C.S. Raghavendra's research while affiliated with University of Southern California and other places

Publications (177)

Article
Full-text available
Wireless ad hoc networks have traditionally been assumed to use omni-directional anten-nas. However, it has been recently recognized that the use of advanced antenna technolo-gies could help alleviate the capacity limitations of multi-hop wireless networks, stemming from interference generated in the shared medium [1]. Adaptive array antennas have...
Article
Full-text available
Intermittently connected mobile networks are wireless networks where most of the time there does not exist a complete path from the source to the destination. There are many real networks that follow this model, for example, wildlife tracking sensor networks, military networks, vehicular ad hoc networks (VANETs), etc. In this context, conventional...
Article
Full-text available
Intermittently connected mobile networks are wireless networks where most of the time there does not exist a complete path from the source to the destination. There are many real networks that follow this model, for example, wildlife tracking sensor networks, military networks, vehicular ad hoc networks, etc. In this context, conventional routing s...
Book
This chapter reviews medium access control (MAC), an enabling technology in wireless sensor networks. MAC protocols control how sensors access a shared radio channel to communicate with neighbors. Battery-powered wireless sensor networks with many nearby nodes challenge traditional MAC design. This chapter discusses design trade-offs with an emphas...
Conference Paper
Full-text available
CITATION: C. Tang, A. T. Chronopoulos, C. S. Raghavendra, Soft-Timeout Distributed Key Generation for Digital Signature based on Elliptic Curve D-log for Low-power Devices, Proceedings of IEEE SecureComm 2005, The 1st IEEE/CreateNet International Conference on Security and Privacy for Emerging Areas in Communication Networks, Athens, Greece, pp. 35...
Conference Paper
In this paper, we propose a compression scheme called spatial set-partitioning in hierarchical trees which exploits the spatial and temporal correlations present in sensor data. This scheme allows progressive transmission and provides scalability in adapting to the underlying correlation structure of sensed data. It uses flexible Slepian-Wolf codin...
Conference Paper
This paper proposes a new routing paradigm for sensor networks called X visiting-pattern routing (XVR) that decouples visiting-patterns of packets from the routing core. Visiting-patterns indicate where to forward packets as next hops in a network and are essential to any routing service. With XVR, the visiting-patterns are defined in a separate mo...
Conference Paper
In-network processing is an appealing principle for resource conservation for sensor network applications. We propose a scheme to compress sensor array data in which one sensor has to send its readings to multiple neighbor sensors. This proposed scheme uses low-density parity-check code based Slepian-Wolf codes to compress these bit-planes extracte...
Conference Paper
A novel coding scheme is proposed for applications over wireless microsensor networks to meet both wireless link bandwidth and node energy constraints. First, an analysis is performed on the energy efficiency of coding schemes in wireless microsensor networks. Based on this analysis, we devise a power aware coding scheme, called EESPIHT which explo...
Conference Paper
Full-text available
Intermittently connected mobile networks are wireless networks where most of the time there does not exist a complete path from source to destination, or such a path is highly unstable and may break soon after it has been discovered. In this context, conventional routing schemes would fail. To deal with such networks we propose the use of an opport...
Conference Paper
Full-text available
Adaptive array antennas have the ability to respond automatically to an unknown interference environment, in real time, by steering s and reducing side lobe levels in the direction of interference, while retaining some desired signal beam characteristics. We present a protocol (ADAPT) that enables nodes in an ad hoc network to utilize adaptive arra...
Conference Paper
Sensor readings in a wireless microsensor network are correlated both spatially and temporally. Various coding and storage schemes and also other applications have been developed to exploit these correlations; therefore it is crucial to efficiently track the correlations. In this paper, a linear prediction algorithm is developed to initially establ...
Article
Sensor networks find use in a wide range of applications that involve distributed and collaborative computations.
Conference Paper
IEEE 802.15.4 is a new standard to address the need for low-rate low-power low-cost wireless networking. We provide in this paper one of the first simulation-based performance evaluations of the new medium access protocol in IEEE 802.15.4, focusing on its beacon-enabled mode for a star-topology network. We describe its key features such as the supe...
Conference Paper
This paper defines two modes for sensor networks with tripwires operating in a field, namely, monitoring mode and processing mode and proposes a collaborative two-stage detection scheme called DEAD which uses a group of tripwires to facilitate this. The experimental results show that this scheme can make a sensor network power aware with low overhe...
Conference Paper
Directional and smart antennas can be useful in increasing the capacity of wireless ad hoc networks. A number of media access and routing protocols have been recently proposed for use with such antennas, and have shown significant performance improvements over the omni-directional case. However, it is important to explore if and how different direc...
Conference Paper
This paper proposes a programmable routing framework that promotes the adaptivity in routing services for sensor networks. This framework includes a universal routing service and an automatic deployment service. The universal routing service allows the introduction of different services through its tunable parameters and programmable components. Th...
Conference Paper
Directional antennas can be useful in significantly increasing the capacity of wireless ad hoc networks. With directional antennas, independent communications between nodes can occur in parallel, even if the nodes are within range of each other. However, mutual interference by simultaneous transmissions limits the maximum number of such concurrent...
Conference Paper
Sensor networks are used in a variety of applications for event monitoring, environmental sensing and outer space exploration. An important application is detecting a target in the field using sensors gathering acoustic data. In this target detection application (ATR), a cluster of wireless sensors collected acoustic data and perform signal process...
Conference Paper
Full-text available
Distributed sensor networks are a significant technology nowadays. Inexpensive, smart devices with multiple sensors provide opportunities for instrumenting, monitoring and controlling targeting systems. Such sensor nodes have capability for acquiring and embedded-processing of variety of data forms. Collaborative signal processing and fusion algori...
Conference Paper
Small packets constitute a large fraction of packets in the Internet. Gathercast is a network layer service that combines small packets going to the same destination into a single packet, reducing the number of packets in the network and saving computations at intermediate routers. We propose a new model for gathercast using active network techniqu...
Conference Paper
In this paper a methodology for adapting existing wireless ad hoc network protocols to power controlled networks is presented. Wireless nodes are assumed to have transmission power control with m discrete levels, and a clustering scheme is used in the adaptation to be energy efficient. Clusters are formed among the nodes in a distributed self-organ...
Conference Paper
Directional antennas can be useful in significantly increasing node and network lifetime in wireless ad hoc networks. In order to utilize directional antennas, an algorithm is needed that will enable nodes to point their antennas to the right place at the right time. In this paper we present an energy-efficient routing and scheduling algorithm that...
Conference Paper
Proposes a media access control (MAC) protocol for situation aware, long range wireless local area networks (LANs) consisting of highly mobile nodes. We choose to schedule node transmissions instead of using contention-based protocols for accessing the channel. This approach is attractive for improving the performance of wireless LANs with long pro...
Article
Full-text available
Sensor networks find use in a wide range of applications that involve distributed and collaborative com-putations. Extensive research has focused upon design of time optimal parallel and distributed algorithms for two dimensional mesh connected computers (MCC). We show that a large set of parallel algorithms (see Property 4.1), that take time Òµ an...
Article
In this paper we present a case for using new power-aware metrics for determining routes in wireless ad hoc networks. We present five different metrics based on battery power consumption at nodes. We show that using these metrics in a shortest-cost routing algorithm reduces the cost/packet of routing packets by 5-30% over shortest-hop routing (this...
Conference Paper
Ad hoc wireless networks and sensor networks have nodes with limited battery power, and broadcasting is an important operation in such networks. In this paper, we consider energy efficient one-to-all and all-to-all broadcast communications in such power constrained networks. It is assumed that nodes have power control and can adjust the range of th...
Article
We present MILAN, a model based extensible framework that facilitates rapid, multigranular performance evaluation of a large class of embedded systems, by seamlessly integrating different widely used simulators into a unified environment. MILAN provides a formal paradigm for specification of structural and behavioral aspects of embedded systems, an...
Article
In this paper we present five different power-aware metrics based on battery power consumption
Article
Clusters of workstations and networked parallel computing systems are emerging as promising computational platforms for HPC applications. The processors in such systems are typically interconnected by a collection of heterogeneous networks such as Ethernet, ATM, and FDDI, among others. In this paper, we develop techniques to perform block-cyclic re...
Article
Full-text available
A major challenge in Metacomputing Systems (Computational Grids) is to effectively use their shared resources, such as compute cycles, memory, communication network, and data repositories, to optimize desired global objectives. In this paper we develop a unified framework for resource scheduling in metacomputing systems where tasks with various req...
Conference Paper
In heterogeneous computing systems, an application often requires multiple resources of different types to be allocated simultaneously. This is the resource co-allocation problem. We develop a framework for mapping a collection of applications with resource co-allocation requirements. In our framework, application tasks have two types of constraint...
Article
Full-text available
Run-time array redistribution is necessary to enhance the performance of parallel programs on distributed memory supercomputers. In this paper, we present an efficient algorithm for array redistribution from cyclic(x) on P processors to cyclic(Kx) on Q processors. The algorithm reduces the overall time for communication by considering the data tran...
Article
Full-text available
. We show that deadlocks due to dependencies on consumption channels is a fundamental problem in multicast wormhole routing. This issue of deadlocks has not been addressed in many previously proposed multicast algorithms. We also show that deadlocks on consumption channels can be avoided by using multiple classes of consumption channels and restric...
Conference Paper
Full-text available
Multistage network based input-buffered ATM switches, which have been studied extensively, are cheaper compared to crossbar designs but suffer from elaborate cell selection methods or expensive network setup. In this paper, a fast cell selection method is proposed to avoid slow cell selection and costly network setup for these designs. In particula...
Conference Paper
The Information Power Grid (IPG) is emerging as an infrastructure that will enable distributed applications-such as videoconferencing and distributed interactive simulation-to seamlessly integrate collections of heterogeneous workstations, multiprocessors, and mobile nodes over heterogeneous wide-area networks. This paper introduces a framework for...
Conference Paper
Run-time array redistribution is necessary to enhance the performance of parallel programs on distributed memory supercomputers. In this paper, we present an efficient algorithm for array redistribution from cyclic(x) on P processors to cyclic(Kx) on Q processors. The algorithm reduces the overall time for communication by considering the data tran...
Article
. The all-to-all personalized communication is a massive data movement operation that arises frequently in problems like large matrix transposition on hypercube computers. In literature, various researchers have proposed routing methods to solve this problem using multiport packet switching communication, which is not practical. In this paper, we p...
Conference Paper
Full-text available
The routing and signaling protocols for supporting multipoint-to-multipoint connections in ATM networks have been presented earlier. VP-merge and VC-merge techniques have been proposed as the likely candidates for resolving the sender identification problem associated with these connections. The additional buffer requirements in the VC-merge mechan...
Conference Paper
In this paper we develop a new multi-access protocol for multi-hop radio networks. The unique feature of our protocol is that it is energy conserving. Radios that are not actively transmitting or receiving a packet power themselves off. The manner in which nodes power themselves off does not influence the delay or throughput characteristics of our...
Article
Computation time for various primitive operations, such as broadcasting and global sum, can significantly increase when there are node failures in a hypercube. In this paper we develop nearly optimal algorithms for computing important basic problems on a faulty SIMD hypercube. In an SIMD hypercube, during a communication step, nodes can exchange in...
Article
In this paper, we develop algorithms in order of efficiency for all-to-all broadcast problem in an N=2<sup>n</sup>-node n-dimensional faulty SIMD hypercube, Q<sub>n</sub>, with up to n-1 node faults. The algorithms use a property of a certain ordering of dimensions. Our analysis includes startup time (α) and transfer time (β). We have established t...
Article
Full-text available
We show that deadlocks due to dependencies on consumption channels are a fundamental problem in wormhole multicast routing. This type of resource deadlocks has not been addressed in many previously proposed wormhole multicast algorithms. We also show that deadlocks on consumption channels can be avoided by using multiple classes of consumption chan...
Article
In this paper we develop a new multiaccess protocol for ad hoc radio networks. The protocol is based on the original MACA protocol with the adition of a separate signalling channel. The unique feature of our protocol is that it conserves battery power at nodes by intelligently powering off nodes that are not actively transmitting or receiving packe...
Conference Paper
Several multimedia applications like video-conferencing and distributed interactive simulations require efficient support for multipoint-to-multipoint connections from the underlying networks. The routing and signaling protocols for supporting these connections in ATM networks have been proposed earlier by Venkateswaran et al. (see IEEE ATM'97 Work...
Article
Ray tracing is a well known technique to generate life-like images. Unfortunately, ray tracing complex scenes can require large amounts of CPU time and memory storage. Distributed memory parallel computers with large memory capacities and high processing speeds are ideal candidates to perform ray tracing. However, the computational cost of renderin...
Conference Paper
In this paper, we present a scalable dynamic multicast routing algorithm based on a dynamic Steiner tree approach. First, we analyze a hierarchical multicast routing algorithm which introduced the use of core nodes in each peer-group to support multicasting under the private network-network interface (PNNI) framework. Based on this analysis, we con...
Conference Paper
In this paper, we present a distributed multicast routing protocol (DMRP) for dynamic computation of multicast trees. This protocol is a distributed version of a centralized heuristic for dynamic Steiner tree computation. The protocol is deadlock-free and is a correct implementation of the centralized heuristic. It can be easily extended to the hie...
Conference Paper
A significant barrier inhibiting the use of parallel computing is the difficulty of writing parallel software. One solution to this problem is to build tools that can automatically convert sequential programs to parallel programs. In this paper we describe the implementation of a system that is designed to perform a semantic level analysis and tran...
Article
Exact performance analysis of dynamic load-balancing policies for distributed systems is known to be very difficult owing to the facts that the state space is multidimensional and that load-balancing decisions are state dependent. In this paper, a state-aggregation method is proposed to model and analyze dynamic load-balancing policies. Those state...
Article
In a sort-last polygon rendering system, the efficiency of image composition is very important for achieving fast rendering. In this paper, the implementation of a sort-last rendering system on a general purpose multicomputer system is described. A two-phase sort-last-full image composition scheme is described first, and then many variants of it ar...
Article
Data parallel languages like HPF require the user to specify the distribution of the data in the application. This distribution is specified over the processors on which the application is to execute. A good data distribution depends on the number of processors, the communication latency and the underlying compilation system. Hence it is difficult...
Article
This paper presents an accurate model for evaluating the mean system size of parallel queues with the Join the Shortest Queue (JSQ) policy. The system considered consists of N identical queues with infinite buffers, and each of the queues has one server. The job arrival process is assumed to be Poisson. The service times are assumed to be exponenti...
Conference Paper
In this paper, we extend the hierarchical PNNI (private network node interface or private network network interface) point-to-point routing protocols [Dykeman, 1995] to support multicast routing in ATM networks. Our idea is based on the core-based tree idea for inter-domain multicast routing in the Internet [Ballardie et al., 1993]. Our idea uses m...
Conference Paper
Extends our prior results [Raghavendra & Sridhar (1992, 1993), Sengupta & Raghavendra (1994)] to obtain algorithms for performing all-to-all broadcast, global sum and broadcast operation in an N-node (N=2<sup>n</sup>), n-dimensional faulty SIMD hypercube, Q<sub>n</sub> (n&ges;9), with the number of faults n-1<f&les;2n-3. We also discuss optimal alg...
Article
In this paper, the problem of broadcasting in ann-dimensional SIMD hypercube,Qn, with up ton− 1 node faults is studied. In an SIMD hypercube, during a communication step, nodes can exchange information with their neighbors only across a specific dimension. The broadcasting algorithms must work independent of the location of the source node and faul...
Article
Recently, the diameter problem for packed exponential connections (PEC) networks was addressed by Cho-Chin Lin and V. K. Prasanna [Proc. Symposium on Parallel and Distributed Processing, 1992, pp. 368–375], who presented asymptotically tight bounds for the diameter and showed asymptotically optimal routing algorithms. In this paper exact, solutions...
Article
We consider the problem of computing a global commutative and associative operation, also known as semi-group operation, (such as addition and multiplication) on a faulty hypercube. In particular, we study the problem of performing such an operation in an n-dimensional SIMD hypercube, Q<sub>n</sub>, with up to n-1 node and/or link faults. In an SIM...
Article
We consider the problem of embedding and reconfiguring binary tree structures in faulty hypercubes. We assume that the number of faulty nodes is at most (n-2), where n is the number of dimensions of the hypercube; we further assume that the location of faulty nodes are known. Our embedding techniques are based on a key concept called free dimension...
Article
This paper presents an accurate analytical model for evaluating the performance of the join the shortest queue (JSQ) policy. The system considered consists of N identical queues each of which may have single or multiple servers. A birth-death Markov process is used to model the evolution of the number of jobs in the system. Our results show that th...
Article
In the proposed algorithm, several single population genetic algorithms with different cross-over and mutation parameters are run as a set of processes that cooperate periodically and exchange information to solve the problem efficiently. The algorithm is less stochastic than the standard genetic algorithm and a distributed implementation is approp...
Conference Paper
An important issue facing users who develop applications on PVM is that of partitioning the data over the different processors and generating communication statements for non-local data accesses. The burden of generating communication statements is alleviated by data parallel languages like HPF. HPF requires the user to specify the distribution of...
Conference Paper
Full-text available
Loops without dependences among iterations are a rich source of parallelism in many applications. Among these types of loops, non-uniform loops with variable execution times need efficient scheduling schemes to take advantages of the capabilities of parallel machines. We present a global distributed control scheme (GDC) to schedule nonuniform loops...
Conference Paper
High speed networking applications like video-on-demand require the support of switches which can handle very high multicast loads. B-ISDN switches with multicasting capabilities can be used to support such applications efficiently. These switches must be fast and the routing delays for the packets must be small. The switches studied in the literat...
Article
Hypercube network is an attractive structure for parallel processing due to its symmetry and regularity. We use the concept of free dimensions to achieve fault tolerance in hypercubes without requiring additional spare processing nodes; such additional redundancy requires modification of hypercube structure. A free dimension is defined to be a dime...
Conference Paper
We present an improved multicast routing algorithm for self-routing multistage networks with circulating data. This multicast routing algorithm uses two passes through the network, and is based on the cube concept where a cube consists of a group of outlets reachable in one pass through the multistage network. A given multicast connection set, cons...
Article
We present methods to store and access templates of data arrays in parallel processors with shuffle-exchange-type interconnection networks. For this purpose, we define the class of composite linear permutations. In our method, each element of the data array is stored in the memory module determined by applying a suitable composite linear permutatio...
Article
Self-routing interconnection networks with their low processing-overhead delay and decentralized routing, are an attractive option for switching fabrics in high speed networks. These interconnection networks, however, realize only a subset of all possible input-output permutations in a non-blocking fashion. The non-blocking property of these networ...
Article
A residual hypercube is an arbitrary subgraph induced by a subset of the nodes of the hypercube. Residual hypercubes can be used to model the availability of only some of the nodes of a hypercube, e.g., in fault tolerance and processor allocation problems. A residual hypercube may be specified either by listing all the nodes included in the subgrap...
Conference Paper
Ray tracing is one of the computer graphics techniques used to render high quality images. Ray tracing complex scenes can require large amounts of CPU time and memory storage. We present a parallel implementation of the ray tracing algorithm on the Intel Delta parallel computer. Two key issues of efficient implementation are load balancing and data...
Conference Paper
We address a significant problem in parallel processing research, namely, how to port existing sequential programs to run efficiently on parallel machines (the “dusty deck” problem). Conventional domain-independent techniques are inadequate for solving this problem because they miss significant opportunities of parallelism. We present experimental...
Conference Paper
We address a significant problem in parallel processing research, namely, how to port existing sequential programs to run efficiently on parallel machines (the “dusty deck” problem). Conventional domain-independent techniques are inadequate for solving this problem because they miss significant opportunities of parallelism. We present experimental...
Conference Paper
We show that deadlocks due to dependencies on consumption channels is a fundamental problem in multicast wormhole routing. This issue of deadlocks has not been addressed in many previously proposed multicast algorithms. We also show that deadlocks on consumption channels can be avoided by using multiple classes of consumption channels and restricti...
Conference Paper
Ray tracing is one of the computer graphics techniques used to render high quality images. Unfortunately, the ray tracing of complex scenes can require large amounts of CPU time, making the technique impractical for everyday use. Since the ray tracing calculations that determine the values of individual pixels are independent, this appears to be an...
Article
In this paper we study methods for routing data in supercomputers that use multistage interconnection networks (MINs), in the presence of faulty components in the network. These methods are applicable to existing multiprocessors like IBM GF11 and RP3. These methods are based on the concept of dynamic full-access(DFA) which refers to the ability of...
Conference Paper
Ray tracing is one of the computer graphics techniques used to render high quality images. Unfortunately, ray tracing complex scenes can require large amounts of CPU time, making the technique impractical for everyday use. Parallel ray tracing algorithms could potentially be used to reduce the high computational cost. However, pixel computation tim...
Article
Circuit-switched communication has been increasingly used in hypercube multiprocessors. Reserve-and-hold strategy is commonly used to establish a circuit-switched path between a pair of nodes in the hypercube. With this strategy, a routing algorithm has to be designed with sufficient care to avoid deadlocks. A commonly used, deadlock-free routing a...
Article
In this paper we present schemes for reconfiguration of embedded task graphs in hypercubes. Previous results, which use either fault-tolerant embedding or an automorphism approach, can be expensive in terms of either the required number of spare nodes or reconfiguration time. Using the free dimension concept, we combine the above two approaches in...
Article
Fault tolerance in hypercubes is achieved by exploiting inherent redundancy and executing tasks on faulty hypercubes. The authors consider tasks that require linear chain, ring, mesh, and torus structure, which are quite useful in parallel and pipeline computations. They assume the number of faults is on the order of the number of dimensions of the...