Calin Vladeanu - Academia.edu (original) (raw)

Papers by Calin Vladeanu

Abstract—In this paper, a turbo trellis-coded spatial modulation (TTCSM) transmission scheme is p... more Abstract—In this paper, a turbo trellis-coded spatial modulation (TTCSM) transmission scheme is proposed. In trelliscoded spatial modulation (TCSM) scheme, the information bits used to select the transmit antenna index are encoded. In order to increase the performances of the TCSM scheme, a parallel concatenated encoding scheme can be used.

Abstract: Lack of frequency spectrum is becoming one of the major problems in the telecommunicati... more Abstract: Lack of frequency spectrum is becoming one of the major problems in the telecommunication field with the introduction of several new radio communication technologies. Cognitive Radio (CR) technology promises to be one possible solution to this problem, by allowing access of unlicensed users in licensed bands, based on an opportunistic approach and without interfering with the licensed (primary) user.

This paper investigates the chaos-based asynchronous direct sequence code-division multiple acces... more This paper investigates the chaos-based asynchronous direct sequence code-division multiple access (DS-CDMA) system performance optimization in accordance with spreading sequences set. The multiple access interference (MAI) power is estimated for conventional matched-filter receiver scheme, under the standard gaussian approximation (SGA) hypothesis, and minimized with respect to the auto-correlation function of the spreading sequences.

Abstract: Recently, a new family of recursive systematic convolutional (RSC) encoders over Galois... more Abstract: Recently, a new family of recursive systematic convolutional (RSC) encoders over Galois field GF (2^ N) was introduced. The present paper considers the parallel turbo trellis coded modulation (TTCM) scheme using these nonbinary encoders as constituent codes. Besides operating over a higher order Galois field, these encoders use a non-linear function, the left-circulate (LCIRC) function, to control the encoder states.

Cuvinte cheie. Egalizare turbo, filtru cu supraeşantionare, algoritmi SISO, filtru MMSE Rezumat. ... more Cuvinte cheie. Egalizare turbo, filtru cu supraeşantionare, algoritmi SISO, filtru MMSE Rezumat. În această lucrare se prezintă un egalizor cu intrare şi ieşire soft (SISO) optimizat în sensul minimizării erorii pătratice medie (MMSE), folosit în egalizarea turbo, în cazul în care semnalul recepţionat este supraeşantionat. Se va folosi un algoritm iterativ de reactualizare a coeficenţilor filtrului, adecvat transmisiei pe canale variabile în timp.

Abstract–This paper presents a new family of turbo codes whose the constituent codes have R≥ 1 no... more Abstract–This paper presents a new family of turbo codes whose the constituent codes have R≥ 1 non-binary inputs and R+1 outputs. We refer this family as the multi input non-binary turbo codes (MNBTC), which is very general. More specifically, we show that this family includes the multi-binary turbo-codes (MBTCs) that themselves include the classical binary turbo-codes (BTCs). Moreover, it also includes the turbo-codes with Reed Solomon codes as constituent codes.

Abstract This paper considers a minimum mean-squared error (MMSE) single user adaptive receiver f... more Abstract This paper considers a minimum mean-squared error (MMSE) single user adaptive receiver for the asynchronous direct-sequence code-division multiple-access (DS-CDMA) system, based on a gradient adaptive lattice (GAL) algorithm. Since the lattice predictor orthogonalizes the input signals this algorithm achieves a faster convergence rate than the transversal least-mean-square (LMS) algorithm.

Abstract:-In this paper we present a study of the receiver movement influence on the indoor wirel... more Abstract:-In this paper we present a study of the receiver movement influence on the indoor wireless communication system performances. We consider an optical code division multiple access (OCDMA) indoor wireless communication system with spectral encoding and evaluate its performances in cases of classical OCDMA and dynamic OCDMA. As the receiver moves increasingly away from transmitter the amount of power received in that place will be getting smaller and system performances are affected.

Abstract: This paper considers a minimum mean-squared error (MMSE) single user adaptive receiver ... more Abstract: This paper considers a minimum mean-squared error (MMSE) single user adaptive receiver for the asynchronous direct-sequence code-division multiple-access (DS-CDMA) system, based on the least-mean-square (LMS) algorithm. It is known that in this context the adaptive algorithm can be iterated several times during the same bit interval in order to achieve a faster convergence rate, which further reduces the length of the training sequence. The objective of this paper is twofold.

In this paper, trellis coded modulation (TCM) schemes are designed using recursive encoders over ... more In this paper, trellis coded modulation (TCM) schemes are designed using recursive encoders over Galois field GF (2N). These encoders are designed using the nonlinear left-circulate (LCIRC) function. The LCIRC function performs a bit left circulation over the representation word. Different encoding rates are obtained for these encoders when using different representation word lengths at the input and the output, denoted as Nin and N, respectively.

This paper reconsiders the Minimum Mean-Squared Error (MMSE) single user adaptive receiver for th... more This paper reconsiders the Minimum Mean-Squared Error (MMSE) single user adaptive receiver for the asynchronous Direct Sequence–Code Division Multiple Access (DS-CDMA) system. During the training period the classical MMSE receiver adapts the tap weights once every data bit interval. Our aim is to reduce the overhead introduced during the training period. This will be achieved by adapting the tap weights several times during each bit interval, in an iterative manner.

ABSTRACT The BER performances of asynchronous DS-CDMA systems using conventional matched-filter r... more ABSTRACT The BER performances of asynchronous DS-CDMA systems using conventional matched-filter receiver and multilevel chaotic spreading are estimated over a Rician fading selective channel. The paper completes the results of previous works dedicated to the optimization of system's BER performances by controlling the chaotic sequence generator.

Abstract—In this paper we consider an optical code division multiple access (OCDMA) indoor wirele... more Abstract—In this paper we consider an optical code division multiple access (OCDMA) indoor wireless communication system using spectral encoding and evaluate its performances in cases of classical OCDMA, dynamic OCDMA and OCDMA with deconvolution. We present an analysis of the receiver movement influence on the indoor wireless communications system performances.

Abstract: In this paper, quadrature amplitude modulation–trellis coded modulation (QAM-TCM) schem... more Abstract: In this paper, quadrature amplitude modulation–trellis coded modulation (QAM-TCM) schemes are designed using recursive convolutional (RC) encoders over Galois field GF (2^ N). These encoders are designed using the nonlinear leftcirculate (LCIRC) function. The LCIRC function performs a bit left circulation over the representation word. Different encoding rates are obtained for these encoders when using different representation wordlengths at the input and the output, denoted as Nin and N, respectively.

Most spatial modulation (SM) schemes in the literature use hard-output maximumlikelihood (ML) ant... more Most spatial modulation (SM) schemes in the literature use hard-output maximumlikelihood (ML) antenna index detection. In trellis coded spatial modulation (TCSM) scheme, the detection should be also performed for the transmitted symbol, while the sequence decoding is performed using a hard-output Viterbi algorithm.

Abstract The most common algorithms used for echo cancellation are the normalized least-mean-squa... more Abstract The most common algorithms used for echo cancellation are the normalized least-mean-square (NLMS) and the affine projection (AP). The classical versions of these algorithms use a constant step-size parameter and need to establish a tradeoff between several performance criteria eg, high convergence rate versus low misadjustment. In this paper, we present a class of variable step-size NLMS and AP algorithms, which are designed to recover the near-end signal from the error of the adaptive filter.

Abstract—The security of transmitted digital information through a channel, against passive or ac... more Abstract—The security of transmitted digital information through a channel, against passive or active attacks, becomes more and more important. The use of a 1-D chaotic signal to mask useful information and to make it unrecognizable by an eavesdropper is a field of research in full expansion. In order to obtain such high-level security; chaotic generators used to encrypt digital data, must have desirable dynamical statistical properties such as: noise-like autocorrelation, cross-correlation, uniformity, attractors, etc.

… (AICT), 2010 Sixth …, Jan 1, 2010

Abstract In this paper, parallel turbo phase shift keying-trellis coded modulation (Turbo PSK-TCM... more Abstract In this paper, parallel turbo phase shift keying-trellis coded modulation (Turbo PSK-TCM) schemes are designed using recursive convolutional encoders over Galois field GF (2 N). These encoders are designed using the nonlinear left-circulate (LCIRC) function. The LCIRC function performs a bit left circulation over the representation word. An optimum 1-delay GF (2 N) recursive convolutional encoder scheme using LCIRC (RC-LCIRC) is proposed for PSK-TCM schemes. The minimum Euclidian distance is estimated for these ...

… (COMM), 2010 8th …, Jan 1, 2010

In this paper, we propose a fast and robust scheme for image encryption including a new chaotic g... more In this paper, we propose a fast and robust scheme for image encryption including a new chaotic generator. The proposed crypto-system uses a variable block cipher length (8, 128, and 512) with different modes: cipher block chaining (CBC), output feedback (OFB), cipher feedback (CFB) and counter (CTR). The fastness and robustness properties of our cryptosystem are determined by the chaotic generator using a 32-bits finite precision with integer representation to facilitate hardware implementation, and by a keystream permutation using a 2D-cat map with chaotic control parameters. The chaotic generator is constructed with two non linear (the skew tent map) IIR filters. To quantify the security level of the proposed cryptosystem, we analyze the global dynamical properties of the chaotic generator using the NIST (National Institute of Standards and Technology) test, and we show that, the algorithm can resist the statistical and differential attacks; it also passed the key sensitivity test. Moreover, the algorithm has a large key space. The experimental results indicate that the scheme is secure, efficient, and faster than conventional advanced encryption standard (AES).

Computing in the Global …, Jan 1, 2007

Abstract This paper analyzes the behavior of the Least Mean Square (LMS) adaptive algorithm in th... more Abstract This paper analyzes the behavior of the Least Mean Square (LMS) adaptive algorithm in the minimum mean-squared error (MMSE) single user adaptive receiver for the asynchronous direct sequence-code division multiple access (DS-CDMA) system. It is known that in this context the adaptive algorithm can be iterated several times during the same bit interval in order to achieve a faster convergence rate for the receiver, which further reduces the length of the training sequence. Instead of using such multiple iterations we ...

Abstract—In this paper, a turbo trellis-coded spatial modulation (TTCSM) transmission scheme is p... more Abstract—In this paper, a turbo trellis-coded spatial modulation (TTCSM) transmission scheme is proposed. In trelliscoded spatial modulation (TCSM) scheme, the information bits used to select the transmit antenna index are encoded. In order to increase the performances of the TCSM scheme, a parallel concatenated encoding scheme can be used.

Abstract: Lack of frequency spectrum is becoming one of the major problems in the telecommunicati... more Abstract: Lack of frequency spectrum is becoming one of the major problems in the telecommunication field with the introduction of several new radio communication technologies. Cognitive Radio (CR) technology promises to be one possible solution to this problem, by allowing access of unlicensed users in licensed bands, based on an opportunistic approach and without interfering with the licensed (primary) user.

This paper investigates the chaos-based asynchronous direct sequence code-division multiple acces... more This paper investigates the chaos-based asynchronous direct sequence code-division multiple access (DS-CDMA) system performance optimization in accordance with spreading sequences set. The multiple access interference (MAI) power is estimated for conventional matched-filter receiver scheme, under the standard gaussian approximation (SGA) hypothesis, and minimized with respect to the auto-correlation function of the spreading sequences.

Abstract: Recently, a new family of recursive systematic convolutional (RSC) encoders over Galois... more Abstract: Recently, a new family of recursive systematic convolutional (RSC) encoders over Galois field GF (2^ N) was introduced. The present paper considers the parallel turbo trellis coded modulation (TTCM) scheme using these nonbinary encoders as constituent codes. Besides operating over a higher order Galois field, these encoders use a non-linear function, the left-circulate (LCIRC) function, to control the encoder states.

Cuvinte cheie. Egalizare turbo, filtru cu supraeşantionare, algoritmi SISO, filtru MMSE Rezumat. ... more Cuvinte cheie. Egalizare turbo, filtru cu supraeşantionare, algoritmi SISO, filtru MMSE Rezumat. În această lucrare se prezintă un egalizor cu intrare şi ieşire soft (SISO) optimizat în sensul minimizării erorii pătratice medie (MMSE), folosit în egalizarea turbo, în cazul în care semnalul recepţionat este supraeşantionat. Se va folosi un algoritm iterativ de reactualizare a coeficenţilor filtrului, adecvat transmisiei pe canale variabile în timp.

Abstract–This paper presents a new family of turbo codes whose the constituent codes have R≥ 1 no... more Abstract–This paper presents a new family of turbo codes whose the constituent codes have R≥ 1 non-binary inputs and R+1 outputs. We refer this family as the multi input non-binary turbo codes (MNBTC), which is very general. More specifically, we show that this family includes the multi-binary turbo-codes (MBTCs) that themselves include the classical binary turbo-codes (BTCs). Moreover, it also includes the turbo-codes with Reed Solomon codes as constituent codes.

Abstract This paper considers a minimum mean-squared error (MMSE) single user adaptive receiver f... more Abstract This paper considers a minimum mean-squared error (MMSE) single user adaptive receiver for the asynchronous direct-sequence code-division multiple-access (DS-CDMA) system, based on a gradient adaptive lattice (GAL) algorithm. Since the lattice predictor orthogonalizes the input signals this algorithm achieves a faster convergence rate than the transversal least-mean-square (LMS) algorithm.

Abstract:-In this paper we present a study of the receiver movement influence on the indoor wirel... more Abstract:-In this paper we present a study of the receiver movement influence on the indoor wireless communication system performances. We consider an optical code division multiple access (OCDMA) indoor wireless communication system with spectral encoding and evaluate its performances in cases of classical OCDMA and dynamic OCDMA. As the receiver moves increasingly away from transmitter the amount of power received in that place will be getting smaller and system performances are affected.

Abstract: This paper considers a minimum mean-squared error (MMSE) single user adaptive receiver ... more Abstract: This paper considers a minimum mean-squared error (MMSE) single user adaptive receiver for the asynchronous direct-sequence code-division multiple-access (DS-CDMA) system, based on the least-mean-square (LMS) algorithm. It is known that in this context the adaptive algorithm can be iterated several times during the same bit interval in order to achieve a faster convergence rate, which further reduces the length of the training sequence. The objective of this paper is twofold.

In this paper, trellis coded modulation (TCM) schemes are designed using recursive encoders over ... more In this paper, trellis coded modulation (TCM) schemes are designed using recursive encoders over Galois field GF (2N). These encoders are designed using the nonlinear left-circulate (LCIRC) function. The LCIRC function performs a bit left circulation over the representation word. Different encoding rates are obtained for these encoders when using different representation word lengths at the input and the output, denoted as Nin and N, respectively.

This paper reconsiders the Minimum Mean-Squared Error (MMSE) single user adaptive receiver for th... more This paper reconsiders the Minimum Mean-Squared Error (MMSE) single user adaptive receiver for the asynchronous Direct Sequence–Code Division Multiple Access (DS-CDMA) system. During the training period the classical MMSE receiver adapts the tap weights once every data bit interval. Our aim is to reduce the overhead introduced during the training period. This will be achieved by adapting the tap weights several times during each bit interval, in an iterative manner.

ABSTRACT The BER performances of asynchronous DS-CDMA systems using conventional matched-filter r... more ABSTRACT The BER performances of asynchronous DS-CDMA systems using conventional matched-filter receiver and multilevel chaotic spreading are estimated over a Rician fading selective channel. The paper completes the results of previous works dedicated to the optimization of system's BER performances by controlling the chaotic sequence generator.

Abstract—In this paper we consider an optical code division multiple access (OCDMA) indoor wirele... more Abstract—In this paper we consider an optical code division multiple access (OCDMA) indoor wireless communication system using spectral encoding and evaluate its performances in cases of classical OCDMA, dynamic OCDMA and OCDMA with deconvolution. We present an analysis of the receiver movement influence on the indoor wireless communications system performances.

Abstract: In this paper, quadrature amplitude modulation–trellis coded modulation (QAM-TCM) schem... more Abstract: In this paper, quadrature amplitude modulation–trellis coded modulation (QAM-TCM) schemes are designed using recursive convolutional (RC) encoders over Galois field GF (2^ N). These encoders are designed using the nonlinear leftcirculate (LCIRC) function. The LCIRC function performs a bit left circulation over the representation word. Different encoding rates are obtained for these encoders when using different representation wordlengths at the input and the output, denoted as Nin and N, respectively.

Most spatial modulation (SM) schemes in the literature use hard-output maximumlikelihood (ML) ant... more Most spatial modulation (SM) schemes in the literature use hard-output maximumlikelihood (ML) antenna index detection. In trellis coded spatial modulation (TCSM) scheme, the detection should be also performed for the transmitted symbol, while the sequence decoding is performed using a hard-output Viterbi algorithm.

Abstract The most common algorithms used for echo cancellation are the normalized least-mean-squa... more Abstract The most common algorithms used for echo cancellation are the normalized least-mean-square (NLMS) and the affine projection (AP). The classical versions of these algorithms use a constant step-size parameter and need to establish a tradeoff between several performance criteria eg, high convergence rate versus low misadjustment. In this paper, we present a class of variable step-size NLMS and AP algorithms, which are designed to recover the near-end signal from the error of the adaptive filter.

Abstract—The security of transmitted digital information through a channel, against passive or ac... more Abstract—The security of transmitted digital information through a channel, against passive or active attacks, becomes more and more important. The use of a 1-D chaotic signal to mask useful information and to make it unrecognizable by an eavesdropper is a field of research in full expansion. In order to obtain such high-level security; chaotic generators used to encrypt digital data, must have desirable dynamical statistical properties such as: noise-like autocorrelation, cross-correlation, uniformity, attractors, etc.

… (AICT), 2010 Sixth …, Jan 1, 2010

Abstract In this paper, parallel turbo phase shift keying-trellis coded modulation (Turbo PSK-TCM... more Abstract In this paper, parallel turbo phase shift keying-trellis coded modulation (Turbo PSK-TCM) schemes are designed using recursive convolutional encoders over Galois field GF (2 N). These encoders are designed using the nonlinear left-circulate (LCIRC) function. The LCIRC function performs a bit left circulation over the representation word. An optimum 1-delay GF (2 N) recursive convolutional encoder scheme using LCIRC (RC-LCIRC) is proposed for PSK-TCM schemes. The minimum Euclidian distance is estimated for these ...

… (COMM), 2010 8th …, Jan 1, 2010

In this paper, we propose a fast and robust scheme for image encryption including a new chaotic g... more In this paper, we propose a fast and robust scheme for image encryption including a new chaotic generator. The proposed crypto-system uses a variable block cipher length (8, 128, and 512) with different modes: cipher block chaining (CBC), output feedback (OFB), cipher feedback (CFB) and counter (CTR). The fastness and robustness properties of our cryptosystem are determined by the chaotic generator using a 32-bits finite precision with integer representation to facilitate hardware implementation, and by a keystream permutation using a 2D-cat map with chaotic control parameters. The chaotic generator is constructed with two non linear (the skew tent map) IIR filters. To quantify the security level of the proposed cryptosystem, we analyze the global dynamical properties of the chaotic generator using the NIST (National Institute of Standards and Technology) test, and we show that, the algorithm can resist the statistical and differential attacks; it also passed the key sensitivity test. Moreover, the algorithm has a large key space. The experimental results indicate that the scheme is secure, efficient, and faster than conventional advanced encryption standard (AES).

Computing in the Global …, Jan 1, 2007

Abstract This paper analyzes the behavior of the Least Mean Square (LMS) adaptive algorithm in th... more Abstract This paper analyzes the behavior of the Least Mean Square (LMS) adaptive algorithm in the minimum mean-squared error (MMSE) single user adaptive receiver for the asynchronous direct sequence-code division multiple access (DS-CDMA) system. It is known that in this context the adaptive algorithm can be iterated several times during the same bit interval in order to achieve a faster convergence rate for the receiver, which further reduces the length of the training sequence. Instead of using such multiple iterations we ...