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Papers by M Reza Khanzadi

2012 IEEE …, Jan 1, 2012

In this work, the problem of receiver design for phase noise estimation and data detection in the... more In this work, the problem of receiver design for phase noise estimation and data detection in the presence of oscillator phase noise in a point-to-point multiple-input multiple-output (MIMO) system is addressed. First, we discuss some interesting and challenging aspects in receiver design for MIMO systems in the presence of Wiener phase noise. Then, using the variational Bayesian (VB) framework, a joint iterative phase noise estimator and symbol detector are developed based on inverse Gibbs or variational free energy maximization. Further, the symbol error probability (SEP) of the newly proposed iterative scheme is compared with the optimal maximum likelihood (ML) detector with perfect phase information for 16-phase shift keying (PSK) and 16-quadrature amplitude modulation (QAM) schemes.

In this paper, first, a new discrete-time model of phase noise for digital communication systems,... more In this paper, first, a new discrete-time model of phase noise for digital communication systems, which is a more accurate model compared to the classical Wiener model, is proposed based on a comprehensive continuous-time representation of time-varying phase noise, and statistical characteristics of this model are derived. Next, the non-data-aided (NDA) and decision-directed (DD) maximum-likelihood (ML) estimators of time-varying phase noise, using the proposed discrete-time model are derived. To evaluate the performance of the proposed estimators, the Cramer-Rao lower bound (CRLB) for each estimation approach is derived and by using Monte-Carlo simulations it is shown that the mean-square error (MSE) of the proposed estimators converges to the CRLB at moderate signal-to-noise ratios (SNR). Finally, simulation results show that the proposed estimators outperform existing estimation methods as the variance of the phase noise process increases.

… (WiAD), 2010 6th …, Jan 1, 2010

This paper proposes a new modulation method for an uncoded cognitive transmission (secondary user... more This paper proposes a new modulation method for
an uncoded cognitive transmission (secondary user transmission)
in presence of a Primary User (PU) for the AWGN channel.
Interference of the PU is assumed to be known at the transmitter
of Cognitive User (CU) non-causally. Based on this knowledge,
for the design of the modulator and demodulator of the CU,
a symbol by symbol approach is studied which can fulfill the
coexistence conditions of the CU and the PU of the band. In this
scheme, the modulator and demodulator of CU are designed
jointly by solving an optimization problem to mitigate the
interference of the PU and minimize the symbol error probability
(Pe) in CU’s communication link without increasing the symbol
error probability (Pe) of the PU. The proposed method is a
modulation approach in a single (complex-valued) dimension
rather than a high dimensional coding scheme. Although this
one-dimensional method is not capacity achieving, we show it still
has a remarkable performance with low amount of complexity.
An implementation algorithm for our modulation method is also
presented and the performance of this method is evaluated by
experimental results.

… and Biomimetics, Jan 1, 2007

The result of practical implementation of intelligent compensation of friction to achieve precisi... more The result of practical implementation of intelligent compensation of friction to achieve precision motion control of X-Y table is presented here. It uses LOLIMOT algorithm to make a neuro-fuzzy model that predicts the effect of friction on the system output. This predictor is used with inverse of ideal system model as a friction compensator. Implementation and applying this compensator to the system results mean tracking error reduction for a desired path. Moreover, the disturbances implied by the friction are highly improved.

publications.lib.chalmers.se

This paper proposes a new modulation method for an uncoded cognitive transmission (secondary user... more This paper proposes a new modulation method for an uncoded cognitive transmission (secondary user transmission) in presence of a Primary User (PU) for AWGN and time-varying flat-fading channels. Interference symbol of the PU is assumed to be known at the transmitter of the Cognitive User (CU) beforehand. Based on this knowledge and using a symbol by symbol approach, we design a CU modulation which can fulfill the coexistence conditions of the CU and the PU. The proposed method is a low-complexity modulation approach in a single (complex-valued) dimension rather than a high dimensional coding scheme, but still it achieves good performance. The robustness of the method is also investigated in case of having an imperfect knowledge about the PU transmitted symbols. An implementation algorithm for our modulation method is presented and its performance is evaluated by experiments.

… Spring, Taipei, Taiwan, Jan 1, 2010

We consider clustered wireless networks, where transceivers in a cluster use a time-slotted mecha... more We consider clustered wireless networks, where transceivers in a cluster use a time-slotted mechanism (TDMA) to access a wireless channel that is shared among several clusters. Earlier work has demonstrated that a significant increase in network throughput can be achieved if all the schedules are optimized jointly. However, a drawback of this approach is the prohibitive level of computational complexity is required when a network with a large number of clusters and time-slots is to be scheduled. In this paper, we propose a modification to our previously proposed algorithm which allows for the complexity to be adjusted to the available processing power, provided some minimum processing power is available. This is achieved by carefully reducing the number of interfering clusters considered when scheduling a cluster. In addition, we propose and evaluate two heuristic methods of discarding the less significant clusters. While the optimality of the obtained schedule is not proven, our results demonstrate that large gains are consistently attainable.

2012 IEEE …, Jan 1, 2012

In this work, the problem of receiver design for phase noise estimation and data detection in the... more In this work, the problem of receiver design for phase noise estimation and data detection in the presence of oscillator phase noise in a point-to-point multiple-input multiple-output (MIMO) system is addressed. First, we discuss some interesting and challenging aspects in receiver design for MIMO systems in the presence of Wiener phase noise. Then, using the variational Bayesian (VB) framework, a joint iterative phase noise estimator and symbol detector are developed based on inverse Gibbs or variational free energy maximization. Further, the symbol error probability (SEP) of the newly proposed iterative scheme is compared with the optimal maximum likelihood (ML) detector with perfect phase information for 16-phase shift keying (PSK) and 16-quadrature amplitude modulation (QAM) schemes.

In this paper, first, a new discrete-time model of phase noise for digital communication systems,... more In this paper, first, a new discrete-time model of phase noise for digital communication systems, which is a more accurate model compared to the classical Wiener model, is proposed based on a comprehensive continuous-time representation of time-varying phase noise, and statistical characteristics of this model are derived. Next, the non-data-aided (NDA) and decision-directed (DD) maximum-likelihood (ML) estimators of time-varying phase noise, using the proposed discrete-time model are derived. To evaluate the performance of the proposed estimators, the Cramer-Rao lower bound (CRLB) for each estimation approach is derived and by using Monte-Carlo simulations it is shown that the mean-square error (MSE) of the proposed estimators converges to the CRLB at moderate signal-to-noise ratios (SNR). Finally, simulation results show that the proposed estimators outperform existing estimation methods as the variance of the phase noise process increases.

… (WiAD), 2010 6th …, Jan 1, 2010

This paper proposes a new modulation method for an uncoded cognitive transmission (secondary user... more This paper proposes a new modulation method for
an uncoded cognitive transmission (secondary user transmission)
in presence of a Primary User (PU) for the AWGN channel.
Interference of the PU is assumed to be known at the transmitter
of Cognitive User (CU) non-causally. Based on this knowledge,
for the design of the modulator and demodulator of the CU,
a symbol by symbol approach is studied which can fulfill the
coexistence conditions of the CU and the PU of the band. In this
scheme, the modulator and demodulator of CU are designed
jointly by solving an optimization problem to mitigate the
interference of the PU and minimize the symbol error probability
(Pe) in CU’s communication link without increasing the symbol
error probability (Pe) of the PU. The proposed method is a
modulation approach in a single (complex-valued) dimension
rather than a high dimensional coding scheme. Although this
one-dimensional method is not capacity achieving, we show it still
has a remarkable performance with low amount of complexity.
An implementation algorithm for our modulation method is also
presented and the performance of this method is evaluated by
experimental results.

… and Biomimetics, Jan 1, 2007

The result of practical implementation of intelligent compensation of friction to achieve precisi... more The result of practical implementation of intelligent compensation of friction to achieve precision motion control of X-Y table is presented here. It uses LOLIMOT algorithm to make a neuro-fuzzy model that predicts the effect of friction on the system output. This predictor is used with inverse of ideal system model as a friction compensator. Implementation and applying this compensator to the system results mean tracking error reduction for a desired path. Moreover, the disturbances implied by the friction are highly improved.

publications.lib.chalmers.se

This paper proposes a new modulation method for an uncoded cognitive transmission (secondary user... more This paper proposes a new modulation method for an uncoded cognitive transmission (secondary user transmission) in presence of a Primary User (PU) for AWGN and time-varying flat-fading channels. Interference symbol of the PU is assumed to be known at the transmitter of the Cognitive User (CU) beforehand. Based on this knowledge and using a symbol by symbol approach, we design a CU modulation which can fulfill the coexistence conditions of the CU and the PU. The proposed method is a low-complexity modulation approach in a single (complex-valued) dimension rather than a high dimensional coding scheme, but still it achieves good performance. The robustness of the method is also investigated in case of having an imperfect knowledge about the PU transmitted symbols. An implementation algorithm for our modulation method is presented and its performance is evaluated by experiments.

… Spring, Taipei, Taiwan, Jan 1, 2010

We consider clustered wireless networks, where transceivers in a cluster use a time-slotted mecha... more We consider clustered wireless networks, where transceivers in a cluster use a time-slotted mechanism (TDMA) to access a wireless channel that is shared among several clusters. Earlier work has demonstrated that a significant increase in network throughput can be achieved if all the schedules are optimized jointly. However, a drawback of this approach is the prohibitive level of computational complexity is required when a network with a large number of clusters and time-slots is to be scheduled. In this paper, we propose a modification to our previously proposed algorithm which allows for the complexity to be adjusted to the available processing power, provided some minimum processing power is available. This is achieved by carefully reducing the number of interfering clusters considered when scheduling a cluster. In addition, we propose and evaluate two heuristic methods of discarding the less significant clusters. While the optimality of the obtained schedule is not proven, our results demonstrate that large gains are consistently attainable.