The recent COVID-19 emergency has pointed out the importance of effective and efficient tools to support users in their day-by-day activities, ranging from health-related ones to studying, remote working and recreation. Indeed, wearables and modern network technologies, such as network slicing and SDWAN, play a key role in this scenario, but existing applications should be rethought to be really useful in critical situations like the current pandemic. In this paper, we reflect about this topic, trying to design an innovative architectural framework where Wearable Expert Systems, IoT and network infrastructures are integrated to obtain the best level of performance.

In this paper, the WEAR-IT framework is presented. It has been developed to provide Android applications with an effective set of primitives to interface with different kinds of wearable devices. The paper presents both architectural and practical features of WEAR-IT, through a case study from the e-Health domain.

In this paper, we consider the problem of modeling application scenarios characterized by variability over time and involving heterogeneous kinds of knowledge. The evolution of distributed technologies creates new and challenging possibilities of creating innovative architectures that integrate different kinds of problem solving methods, obtaining many benefits from the user point of view. In particular, we propose here a multilayer modeling system and adopt the Wearable Expert System concept to tie together statistical and Artificial Intelligence rule-based methods. A music recommendation system applying this model has been implemented as a Cloud Mobile architecture.

Expert Systems design and implementation has been always conceived as a centralized activity, characterized by the relationship between users, domain experts and knowledge engineers. The growing diffusion of sophisticated PDAs and mobile operating systems opens up to new and dynamic application environments and requires to rethink this statement. New frameworks for expert systems design, in particular rule-based systems, should be developed to allow users and domain experts to interact directly, minimizing the role of knowledge engineer and promoting the real-time updating of knowledge bases when needed. This paper present the KAFKA approach to this challenge, based on the implementation of the Knowledge Artifact conceptual model supported by Android OS devices.

Several works have recently appeared in the literature on the design, performance and dimensioning of networks supporting video on demand and multimedia services. It has been shown that performance is strongly dependent on the model adopted to describe the user's behaviour in terms of requests for programs. In this paper we provide a detailed investigation of a non stationary model for the user's request distribution. Numerical results are provided for a network scenario proposed in the literature to investigate the error achieved when the non stationary distribution is approximated with a stationary exponential one.

This paper studies a reference network architecture for video information retrieval, based on hierarchical storage of the video segments and asynchronous transfer mode (ATM) transport capability on the long distance network. The storage associated to local switching nodes can be exploited in two complementary ways, either for caching the most requested video programs, and for decoupling the transmission speed on the long distance network from the natural playout speed of the video segments. We show that both approaches lead to a substantial increase of the load carried on the long distance network with a given service requirement. Moreover, we show that a greater efficiency is obtained when a suitable integration of the two approaches is considered.

This paper is concerned with the ATM traffic characterization within the network. Most of the work performed up to now has studied the effects of traffic on the access multiplexer and the first switch of an ATM network. Various source models were assumed to generate the ATM traffic. So, while the performance of a single switch node has been exhaustively examined, the statistical behavior of the traffic modified as it crosses the network has not been thoroughly analyzed yet. This paper, through an analysis of a network of cascaded queues, indicates that limit distributions exist in the statistical behavior of the traffic streams and in the queue performance, although a formal proof is believed to be very hard to obtain. The first modelling step consists of deriving the exact interdeparture time distribution for the cells of a reference-connection arriving to the output queue of a switch node with a general interarrival time distribution and multiplexed with a background traffic stream. The analysis is iterated through a long sequence of cascaded output queues, until the interdeparture time distribution converges. Simulations show that the analytical results are accurate at each stage of the network under the hypothesis of independent queues, and are also good approximations in the case of correlated queues. This study shows that the queue performance at the limit point is always better than the M/D/1 case. The distributions found in this way depend only on the connection bandwidth and on the background traffic behavior. The initial characteristics of a connection (burst length distributions and burst interarrival time distributions) only influence the convergence speed, not the limit distribution.

Results for nonblocking distribution networks are generalized for the multirate environment in which different user connections share a switch's internal data paths for arbitrary fractions of the total capacity. Conditions under which network proposed by Y.P. Ofman (1965), C.D. Thompson (1978), and N. Pippenger (1973) lead to multirate distribution networks are derived. The results include both rearrangement and wide-sense nonblocking networks. The complexity of the rearrangement multirate network exceeds that of the corresponding space-division network by a log log factor, while the complexity of the wide-sense nonblocking network is within a factor of two of the corresponding space-division network.>

This paper proposes a methodology for performing an evaluation and optimization of the cost of an ATM switching architecture under performance constraints given in terms of virtual connection blocking probability. An analysis of blocking networks is developed, and combined with known results concerning nonblocking networks, provides a theoretical model which relates traffic characteristics, network topology and blocking probability in a multirate/multiservice broadband environment. An analysis of the characteristics determining the cost of a generic ATM switch implementation follows. The model is oriented to optimize both the topological parameters and the speed advantage, with respect to the main cost factors of VLSI-based switching networks i.e., components count and complexity, interconnection costs.>

The authors propose a methodology for performing an evaluation and optimization of the cost of an asynchronous transfer mode (ATM) switching architecture under performance constraints given in terms of virtual connection blocking probability. An analysis of blocking networks is developed and combined with known results concerning nonblocking networks that provide a theoretical model which relates traffic characteristics, network topology, and blocking probability in a multirate/multiservice broadband environment. An analysis of the characteristics determining the cost of a generic ATM switch implementation follows. The model is oriented to optimize both the topological parameters and the speed advantage, with respect to the main cost factors of VLSI-based switching networks.>

A class of rearrangeable interconnection networks which includes the Benes network as a special case is identified. An instance of this class consists of a set of parallel planes each consisting of a Delta network with a suitable number of additional stages. A formal definition is given and a rearrangeability condition is proven which gives a tradeoff between the number of planes and additional stages necessary.>

The problem of arbitrating access to a tree-structured communication channel, with large geographic extent, providing multipoint communication among a set of terminals, is considered. Terminals transmit information in bursts consisting of many packets and compete for the right to transmit bursts. In the simplest case, the channel allows only one terminal to transmit at a time; this can be extended to k concurrent transmitters. Two general approaches are identified. The first is based on the idea of transmit permits or tokens; that is, a terminal must have explicit permission to transmit before starting a burst. The second approach allows terminals to transmit whenever the number of bursts they can observe from their vantage point is less than the limiting number; the network then performs arbitration internally, possibly aborting some bursts in the process, to prevent too many bursts from being active on a link at one time. Several specific access arbitration algorithms based on these approaches are presented and assessed.>

The authors generalize known results for nonblocking distribution networks (also known as generalized connection networks) to the multirate environment, where different user connections share a switch's internal data paths in arbitrary functions of the total capacity. In particular, they derive conditions under which networks due to Y.P. Ofman (1965) and C.D. Thompson (1978), N. Pippenger (1973), and J.S. Turner (1989) lead to nonblocking multirate distribution networks. The results include both rearrangeable and wide-sense nonblocking networks. The complexity of most of our nonblocking multirate networks is roughly twice that of the corresponding space division networks. The one exception has complexity that exceeds that of the corresponding space division network by a log log factor.>

An extension of the classical theory of nonblocking networks is identified and studied that is applicable to multirate circuit and fast packet/ATM switching systems. Conditions are determined under which the Clos, Cantor, and Benes networks are strictly nonblocking. Conditions are also determined under which the Benes network and variants of the Cantor and Clos networks are rearrangeable. It is found that strictly nonblocking operation can be obtained for multirate traffic with essentially the same complexity as in the classical context.>

An extension of the classical theory of connection networks is defined and studied. This extension models systems in which multiple connections of differing data rates share the links within a network. Conditions under which the Clos and Cantor networks are strictly nonblocking for multirate traffic are determined. The authors also determine conditions under which the Benes network and variants of the Cantor and Clos networks are rearrangeable. It is found that strictly nonblocking operation can be obtained for multirate traffic with essentially the same complexity as in the classical context.

The performance of aa delta interconnection network for multiprocessors is evaluated in a circuit switching environment An error is pointed out in previous literature and an exact analytical model is given for regeneration systems, where a connection request is considered lost if not immediately granted. An approximated numerical method is suggested for the correction of the analytical results, which gave outputs in very good agreement with the simulation of real systems where requests are maintained.