Erina Ferro

Bluetooth and Wi-Fi wireless protocols: a survey and a comparison

Bluetooth and IEEE 802.11 (Wi-Fi) are two communication protocol standards that define a physical layer and a MAC layer for wireless communications within a short range (from a few meters up to 100 m) with low power consumption (from less than 1 mW up to 100 mW). Bluetooth is oriented to connecting close devices, serving as a substitute for cables, while Wi-Fi is oriented toward computer-to-computer connections, as an extension of or substitution for cabled LANs. In this article we offer an overview of these popular wireless communication standards, comparing their main features and behaviors in terms of various metrics, including capacity, network topology, security, quality of service support, and power consumption.

Static and dynamic resource allocation in a multiservice satellite network with fading

A control architecture for resource allocation in satellite networks is proposed, along with the specification of performance indexes and control strategies. The latter, besides being based on information on traffic statistics and network status, rely upon some knowledge of the fading conditions over the satellite network channels. The resource allocation problem consists of the assignment, by a master station, of a total available bandwidth among traffic earth stations in the presence of different traffic types. Traffic stations are assumed to measure continuously their signal fade level, but this information may either be used only locally or also communicated to the master station. According to the information made available on-line to the master station on the level of the fading attenuation of the traffic stations, the assignment can be made static, based on the a priori knowledge of long-term fading statistics, or dynamic, based on the updated measurements. In any case, the decisions can be adapted to slowly time-varying traffic characteristics. At each earth station, two basic traffic types are assumed to be present, namely guaranteed bandwidth, real time, synchronous data (stream traffic) and best-effort traffic (datagram traffic). Numerical results are provided for a specific architecture in the dynamic case, in a real environment, based on the Italsat satellite national coverage payload characteristics. Copyright

A survey of architectures and scenarios in satellite‐based wireless sensor networks: system design aspects

This paper is not a survey related to generic wireless sensor networks (WSNs), which have been largely treated in a number of survey papers addressing more focused issues; rather, it specifically addresses architectural aspects related to WSNs in some way connected with a satellite link, a topic that presents challenging interworking aspects. The main objective is to provide an overview of the potential role of a satellite segment in future WSNs. In this perspective, requirements of the most meaningful WSN applications have been drawn and matched to characteristics of various satellite/space systems in order to identify suitable integrated configurations. Copyright

The FODA-TDMA satellite access scheme: presentation, study of the system, and results

A description is given of FODA-TDMA (FIFO ordered demand assignment-TDMA), a satellite access scheme designed for mixed traffic (patent N. 9373A/89). The study of the system is presented and the choice of some parameters is justified. A simplified analytic solution is found, describing the steady-state behavior of the system. Some results of the simulation tests for an already existing hardware environment are also presented for channel speeds of 2 and 8 Mb/s, considering both the stationary and the transient cases. The results of experimentation at 2 Mb/s on the EUTELSAT-F2 satellite are also presented and compared with the results of the simulation. >

The PERSONA Service Platform for AAL Spaces

The project PERSONA aims at advancing the paradigm of Ambient Intelligence through the harmonization of Ambient Assisted Living (AAL) Technologies and concepts for the development of sustainable and affordable solutions for the independent living of senior citizens. PERSONA is one of the integrated projects funded by the European Commission within the 6th Framework Program for IST (Information Society Technologies) on AAL for the Aging Society. It involves the participation of 21 partners, from Italy, Spain, Germany, Greece, Norway and Denmark, with a total budget of around 12 million Euros.

Monitoring elderly behavior via indoor position-based stigmergy

In this paper we present a novel approach for monitoring elderly people living alone and independently in their own homes. The proposed system is able to detect behavioral deviations of the routine indoor activities on the basis of a generic indoor localization system and a swarm intelligence method. For this reason, an in-depth study on the error modeling of state-of-the-art indoor localization systems is presented in order to test the proposed system under different conditions in terms of localization error. More specifically, spatiotemporal tracks provided by the indoor localization system are augmented, via marker-based stigmergy, in order to enable their self-organization. This allows a marking structure appearing and staying spontaneously at runtime, when some local dynamism occurs. At a second level of processing, similarity evaluation is performed between stigmergic marks over different time periods in order to assess deviations. The purpose of this approach is to overcome an explicit modeling of users activities and behaviors that is very inefficient to be managed, as it works only if the user does not stray too far from the conditions under which these explicit representations were formulated. The effectiveness of the proposed system has been experimented on real-world scenarios. The paper includes the problem statement and its characterization in the literature, as well as the proposed solving approach and experimental settings.

AAL Middleware Infrastructure for Green Bed Activity Monitoring

This paper describes a service-oriented middleware platform for ambient assisted living and its use in two different bed activity services: bedsore prevention and sleeping monitoring. A detailed description of the middleware platform, its elements and interfaces, as well as a service that is able to classify some typical users positions in the bed is presented. Wireless sensor networks are supposed to be widely deployed in indoor settings and on peoples bodies in tomorrows pervasive computing environments. The key idea of this work is to leverage their presence by collecting the received signal strength measured among fixed general-purpose wireless sensor devices, deployed in the environment, and wearable ones. The RSS measurements are used to classify a set of users positions in the bed, monitoring the activities of the user, and thus supporting the bedsores and the sleep monitoring issues. Moreover, the proposed services are able to decrease the energy consumption by exploiting the context information coming from the proposed middleware.

Long-lived TCP connections via satellite: cross-layer bandwidth allocation, pricing, and adaptive control

The paper focuses on the assignment of a common bandwidth resource to TCP connections over a satellite channel. The connections are grouped according to their source-destination pairs, which correspond to the up- and down-link channels traversed, and each group may experience different fading conditions. By exploiting the tradeoff between bandwidth and channel redundancy (as determined by bit and coding rates) in the maximization of TCP goodput, an overall optimization problem is constructed, which can be solved by numerical techniques. Different relations between goodput maximization and fairness of the allocations are investigated, and a possible pricing scheme is proposed. The allocation strategies are tested and compared in a fading environment, first under static conditions, and then in a real dynamic scenario. The goodput-fairness optimization allows significant gains over bandwidth allocations only aimed at keeping the channel bit error rate below a given threshold in all fading conditions.

Radio resource management across multiple protocol layers in satellite networks: a tutorial overview

Satellite transmissions have an important role in telephone communications, television broadcasting, computer communications, maritime navigation, and military command and control. Moreover, in many situations they may be the only possible communication set-up. Trends in telecommunications indicate that four major growth market/service areas are messaging and navigation services (wireless and satellite), mobility services (wireless and satellite), video delivery services (cable and satellite), and interactive multimedia services (fibre/cable, satellite). When using geostationary satellites (GEO), the long propagation delay may have great impact, given the end-to-end delay users requirements of relevant applications; moreover, atmospheric conditions may seriously affect data transmission. Since satellite bandwidth is a relatively scarce resource compared to the terrestrial one (e.g. in optical transport networks), and the environment is harsher, resource management of the radio segment plays an important role in the systems efficiency and economy. The radio resource management (RMM) entity is responsible for the utilization of the air interface resources, and covers power control, handover, admission control, congestion control, bandwidth allocation, and packet scheduling. RRM functions are crucial for the best possible utilization of the capacity. RRM functions can be implemented in different ways, thus having an impact on the overall system efficiency. This tutorial aims to provide an overview of satellite transmission aspects at various OSI layers, with emphasis on the MAC layer; some cross-layer solutions for bandwidth allocation are also indicated. Far from being an exhaustive survey (mainly due to the extensive nature of the subject), it offers the readers an extensive bibliography, which could be used for further research on specific aspects. Copyright

Practical experiences in interconnecting LANs via satellite

We present an experiment in interconnecting LANs via a satellite link and describe the individual components involved in the experiment. The project was developed in two phases: a) design and realisation of a satellite access scheme that supports real-time and non real-time traffic with a signal fading countermeasure, called FODA/IBEA-TDMA; b) interconnection of LANs where real-time and non real-time applications run. The experiment was presented the first time in June 1994 as a demo in which the Eutelsat satellite was used (in the 12/14 GHz band) to exchange data between two LANs in Pisa and Florence, while video and audio applications running on PCs connected the two sites. The demo was repeated a few weeks later and the Intelsat satellite was used in the 20/30 GHz band.