Papers by R. Chandrasekaran
International Conference on Computer Communications and Networks, 2003
This paper presents the results of a comparative study of spare capacity assignment for original ... more This paper presents the results of a comparative study of spare capacity assignment for original quasipath restoration (OQPR), improved quasipath restoration (IQPR), link restoration (LR), path restoration (PR) and link-disjoint path restoration (LDPR) schemes. Numerical results indicate that the restoration schemes studied can be sorted from most expensive to least expensive (spare capacity assignment cost) in the following order: LR,
2006 International Symposium on a World of Wireless, Mobile and Multimedia Networks(WoWMoM'06), 2006
Cognitive radios CR have the ability to dynamically adapt to local spectrum availability. In a mu... more Cognitive radios CR have the ability to dynamically adapt to local spectrum availability. In a multi-hop wireless network comprised of CR-enabled devices, Medium Access Control (MAC) layer scheduling for data communication involves assignment of timeslots and ...
2011 31st International Conference on Distributed Computing Systems, 2011
An important first step when deploying a wireless ad hoc network is neighbor discovery in which e... more An important first step when deploying a wireless ad hoc network is neighbor discovery in which every node attempts to determine the set of nodes it can communicate within one wireless hop. In the recent years, cognitive radio (CR) technology has gained attention as an attractive approach to alleviate spectrum congestion. A CR transceiver can operate over a wide range of frequencies possibly spanning multiple frequency bands. A CR node can opportunistically utilize unused wireless spectrum without interference from other wireless devices in its vicinity. Due to spatial variations in frequency usage and hardware variations in radio transceivers, different nodes in the network may perceive different subsets of frequencies available to them for communication. This heterogeneity in the available channel sets across the network increases the complexity of solving the neighbor discovery problem in a CR network. In this paper, we design and analyze several randomized algorithms for neighbor discovery in such a (heterogeneous) network under a variety of assumptions.
International Conference on Distributed Computing Systems, 2011
An important first step when deploying a wireless ad hoc network is neighbor discovery in which e... more An important first step when deploying a wireless ad hoc network is neighbor discovery in which every node attempts to determine the set of nodes it can communicate within one wireless hop. In the recent years, cognitive radio (CR) technology has gained attention as an attractive approach to alleviate spectrum congestion. A CR transceiver can operate over a wide range
International Journal of Pervasive Computing and Communications, 2006
A critical issue in the design of routing protocols for wireless sensor networks is the efficient... more A critical issue in the design of routing protocols for wireless sensor networks is the efficient utilization of resources such as scarce bandwidth and limited energy supply. Many routing schemes proposed in the literature try to minimize the energy consumed in routing or maximize the lifetime of the sensor network without taking into consideration limited capacity of wireless links. This
SIAM Journal on Computing, 1997
ABSTRACT
Operations Research Letters, 1987
Operations Research, 1977
We consider a special case of the transportation problem with 3 supply points and n demand points... more We consider a special case of the transportation problem with 3 supply points and n demand points. An efficient algorithm is provided and the problem is illustrated with an example concerning financial aid to students.
Engineering Optimization, 1999
The design approximation problem is a well known problem in stock cutting, where, in order to fac... more The design approximation problem is a well known problem in stock cutting, where, in order to facilitate the optimization techniques used in the cutting process, it is required to approximate complex designs by simpler ones. Although there are algorithms available to solve this problem, they all suffer from an undesirable feature that they only produce one optimal solution to the problem, and do not identify the complete set of all optimal solutions. The focus of this paper is to study this hitherto unexplored aspect of the problem: specifically, the case is considered in which both the design and the parent material are convex shapes, and some essential properties of all optimal solutions to the design approximation problem are ascertained. These properties are then used to devise two efficient schemes to identify the set of all optimal solutions to the problem. Finally, the recovery of a desired optimal approximation from the identified sets of optimal solutions, is discussed.
Discrete Optimization, 2013
ABSTRACT In this paper, we design and analyze a simple, greedy algorithm for a class of linear pr... more ABSTRACT In this paper, we design and analyze a simple, greedy algorithm for a class of linear programs called Horn programs. This algorithm, which we term as the “Lifting Algorithm”, is a variant of the Stressing Algorithm proposed for Difference Constraint systems in [5] and runs in time O(m·n 2) on a Horn system with m constraints and n variables. Inasmuch as Horn constraints subsume difference constraints, and all known algorithms for the problem of checking feasibility in Difference Constraint Systems run in time Ω(m·n), the running time of our algorithm is only a factor n worse than the best known running time for checking feasibility in Difference Constraint Systems. Horn programs arise in a number of application areas including econometrics and program verification; consequently, their study is well-motivated. An important feature of our algorithm is that it uses only one operator, viz., addition. We also show that our algorithm can identify the linear and lattice point feasibility of Extended Horn Systems in O(m ·n 2) time.
Discrete Mathematics, 1988
In this paper we suggest a generalization of the well known ancept of matroid. This includes as s... more In this paper we suggest a generalization of the well known ancept of matroid. This includes as special cases generalized matroids due to A. Frank and some examples of 'Linking of matroids by linking systems' by A. Schrijver in addition to matroids. We do not see any direct relationship between this concept and that of greedoids introduced by Korte and LovasZ. The concept generalizes many aspects of matroids. These include combinatorial structures as well as optimization Froblems. We hope it will provide a unified framework for many of these problems.
Discrete Applied Mathematics, 2011
Motivated by applications in software programming, we consider the problem of covering a graph by... more Motivated by applications in software programming, we consider the problem of covering a graph by a feasible labeling. Given an undirected graph G = (V , E), two positive integers k and t, and an alphabet Σ, a feasible labeling is defined as an assignment of a set L v ⊆ Σ to each vertex v ∈ V , such that (i) |L v | ≤ k for all v ∈ V and (ii) each label α ∈ Σ is used no more than t times. An edge e = {i, j} is said to be covered by a feasible labeling if L i ∩ L j ̸ = ∅. G is said to be covered if there exists a feasible labeling that covers each edge e ∈ E. In general, we show that the problem of deciding whether or not a tree can be covered is strongly NP-complete. For k = 2, t = 3, we characterize the trees that can be covered and provide a linear time algorithm for solving the decision problem. For fixed t, we present a strongly polynomial algorithm that solves the decision problem; if a tree can be covered, then a corresponding feasible labeling can be obtained in time polynomial in k and the size of the tree. For general graphs, we give a strongly polynomial algorithm to resolve the covering problem for k = 2, t = 3.
Discrete Applied Mathematics, 1984
ABSTRACT
Discrete Applied Mathematics, 2004
... R. Chandrasekaran a , KPK Nair b , YP Aneja c , Corresponding Author Contact Information , E-... more ... R. Chandrasekaran a , KPK Nair b , YP Aneja c , Corresponding Author Contact Information , E-mail The Corresponding Author , SN Kabadi b. ... Given an undirected network G≡[N,E], asourcesink pair of nodes (s,t) in N, a non-negative number u i,j representing the capacity of ...
Discrete Applied Mathematics, 1994
There exist general purpose algorithms to solve the integer linear programming problem but none o... more There exist general purpose algorithms to solve the integer linear programming problem but none of them are polynomial. Polynomially bounded rounding algorithms have been studied, but most of them are problem specific. In this paper we study a generalized rounding algorithm that is polynomial, characterize matrices that may be used in this scheme and identify a class of integer programs that it solves.
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Papers by R. Chandrasekaran