Ashok K. Agrawala - Profile on Academia.edu (original) (raw)

Papers by Ashok K. Agrawala

Communications of The ACM, Nov 1, 1977

arXiv (Cornell University), Mar 24, 2015

In pervasive computing environments, various entities often have to cooperate and integrate seaml... more In pervasive computing environments, various entities often have to cooperate and integrate seamlessly in a situation which can, thus, be considered as an amalgamation of the context of several entities interacting and coordinating with each other, and often performing one or more activities. However, none of the existing context models and ontologies address situation modeling. In this paper, we describe the design, structure and implementation of a generic, flexible and extensible context ontology called Rover Context Model Ontology (RoCoMO) for context and situation modeling in pervasive computing systems and environments. We highlight several limitations of the existing context models and ontologies, such as lack of provision for provenance, traceability, quality of context, multiple representation of contextual information, as well as support for security, privacy and interoperability, and explain how we are addressing these limitations in our approach. We also illustrate the applicability and utility of RoCoMO using a practical and extensive case study.

In this survey paper, we overview the various network traffic models, especially focusing on the ... more In this survey paper, we overview the various network traffic models, especially focusing on the multiscale analysis. By multiscale analysis we mean wavelet-based self-similar and multifractal analysis. Multiscale analysis is advantageous in that it can reveal the scaling behavior of the traffic on large time scale, at the same time characterize small-scale irregularity. We also discuss how we can apply this analysis technique to wireless LAN traffic characterization. For many applications, to represent statistics of stochastic processes the expected value of £ ¤ § ¦ © and of £ ¤ § ¦ © are used. These time-dependent quantities can be expressed in terms of the second-order properties of

Packet error in the IEEE 802.11 network is one source of performance degradation and its variabil... more Packet error in the IEEE 802.11 network is one source of performance degradation and its variability. Most of the previous works study how collision avoidance and hidden terminals affect 802.11 performance metrics, such as probability of a collision and saturation throughput. In this paper we focus on the effect of packet errors on capacity and variability of the 802.11 MAC protocol. We develope a new analytical model, called Ô-Model, by extending the existing model (Tay and Chua's model) to incorporate packet error probability Ô. With Ô-Model, we successfully analyze capacity and variability of the 802.11 MAC protocol. The variability analysis shows that increasing packet error probability by ¡Ô has more effect on saturation throughput, than adding ¼ Ï ¡Ô stations, where Ï is the minimum contention window size, We also show the numerical validation of Ô-Model with 802.11 MAC-level simulator.

Acquisition, distribution, management, and analysis of information are the fundamental purposes b... more Acquisition, distribution, management, and analysis of information are the fundamental purposes behind most complex constructed systems and infrastructures, and yet a process-centric approach is fundamental to the design and implementation of such systems. Since information is the essential commodity in these endeavors, we believe that an effective design should take into account the fundamental properties of information: its characteristics, its representation, its value, its temporal dynamics, its fusion, its distillation, etc. Information Dynamics is an attempt to bring a degree of rigor to the understanding of the nature of information itself and how it is used in the pursuit of system objectives.

This report presents a general analysis for the performance of WLAN location determination system... more This report presents a general analysis for the performance of WLAN location determination systems. In particular, we present an analytical method for calculating the average distance error and probability of error of WLAN location determination systems. These expressions are obtained with no assumptions regarding the distribution of signal strength or the probability of the user being at a specific location, which is usually taken to be a uniform distribution over all the possible locations in current WLAN location determination systems. We use these expressions to find the optimal strategy to estimate the user location and to prove formally that probabilistic techniques give more accuracy than deterministic techniques, which has been taken for granted without proof for a long time. The analytical results are validated through simulation experiments. We also study the effect of the assumption that the user position follows a uniform distribution over the set of possible locations on the accuracy of WLAN location determination systems. The results show that knowing the probability distribution of the user position can reduce the number of access points required to obtain a given accuracy. However, with a high density of access points, the performance of a WLAN location determination system is consistent under different probability distributions for the user position.

We study permutations of the job order performed by various LIFO service disciplines. The sets of... more We study permutations of the job order performed by various LIFO service disciplines. The sets of such permutations are shown to be equivalent to sets of string permutations with simple characteristics. In particular, it is easy to test whether a given permutation belongs to these sets. Several algorithms that e ciently perform such tests are presented.

The scheduling problem is considered to be a crucial part in the design of real-time distributed ... more The scheduling problem is considered to be a crucial part in the design of real-time distributed computer systems. This paper gives an extensive survey of the research performed in the area of real-time scheduling, which includes localized and centralized scheduling and allocation techniques. We classify the scheduling strategies into four basic categories: static and dynamic priorities, heuristic approaches, scheduling with precedence relations, allocation policies and strategies. DTIC EECT E MAR 14 1988El i IF rH t Mu wok is mppow d W p by g1 s No. W61-HA-40O79 OV frm Wetnghoe Eleric Company, and No. NO004-M-0=41 from the Oflim d Naval Reaadch to thr Danmtaa of Comiuler ciec, Univeully of Mmyland at College I Park. DmmTWB"ON STATEMNT ] Aprw for public rel.com Dtattbution Unlimited

Springer eBooks, 2005

We define techniques to compute energy-efficient reliable paths within the framework of on-demand... more We define techniques to compute energy-efficient reliable paths within the framework of on-demand routing protocols. The choice of energy-efficient reliable paths depend on link error rates on different wireless links, which in turn depend on channel noise. We show how our scheme accounts for such channel characteristics in computing such paths. Additionally, we perform a detailed study of the AODV protocol and our energy-efficient variants, under various noise and node mobility conditions. Our results show that our proposed variants of on-demand routing protocols can achieve orders of magnitude improvement in energy-efficiency of reliable data paths.

arXiv (Cornell University), Sep 23, 2022

The present study proposes a novel method of trend detection and visualization-more specifically,... more The present study proposes a novel method of trend detection and visualization-more specifically, modeling the change in a topic over time. Where current models used for the identification and visualization of trends only convey the popularity of a singular word based on stochastic counting of usage, the approach in the present study illustrates the popularity and direction that a topic is moving in. The direction in this case is a distinct subtopic within the selected corpus. Such trends are generated by modeling the movement of a topic by using k-means clustering and cosine similarity to group the distances between clusters over time. In a convergent scenario, it can be inferred that the topics as a whole are meshing (tokens between topics, becoming interchangeable). On the contrary, a divergent scenario would imply that each topics' respective tokens would not be found in the same context (the words are increasingly different to each other). The methodology was tested on a group of articles from various media houses present in the 20 Newsgroups dataset.

The Computer Journal, 2017

Machine-to-machine communications (M2M) technology enables large-scale communication and networki... more Machine-to-machine communications (M2M) technology enables large-scale communication and networking of devices of various kinds including home devices and appliances. A critical issue for home M2M networks is how to efficiently integrate the already existing home consumer devices and appliances into an IP based wireless M2M network with least modifications to existing components. Due to its popularity and widespread usage in closed spaces, Wi-Fi is a good alternative as a wireless technology to enable M2M networking for home devices. This thesis addresses the energy-efficient integration of home appliances to a Wi-Fi and IP based home M2M network. Towards this goal, we first propose an integration architecture that requires least modifications in existing components. Then, we propose a novel long-term sleep scheduling algorithm to be applied together with the existing 802.11 power save mode (PSM). The proposed scheme utilizes the multicast DNS (mDNS) protocol to maintain device and service availability when devices go into deep sleep mode. We implemented our proposed architecture and algorithm as a prototype to build an M2M network of home appliances as a test-bed. We performed various experiments on this test-bed to evaluate the proper operation and energy savings of our proposal. We also did extensive simulation experiments for larger-scale scenarios. As a result of our test-bed and simulation experiments, we observed energy savings up to 70% compared to the existing infrastructure which applies no sleep mechanism, and up to 20% compared to standard 802.11 PSM scheme, while ensuring device and service availability at the same time.

Bibliography 27 Appendix A: Description and Format of the Log Entries. 29 Appendix B: The Format ... more Bibliography 27 Appendix A: Description and Format of the Log Entries. 29 Appendix B: The Format of the Program Control Table. . 61 vi * EXEC-8 is a registered trademark of the United Software Corporation and is the Operating System used on the UNIVAC 1100 series machines (UNIVAC 1106, 1108, and 1110). For the purpose of this report we will use EXEC-8 and "the Executive" interchangeably. 157 he following current-awareness and literature-survey hibliraphies are issued periodically by the Bureau: ryogenic Data Center Current Awareness Service. A literature survey issued biweekly.

A cooperative framework to scale multi-party applications

We define a framework to implement multi-party applications in which cooperation between applicat... more We define a framework to implement multi-party applications in which cooperation between application peers is leveraged to achieve scalability. In this framework, the peers cooperate by devoting a part of their own resources to be used by other peers of the same application group. Through detailed analysis, simulations, and implementations, we demonstrate that applications implemented using this approach can achieve significant performance benefits. There are two major aspects to scalably implement cooperative applications—resource provisioning and management, and handling the impact of peer failures on application performance. In this thesis we define efficient techniques to address both these aspects. Resource limitation is the most typical reason that constrain the scalability of applications. Therefore we first study resource provisioning and management at application peers. We do this using two examples. The first example application is the group key distribution problem that arises in secure group communication systems. Our proposed solution to this problem is based on the cooperative approach and is, therefore, fundamentally different from all existing solutions to this problem. We perform detailed comparisons with best-known existing techniques to demonstrate that our proposed scheme incurs the least processing, storage and communication overheads. As a second example we examine the one-many data transfer problem. We proposed a scalable solution to this problem using a cooperative approach known as application-layer multicast. This solution constructs provably efficient data delivery structures, guarantees low control overheads, and is the most scalable application-layer multicast protocol known today. Next we study the impact of peer failures on application performance. While the cooperative model for multi-party applications enables scalability, it adds dependencies between application peers. Consequently failures of some peers affect the performance at other peers. Efficient failure recovery techniques, therefore, form an important component of cooperation-based implementations of multi-party applications. We examine this aspect of cooperative applications using the application-layer multicast example. We define a simple, robust, low-overhead data recovery technique that efficiently handles failures of application peers. (Abstract shortened by UMI.)

Locus: robust and calibration-free indoor localization, tracking and navigation for multi-story buildings

Journal of Location Based Services, 2015

A fundamental goal of indoor localisation technology is to achieve the milestone of combining min... more A fundamental goal of indoor localisation technology is to achieve the milestone of combining minimal cost with accuracy sufficient enough for general consumer applications. To achieve this, current indoor positioning systems need either extensive calibration or expensive hardware. Moreover, very few systems built so far have addressed floor determination in multi-story buildings. In this paper, we explain a Wi-fi-based indoor localisation, tracking and navigation system for multi-story buildings called Locus. Locus determines a device’s floor as well as location on that floor using existing knowledge of infrastructure, and without requiring any calibration or proprietary hardware. It is an inexpensive solution with minimum set-up and maintenance expenses, is scalable, readily deployable and robust to environmental changes. Experimental results in three different buildings spanning multiple floors show that it can determine the floor with 95.33% accuracy and the location on the floor with an error of 6.49 m on an average in real-life practical environments. We also demonstrate its utility via two location-based applications for indoor navigation and tracking in emergency scenarios.

Proceedings of the 12th EAI International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services, 2015

A context-aware system uses context to provide relevant information and services to the user, whe... more A context-aware system uses context to provide relevant information and services to the user, where relevancy depends on the user's situation. This relevant information could include a wide range of heterogeneous content. Many existing context-aware systems determine this information based on pre-defined ontologies or rules. In addition, they rely on users' context history to filter it. Moreover, they often provide domain-specific information. Such systems are not applicable to a large and varied set of user situations and information needs, and may suffer from cold start for new users. In this paper, we address these limitations and propose a novel, general and flexible approach for bootstrapped discovery and ranking of heterogeneous relevant services and information in context-aware systems. We design and implement four variations of a base algorithm that ranks candidate relevant services, and the information to be retrieved from them, based on the semantic relatedness between the information provided by the services and the user's situation description. We conduct a live deployment with 14 subjects to evaluate the efficacy of our algorithms. We demonstrate that they have strong positive correlation with human supplied relevance rankings and can be used as an effective means to discover and rank relevant services and information. We also show that our approach is applicable to a wide set of users' situations and to new users without requiring any user interaction history.

Multi-armed bandit problem is a classic example of the exploration vs. exploitation dilemma in wh... more Multi-armed bandit problem is a classic example of the exploration vs. exploitation dilemma in which a collection of one-armed bandits, each with unknown but fixed reward probability, is given. The key idea is to develop a strategy, which results in the arm with the highest reward probability to be played such that the total reward obtained is maximized. Although seemingly a simplistic problem, solution strategies are important because of their wide applicability in a myriad of areas such as adaptive routing, resource allocation, clinical trials, and more recently in the area of online recommendation of news articles, advertisements, coupons, etc. to name a few. In this dissertation, we present different types of Bayesian Inference based bandit algorithms for Two and Multiple Armed Bandits which use Order Statistics to select the next arm to play. The Bayesian strategies, also known in literature as "Thompson Method" are shown to function well for a whole range of values, including very small values, outperforming UCB and other commonly used strategies. Empirical analysis results show a significant improvement in both synthetic and real

Categorization and performance analysis of advanced avionics algorithms on parallel processing architectures

Proceedings of the IEEE National Aerospace and Electronics Conference

Some of the emerging candidate advanced avionics algorithms for next-generation aircraft and miss... more Some of the emerging candidate advanced avionics algorithms for next-generation aircraft and missions are discussed. Details of algorithm categorization and architecture classification and categorization are presented. In addition, a methodology for mapping the algorithms into the parallel-processing architectures is developed. In order to determine the algorithm performance on candidate architectures, a task graph is constructed for the critical processing areas, indicating data dependencies, memory accesses, throughputs, data rates, primitives, and timing requirements. Both the primitives and processing architectures are categorized, and a heuristic mapping is performed. For each task graph and primitive, candidate architectures are analyzed in order to determine performance metrics.<<ETX>>

Proceedings of the IEEE, 1968

Two versioaf of M ursllpervised leprning a J g o r i h for pat-Navy 05ce of Naval Research Contra... more Two versioaf of M ursllpervised leprning a J g o r i h for pat-Navy 05ce of Naval Research Contract N00014-67-A-0204M119. Manuscript rapived February 13, I W. Thh work was supported principally by U. S. Pergamon Rgs 1%5, p. 332. ' M. Born and E. Wolf, Principles of Optics, 3rd revised ed.