Ishfaq Ahmad

Ishfaq Ahmad
University of Texas at Arlington | UTA

About

213
Publications
12,384
Reads
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7,741
Citations
Citations since 2017
15 Research Items
1385 Citations
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2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250

Publications

Publications (213)
Article
Natural hazards and technical malfunctions often cause widespread outages of power networks that affect the communities and critical infrastructures. Microgrids with distributed generation and storage can help mitigate some of these devastating effects. However, not many communities and infrastructures have alternative power mechanisms. When needed...
Article
Human-robot interfaces encompass developing technologies that determine how a user interacts with robot systems. Touchless and nonverbal interfaces are a subset of these in which the user can interact with robots without the use of buttons, speech, or other physical methods. The two driving forces behind the development of these methods are the des...
Article
Falls are a major health concern among elderly populations. There is a critical need to develop automated systems for assessing a patient's fall risk although the methodologies for determining this risk vary in efficacy, accessibility, and comfort. With advancements in smart home technol-ogy, aging in place and accurate fall risk assessment are no...
Article
Full-text available
People with hearing and speaking disabilities face significant hurdles in communication. The knowledge of sign language can help mitigate these hurdles, but most people without disabilities, including relatives, friends, and care providers, cannot understand sign language. The availability of automated tools can allow people with disabilities and t...
Article
Full-text available
Video standards are crucial for exchanging video content, enabling a myriad of services and supporting a wide variety of devices ranging from personal devices to clouds and IoT. One of the core requirements in video standards is the rate control that regulates the bit allocation and picture quality. This paper presents an overview of rate control t...
Conference Paper
Extreme weather events cause widespread power outages that affect critical infrastructures and other communities alike. Microgrids donate or trade their surplus capacity that the grid can use to power up critical load and communities that do not have alternatives power arrangements. Service restoration based on energy donation during a crisis is a...
Article
The task-to-core scheduling problem for allocating tasks graphs using Dynamic Voltage and Frequency Scaling (DVFS) for achieving three objectives of performance, energy, and temperature (PET), poses algorithmic challenges as it involves conflicting goals and trade-offs. A myriad of static algorithms have been proposed for solving the problem. These...
Conference Paper
Overwhelming energy-related costs mar data center profits. In a smart grid, the price of electricity may change with real-time demand, geographic area, and time-of-use. Data centers with flexible request dispatch and resource allocation capabilities can cooperatively avail these price variations to reduce expenditures and maximize profit. In this p...
Article
In allocating parallel tasks to cores, most energy and thermal-aware scheduling techniques rely on Dynamic Voltage and Frequency Scaling (DVFS) to mark up and down core speeds for running the system under the desired constraints. While these techniques often meet the imposed system constraints, they are maladroit at identifying the best possible tr...
Article
Three-way joint optimization of performance (P), energy (E), and temperature (T) in scheduling parallel tasks to multiple cores poses a challenge that is staggering in its computational complexity. The goal of the PET optimized scheduling (PETOS) problem is to minimize three quantities: the completion time of a task graph, the total energy consumpt...
Conference Paper
Performance, energy and temperature (PET) are closely related and must be considered holistically while addressing the balance between them. Multi-objective evolutionary algorithms (MOEAs) for finding Pareto optimal solutions are highly effective in generating solutions for task-to-core scheduling and voltage selection on individual cores. A soluti...
Conference Paper
Multi-objective evolutionary algorithms (MOEAs) are effective techniques for solving the DVFS-enabled performance (P), energy (E), and temperature (T) optimized scheduling (PETOS) problem. There are several MOEA techniques proposed in the literature for general multi-objective optimization. For example, SPEA-II is efficient for solving the PETOS pr...
Conference Paper
Despite significant advancements in multicore processor technology for reducing the chip-level energy consumption, higher levels of power dissipation resulting in thermal implications and cooling costs remain as unsolved problems. Although several scheduling methods of controlling and managing the power dissipation and temperature exist, most schem...
Article
Enabled by high-speed networking in commercial, scientific, and government settings, the realm of high performance is burgeoning with greater amounts of computational and storage resources. Large-scale systems such as computational grids consume a significant amount of energy due to their massive sizes. The energy and cooling costs of such systems...
Article
Thermal-aware scheduling of parallel jobs is becoming an increasingly critical issue in software design for computing platforms ranging from embedded systems to large servers and entire data centers. In addition to the obvious implications of unrestricted temperature, such as thermal emergencies resulting in hardware failure, effective thermal mana...
Conference Paper
This paper addresses the joint optimization of performance, energy, and temperature, termed as PET - optimization. This multi-objective PET-optimization is achieved in scheduling DAGs on multi-core systems. Our technique is based on multi-objective evolutionary algorithm (MOEA) for finding Pareto optimal solutions using scheduling and voltage selec...
Conference Paper
This paper proposes energy-efficient scheduling algorithms for distributed heterogeneous grids. The conservation of energy consumption has a tirade of effects that improve system reliability, increases in the lifespan of the system, ideally with only a linear degradation in performance. With a few restrictions and proper modeling, we convert the En...
Conference Paper
Thermal management is highly crucial for efficient exploitation of the potentially enormous computational power offered by advanced multi-core processors. Higher temperatures can adversely affect these processors. Without any thermal constraint, a task graph may be scheduled to run on the cores at their maximum voltage. Very often, multiple factors...
Article
The problem of energy-constrained performance optimization (as opposed to performance-constrained energy optimization) for parallel applications has garnered considerable attention in the area of sustainable computing. This paper surveys algorithms developed for effectively minimizing the degradation in schedule length that results from reschedulin...
Article
Full-text available
Over the last two decades, we have witnessed a tremendous growth of sequenced genomic data. However, the algorithms and computational power required to expeditiously process, classify, and analyze genomic data has lagged considerably. In bioinformatics, one of the most challenging and computationally intensive processes, which may take up to weeks...
Article
Full-text available
Data object replication onto distributed servers can potentially alleviate bottlenecks, reduce network traffic, increase scalability, add robustness, and decrease user perceived access time. The decision of selecting data object and server pairs requires solving a constraint optimization problem that in general is NP-complete. In this paper, we abs...
Article
Full-text available
This paper presents a variant of simulated evolution technique for the static non-preemptive scheduling of parallel programs represented by directed acyclic graphs including inter-processor communication delays and contention onto a multiprocessor system with the dual objectives of reducing the total execution time and scaling with the number of pr...
Conference Paper
The expanding scale and density of data centers has made their power consumption an imperative issue. Data center energy management has become of unprecedented importance not only from an economic perspective but also for environment conservation. The recent surge in the popularity of cloud computing for providing rich multimedia services has furth...
Conference Paper
There is a lack of generally applicable methods for reducing energy consumption while ensuring good quality of service in distributed computational grids. We study the energy-aware task allocation problem for assigning a set of tasks onto the machines in a grid environment where the conflicting goals of ensuring quality of service and reducing ener...
Conference Paper
Given an initial schedule of a parallel program represented by a directed acyclic graph (DAG) and an energy constraint, the question arises how to effectively determine what nodes (tasks) can be penalized (slowed down) through the use of dynamic voltage scaling. The resulting re-schedule length with a strict energy budget should have a minimum amou...
Article
In our previous work, an image restoration algorithm based on modified Hopfield neural network and harmonic model was proposed. But the computational complexity of the algorithm is high. In this paper, a parallel image restoration algorithm based on the Harmonic model using modified Hopfield neural network (MHNN) is developed. The proposed algorith...
Article
This paper proposes an object-level rate control algorithm to jointly controlling the bit rates of multiple video objects. Utilizing noncooperative game theory, the proposed rate control algorithm mimics the behaviors of players representing video objects. Each player competes for available bits to optimize its visual quality. The algorithm finds a...
Conference Paper
Rate control in H.264/AVC aims to achieve the best tradeoff between encoding quality and bandwidth while satisfying the buffer restriction. Due to the improving efficiency of intra-only rate control, we propose an effective rate control scheme for intra-only encoding. The proposed scheme employs a novel rate-distortion (RD) model, a new complexity...
Conference Paper
This paper presents a novel rate control algorithm for H.264/AVC video coding. Pertinent to the algorithm, the paper introduces a joint R-D model, a coding bit estimation approach, a picture complexity measurement, and a model update method. Specifically, the proposed picture complexity measurement employs a harmonic mean based approach to predict...
Article
This paper addresses the problem of how to efficiently manage the power consumption while preserving high visual quality performance in video coding for pervasive video applications. We define an optimization problem that corresponds to the minimization of both the power consumption and video distortion of a video encoder. A joint rate-complexity-d...
Conference Paper
Full-text available
This paper proposes a technique to minimize the makespan of DAGs under energy constraints on multi-core processors that often need to operate under strict energy constraints. Most of the existing work aims to reduce energy subject to performance constraints. Thus, our work is in contrast to these techniques, and it is useful because one can encount...
Article
This paper proposes a non-cooperative game based technique to replicate data objects across a distributed system of multiple servers in order to reduce user perceived Web access delays. In the proposed technique computational agents represent servers and compete with each other to optimize the performance of their servers. The optimality of a non-c...
Article
Full-text available
The ten papers in this special section focus on power-aware parallel and distributed computing (PAPADS).
Article
The 14 regular papers and two brief papers in this special issue capture some of the state-of-the-art research on video surveillance issues, provide comprehensive overview of existing techniques, and propose novel solutions for important research problems.
Article
Motion estimation is a multistep process that encompasses techniques such as motion vector prediction, determination of search range and search patterns, and identification of termination criteria. Each of these techniques has several diversions that may suit a particular set of video characteristics. It would be hard to conceive a universal algori...
Conference Paper
Multi-core processors are beginning to revolutionize the landscape of high-performance computing. In this paper, we address the problem of power-aware scheduling/mapping of tasks onto heterogeneous and homogeneous multi-core processor architectures. The objective of scheduling is to minimize the energy consumption as well as the makespan of computa...
Conference Paper
Full-text available
Adaptive replication of data items on servers of a mobile ad hoc network can alleviate access delays. The selection of data items and servers requires solving a constrained optimization problem, that is in general NP-complete. The problem is further complicated by frequent partitions of the ad hoc network. In this paper, a mathematical model for da...
Article
This paper compares and analyzes 10 heuristics to solve the fine-grained data replication problem over the Internet. In fine-grained replication, frequently accessed data objects (as opposed to the entire website contents) are replicated onto a set of selected sites so as to minimize the average access time perceived by the end users. The paper pre...
Conference Paper
Creating replicas of frequently accessed data objects across a read intensive network can lead to reduced communication cost and end-user response time. On the contrary, data replication in the presence of writes incurs extra cost due to multiple updates. The selection of data objects and servers requires solving a constraint optimization problem,...
Conference Paper
In this paper, we consider the problem of MPEG-4 visual simple profile to H.264/AVC baseline profile (BP) transcoding. An efficient transcoding algorithm with fast mode selection and motion vector refinement is proposed. The proposed algorithm exploits the side information from the decoding stage to predict the coding modes and MVs of H.264/AVC BP...
Conference Paper
Object-based video coding, such as MPEG-4, supports the encoding and manipulating of individual video object. Rate control algorithm for multiple video object coding shall adapt to the perceptual importance of the video object. For this purpose, we present a joint rate control algorithm for coding multiple video objects. The proposed algorithm is a...
Article
Many believe that multi-view video is poised to change how people watch television and that it could become a driving force in interactive multimedia entertainment, for both desktop and mobile environments. An MVV system acquires several video sequences of the same scene simultaneously from more than one angle and transports these streams remotely....
Article
Full-text available
Replicating data over geographically dispersed web servers reduces network traffic, server load, and more importantly the user-perceived access delays. This paper proposes a unique replica placement technique using the concepts of a supergame. The supergame allows the agents who represent the data objects to continuously compete for the limited ava...
Conference Paper
Full-text available
Replicating data objects onto servers across a system can alleviate access delays. The selection of data objects and servers requires solving a constraint optimization problem, which is NP-complete in general. A majority of conventional replica placement techniques falter on issues of scalability or solution quality. To counteract such issues, we p...
Conference Paper
Full-text available
With the rapid growth of servers and applications spurred by the Internet, the power consumption of servers has become critically important and must be efficiently managed. High energy consumption also translates into excessive heat dissipation which in turn, increases cooling costs and causes servers to become more prone to failure. This paper pre...
Conference Paper
Exploitation of redundancies for superior coding efficiency is one of the major research issues in multi-view video coding (MVC). However, this incurs extra computation, counteracting the benefit gained from coding efficiency. This paper exploits inter-view correlations among video objects and background to lower the prediction complexity while ach...
Conference Paper
This paper addresses the issues of how to efficiently manage the power consumption while preserving high quality performance for video coding in futuristic pervasive computing environments. We formulate an optimization problem that corresponds to minimize both the power consumption and video distortion. A joint rate-complexity-distortion (R-C-D) mo...
Article
The Internet now offers more than just simple information to the users. Decision makers can now issue analytical, as opposed to transactional, queries that involve massive data (such as, aggregations of millions of rows in a relational database) in order to identify useful trends and patterns. Such queries are often referred to as Online-analytical...
Article
Full-text available
Priority queueing models have been commonly used in telecommu- nication systems. The development of analytically tractable models to determine their performance is vitally important. The discrete time batch Markovian arrival process (DBM AP) has been widely used to model the source behavior of data traffic, while phase-type ( PH )d is- tribution ha...
Conference Paper
In this paper we consider, compare and analyze three game theoretical grid resource allocation mechanisms. Namely, 1) the non-cooperative sealed-bid method where tasks are auctioned off to the highest bidder, 2) the semi-cooperative n-round sealed-bid method in which each site delegate its work to others if it cannot perform the work itself, and 3)...
Article
Motion estimation (ME) is a multistep process that involves not one, but a combination of techniques, such as motion starting point, motion search patterns, and adaptive control to curb the search, avoidance of search stationary regions, etc. The collective efficiency of these techniques is what makes a ME algorithm robust and efficient across the...
Article
This paper presents a game theory based technique for optimizing the bit rate control in video coding. Game theory, by virtue of its enormous potential for solving constrained optimization problems, has been effectively utilized in several branches of natural and social sciences. But this paper is the first attempt in using game theory for video co...
Article
In this paper, we propose a joint source-channel region-based rate control algorithm for real-time video transmissions over wireless systems. During the video transmission, the channel throughput available to the video encoder in the wireless systems is inherently variable, due to the retransmission of the error packets using the automatic repeat r...
Article
Minimization of the execution time of an iterative application in a heterogeneous parallel computing environment requires an appropriate mapping scheme for matching and scheduling the subtasks of a given application onto the processors. Often, some of the characteristics of the application subtasks are unknown a priori or change from iteration to i...
Conference Paper
Exploiting redundancy is the hallmark of traditional video coding but is even more essential in multi-view video coding (MVC). The exploitation of additional redundancies, however, incurs extra computational complexity, counteracting the benefits gained from coding efficiency. In this paper, we propose an efficient segmentation scheme for MVC, whic...
Conference Paper
Full-text available
This paper proposes a non-cooperative game theoretical replica allocation technique (NCOR) to reduce user perceived Web access delays. NCOR uses distributed agents that because of their local knowledge act in a self-interested manner in order to enhance the performance of the servers that they represent. This can lead to some performance gains for...
Article
The embedded multireference frames selection with variable block-size motion compensation model drastically increases the computational complexity of the H.264/AVC video coding standard. This paper proposes an adaptive hierarchical motion estimation (ME) algorithm for H.264/AVC with the objective of minimizing the complexity while maximizing the vi...
Conference Paper
This paper proposes an agent-based distributed replica allocation and management technique, where each agent maximizes its own benefit, such as, user access time, latency and communication cost. The technique gathers inspiration from market economy and game theoretical mechanism designs. In such mechanisms the agents do not have a global view of th...
Article
Obtaining an optimal schedule for a set of precedence-constrained tasks is a well-known NP-complete problem in its general form. In view of the intractability of the problem, most of the previous work relies on heuristics that try to find reasonably high quality solutions in an acceptable amount of time. While optimal polynomial-time algorithms are...
Article
In distributed web caching architectures, institutional proxies take advantage of their neighbors’ contents in order to reduce the number of requests forwarded to the server. Intuitively, the maximum benefit from this cooperation is expected when the proxies that exhibit similar requests are grouped together. The current practice is to follow a sta...
Article
One of the fundamental challenges in deploying multimedia systems, such as telemedicine, education, space endeavors, marketing, crisis management, transportation, and military, is to deliver smooth and uninterruptible flow of audio-visual information, anytime and anywhere. A multimedia system may consist of various devices (PCs, laptops, PDAs, smar...
Article
Object-based coding can potentially achieve a higher degree of compression and better visual quality. The objects in a scene are not always synchronous, that is, they have different temporal resolutions. In some applications, it is more efficient to transmit asynchronous objects with different temporal rates so as to achieve a better tradeoff betwe...
Article
Mobile devices performing video coding and streaming over wireless and pervasive communication networks are limited in energy supply. To prolong the operational lifetime of these devices, an embedded video encoding system should be able to adjust its computational complexity and energy consumption as demanded by the situation and its environment. T...
Conference Paper
This paper proposes a parallel implementation of the multiple sequence alignment algorithm, known as ClustalW, on distributed memory parallel machines. The proposed algorithm divides a progressive alignment into subtasks and schedules them dynamically. A task tree is built according to the dependency of the generated phylogenetic tree. The computat...
Conference Paper
In video transmission over two-way wireless channel automatic repeat request (ARQ) retransmission has been used to protect packets from losing, which also causes the channel throughput varying and brings more challenges to rate control of the video compression. This paper proposes a new rate control algorithm based on regions of interest (ROI), PID...
Article
This paper proposes a game theoretical rate control technique for video compression. Using a cooperative gaming approach, which has been utilized in several branches of natural and social sciences because of its enormous potential for solving constrained optimization problems, we propose a dual-level scheme to optimize the perceptual quality while...
Article
This paper proposes a game theoretical rate control technique for video compression. Using a cooperative gaming approach, which has been utilized in several branches of natural and social sciences because of its enormous potential for solving constrained optimization problems, we propose a dual-level scheme to optimize the perceptual quality while...
Article
For video coding in futuristic ubiquitous environments, how to efficiently manage the power consumption while preserving high video quality is crucial. To address the above challenge, we formulate a multiple objective optimization problem to model the behavior of power-distortion-optimized video coding. The objectives in this problem are incommensu...
Article
Full-text available
This paper extends some of the basic results on chess endgames. In par- ticular we analyze five famous endgames in the history of chess. We propose some new analytical constructs that help in understanding the outcome of the endgames and accurately project the winners. The generalized analysis of endgames enable us to obtain some remarkable game po...
Article
In video coding and streaming over wireless communication network, the power-demanding video encoding operates on the mobile devices with limited energy supply. To analyze, control, and optimize the rate-distortion (R-D) behavior of the wireless video communication system under the energy constraint, we need to develop a power-rate-distortion (P-R-...
Conference Paper
Full-text available
The Replica Placement Problem (RPP) aims at creating a set of duplicated data objects across the nodes of a distributed system in order to optimize certain criteria. Typically, RPP formulations fall into two categories: static and dynamic. The first assumes that access statistics are estimated in advance and remain static, and, therefore, a one-tim...
Conference Paper
Full-text available
This paper presents a novel multistage motion estimation (ME) scheme called content adaptive search technique (CAST). The proposed scheme consists of four stages: motion vector field (MVF) prediction, block-based segmentation, motion parameter extraction, and adaptive search strategy. Through pre-processing the MVF of the previous reference frame i...
Article
Fast dissemination and access of information in large distributed systems, such as the Internet, has become a norm of our daily life. However, undesired long delays experienced by end-users, especially during the peak hours, continue to be a common problem. Replicating some of the objects at multiple sites is one possible solution in decreasing net...
Article
Full-text available
Notoriously high delays in accessing Web pages loaded with massive multimedia objects are highly undesirable. Inspired by the requirements of news agencies and other information providers to include multimedia content in their pages, this paper proposes a new solution to the problem of minimizing the Web response time. We consider an environment th...
Article
This paper proposes a rate control algorithm for single and multiple objects video coding. The algorithm exploits prediction and feedback control to achieve accurate bit rate while maximizing the picture quality and simultaneously effectively handling buffer fullness. The algorithm estimates the bit budget of a frame based on its global coding comp...
Conference Paper
Full-text available
A multistage motion estimation scheme is proposed. The scheme extracts video characteristics by first performing an online video analysis separately for foreground and background regions. Motion parameters are extracted and passed to the next stage. The next stage includes a mathematical model for the block distortion surface (BDS) that enables the...
Conference Paper
This paper proposes a median-bias fast priority search algorithm for motion estimation. The main characteristic of the proposed algorithm is that it adapts a priority median-bias search pattern enabling the identification of locations with higher probability of finding the motion vector. Moreover, based on the history of motion vectors, the algorit...
Conference Paper
Motion estimation plays an important role in the motion compensated video coding framework. Due to the high computational complexity of the exhaustive search, many sub-optimal fast search algorithms, aiming to achieve the best trade off between distortion and search speed, are proposed. We observe that the distortion gradient of a search point on t...
Conference Paper
Full-text available
This work deals with layered video transmission over wireless networks. We focus on deriving the required bandwidth provisioning for each layered video given their respective QoS target. We model the layered video traffic by a discrete time batch Markovian arrival process (DBMAP) with marked transitions. We assume the link level behavior of the wir...
Article
With the scalability and flexibility of the MPEG-4 and the emergence of the broadband wireless network, wireless multimedia services are foreseen to become deployed in the near future. Transporting MPEG-4 video over the broadband wireless network is expected to be an important component of many emerging multimedia applications. One of the critical...
Article
Full-text available
This paper analyzes a certain class of combinatorial board games that in- cludes Ayo, Tchoukaillon and Modular N-queen. We refine the existing re- sults by providing simple and intuitive proofs using abstract combinatorics, and also reveal some interesting game positions.
Conference Paper
In wireless communication networks, an important issue that must be addressed is the limited energy supply of a mobile device, especially in wireless video applications. In this paper, we develop a parametric video encoding architecture, which is fully scalable in power consumption, and establish the power-rate-distortion (P-R-D) model of the video...
Conference Paper
This paper proposes a joint source-channel rate control algorithm for real-time video transmissions over WCDMA systems. The algorithm encompasses a region-based bit allocation strategy and a macro block-based segmentation technique. To enhance the video quality while saving bits, the algorithm effectively allocates more bits to important parts of a...
Conference Paper
In the recent years multimedia technology has emerged as a key technology, because of its ability to represent information in disparate forms as a bit-stream. This enables data from text to video and sound to be streamed, stored, processed, and delivered in digital form. A great part of the current research community effort has emphasized the deliv...
Conference Paper
Full-text available
In this paper we propose a traffic model for delivering scalable video encoded with multiple layers on heterogeneous networks. The model is based on Markovian arrival process with marked transitions. The state of the underlying Markov chain of the video arrival process is derived from the correlation feature found in the video data. The base layer...
Article
Full-text available
Configuration similarity is a special form of content-based image retrieval that considers relative object locations. It can be used as a standalone method, or to complement retrieval based on visual or semantic features. The corresponding queries ask for sets of objects that satisfy some spatio-temporal constraints, e.g., "find all triplets of obj...