WorldCat Identities

Kumar, P. R.

Works: 76 works in 115 publications in 2 languages and 1,175 library holdings
Genres: Conference proceedings 
Roles: Author, Editor, Other
Classifications: QA402, 003
Publication Timeline
Most widely held works by P. R Kumar
Stochastic systems : estimation, identification, and adaptive control by P. R Kumar( Book )

8 editions published in 1986 in English and held by 315 WorldCat member libraries worldwide

Adaptive control, filtering, and signal processing by Karl J Åström( Book )

9 editions published in 1995 in English and held by 178 WorldCat member libraries worldwide

The area of adaptive systems, which encompasses recursive identification, adaptive control, filtering, and signal processing, has been one of the most active areas of the past decade. Since adaptive controllers are fundamentally nonlinear controllers which are applied to nominally linear, possibly stochastic and time-varying systems, their theoretical analysis is usually very difficult. Nevertheless, over the past decade much fundamental progress has been made on some key questions concerning their stability, convergence, performance, and robustness. Moreover, adaptive controllers have been successfully employed in numerous practical applications, and have even entered the marketplace
Discrete event systems, manufacturing systems, and communication networks by P. R Kumar( Book )

7 editions published in 1995 in English and held by 151 WorldCat member libraries worldwide

The study of discrete event dynamical systems (DEDS) has become rapidly popular among researchers in systems and control, in communication networks, in manufacturing, and in distributed computing. This development has created problems for researchers and potential "consumers" of the research. The first problem is the veritable Babel of languages, formalisms, and approaches, which makes it very difficult to determine the commonalities and distinctions among the competing schools of approaches. The second, related problem arises from the different traditions, paradigms, values, and experiences that scholars bring to their study of DEDS, depending on whether they come from control, communication, computer science, or mathematical logic. As a result, intellectual exchange among scholars becomes compromised by unexplicated assumptions
Scaling laws for ad hoc wireless networks : an information theoretic approach by Feng Xue( Book )

6 editions published in 2006 in English and held by 17 WorldCat member libraries worldwide

In recent years there has been significant and increasing interest in ad hoc wireless networks. The design, analysis and deployment of such wireless networks necessitate a fundamental understanding of how much information transfer they can support, as well as what the appropriate architectures and protocols are for operating them. This monograph addresses these questions by presenting various models and results that quantify the information transport capability of wireless networks, as well as shed light on architecture design from a high level point of view. The models take into consideration important features such as the spatial distribution of nodes, strategies for sharing the wireless medium, the attenuation of signals with distance, and how information is to be transferred, whether it be by encoding, decoding, choice of power level, spatio-temporal scheduling of transmissions, choice of multi-hop routes, or other modalities of cooperation between nodes. An important aspect of the approach is to characterize how the information hauling capacity scales with the number of nodes in the network. The monograph begins by studying models of wireless networks based on current technology, which schedules concurrent transmissions to take account of interference, and then routes packets from their sources to destinations in a multi-hop fashion. An index of performance, called transport capacity, which is measured by the bit meters per second the network can convey in aggregate, is studied. For arbitrary networks, including those allowing for optimization of node locations, the scaling law for the transport capacity in terms of the number of nodes in the network is identified. For random networks, where nodes are randomly distributed, and source-destination pairs are randomly chosen, the scaling law for the maximum common throughput capacity that can be supported for all the source-destination pairs is characterized. The constructive procedure for obtaining the sharp lower bound gives insight into an order optimal architecture for wireless networks operating under a multi-hop strategy. To determine the ultimate limits on how much information wireless networks can carry requires an information theoretic treatment, and this is the subject of the second half of the monograph. Since wireless communication takes place over a shared medium, it allows more advanced operations in addition to multi-hop. To understand the limitations as well as possibilities for such information transfer, wireless networks are studied from a Shannon information-theoretic point of view, allowing any causal operation. Models that characterize how signals attenuate with distance, as well as multi-path fading, are introduced. Fundamental bounds on the transport capacity are established for both high and low attenuation regimes. The results show that the multi-hop transport scheme achieves the same order of scaling, though with a different pre-constant, as the information theoretically best possible, in the high attenuation regime. However, in the low attenuation regime, superlinear scaling may be possible through recourse to more advanced modes of cooperation between nodes. Techniques used in analyzing multi-antenna systems are also studied to characterize the scaling behavior of large wireless networks
Packets with deadlines : a framework for real-time wireless networks by I-Hong Hou( Book )

6 editions published in 2013 in English and held by 16 WorldCat member libraries worldwide

"With the explosive increase in the number of mobile devices and applications, it is anticipated that wireless traffic will increase exponentially in the coming years. Moreover, future wireless networks all carry a wide variety of flows, such as video streaming, online gaming, and VoIP, which have various quality of service (QoS) requirements. Therefore, a new mechanism that can provide satisfactory performance to the complete variety of all kinds of flows, in a coherent and unified framework, is needed. In this book, we introduce a framework for real-time wireless networks. This consists of a model that jointly addresses several practical concerns for real-time wireless networks, including per-packet delay bounds, throughput requirements, and heterogeneity of wireless channels. We detail how this framework can be employed to address a wide range of problems, including admission control, packet scheduling, and utility maximization."--Page [vi]
Research on rapeseed & mustard : proceedings of an Indo-Swedish Symposium, September 4-6, 1989( Book )

4 editions published in 1990 in English and held by 10 WorldCat member libraries worldwide

Proceedings, twenty-fifth annual Allerton Conference on Communication, Control, and Computing : conference held September 30-October 2, 1987, Allerton House, Monticello, Illinois by Control, and Computing Allerton Conference on Communication( Book )

3 editions published in 1987 in English and held by 8 WorldCat member libraries worldwide

Lecture series in mobile telecommunications and networks : transcripts of the third series of three lectures, March 2008 - February 2009 by P. R Kumar( Book )

1 edition published in 2009 in English and held by 6 WorldCat member libraries worldwide

Stochastic optimal control and stochastic differential games by P. R Kumar( Book )

4 editions published between 1977 and 1979 in English and held by 4 WorldCat member libraries worldwide

Brassica Oliseeds : breeding and management( Book )

1 edition published in 2015 in English and held by 3 WorldCat member libraries worldwide

Closed-loop analysis and feedback design in the presence of limited information by Dapeng Li( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Recent progress in communication technologies and their use in feedback control systems motivate to look deeper into the interplay of control and communication in the closed-loop feedback architecture. Among several research directions on this topic, a great deal of attention has been given to the fundamental limitations in the presence communication constraints. Entropy rate inequalities corresponding to the information flux in a typical causal closed loop have been derived towards obtaining a Bode-like integral formula. This work extends the discrete-time result to continuous-time systems. The main challenge in this extension is that Kolmogorov's entropy rate equality, which is fundamental to the derivation of the result in discrete-time case, does not hold for continuous-time systems. Mutual information rate instead of entropy rate is used to represent the information flow in the closed-loop, and a limiting relationship due to Pinsker towards obtaining the mutual information rate between two continuous time processes from their discretized sequence is used to derive the Bode-like formula. The results are further extended to switched systems and a Bode integral formula is obtained under the assumption that the switching sequence is an ergodic Markov chain. To enable simplified calculation of the resulting lower bound, some Lie algebraic conditions are developed. Besides analysis results, this dissertation also includes joint control/communication design for closed-loop stability of performance. We consider the stabilization problem within Linear Quadratic Regulator framework, where a control gain is chosen to minimize a linear quadratic cost functional while subject to the input power constraint imposed by an additive Gaussian channel which closes the loop. Also focused on Gaussian channel, the channel noise attenuation problem is addressed, by using H-infinity/H2 methodology. Similar feedback optimal estimation problem is solved by using Kalman filtering theory
Mode identification using stochastic hybrid models with applications to conflict detection and resolution by Asal Naseri Kouzehgarani( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

Most models of aircraft trajectories are non-linear and stochastic in nature; and their internal parameters are often poorly defined. The ability to model, simulate and analyze realistic air traffic management conflict detection scenarios in a scalable, composable, multi-aircraft fashion is an extremely difficult endeavor. Accurate techniques for aircraft mode detection are critical in order to enable the precise projection of aircraft conflicts, and for the enactment of altitude separation resolution strategies. Conflict detection is an inherently probabilistic endeavor; our ability to detect conflicts in a timely and accurate manner over a fixed time horizon is traded off against the increased human workload created by false alarms that is, situations that would not develop into an actual conflict, or would resolve naturally in the appropriate time horizon-thereby introducing a measure of probabilistic uncertainty in any decision aid fashioned to assist air traffic controllers. The interaction of the continuous dynamics of the aircraft, used for prediction purposes, with the discrete conflict detection logic gives rise to the hybrid nature of the overall system. The introduction of the probabilistic element, common to decision alerting and aiding devices, places the conflict detection and resolution problem in the domain of probabilistic hybrid phenomena. A hidden Markov model (HMM) has two stochastic components: a finite-state Markov chain and a finite set of output probability distributions. In other words an unobservable stochastic process (hidden) that can only be observed through another set of stochastic processes that generate the sequence of observations. The problem of self separation in distributed air traffic management reduces to the ability of aircraft to communicate state information to neighboring aircraft, as well as model the evolution of aircraft trajectories between communications, in the presence of probabilistic uncertain dynamics as well as partially observable and uncertain data. We introduce the Hybrid Hidden Markov Modeling (HHMM) formalism to enable the prediction of the stochastic aircraft states (and thus, potential conflicts), by combining elements of the probabilistic timed input output automaton and the partially observable Markov decision process frameworks, along with the novel addition of a Markovian scheduler to remove the non-deterministic elements arising from the enabling of several actions simultaneously. Comparisons of aircraft in level, climbing/descending and turning flight are performed, and unknown flight track data is evaluated probabilistically against the tuned model in order to assess the effectiveness of the model in detecting the switch between multiple flight modes for a given aircraft. This also allows for the generation of probabilistic distribution over the execution traces of the hybrid hidden Markov model, which then enables the prediction of the states of aircraft based on partially observable and uncertain data. Based on the composition properties of the HHMM, we study a decentralized air traffic system where aircraft are moving along streams and can perform cruise, accelerate, climb and turn maneuvers.We develop a common decentralized policy for conflict avoidance with spatially distributed agents (aircraft in the sky) and assure its safety properties via correctness proofs
A digital interface for wireless networks by Anand Muralidhar( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

This dissertation addresses the problem of determining the capacity of wireless networks and how to operate them. Within this context we present results on Gaussian relay, interference, and multicast networks. Two new models for wireless networks are introduced here: the discrete network and the superposition network. As with a Gaussian network, one can construct either a discrete network or a superposition network. The discrete network is obtained by simply quantizing the received signals in the Gaussian model and by restricting the transmit signals to a finite alphabet. The superposition network, inspired by the Gaussian model, is a noiseless deterministic network, the inputs and outputs of the channels are discrete, and channel gains are signed integers. The capacity of a class of Gaussian relay networks and its corresponding discrete or superposition network is always within a bounded gap, where the gap is independent of channel gains or signal-to-noise ratio (SNR), and depends only on the number $M$ of nodes in the network. More importantly, a near-optimal coding strategy for either the discrete or the superposition network can be converted into a near-optimal coding strategy for the original Gaussian network. Hence, both these networks serve as near-optimal digital interfaces for operating the Gaussian network. The discrete network is obtained from a Gaussian network by simply quantizing the received signals and restricting transmitted signals to a certain finite precision. Since its signals are obtained from those of a Gaussian network and its transmissions are transmittable as-is on a Gaussian network, the discrete network provides a particularly simple quantization-based digital interface for operating layered Gaussian relay networks. These are relay networks in which the nodes are grouped into layers, and only nodes of one layer can transmit to the nodes of the next layer. The cut-set upper bounds on the capacities of the Gaussian and the discrete network are within an SNR-independent bounded gap of $O(M log M)$ bits. Moreover, a simple linear network code is a near-optimal coding strategy for the discrete relay network, achieving all rates within $O(M^2)$ bits of its cut-set bound, where the bound is independent of channel gains or SNR. The linear code can be used as-is on the Gaussian network after quantizing its received signals. It achieves all rates within $O(M^2)$ bits of the capacity for Gaussian relay networks. The linear network code improves on existing approximately-optimal coding schemes for the relay network by virtue of its simplicity and robustness, and it explicitly connects wireline network coding with codes for Gaussian networks. The approximation of Gaussian networks by other previously proposed deterministic networks is also studied in this dissertation, and two main results are presented, one positive and the other negative. The gap between the capacity of a Gaussian relay network and a corresponding linear deterministic network can be unbounded. The key reasons are that the linear deterministic model fails to capture the phase of received signals, and there is a loss in signal strength in the reduction to a linear deterministic network. On the positive side, Gaussian relay networks with a single source-destination pair are indeed well approximated by the superposition network. The difference between the capacity of a Gaussian relay network and the corresponding superposition network is bounded by $O(M log M)$ bits, where the gap is again independent of channel gains or SNR. As a corollary, multiple-input multiple-output (MIMO) channels cannot be approximated by the linear deterministic model but can be by the superposition model. A code for a Gaussian relay network can be designed from {em any} code for the corresponding superposition network simply by pruning it, suffering no more than a rate loss of $O(M log M)$ bits that is independent of SNR. Similar results hold for the $K times K$ Gaussian interference network, MIMO Gaussian interference networks, MIMO Gaussian relay networks, and multicast networks, with the constant gap depending additionally on the number of antennas in case of MIMO networks
Enforcing cooperation and providing quality of service in wireless networks by Juan J Jaramillo Jimenez( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

The purpose of this dissertation is to design algorithms that provide quality of service and enforce cooperation in wireless ad hoc networks. Using a simple network model, we first study the performance of some previously proposed cooperation-enforcing strategies and then present a new mechanism. We prove that our mechanism is robust to imperfect measurements, is collusion-resistant, and can achieve full cooperation among nodes. Assuming cooperation is being enforced, we then study the problem of optimal routing and admission control for flows which require a pre-specified bandwidth from the network. We develop an algorithm whose performance is close to that of an omniscient off-line algorithm that has complete a priori knowledge of the entire sequence of flow arrivals and their bandwidth requests, including the future. We then study the problem of congestion control and scheduling in wireless ad hoc networks that have to support a mixture of best-effort and real-time traffic. We propose a model for incorporating the requirements of packets with deadlines in an optimization framework. The solution to the problem results in a joint congestion control and scheduling algorithm which fairly allocates resources to meet the fairness objectives of both elastic and inelastic flows, and the per-packet delay requirements of inelastic flows
Ramana pahavanum thirukkoiyilkalum by P. R Kumar( Book )

1 edition published in 2010 in Tamil and held by 2 WorldCat member libraries worldwide

Temples in South India
Verification and Enforcement of State-Based Notions of Opacity in Discrete Event Systems by Anooshiravan Saboori( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Motivated by security and privacy considerations in applications of discrete event systems, we describe and analyze the complexity of verifying various state-based notions of opacity in systems that are modeled as (possibly non-deterministic) finite automata with partial observation on their transitions. Assuming that the intruder observes system activity through some projection map and has complete knowledge of the system model, we define three notions of opacity with respect to a set of secret states: (i) initial-state opacity is a notion that requires the membership of the system true initial state to the set of secret states remain opaque (i.e., uncertain) to the intruder; (ii) K-step opacity is a notion that requires that at any specific point in time within the last K observations, the entrance of the system state to the given set of secret states remain opaque to the intruder; (iii) infinite-step opacity is a notion that requires the entrance of the system state at any particular instant to the set of secret states remain opaque, for the length of the system operation, to the intruder. As illustrated via examples in the thesis, the above state-based notions of opacity can be used to characterize the security requirements in many applications, including encryption using pseudo-random generators, coverage properties in sensor networks, and anonymity requirements in protocols for web transactions. In order to model the intruder capabilities regarding initial-state opacity, we address the initial-state estimation problem in a non-deterministic finite automaton under partial observations on its transitions via the construction of an initial-state estimator. We analyze the properties and complexity of the initial-state estimator, and show how the complexity of the verification method can be greatly reduced in the special case when the set of secret states is invariant (i.e., it does not change over time). We also establish that the verification of initial-state opacity is a PSPACE-complete problem. In order to verify K-step opacity, we introduce the K-delay state estimator which constructs the estimate of the state of the system K observations ago (K-delayed state estimates) for a given non-deterministic finite automaton under partial observation on its transitions. We provide two methods for constructing K-delay state estimators, and hence two methods for verifying K-step opacity, and analyze the computational complexity of both. In the process, we also establish that the verification of $K$-step opacity is an NP-hard problem. We also investigate the role of the delay K in K-step opacity and show that there exists a delay K* such that K-step opacity implies K'-step opacity for any K and K' such that K'>K>= K*. This is not true for arbitrary K'>K though the converse holds trivially. Infinite-step opacity can be verified via the construction of a current-state estimator and a bank of appropriate initial-state estimators. The verification of infinite-step opacity is also shown to be a PSPACE-hard problem. Finally, we tackle the problem of constructing a minimally restrictive opacity-enforcing supervisor (MOES) which limits the system's behavior within some pre-specified legal behavior while enforcing opacity requirements. We characterize the solution to MOES, under some mild assumptions, in terms of the supremal element of certain controllable, normal, and opaque languages. We also show that this supremal element always exists and that it can be implemented using state estimators. The result is a supervisor that achieves conformance to the pre-specified legal behavior while enforcing opacity by disabling, at any given time, a subset of the controllable system events, in a way that minimally restricts the range of allowable system behavior
Generalized Nash games with shared constraints: Existence, efficiency, refinement and equilibrium constraints by Ankur A Kulkarni( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

The thesis pertains to some fundamental questions in the theory of games. Our focus is on a class of noncooperative N -player games, called generalized Nash games with shared constraints, or simply, shared-constraint games. In such a game, every strategy-tuple is constrained to lie in a subset C of the product space of strategies. Thus strategies available to a player are only those which when taken jointly with the strategies of all other players, form a tuple that lies in C. The set C is called the shared constraint. Despite their relevance in real-world settings, there are many theoretical properties of these games that are not well understood. What interests us in this thesis is the theoretical character of the equilibria of these games. Shared-constraint games admit two kinds of equilibria: generalized Nash equilibria (GNE) that are ill-posed and often intractable and a smaller subset of them (called variational equilibria or VE) satisfying an exogenous regularity condition that are well-posed and surprisingly tractable. We seek to clarify the nature of these equilibria, study their economic implications and exploit their properties to advance the analytical theory for conventional and somewhat unconventional shared-constraint games. The unconventional shared-constraint games are in fact a class of dynamic games, called multi-leader multi-follower games, which we view through the lens of shared constraints. Four questions are addressed in this thesis with the central theme as shared-constraint games. In the first part of the thesis we present a refinement of the GNE. A refinement of an equilibrium is a subset of the set of equilibria which is nonempty whenever the original set of equilibria is nonempty. Refined equilibria are representative of the set of equilibria and have additional properties that make them more attractive as solution concepts than the original equilibria. The contribution of this work is a theory that gives sufficient conditions for a game to admit the VE as a refinement of the GNE. These conditions are expressed in terms of the Brouwer degree, which is seen to relate the GNE and the VE in a profound manner. Importantly, for certain classes of games, these conditions are also seen to be necessary. The degree theoretic relationship holds in both, primal and primal-dual space. Our work unifies some previously known results and provides mathematical justification for ideas that were known to be intuitive appealing but were hitherto unsubstantiated formally. The second part of this thesis is about multi-leader multi-follower games. These games are highly nonconvex and irregular and no reliable theory is available for claiming the existence of equilibria of these games. We develop such a theory for multi-leader multi-follower games with shared constraints. The application of standard fixed point arguments to the reaction map of general multi-leader multi-follower games is hindered by the lack of suitable continuity properties, amongst other requirements, in this map. We observe that these games bear a close resemblance to shared-constraint games and present modifications of the canonical multi-leader multi-follower game that result in shared-constraint games, with far more favorable properties. Specifically, a global equilibrium of this game exists when a suitably defined modified reaction map admits a fixed point. Sufficient conditions for the existence of these fixed points are obtained via topological fixed point theory. Finally, the paradigm developed is applied to a class of LCP-constrained leader problems where conditions for the contractibility of the domain are derived via the theory of retracts. The third part of thesis concerns the use of variational inequalities for claiming the existence of an equilibrium to shared-constraint games. The equilibrium conditions of a generalized Nash game can be compactly stated as a quasi-variational inequality (QVI), an extension of the variational inequality (VI). Harker showed that under certain conditions on the maps defining the QVI, a solution to a related VI solves the QVI. But the application of Harker⁰́₉s result to the QVI associated with shared-constraint games proves difficult because its hypotheses can fail to hold even for simple shared-constraint games. We show these hypotheses are in fact impossible to satisfy in most settings. But we show that for a modified QVI, whose solution set equals that of the original QVI, the hypothesis of Harker⁰́₉s result always hold. This paves the way for applying this result to shared-constraint games, albeit in an indirect manner. This avenue allows us to recover as a special case, a result proved by Facchinei et al., in which it is shown that a suitably defined variational inequality provides a solution to the QVI of a shared-constraint game. In the fourth part we take a system-level view of shared-constraint games that result from resource allocation. We clarify the relation between this mode of allocating resources and the other conventional modes via either perfect competition or through the use of a mechanism. We find that for perfectly competitive settings the VE is the same as the competitive equilibrium. We then compare the performance of GNE and VE of the shared-constraint game with respect to the system-level objective of maximization of social welfare or aggregate utility. We are specifically interested in the efficiency of an equilibrium, which is the ratio of the aggregate utility for this equilibrium to the optimal aggregate utility, and in the lowest value this efficiency can take for a class of utility functions. We show that for a certain class of utility functions the VEs are fully efficient. We characterize this class and show that departures from this setting can lead to arbitrarily low efficiency in the worst case. Specifically, in this class, even while the VEs are efficient, GNEs can be arbitrarily inefficient, and VEs of games not belonging to the ⁰́₈efficient⁰́₉ class can have arbitrarily low efficiency in the worst case. Finally we suggest ways to remedy the low efficiency of equilibria in these cases. We find that a more restricted class of utility functions, in which the gradient map of every member utility function is bounded away from zero and from above uniformly over the domain, gives a more favorable worst case efficiency. We then consider a game where players incur costs that, from the system point of view are not additive, whereby the system problem is not merely the sum of the objectives of all players. We characterize utility functions for which the VE is efficient under this notion of efficiency. Finally we consider the imposition of a reserve price on players. The reserve price has the effect of eliminating players with low interest in the resource. The GNE is more indicative of the system optimal. We find that under certain conditions, efficiency as high as unity is obtainable by the imposition of an appropriate reserve price
Proceedings of the ACM/IEEE 4th International Conference on Cyber-Physical Systems by IEEE/ACM International Conference on Cyber-Physical Systems( )

1 edition published in 2013 in English and held by 0 WorldCat member libraries worldwide

Mathematical foundations of complex networked information systems : Politecnico di Torino, Verrès, Italy 2009 by Mathematical foundations of complex networked information systems (Summer School)( )

1 edition published in 2015 in English and held by 0 WorldCat member libraries worldwide

Introducing the reader to the mathematics beyond complex networked systems, these lecture notes investigate graph theory, graphical models, and methods from statistical physics. Complex networked systems play a fundamental role in our society, both in everyday life and in scientific research, with applications ranging from physics and biology to economics and finance. The book is self-contained, and requires only an undergraduate mathematical background
ANC'13 : proceedings of the 2013 Workshop on Airborne Networks and Communications : July 29, 2013, Bangalore, India by ACM MobiHoc Workshop on Airborne Networks and Communications( )

1 edition published in 2013 in English and held by 0 WorldCat member libraries worldwide

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Adaptive control, filtering, and signal processing
Alternative Names
Kumar, P. R.

Kumar, Panganamala Ramana

Panqanamala Ramana Kumar

English (58)

Tamil (1)

Scaling laws for ad hoc wireless networks : an information theoretic approach