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Abbas El Gamal

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Papers by Abbas El Gamal

<title>Folded multiple-capture: an architecture for high dynamic range disturbance-tolerant focal plane array</title>

Infrared Technology and Applications XXX, 2004

Earlier studies have shown that multiple capture can achieve high SNR, but cannot satisfy the hig... more Earlier studies have shown that multiple capture can achieve high SNR, but cannot satisfy the high dynamic range (HDR) and high speed requirements of the Vertically-Integrated-Sensor-Array (VISA) project. Synchronous selfreset, on the other hand, can achieve these requirements, but suffers from poor SNR. Extended counting can achieve high dynamic range at high frame rate and with good SNR, but at the expense of high power consumption. The paper proposes a new HDR focal plane array architecture, denoted by folded-multiple capture (FMC), which by combining features of the synchronous self-reset and multiple capture schemes, can satisfy the VISA requirements at a fraction of the power dissipation and with more robustness to device variations than extended counting. The architecture is also capable of detecting subframe disturbances, e.g., due to laser jamming, and correcting for it.

<title>Characterization of CMOS image sensors with Nyquist rate pixel-level ADC</title>

Sensors, Cameras, and Applications for Digital Photography, 1999

Techniques for characterizing CCD imagers have been developed over many years. These techniques h... more Techniques for characterizing CCD imagers have been developed over many years. These techniques have been recently modified and extended to CMOS PPS and APS imagers. With the scaling of CMOS technology, an increasing number of transistors can be added to each pixel. A promising direction to utilize these transistors is to perform pixel level ADC. The authors have designed and protoyped two imagers with pixel level Nyquist rate ADC. The ADCs operate in parallel and output data one bit at a time. The data is read out of the imager array one bit plane at a time in a manner similar to a digital memory. Existing characterization techniques could not be directly used for these imagers, however, since there is no facility to read out the analog pixel values before ADC, and the ADC resolution is limited to only 8 bits. Fortunately. the ADCs are fully testable electrically without the need for any light or optics. This makes it possible to obtain the ADC transfer curve, which greatly simplifies characterization. In this paper we describe how we characterize our pixel level ADC imagers. To estimate QE, we measure the imager photon to DN transfer curve and the the ADC transfer curve. We find that both curves are quite linear. Using an estimate of the sense node capacitance we then estimate sensitivity, and QE. To estimate FPN we model it as an outcome of the sum of two uncorrelated random processes, one representing the ADC FPN, and the other representing the photodetector FPN, and develop estimators for the model parameters form imager data under uniform illumination. We report characterization results for a 640×512 imager, which was fabricated in a 0.35µm standard digital CMOS process.

Capacity region of the broadcast channel with two deterministic channel state components

2014 IEEE International Symposium on Information Theory, 2014

This paper establishes the capacity region of a class of broadcast channels with random state in ... more This paper establishes the capacity region of a class of broadcast channels with random state in which each channel component is selected from two possible functions and each receiver knows its state sequence. This channel model does not fit into any class of broadcast channels for which the capacity region was previously known and is useful in studying wireless communication channels when the fading state is known only at the receivers. The capacity region is shown to coincide with the UV outer bound and is achieved via Marton coding.

format_quoteThis channel model challenges previous broadcast channel capacities, indicating limited knowledge in the random state capacity realm.format_quote

Architectures for High Dynamic Range, High Speed Image Sensor Readout Circuits

2006 IFIP International Conference on Very Large Scale Integration, 2006

The stringent performance requirements of many infrared imaging applications warrant the developm... more The stringent performance requirements of many infrared imaging applications warrant the development of precision high dynamic range, high speed focal plane arrays. In addition to achieving high dynamic range, the readout circuits for these image sensors must achieve high linearity and SNR at low power consumption. We first review two high dynamic range image sensor schemes that have been developed for visible range imaging and discuss why they cannot meet the stringent performance demands of infrared imaging. We then describe a new dynamic range extension scheme, Folded Multiple Capture, that can meet these performance requirements. Dynamic range is extended using synchronous self-reset while high SNR is maintained using few non-uniformly spaced captures and leastsquares fit to estimate pixel photocurrent. We conclude with a description of a prototype of this architecture targeted for 3D-IC IR focal plane arrays.

format_quoteAchieving NETD of 10mK in IR imaging requires detection of femtoamp photocurrents, emphasizing high sensitivity needs.format_quote

Optimal Placement and Selection of Camera Network Nodes for Target Localization

Lecture Notes in Computer Science, 2006

The paper studies the optimal placement of multiple cameras and the selection of the best subset ... more The paper studies the optimal placement of multiple cameras and the selection of the best subset of cameras for single target localization in the framework of sensor networks. The cameras are assumed to be aimed horizontally around a room. To conserve both computation and communication energy, each camera reduces its image to a binary "scan-line" by performing simple background subtraction followed by vertical summing and thresholding, and communicates only the center of the detected foreground object. Assuming noisy camera measurements and an object prior, the minimum mean squared error of the best linear estimate of the object location in 2-D is used as a metric for placement and selection. The placement problem is shown to be equivalent to a classical inverse kinematics robotics problem, which can be solved efficiently using gradient descent techniques. The selection problem on the other hand is a combinatorial optimization problem and finding the optimal solution can be too costly to implement in an energy-constrained wireless camera network. A semi-definite programming approximation for the problem is shown to achieve close to optimal solutions with much lower computational burden. Simulation and experimental results are presented.

A 0.5 μm pixel frame-transfer CCD image sensor in 110 nm CMOS

2007 IEEE International Electron Devices Meeting, 2007

Cascade multiterminal source coding

2009 IEEE International Symposium on Information Theory, 2009

We investigate distributed source coding of two correlated sources X and Y where messages are pas... more We investigate distributed source coding of two correlated sources X and Y where messages are passed to a decoder in a cascade fashion. The encoder of X sends a message at rate R1 to the encoder of Y . The encoder of Y then sends a message to the decoder at rate R2 based both on Y and on the message it received about X. The decoder's task is to estimate a function of X and Y . For example, we consider the minimum mean squared-error distortion when encoding the sum of jointly Gaussian random variables under these constraints. We also characterize the rates needed to reconstruct a function of X and Y losslessly. Our general contribution toward understanding the limits of the cascade multiterminal source coding network is in the form of inner and outer bounds on the achievable rate region for satisfying a distortion constraint for an arbitrary distortion function d(x, y, z). The inner bound makes use of a balance between two encoding tactics-relaying the information about X and recompressing the information about X jointly with Y . In the Gaussian case, a threshold is discovered for identifying which of the two extreme strategies optimizes the inner bound. Relaying outperforms recompressing the sum at the relay for some rate pairs if the variance of X is greater than the variance of Y .

format_quoteA threshold exists where relaying outperforms recompressing the sum for certain X and Y variances.format_quote

Placement and routing for a field programmable multi-chip module

Proceedings of the 31st annual conference on Design automation conference - DAC '94, 1994

Placemen t and routing heuristics for a Field Programmable Multi-Chip Module (FPMCM) are presente... more Placemen t and routing heuristics for a Field Programmable Multi-Chip Module (FPMCM) are presented. The placement is done in three phases; partitioning, chip assignment and iterative improvement. The routing is done in two phases; global routing followed by detailed routing. Detailed routing involves new channel routing problems denoted by Exact Segmented Channel Routing (ESCR) and K-ESCR. A very fast K-ESCR heuristic is described. Experimental results show that the placement heuristic achieves high gate utilization, and that the K-ESCR heuristic performs surprisingly well over wide range of channel sizes.

Reliable Communication of Highly Distributed Information

Open Problems in Communication and Computation, 1987

Shannon’s theory of information [1] and subsequent generalizations to multiple users (for a surve... more Shannon’s theory of information [1] and subsequent generalizations to multiple users (for a survey see [2]) consider the situation of a small number of users each with an unlimited amount of information. The users communicate over a noisy channel with the goal of exchanging their information reliably. Here, we consider a complementary model. We assume a very large number of users, each with a small amount of information. We also assume that the communication takes place over a noisy channel but assume that the goal of the users is to compute a function reliably. This highly distributed information model is motivated by problems of decision making in a network. The users could be either a large number of processors, human beings, or simply the components of a logic circuit. In all cases, the noise is an inevitable physical limitation.

Experimental high speed CMOS image sensor system and applications

Proceedings of IEEE Sensors

CMOS image sensors are capable of very high-speed nondestructive readout, enabling many novel app... more CMOS image sensors are capable of very high-speed nondestructive readout, enabling many novel applications. To explore such applications, we designed and prototyped an experimental high speed imaging system based on a CMOS digital pixel sensor (DPS). The experimental system comprises a PCB that has the DPS chip interfaced to a PC via three I/O cards supported by an easy to use software environment. The system is capable of image acquisition at rates of up to 1,400 frames/sec. After describing the DPS chip and experimental imaging system,we present two applications: dynamic range extension and optical flow estimation. These applications rely on the DPS's ability to perform nondestructive readout of multiple frames at high-speed.

format_quoteImplemented single-ended charge-redistribution sense-amps for voltage coupling robustness in the DPS chip design.format_quote

<title>Quantitative study of high dynamic range Sigma-Delta-based focal plane array architectures</title>

Infrared Technology and Applications XXX, 2004

The paper investigates the suitability of Σ∆ modulation based FPA readout schemes for use in Vert... more The paper investigates the suitability of Σ∆ modulation based FPA readout schemes for use in Vertically Interconnected Sensor Arrays requiring ultra high dynamic range and frame rate. It is shown that the extended counting scheme is capable of achieving the DR and frame rate requirements but at the expense of high power consumption. Extended counting is also shown to outperform several other HDR schemes in terms of SNR at the ultra high DR and frame rate.

Source Description Cost

2006 IEEE International Symposium on Information Theory, 2006

The paper considers the source description problem with average distortion and per-symbol reprodu... more The paper considers the source description problem with average distortion and per-symbol reproduction cost constraints. The source description cost-distortion function is then defined as the minimum of a weighted sum of the rate and the expected per-symbol reproduction cost subject to average distortion constraint. This function is evaluated for (i) binary source, Hamming loss and reproduction cost of 0 for a 0 and 1 for 1, (ii) Gaussian source, squared error distortion, and average power constraint on reproduction, and (iii) Gaussian Wyner-Ziv source coding with side information setting and average power constraint on reproduction. The results are compared to the description cost in the classical case.

format_quoteSensor networks must compress data locally due to limited energy and throughput, necessitating effective source description strategies.format_quote

The capacity of a class of 3-receiver broadcast channels with degraded message sets

Computing Research Repository, 2007

Korner and Marton established the capacity region for the 2-receiver broadcast channel with degra... more Korner and Marton established the capacity region for the 2-receiver broadcast channel with degraded message sets. Recent results and conjectures suggest that a straightforward extension of the Korner-Marton region to more than 2 receivers is optimal. This paper shows that this is not the case. We establish the capacity region for a class of 3-receiver broadcast channels with 2 degraded

format_quoteThe capacity region for 3-receiver broadcast channels can exceed the straightforward Körner-Marton extension, validating the authors' novel findings.format_quote

Miniaturized integration of a fluorescence microscope

Nature Methods, 2011

the light microscope is traditionally an instrument of substantial size and expense. its miniatur... more the light microscope is traditionally an instrument of substantial size and expense. its miniaturized integration would enable many new applications based on mass-producible, tiny microscopes. Key prospective usages include brain imaging in behaving animals for relating cellular dynamics to animal behavior. here we introduce a miniature (1.9 g) integrated fluorescence microscope made from mass-producible parts, including a semiconductor light source and sensor. this device enables high-speed cellular imaging across ~0.5 mm 2 areas in active mice. this capability allowed concurrent tracking of ca 2+ spiking in >200 Purkinje neurons across nine cerebellar microzones. during mouse locomotion, individual microzones exhibited large-scale, synchronized ca 2+ spiking. this is a mesoscopic neural dynamic missed by prior techniques for studying the brain at other length scales. overall, the integrated microscope is a potentially transformative technology that permits distribution to many animals and enables diverse usages, such as portable diagnostics or microscope arrays for large-scale screens. Modern understanding of technology recognizes miniaturized integration as a pivotal advance that facilitates low-cost production and typically leads to improved performance and unanticipated applications 1 . Such impact has been shown in diverse arenas, including telecommunications, computing and genomics. One technology that has largely resisted integration is the light microscope, which generally remains a bulky and costly tabletop instrument. In neuroscience, microscopy has achieved widespread use in live animals, but the limitations of conventional microscopes hamper the scope and scale of brain-imaging experiments 2 . To improve the accessibility, quality and throughput of brain-imaging studies in freely behaving mice, we created a miniature, integrated fluorescence microscope with a design permitting mass-production and high-speed tracking of neural dynamics. The microscope is based on micro-optics and semiconductor optoelectronics, both readily mass-fabricated, and integrates all optical parts in a tiny package that is easily held by the fingertips. Compared to highresolution fiber-optic microscopes, our device offers advantages in optical sensitivity, field of view, attainable resolution, mechanical flexibility for the animal, cost and portability.

Noisy Network Coding

IEEE Transactions on Information Theory, 2011

A noisy network coding scheme for sending multiple sources over a general noisy network is presen... more A noisy network coding scheme for sending multiple sources over a general noisy network is presented. For multi-source multicast networks, the scheme naturally extends both network coding over noiseless networks by Ahlswede, Cai, Li, and Yeung, and compress-forward coding for the relay channel by Cover and El Gamal to general discrete memoryless and Gaussian networks. The scheme also recovers as special cases the results on coding for wireless relay networks and deterministic networks by Avestimehr, Diggavi, and Tse, and coding for wireless erasure networks by Dana, Gowaikar, Palanki, Hassibi, and Effros. The scheme involves message repetition coding, relay signal compression, and simultaneous decoding. Unlike previous compress-forward schemes, where independent messages are sent over multiple blocks, the same message is sent multiple times using independent codebooks as in the network coding scheme for cyclic networks. Furthermore, the relays do not use Wyner-Ziv binning as in previous compress-forward schemes, and each decoder performs simultaneous joint typicality decoding on the received signals from all the blocks without explicitly decoding the compression indices. A consequence of this new scheme is that achievability is proved simply and more generally without resorting to time expansion to extend results for acyclic networks to networks with cycles. The noisy network coding scheme is then extended to general multi-source networks by combining it with decoding techniques for interference channels. For the Gaussian multicast network, noisy network coding improves the previously established gap to the cutset bound. We also demonstrate through two popular AWGN network examples that noisy network coding can outperform conventional compress-forward, amplifyforward, and hash-forward coding schemes.

Capacity of a Class of Relay Channels With Orthogonal Components

IEEE Transactions on Information Theory, 2005

The capacity of a class of discrete-memoryless relay channels with orthogonal channels from the s... more The capacity of a class of discrete-memoryless relay channels with orthogonal channels from the sender to the relay receiver and from the sender and relay to the receiver is shown to be equal to the max-flow min-cut upper bound. The result is extended to additive white Gaussian noise (AWGN) relay channels where the channel from the sender to the relay uses a different frequency band from the channel from the sender and the relay to the receiver. Index Terms-Additive white Gaussian noise (AWGN) relay channel, discrete memoryless relay channel.

On Adaptive Transmission for Energy Efficiency in Wireless Data Networks

IEEE Transactions on Information Theory, 2004

This paper investigates the problem of energy-efficient transmission of data packets in a wireles... more This paper investigates the problem of energy-efficient transmission of data packets in a wireless network by jointly adapting to backlog and channel condition. Specifically, we consider minimum-energy scheduling problems over multiple-access channels, broadcast channels, and channels with fading, when packets of all users need to be transmitted before a deadline . Earlier work has considered a similar setup and demonstrated significant transmission energy saving by adapting to backlog for channels that are time invariant and when transmission is restricted to time-division. For concreteness, throughout the paper, rates and powers corresponding to optimal coding over discrete-time additive white Gaussian noise (AWGN) channels are assumed. The results, however, hold for more general channels and coding schemes where the total transmitted power is convex in the transmission rates. The offline scheduling problems for all the channels considered are shown to reduce to convex optimization problems with linear constraints. An iterative algorithm, referred to as FlowRight, that finds optimal offline schedules is presented. A heuristic online algorithm that we call look-ahead water-filling, which jointly adapts to both channel fading state and backlog is described. By the use of a small buffer which introduces an almost fixed delay, this algorithm achieves a considerable reduction in energy relative to water filling solely on channel states.

Optimal throughput-delay scaling in wireless networks - part I: the fluid model

IEEE Transactions on Information Theory, 2006

introduced a random model to study throughput scaling in a wireless network with static nodes, an... more introduced a random model to study throughput scaling in a wireless network with static nodes, and showed that the throughput per source-destination pair is Θ 1/ √ n log n . Grossglauser and Tse (2001) showed that when nodes are mobile it is possible to have a constant throughput scaling per source-destination pair. In most applications delay is also a key metric of network performance. It is expected that high throughput is achieved at the cost of high delay and that one can be improved at the cost of the other. The focus of this paper is on studying this trade-off for wireless networks in a general framework. Optimal throughput-delay scaling laws for static and mobile wireless networks are established. For static networks, it is shown that the optimal throughput-delay trade-off is given by D(n) = Θ(nT (n)), where T (n) and D(n) are the throughput and delay scaling, respectively. For mobile networks, a simple proof of the throughput scaling of Θ(1) for the Grossglauser-Tse scheme is given and the associated delay scaling is shown to be Θ(n log n). The optimal throughput-delay trade-off for mobile networks is also established. To capture physical movement in the real world, a random walk model for node mobility is assumed. It is shown that for throughput of O 1/ √ n log n , which can also be achieved in static networks, the throughput-delay trade-off is the same as in static networks, i.e., D(n) = Θ(nT (n)). Surprisingly, for almost any throughput of a higher order, the delay is shown to be Θ(n log n), which is the delay for throughput of Θ(1). Our result, thus, suggests that the use of mobility to increase throughput, even slightly, in real-world networks would necessitate an abrupt and very large increase in delay.

Optical flow estimation using temporally oversampled video

IEEE Transactions on Image Processing, 2005

Recent advances in imaging sensor technology make high frame rate video capture practical. As dem... more Recent advances in imaging sensor technology make high frame rate video capture practical. As demonstrated in previous work, this capability can be used to enhance the performance of many image and video processing applications. The idea is to use the high frame rate capability to temporally oversample the scene and thus to obtain more accurate information about scene motion and illumination. This information is then used to improve the performance of image and standard frame-rate video applications. The paper investigates the use of temporal oversampling to improve the accuracy of optical flow estimation (OFE). A method for obtaining high accuracy optical flow estimates at a conventional standard frame rate, e.g. 30 frames/s, by first capturing and processing a high frame rate version of the video is presented. The method uses the Lucas-Kanade algorithm to obtain optical flow estimates at a high frame rate, which are then accumulated and refined to estimate the optical flow at the desired standard frame rate. The method demonstrates significant improvements in optical flow estimation accuracy both on synthetically generated video sequences and on a real video sequence captured using an experimental highspeed imaging system. It is then shown that a key benefit of using temporal oversampling to estimate optical flow is the reduction in motion aliasing. Using sinusoidal input sequences, the reduction in motion aliasing is identified and the desired minimum sampling rate as a function of the velocity and spatial bandwidth of the scene is determined. Using both synthetic and real video sequences it is shown that temporal oversampling improves OFE accuracy by reducing motion aliasing not only for areas with large displacements but also for areas with small displacements and high spatial frequencies. The use of other OFE algorithms with temporally oversampled video is then discussed. In particular the Haussecker algorithm is extended to work with high frame rate sequences. This extension demonstrates yet another important benefit of temporal oversampling, which is improving OFE accuracy when brightness varies with time.

Min-cut replication in partitioned networks

IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, 1995

Abstruct-Logic replication has been shown empirically to reduce pin count and partition sue in pa... more