Raghavan Subramaniyan - Academia.edu (original) (raw)

Uploads

Papers by Raghavan Subramaniyan

Journal of the Acoustical Society of America, May 1, 1995

The direction of arrival (DOA) estimation problem in the presence of signal and noise coupling in... more The direction of arrival (DOA) estimation problem in the presence of signal and noise coupling in antenna arrays is addressed. In many applications, such as smart antenna, radar and navigation systems, the noise coupling between different antenna array elements is often neglected in the antenna modeling and thus, may significantly degrade the system performance. Utilizing the exact noise covariance matrix enables to achieve highperformance source localization by taking into account the colored properties of the array noise. The noise covariance matrix of the antenna array consists of both the external noise sources from sky, ground and interference, and the internal noise sources from amplifiers and loads. Computation of the internal noise covariance matrix is implemented using the theory of noisy linear networks combined with the method of moments (MoM). Based on this noise statistical analysis, a new four-port antenna element consisting of two orthogonal loops is proposed with enhanced source localization performance. The maximum likelihood (ML) estimator and the Cramer-Rao lower bound (CRLB) for DOA estimation in the presence of noise coupling is derived. Simulation results show that the noise coupling in antenna arrays may substantially alter the source localization performance. The performance of a mismatched ML estimator based on a model which ignores the noise coupling shows significant performance degradation due to noise coupling. These results demonstrate the importance of the noise coupling modeling in the DOA estimation algorithms.

Journal of Electronics (China), 2012

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

L'invention vise a identifier (302) des pixels dans une image fournie pour lesquels le conten... more L'invention vise a identifier (302) des pixels dans une image fournie pour lesquels le contenu a ete fourni (301) de maniere erronee. Le contenu d'image est traite (303) pour produire une version de l'image dans laquelle l'erreur est au moins partiellement cachee, et produire (304) aussi des donnees auxiliaires relatives au(x) pixel(s) errone(s) et a l'emplacement spatial auquel ce(s) pixel(s) correspond(ent), afin de produire un enregistrement qui decrit quels pixels du contenu d'image a ete fourni de maniere erronee. Une option (305) facultative pouvant etre selectionnee par l'utilisateur permet d'afficher la version corrigee de l'image mentionnee precedemment dans laquelle l'erreur est au moins partiellement cachee, et une version de l'image dans laquelle les donnees auxiliaires sont utilisees pour decrire le(s) pixel(s) errone(s) afin d'identifier aisement les pixels fournis de maniere erronee de ceux fournis correctement.

L'invention concerne un procede et un appareil permettant de determiner la qualite de la coin... more L'invention concerne un procede et un appareil permettant de determiner la qualite de la coincidence d'un bloc pour un vecteur de mouvement candidat dans un systeme codeur video utilisant des vecteurs de mouvement representant la difference en termes de coordonnees d'un macrobloc de donnees dans une trame courante de donnees video et de coordonnees d'un macrobloc relatif de donnees dans une trame de reference de donnees video. Le procede consiste a definir un modele de recherche, a rechercher une region d'apres le modele de recherche pour un vecteur de mouvement candidat en vue de l'evaluation, a calculer une difference metrique, a calculer une polarisation d'apres la difference entre un vecteur de mouvement de prediction et un vecteur de mouvement candidat, a determiner une difference metrique modifiee par l'ajout de la difference metrique a la polarisation et a definir un vecteur de mouvement final d'apres la difference metrique modifiee.

Cette invention concerne des ensembles fils-guides multifonctionnels et un systeme pour analyser ... more Cette invention concerne des ensembles fils-guides multifonctionnels et un systeme pour analyser des parametres anatomiques et fonctionnels. Selon l'invention, un seul fil-guide permet d'effectuer des mesures fonctionnelles et anatomiques et d'identifier des lesions. Les mesures fonctionnelles telles que la pression peuvent etre obtenues a l'aide d'un capteur de pression sur le fil-guide tandis que les mesures anatomiques telles que les dimensions des lumieres peuvent etre obtenues par utilisation d'une electrode. Le reseau vasculaire et les lesions stenosees peuvent etre modelises sous la forme d'un reseau electrique equivalent et resolus en fonction des parametres mesures. Plusieurs options de plan de traitement peuvent etre elaborees, chaque plan pouvant correspondre au traitement d'un sous-ensemble de lesions particulieres. La solution anatomique pour chacun des plans de traitement peut etre estimee et les parametres electriques modifies equivalen...

一种降低视频编码器系统中计算复杂性的方法和设备。 该方法包括接收变换的视频块数据系数；设定阈值；确定是否至少一个变换的视频块数据系数的量值大于该阈值；如果至少一个变换视频块数据系数的量值大于该阈... more 一种降低视频编码器系统中计算复杂性的方法和设备。 该方法包括接收变换的视频块数据系数；设定阈值；确定是否至少一个变换的视频块数据系数的量值大于该阈值；如果至少一个变换视频块数据系数的量值大于该阈值则执行随后的压缩功能；并且如果没有变换视频块数据系数的量值大于该阈值，则绕过随后的压缩功能。

H.264 is the latest video compression technology offering up to 50% bit rate savings compared to ... more H.264 is the latest video compression technology offering up to 50% bit rate savings compared to previous technologies like MPEG-2 and MPEG-4. However, the improved compression comes at the cost of increased computational complexity. H.264 decoding is about 2 to 3 times more complex than MPEG-4 decoder. This poses a challenge for real time implementation for embedded applications. To implement a high resolution (e.g. VGA) H.264 decoder on a low power embedded platform, DSP's or SIMD accelerated processors face several challenges. They either can't meet the demand of processing power (e.g. ARM-like RISC processors) or require high power and chip area (multi-core DSP). An embedded platform of ARM host with a vector co-processor promises to give a very good cost-performance tradeoff. We have developed an optimized H.264 decoder on a vector processor by some efficient methods to improve the performance. Our simulation shows that it is possible to decode VGA H.264 bitstreams at 1...

Motion Compensation for video decoding in standards like MPEG and H.264 typically take more than ... more Motion Compensation for video decoding in standards like MPEG and H.264 typically take more than 50% of the computational time, a new technique is proposed to speed up this process for low motion video sequence. This technique can be primarily employed for systems which have vector processors as video decode accelerators. The typical gain using this technique on an ideal vector processor can be more than 50% for a low motion video sequence. An ideal vector processor satisfies the below equation.

Journal of the Acoustical Society of America, May 1, 1995

The direction of arrival (DOA) estimation problem in the presence of signal and noise coupling in... more The direction of arrival (DOA) estimation problem in the presence of signal and noise coupling in antenna arrays is addressed. In many applications, such as smart antenna, radar and navigation systems, the noise coupling between different antenna array elements is often neglected in the antenna modeling and thus, may significantly degrade the system performance. Utilizing the exact noise covariance matrix enables to achieve highperformance source localization by taking into account the colored properties of the array noise. The noise covariance matrix of the antenna array consists of both the external noise sources from sky, ground and interference, and the internal noise sources from amplifiers and loads. Computation of the internal noise covariance matrix is implemented using the theory of noisy linear networks combined with the method of moments (MoM). Based on this noise statistical analysis, a new four-port antenna element consisting of two orthogonal loops is proposed with enhanced source localization performance. The maximum likelihood (ML) estimator and the Cramer-Rao lower bound (CRLB) for DOA estimation in the presence of noise coupling is derived. Simulation results show that the noise coupling in antenna arrays may substantially alter the source localization performance. The performance of a mismatched ML estimator based on a model which ignores the noise coupling shows significant performance degradation due to noise coupling. These results demonstrate the importance of the noise coupling modeling in the DOA estimation algorithms.

Journal of Electronics (China), 2012

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

L'invention vise a identifier (302) des pixels dans une image fournie pour lesquels le conten... more L'invention vise a identifier (302) des pixels dans une image fournie pour lesquels le contenu a ete fourni (301) de maniere erronee. Le contenu d'image est traite (303) pour produire une version de l'image dans laquelle l'erreur est au moins partiellement cachee, et produire (304) aussi des donnees auxiliaires relatives au(x) pixel(s) errone(s) et a l'emplacement spatial auquel ce(s) pixel(s) correspond(ent), afin de produire un enregistrement qui decrit quels pixels du contenu d'image a ete fourni de maniere erronee. Une option (305) facultative pouvant etre selectionnee par l'utilisateur permet d'afficher la version corrigee de l'image mentionnee precedemment dans laquelle l'erreur est au moins partiellement cachee, et une version de l'image dans laquelle les donnees auxiliaires sont utilisees pour decrire le(s) pixel(s) errone(s) afin d'identifier aisement les pixels fournis de maniere erronee de ceux fournis correctement.

L'invention concerne un procede et un appareil permettant de determiner la qualite de la coin... more L'invention concerne un procede et un appareil permettant de determiner la qualite de la coincidence d'un bloc pour un vecteur de mouvement candidat dans un systeme codeur video utilisant des vecteurs de mouvement representant la difference en termes de coordonnees d'un macrobloc de donnees dans une trame courante de donnees video et de coordonnees d'un macrobloc relatif de donnees dans une trame de reference de donnees video. Le procede consiste a definir un modele de recherche, a rechercher une region d'apres le modele de recherche pour un vecteur de mouvement candidat en vue de l'evaluation, a calculer une difference metrique, a calculer une polarisation d'apres la difference entre un vecteur de mouvement de prediction et un vecteur de mouvement candidat, a determiner une difference metrique modifiee par l'ajout de la difference metrique a la polarisation et a definir un vecteur de mouvement final d'apres la difference metrique modifiee.

Cette invention concerne des ensembles fils-guides multifonctionnels et un systeme pour analyser ... more Cette invention concerne des ensembles fils-guides multifonctionnels et un systeme pour analyser des parametres anatomiques et fonctionnels. Selon l'invention, un seul fil-guide permet d'effectuer des mesures fonctionnelles et anatomiques et d'identifier des lesions. Les mesures fonctionnelles telles que la pression peuvent etre obtenues a l'aide d'un capteur de pression sur le fil-guide tandis que les mesures anatomiques telles que les dimensions des lumieres peuvent etre obtenues par utilisation d'une electrode. Le reseau vasculaire et les lesions stenosees peuvent etre modelises sous la forme d'un reseau electrique equivalent et resolus en fonction des parametres mesures. Plusieurs options de plan de traitement peuvent etre elaborees, chaque plan pouvant correspondre au traitement d'un sous-ensemble de lesions particulieres. La solution anatomique pour chacun des plans de traitement peut etre estimee et les parametres electriques modifies equivalen...

一种降低视频编码器系统中计算复杂性的方法和设备。 该方法包括接收变换的视频块数据系数；设定阈值；确定是否至少一个变换的视频块数据系数的量值大于该阈值；如果至少一个变换视频块数据系数的量值大于该阈... more 一种降低视频编码器系统中计算复杂性的方法和设备。 该方法包括接收变换的视频块数据系数；设定阈值；确定是否至少一个变换的视频块数据系数的量值大于该阈值；如果至少一个变换视频块数据系数的量值大于该阈值则执行随后的压缩功能；并且如果没有变换视频块数据系数的量值大于该阈值，则绕过随后的压缩功能。

H.264 is the latest video compression technology offering up to 50% bit rate savings compared to ... more H.264 is the latest video compression technology offering up to 50% bit rate savings compared to previous technologies like MPEG-2 and MPEG-4. However, the improved compression comes at the cost of increased computational complexity. H.264 decoding is about 2 to 3 times more complex than MPEG-4 decoder. This poses a challenge for real time implementation for embedded applications. To implement a high resolution (e.g. VGA) H.264 decoder on a low power embedded platform, DSP's or SIMD accelerated processors face several challenges. They either can't meet the demand of processing power (e.g. ARM-like RISC processors) or require high power and chip area (multi-core DSP). An embedded platform of ARM host with a vector co-processor promises to give a very good cost-performance tradeoff. We have developed an optimized H.264 decoder on a vector processor by some efficient methods to improve the performance. Our simulation shows that it is possible to decode VGA H.264 bitstreams at 1...

Motion Compensation for video decoding in standards like MPEG and H.264 typically take more than ... more Motion Compensation for video decoding in standards like MPEG and H.264 typically take more than 50% of the computational time, a new technique is proposed to speed up this process for low motion video sequence. This technique can be primarily employed for systems which have vector processors as video decode accelerators. The typical gain using this technique on an ideal vector processor can be more than 50% for a low motion video sequence. An ideal vector processor satisfies the below equation.