Papers by Francesco Potortì

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[R30] Francesco Potortì, Sangjoon Park, Antonio Ramón Jiménez Ruiz, Paolo Barsocchi, Michele Girolami, Antonino Crivello, So Yeon Lee, Jae Hyun Lim, Joaquín Torres-Sospedra, Fernando Seco, Raul Montoliu, Germán Martin Mendoza-Silva, Maria Del Carmen Pérez Rubio, Cristina Losada-Gutiérrez, Felipe Espinosa, and Javier Macias-Guarasa. Comparing the Performance of Indoor Localization Systems through the EvAAL Framework. Sensors, Vol. 17, No. 10, October 2017. [ bib | DOI | email | .pdf ]
In recent years, indoor localization systems have been the object of significant research activity and of growing interest for their great expected social impact and their impressive business potential. Application areas include tracking and navigation, activity monitoring, personalized advertising, Active and Assisted Living (AAL), traceability, Internet of Things (IoT) networks, and Home-land Security. In spite of the numerous research advances and the great industrial interest, no canned solutions have yet been defined. The diversity and heterogeneity of applications, scenarios, sensor and user requirements, make it difficult to create uniform solutions. From that diverse reality, a main problem is derived that consists in the lack of a consensus both in terms of the metrics and the procedures used to measure the performance of the different indoor localization and navigation proposals. This paper introduces the general lines of the EvAAL benchmarking framework, which is aimed at a fair comparison of indoor positioning systems through a challenging competition under complex, realistic conditions. To evaluate the framework capabilities, we show how it was used in the 2016 Indoor Positioning and Indoor Navigation (IPIN) Competition. The 2016 IPIN competition considered three different scenario dimensions, with a variety of use cases: (1) pedestrian versus robotic navigation, (2) smartphones versus custom hardware usage and (3) real-time positioning versus off-line post-processing. A total of four competition tracks were evaluated under the same EvAAL benchmark framework in order to validate its potential to become a standard for evaluating indoor localization solutions. The experience gained during the competition and feedback from track organizers and competitors showed that the EvAAL framework is flexible enough to successfully fit the very different tracks and appears adequate to compare indoor positioning systems.

Keywords: indoor localization; indoor navigation; indoor competition; standard evaluation metrics; benchmarking; performance evaluation; Active and Assisted Living; smartphone sensors; pedestrian dead reckoning
[R29] Francesco Potortì and Filippo Palumbo. CEO: a Context Event Only indoor localization technique for AAL. Journal of Ambient Intelligence and Smart Environments (JAISE), Vol. 7, No. 6, pp. 745--760, November 2015. [ bib | DOI | email | http | .pdf ]
Ambient Assisted Living applications are deployed in smart environments that provide some basic services, a typical example being user localization. AAL applications generally have low accuracy requirements for indoor localization; this opens the opportunity for parasitizing the existing smart environment infrastructure without adding dedicated positioning sensors. In this scenario, one can exploit simple binary sensors that are usually present in the smart environment, such as light and appliance switches or intrusion detection sensors, to obtain a rough estimate of the position of the user. This application is device-free, meaning that the user is not required to carry any device in order to be localized. In this paper we present CEO, a software-only system which we evaluate along the technical guidelines of the EvAAL competition. While the localization performance of CEO is lower with respect to most EvAAL competitors of past editions, it has the benefit of being non-intrusive, easy to install and perfectly compatible with other software systems: these characteristics would made it a potentially significant EvAAL competitor. While developing CEO, we only exploited the definition of the EvAAL competition environment as it was presented to competitors. The only inputs to CEO are the context events generated during the competition, which in 2012 and 2013 were limited to pressing light switches and using a stationary bicycle. We compare the performance of CEO against the results of those editions of EvAAL and show how it can be used to easily improve the performance of any EvAAL competitor.

Keywords: AAL; AmI; indoor localization; tracking
[R28] Paolo Barsocchi, Stefano Chessa, Francesco Furfari, and Francesco Potortì. Evaluating AAL solutions through competitive benchmarking: the localization competition. IEEE Pervasive Computing Magazine, Vol. 12, No. 4, pp. 72--79, October--December 2013. [ bib | DOI | email | .pdf ]
Evaluation of Ambient Assisted Living (AAL) systems is particularly challenging due to the complexity of such systems and to the variety of solutions adopted and services offered. This problem is related to the evaluation of pervasive and ubiquitous systems that has been the focus of many researchers in the recent years and that still awaits for solutions. On the other hand, analyzing and comparing AAL solutions is paramount for the assessment of the research results in this area. EvAAL (Evaluating AAL Systems Through Competitive Benchmarking) is a recently established international competition that aims to address this problem in order to let benchmarking and comparison methodologies of AAL systems emerge from experience. This work describes the first EvAAL competition which was devoted to localization and tracking; proposed evaluation criteria, benchmarks, and achieved results are reported. All evaluation data are freely available from the EvAAL web site.

Keywords: AAL; AmI; indoor localization; tracking
[R27] Anda Guraliuc, Paolo Nepa, Paolo Barsocchi, and Francesco Potortì. Limb movements classification using wearable wireless transceivers. IEEE Transactions on Information Technology in Biomedicine, Vol. 15, No. 3, pp. 474--480, May 2011. [ bib | DOI | .pdf ]
A feasibility study where small wireless transceivers are used to classify some typical limb movements used in physical therapy processes is presented. Wearable wireless low-cost commercial transceivers operating at 2.4 GHz are supposed to be widely deployed in indoor settings and on people's bodies in tomorrow's pervasive computing environments. The key idea of this work is to exploit their presence by collecting the received signal strength measured between those worn by a person. The measurements are used to classify a set of kinesiotherapy activities. The collected data are classified using both Support Vector Machine and K-Nearest Neighbour methods, in order to recognise the different activities.

Keywords: Classification of human limbs activities; K-Nearest Neighbour (K-NN); Received Signal Strength (RSS); Support Vector Machine (SVM); wearable wireless devices
[R26] Paolo Barsocchi, Alan Bertossi, Cristina Pinotti, and Francesco Potortì. Allocating data for broadcasting over wireless channels subject to transmission errors. Wireless Networks, Vol. 16, No. 2, pp. 355--365, February 2010. [ bib | DOI | .pdf ]
Broadcasting is an efficient and scalable way of transmitting data over wireless channels to an unlimited number of clients. In this paper the problem of allocating data to multiple channels is studied, assuming flat data scheduling per channel and the presence of unrecoverable channel transmission errors. The objective is that of minimizing the average expected delay experienced by the clients. Two different channel error models are considered: the Bernoulli model and the simplified Gilbert-Elliot one. In the former model, each packet transmission has the same probability to fail and each transmission error is independent from the others. In the latter one, bursts of erroneous or error-free packet transmissions due to wireless fading channels are modeled. Particular cases are detected where optimal solutions can be found in polynomial time. For general cases, simulations show that good sub-optimal solutions can be found on benchmarks whose item popularities follow Zipf distributions.

Keywords: wireless communication; data broadcasting; multiple channels; flat scheduling; average expected delay; channel transmission errors; Bernoulli model; Gilbert-Elliot model; heuristics
[R25] Raffaello Secchi, Arjuna Sathiaseelan, Francesco Potortì, Alberto Gotta, and Gorry Fairhurst. Using Quick-Start to enhance TCP Friendly Rate Control performance in bidirectional satellite networks. International Journal of Satellite Communications and Networking, Vol. 27, No. 3, pp. 141--161, May--June 2009. [ bib | DOI | .pdf ]
In the not so distant future, we envisage an Internet where the biggest share of capacity is used by streaming applications. To avoid congestion collapse from unresponsive flows, calls for a robust and ubiquitous end-to-end multimedia congestion control mechanism, such as TCP Friendly Rate Control (TFRC) that provides fair sharing with the other Internet traffic. This paper therefore analyses the implications of using rate-adaptive congestion control over satellite links that utilise Demand Allocation Multiple Access (DAMA) to maximise satellite transponder utilisation. The interaction between TFRC with DAMA is explored using simulations supported by fluidic flow models. The analysis shows that DAMA slows-down the start-up phase of TFRC, causing non- negligible delays. To mitigate this problem, we propose a new cross-layer method based on the Quick-Start (QS) mechanism. This can accelerate the start-up of multimedia flows by judicious allocation of additional capacity derived from cross-layer signalling.

Keywords: multimedia; TFRC; satellites; DAMA; Quick Start
[R24] Paolo Barsocchi, Gabriele Oligeri, and Francesco Potortì. Measurement-based frame error model for simulating outdoor Wi-Fi networks. IEEE Transactions on Wireless Communications, Vol. 8, No. 3, pp. 1154--1158, March 2009. [ bib | DOI | .pdf ]
We present a measurement-based model of the frame error process on a Wi-Fi channel in rural environments. Measures are obtained in controlled conditions, and careful statistical analysis is performed on the data, providing information which the network simulation literature is lacking. Results indicate that most network simulators use a frame loss model that can miss important transmission impairments even at a short distance, particularly when considering antenna radiation pattern anisotropy and multi-rate switching.

Keywords: simulation; FER; two-ray; AWGN; fading
[R23] Tomaso de Cola, Luca Ronga, Tommaso Pecorella, Paolo Barsocchi, Stefano Chessa, Erina Ferro, Alberto Gotta, Gabriele Oligeri, Francesco Potortì, Raffaello Secchi, Arjuna Sathiaseelan, Maria Ángeles Vázquez Castro, José Antonio del Peral Rosado, Carlo Caini, and Rosario Firrincieli. Communications and networking over satellites: SatNEx experimental activities and testbeds. International Journal of Satellite Communications and Networking, Vol. 27, No. 1, pp. 1--33, January--February 2009. [ bib | DOI | http | .pdf ]
One of the aims of the SatNEx (Satellite Network of Excellence, http://www.satnex.de) European project is to provide the scientific community that operates on satellite communications with simulation/emulation tools and measurement campaigns, in order to support various research activities that investigate problems in satellite communications at different levels of the OSI stack. In fact, the research activities developed in SatNEx address the most relevant aspects of satellite communications, such as channel modulation and coding schemes, access strategies, advanced networking, end-to-end quality of service, transport performance, delay tolerant networks, and new applications. Even if SatNEx is mainly devoted to satellite communications, integration of satellite and terrestrial wireless segments has also been taken into account. This paper presents the results obtained in a specific joint activity relevant to those trials and testbeds developed during the project. The high number of authors of this paper is an indication of the strong collaborative work sustained, the large measurement campaigns, and the complexity in setting up some tests.

Keywords: satellite communications; testbeds; measurement tools; performance evaluation
[R22] Dragan Savić, Francesco Potortì, Francesco Furfari, Matevž Pustišek, Sašo Tomažič, and Janez Bešter. CostGlue: simulation data exchange in telecommunications. SIMULATION: Transactions of The Society for Modeling and Simulation International, Vol. 84, No. 4, pp. 157--168, April 2008. [ bib | DOI | http | .pdf ]
Exchanging simulation data among simulation practitioners is, to a great extent, hindered by the use of different kinds of data formats in simulation software packages. The purpose of the CostGlue project is to facilitate the exchange of simulation data in the field of telecommunications. We propose a common data interchange format and a data exchange model for raw simulation data, metadata and post-processing data. Based on this model, we additionally propose a framework, CostGlue, designed for packaging simulation output data into the common interchange format, launching post-processing plugins and exporting data into input formats for various third party tools. As a proof of concept we have implemented the framework as a software package and released it as free software.

Keywords: simulation, measurements; data; archiving; HDF
[R21] Carlo Caini, Rosario Firrincieli, Mario Marchese, Tomaso de Cola, Michele Luglio, Cesare Roseti, Nedo Celandroni, and Francesco Potortì. Transport layer protocols and architectures for satellite networks. International Journal of Satellite Communications and Networking, Vol. 25, No. 1, pp. 1--26, January--February 2007. [ bib | DOI | http | .pdf ]
Designing efficient transmission mechanisms for advanced satellite networks is a demanding task, requiring the definition and the implementation of protocols and architectures well suited to this challenging environment. In particular, transport protocols performance over satellite networks is impaired by the characteristics of the satellite radio link, specifically by the long propagation delay and the possible presence of segment losses due to physical channel errors. The level of impact on performance depends upon the link design (type of constellation, link margin, coding and modulation) and operational conditions (link obstructions, terminal mobility, weather conditions, etc.). To address these critical aspects a number of possible solutions have been presented in the literature, ranging from limited modifications of standard protocols (e.g. TCP, transmission control protocol) to completely alternative protocol and network architectures. However, despite the great number of different proposals (or perhaps also because of it), the general framework appears quite fragmented and there is a compelling need of an integration of the research competences and efforts. This is actually the intent of the transport protocols research line within the European SatNEx (Satellite Network of Excellence) project. Stemming from the authors' work on this project, this paper aims to provide the reader with an updated overview of all the possible approaches that can be pursued to overcome the limitations of current transport protocols and architectures, when applied to satellite communications. In the paper the possible solutions are classified in the following categories: optimization of TCP interactions with lower layers, TCP enhancements, performance enhancement proxies (PEP) and delay tolerant networks (DTN). Advantages and disadvantages of the different approaches, as well as their interactions, are investigated and discussed, taking into account performance improvement, complexity, and compliance to the standard semantics. From this analysis, it emerges that DTN architectures could integrate some of the most efficient solutions from the other categories, by inserting them in a new rigorous framework. These innovative architectures therefore may represent a promising solution for solving some of the important problems posed at the transport layer by satellite networks, at least in a medium-to-long term perspective.

Keywords: transport protocols; TCP; satellite networks; PEP; DTN
[R20] Erina Ferro and Francesco Potortì. Bluetooth and Wi-Fi wireless protocols: a survey and a comparison. IEEE Wireless Communications, Vol. 12, No. 1, pp. 12--26, February 2005. [ bib | DOI | .pdf ]
Bluetooth and IEEE 802.11 (Wi-Fi) are two communication protocol standards which define a physical layer and a MAC layer for wireless communications within a short range (from a few meters up to 100 meters) 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 towards computer-to-computer connections, as an extension of or substitution for cabled LANs. In this paper 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.

Keywords: Bluetooth; Wi-Fi; 802.11; comparison; tutorial
[R19] Nedo Celandroni and Francesco Potortì. Maximising single connection TCP goodput by trading bandwidth for BER. International Journal of Communication Systems, Vol. 16, No. 1, pp. 63--79, February 2003. Special issue on wireless access to the global internet: mobile radio networks and satellite systems. [ bib | DOI | .ps.gz | .pdf ]
All other conditions being equal, the end-to-end throughput of a TCP connection depends on the packet loss rate at the IP level. This is an issue when IP runs on a wireless link, where the bit error rate is variable and typically much higher than it is on fixed links. Especially on physical links where the bandwidth delay product is high, TCP performance is significantly impaired by apparently low values of the bit error rate. Generally speaking, on a wireless link bandwidth can be traded for information quality (error rate), the simplest method being to change the type or parameters of forward error correction. On this basis, we show a general method of taking advantage of this trade-off in order to maximize the throughput of a TCP connection.

Keywords: wireless; TCP; FEC; BER; packet loss; throughput; goodput
[R18] Laurent Franck and Francesco Potortì. GaliLEO: a simulation tool for LEO satellite constellations. SIMULATION: Transactions of The Society for Modeling and Simulation International, Vol. 78, No. 9, pp. 543--551, September 2002. [ bib | http | .pdf ]
We present GaliLEO, a simulator for the transmission of connection-oriented traffic over a constellation of LEO/MEO (Low / Medium Earth Orbit) satellites. Its scope is limited to the satellites and the stations accessing them, without any modelling of the terrestrial network, but inside this scope the goal is to study the performance of satellite-based communication networks from as many as possible points of view at the network level. Typical applications include simulation of access techniques, routing policies, fault management. The simulator is written in Java, and it makes use of dynamic loading to easily integrate user-written modules. A draft manual is available, and a preliminary version of the program has been published at the end of 2000.

Keywords: LEO; simulation; simulator; satellites; java
[R17] Nedo Celandroni, Erina Ferro, and Francesco Potortì. A multi-level satellite channel allocation algorithm for real-time VBR data. International Journal of Satellite Communications, Vol. 20, No. 1, pp. 47--61, January--February 2002. [ bib | DOI | .ps.gz | .pdf ]
Integrated services over a shared satellite channel need a MAC protocol that is able to deal with real-time traffic without substantially affecting the efficiency of the shared medium. Because of its bursty nature, MPEG coded VBR video transmission is one of the most challenging real-time applications. In this paper we analyse the statistical performance of a simple allocation method for VBR traffic by using an accurate statistical model of an MPEG-2 VBR coded movie, which exhibits a peak to mean ratio of about 4. The results were obtained both analytically and by simulation, and show that our method is suitable for transmitting non-interactive video and best-effort traffic on the same satellite link.

Keywords: satellite; VBR; MPEG-2; bursty traffic; packet delay; channel efficiency; allocation levels
[R16] Enrico Gregori, Riccardo Marcantonio, and Francesco Potortì. GSn: a new service type for integrated services on the Internet. European Transactions on Telecommunications, Vol. 12, No. 1, pp. 3--12, January--February 2001. [ bib | .ps.gz | .pdf ]
Network services with deterministic guarantees are based on a worst-case description of user-generated traffic. When designing a policing and scheduling algorithm for guaranteed services on the Internet, accuracy of description of the traffic profile has to be traded with simplicity of implementation. The result of this trade off is often expressed as the number of token buckets required by the service along with the choice of their parameters. The GS type of service proposed by the IETF uses two token buckets both for characterizing the traffic and for policing it. The choice of using only two token buckets is primarily driven by policing costs. In this paper we propose a method that allows the number of token buckets used for characterizing the traffic to be greater than what is actually needed to police it. This means we can obtain an accurate profile of the traffic while keeping policing simple. The method consists of computing a profile of the traffic which involves a number of token buckets of the order of ten, and then doing the policing using only the first token bucket, plus another one which is chosen depending on the delay requirements of the receivers. This paper shows that with this simple enhancement we obtain a guaranteed service whose performance closely approaches the theoretical limits of services with deterministic guarantees.

Keywords: Internet; integrated services; guaranteed service; GS
[R15] Nedo Celandroni and Francesco Potortì. Fade countermeasure using signal degradation estimation for demand-assignment satellite systems. Journal of Communications and Networks, Vol. 2, No. 3, pp. 230--238, September 2000. [ bib | .ps.gz | .pdf ]
This paper describes a complete fade countermeasure system, designed for thin route user-oriented and fully meshed satellite networks. The signal degradation due to the residual uplink attenuation after up-power control intervention, plus the down-link attenuation, is compensated for by varying the FEC coding and bit rates of the data. Down and up-link signal degradations are evaluated separately: the former by collecting statistics of quantised levels of the demodulated PSK signal, and the latter by using a narrow band signal level estimator. Measurement times are optimised using a model to evaluate the scintillation variance. The performance evaluation of the whole system in the presence of additive white Gaussian noise (AWGN), shows that very small link power margins can be adopted.

Keywords: fade countermeasure; scintillation; FEC; signal quality estimation; power margin
[R14] Nedo Celandroni, Erina Ferro, Francesco Potortì, Antonio Chimienti, and Maurizio Lucenteforte. Dynamic rate shaping on MPEG-2 video streams for bandwidth saving on a faded satellite link. European Transactions on Telecommunications, Vol. 11, No. 4, pp. 363--372, July--August 2000. Special issue on service quality control in multimedia wireless networks. [ bib | .ps.gz | .pdf ]
In a previous work, we studied how to send a video stream over a noisy satellite channel using the scalability features of the MPEG-2 standard. The base and the enhancement flows were sent with different levels of protection (bit and coding rates) in order to deal with the channel degradation. In this paper, we add Dynamic Rate Shaping (DRS), thus obtaining a greater flexibility in the choice of transmission parameters. In fact, it is possible to trim the required bandwidth in continuous mode in the working range, thus saving some bandwidth when keeping the video quality constant during changing fade conditions. The performances of DRS applied to both the non-scalable and the scalable MPEG-2 coded video streams are shown separately. An application of the techniques presented is discussed, and some criteria are given for choosing the most suitable parameters, according to the service quality requirements.

Keywords: VBR; DSR; MPEG; scalability; layers; fading; satellites; noisy link; errors; video quality
[R13] Nedo Celandroni, Erina Ferro, Francesco Potortì, Antonio Chimienti, Maurizio Lucenteforte, and Romualdo Picco. MPEG-2 coded video traces transmitted over a satellite link: scalable and non-scalable solutions in rain fading conditions. Multimedia Tools and Applications, Vol. 10, No. 1, pp. 73--97, January 2000. [ bib | .ps.gz | .pdf ]
The literature is poor in the analyses of the effects produced by corrupted bits in compressed video bitstreams. This paper presents the results of a transmission experiment of MPEG-2 coded video data over a satellite link affected by noise, in order to investigate under which conditions this type of transmission is economically feasible. The signal-to-noise ratio scalability feature of the MPEG-2 encoder was used to produce different bitstreams of the same movie sequence. The scope of the study was to verify which are the best combinations of video and channel codings in the presence of attenuation on the satellite link, in order to optimize the bandwidth utilisation for a requested image quality. The results obtained give indications about the data channel codings to be used to counter the rain fade on the transmission link, which is a non negligible problem especially when satellite transmissions are in the Ka band. Moreover, the results highlight the flexibility of the scalable video coding in the examined scenario.

Keywords: MPEG video; scalability; quality factor; satellite; fading
[R12] Nedo Celandroni, Erina Ferro, and Francesco Potortì. A simulation tool to validate and compare satellite TDMA access schemes. Telecommunication Systems, Vol. 12, No. 1, pp. 21--37, 1999. [ bib | .ps.gz | .pdf ]
This paper proposes an architecture design for a tool suitable for emulating DA-TDMA (demand-assignment-time division multiple access) satellite access schemes. The tool presented, named FRACAS (for FRAmed Channel Access Simulator) , is particularly suitable for comparing the performance of different satellite channel allocation policies. Using Fracas, a service provider can choose from different policies for sharing a satellite channel among a number of users. Some allocation policies, selected from those available in the literature, are built-in, while others can be designed from scratch and added without much effort. The parameters of the built-in allocation policies can easily be changed in order to exploit the full potential of the allocation schemes. Fracas' features permit the optimisation of satellite resource usage in accordance with the traffic pattern supported. Fracas enables research teams and students to explore and compare different multiple access schemes, and to develop simulation runs for various kinds of service-induced traffic, including aggregate traffic, which is typical in a local area network (LAN) interconnection environment.

Keywords: emulator; simulator; satellite access schemes; performance comparison; TDMA; aggregate traffic
[R11] Nedo Celandroni and Francesco Potortì. Modeling Ka band scintillation as a fractal process. IEEE Journal on Selected Areas in Communications, Vol. 17, No. 2, pp. 164--172, February 1999. Direct-to-user satellite systems and technologies at Ka band and beyond. [ bib | .ps.gz | .pdf ]
We propose a model that describes the signal fading process due to scintillation in the presence of rain. We analyzed a data set of up-link (30 GHz) and down-link (20 GHz) attenuation values averaged over 1 second intervals. The data are samples relative to 10 significant events, for a total of 180,000 s, recorded at the Spino d'Adda (North of Italy) station using the Olympus satellite. Our analysis is based on the fact that the plot of attenuation versus time recalls the behaviour of a self-similar process. We then make various considerations and propose a fractional Brownian motion model for the scintillation process. We describe the model in detail, with pictures showing the apparent self-similarity of the measured data. We then show that the Hurst parameter of the process is a simple function of the rain fade. We describe a method for producing random data that interpolate the measured samples, while preserving some of their interesting statistical properties. This method can be used for simulating fade countermeasure systems. As a possible application of the model, we show how to optimise fade measurement times for fade countermeasure systems.

Keywords: scintillation; rain fade; fractal model; signal degradation; fade countermeasures
[R10] Nedo Celandroni, Marco Conti, Erina Ferro, Enrico Gregori, and Francesco Potortì. A bandwidth assignment algorithm on a satellite channel for VBR traffic. International Journal of Satellite Communications, Vol. 15, No. 6, pp. 237--246, November--December 1997. [ bib | DOI | .ps.gz | .pdf ]
Variable Bit Rate (VBR) video is currently by far the most interesting and challenging real-time application. A VBR encoder attempts to keep the quality of video output constant, and at the same time reduces bandwidth requirements since only a minimum amount of information has to be transferred. On the other hand, as VBR video traffic is both highly variable and delay sensitive, high-speed networks (e.g. ATM) are generally implemented by assigning peak rate bandwidths to VBR video applications. This approach may however be inefficient in a satellite network based on a TDMA scheme. To overcome this problem, we have designed a demand-assignment satellite bandwidth allocation algorithm in TDMA, named V2L-DA (VBR 2 Level-Demand Assignment), which manages the VBR video traffic according to a dynamic bandwidth allocation algorithm. In this paper we discuss how to tune the proposed algorithm in order to optimise network utilisation when MPEG-1 VBR video traffic is being transmitted. Our results indicate that most of the time only 40% of the peak rate bandwidth is needed to satisfy the VBR source, and the remaining 60% of the peak rate bandwidth can be used to transmit the datagram traffic queued in the network stations.

Keywords: satellite; TDMA assignment; real-time traffic; non real-time traffic; VBR traffic; MPEG coding; traffic model
[R09] Nedo Celandroni, Erina Ferro, and Francesco Potortì. DRIFS-TDMA: a proposal for satellite access distributed-control algorithm for multimedia traffic in a faded environment. International Journal of Satellite Communications, Vol. 15, No. 5, pp. 227--235, September--October 1997. [ bib | DOI | .ps.gz | .pdf ]
Most demand assignment TDMA satellite access protocols use centralised-control access schemes rather than distributed ones because their simplicity and robustness usually compensate for the longer allocation delay. Starting from the FODA/IBEA centralised-control protocol, we studied two distributed-control protocols, named DRIFS and FEEDERS respectively, for accessing a geostationary satellite channel. Multimedia traffic and faded environments were considered in the study of both the access schemes. This paper presents the DRIFS proposal, together with the recovery procedures from critical events, whose handling is central to the discussion of a distributed satellite access protocol. Probabilities of such events are also estimated. Reference [R08] presents the FEEDERS proposal, while in [R03] the reader can find the results of a comparison between the two schemes obtained by means of simulation.

Keywords: satellite access scheme; distributed control; capacity allocation on demand; fading; multimedia traffic
[R08] Nedo Celandroni, Erina Ferro, and Francesco Potortì. FEEDERS-TDMA: a distributed-control algorithm for satellite channel capacity assignment in a mixed traffic and faded environment. International Journal of Satellite Communications, Vol. 15, No. 4, pp. 185--195, July--August 1997. [ bib | DOI | .ps.gz | .pdf ]
This paper presents FEEDERS , an access scheme for sharing, in TDMA mode, the capacity of a satellite channel among a number of stations, on the basis of user demand. This scheme and its companion, DRIFS [R09], result from a study carried out by the authors on distributed- control protocols for geostationary satellite access. Both protocols derive from the FODA/IBEA centralised-control system and have the same features. The distributed technique to compute the capacity allocation adopted by FEEDERS improves some performance in FODA/IBEA, but raises a problem about system stability. Techniques to solve this problem are presented, together with system performance. A comparison is also made with the FODA/IBEA system, though a more detailed comparison can be found in [R03], where DRIFS, FEEDERS and FODA/IBEA systems are all compared.

Keywords: satellite access scheme; distributed control; capacity allocation on demand; fading; isochronous traffic; anisochronous traffic
[R07] Nedo Celandroni, Erina Ferro, Francesco Potortì, and Gérard Maral. Delay analysis for interlan traffic using two suitable TDMA satellite access schemes. International Journal of Satellite Communications, Vol. 15, No. 4, pp. 141--153, July--August 1997. [ bib | DOI | .ps.gz | .pdf ]
Two demand assignment TDMA satellite access schemes that are suitable for providing flexible interconnections of local area networks are compared by means of simulation: FODA/IBEA and CFRA. A unique simulation tool was used, a meshed network of VSATs under the control of a master station was considered and similar networking conditions were applied to both access schemes. The generated traffic had two components having different level of burstiness: bulk traffic and interactive traffic. The performance evaluated is the delay for each traffic component. We show that CFRA is best when connecting clusters of only a few stations and even individual ones exchanging light traffic. FODA/IBEA, on the other hand, is better suited to interconnect networks, or within networks with many hosts, where heavy traffic is more likely.

Keywords: satellite; TDMA access schemes; comparison; bursty traffic; demand assignment; simulation
[R06] Nedo Celandroni, Erina Ferro, and Francesco Potortì. Quality estimation of PSK modulated signals. IEEE Communications Magazine, pp. 50--55, July 1997. Special issue on Broadband via satellite. [ bib | .ps.gz | .pdf ]
A very important problem in fade countermeasure systems is the need to detect signal quality quickly and accurately. In fact, the countermeasure has to be initiated before the signal degradation effect on the bit error rate is detected by the user. This paper presents an overview of different methods to evaluate signal quality, which are based on the availability of soft quantized levels of PSK demodulated signals at the receiver. It is shown that this class of methods has a good theoretical performance. Also, an innovative procedure is presented which adapts one of the methods to some existing hardware, and tunes-up a set of parameters in order to compensate to the fact that the hardware is to some extent impaired.

Keywords: soft quantisation; fade estimation; channel quality; satellite communications; viterbi decoder
[R05] Nedo Celandroni, Erina Ferro, and Francesco Potortì. A traffic generator for testing communication systems: presentation, implementation and performance. Real-Time Systems, Vol. 13, No. 1, pp. 50--55, July 1997. [ bib | .ps.gz | .pdf ]
This paper presents a multi-application traffic generator (MTG), aimed at the generation of packets over a LAN. The generated traffic simulates the one produced by a number of both isochronous and anisochronous applications, thus allowing the measurement of a number of parameters relevant to the communication network. From a test point of view, data generated by the MTG system is equivalent to data generated by real applications spread over a LAN. The MTG system is presented, its implementation is described, some figures relevant to the MTG performance are shown, and the statistical analysis which can be performed on the recorded data is briefly introduced.

Keywords: traffic generator; ethernet; unix; LAN
[R04] Nedo Celandroni, Erina Ferro, and Francesco Potortì. Experimental results of a demand-assignment thin route TDMA system. International Journal of Satellite Communications, Vol. 14, No. 2, pp. 113--126, March--April 1996. [ bib | DOI | .ps.gz | .pdf ]
This paper presents the experimental results measured on the Italsat satellite when data is transmitted by using the FODA/IBEA satellite access scheme. The measures presented refer to the packet arrival time jitter, which affects the real-time data, and to the end-to-end delay of the non real-time data. The experimental results, obtained with four Italian active stations on Italsat confirm the analytical results. The paper also shows the advantage of working in pre-assignment mode, a feature of the capacity assignment algorithm which improves the end-to-end delay of non real-time data during the transient provoked by a traffic step when the system is scarcely loaded.

Keywords: thin route TDMA; real-time data; capacity assignment on demand; jitter; leaky bucket; non-real-time data; end-to-end delay; pre-assignment mode; transient traffic, stationary traffic
[R03] Nedo Celandroni, Erina Ferro, and Francesco Potortì. Comparison between distributed and centralised demand assignment TDMA satellite access schemes. International Journal of Satellite Communications, Vol. 14, No. 2, pp. 95--111, March--April 1996. [ bib | DOI | .ps.gz | .pdf ]
This paper presents the performance measurements from a comparison between FODA/IBEA and two other satellite access schemes, FEEDERS and DRIFS. The three schemes differ in terms of the scheduling of the channel capacity: i.e. centralised control in FODA/IBEA and distributed in the other two. All these access schemes were designed at CNUCE, where the simulation tool used for the comparison was also developed. FODA/IBEA was developed and tested on several satellites (Olympus, Eutelsat and Italsat), and used in a project of LAN interconnection. The two distributed control access schemes have been studied and simulated to analyse the behaviour of the capacity assignment algorithm, while the recovery procedures needed for the network stability are presented in [R08] and [R09]. All the access schemes support an aggregated traffic, and the quality of the data transmission is guaranteed even when the transmitting signal experiences a severe attenuation due to bad atmospheric conditions.

Keywords: satellite; TDMA access schemes; distributed control; centralised control; comparison; aggregated traffic; traffic generatorts; fade countermeasure
[R02] Nedo Celandroni, Erina Ferro, Francesco Potortì, Alessandro Bellini, and Gianfranco Pirri. Practical experiences in interconnecting LANs via satellite. ACM Computer Communication Review, Vol. 25, No. 5, pp. 56--58, October 1995. [ bib | .pdf ]
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 1 ; 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.

Keywords: satellite; TDMA fade countermeasure; satellite LAN interconnection; satellite videoconference
[R01] Nedo Celandroni, Erina Ferro, Nick James, and Francesco Potortì. FODA/IBEA-TDMA: a flexible fade countermeasure system for integrated services in user oriented networks. International Journal of Satellite Communications, Vol. 10, pp. 309--323, December 1992. [ bib | .ps.gz | .pdf ]
A flexible, processor based, TDMA station has been implemented. This station and its associated variable data rate modem enables users to implement very complex frame structures under software control. Burst rates of 512 Kbit/s - 8.192 Mbit/s and different coding rates are possible allowing the transmitted bit energy from each station in the network to be adapted to prevailing conditions. The proposed application of the station is the transmission of mixed stream and packet traffic, in a LANs interconnection via satellite environment, using a modification of the FODA 5 technique. The association of the up-link power control feature with the bit and coding rate variation gives the system an interesting ability to cope with fade conditions. The link outage probability is investigated for the Olympus transponder in Ka band. The ability of the system, together with the good performance of Olympus, shows that the Ka band is usable for the above mentioned types of networks without prohibitive fade degradation, at least for limited coverages.

Keywords: TDMA controller; variable bit rate modem; fade countermeasure; outage; multiple access; satellite network
[M04] Francesco Potortì. EvAAL evaluation workshop. Ercim News, No. 95, p. 54, October 2013. Not peer reviewed. [ bib | email | .pdf ]
For the third consecutive year, the EvAAL competition gathered teams from all around the world to compare their systems in the participating living labs. EvAAL, a project embedded into the AALOA association, was led by the Institute of Information and Technologies (ISTI) of CNR (Pisa, IT) and was mostly financed by the universAAL FP7 project.

Keywords: AAL, ambient assisted living, benchmark, competition, contest, localization
[M03] Sten Hanke, Thomas Karopka, Francesco Furfari, and Francesco Potortì. To build up an ambient assisted living open association (AALOA). proceedings of the AAL summit, pp. --, June 2012. Extended abstract. [ bib | email | .pdf ]
One problem which slows down the creation of the AAL market is fragmentation of research efforts and the lack of a standardised approach for developers. To address this, we founded the AALOA (AAL Open Association). The vision of AALOA is to create a ecosystem for the domain of assistive technology for independent living. Community building activities as well as the hosting of AAL related projects like EvAAL and several open source software projects1 has been used to attract different stakeholders of the AAL community. Two main initiatives for the AALOA community building and promotion of the idea among all stakeholder groups has been brought forth so far. The AMB11 workshop, organised together with the eInclusion unit of the EC and the Lecce Declaration, which gained support from 44 projects mostly at the EU level.

Keywords: AAL, open source, community building
[M02] Thomas Karopka, Francesco Potortì, and Sten Hanke. Open Minds. PS public service review, No. 31, 2012. Not peer reviewed. [ bib | email | http | .pdf ]
Healthy and active ageing is one of the main challenges for most industrialised nations and a key issue on Europe's agenda for the period 2014-2020. The number of people aged 60 and over in the EU is now rising by more than two million every year. This raises the question of how to transform this challenge to our societies into a driver of economy and create a win-win situation? One of the envisioned solutions is the application of assistive technology combined with newly created services to allow people to live an independent life for as long as possible. Research in this area involves many ICT related R&D disciplines and has attracted much attention in the last couple of years. Several initiatives have emerged to tackle the challenges involved, and significant incremental progress has been made on many fronts. But a major breakthrough, leading to a standardised approach and thereby to widespread adoption, is still not in sight. One of the main problems from the technological point of view is fragmentation. The mission of AALOA, the Ambient Assisted Living Open Association, is to address this situation by bringing together the resources, tools and people involved in Ambient Asssisted Living (AAL) in a single forum that makes it much easier to reach conclusions on provisions needed to achieve progress. A concrete technical objective is to promote a common platform or middleware that is distributed as open source software.

Keywords: AAL, ambient assisted living, community building, open source
[M01] Stefano Chessa, Francesco Furfari, and Francesco Potortì. EvAAL: evaluating AAL systems through competitive benchmarking. Ercim News, No. 84, p. 46, October 2011. Not peer reviewed. [ bib | email | .pdf ]
Owing to the complexity of Ambient Assisted Living (AAL) systems and platforms, the evaluation of AAL solutions is a complex task that will challenge researchers for years to come. However, the analysis and comparison of proposed solutions is paramount to enable us to assess research results in this area. We have thus organized an international contest called EvAAL: Evaluating AAL Systems Through Competitive Benchmarking. Its aims are to raise interest within the research and developer communities in the multidisciplinary research fields enabling AAL, and to create benchmarks for the evaluation and comparison of AAL systems.

Keywords: AAL, ambient assisted living, benchmark, competition, contest, localization
[L09] Paolo Barsocchi and Francesco Potortì. Wearable sensors, Chap. 6.4. Localization in body area networks, pp. 493--516. Academic Press, Elsevier, August 2014. [ bib | email | http ]
This chapter highlights the importance of localization in relation to on-body area networks and gives a broad overview of localization methods and technologies. Most of the material is relative to indoor localization, because that is where body-area networks are mostly relevant. The chapter provides an overview on criteria used to evaluate the performance of localization system, followed by an overview of technologies used for different types of sensors and general ways to fuse data generated by sensors. Since we envision a future where the presence of small devices communicating via packet radio is ubiquitous in most indoor and some outdoor environments, the rest of the chapter concentrates on methods and algorithms used in the context of wearable radios, most of which are based on the RSS (received signal strength) indicator available on packet radio devices.

[L08] Francesco Furfari, Francesco Potortì, Stefano Chessa, M.-R. Tazari, Michael Hellenschmidt, R. Wichert, Joe Gorman, and Antonio Kung. Platforms for AAL Applications, Chap. 7. The AAL Open Association Manifesto, pp. 190--194. Vol. 6446 of Lecture Notes in Computer Science, SpringerLink, 2010. [ bib | DOI | email | http ]
AAL (Ambient Assisted Living) has great potential for positively influencing the lives of many people. But impact so far has been less than hoped, partly due to fragmentation of research efforts and the lack of a standardised approach for developers. To address this, we are forming the AALOA (AAL Open Association), and invite you to join in our efforts.

Keywords: AmI; AAL; Platform; OSGi; URC; Smart Homes; Healthcare; Software Platform; Open Source Policies; Standards; reference platform; standardization; Platform; Application; Policies; Universal Remote Console (URC); Web Service Description Language (WSDL); personal user interface; pluggable user interface; OpenURC; Alliance; Platform for Accessible User Interfaces; ISO; ICT; e-Inclusion
[L07] Paolo Barsocchi, Alan A. Bertossi, M. Cristina Pinotti, and Francesco Potortì. Handbook of Research on Mobile Multimedia, Chap. XXIX: Quality of service of data broadcasting algorithms on erroneous wireless channels, pp. 421--436. IGI Global -- Information Science Reference, 2 Ed., September 2008. [ bib | http ]
Broadcasting is an efficient and scalable way of transmitting data over wireless channels to an unlimited number of clients. In this chapter the problem of allocating data to multiple channels is studied, assuming flat data scheduling per channel and the presence of unrecoverable channel transmission errors. The behavior of wireless channels is described by the Bernoulli model, in which each packet transmission has the same probability to fail and each transmission error is independent from the others. The objective is that of minimizing the average expected delay experienced by the clients. Optimal solutions can be found in polynomial time when all data items have unit lengths, while heuristics are presented when data items have non-unit lengths. Extensive simulations, performed on benchmarks whose item popularities follow Zipf distributions, show that good sub-optimal solutions are found.

Keywords: broadcast scheduling algorithm; data allocation algorithm; average expected delay; wireless channel; channel error model; heuristics; quality of service
[L06] Dragan Savić, Francesco Potortì, Francesco Furfari, Matevž Pustišek, Sašo Tomažič, and Janez Bešter. 23. Recent advances in modeling and simulation tools for communication networks and services, Chap. A tool for packaging and exchanging simulation results, pp. 443--462. Springer US, November 2007. Proceedings of the final COST 285 symposium. [ bib | DOI | http ]
In the field of simulations storing and exchanging simulation data are important tasks. The quantity of simulation data can be rather big and at the same time this data can appear in different formats. The conversion of big quantities of data can be extremely time-consuming. In this article we focus on simulations in telecommunications. Therefore we have studied the needs of the telecommunication community and defined a reference model of a simulation process. According to the needs we have developed a software tool CostGlue, which represents a central repository for data produced with different types of simulation tools and acts as a converter of different output formats into different input formats. CostGlue has modular software architecture. This enables further development and contributions from any other research sphere of activity. The core of the software tool represents the application CoreGlue responsible for communicating with the database. CoreGlue represents unified interface for writing to the database and reading from it. Specific functions like import and export of data and different mathematical calculations are represented as a set of self-described modules, which are loaded as necessary. The graphic user interface is introduced as a web application for the simplicity of use and effective remote access to the application. The software package CostGlue is going to be released as free software with the possibility of further development.

Keywords: simulation; archiver; converter; HDF
[L05] Nedo Celandroni and Francesco Potortì. Resource management in satellite networks, Chap. 9.3. Cross-layer interaction between TCP and physical layer, pp. 294--298. Springer, 2007. Not peer reviewed. [ bib | http ]
Keywords: TCP; satellite; cross-layer
[L04] Paolo Barsocchi, Alberto Gotta, and Francesco Potortì. Resource management in satellite networks, Chap. 8.5.1. Redundant codes in hybrid networks, pp. 265--267. Springer, 2007. Not peer reviewed. [ bib | http ]
Keywords: TCP; satellite; cross-layer
[L03] Matevž Pustišek, Dragan Savić, and Francesco Potortì. Modeling and simulation tools for emerging telecommunications networks, Chap. 10. Packaging simulation results with CostGlue, pp. 209--222. Kluwer/Springer, September 2006. Proceedings of the mid-term COST 285 symposium. [ bib | http ]
Researchers performing simulations work in the field of computer telecommunications are often faced with the time-consuming task of converting huge quantities of data to and from different formats. We examine some of the requirements of the telecommunications simulation community and propose an architecture for a general purpose archiver and converter for big quantities of simulation data to be released as free software.

Keywords: simulation; archiver; converter; HDF
[L02] Marco Annoni, Simone Bizzarri, Erina Ferro, Laurent Franck, Ioannis Gragopoulos, Evangelos Papapetrou, and Francesco Potortì. Service efficient network interconnection via satellite -- EU COST Action 253, Chap. 5. GaliLEO: a simulation tool for traffic on LEO satellite constellations - presentation of the architecture. Wiley, January 2002. Not peer reviewed. [ bib | .html ]
Complex communication systems where satellite links are involved are difficult to test and tune up without the help of simulation tools. First of all, using satellites is very expensive - the satellite time spent in testing and tuning-up the system must thus be as short as possible. Second, during the performance evaluation in a real environment it is not always possible to find the right amount of traffic, and the most appropriate traffic pattern and data aggregation that will put the system under the maximum amount of stress so that its limits can be validated. When satellite constellations are involved, rather than single satellites, these problems are enormously exacerbated, to the point that in all but very particular cases it is practically impossible for the researcher to do tests on satellite constellations. It is therefore necessary to use some kind of simulation tool. The array of required features for the tool is very broad. The basic feature is that of making it possible to describe the constellation topology, and the position of earth terminals. Satellite may have different capabilities, in term of number and characteristics of intersatellite links, spot topology and behaviour, and on-board processing abilities. Many types of routing algorithms are under study, some of which allow for dynamic rerouting based on nodes' perceived congestion or on quality of service requests. Also, it should be possible to analyse channel allocation algorithms for the up-down links, including frequency reuse algorithms. The traffic generation choice should be broad and easily extensible, allowing for both fine control on single connections and generation of background traffic for loading the satellite network. Finally, a rich set of statistic collection and analysis tools should be available.

Keywords: COST; LEO; satellite; simulation
[L01] Laurent Franck and Francesco Potortì. Modeling and simulation environment for satellite and terrestrial communication networks, Chap. 11. GaliLEO: a simulation tool for LEO satellite constellations. Kluwer, October 2001. Proceedings of the European COST telecommunications symposium -- COST Action 256 -- The Kluwer International series in Engineering and Computer Science: volume 645. [ bib | http ]
We present Galileo, a simulator for the transmission of both connection-oriented and connectionless traffic over a constellation of LEO/MEO (Low / Medium Earth Orbit) satellites. Its scope is limited to the satellites and the stations accessing them, without any modelling of the terrestrial network, but inside this scope the goal is to study the performance of satellite-based communication networks from as many as possible points of view. Typical applications include simulation of access techniques, routing policies, fault management. The simulator is written in Java, and it makes use of dynamic loading to easily integrate user-written modules. A draft manual is available, and a preliminary version of the program will be published by the end of 2000.

Keywords: COST; galileo; satellite; simulation
[C46] Francesco Potortì, Antonino Crivello, and Michele Girolami. Wi-Fi Probes as Digital Crumbs for Crowd Localisation. In: proceedings of the International Conference on Indoor Positioning and Indoor Navigation (IPIN), Madrid, ES, October 2016. In print. [ bib | DOI | email | http | .pdf ]
While indoor localization techniques based on Wi- Fi RSS measurements have been extensively studied, their application to eavesdropping Wi-Fi probe requests sent from mobile devices in large indoor environments, such as shopping malls, is scarce or absent in the literature. The idea behind this work is to observe Wi-Fi enabled smartphones, especially when they are not associated to a network. They periodically perform active network scanning by issuing probe requests, which are detected by networked sniffing devices produced by Cloud4Wi®. We experimentally investigate the opportunities offered by passive gathering of Wi-Fi probes for purposes of crowd positioning in areas of interest. Our preliminary experimental setting convincingly shows that a small number of sniffing devices may be enough for analysing crowd movements in indoor areas.

Keywords: Passive indoor localization; crowd sensing; Wi-Fi probe eavesdropping; Wi-Fi fingerprinting
[C45] Francesco Potortì, Paolo Barsocchi, Michele Girolami, Joaquı́n Torres-Sospedra, and Raúl Montoliu. Evaluating Indoor Localization Solutions in Large Environments Through Competitive Benchmarking: The EvAAL-ETRI Competition. In: proceedings of the International Conference on Indoor Positioning and Indoor Navigation (IPIN), Banff, AB, Canada, October 2015. [ bib | DOI | email | http | .pdf ]
The increasing demand for services and higher comfort levels inside buildings, together with the rise in time spent indoor, ensure an upward trend in indoor localization demand for the future. Evaluation of indoor localization systems is particularly challenging due to the complexity of such systems and to the variety of solutions adopted and services offered. EvAAL is an international competition aimed at evaluating and assessing indoor localization systems. The fifth edition of EvAAL promotes competitions on indoor localization in large environments. This paper describes its technical aspects, the competing systems and the results.

Keywords: device-free localization; indoor localization; RSS localization
[C44] Pietro Cassarà, Francesco Potortì, Paolo Barsocchi, and Michele Girolami. Choosing an RSS Device-Free Localization algorithm for Ambient Assisted Living. In: proceedings of the International Conference on Indoor Positioning and Indoor Navigation (IPIN), Banff, AB, Canada, October 2015. Code available at http://wnet.isti.cnr.it/software/spin. [ bib | DOI | email | http | .pdf ]
Device-free localization algorithms attract, among others, the attention of researchers working in the Ambient Assisted Living (AAL) scenarios, where the target user might not be able or willing to wear any devices. We concentrate on systems that exploit the Received Signal Strength indicator coming from wireless devices whose position is known, called anchors. In this paper we select and test the main device-free localization solutions and experimentally compare their performance using a smaller number of anchors than commonly found in the literature. We illustrate the procedure used to validate our comparing procedure and we give suggestions on usability in the application scenarios typical of AAL.

Keywords: device-free localization; indoor localization; RSS localization
[C43] Pietro Cassarà, Francesco Potortì, Paolo Barsocchi, Michele Girolami, and Paolo Nepa. Lessons Learned on Device Free Localization with Single and Multi Channel Mode. In: proceedings of the International Conference on Indoor Positioning and Indoor Navigation (IPIN), Banff, AB, Canada, October 2015. [ bib | DOI | email | http | .pdf ]
In this paper we concentrate on device-free RSS-based indoor localization methods, which have been the subject of intensive studies in the last few years. Specifically, the purpose of this paper is to assess the performance improvements of a Variance-based Radio Tomographic Imaging (VRTI) technique, when scanning various radio channels. We compare the performance of such technique compared with a VRTI configured with only single channel, the latter being the minimum introduced interference option. Moreover, in this paper we discuss in which application scenarios the multi-channel scanning technique is usable and appropriate. We describe how we configure the measurements campaigns to gather RSS values as well two indicative performance metrics, namely the mean square error and percentiles of the error distribution.

Keywords: device-free localization; indoor localization; RSS localization
[C42] Paolo Barsocchi, Erina Ferro, Filippo Palumbo, and Francesco Potortì. Smart meter led probe for real-time appliance load monitoring. In: IEEE, Ed., proceedings of IEEE Sensors, pp. 1451--1454, Piscataway, USA, November 2014. [ bib | DOI | email | http | .pdf ]
Non-intrusive load monitoring of domestic appliances has received steady interest in the last twenty years, first because of interest from energy companies interested in usage statistics for power balancing and, more recently, in order to assist users in tuning their habits for reduced power consumption. We discuss how this concept can be used in real-time with a cheap, easy-to-install device based on Arduino to monitor the usage of domestic appliances and thus the activities of persons inside their home. The device is presented, complete with free software and hardware, and a proof-of-concept web-based user interface is depicted that is able to discriminate very simple activities.

Keywords: Arduino; energy meter; NIALM; AIDL; appliance usage detection
[C41] Pietro Cassarà, Francesco Potortì, Paolo Barsocchi, and Paolo Nepa. Single-channel versus multi-channel scanning in device-free indoor radio localization. October 2013. Oral presentation, proceedings not published. [ bib | email ]
Keywords: device-free localization; indoor localization; RSS localization
[C40] Sten Hanke, Francesco Furfari, Juan Pablo Lázaro Ramos, and Francesco Potortì. The AALOA exploitation model for AAL project results. In: Erika Pohjanen, Ed., proceedings of AAL Forum, pp. 335--339, New Tools for Health, Norrköping (SE), September 2013. [ bib | email | http | .pdf ]
AALOA, the Ambient Assisted Living Open source Association, was born to create an environment to foster initiatives linked to AAL. AALOA offers an environment where people and organizations can start an AAL project. Most projects are expected to be software projects, to be released using a Free / Libre / Opens Source software licence, but other types of activities, like research, conference organization, standardization and lobbying are envisioned as well. This paper illustrates the idea of the Ambient Assisted Living Open Association, the actions initiated by AALOA and those planned for the future. The main focus is on the exploitation possibilities which AALOA provides to the outcome of several European and non-European projects. A collaboration here would be a win-win situation. On one side, AALOA has already appropriate prominence and is linked to European strategies which can help to group people and associations around different project results and to position them in the right way and manner. On the other side AALOA is depending on the community and on the projects it hosts. To demonstrate this ambition and to give a demonstration for other European projects, the paper presents the identified exploitable results of the universAAL FP7 project and their planned incubation in AALOA.

Keywords: AAL; open source; community building
[C39] Paolo Barsocchi, Francesco Potortì, and Paolo Nepa. Device-free indoor localization for AAL applications. In: Balwant Godara and Konstantina S. Nikita, Eds., proceedings of the International Workshop on Advances in Wireless Physical Layer Communications for Emerging Healthcare Applications (IWAWPLC), pp. 361--368, Springer, Paris (FR), November 2012. In: Wireless Mobile Communication and Healthcare. [ bib | DOI | email | .pdf ]
We present a device-free localization method oriented to Ambient Assisted Living applications. The system exploits the received signal strength (RSS) measured by fixed wireless communications devices, whose position is known a priori, in order to localize a person in the transmission coverage area. The proposed localization system is passive, by not requiring the user to wear anything, and is able to trade complexity for accuracy by simply changing the number of deployed devices. The presentation is validated by an indoor experimental study.

Keywords: RSS-based localization; AAL; tracking
[C38] Paolo Barsocchi, Francesco Potortì, Francesco Furfari, and Alejandro M. Medrano Gil. Comparing AAL indoor localization systems - indoor localization and tracking. In: Stefano Chessa and Stefan Knauth, Eds., Evaluating AAL systems through competitive benchmarking, pp. 1--13, Springer, Lecce (IT), 2012. [ bib | DOI | email | .pdf ]
EvAAL (Evaluating AAL Systems Through Competitive Benchmarking) is an international competition aimed at the evaluation and assessment of Ambient Assisted Living systems components, services and platforms. In 2011 took place the first edition of EvAAL on the special theme of Indoor Localization and Tracking for AAL. This paper describes the technical aspects of the first edition of EvAAL and draws a roadmap for the future editions.

Keywords: AAL; localization; tracking
[C37] Stefano Chessa, Francesco Furfari, Francesco Potortì, Paolo Barsocchi, Mohammad-Reza Tazari, and Reiner Wichert. Evaluating AAL systems through competitive benchmarking (EvAAL) (Technical aspects of the first competition). In: Ilse Bierhoff, Henk Herman Nap, Wil Rijnen, and Reiner Wichert, Eds., proceedings of AAL Forum, pp. 102--107, Lecce (IT), September 2011. EvAAL workshop. [ bib | email | http | .pdf ]
EvAAL (Evaluating AAL Systems Through Competitive Benchmarking) is an international competition aimed at the evaluation and assessment of Ambient Assisted Living systems components, services and platforms. In 2011 took place the first edition of EvAAL on the special theme of Indoor Localization and Tracking for AAL. This paper describes the technical aspects of the first edition of EvAAL and draws a roadmap for the future editions.

Keywords: AAL; localization; tracking
[C36] Paolo Barsocchi, Stefano Chessa, Erina Ferro, Francesco Furfari, and Francesco Potortì. Context driven enhancement of RSS-based localization systems. In: proceedings of the IEEE Symposium on Computers & Communications (ISCC), pp. 463--468, Kerkyra (GR), June 2011. [ bib | DOI | email ]
RSS-based indoor localization systems are widely accepted in the literature as one of the less invasive localization technique. In fact, this range-based approach does not require any special hardware and is available in most standard wireless devices. Furthermore, judicious use of RSS (Receive Signal Strength) has not a significant impact on local power consumption, sensor size, and cost. In front of these interesting characteristics, the performance of the RSS approach is worst with respect to some more invasive ad hoc hardware range-based solutions (such as Angle of Arrival, Time of Arrival etc.). In this paper we propose a localization method that leveraging the context information, such as the knowledge of being in a given room, increases the localization accuracy of RSS-based methods. Performance evaluation is done via real measurements in an office environment composed of three adjacent rooms.

Keywords: zigbee; context information; indoor localization; RSSI localization
[C35] Paolo Barsocchi, Stefano Chessa, Francesco Furfari, and Francesco Potortì. Using context information to improve indoor localisation. In: Rainer Mautz, Melanie Kunz, and Hilmar Ingensand, Eds., Abstracts of the International Conference on Indoor Positioning and Indoor Navigation (IPIN), pp. 295--296, Campus Science City, ETH Zurich (CH), September 2010. Not peer reviewed, oral presentation. [ bib | email | .pdf ]
RSSI-based indoor localisation systems are widely accepted in the literature as one of the least invasive localisation technique. In fact, this range-based approach does not require any special hardware and is available in most standard wireless devices. Furthermore, judicious use of RSSI has not a significant impact on local power consumption, sensor size, and cost. In front of these interesting characteristics, the performance of the RSSI approach is worst with respect to some more invasive ad hoc hardware range-based solutions (such as Angle of Arrival, Time of Arrival etc...). Context information, such as knowledge of being in a given room, can increase the localisation accuracy of RSSI-based methods. In this paper we propose a localisation method that leverages context information. Performance evaluation is done via real measurements in an office environment composed of three adjacent rooms.

Keywords: zigbee; context; indoor localization; RSSI localization
[C34] Paolo Barsocchi, Francesco Furfari, Paolo Nepa, and Francesco Potortì. RSSI localisation with sensors placed on the user. In: Rainer Mautz, Melanie Kunz, and Hilmar Ingensand, Eds., proceedings of the International Conference on Indoor Positioning and Indoor Navigation (IPIN), pp. 194--199, Campus Science City, ETH Zurich (CH), September 2010. [ bib | DOI | email | .pdf ]
We examine the indoor single-room localisation problem while using multiple fixed transmitters (anchors) and multiple mobile receivers placed on the user (mobiles). Anchors transmit a periodic beacon that the mobiles receive and of which they measure the received power level value (RSSI). Using this information only, which requires no specialised hardware, the mobiles estimate the position and orientation of the user. Many methods have been proposed to tackle this problem. In this paper we describe a purely theoretical procedure that aims to evaluate the maximum attainable performance of any real methods using RSSI for localisation purpose. Our analysis we present is based on a fine grid of RSSI values in a room, which are computed via ray-tracing, and a maximum-likelihood approach to localisation. Here we illustrate the performance gains of using multiple mobiles versus using a single one and and the attainable performance of user orientation estimation.

Keywords: zigbee; accuracy limits; indoor localization; RSSI localization
[C33] Anda Guraliuc, Andrea A. Serra, Paolo Nepa, Giuliano Manara, and Francesco Potortì. Detection and classification of human arm movements for physical rehabilitation. In: proceedings of the Antennas and Propagation Society International Symposium, pp. 1--4, Toronto, ON (CA), July 2010. [ bib | DOI | email | .pdf ]
In the latest years, the detection of body posture and activity received a significant interest in the field of the physical rehabilitation aimed at providing advanced medical therapies to patients who have suffered a stroke, joint replacements/reconstructions, amputation, or some motor function disability resulting from Parkinson’s disease. Rehabilitation is a dynamic process and the restoration of patients’ functional capability to normal requires every day functional activities that need to be monitored and controlled by specialized medical operators. An effective approach is represented by motion capturing systems where some video cameras follow the movements of a number of markers placed on the human body to reconstruct its activity. However, such systems are complex, expensive and require a large number of constitutive elements (cameras and markers).

Keywords: posture identification; RSSI; radio frequency; body sensors
[C32] Alberto Gotta, Erina Ferro, and Francesco Potortì. Quality of experience in satellite video streaming transmissions in urban vehicular environment. In: proceedings of the International Workshop on Satellite and Space Communications (IWSSC), pp. 18--22, IEEE, Siena (IT), September 2009. [ bib | DOI | email | .pdf ]
In case of video streaming services via satellite towards vehicular clients, very long blockage periods due to road infrastructures, vegetation, and so on, may lead to a complete channel outage, which may result in the loss of all packets transmitted during that period, even in the presence of interleaving and FEC techniques. But if these periods are predictable, as in the presence of known routes traced by means of a GPS navigator, it may be advisable to alert the transmitter in advance, in order to counteract the incoming outage interval. We refer to this technique as Smart Mode. In the following we will detail how Smart Mode takes advantage of FEC and interleaving techniques, in order to improve the Quality of Experience and to reduce the waste of bandwidth in satellite multimedia streaming.

Keywords: video streaming; satellite; mobile; FEC; interleaver
[C31] David Pradas, Paolo Barsocchi, Francesco Potortì, Lei Jiang, and M.A. Vázquez Castro. Satellite PHY-layer selector design for video applications in tropical areas. In: proceedings of the International Workshop on Satellite and Space Communications (IWSSC), pp. 407--411, IEEE, Siena (IT), September 2009. [ bib | DOI | email | .pdf ]
This paper aims at providing different cost-efficient solutions for the channel impairments in tropical areas. In order to extend service to isolated areas, we propose an hybrid architecture based on DVB-S2/RCS + Wi-Fi networks. In this scenario, the delay of the ACM reaction to fade changes can affect the quality of the video transmission, especially because of the characteristics of tropical deep fading events. In order to avoid QoS reduction, we focus on the DVB PHY-layer shifted threshold, which we study not only for different Amazon areas and different rain conditions, but also for different reaction delays. The performance of the PHY-layer selector is evaluated in terms of video quality (PSNR), packet error rate and bandwidth efficiency.

Keywords: atmospheric fading; tropical area; video streaming; satellite; packet-level FEC
[C30] Francesco Potortì, Alessandro Corucci, Paolo Nepa, Francesco Furfari, Paolo Barsocchi, and Alice Buffi. Accuracy limits of in-room localisation using RSSI. In: proceedings of the Antennas and Propagation Society International Symposium, Charleston, SC (US), June 2009. [ bib | DOI | email | .pdf ]
Indoor localisation using inexpensive, non-dedicated wireless devices has spun great attention in the last years. We witness the ubiquitous presence of Wi-Fi access points in offices and homes, soon followed by the increasing spread of low-power, low-cost wireless nodes using the Bluetooth and, in perspective, ZigBee technologies. The presence of a potentially high number of wireless transmitters in indoor spaces has pushed researchers to investigate whether their built-in received signal strength indicator (RSSI) could be exploited to gain information on the relative position of a receiver with respect to a number of transmitters and, by knowing in advance the position of those transmitters, to pinpoint the receiver's position. Even though RSSI meters are not built to this end, but rather to give information to the higher communication protocol layers about the status of the communication link, their usage is highly attractive, because the information they give is obtained almost for free. As a consequence, many studies exist which, analytically, through simulations or through real measurements, analyse how a receiver (mobile) can best use RSSI relative to multiple wireless transmitters (anchors) to compute its position. In this paper we use detailed ray-tracing simulation to investigate the ultimate performance of indoor, single-room localisation using RSSI measurements in a specific case, and we comment on the results. This study does not lend itself to practical implementation of a localisation method, but rather provides insight into the limits of methods based on RSSI.

Keywords: indoor localisation; RSSI; Zigbee; sensors
[C29] Anda Guraliuc, Andrea A. Serra, Paolo Nepa, Giuliano Manara, Francesco Potortì, and Paolo Barsocchi. Body posture/activity detection: path loss characterization for 2.4 GHz on-body wireless sensors. In: proceedings of the Antennas and Propagation Society International Symposium, Charleston, SC (US), June 2009. [ bib | DOI | email | .pdf ]
On-body wireless sensor networks (WSNs) are gaining an increasing interest in medical, military as well as entertainment applications. Wireless transceiver modules placed on the body and combined with actuators/sensors can communicate between them and with any other node located in the surrounding environment, without any human body movement constraint with respect to wired connections. A further application of the above on-body WSNs could be in the framework of the human body posture and activity detection. Recognizing people’s activities is a key issue in Assisted Living (AL) applications, where it can be required to monitor and detect abnormalities for elderly care, or rate how a person performs routine activities. As an example, in the medical field the patient recovery and rehabilitation can be remotely monitored, controlled and recorded without the presence of a technician. Likewise, in military applications the Soldier Assist System (SAS) that provides recognition of soldier activities can be improved by body activity detection networks. In this context the authors are involved in a research activity aimed at developing algorithms for body posture/activity classification, which are based on RSS (Received Signal Strength) exploiting. Indeed, the RSS indicator is already available in most of low cost transceiver modules designed for WSNs (Smart Dust or Motes). If only a rough classification of body posture/activity is required, additional devices, as for example gyroscopes or accelerometers, could be avoided. The development of the system architecture (number of transceivers and their best placement on the human body) requires accurate path loss models to characterize radio links between a set of transceivers placed on the human body, for a number of body postures and movements. Therefore, as a first step of the above mentioned algorithm development activity, on- body path loss properties are being studied. Both numerical and experimental results will be presented in this paper. The analysis of the path loss as a function of the distance between two on-body antennas is performed at 2.4 GHz and results are shown for some radio links.

Keywords: posture identification; RSSI; radio frequency; body sensors
[C28] David Pradas Fernández, Lei Jiang, Maria Angeles Vázquez Castro, Paolo Barsocchi, and Francesco Potortì. Cost-efficient design of hybrid network for video transmission in tropical areas. In: proceedings of the IEEE Vehicular Technology Conference (VTC)- Spring, Barcelona (ES), April 2009. [ bib | DOI | email | .pdf ]
This paper aims at providing different cost-efficient solutions for the channel impairments in tropical areas. In order to extend service to isolated areas, we propose hybrid architecture based on DVB-S2/RCS+WiFi networks. In this scenario the satellite channel is affected by deep rain events that do not allow ACM modes to protect data. Moreover, the delay in the ACM reaction to fade changes can affect the quality of the video transmission. In order to avoid the QoS reduction, we focus on different Fading Mitigation Techniques (FMT), designing a multi-layer scheme protection, using LL-FEC and AL-FEC in higher layers, and optimizing the intervention threshold and super-frame length in the physical layer.

Keywords: DVB-S2; WiFi; LL-FEC; AL-FEC; Hybrid network; Tropical; video streaming
[C27] Sébastien Rumley, Dragan Savić, Francesco Potortì, Sašo Tomažič, and Christian Gaumier. Practical approaches for software components integration in telecommunications. In: International Convention MIPRO, Vol. 2, pp. 135--139, MIPRO Croatian Society, IEEE Croatia Section, University of Zagreb and University of Rijeka, Opatija (HR), May 2008. [ bib | .pdf ]
In network engineering as in other areas, sophisticated software tools have been conceived to handle models of increasing complexity. These tools theoretically support a great number of input cases. However, in practice, they are confronted to a limited set of inputs, since too large efforts are required to configure each new input case. Similarly, only a few quantitative metrics are extracted from tool results, whereas the output files could be analyzed in many different ways. The potential of a given tool could thus be decoupled if these preprocessing and post-processing tasks would be wisely automated. In this paper, we focus on these preprocessing and postprocessing operations, and propose a generic execution environment which automates them. This environment permits in particular to assess the influence of various parameters on the final results, and to perform generalized what-if analysis.

Keywords: simulation support systems
[C26] Dragan Savić, Francesco Potortì, Francesco Furfari, Janez Bešter, Sašo Tomažič, and Matevž Pustišek. Storing and exchanging simulation results in telecommunications. In: S. Blažič B. Zupančič, R. Karba, Ed., proceedings of the EUROSIM congress on Modelling and Simulation, Vol. 2, pp. 1--7, SLOSIM, Slovene Society for Simulation and Modelling, ARGESIM -- ARGE Simulation News, Ljubljana (SI), September 2007. [ bib | .pdf ]
Though storing and exchanging simulation data is a rather simple task done by simulation practitioners, it is quite often a challenge as huge quantities of data are not uncommon, and conversion between different formats can be much time consuming. After examining some of the needs of the telecommunications simulation community, we describe the architecture of a working prototype -- CostGlue -- to be used as a general-purpose archiver and converter for large quantities of simulation data. The software architecture of the CostGlue tool is modular therefore allowing further development and contributions from other research sphere of activity. The core of the tool -- CoreGlue -- is responsible for communicating with the database. It acts as a unified interface for writing to the database and reading from it. Specific functions like import and export of data and different mathematical calculations are represented as a set of self-described modules, which are loaded as necessary. The graphic user interface is introduced as a web application for the simplicity of use and effective remote access to the application. The software package CostGlue is going to be released as free software with the possibility of further development.

Keywords: simulation; measurements; data; archiving; HDF
[C25] Paolo Barsocchi, Alan Bertossi, Maria Cristina Pinotti, and Francesco Potortì. Data broadcasting algorithms on error-prone wireless channels. In: proceedings of the International Workshop on Information Security in Wireless Networks, Suceava (RO), IOS Press, September 2006. Not peer reviewed. [ bib | .pdf ]
Broadcasting is an efficient and scalable way of transmitting data over wireless channels to an unlimited number of clients. In this paper the problem of allocating data to multiple channels is studied, assuming flat data scheduling per channel and the presence of unrecoverable channel transmission errors. The objective is that of minimizing the average expected delay experienced by the clients. Two different channel error models are considered: the Bernoulli model and the simplified Gilbert-Elliot one. In the former model, each packet transmission has the same probability to fail and each transmission error is independent from the others. In the latter one, bursts of erroneous or error-free packet transmissions due to wireless fading channels are modeled. For both channel error models, optimal solutions can be found in polynomial time when all data items have unit lengths, while heuristics are presented when data items have non-unit lengths. Extensive simulations, performed on benchmarks whose item popularities follow Zipf distributions, show that good sub-optimal solutions are found.

Keywords: wireless communication; data broadcasting; multiple channels; flat scheduling; average expected delay; channel transmission errors; Bernoulli model; Gilbert-Elliot model; heuristics
[C24] Paolo Barsocchi, Gabriele Oligeri, and Francesco Potortì. Frame error model in rural Wi-Fi networks. In: proceedings of the International Symposium on Modeling and Optimization (Wiopt), pp. 41--46, IEEE, Limassol (CY), April 2007. WiNMee/WiTMeMo workshop. [ bib | DOI | .ps.gz | .pdf ]
Commonly used frame loss models for simulations over Wi-Fi channels assume a simple double regression model with threshold. This model is widely accepted, but few measurements are available in the literature that try to validate it. As far as we know, none of them is based on field trials at the frame level. We present a series of measurements for relating transmission distance and packet loss on a Wi-Fi network in rural areas and propose a model that relates distance with packet loss probability. We show that a simple double regression propagation model like the one used in the ns-2 simulator can miss important transmission impairments that are apparent even at short transmitter-receiver distances. Measurements also show that packet loss at the frame level is a Bernoullian process for time spans of few seconds. We relate the packet loss probability to the received signal level using standard models for additive white Gaussian noise channels. The resulting model is much more similar to the measured channels than the simple models where all packets are received when the distance is below a given threshold and all are lost when the threshold is exceeded.

Keywords: ns2; model; AWGN; FER; frame error rate
[C23] Alberto Gotta, Raffaello Secchi, and Francesco Potortì. Simulating dynamic bandwidth allocation on satellite links. In: proceedings of the International Conference on Performance Evaluation Methodologies and Tools (Valuetools), p. 8, ACM, Pisa (IT), October 2006. WNS2 workshop. [ bib | DOI | .pdf ]
In the last years, DVB-RCS has emerged as a flexible technology offering broadband Internet access to a large community of users at a relatively low cost. At the same time, the spreading of networked multimedia applications has highlighted the need to investigate mechanisms that guarantee a certain level of Quality of Service (QoS) to the end users. In particular, the DVB-RCS standard specifies different capacity request categories to support QoS at the link layer. We describe Tdma-bod, an ns-2 improvement that implements generic bandwidth-on-demand allocation in TDMA satellite systems; the patch is available as free software. This simulator has been validated through experimental tests performed on the Skyplex satellite system. Specifically, we run CBR UDP flows to measure the characteristics of the satellite link in terms of throughput and delay and to verify that the simulative model output matches the experimental dynamic throughput and one-way delay behaviour. The simulations and experiments show that bandwidth-on-demand allocation mechanisms may cause large delays when sudden variations in the incoming traffic rate occur, a behaviour typical of multimedia flows.

Keywords: ns2; TDMA; BoD; DAMA
[C22] Dragan Savić, Matevž Pustišek, and Francesco Potortì. A tool for packaging and exchanging simulation results. In: proceedings of the International Conference on Performance Evaluation Methodologies and Tools (Valuetools), p. 60, ACM, Pisa (IT), October 2006. [ bib | .pdf ]
Storing and exchanging simulation data is a common task among simulation practitioners, but quite often it becomes a challenge as huge quantities of data are not uncommon, and conversion between different formats can become an unwieldy task. After examining some of the needs of the telecommunications simulation community, we describe the architecture of the working prototype of a general purpose archiver and converter for big quantities of simulation data to be released as free software.

Keywords: Measurements; Simulation; Data; Archiving; HDF
[C21] Alberto Gotta, Raffaello Secchi, and Francesco Potortì. An analysis of TCP startup over an experimental DVB-RCS platform. In: proceedings of the International Workshop on Satellite and Space Communications (IWSSC), pp. 176--180, Madrid (ES), September 2006. [ bib | DOI | .pdf ]
Satellite systems are evolving towards higher available bandwidths and dynamic allocation based on instantaneous traffic rates offered at the stations, so called BoD (bandwidth on demand) channel sharing. This trend is paired with more and more powerful error correcting schemes, like those adopted in the recent DVB-S2 standard, which promise to make the channel virtually immune from packet errors. These factors, together with the significant round-trip delay of geostationary satellites, combine so that most TCP connections would send all of their data during the Slow Start phase. We investigate the performance of TCP during startup on recent BoD system by observing and explaining the behavior of different TCP flavors on different systems when transmitting data over the Eutelsat's Skyplex Data satellite system. We make recommendations for choosing and improving TCP implementations and for future BoD allocation schemes.

Keywords: TDMA; BoD; DAMA; TCP; startup
[C20] Paolo Barsocchi, Gabriele Oligeri, and Francesco Potortì. Packet loss in TCP hybrid wireless networks. In: proceedings of the Advanced Satellite Mobile Systems Conference (ASMS), Herrsching (DE), May 2006. (No page numbers). [ bib | .ps.gz | .pdf ]
Hybrid networks where packets travel through both a geostationary satellite and a terrestrial local wireless link are a particularly challenging environment with respect to TCP performance. The reason is that such networks exhibit both a high latency and a high packet loss, a combination that stresses TCP's congestion avoidance algorithm. Accurate modelling of the packet loss process in such networks is not an easy task, so very simplified models are frequently used. We present channel state measurements done on fixed-speed IEEE 802.11 terrestrial networks. We use the ns-2 simulator to evaluate the performance of TCP on the said channel. We then evaluate the accuracy of some models that are commonly used to represent the channel state, by comparing these models with actual traces.

Keywords: Hybrid networks; WiFi; satellite; packet loss; burst
[C19] Paolo Barsocchi, Alberto Gotta, Francesco Potortì, Francisco Javier González-Castaño, Felipe Gil-Castiñeira, Jose I. Moreno, and Antonio Cuevas. Experimental results with forward erasure correction and real video streaming in hybrid wireless networks. In: proceedings of the International Symposium on Wireless Communication Systems (ISWCS), Siena (IT), pp. 662--666, IEEE, September 2005. International Workshop on Satellite and Space Communications (IWSSC). [ bib | .pdf ]
In a heterogeneous MANET, based on wireless LANs linked together by satellite, the overall channel efficiency is impaired by multiple effects, because of multipath fading in the terrestrial segment and signal fading on the satellite link. In this paper we address this issue by applying forward erasure correction codes (FZC) to MPEG-4 video sequences exchanged by the hosts of a hybrid network, made of a satellite link and a wireless LAN using 802.11b devices. A standard video streaming application runs on one end of the satellite link while, at the final end, a wireless ad hoc network receives the multicast video stream. This work aims at demonstrating the improvement in Quality of Service (QoS) of the video transmitted in the hybrid network. The main parameters measured are the packet loss, the delivery delay, and the overhead in bandwidth occupancy imposed by the use of FZC. The received video is then evaluated by using a MOS (Mean Opinion Score) procedure.

Keywords: erasure codes; video; 802.11; satellite; packet loss
[C18] Francesco Potortì. Free software and research. In: Marco Scotto and Giancarlo Succi, Eds., proceedings of the International Conference on Open Source Systems (OSS), Genova (IT), pp. 270--271, ECIG Edizioni Culturali Internazionali Genova, July 2005. Short paper. [ bib | .pdf | .ps | .pdf ]
Free software licenses are a natural choice in a research environment. In the following, we will try to back this simple statement with some considerations and examples, in an effort to analyse the significant interactions between free software and research.

Keywords: free software; advocacy; academy
[C17] Nedo Celandroni, Erina Ferro, and Francesco Potortì. Goodput optimisation of long-lived TCP connections in a rain-faded satellite channel. In: proceedings of the IEEE Vehicular Technology Conference (VTC)- Spring, Milano (IT), Vol. 5, pp. 2901--2905, IEEE, May 2004. [ bib | .ps.gz | .pdf ]
The optimization of the end-to-end throughput of a TCP connection over geostationary satellite links is a challenging research topic because the high delay-bandwidth product, together with a non-negligible random loss of packets, are conditions which differ considerably from the original environment for which TCP was originally designed. As a result, TCP performance is significantly impaired by the channel bit error rate. In this paper we investigate the application of different FEC (forward error correction) types/rates and different bit rates, for the optimization of TCP goodput, in transmissions over a rain-faded geostationary satellite channel, provided that the end-to-end protocols are left unaltered. We compare physical-level FEC techniques, such as convolutional encoding/Viterbi decoding and Reed Solomon, link-level erasure codes and their combinations, over a wide field of signal-to-noise conditions of the satellite channel. The case of multiple connections per link is also analyzed, in addition to that of a single connection per link. . In order to evaluate the throughput of TCP long-lived connections we used a fluid simulator ad-hoc developed.

Keywords: Long-lived TCP connections; rain fading; satellite channel; FEC techniques
[C16] Nedo Celandroni, Erina Ferro, Francesco Potortì, Giacomo Saviozzi, and Marco Boldrini. The intracoastal satellite communicator system (ISCS). In: proceedings of the AIAA International Communications Satellite Systems Conference (ICSSC), Toulouse (FR), p. 282, April 2001. [ bib | .pdf ]
This paper describes an application of the ORBCOMM satellite system for helping pleasure-boat sailors to navigate. The IntraCoastal Satellite Communication System (ICSCS) is an improvement on the well established ChartPlotter made by Geonav 11E Navionix for bidirectional coastal communication. By using a terminal of the ORBCOMM system, ICSCS allows the sailors to access and retrieve information which has been coded ad-hoc on web sites. The paper briefly describes the software architecture of the system and presents the additional user facilities. The IntraCoastal Satellite Communicator System has been available on the market since beginning of year 2000, and has already been installed on many pleasure boats in Italy.

Keywords: satellite; Orbcomm; Synthema; navigation
[C15] Laurent Franck and Francesco Potortì. GaliLEO: a simulation tool for LEO satellite constellations. In: proceedings of the IST Mobile Summit, Galway (GB), pp. 735--758, October 2000. [ bib | .ps.gz | .pdf ]
Abstract: We present Galileo, a simulator for the transmission of both connection-oriented and connectionless traffic over a constellation of LEO/MEO (Low/Medium Earth Orbit) satellites. Its scope is limited to the satellites and the stations accessing them, without any modelling of the terrestrial network, but inside this scope the goal is to study the performance of satellite-based communication networks from as many as possible points of view. Typical applications include simulation of access techniques, routing policies, fault management. The simulator is written in Java, and it makes use of dynamic loading to easily integrate user-written modules. A draft manual is available, and a preliminary version of the program will be published by the end of 2000.

Keywords: satellite; LEO; MEO; simulator
[C14] Nedo Celandroni, Erina Ferro, and Francesco Potortì. Performance evaluation of a multi-level allocation algorithm for VBR traffic over a GEO satellite. In: proceedings of the Symposium on Performance Evaluation of Computer and Telecommunication Systems (SPECTS), Vancouver (US-CA), pp. 452--457, July 2000. [ bib | .ps.gz | .pdf ]
In this paper we present VnL-TDMA, a new MAC (medium access control) protocol for accessing in TDMA a satellite channel shared among various earth stations which transmit mixed traffic (real-time and non-real time). We concentrate on the analysis of the real-time allocation for variable bit rate (VBR) traffic, and analyse its performance using a synthetically generated VBR traffic modelled on the basis of the statistical parameters of an MPEG-2 coded movie in VBR mode. The peak traffic rate of the movie is almost four times higher than its mean rate, which means that trivial peak rate allocation would waste a lot of the satellite channel bandwidth, while VnL makes unused bandwidth instantaneously available to all earth stations to enable them to transmit best-effort traffic.

Keywords: TDMA; VBR; MPEG; allocation method; multilevel; satellite
[C13] Nedo Celandroni, Erina Ferro, Francesco Potortì, Antonio Chimienti, and Maurizio Lucenteforte. DRS compression applied to MPEG-2 video data transmitted over a satellite channel. In: proceedings of the IEEE Symposium on Computers & Communications (ISCC), Antibes-Juan Les Pins (FR), pp. 259--266, July 2000. [ bib | email ]
[C12] Nedo Celandroni, Erina Ferro, Francesco Potortì, and Laurent Franck. GaliLEO: a simulation tool for traffic on LEO satellite constellations. Presentation of the architecture. In: proceedings of the COST 252-253-255 Workshop, Toulouse (FR), pp. 145--153, May 1999. Not peer reviewed. [ bib | .pdf ]
The aim of this work is to create a tool that can simulate the transmission of both connection-oriented and connection-less traffic over a constellation of LEO/MEO (Low Earth Orbit/ Medium Earth Orbit) satellites. We hope to provide a performance evaluation of various constellation access techniques and routing policies. The simulator, named GaliLEO, will be written in Java and will integrate results from another simulator (CONSIM from CSELT, I) to study the impact of faults in system performance. GaliLEO should eventually become the simulation tool for the Cost253 action, thus providing a common tool for all studies taking place in the action. At the time of writing, considerable interest is being shown in GaliLEO.

[C11] Nedo Celandroni, Erina Ferro, and Francesco Potortì. An emulator for testing the performance of framed access schemes. In: proceedings of the IEEE Conference on Global Communications (GLOBECOM), Sidney (AU), pp. 1590--1593, November 1998. [ bib | email ]
[C10] Nedo Celandroni, Erina Ferro, Francesco Potortì, Antonio Chimienti, and Maurizio Lucenteforte. Experimental results of MPEG-2 coded video transmission over a noisy satellite link. In: proceedings of the International Conference on Telecommunications, Porto Carras (GR), pp. 221--225, June 1998. [ bib | .ps.gz | .pdf ]
Keywords: MPEG video; scalability; quality factor; satellite; fading
[C09] Nedo Celandroni, Erina Ferro, Francesco Potortì, and Gérard Maral. Bursty data traffic via satellite: performance comparison between two TDMA access schemes. In: proceedings of the European Conference on Satellite Communications (ECSC), Roma (IT), pp. 170--175, November 1997. [ bib | email ]
[C08] Nedo Celandroni and Francesco Potortì. A fractal attenuation model for the Ka band. In: proceedings of the Ka Band Utilisation Conference, Sorrento (IT), pp. 307--314, September 1997. [ bib | email ]
[C07] Nedo Celandroni and Francesco Potortì. An inexpensive rain fade countermeasure technique for DA-TDMA satellite systems. In: proceedings of the IEEE Conference on Global Communications (GLOBECOM), London (UK), pp. 1001--1005, November 1996. [ bib | .ps.gz | .pdf ]
Rain attenuation countermeasure systems for geostationary satellite transmissions have been proposed that use a variety of methods. This paper presents a technique which only requires a burst modem that is able to vary its bit and coding rate on a sub-burst basis coupled with a convolutional encoder/Viterbi decoder. A complete method for predicting the attenuation at the receive time is described for two different DA-TDMA systems, using centralised and distributed control, respectively. The method is used for choosing the up power, bit and coding rate of the data to be transmitted. Its performance is evaluated on the basis of experimental results.

[C06] Nedo Celandroni, Erina Ferro, and Francesco Potortì. The performance of the FODA/IBEA satellite access scheme measured on the Italsat satellite. In: proceedings of the International Conference on Digital Satellite Communications (ICDSC), Brighton (UK), pp. 332--338, May 1995. [ bib | email ]
[C05] Nedo Celandroni, Erina Ferro, and Francesco Potortì. The Italian contribution to the integration of terrestrial and satellite networks. In: proceedings of the final symposium of the COST-226 project - Integrated Space/Terrestrial Networks, Budapest (HU), pp. 159--169, May 1995. [ bib | email ]
[C04] Nedo Celandroni, Erina Ferro, and Francesco Potortì. Outage probability of an adaptive TDMA satellite access scheme. In: proceedings of the International Conference on Communications (ICC), Geneva (CH), pp. 1449--1454, May 1993. [ bib | DOI | .ps.gz | .pdf ]
[C03] Nedo Celandroni, Erina Ferro, Maurizio Neri, and Francesco Potortì. The Italian Olympus TDMA experiment. In: proceedings of the Olympus Utilization Conference, Sevilla (ES), pp. 55--59, April 1993. [ bib | email ]
[C02] Nedo Celandroni, Erina Ferro, Nick James, and Francesco Potortì. Design and implementation of a flexible, software based TDMA system. In: proceedings of the IEEE Conference on Global Communications (GLOBECOM), Orlando (US-FL), pp. 693--699, December 1992. [ bib | email ]
[C01] Nedo Celandroni, Erina Ferro, and Francesco Potortì. A traffic generator for the performance evaluation of a satellite network. In: proceedings of the International Conference on Communication Technology (ICCT), Beijing (CN), pp. 9.08.01--9.08.05, September 1992. [ bib | email ]
[B06] Erina Ferro and Francesco Potortì. ISI Trials and Demonstrations Report, Chap. 7: SatNEx JA2410 FT1 WICHMO, pp. 47--51. ISI - The Integral Satcom Initiative, January 2010. White paper. [ bib | email | http ]
Keywords: simulation; FER; two-ray; AWGN; fading
[B05] Erina Ferro and Francesco Potortì. ISI Trials and Demonstrations Report, Chap. 6: SatNEx JA2410 FT4 VOTOS, pp. 43--46. ISI - The Integral Satcom Initiative, January 2010. White paper. [ bib | email | http ]
Keywords: Hybrid networks; WiFi; satellite; packet loss; burst
[B04] Francesco Furfari, Francesco Potortì, and Dragan Savić. The CostGlue XML schema. Tech. Rep. cnr.isti/2008-TR-003, CNR-ISTI, via Moruzzi, 1, January 2008. [ bib | http | .pdf ]
An XML schema for scientific metadata is described. It is used for the CostGlue archival program, developed in the framework of the European Union COST Action 285: Modelling and simulation tools for research in emerging multi-service telecommunications. The schema is freely available under the GNU LGPL license at http://wnet.isti.cnr.it/software/costglue/schema/2007/CostGlue.xsd, or at its official repository, at http://lt.fe.uni-lj.si/costglue/schema/2007/costglue.xsd.

[B03] Paolo Barsocchi, Gabriele Oligeri, and Francesco Potortì. Transmission range and frame error process in rural area Wi-Fi networks. Tech. Rep. ISTI-2006-TR-43, CNR-ISTI, via Moruzzi, 1, June 2006. [ bib | http | .pdf ]
Few researchers have performed measurements of a Wi-Fi channel at the frame level in order to understand performance issues by relating frame errors and signal strength. This paper presents results relative to ad hoc measurements in a rural environment. We show that a simple double regression propagation model like the one used in the ns-2 simulator can miss important transmission impairments that are apparent even at short transmitter-receiver distances. We propose a two-ray propagation model which improves on those commonly used for simulation purposes. Frames were transmitted and received by using two cheap laptops with standard Linux drivers. Measurements also show that packet loss at the frame level is a Bernoullian process for time spans of few seconds, and that longer time spans exhibit a more complex behaviour, meaning that the 2-state Markov-modulated process often used in the literature is not a good match for rural areas.

[B02] Paolo Barsocchi, Gabriele Oligeri, and Francesco Potortì. Validation for 802.11b wireless channel measurements. Tech. Rep. ISTI-2006-TR-29, CNR-ISTI, via Moruzzi, 1, June 2006. [ bib | http | .pdf ]
Few researchers have undertaken the task of measuring the wireless channel at the frame level to understand performance issues related to frame loss and signal strength. This paper proposes a measurement procedure for terrestrial wireless networks based on cheap hardware and custom software, and validates it through experiments on real-word wireless environment. In order to validate the measurement procedure, we carry out a comprehensive measurement campaign in a rural environment and we evaluate statistics about frame loss and signal level in the IEEE 802.11b wireless channel. Frames are transmitted and received by using two cheap laptops with standard Linux drivers and purposely written software. A first validation step compares the behaviour of the received signal power level with the two-ray propagation model. A subsequent step compares the observed frame loss with the expected coding gain at various transmission rates. Graphs of the observed frame loss rate at different transmission rates are provided for a rural environment, where the two-ray propagation model is a good fit.

[B01] Nedo Celandroni, Erina Ferro, and Francesco Potortì. Goodput optimization of long-lived TCP connections in a faded satellite channel. Tech. Rep. ISTI-2003-TR-69, CNR-ISTI, via Moruzzi, 1, June 2003. Extended version. [ bib | http | .ps.gz ]
The optimization of the end-to-end throughput of a TCP connection over geostationary satellite links is a challenging research topic because the high delay-bandwidth product, together with a non-negligible random loss of packets, are conditions which differ considerably from the original environment for which TCP was originally designed. As a result, TCP performance is significantly impaired by the channel bit error rate. In this paper we investigate the application of different FEC (forward error correction) types/rates and different bit rates, for the optimization of TCP goodput, in transmissions over a rain-faded geostationary satellite channel, provided that the end-to-end protocols are left unaltered. We compare physical-level FEC techniques, such as convolutional encoding/Viterbi decoding and Reed Solomon, link-level erasure codes and their combinations, over a wide field of signal-to-noise conditions of the satellite channel. The case of multiple connections per link is also analyzed, in addition to that of a single connection per link. In order to evaluate the throughput of a TCP long-lived connection we used a method that is midway between analysis (fluid model) and simulation.


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