We shall study message and packet scheduling, as well as network monitoring results production. These two problems are very relevant for achieving high performances and easy of programming in distributed systems.
In particular, we shall propose new models for representing and studying these problems, investigate their computational complexity, propose optimal algorithms and fast sub-optimal heuristics, study the properties of such algorithms and heuristics, and implement them. Specifically:
The tools implemented during the past activity will be used to run real scale experiments.
Our everyday life depends on the correct working of critical distributed systemslike air traffic control, power plant control, but also stock market, government services, just to cite few. At the same time, attacks to such systems are becoming more and more frequent. The problem has been investigated since many years, and has been modelled as Byzantine failures. Many techniques have been proposed for solving such problems. However, such techniques do not take into account the computational effort they require, thus making them unattractive for practical use. In this research, we shall look for new techniques that solve the problem with a certain degree of approximation, but require little computational effort, so to be attractive also for applications require low power consuption, like mobile ad-hoc networks.
On the algorithmic skeleton side, we will analyze common structures of parallel an distributed applications and define a skeleton model starting from these structures. The investigation will move from the analysis of key applications and validate the expressivity of the model against standard benchmark suites. A key point to be addressed will be the definition of skeletons for irregular and dynamic applications, which are crucial distributed and mobile setting. This will involve the definition of suitable execution models for nesting dynamic skeletons and the derivation of reliable approximation of skeleton execution costs. Our investigation will include the derivation of optimized implementation templates for the skeleton proposed and tests on real machines.
The integration of LEO satellite constellations and Internet is a novel and very promising research area. The purpose of using LEO satellites for internet traffic is manyfold: reduce the congestion, improve the quality of service, allow a better connection of mobile users by providing a global planet coverage. Besides, this should be the testbed for interplanetary internet, namely the computer network that in the future will connect all the processing equipment that humans send on planets other than the earth (mars, for instance). This is a novel research area and many problems must be investigated. To cite few, medium access control proper routing and load balancing, congestion control. We shall focus on these problems giving solutions that take into account the special features of LEO satellites: high latency, low communication quality, low on board memory and processing power.
Major issues in mobile, ad hoc networks are how to implement routing in such a dynamic context and how to guarantee consistency, integrity and confidentiality of the global information. Existing solutions for wired networks or personal communication networks can hardly be adapted to these networks due to different constraints/requirements in terms of energy, mobility, memory and processing capacity. Furthermore, a typical problem of ad-hoc networks is the cooperation enforcement in networks of heterogeneous users. One of the most important problems when dealing with mobile terminals is power awareness. Energy conserving habits can suggest to users of multi-hop networks to refrain from forwarding messages toward the final destination. If such a behaviour spreads in the network, no message will be forwarded, and so no communication will take place. The final and fatal consequence of this is network disruption.
The activity in the short term for mobile ad hoc networks can be detailed as follows:
- develop a new routing algorithm for ad hoc networks which exploits a virtual, topology-independent structure of the network to reduce the costs of path setup in the routing algorithm. This algorithm will be compared with the state of the art routing algorithms by means of simulation under different conditions of network load, mobility and density of mobile nodes.
- define models of data distribution in order to provide data availability and confidentiality and recovery algorithms. These models and algorithms should be designed taking into considerations the different characteristics of sensor and mobile networks.
- define models of users behaviour in multihop ad hoc networks with the aim of studying the basic limits of classes of policies implemented with the purpose of forcing users to cooperate in forwarding messages. These models and results can be used to propose and study the performances of new policies, properly designed following the guidelines obtained as above.
Network protocols and data management in wireless sensor networks:
the activity on Sensor networks aims at the integration of database and wireless sensor networks technologies, to let the processing of complex queries in sensor networks, even when the network is disconnected from the sink nodes. This requirement has several implications on the different layers of the sensor network architecture. This activity investigates these implications at different layers: i) at the communication level, addressing routing related problems, ii) at the data-management level, investigating issues related to database technologies and to their adaptability to the management of streams of sensed data, and iii) at a middleware level, by designing a support the data management level compatible with the sensors constraints.
Finally, video transcoding for mobile terminals in cellular networks will be investigated. In particular, we shall concentrate on the problem of avoiding still frames in moving pictures when the communication channel has a dynamic bandwidth. This problem shall arise in next generation cellular systems, like UMTS, which adopts a CDMA channel access protocol, with variable channel bandwidth. Fast processing of frames are in order for avoiding still pictures and guaranteeing acceptable video quality at the same time. Another line of activity will be the investigation of real time video transmission in vehicular networks, namely in networks formed by cars and trucks running on highways and on roads, a particularly hot field in mobile networks.