A study is made of a cross-coupled phase-locked loop (CCPLL) used for separation of close sinusoids with slowly varying frequencies. It is assumed that the sinusoids have equal amplitudes, and it is shown that the CCPLL system can... more
A study is made of a cross-coupled phase-locked loop (CCPLL) used for separation of close sinusoids with slowly varying frequencies. It is assumed that the sinusoids have equal amplitudes, and it is shown that the CCPLL system can effectively separate two sine signals with an observation interval T<1/ Delta f. An analysis in the presence of noise is also given. It is shown that a satisfactory phase estimation can be achieved for SNR >or=15 dB. The result has application in fields such as ranging, symbol synchronization, and carrier recovery for coherent demodulation.<<ETX>>
Research Interests:
The closed-loop self-synchronized constrained notch filter (CLSS-CNF) is proposed, and its ability for retrieval of narrowband signals corrupted by a strong FM interference is studied. Self-synchronization is achieved through the... more
The closed-loop self-synchronized constrained notch filter (CLSS-CNF) is proposed, and its ability for retrieval of narrowband signals corrupted by a strong FM interference is studied. Self-synchronization is achieved through the estimation of the instantaneous phase of the FM interference to control time-varying coefficients of SC-CNF by using a closed-loop structure. The CLSS-CNF can overcome the tracking capability threshold of a
Research Interests:
Research Interests:
Research Interests:
Research Interests:
A Multiple Input Single Output (MISO) system based on Maximum Ratio Transmission (MRT) precoding with nonlinear Power Amplifiers (PAs) is considered. The nonlinear PAs distort the transmitted signal causing performance degradation. The... more
A Multiple Input Single Output (MISO) system based on Maximum Ratio Transmission (MRT) precoding with nonlinear Power Amplifiers (PAs) is considered. The nonlinear PAs distort the transmitted signal causing performance degradation. The common approach to mitigating nonlinear distortions is linearization of the PAs. For the MISO system we propose to apply a more generic approach in the form of an entire nonlinear MISO channel linearization, applied jointly for all PAs. It is shown that the results of this approach outperform those of the approach based on local linearization of each PA separately. An iterative technique is proposed to implement the entire MISO channel linearization. This technique requires knowledge of the channel state information and a model of the PAs at the transmitter. The performance of separate local and collective joint linearization is evaluated and compared in terms of the Symbol Error Rate (SER).
Research Interests:
... A. PAR It is well known that when is large, the transmit multi-carrier signals in (1 ... the se-quential signal transmission into independent symbols allows working with each multicarrier vector independently. ... We will assume that... more
... A. PAR It is well known that when is large, the transmit multi-carrier signals in (1 ... the se-quential signal transmission into independent symbols allows working with each multicarrier vector independently. ... We will assume that the out-of-band terms are filtered at the receiver input ...
Research Interests: Mathematics, Approximation Theory, Computer Science, Optimization techniques, Algorithm, and 15 moreMaximum Likelihood, Iterative Decoding, Degradation, Mutual Information, Maximum Likelihood Estimation, Nonlinear system, Nonlinear Model, Gradient Descent Algorithm, Detection Theory, Nonlinear Distortion, Electrical And Electronic Engineering, Amplifiers, Maximum Likelihood detection, OFDM modulation, and FREQUENCY DIVISION MULTIPLEXING
In this work we consider an OFDM-SDMA downlink with a real life, nonlinear Power Amplifier (PA). It is well known that a nonlinear PA produces nonlinear distortions. We propose a novel iterative algorithm based on Zero Forcing (ZF)... more
In this work we consider an OFDM-SDMA downlink with a real life, nonlinear Power Amplifier (PA). It is well known that a nonlinear PA produces nonlinear distortions. We propose a novel iterative algorithm based on Zero Forcing (ZF) precoding to cancel the nonlinear distortions seen at the mobile devices while preserving the interference-free reception due to ZF. The proposed algorithm also keeps the out-of-band radiation of the transmitted signals low, in order to satisfy spectral purity requirements. For a low Back-Off (BO) scenario, where the nonlinear distortions are strong, the proposed algorithm shows a much lower Symbol Error Rate (SER) and much higher power efficiency than the well known ZF-SDMA with a real life PA.
Research Interests:
The influence of nonlinear power amplifiers (PAs) on the performance of multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems is investigated. A “full” MIMO scheme with transmitters (TX) precoding... more
The influence of nonlinear power amplifiers (PAs) on the performance of multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems is investigated. A “full” MIMO scheme with transmitters (TX) precoding and receivers (RX) decoding is considered. It is shown, under assumption of high order OFDM and frequency selective channel, that the ratio between the useful signal and the nonlinear distortions is proportional to the number of TX antennas, i.e., the influence of the nonlinear distortions decreases as the number of TX antennas increases. The distortion reduction factor (DRF) is proposed as a performance metric for MIMO-OFDM systems with nonlinear PAs. A general formula for signal to distortion and noise ratio is obtained for the nonlinear PA with memory, described by the Wiener-Hammerstein (WH) model. Special cases of MIMO, such as maximum ratio transmission (MRT) and maximum ratio combining (MRC), are considered. A full agreement between the theoretical and simulation results is obtained. The main contribution of this paper is in a statement that TX processing reduces the effect of nonlinear distortions. This is obtained by novel approach for analysis of the MIMO-OFDM systems with nonlinear PAs with memory.
Research Interests:
Breathing monitors have become the all-important cornerstone of a wide variety of commercial and personal safety applications, ranging from elderly care to baby monitoring. Many such monitors exist in the market, some, with vital signs... more
Breathing monitors have become the all-important cornerstone of a wide variety of commercial and personal safety applications, ranging from elderly care to baby monitoring. Many such monitors exist in the market, some, with vital signs monitoring capabilities, but none remote. This paper presents a simple, yet efficient, real time method of extracting the subject's breathing sinus rhythm. Points of interest are detected on the subject's body, and the corresponding optical flow is estimated and tracked using the well known Lucas-Kanade algorithm on a frame by frame basis. A generalized likelihood ratio test is then utilized on each of the many interest points to detect which is moving in harmonic fashion. Finally, a spectral estimation algorithm based on Pisarenko harmonic decomposition tracks the harmonic frequency in real time, and a fusion maximum likelihood algorithm optimally estimates the breathing rate using all points considered. The results show a maximal error of 1 ...
Research Interests:
The influence of a nonlinear power amplifier on the performance of OFDM-MRT is investigated. It is shown that the ratio between the useful signal and the nonlinear distortions is proportional to the number of TX antennas, i.e., the... more
The influence of a nonlinear power amplifier on the performance of OFDM-MRT is investigated. It is shown that the ratio between the useful signal and the nonlinear distortions is proportional to the number of TX antennas, i.e., the influence of the nonlinear distortions decreases as the number of TX antennas increases. The Distortion Reduction Factor (DRF) is proposed as a performance metric for multi-antenna systems with nonlinear power amplifier. Considering the nonlinear power amplifier in each transmitting branch, a general formula for signal to distortions and noise ratio in the receiver is obtained and symbol error rate is computed. The MRT is compared to MRC and SISO. It is shown that for a low noise scenario the performance of MRT is much better than that of MRC. Full agreement of the theoretical and simulation results is obtained.
Research Interests:
Research Interests:
Remote sensing of elderlies' call for help is of great interest to caregivers, the elderly's family, and, of course, to the elderly who most often doesn't want to be bothered with a wearable device or cannot physically reach... more
Remote sensing of elderlies' call for help is of great interest to caregivers, the elderly's family, and, of course, to the elderly who most often doesn't want to be bothered with a wearable device or cannot physically reach the panic button. According to the center for disease control and prevention (CDC), 2.5 million elderlies are treated in emergency rooms due to fall injuries. Personal emergency response systems (PERS), also known as panic buttons or medical alerts, are very common in the industry. Some of them require the injured person to operate, some are passive but have to be on the injured person body in the form of a necklace or a wrist band. We propose a single transmitter (TX), single receiver (RX), fully remote ultrasonic radar system for classifying a call for help signal, which only requires the person to wave one of her/his hands for 3 seconds. A simple, yet robust algorithm is employed to classify the movement extracted out of the phase of the received signal emitted from a 40 kHz continuous-wave (CW) ultrasonic transmitter. The proposed algorithm is highly immune to thermal noise and employs a novel real time, optimal Doppler estimation without the use of spectral analysis algorithms such as the Fourier transform.
Research Interests:
ABSTRACT This paper investigates the achievable rate of multicarrier systems with non-linear distortion caused by high power amplifier (HPA) at the transmitter. We derive mutual information expressions for several non-linear models of... more
ABSTRACT This paper investigates the achievable rate of multicarrier systems with non-linear distortion caused by high power amplifier (HPA) at the transmitter. We derive mutual information expressions for several non-linear models of HPA. Specific results are given for different values of the input backoff. It is shown that for some cases, linearization of HPA is not the best strategy.
Research Interests:
This paper deals with a Maximum Likelihood (ML) receiver for a Single Carrier (SC) signal distorted by a nonlinear Power Amplifier (PA). The well known optimal Matched Filter (MF) loses its optimality when a nonlinear PA is considered. We... more
This paper deals with a Maximum Likelihood (ML) receiver for a Single Carrier (SC) signal distorted by a nonlinear Power Amplifier (PA). The well known optimal Matched Filter (MF) loses its optimality when a nonlinear PA is considered. We first propose an optimal receiver based on the ML criterion taking into account the PA nonlinearity. In case of a Additive White Gaussian Noise (AWGN), the ML receiver has to find the minimum Euclidean distance between the received vector and all nonlinearly distorted vectors that the transmitter may send. The exhaustive search solution of this problem has exponential complexity. To reduce the complexity, we propose a sub-optimal receiver that minimizes the Euclidean distance, seen as a cost function, using the Gradient Descent (GD) algorithm. We also present a low complexity version of the GD based receiver which is suitable for a parallel processing implementation. Comparative study of Symbol Error Rate (SER) performance of the proposed receiver against the optimal SC MF based receiver is given.
Research Interests:
OFDM signal suffers from high Peak to Average Power Ratio (PAPR). This dictates the necessity to drive the nonlinear power amplifier with high back-off, which leads to low power amplifier efficiency. In this paper we consider system that... more
OFDM signal suffers from high Peak to Average Power Ratio (PAPR). This dictates the necessity to drive the nonlinear power amplifier with high back-off, which leads to low power amplifier efficiency. In this paper we consider system that contains Iterative Clipping and Filtering (ICF) at the transmitter for PAPR reduction and modified iterative receiver (MIR) for demodulation. The MIR demodulate the distorted received signal. The distortions are created by the ICF and the nonlinear PA. The system architecture provides two main degrees of freedom given by the two back-offs: BO1 for ICF and BO2 for the power amplifier. We suggest to exploit these degrees of freedom in order to optimize the system performance expressed by a triplet: power efficiency (PE), adjacent channel power ratio (ACPR) and symbol error rate (SER). The optimal pair [BO1 BO2] depends on the priority among ACPR, SER and PE. Once the priority is determined, the optimal pair [BO1 BO2] that optimizes the system performa...
Research Interests:
A method of retrieval of a multitone corrupted by a strong wide-band FM interference is presented. The input mixture is transformed into a new time domain, resulting in a concentration of the FM interference around a chosen frequency;... more
A method of retrieval of a multitone corrupted by a strong wide-band FM interference is presented. The input mixture is transformed into a new time domain, resulting in a concentration of the FM interference around a chosen frequency; this interference is then rejected by a constrained notch filter with a fixed notch point. Time warping is implemented through nonequally spaced sampling. The proposed method provides results superior to those of conventional adaptive processing, which fails to track the parameters of an FM interference with significantly large frequency deviations.
The spectral subtraction approach has become almost standard in speech enhancement because it is relatively easy to understand and implement. The major drawback of the spectral subtraction method is that it leaves residual noise with... more
The spectral subtraction approach has become almost standard in speech enhancement because it is relatively easy to understand and implement. The major drawback of the spectral subtraction method is that it leaves residual noise with annoying noticeable tonal characteristics referred to as musical noise. For low SNR the perceived effect of the "musical noise" is close to that of the additive noise. In the present work we propose to reduce the musical noise by applying the output of a standard spectral subtractor to a constrained high order notch filter which suppresses the "musical noise". The filtration process distorts the speech signal. It is possible to reduce the level of distortion if the speech signal is preprocessed properly before it is contaminated by the noise. It will be demonstrated that the proposed method is superior to the standard spectral subtraction specially for low SNR. A comprehensive listening test indicated that for segmental SNR= −12dB, 7...
Research Interests:
Research Interests:
Research Interests:
ABSTRACT An application of a constrained notch filter (CNF) for filtering a sine signal with arbitrary varying frequency is considered. It is shown that the concept of CNF can be easily extended to time-varying CNF (TVCNF) whose... more
ABSTRACT An application of a constrained notch filter (CNF) for filtering a sine signal with arbitrary varying frequency is considered. It is shown that the concept of CNF can be easily extended to time-varying CNF (TVCNF) whose coefficients vary with time according to the rule of frequency variation of the considered FM signal. Such a TVCNF is able to reject the FM signal and at the same time remain transparent to any other signal. The main problem in TVCNF implementation is to provide a proper control (synchronization) of its coefficients. An application of the TVCNF for the enhancement of an arbitrary signal corrupted by a strong FM interference is investigated. It is shown that if the synchronization is based on the input mixture, then for any negative signal-to-interference ratio (SIR&amp;Lt;0 dB) at the input of the TVCNF, the SIR at its output reaches 0 dB
Research Interests:
ABSTRACT The concept of time-varying filters as applied to the problem of rejection of a sine signal with fast variations of frequency is explored. Using such filters, a method for synchronous (i.e., when frequency is known) estimation of... more
ABSTRACT The concept of time-varying filters as applied to the problem of rejection of a sine signal with fast variations of frequency is explored. Using such filters, a method for synchronous (i.e., when frequency is known) estimation of phase and amplitude of a sine wave corrupted by closely spaced sinusoidal interference with fast frequency variations is proposed. It is shown that the coefficients of the time-varying filter can be effectively determined using a Phase Locked Loop. It is proved that the performance of the proposed estimator depends neither on the interference level nor on the speed of frequency variations. Comparison with an adaptive estimator based on a linear time invariant filter shows the superiority of the proposed one where the interference frequency changes rapidly over time.ZusammenfassungDas Konzept der Anwendung zeitvarianter Filter zur Unterdrückung eines Sinnusignals schnell veränderlicher Frequenz wird erforscht. Auf der Grundlage solcher Filter wird ein Verfahren vorgeschlagen, mit der die Phase und die Amplitude eines Sinussignals synchron (d.h., bei bekannter Frequenz) geschätzt werden können, das durch dicht benachbarte Sinuskomponenten schnell variierender Frequenzen gestört ist. Es wird gezeigt, daß die Koeffizienten des zeitveränderlichen Filters mit Hilfe einer Phase-Locked-Loop effizient bestimmt werden können. Es wird nachgewiesen, daß die Leistungsfähigkeit des vorgeschlagenen Schätzers weder vom Störpegel noch von der Geschwindigkeit der Frequenzänderungen abhängt. Der Vergeich mit einem adaptiven Schätzer auf der Basis eines linearen zeitinvarianten Filters zeigt, daß der neue Vorschlag im Falle schneller Frequenzänderungen des Störsignals überlegen ist.RésuméLe concept de filters variant dans le temps, comme dans le problème de rejection d&#39;un signal sinusoïdal de fréquence à variation rapide, est exploré. En utilisant de tels filters, une méthode est proposée pour l&#39;estimation synchrone (c&#39;est-à-dire, quand la fréquence est connue) de la phase et de l&#39;amplitude d&#39;une onde sinusoïdale perturbée par une interférence sinusoïdale proche et à forte variation de fréquence. Il est montré que les coefficients du filtre variant dans le temps peuvent être déterminés en utilisant un boucle à asservissement de phase. Il est prouvé que les performances de l&#39;estimateur proposé ne dépendent ni du niveau d&#39;interférence ni de la vitesse de variation de la fréquence. La comparaison avec un estimateur adaptatif basé sur un filtre linéaire invariant dans le temps montre la supériorité de celui qui est proposé dans lequel la fréquence de l&#39;interférence change rapidement dans le temps.
Research Interests:
This paper investigates the achievable rate of multicarrier systems with non-linear distortion caused by high power amplifier (HPA) at the transmitter. We derive mutual information expressions for several non-linear models of HPA.... more
This paper investigates the achievable rate of multicarrier systems with non-linear distortion caused by high power amplifier (HPA) at the transmitter. We derive mutual information expressions for several non-linear models of HPA. Specific results are given for different values of the input backoff. It is shown that for some cases, linearization of HPA is not the best strategy.
Research Interests:
Link adaptation is a crucial part of many modern communications systems, allowing the system to adapt the transmission and reception strategies to changes in channel conditions. One of the fundamental components of the link adaptation... more
Link adaptation is a crucial part of many modern communications systems, allowing the system to adapt the transmission and reception strategies to changes in channel conditions. One of the fundamental components of the link adaptation mechanism is signal to noise ratio (SNR) estimation, measuring the instantaneous (mostly post processing) SNR at the receiver. That is, the SNR at the decoder
Research Interests:
ABSTRACT In this work we present a serial concatenation of differential encoder 8-PSK with Reed Solomon (RS) code and iterative decoding to get the maximum performance from this combination. The differential encoding is often used in... more
ABSTRACT In this work we present a serial concatenation of differential encoder 8-PSK with Reed Solomon (RS) code and iterative decoding to get the maximum performance from this combination. The differential encoding is often used in conjunction with noncoherent demodulation to overcome carrier phase synchronization problems in communication systems employing M-ary phase shift keying (MPSK), in spite of the degradation in performance relative to coherent systems. In this work, we show that when differential encoding is combined with RS encoding and interleaving, this degradation is reduced due to the iterative decoding. We also present a soft input soft output (SISO) decoder for RS codes based on the Chase algorithms for binary block codes. The receiver in the simulations, is a serial concatenation of maximum a posteriori probability (MAP) demodulator, de-interleaver and the new RS SISO decoder.
Research Interests:
... and Computer Engineering Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel 1 linnadav@walla.com 2 ilan.shallom@audiocodes.com 3 dov@ee.bgu.ac.il ... Several are classified as coder dependent, in which the algorithm makes... more
... and Computer Engineering Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel 1 linnadav@walla.com 2 ilan.shallom@audiocodes.com 3 dov@ee.bgu.ac.il ... Several are classified as coder dependent, in which the algorithm makes use of coder specific information. ...
Research Interests:
... Acknowledgements We would like to thank Dr. I. Kalet for his help. References [1] I. Kalet and S. Shamai (Shitz), "On the capacity of a twistedwire pair: Gaussian model", IEEE Trans. Comm., Vol. 38, No. 3, March 1990, pp.... more
... Acknowledgements We would like to thank Dr. I. Kalet for his help. References [1] I. Kalet and S. Shamai (Shitz), "On the capacity of a twistedwire pair: Gaussian model", IEEE Trans. Comm., Vol. 38, No. 3, March 1990, pp. ... Comm., Vol. 38, No. 3, March 1990, pp. 368378. ...
Research Interests:
... Signal Processing 13 (1987) 301-308 301 North-Holland MODE DETECTOR OF SSB RADIODov WULICH and David YARDENI Department of Electrical and Computer ... [6] i. Reiner, Introduction to Matrix Theory and Linear Algebra, Holt, Rinehart... more
... Signal Processing 13 (1987) 301-308 301 North-Holland MODE DETECTOR OF SSB RADIODov WULICH and David YARDENI Department of Electrical and Computer ... [6] i. Reiner, Introduction to Matrix Theory and Linear Algebra, Holt, Rinehart &amp; Winston, New York, 1971. ...
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
Multiple input multiple output (MIMO) precoding is an efficient scheme that may significantly enhance the communication link. Many precoding schemes require channel knowledge at the transmitter that is obtained, in non-reciprocal... more
Multiple input multiple output (MIMO) precoding is an efficient scheme that may significantly enhance the communication link. Many precoding schemes require channel knowledge at the transmitter that is obtained, in non-reciprocal channels, through feedback from the receiver to the transmitter. Focusing on the natural fusion of orthogonal frequency division multiplexing (OFDM) and MIMO, we exploit the channel correlation in the frequency domain to reduce the required feedback data rate. The proposed feedback method tailors Huffman coding to an existing clustering method, and is employed here for the transmit beamforming. The method leads to a significant reduction in the required feedback data rate, and performs better than existing feedback techniques. The proposed method can be easily implemented in any existing or future protocol due to its low complexity.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT We present results of simulation of a low-bit rate speech transmission system in a channel with common Rayleigh fading. The system uses code-excited linear voice prediction (CELP) and the channel errors correction. The quality of... more
ABSTRACT We present results of simulation of a low-bit rate speech transmission system in a channel with common Rayleigh fading. The system uses code-excited linear voice prediction (CELP) and the channel errors correction. The quality of the speech restoration provided by the system is estimated with the help of two tests. The first one is the well known intelligibility diagnostic rhyme test (DRT) and the second one is the mean opinion score (MOS). The system considered appears to be rather robust i.e., demonstrates high noise and fading immunity and provides good speech quality for the bit-rate 4.8 kb/s in channels with the bit-error rate not exceeding 10-2
Research Interests:
Research Interests:
This paper deals with a Maximum Likelihood receiver for a nonlinearly distorted OFDM signal over a flat channel with AWGN. The nonlinearity destroys the orthogonality between subcarriers, consequently, a per subcarrier decision, used when... more
This paper deals with a Maximum Likelihood receiver for a nonlinearly distorted OFDM signal over a flat channel with AWGN. The nonlinearity destroys the orthogonality between subcarriers, consequently, a per subcarrier decision, used when the linear PA is considered, is no longer optimal. We propose a sub-optimal receiver based on the Maximum Likelihood (ML) criterion. The ML receiver has to find the minimum Euclidean distance between the received vector and a set of all possible OFDM symbols passed through the same nonlinearity. This approach has exponential complexity. To reduce the complexity, we propose a sub-optimal receiver that minimizes the Euclidean distance, seen as a cost function, by the gradient descent algorithm. Unfortunately, due to the nonlinearity, the cost function is non-convex. In order to overcome this obstacle, we propose a method to classify the solution, i.e., to decide if the achieved minimum is local or global. We modify the gradient descent algorithm to avoid convergence to a local minimum. It is shown that the proposed receiver outperforms the simple OFDM and iterative receivers in terms of symbol error rate (SER) performance.