Several smart city monitoring applications use Mobile Crowd Sensing (MCS) technology to collect surrounding data events and send them to a central location for analysis. However, the majority of these applications use infrastructure networks that use direct communication (LTE, 5G) to transfer these data to the remote server. This leads to an increase in the load of the network bandwidth and comes at a higher data cost as well. This paper proposes an infrastructure-less routing protocol for MCS based on RPL (Routing Protocol for Low Power and Lossy Networks). However, RPL does not support mobility, and therefore, the proposed protocol is context-aware that adapts to the status and mobility of the nodes. The conducted performance evaluation reveals that the protocol performs better than the RPL in terms of packet delivery ratio (22% higher) and power consumption, due to the mobility management and the reduction in the control packet overhead (60% in low-medium mobility).

We propose a mathematical model for multiple sink placement in Underwater Wireless Sensor Networks (UWSNs). The model is constructed for a 3D mesh topology. Our objective is to minimize the overall number of hops of every source-closest sink pair of cells. We analyze the constructed model, and prove its hardness by reducing the k-median problem, a well-known NP-hard problem to our problem. We then use the Partitioning Around Medoid (PAM) approximation algorithm to find a near optimal solution to our sink placement problem. We test the solutions obtained by this approximation algorithm by comparing them with the optimal solutions obtained using a brute force method. We also compare the approximate solutions with solutions obtained using a random-based heuristic. Results show that the proposed PAM-based approximation achieves remarkably near-optimal solutions.

This paper describes the new fault-tolerant routing algorithm for k-ary n-cubes using the concept of "probability vectors" and conducts an extensive performance analysis for the new algorithm. To compute these vectors, a node determines first its faulty set, which represents the set of all its neighbouring nodes that are faulty or unreachable due to faulty links. Each node then calculates a probability vector, where the l/sup th/ element represents the probability that a destination node at distance l cannot be reached through a minimal path due to a fault node or link. The probability vectors are used by all the nodes to achieve an efficient fault-tolerant routing in the network. The extensive performance analysis conducted in this study reveals that the proposed algorithm exhibits good fault-tolerance properties in terms of the achieved average routing distances.

We conduct a general study of the topological properties of optical transpose interconnection systems (OTIS). We first obtain their basic topological metrics of size, degree, shortest distance and diameter, and then we obtain results related to the recursive structure and efficient embedding of meshes, cubes, spanning trees and cycles. We also present minimal one-to-one routing and optimal broadcasting algorithms, and we show how to construct node-disjoint paths between any two nodes of an OTIS network. Recent studies have addressed only particular members of the general class of OTIS networks. In this paper, we present unified tools for obtaining the topological properties of an arbitrary OTIS network based on the properties of the corresponding factor network.

This paper describes a new fault-tolerant routing algorithm for the hypercube, using the concept of probability vectors. To compute these vectors, a node first determines its faulty set, which represents the set of all its neighbouring nodes that are faulty or unreachable due to faulty nodes or links. Each node then calculates a probability vector, where the $k$th element represents the probability that a destination node at distance $k$ cannot be reached through a minimal path due to a faulty node or link. The probability vectors are used by all the nodes to achieve an efficient fault-tolerant routing in the network. A performance comparison with the recently proposed safety-vectors algorithm, through extensive simulation, shows that the new algorithm exhibits superior performance in terms of routing distances and percentage of reachability.

We present a number of results related to the fault tolerance of Cartesian product networks. We start by presenting a method for building containers (i.e., sets of node-disjoint paths) between any two nodes of a product network based on given containers for the factor networks. Then, we show that the best achievable fault diameter (i.e., diameter under maximum fault conditions), under reasonable network regularity and connectivity conditions, is equal to the fault-free diameter plus one. The concept of high fault resilience is then defined. We then prove that if each factor network is highly resilient, then their Cartesian product has minimal fault diameter. We derive from these results that Cartesian products of several popular networks are highly resilient and have minimal fault diameter equal to diameter plus one. These results spare future efforts that would be needed to individually determine the fault diameter of such networks as has been the practice with previously studied networks.

We study the cross product as a method for generating and analyzing interconnection network topologies for multiprocessor systems. Consider two interconnection graphs G/sub 1/ and G/sub 2/ each with some established properties such as symmetry, low degree and diameter, scalability, simple optimal routing, recursive structure (partitionability), fault tolerance, existence of node-disjoint paths, low cost embedding, and efficient broadcasting. We investigate and evaluate the corresponding properties for the cross product of G/sub 1/ and G/sub 2/ based on the properties of G/sub 1/ and those of G/sub 2/. We also give a mathematical characterization of product families of graphs which are closed under the cross product operation. This investigation is useful in two ways. On one hand, it gives a new tool for further studying some of the known interconnection topologies, such as the hypercube and the mesh, which can be defined using the cross product operation. On the other hand, it can be used in defining and evaluating new interconnection graphs using the cross product operation on known topologies.

We present and evaluate, for the first time, a parallel algorithm for solving the LU decomposition problem on the star graph. The proposed parallel algorithm is of O(N/sup 3//n!) computation complexity and uses O(Nn) communication time to decompose a matrix of order N on a star graph of dimension n, where N/spl ges/(n-1)!. The incurred communication time is better than the best known results for the hypercube, O(Nlogn!), and the mesh, O(N/spl radic/n!), each with approximately n! nodes. The proposed parallel algorithm takes advantage of the attractive topological qualities of the star graph in order to reduce the communication time involved in tasks such as pivoting, row/column interchanges, and pivot row and multipliers column broadcasts.

We obtain the fault diameter of k-ary n-cube interconnection networks (also known as n-dimensional k-torus networks). We start by constructing a complete set of node-disjoint paths (i.e., as many paths as the degree) between any two nodes of a k-ary n-cube. Each of the obtained paths is of length zero, two, or four plus the minimum length except for one path in a special case (when the Hamming distance between the two nodes is one) where the increase over the minimum length may attain eight. These results improve those obtained by B. Bose et al. (1995) where the length of some of the paths has a variable increase (which can be arbitrarily large) over the minimum length. These results are then used to derive the fault diameter of the k-ary n-cube, which is shown to be /spl Delta/+1 where /spl Delta/ is the fault free diameter.

Abstract The paper describes the approach taken for configuration management in the Nexus distributed operating system. Nexus uses kernel‐level support for monitoring the failure or termination status of distributed components of an application. Periodic user‐level messages are not required for status monitoring. Group and dependency relationships between such components can be defined by the programmer for the purpose of configuration monitoring and management. An object belonging to a distributed application can be monitored by its host kernel for system‐defined exception conditions. When any of these conditions arise, other objects are notified through signals or messages, as specified by the programmer.

Undertakes a comparative study of two important interconnection network topologies: the star graph and the hypercube, from the graph theory point of view. Topological properties are derived for the star graph and are compared with the corresponding properties of the hypercube. Among other results, the authors determine necessary and sufficient conditions for shortest path routing and characterize maximum-sized families of parallel paths between any two nodes of the star graph. These parallel paths are proven of minimum length within a small additive constant. They also define greedy and asymptotically balanced spanning trees to support broadcasting and personalized communication on the star graph. These results confirm the already claimed topological superiority of the star graph over the hypercube.>

This paper describes the approach taken for configuration management in the Nexus distributed operating system. Nexus uses kernel-level support for monitoring status of distributed components of an application. Periodic user-level messages are no longer required for status monitoring. Group and dependency relationships between such components can be defined by the programmer for the purpose of configuration monitoring and management. An object belonging to a distributed application can be monitored by its host kernel for some system-defined exception conditions. When any of these conditions arise, other objects are notified through signals or messages, as specified by the programmer.>

The use of a new topology, called the arrangement graph, as a viable interconnection scheme for parallel and distributed systems, has been recently proposed and examined. The arrangement graphs represent a rich class of generalized star graphs with many attractive properties, In this paper we obtain (1) unit expansion embeddings of a variety of multi-dimensional grids, (2) dilation 1, 2, 3, and 4 embeddings of hypercubes and (3) hierarchical and greedy spanning trees to support broadcasting and personalized communication in arrangement graphs.

Arrangement graphs have been proposed as an attractive interconnection topology for large multiprocessor systems. The authors study these graphs by proving the existence of Hamiltonian cycles in any arrangement graph. They also prove that an arrangement graph contains cycles of all lengths ranging between 3 and the size of the graph. They show that an arrangement graph can be decomposed into node disjoint cycles in many different ways.>