Showing papers by "Dinesh Rajan published in 2006"

Adaptive flat multiresolution multiplexed computational imaging architecture utilizing micromirror arrays to steer subimager fields of view

Abstract: A thin, agile multiresolution, computational imaging sensor architecture, termed PANOPTES (processing arrays of Nyguist-limited observations to produce a thin electro-optic sensor), which utilizes arrays of microelectromechanical mirrors to adaptively redirect the fields of view of multiple low-resolution subimagers, is described. An information theory-based algorithm adapts the system and restores the image. The modulation transfer function (MTF) effects of utilizing micromirror arrays to steering imaging systems are analyzed, and computational methods for combining data collected from systems with differing MTFs are presented.

Joint feed-forward and feedback design for wireless communication systems

Abstract: A first method comprises determining a condition of a buffer in a transmitter; using the condition, determining information corresponding to the condition; and communicating the information to a receiver. A second method is disclosed comprising receiving first information corresponding to a condition of a buffer in a transmitter; determining channel state information for a channel from the transmitter to the receiver; using the first information and the determined channel state information, determining second information; and communicating the second information to the transmitter. The second information and the condition of the buffer may be used by the transmitter to determine at least one transmission parameter, e.g., one or both of transmission rate and transmission power for a signal from the transmitter to the receiver. A desired delay constraint for packet traffic over the channel may be achieved.

Benefits of optical system diversity for multiplexed image reconstruction

Abstract: Algorithms that use optical system diversity to improve multiplexed image reconstruction from multiple low-resolution images are analyzed and demonstrated. Compared with systems using identical imagers, systems using additional lower-resolution imagers can have improved accuracy and computation. The diverse system is not sensitive to boundary conditions and can take full advantage of improvements that decrease noise and allow an increased number of bits per pixel to represent spatial information in a scene.

Improved Multiplexed Image Reconstruction Performance Through Optical System Diversity Design

Abstract: Multiplexed image reconstruction, estimating high resolution images from multiple low resolution images with highly overlapped fields of view, is improved when the magnification of the imagers is diverse. No assumptions of shift invariance or Toeplitz structure are required for computational manageability because localized reconstruction is possible and sensitivity to boundary conditions is reduced. Such multiplexed diverse image sensors have applications in flat sensor systems for surveillance and pervasive personal imaging.

Hybrid routing with periodic updates (HRPU) in wireless mesh networks

Abstract: This paper proposes HRPU, a hybrid routing algorithm for wireless mesh networks. In HRPU, the mesh portal periodically broadcasts a mesh update message, which allows all nodes to have a route towards the mesh portal stored semi-permanently in their routing table. Whenever a node has data to be sent to backbone network, it sends the data without any route establishment delay using the route to the mesh portal. Numerical results show the higher throughput and lower overhead of proposed HRPU. In HRPU the mesh portals and mesh points adapt some critical parameters to further improve performance

Edge Detection Performance in Super-Resolution Image Reconstruction from Camera Arrays

Abstract: Previous work has shown that for super-resolution image reconstruction from low resolution images, image acquisition with a diverse optical system improves reconstructed image quality as measured by the expected and actual mean squared error. However, other measures of image fidelity should also be considered. An alternative performance measure might be based on edge errors, since edges are often the first step in more complex image analysis for both image processing systems and biological systems. This paper explores the behavior of edge errors and intensity errors for super-resolution image reconstruction applications in which ill-posed inversions may cause the actual mean squared error to be highly dependent of image content and thus poorly predicted by the expected mean squared error.

CTH11-1: Queuing Aspects of Multiantenna Multiple Access Channels

Abstract: In this communication, we investigate the effect of spatial dimension in a Gaussian multiple access system and study its impact on the physical layer capacity and the end to end delay from a queueing theory perspective. For a multiple-input, single-output (MISO) multiple access channel, we derive conditions on the transmit power and number of transmit antennas for which additional users increase or decrease the capacity. The capacity as a function of the number of users is used for calculating the end-to-end delay. Numerical analysis on the end-to-end delay for a Rayleigh fading MISO channel with no channel state information at transmitter (CSIT) indicates that increasing the number of transmit antennas can actually increase the delay.

Queuing aspects of multiantenna multiple access channels

Abstract: In this communication, we investigate the effect of spatial dimension in a Gaussian multiple access system and study its impact on the physical layer capacity and the end to end delay from a queueing theory perspective. For a multiple-input, single- output (MISO) multiple access channel, we derive conditions on the transmit power and number of transmit antennas for which additional users increase or decrease the capacity. The capacity as a function of the number of users is used for calculating the end- to-end delay. Numerical analysis on the end-to-end delay for a Rayleigh fading MISO channel with no channel state information at transmitter (CSIT) indicates that increasing the number of transmit antennas can actually increase the delay! Index terms- MIMO, MAC, Queueing theory I. INTRODUCTION

Super-Resolution Image Reconstruction for Diverse Sub-Imager Arrays

Abstract: High resolution images can be estimated using multiple low resolution images obtained from an array of sub- imagers with overlapping fields of view Design choices for the optics and sensors of a flat camera can have a significant impact on the performance of reconstruction algorithms This paper will analyze designs that provide diversity which reduces the expected error of reconstruction algorithms It will be assumed that the fields of view of individual sub-imagers can be controlled so that the desired resolution improvement at the object distance of interest can be achieved Simulations will demonstrate the analytical results

Improvedmultiplexedimage reconstructionperformance through opticalsystemdiversitydesign

Abstract: Multiplexed imagereconstruction, estimating highresolution imagesfrommultiple lowresolution images withhighly overlapped fields ofview, isimproved whenthemagnification oftheimagers isdiverse. Noassumptions ofshift invariance orToeplitz structure arerequired forcomputational manageability because localized reconstruction ispossible andsensitivity toboundary conditions isreduced. Suchmultiplexed diverse imagesensors haveapplications in flat sensor systems forsurveillance andpervasive personal imaging. Index Terms-Multiplexed imagers, imagereconstruction, computational imaging, flat camera.