright © 2010 ACM, Inc. Terms of ...

Research paper thumbnail of Mobile multimedia communication systems and networks

Research paper thumbnail of IEEE COMMUNICATIONS LETTERS, VOL. 7, NO. 5, MAY 2003 207 The Cramer-Rao Bound for Phase Estimation From

In this letter, we express the Cramer-Rao Bound (CRB) for carrier phase estimation from a noisy l... more In this letter, we express the Cramer-Rao Bound (CRB) for carrier phase estimation from a noisy linearly modulated signal with encoded data symbols, in terms of the marginal a posteriori probabilities (APPs) of the coded symbols. For a wide range of classical codes (block codes, convolutional codes, and trellis-coded modulation), these marginal APPs can be computed efficiently by means of the Bahl--Cocke--Jelinke--Raviv (BCJR) algorithm, whereas for codes that involve interleaving (turbo codes and bit interleaved coded modulation), iterated application of the BCJR algorithm is required. Our numerical results show that when the BER of the coded system is less than about 10 3 , the resulting CRB is essentially the same as when transmitting a training sequence.

Research paper thumbnail of The true Cramer-Rao bound for phase-independent

This contribution considers the Cramer-Rao bound (CRB) related to phase-independent carrier frequ... more This contribution considers the Cramer-Rao bound (CRB) related to phase-independent carrier frequency estimation from a noisy PSK signal. Instead of estimating the frequency jointly with the carrier phase, we treat the phase as a nuisance parameter. Ideal symbol timing is assumed. Both cases of known data (training sequence) and random data are considered. We show that frequency estimation irrespective of the carrier phase yields a larger CRB than does joint frequency and phase estimation; the penalty resulting from the former strategy vanishes with increasing observation interval.

Research paper thumbnail of The True Cramer-Rao Bound For Carrier And Symbol

This contribution considers the Cramer-Rao bound (CRB) related to estimating the synchronization ... more This contribution considers the Cramer-Rao bound (CRB) related to estimating the synchronization parameters (carrier phase, carrier frequency and time delay) of a noisy linearly modulated signal with random data symbols. We explore various scenarios, involving the estimation of a subset of the parameters while the other parameters are either considered as nuisance parameters or a priori known to the receiver. In addition, some results related to the CRB for coded transmission will be presented.

Research paper thumbnail of Some TDMA and OFDM/CDMA receiver structures for communication over the return path of the CATV network

This paper deals with the derivation and comparison of some promising TDMA and OFDM/CDMA receiver... more This paper deals with the derivation and comparison of some promising TDMA and OFDM/CDMA receiver structures for communication over the return path channel of the cable TV (CATV) network. Regarding TDMA, it is shown that the performance substantially improves by using equalization. Given the slowly varying, frequency selective nature of the ingress noise, OFDM seems an interesting possible access technique