Antonio Caruso

GPS free coordinate assignment and routing in wireless sensor networks

In this paper we consider the problem of constructing a coordinate system in a sensor network where location information is not available. To this purpose we introduce the virtual coordinate assignment protocol (VCap) which defines a virtual coordinate system based on hop distances. As compared to other approaches, VCap is simple and have very little requirements in terms of communication and memory overheads. We compare by simulations the performances of greedy routing using our virtual coordinate system with the one using the physical coordinates. Results show that the virtual coordinate system can be used to efficiently support geographic routing.

The Meandering Current Mobility Model and its Impact on Underwater Mobile Sensor Networks

Underwater mobile acoustic sensor networks are promising tools for the exploration of the oceans. These networks require new robust solutions for fundamental issues such as: localization service for data tagging and networking protocols for communication. All these tasks are closely related with connectivity, coverage and deployment of the network. A realistic mobility model that can capture the physical movement of the sensor nodes with ocean currents gives better understanding on the above problems. In this paper, we propose a novel physically-inspired mobility model which is representative of underwater environments. We study how the model affects a range-based localization protocol, and its impact on the coverage and connectivity of the network under different deployment scenarios.

Bounds on hop distance in greedy routing approach in wireless ad hoc networks

Wireless ad hoc networks are generally characterised by random node locations and multi-hop routes. A quantitative knowledge of the relation between hop count and Euclidean distance could provide a better understanding of important network parameters such as end-to-end delay, power consumption along the route, and node localisation. In this paper, we present an analytic approach to capture the statistics on hop count for a given source-to-destination Euclidean distance in a greedy routing approach. We also show that, for a given hop count, the bounds on Euclidean distance can be computed from the distribution characteristics of per-hop progress.

On service discovery in mobile social networks

Mobile social networks represent a convergence between mobile communications and service-oriented paradigms, which are supported by the large availability and heterogeneity of resources and services offered by recent mobile devices. In particular, the service-oriented nature of MSN is in the capability of sharing resources and services among devices that lie in proximity and that opportunistically interact. Service discovery is thus of primary importance to sustain the most intimate mechanisms of MSN. Despite of their centrality, studies on service discovery in MSN are still in their youth. We contribute to frame the results achieved so far and to identify some possible perspectives of the research in this field, by giving a transversal review of the scientific outcomes in the different steps of service discovery, namely advertisement, query, selection and access.

Worst-Case Diagnosis Completeness in Regular Graphs under the PMC Model

System-level diagnosis aims at the identification of faulty units in a system by the analysis of the system syndrome, that is, the outcomes of a set of interunit tests. For any given syndrome, it is possible to produce a correct (although possibly incomplete) diagnosis of the system if the number of faults is below a syndrome-dependent bound and the degree of diagnosis completeness, that is, the number of correctly diagnosed units, is also dependent on the actual syndrome sigma. The worst-case diagnosis completeness is a syndrome-independent bound that represents the minimum number of units that the diagnosis algorithm correctly diagnoses for any syndrome. This paper provides a lower bound to the worst-case diagnosis completeness for regular graphs for which vertex- isoperimetric inequalities are known and it shows how this bound can be applied to toroidal grids. These results prove a previous hypothesis about the influence of two topological parameters of the diagnostic graph, that is, the bisection width and the diameter, on the degree of diagnosis completeness.

Fault-diagnosis of grid structures

The problem of fault diagnosis in grid-connected systems is considered. A diagnosis algorithm, called DAGS and based on the PMC model, is presented. DAGS provides a diagnosis which is shown to be correct, although possibly incomplete, if the cardinality of the actual fault set is below a bound Tσ, dependent of the actual syndrome σ. A bound T independent of σ is also derived by a worst-case analysis covering the cases of triangular, square, hexagonal and octagonal grids. T is shown to be θ(n2/3), where n is the size of the system, for all the grids considered.

Reliable Routing in Wireless Ad Hoc Networks: The Virtual Routing Protocol

A novel routing protocol for wireless, mobile ad hoc networks is presented. This protocol incorporates features that enhance routing reliability, defined as the ability to provide almost 100% packet delivery rate. The protocol is based on a virtual structure, unrelated to the physical network topology, where mobile nodes are connected by virtual links and are responsible for keeping physical routes to their neighbors in the virtual structure. Routes between pairs of mobiles are set up by using information to translate virtual paths discovered in the virtual structure. Route discovery and maintenance phases of the protocol are based on unicast messages travelling across virtual paths, with sporadic use of flooding protocol. Most flooding is executed in the background using low priority messages. The routing protocol has been evaluated and compared with the Dynamic Source Routing protocol and with the Zone Routing Protocol by means of simulation.

A New Diagnosis Algorithm for Regular Interconnected Structures

We present a new diagnosis algorithm (NDA) for regular interconnected structures. The diagnosis algorithm has time complexity O(kn) when applied to k-regular systems of n units. It provides a correct diagnosis, although incomplete. The diagnosis is correct if the number of faulty units is not above a specified bound T σ , asserted by the algorithm itself. The correctness and completeness of NDA is studied through simulations on toroidal grids and hypercubes. Simulation results show that NDA provides a correct diagnosis even when the number of faults is very high (near half of the system size). The comparison between algorithm NDA and other diagnostic algorithms shows that NDA provides a better diagnosis, i.e., it has a higher degree of completeness than other diagnostic algorithms.

Virtual Naming and Geographic Routing on Wireless Sensor Networks

We consider the problem of routing with guaranteed delivery in wireless sensor networks where physical locations of the sensors are not known. We propose a naming protocol which defines a 2-dimensional coordinate system and a routing protocol (Ibrid) which ensures guaranteed delivery of packets. We show by means of simulation that in realistic settings where the network includes voids and obstacles, Ibridfinds routess hortest than those obtained with existing geographic routing algorithms over physical coordinates.

“Direction” Forwarding for Highly Mobile, Large Scale Ad Hoc Networks

In this paper, we present a novel packet forwarding scheme for wireless ad hoc networks --- “Direction” Forwarding (DFR). Popular routing protocols such as DSDV and AODV use “predecessor” based forwarding, namely, the packet is forwarded to the predecessor on the shortest path from the destination, as advertised during the last update. Predecessor forwarding may fail in large scale networks where the routing update rate must be reduced by the need to maintain link O/H below reasonable levels. However, if nodes are mobile, routing table entries may become “stale” very rapidly. DFR is designed to overcome the “stale” routing table entry problem. When the routing update arrives, the node remembers not only the predecessor delivering the update, but also the update “direction” of arrival. When a packet must be forwarded to destination, it is first forwarded to the node ID found in the routing table. If the node has moved and ID forwarding fails, the packet is “direction” forwarded to the “most promising” node in the indicated direction. At first glance, DFR seems to combine the features of table based routing and geo-routing. However, direction forwarding differs from geo-routing in that the direction is learned from the routing updates, instead of being computed from the destination coordinates. Thus, DFR does not require destination coordinates, a global coordinate system, or a Geo Location Server. In the paper we show the application of DFR to a scalable routing scheme, LANMAR. Through simulation experiments we show that DFR substantially enhances LANMAR performance in large, mobile network scenarios.