Francesco Verde | Università degli Studi di Napoli "Federico II" (original) (raw)

Papers by Francesco Verde

Ieee Communications Letters, 2001

We propose an adaptive minimum variance equalizer, which is able to recover the transmitted symbo... more We propose an adaptive minimum variance equalizer, which is able to recover the transmitted symbols even in the presence of severe cochannel interference (CCI) or adjacent-channel interference (ACI). Under the assumption that the interference exhibits a different symbol rate from the desired signal, the proposed equalizer can mitigate CCI/ACI without requiring knowledge of the channel impulse response of the interference.

2013 Future Network Mobile Summit, 2013

2006 14th European Signal Processing Conference, Sep 1, 2006

This paper deals with the problem of designing widely-linear (WL) fractionally-spaced (FS) finite... more This paper deals with the problem of designing widely-linear (WL) fractionally-spaced (FS) finite-impulse response equalizers for both real-and complex-valued improper modulation schemes. Specifically, the synthesis of both WL-FS minimum mean-square error and zero-forcing equalizers is discussed, by deriving the mathematical conditions assuring perfect symbol recovery in the absence of noise. In a general framework, the feasibility of designing WL-FS blind equalizers based on the constant modulus criterion is also investigated, and both unconstrained and constrained designs are provided. The effectiveness of the proposed equalizers is corroborated by means of computer simulation results.

2000 10th European Signal Processing Conference, 2000

The problem of recovering a digital communication signal distorted by a linear time-invariant cha... more The problem of recovering a digital communication signal distorted by a linear time-invariant channel and contaminated by severe co-channel or adjacent-channel digital interference is addressed in this paper. The proposed linear periodically time-varying (LPTV) receiver jointly performs channel equalization and interference suppression, without requiring explicit knowledge or estimation of the interfering channel. Simulation results confirm the effectiveness of the proposed technique, whose performance exhibit a remarkable robustness with respect to varying interference power level.

Acoustics Speech and Signal Processing 1988 Icassp 88 1988 International Conference on, Mar 14, 2010

Recently, much progress has been made on the cross-layer optimization of video streams in multipl... more Recently, much progress has been made on the cross-layer optimization of video streams in multiple access networks. The key idea is to use the granular data structure of compressed video to trade quality with bits, and optimally prioritize transmissions given the available bandwidth, in order to obtain proportionally optimal video quality across video streams. Herein, we discuss the effect and potential benefit of using a cooperative-relay strategy in a wireless network, where proportionally optimal video schedules are computed via a multi-user Markov decision process. The idea is that feeble signals of nodes that are located far away from the destination can be enhanced via the cooperation of intermediate nodes, acting as cooperative relays. Our contribution is to indicate a possible solution that would require relatively modest changes to the multi-user optimization framework, while warranting a uniformly better experience to the video users thanks to cooperative coding.

Acoustics Speech and Signal Processing 1988 Icassp 88 1988 International Conference on, 2010

The problem of channel shortening equalization (CSE) for multiinput multi-output (MIMO) orthogona... more The problem of channel shortening equalization (CSE) for multiinput multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems is addressed. Relying on constrained minimization of the mean-output-energy (MOE) at the CSE output, we propose a blind channel shortening technique, which does not require a priori knowledge or estimation of the MIMO channel impulse responses to be shortened. Numerical results showing the attainable performance gain of the proposed method are reported.

2006 IEEE International Conference on Acoustics Speed and Signal Processing Proceedings, 2000

ABSTRACT Constrained optimization techniques, based on the maximum signal-to-noise-plus-interfere... more ABSTRACT Constrained optimization techniques, based on the maximum signal-to-noise-plus-interference (SINR) criterion,, are considered for joint equalization and narrowband interference (NBI) suppression in orthogonal frequency-division multiplexing (OFDM) systems. Specifically, we show that a recently proposed linear receiver (D. Darsena et al., 2005), which mitigates, in the minimum mean-output-energy sense, the NBI contribution at the receiver output, can be regarded as the solution of a constrained maximum-SINR optimization criterion and, moreover, admits an interesting three-stage decomposition. This decomposition improves the receiver robustness against errors in the estimated statistics of the received data and, most important, allows one to greatly simplify the channel estimation problem. Computer simulations are earned out to illustrate the performance improvements achievable by adopting the constrained maximum-SINR equalizer, in comparison with its unconstrained counterpart

Conference Record of the Thirty-Sixth Asilomar Conference on Signals, Systems and Computers, 2002., 2000

ABSTRACT This paper deals with blind multiuser detection for asynchronous multicarrier code-divis... more ABSTRACT This paper deals with blind multiuser detection for asynchronous multicarrier code-division multiple-access (MC-CDMA) systems. A two-stage linear multiuser detector is proposed, where the first stage performs preliminary disturbance mitigation, allowing thus the second stage, based on the constant modulus algorithm (CMA), to operate with nearly disturbance-free data. The proposed receiver is totally blind, since it needs only a coarse synchronization to the desired user's transmission and knowledge of its spreading code. The effectiveness of the proposed approach is corroborated by computer simulation results, which show that, even with small sample size values, the proposed detector achieves performances close to (and often superior than) those of the non-blind minimum-mean-square error (MMSE) receiver.

IEEE 5th Workshop on Signal Processing Advances in Wireless Communications, 2004., 2000

We propose a new blind channel identification method for multicarrler (MC) transmission systems e... more We propose a new blind channel identification method for multicarrler (MC) transmission systems employing noncircular modulation fonnats. To elLploit the noncircularity property of the signal constellation, the proposed algorithm relies on the subspace decomposition of the augmented vector obtained by stacking the received data ,'ector and its complex·conjugate version. Unlike recently proposed subspace· based techniques, this method allows one to successfully estimate the channel impulse re sponse under certain identifiability conditions, without requiring the introduction of additional redundancy in transmission (e.g., ,'ir tual carriers), and \\ithout resorting to o,'ersampling and/or multi ple antennas at the receh'er. Moreover, it is shown that blind cban nel identification can be performed satisfactorily also in the presen. ce of narrowband interference (NBJ), requiring onIy approlLimate rank determination of the NBI augmented autocorrelation matrix.

2007 IEEE 8th Workshop on Signal Processing Advances in Wireless Communications, 2007

We propose a blind adaptive channel-shortening method for designing finite-impulse response time-... more We propose a blind adaptive channel-shortening method for designing finite-impulse response time-domain equalizers (TEQs) in singleinput multiple-output systems employing multicarrier modulations. The proposed algorithm, which relies on a constrained minimization of the mean-output-energy at the TEQ output, does not require neither a priori knowledge of the channel impulse response nor transmission of training sequences. Moreover, the proposed TEQ is narrowband interference resistant and its synthesis only requires an upper bound (rather than the exact knowledge) of the channel order. * This work is partially supported by Italian National project Wireless 8O2.16 Multi-antenna mEsh Networks (WOMEN) under grant number 2005093248.

2015 IEEE International Conference on Communications (ICC), 2015

2015 IEEE Metrology for Aerospace (MetroAeroSpace), 2015

ABSTRACT This paper deals with the synthesis of a blind channel shortening algorithm for orthogon... more ABSTRACT This paper deals with the synthesis of a blind channel shortening algorithm for orthogonal frequency-division multiplexing (OFDM) systems operating over doubly selective wireless channels, a challenging scenario that is likely to happen in modern unmanned aircraft systems (UASs) data links. When the length of the OFDM cyclic prefix (CP) is smaller than the channel order, we propose to employ a blind linear time-varying (LTV) time-domain equalizer, which shortens the channel impulse response of the channel in the minimum mean-output energy (MMOE) sense, requiring only estimation of the second-order statistics of the received data. The equalizer design leverages on the complex-exponential (CE) basis expansion model (BEM) for the doubly selective channel, which naturally leads to a frequency-shift (FRESH) filter implementation. Monte Carlo computer simulations are carried out to assess the effectiveness of the proposed FRESH-MMOE channel shortener.

2014 European Conference on Networks and Communications (EuCNC), 2014

ABSTRACT We consider a wireless cooperative network, where communication between a source-destina... more ABSTRACT We consider a wireless cooperative network, where communication between a source-destination pair is assisted by multiple relaying nodes. To cope with the wideband nature of the wireless channel, all network nodes are equipped with multiple antennas and employ orthogonal frequency-division multiplexing (OFDM) modulation. Leveraging on an approximate yet accurate performance analysis of the network, carried out in terms of symbol error probability (SEP), a closed-form minimum-SEP optimal design of precoding and relaying matrices is proposed, which allows one to fully exploit the distributed diversity inherent to the cooperative approach, but requires accurate channel state information at the source and the relays. Monte Carlo numerical results are provided to assess the performance advantages that can be achieved by the proposed design.

2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications, 2008

A cross-layer approach, called CoopMAC, has been proposed recently to integrate cooperation at th... more A cross-layer approach, called CoopMAC, has been proposed recently to integrate cooperation at the physical layer with the medium access control sublayer, thereby achieving substantial throughput and delay performance improvements. CoopMAC capitalizes on the broadcast nature of wireless channels, recruiting a relay opportunistically and on the fly to support the communication of a particular source-destination pair. Herein, we study a cross-layer framework that uses randomized cooperative coding, and allows the simultaneous recruitment of multiple relays which collectively act as the antennas of a distributed transmission array, by simply randomizing the antenna code selection rule. We show that randomized cooperation not only alleviates the burden associated with the relay selection process, but also fully exploits the available spatial diversity.

2007 IEEE 8th Workshop on Signal Processing Advances in Wireless Communications, 2007

This paper deals with multiuser detection for multicarrier code-division multiple-access (MC-CDMA... more This paper deals with multiuser detection for multicarrier code-division multiple-access (MC-CDMA) systems, employing either zeropadded or cyclic-prefixed transmission techniques. For both systems, we consider widely-linear finite-impulse response (WL-FIR) estimators, which process both the received signal and its complex conjugate version. With regard to downlink configurations, it is shown that, if the number of users does not exceed a given threshold and their codes are appropriately designed, channel-irrespective WL-FIR zero-forcing symbol recovery is possible. In particular, some spreading code examples are provided, which satisfy our design rules.

In orthogonal-frequency-division-multiplexing (OFDM) systems, finite-impulse response (FIR) linea... more In orthogonal-frequency-division-multiplexing (OFDM) systems, finite-impulse response (FIR) linear precoders allow for perfect or zero-forcing (ZF) equalization of FIR channels (in the absence of noise). Recently, it has been shown that the noncircular or improper nature of some symbol constellations offers an intrinsic source of redundancy, which can be exploited to design efficient FIR widely-linear (WL) receiving structures for OFDM systems operating in the presence of narrowband interference (NBI). With regard to both cyclic-prefixed and zero-padded transmission techniques, it is shown in this paper that, with appropriately designed precoders, it is possible to synthesize in both cases WL-ZF universal equalizers, which guarantee perfect symbol recovery for any FIR channel and, at the same time, exhibit satisfactory NBI suppression capabilities.

Ieee Communications Letters, 2001

We propose an adaptive minimum variance equalizer, which is able to recover the transmitted symbo... more We propose an adaptive minimum variance equalizer, which is able to recover the transmitted symbols even in the presence of severe cochannel interference (CCI) or adjacent-channel interference (ACI). Under the assumption that the interference exhibits a different symbol rate from the desired signal, the proposed equalizer can mitigate CCI/ACI without requiring knowledge of the channel impulse response of the interference.

2013 Future Network Mobile Summit, 2013

2006 14th European Signal Processing Conference, Sep 1, 2006

This paper deals with the problem of designing widely-linear (WL) fractionally-spaced (FS) finite... more This paper deals with the problem of designing widely-linear (WL) fractionally-spaced (FS) finite-impulse response equalizers for both real-and complex-valued improper modulation schemes. Specifically, the synthesis of both WL-FS minimum mean-square error and zero-forcing equalizers is discussed, by deriving the mathematical conditions assuring perfect symbol recovery in the absence of noise. In a general framework, the feasibility of designing WL-FS blind equalizers based on the constant modulus criterion is also investigated, and both unconstrained and constrained designs are provided. The effectiveness of the proposed equalizers is corroborated by means of computer simulation results.

2000 10th European Signal Processing Conference, 2000

The problem of recovering a digital communication signal distorted by a linear time-invariant cha... more The problem of recovering a digital communication signal distorted by a linear time-invariant channel and contaminated by severe co-channel or adjacent-channel digital interference is addressed in this paper. The proposed linear periodically time-varying (LPTV) receiver jointly performs channel equalization and interference suppression, without requiring explicit knowledge or estimation of the interfering channel. Simulation results confirm the effectiveness of the proposed technique, whose performance exhibit a remarkable robustness with respect to varying interference power level.

Acoustics Speech and Signal Processing 1988 Icassp 88 1988 International Conference on, Mar 14, 2010

Recently, much progress has been made on the cross-layer optimization of video streams in multipl... more Recently, much progress has been made on the cross-layer optimization of video streams in multiple access networks. The key idea is to use the granular data structure of compressed video to trade quality with bits, and optimally prioritize transmissions given the available bandwidth, in order to obtain proportionally optimal video quality across video streams. Herein, we discuss the effect and potential benefit of using a cooperative-relay strategy in a wireless network, where proportionally optimal video schedules are computed via a multi-user Markov decision process. The idea is that feeble signals of nodes that are located far away from the destination can be enhanced via the cooperation of intermediate nodes, acting as cooperative relays. Our contribution is to indicate a possible solution that would require relatively modest changes to the multi-user optimization framework, while warranting a uniformly better experience to the video users thanks to cooperative coding.

Acoustics Speech and Signal Processing 1988 Icassp 88 1988 International Conference on, 2010

The problem of channel shortening equalization (CSE) for multiinput multi-output (MIMO) orthogona... more The problem of channel shortening equalization (CSE) for multiinput multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems is addressed. Relying on constrained minimization of the mean-output-energy (MOE) at the CSE output, we propose a blind channel shortening technique, which does not require a priori knowledge or estimation of the MIMO channel impulse responses to be shortened. Numerical results showing the attainable performance gain of the proposed method are reported.

2006 IEEE International Conference on Acoustics Speed and Signal Processing Proceedings, 2000

ABSTRACT Constrained optimization techniques, based on the maximum signal-to-noise-plus-interfere... more ABSTRACT Constrained optimization techniques, based on the maximum signal-to-noise-plus-interference (SINR) criterion,, are considered for joint equalization and narrowband interference (NBI) suppression in orthogonal frequency-division multiplexing (OFDM) systems. Specifically, we show that a recently proposed linear receiver (D. Darsena et al., 2005), which mitigates, in the minimum mean-output-energy sense, the NBI contribution at the receiver output, can be regarded as the solution of a constrained maximum-SINR optimization criterion and, moreover, admits an interesting three-stage decomposition. This decomposition improves the receiver robustness against errors in the estimated statistics of the received data and, most important, allows one to greatly simplify the channel estimation problem. Computer simulations are earned out to illustrate the performance improvements achievable by adopting the constrained maximum-SINR equalizer, in comparison with its unconstrained counterpart

Conference Record of the Thirty-Sixth Asilomar Conference on Signals, Systems and Computers, 2002., 2000

ABSTRACT This paper deals with blind multiuser detection for asynchronous multicarrier code-divis... more ABSTRACT This paper deals with blind multiuser detection for asynchronous multicarrier code-division multiple-access (MC-CDMA) systems. A two-stage linear multiuser detector is proposed, where the first stage performs preliminary disturbance mitigation, allowing thus the second stage, based on the constant modulus algorithm (CMA), to operate with nearly disturbance-free data. The proposed receiver is totally blind, since it needs only a coarse synchronization to the desired user's transmission and knowledge of its spreading code. The effectiveness of the proposed approach is corroborated by computer simulation results, which show that, even with small sample size values, the proposed detector achieves performances close to (and often superior than) those of the non-blind minimum-mean-square error (MMSE) receiver.

IEEE 5th Workshop on Signal Processing Advances in Wireless Communications, 2004., 2000

We propose a new blind channel identification method for multicarrler (MC) transmission systems e... more We propose a new blind channel identification method for multicarrler (MC) transmission systems employing noncircular modulation fonnats. To elLploit the noncircularity property of the signal constellation, the proposed algorithm relies on the subspace decomposition of the augmented vector obtained by stacking the received data ,'ector and its complex·conjugate version. Unlike recently proposed subspace· based techniques, this method allows one to successfully estimate the channel impulse re sponse under certain identifiability conditions, without requiring the introduction of additional redundancy in transmission (e.g., ,'ir tual carriers), and \\ithout resorting to o,'ersampling and/or multi ple antennas at the receh'er. Moreover, it is shown that blind cban nel identification can be performed satisfactorily also in the presen. ce of narrowband interference (NBJ), requiring onIy approlLimate rank determination of the NBI augmented autocorrelation matrix.

2007 IEEE 8th Workshop on Signal Processing Advances in Wireless Communications, 2007

We propose a blind adaptive channel-shortening method for designing finite-impulse response time-... more We propose a blind adaptive channel-shortening method for designing finite-impulse response time-domain equalizers (TEQs) in singleinput multiple-output systems employing multicarrier modulations. The proposed algorithm, which relies on a constrained minimization of the mean-output-energy at the TEQ output, does not require neither a priori knowledge of the channel impulse response nor transmission of training sequences. Moreover, the proposed TEQ is narrowband interference resistant and its synthesis only requires an upper bound (rather than the exact knowledge) of the channel order. * This work is partially supported by Italian National project Wireless 8O2.16 Multi-antenna mEsh Networks (WOMEN) under grant number 2005093248.

2015 IEEE International Conference on Communications (ICC), 2015

2015 IEEE Metrology for Aerospace (MetroAeroSpace), 2015

ABSTRACT This paper deals with the synthesis of a blind channel shortening algorithm for orthogon... more ABSTRACT This paper deals with the synthesis of a blind channel shortening algorithm for orthogonal frequency-division multiplexing (OFDM) systems operating over doubly selective wireless channels, a challenging scenario that is likely to happen in modern unmanned aircraft systems (UASs) data links. When the length of the OFDM cyclic prefix (CP) is smaller than the channel order, we propose to employ a blind linear time-varying (LTV) time-domain equalizer, which shortens the channel impulse response of the channel in the minimum mean-output energy (MMOE) sense, requiring only estimation of the second-order statistics of the received data. The equalizer design leverages on the complex-exponential (CE) basis expansion model (BEM) for the doubly selective channel, which naturally leads to a frequency-shift (FRESH) filter implementation. Monte Carlo computer simulations are carried out to assess the effectiveness of the proposed FRESH-MMOE channel shortener.

2014 European Conference on Networks and Communications (EuCNC), 2014

ABSTRACT We consider a wireless cooperative network, where communication between a source-destina... more ABSTRACT We consider a wireless cooperative network, where communication between a source-destination pair is assisted by multiple relaying nodes. To cope with the wideband nature of the wireless channel, all network nodes are equipped with multiple antennas and employ orthogonal frequency-division multiplexing (OFDM) modulation. Leveraging on an approximate yet accurate performance analysis of the network, carried out in terms of symbol error probability (SEP), a closed-form minimum-SEP optimal design of precoding and relaying matrices is proposed, which allows one to fully exploit the distributed diversity inherent to the cooperative approach, but requires accurate channel state information at the source and the relays. Monte Carlo numerical results are provided to assess the performance advantages that can be achieved by the proposed design.

2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications, 2008

A cross-layer approach, called CoopMAC, has been proposed recently to integrate cooperation at th... more A cross-layer approach, called CoopMAC, has been proposed recently to integrate cooperation at the physical layer with the medium access control sublayer, thereby achieving substantial throughput and delay performance improvements. CoopMAC capitalizes on the broadcast nature of wireless channels, recruiting a relay opportunistically and on the fly to support the communication of a particular source-destination pair. Herein, we study a cross-layer framework that uses randomized cooperative coding, and allows the simultaneous recruitment of multiple relays which collectively act as the antennas of a distributed transmission array, by simply randomizing the antenna code selection rule. We show that randomized cooperation not only alleviates the burden associated with the relay selection process, but also fully exploits the available spatial diversity.

2007 IEEE 8th Workshop on Signal Processing Advances in Wireless Communications, 2007

This paper deals with multiuser detection for multicarrier code-division multiple-access (MC-CDMA... more This paper deals with multiuser detection for multicarrier code-division multiple-access (MC-CDMA) systems, employing either zeropadded or cyclic-prefixed transmission techniques. For both systems, we consider widely-linear finite-impulse response (WL-FIR) estimators, which process both the received signal and its complex conjugate version. With regard to downlink configurations, it is shown that, if the number of users does not exceed a given threshold and their codes are appropriately designed, channel-irrespective WL-FIR zero-forcing symbol recovery is possible. In particular, some spreading code examples are provided, which satisfy our design rules.

In orthogonal-frequency-division-multiplexing (OFDM) systems, finite-impulse response (FIR) linea... more In orthogonal-frequency-division-multiplexing (OFDM) systems, finite-impulse response (FIR) linear precoders allow for perfect or zero-forcing (ZF) equalization of FIR channels (in the absence of noise). Recently, it has been shown that the noncircular or improper nature of some symbol constellations offers an intrinsic source of redundancy, which can be exploited to design efficient FIR widely-linear (WL) receiving structures for OFDM systems operating in the presence of narrowband interference (NBI). With regard to both cyclic-prefixed and zero-padded transmission techniques, it is shown in this paper that, with appropriately designed precoders, it is possible to synthesize in both cases WL-ZF universal equalizers, which guarantee perfect symbol recovery for any FIR channel and, at the same time, exhibit satisfactory NBI suppression capabilities.