Mauro Tropea

Hop-by-Hop Local Flow Control over InterPlaNetary Networks Based on DTN Architecture

Deep space communications are an important research line in scientific community. The possibility of performing the communication between earth and other planets is an excitant challenge. The main issue of the communication between planet, called interplanetary (IPN) communication, is the intermittent visibility due to planet movement and the long propagation delay. In order to solve these problems a delay tolerant network (DTN) has been deployed. DTN is an architecture particularly useful in scenarios where very long transmission delays or intermittent connectivity are present, such as IPN network. The routers in DTN perform a transmission mechanism similar to the model of mail transfer protocols or the store-and-forward and it permits to determine a hop-by-hop based messages exchange. Our main contribute in this paper is the introduction of an asynchronous congestion control mechanism on the network that it is not present in the traditional DTN protocol. This control tries to resolve buffer overflow, link saturation and useless retransmission problems in order to better utilize the overall system.

Integrated Services on High Altitude Platform: Receiver Driven Smart Selection of HAP-Geo Satellite Wireless Access Segment and Performance Evaluation

A renewed interest in the development of high-altitude platforms (HAPs), which are stratospheric aircraft or airship carrying payloads tailored for a wide range of applications in telecommunications and remote sensing, is becoming progressively widespread. HAPs offer a reduced propagation delay and they are especially suitable for interactive multimedia services. In this paper, the inter-working between HAP and satellite segments in an integrated QoS architecture has been addressed. A new way to manage integrated services over a new hybrid wireless platform has been proposed. A smart terminal device has been considered in order to perform an intelligent switching on the wireless access segment. The switching criteria applied in the HAP/satellite architecture is based on the available bandwidth and on the admissible data packet end-to-end delay. Performance evaluations of the integrated HAP–satellite platform have been evaluated in terms of bandwidth utilization and number of admitted calls. The simulations show an improvement of admitted calls, reduced data packet end-to-end delay and increased bandwidth utilization.

An enhanced QoS CBT multicast routing protocol based on Genetic Algorithm in a hybrid HAP-Satellite system

A QoS multicast routing scheme based on Genetic Algorithms (GA) heuristic is presented in this paper. Our proposal, called Constrained Cost-Bandwidth-Delay Genetic Algorithm (CCBD-GA), is applied to a multilayer hybrid platform that includes High Altitude Platforms (HAPs) and a Satellite platform. This GA scheme has been compared with another GA well-known in the literature called Multi-Objective Genetic Algorithm (MOGA) in order to show the proposed algorithm goodness. In order to test the efficiency of GA schemes on a multicast routing protocol, these GA schemes are inserted into an enhanced version of the Core-Based Tree (CBT) protocol with QoS support. CBT and GA schemes are tested in a multilayer hybrid HAP and Satellite architecture and interesting results have been discovered. The joint bandwidth-delay metrics can be very useful in hybrid platforms such as that considered, because it is possible to take advantage of the single characteristics of the Satellite and HAP segments. The HAP segment offers low propagation delay permitting QoS constraints based on maximum end-to-end delay to be met. The Satellite segment, instead, offers high bandwidth capacity with higher propagation delay. The joint bandwidth-delay metric permits the balancing of the traffic load respecting both QoS constraints. Simulation results have been evaluated in terms of HAP and Satellite utilization, bandwidth, end-to-end delay, fitness function and cost of the GA schemes.

A New Routing Protocol for Interference and Path-Length Minimization in Vehicular Networks

Vehicular communication systems represent one of the most desirable technologies when the safety, efficiency and comfort of everyday road travel need to be improved. The main advantage is the absence of an infrastructure, typical of centralized networks, that makes them very scalable and adequate for highly-variable network topologies. Vehicular Ad-hoc NETworks (VANETs) are able to provide wireless networking capability in situations where no fixed infrastructure exists and the communication among nodes can be either direct or made via relaying nodes, as in the classical ad-hoc networks. In this paper, the attention is focused mainly on the network layer of VANETs, proposing a novel approach to reduce the interference level during mobile transmission, also considering the minimization of path lengths. We propose an interference aware routing scheme for multi-radio vehicular networks and a new metric is also proposed, based both on the maximization of the average Signal to Interference level and on the minimization of the path length of the connection between source and destination. Our solution has been integrated with the AODV routing protocol to design a new MIMO Distance Vector Protocol. NS-2 has been used for implementing and testing the proposed idea, and significant performance improvements have been obtained.

A scalable framework for in IP-oriented terrestrial-GEO satellite networks

The exponential growth of the Internet, the heterogeneity of networks, and the need for QoS maintenance have urged researchers to develop ideas for managing network scalability and end-to-end QoS assurance. In this article, an IP IntServ architecture in the satellite access network is combined with a scalable IP DiffServ-like architecture in the terrestrial core network. The proposed architecture aims at guaranteeing fine-grained bandwidth control in the satellite access network and stateless scalability in the core network, by exploiting per-aggregate traffic flow control, typical of the aggregate RSVP protocol, and stateless service assurance, typical of the SCORE approach.

Multicast QoS Core-Based Tree Routing Protocol and Genetic Algorithm Over an HAP-Satellite Architecture

In this paper, a quality-of-service (QoS) multicast routing protocol, i.e., the core-based tree based on heuristic genetic algorithms (GAs), has been implemented and applied over a high-altitude platform (HAP)-satellite platform. The proposed multicast routing algorithm is called the constrained cost-bandwidth-delay GA (CCBD-GA). To achieve a better optimization of the multicast tree cost, a new algorithm called HULK-GA, which is based on the GA and on a proposed broadcast metric, has been developed. Finally, an algorithm called hybrid cost-bandwidth-delay GA has been proposed, taking into account both CCDB-GA and HULK-GA characteristics to obtain an overall algorithm that can consider QoS routing constraints and minimize the overall cost per link of the considered multicast tree. The joint bandwidth-delay metrics can be very useful in hybrid platforms such as the platform considered, because it is possible to take advantage of the single characteristics of the satellite and HAP segments. The HAP segment offers low propagation delay, permitting QoS constraints based on maximum end-to-end delay to be met. The satellite segment, instead, offers a larger footprint but higher propagation delay. The joint bandwidth-delay metric permits the traffic load to be balanced, respecting both QoS constraints.

Minimum Hop Count and Load Balancing Metrics Based on Ant Behavior over HAP Mesh

In this paper we propose a routing algorithm based on Swarm Intelligence studies. In particular, this algorithm is based on AntNet routing with the extensions of novel metrics for the multi-objective optimization, that are minimum hop count and traffic load balancing. In order to build an optimal solution, the proposed algorithm will make use of ANT agents that consist of probe packets sent on the HAPs network. We have chosen as reference network a HAPs mesh in order to get advantages of the dynamic characteristics of these platforms. In this work we perform a comparison of a classical shortest length path and our algorithm that will try to find the minimum hop path respecting a maximum end-to-end delay bound and an equally distribution of the traffic on the HAPs network.

Call admission control with statistical multiplexing for aggregate MPEG traffic in a DVB-RCS satellite network

This paper presents a novel call admission control (CAC) algorithm based on the statistical multiplexing of VBR traffic. The proposed algorithm is called statistical multiplexing based on discrete bandwidth levels of GOP rate (SMDB) because the solution is based on the discretisation of the GOP rate in a set of bandwidth levels and on the time characteristics of discrete bandwidth levels of MPEG sources. SMDB is compared with another statistical CAC based on the normal/lognormal distribution of the GOP rate (SMND). SMDB overcomes SMND in many situations such as high variance around the average video traffic GOP rate of sources and heavy traffic load. The new CAC has been tested in the new generation satellite platform called digital video broadcasting via return channel satellite (DVB-RCS). A high system utilization and multiplexing gain respecting QoS constraints is obtained

A distributed hand-over management and pattern prediction algorithm for wireless networks With mobile hosts

In last years, wireless networking is becoming very popular because it is able to satisfy user requests in terms of Quality of Service (QoS); when mobility is present, perhaps, hand-over issues are relevant when hosts change coverage areas during their active sessions. It is very important to mitigate mobility effects, employing an appropriate bandwidth management policy. In our work, we propose two integrated schemes: the first one is based on Markov theory and is aimed at the prediction of mobile hosts movements (in terms of future cells), while the second one is based on statistical theory and is aimed at the minimization of the wasted bandwidth used for passive reservations. So, the proposed Pattern Prediction and Passive Bandwidth Management Algorithm (3P-BMA) is the result of the integration of the Markov predictor and the statistical bandwidth management scheme. 3P-BMA is completely independent on the considered technology, mobility model and vehicular environment. We do not care if the coverage is made by UMTS or WLAN technologies, if hosts are pedestrians or mobile users, etc. Some campaigns of simulation have been led-out in order to confirm the effectiveness of the proposed idea in terms of prediction accuracy, Call Dropping/Blocking probabilities and system utilization.

A Novel Rate Adaptation Scheme for Dynamic Bandwidth Management in Wireless Networks

In the last years, there has been a lot of research and development in wireless networking and mobility management. We focus our attention on the management of real-time flows, in particular on the management of hand-over events, in terms of bandwidth guarantee and service continuity when the system is dealing with Mobility Independent Predictive (MIP) services, defined in Integrated Services (IS) for mobile wireless environment. The main idea of this proposal is the utilization of a pre-reservation phase in the admission control through a Markovian approach, in order to predict the amount of bandwidth needed by a mobile host during its movements among the probably visited cells. The performance evaluation of the proposed idea has been made in terms of total assigned bandwidth, system utilization and admitted/dropped MIP flows.