Carlo Caini

University of Bologna | UNIBO · "Guglielmo Marconi" Department of Electrical, Electronic and Information Engineering DEI

Challenged networks, including space networks, require the Delay-/ Disruption-Tolerant Networking architecture (DTN), which is based on the introduction of a new layer and a new associate protocol, the Bundle Protocol (BP). The recent release of RFC 9171, which standardizes version 7 (BPv7), has led the University of Bologna to develop its own impl...

This paper aims to investigate the potential advantages and also the limits of source routing when applied to delay-/disruption-tolerant networking (DTN) space networks. To this end, it uses a variant of contact graph routing (CGR) called moderate source routing (MSR), recently proposed by the authors and fully compatible with interplanetary overla...

This chapter discusses the advantages of delay/disruption-tolerant networking (DTN) when applied to satellite communications, considering geosynchronous (GEO) and low Earth orbit (LEO) constellations. The chapter analyses the challenges of GEO communications and shows how the DTN architecture can be interpreted as an elegant architectural extension...

The Delay‐/Disruption‐Tolerant Networking (DTN) architecture was designed to cope with challenges such as long delays and intermittent connectivity. To exploit the a priori knowledge of contacts, typical of space networks, NASA‐JPL designed and included in ION (its DTN protocol suite) the Contact Graph Routing (CGR) algorithm. This paper studies th...

The delay‐/disruption‐tolerant networking (DTN) architecture is considered the key enabling technology for future space communications, as confirmed by the current standardization within CCSDS and the experiments carried out onboard the International Space Station. Despite the scientific community efforts to analyze DTN architecture performance, mo...

This paper aims to present a possible alternative to direct file transfer in “challenged networks”, by using DTNbox, a recent application for peer-to-peer directory synchronization between DTN nodes. This application uses the Bundle Protocol (BP) to tackle long delays and link intermittency typical of challenged networks. The directory synchronizat...

Interplanetary Networks are affected by long propagation delays, intermittent connectivity, possible packet losses due to residual errors, and other impairments. To cope with these challenges, the Delay-/Disruption-Tolerant Networking (DTN) architecture utilizes the Licklider Transmission Protocol (LTP) as Convergence Layer on space links. The LTP...

This paper deals with the performance of Licklider Transmission Protocol (LTP) in space environment, focusing on the impact of segment losses and the design of possible improvements. The in-depth analysis of retransmission mechanisms carried out in the paper shows that, while LTP already achieves delivery time performance very close to the theoreti...

Routing in Delay-/Disruption-Tolerant Networking (DTN) has long been recognized as a challenging research topic. The difficulty lies in the fact that link intermittency and network partitioning, possibly coupled with long delays, prevent the use of Internet solutions based on an up-to-date comprehensive knowledge of network topology, as communicate...

Virtualbricks is a virtualization solution for GNU/Linux platforms developed by the authors and included in Debian. The paper aims to show its potential, referring to version 1.0, just released, when applied to both research and education on DTN satellite communications. In brief, Virtualbricks is a frontend for the management of Qemu/KVM Virtual M...

This chapter discusses the advantages of DTN (delay/disruption-tolerant networking) when applied to satellite communications, considering GEO (geosynchronous) and LEO (low earth orbit) constellations. The chapter analyses the challenges of GEO communications and shows how the DTN architecture can be interpreted as an elegant architectural extension...

In this paper, we analyze the performance of two contact graph routing (CGR) enhancements, namely, CGR with earliest transmission opportunity (CGR-ETO) and overbooking management. CGR-ETO aims to improve the accuracy of predicted bundle delivery time by exploiting existing information on queueing delay, in routing decisions. Overbooking management...

Delay- and Disruption Tolerant Networks (DTNs) are based on an overlay protocol and on the store-carry-forward paradigm. In practice, each DTN node can store information for a long time before forwarding it. DTNs are particularly suited to cope with the challenges imposed by the space environment. This paper is focused on routing in space DTNs, and...

This chapter discusses the advantages of DTN (delay/disruption-tolerant networking) when applied to satellite communications, considering GEO (geosynchronous) and LEO (low earth orbit) constellations. The chapter analyses the challenges of GEO communications and shows how the DTN architecture can be interpreted as an elegant architectural extension...

In this paper we present two enhancements to Contact Graph Routing (CGR), a Delay-/ Disruption- Tolerant Networking routing algorithm developed by NASA JPL for space environments with predetermined connectivity schedules, such as Interplanetary communications and LEO satellite systems. The first enhancement, CGR-ETO, aims to improve the accuracy of...

SUMMARY Delay-Tolerant/Disruption-Tolerant Networking (DTN) architecture will be used in future deep space missions, to enable autonomous networking operations and disruption-tolerant data communications. Therefore, it is worth analyzing the performance of the DTN Bundle Protocol (BP) in a realistic deep space environment, reproducing the character...

Delay-/Disruption- Tolerant Networking (DTN) was first conceived to cope with the impairments of Inter-Planetary Internet. Then its scope was enlarged to cover all “challenged networks”, where long delays, disruption, link intermittency and other challenges prevent, or make difficult, the use of ordinary Internet architecture. To assess DTN perform...

Delay/Disruption-Tolerant Networking (DTN) originated from research on Interplanetary Internet and still today space applications are the most important application field and research stimulus. This paper investigates DTN communications between the Earth and the far side of the Moon, by means of a lunar orbiter acting as relay. After an introductor...

Delay-/Disruption- Tolerant Networking (DTN) aims at providing interoperable communications in "challenged networks", where long delays, disruption, link intermittency and other challenges prevent, or make difficult, the use of the ordinary Internet architecture. Given their heterogeneity, to assess DTN performance in challenged networks is challen...

LEO satellites are characterized by intermittent connectivity with their ground stations. Contacts are short and separated by long intervals, which with urgent data can become a critical factor. To solve this problem, the use of GEO satellites as relay has recently been suggested. This solution is appealing, but has some limits, especially with pol...

Although Delay-/Disruption- Tolerant Networking, which originated from research on an Interplanetary Internet, has enlarged its scope to encompass all challenged networks, space applications are still one of its most important application fields. This paper deals with DTN communication from Moon to Earth, based on the use of a lunar satellite actin...

Delay-/Disruption-Tolerant Networking, which originated from research on deep space communications, has enlarged its scope to encompass all challenged networks, including LEO satellite communications. Focusing on single satellite or incomplete constellation cases, the advantages of DTN mainly relate to its ability to cope with disruption and interm...

Satellite communications are characterized by long delays, packet losses, and sometimes intermittent connectivity and link disruptions. The TCP/IP stack is ineffective against these impairments and even dedicated solutions, such as performance enhancing proxies (PEPs), can hardly tackle the most challenging environments, and create compatibility is...

Satellite communications are an interesting and promising application field for Delay/Disruption Tolerant Networking (DTN). Although primarily conceived for deep space communications and sensor networks, it was immediately recognized that DTN was applicable to satellite environments, in particular to cope with the intermittent channels typical of L...

Delay-/Disruption-Tolerant Networking represents an innovative way to cope with satellite communications impairments. In this view, the paper presents an in-depth analysis of implications of a DTN approach to satellite communications, focusing on these fundamental aspects: network architecture, security, and Quality of Service (QoS). For each topic...

One of the most crucial problems to solve in the field of mobile communication networks is the evaluation for a generic link of the network of the outage probability due to the random characteristics of the transmission system, essentially determined by anomalous propagation conditions, cochannel interference and user mobility. The exact analytical...

Evaluation of spectrum efficiency in mobile radio systems is often performed by different authors starting from different working assumptions; that yields results that are not easily comparable outside the “scenario” where they have been achieved. This paper attempts to settle this controversial matter providing some criteria for overcoming these d...

Although first conceived for the Interplanetary Internet, DTN (Delay-/Disruption-Tolerant Networking) architecture has successively enlarged its application scope to embrace all “challenged networks”, i.e. networks where the TCP design key assumptions of short RTT, no disruptions, and continuous end-to-end path availability are challenged. The dist...

At present, Internet is based on the availability of a continuous path from the source to the sink node and on limited delays. These assumptions do not hold in “challenged networks”, which comprise a wide variety of different environments, from sensor networks to space communications (including satellite systems). These networks are the preferred t...

“Challenged networks” often violate the TCP design key assumption of continuous path availability from the source to the sink node. These networks are the preferred target of Delay/Disruption Tolerant Networking (DTN), which aims at providing a more robust network architecture. Against disruptions, however, even standard TCP offers a certain level...

Delay/disruption tolerant networking (DTN) has recently been proposed as a very effective solution to cope with the problems posed by challenged networks (long delays, disruptions, absence of end-to-end connectivity, etc.). In order to assess DTN performance in such scenarios, it is essential to be able to rely on specific evaluation tools. In this...

Fixed GEO satellite communications are impaired by long RTTs and the possible presence of packet losses on the satellite radio channel. Moreover, when the satellite receiver is mobile, short and long disruptions due to line of sight obstructions can cause further performance deterioration. In this paper, we present a preliminary assessment of disru...

ldquoChallenged Networksrdquo often violate the TCP design key assumption of continuous path availability from the source to the sink node. These networks are the preferred target of Delay/Disruption Tolerant Networking (DTN), which aims at providing a more robust network architecture. Against disruptions, however, even standard TCP offers a certai...

Satellite communications are essential to provide Internet access to wide areas, helping bridge the "digital divide". However, long RTTs and the possible presence of losses due to satellite channel errors, severely impair standard TCP performance. To overcome this problem several approaches are possible, including the adoption of enhanced versions...

The paper describes a measurement campaign carried out by the University of Bologna (UoB), the National Inter-University Consortium for Telecommunications (CNIT) and the University of California Los Angeles (UCLA). The aim of the experiments was the performance assessment of a wide range of TCP enhancements on network environments that include a re...

Fixed GEO satellite communications are impaired by long RTTs (especially GEO) and the possible presence of packet losses on the satellite radio channels. Moreover, when the satellite receiver is mobile, short and long disruptions due to line of sight obstructions associated with the presence of shadowing can cause further performance deterioration...

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 measurement campaign results and evaluation tools, in order to support research activities that investigate problems in satellite communications at different lev...

The increasing level of heterogeneity of present and future networks poses new challenges to TCP. Wired and wireless connections (including satellite) with very different characteristics, concerning bandwidth, RTT and loss rate, will have to co-exist and to compete, possibly in a fair way, in the same network. This heterogeneity makes difficult the...

Satellite communications pose serious challenges to transport layer performance, mainly because of long propagation delays (especially in geosynchronous systems) and the possi ble presence of random errors on the satellite link. Solutions that cope with these impairments usually rely upon either the adoption of enhanced versions of transport protoc...

The rapidly increasing importance of wireless communications (including satellite), together with the rapid growth of high speed networks, pose new challenges to transmission control protocol (TCP). Among them, the most prominent are long round trip times (RTTs), not negligible packet error rates (PER), and very large bandwidths. To overcome them,...

ABSTRACT Research on TCP performance relies either on simulation programs, which run on a single machine, or on the use of real testbeds, where different machines ,represent ,different network ,nodes ,and ,data exchange,is made ,through physical network ,interfaces. This paper proposes a different solution, with the aim of taking the best of both t...

The purpose of any communication system is to reliably transfer information between the source and destination. As a signal propagates through a wireless channel, it experiences random fluctuations in time, due to changes in reflections and attenuations. Thus, the channel characteristic of the channels change randomly with time. The average signal...

The rapidly increasing importance of wireless communications (including satellite) together with the rapid growth of high speed networks pose new challenges to TCP. To overcome them, a wide variety of TCP enhancements has been presented in literature. However, because most proposals aim to address different impairments, the choice of "the best" TCP...

Satellite communications pose serious challenges to transport layer performance, mainly because of long propagation delays (especially in geosynchronous systems) and the possible presence of random errors on the satellite link. Solutions that cope with these impairments usually rely upon either the adoption of enhanced versions of transport protoco...

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The paper describes a measurement campaign recently carried out by University of Bologna (UoB), National Inter-University Consortium for Telecommunications-(CNIT) and University of California Los Angeles (UCLA), on the CNIT GEO Skyplex platform. The aim of the experiments is the performance assessment of a wide range of TCP enhancements on network...

The paper describes a measurement campaign recently carried out by University of Bologna (UoB), National Inter-University Consortium for Telecommunications-(CNIT) and University of California Los Angeles (UCLA), on the CNIT GEO Skyplex platform. The aim of the experiments is the performance assessment of a wide range of TCP enhancements on network...

The paper describes the Testbed for Advanced Transport Protocols and Architecture (TATPA) developed by the University of Bologna, inside the SatNEx (Satellite Network of Excellence) framework. The aim is to provide partners, and in general the scientific community, with a powerful and flexible emulation tool to evaluate new proposal at transport la...

SUMMARY 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 satellit...

To overcome the unsatisfactory performance offered by standard TCP variants in the challenging satellite environment, the scientific community has presented a wide variety of possible solutions, encompassing both innovative transport protocols and architectures. Among these, the paper focuses on those TCP variants that have been actually implemente...

In the paper, the authors aim to quantitatively and qualitatively assess the impact of the cellular environment on TCP performance. The analysis is carried out through a test bed platform working in real time. Its core is represented by the GALATEA emulator, which allows the users to include all the characteristics of a real UMTS system. Four cellu...

TCP connections that incorporate satellite links are greatly disadvantaged with respect to entirely wired connections, because of their longer round trip times (RTTs). TCP Hybla has been conceived with the primary aim to solve this problem, therefore it appears quite promising in geostationary (GEO) satellite environments, where the long propagatio...

In this paper, we present our Advanced TCP Evaluation Testbed on

Internet communications with paths that include satellite link face some peculiar challenges, due to the presence of a long propagation wireless channel. In this paper, we propose a performance enhancing proxy (PEP) solution, called PEPsal, which is, to the best of the authors' knowledge, the first open source TCP splitting solution for the GNU/Lin...

The challenges posed by data communications over both satellite and terrestrial wireless systems make the adoption of adequate countermeasures advisable. In particular, the poor performance experienced by TCP transport protocol in such environments has fed the scientific community to propose novel solutions, from both the protocols and architecture...

Although TCP has proved very effective and robust for many years, its performance on emerging heterogeneous networks is challenged by the impairments originated by the presence of radio links. In particular, satellite communications are affected by long RTTs and possibly also by random segment losses, which can severely affect end-to-end performanc...

Satellite systems offer several advantages to wireless Internet communications. Nevertheless, satellite radio links are affected by two severe problems, namely long propagation delays and relatively high error rates, which pose a difficult challenge to the Internet protocols and in particular to TCP. Among the potential solutions, we are specifical...

A precise identification of prosodic phenomena and the construction of tools able to properly manage such phenomena are essential steps to disambiguate the meaning of certain utterances. In particular they are useful for a wide variety of tasks: automatic recognition of spontaneous speech, automatic enhancement of speech-generation systems, solving...

In the recent past, several solutions have been proposed to improve TCP performance over wired and wireless links. In this context, the main issue that arises when dealing with different TCP proposals is the necessity of a common benchmark environment, where each solution could be tested and evaluated. This is a fundamental step for a fair comparis...

In heterogeneous networks, TCP connections that incorporate a terrestrial or satellite radio link are greatly disadvantaged with respect to entirely wired connections, because of their longer round trip times (RTTs). To cope with this problem, a new TCP proposal, the TCP Hybla, is presented and discussed in the paper. It stems from an analytical ev...

This paper applies the theoretical framework for the evaluation of code acquisition in the presence of fading developed in the companion Part I paper. Code synchronization for code-division multiple-access (CDMA) cellular networks, such as IS-95 and cdma2000, is considered. A multidwell testing procedure is adopted. Notably, a procedure for the opt...

This paper deals with the analysis of the code-acquisition process performed by a mobile terminal in a code-division multiple-access cellular system. The fundamental contribution is the setting of a theoretical framework for code-acquisition analysis, accounting for the presence of fading and shadowing with specified coherence time. A multidwell ar...

This paper presents a study on the automatic detection of prosodic prominence in continuous speech, with particular reference to American English, but with good prospects of application to other languages. Perceptual prosodic prominence is supported by two different prosodic features: pitch accent and stress. Pitch accent is acoustically connected...

In all the TCP protocol variants, included the TCP Hybla proposal recently presented by the authors, the segment transmission rate is given by the ratio between the congestion window (cwnd) and the round trip time (RTT). As a result, to provide a high throughput to long RTT connections (e.g. satellite), it is necessary to make use of large cwnds, w...

In heterogeneous networks, TCP connections that incorporate a terrestrial or satellite radio link are greatly disadvantaged with respect to entirely wired connections, because of their longer round trip times (RTTs). In order to cope with this problem, a new TCP proposal, the TCP Hybla, is presented and discussed in the paper. It stems from an anal...

W-CDMA and SW-CDMA air interfaces require that a user equipment in a given cell acquires slot and frame synchronization, and identifies the primary scrambling code used by the target cell before starting communications. This synchronization procedure is identified as cell search procedure in W-CDMA and beam search procedure in SW-CDMA. Notwithstand...

W-CDMA and SW-CDMA air interfaces are based on code division multiple access and as in all spread spectrum systems the initial acquisition procedure is a challenging issue. This procedure is identified as cell search in W-CDMA and beam search in SWCDMA. Although the terrestrial air interface W-CDMA and the satellite one SW-CDMA are very similar, th...

This paper explores what benefits can result from the compensation of both log-normal shadowing and Rayleigh/Rice-fading fluctuations in a mobile radio environment. The focus is on those power-control policies that exclusively make use of local power-level measurements in order to improve the performance, measured in terms of signal-to-cochannel in...

In this work the problem of code synchronization for CDMA cellular networks, such as IS-95 or cdma2000, is addressed. A multi-dwell testing procedure is adopted and optimized in multiple dimensions. The effects of correlated fading, inter-chip interference, frequency o#set, multiple-access interference, and noise are taken into account in the deter...

The problem of code synchronization for CDMA cellular networks, such as IS-95 or cdma2000, is addressed. A multi-dwell testing procedure is adopted and optimized in multiple dimensions. The effects of correlated fading, inter-chip interference, frequency offset, multiple-access interference, and noise are taken into account in the determination of...

The paper addresses the exploitation of satellite diversity in a satellite mobile network. In particular, we focus on the impact of diversity on service availability and on system capacity, considering the forward link of a CDMA system with a multisatellite and multibeam architecture. The analysis includes the effects of path blockage, intrabeam an...

Subband perceptual audio coding aims at providing the best subjective quality by decomposing the input signal into adjacent subbands. Every frequency component is then separately coded with a different number of bits in order to properly shape the quantization noise density power spectrum. In this letter, an optimum bit allocation algorithm is pres...

A new technique based on vector quantization (VQ) is proposed for interfacing the link-level and the system level analysis of frequency hopping (FH) mobile systems. The method represents an original solution to overcome the problem that the time scales adopted within the two analysis levels are usually different, thus discouraging a direct link bet...

The paper addresses the exploitation of satellite diversity in a satellite mobile network. In particular, we focus on the impact of diversity on service availability and on system capacity, considering the forward link of a CDMA system with a multi-satellite and multi-beam architecture. The analysis includes the effects of path blockage, imperfect...

The aim of this paper is to assess the complexity of different implementations of CQF (Conjugate Quadrature Mirror Filters) analysis and synthesis filter banks. In particular, we compare the classical structure based on FIR (Finite Impulse Response) filters with the alternative implementation based on binomial filters. In both cases, we describe ho...

This paper deals with the performance evaluation of a direct sequence spread-spectrum (DS-SS) system in a real indoor channel, at both 900 MHz and 60 GHz. The aim is to provide some coverage criteria for the design of an indoor wireless system. Exploiting some analytical results presented by the authors in a previous paper, the system performance i...

This work aims at evaluating the performance of a direct sequence spread-spectrum (DS-SS) system over a 60 GHz real indoor channel characterized by the presence of severe multipath. The channel has been described by 1680 impulse response data calculated by means of a 3D ray-tracing program. Both multipath components with delays shorter and longer t...

A theoretical approach to BER evaluation for a GSM-like system employing Frequency Hopping is presented, in the hypothesis of perfect interleaving and considering both hard decoding without channel information and soft decoding with perfect channel knowledge are examined. After the validation of the reliability of the proposed method by means of si...

This work explores what benefits result from tracking and compensating for both lognormal shadowing and Rayleigh fading fluctuations in a mobile radio environment. The aim is in fact to demonstrate under what circumstances this choice can be taken advantage of by those power control policies which exclusively make use of local power level measureme...

The focus of this work is on the performance analysis of a text dependent closed set speaker identification system for the Italian language. Two identification algorithms, based on LPC and LPC-cepstral feature extractors followed by a continuous density hidden Markov model (CD-HMM) classifier, have been implemented and tested on the Italian databas...

In this work we address the problem of low bit rate coding of single notes of orchestra instruments such as pianos, bass drums, snares, triangles, and cymbals, proposing a subband wavelet packet perceptual audio coder, based on a backward estimation of the perceptible signal energy, that exploits the sound characteristics to escape the transmission...

The performance of a perceptual audio coder for high quality low bit rate coding of single notes of orchestra instruments such as pianos, bass drums, snares, triangles, etc., is investigated. The coding system consists of a tree-structured perfect reconstruction filter bank with a dynamic bit allocation based on a backward estimation of the percept...

The delay locked loop tracking circuit of a typical direct sequence spread spectrum system has been analysed to find an analytical expression of the tracking error bias due to the presence of linear channel distortions, independently of their origin (for instance, due to band limitations and/or multipath propagation). Moreover, the influence of the...

Several multisatellite and multispot systems have been recently proposed for provision of mobile and personal services with global coverage, adopting GEO or non-GEO (i.e., MEO, LEO) satellite constellations. The paper addresses an in-depth analysis of these constellations, evaluating both geometrical performance measures and cochannel interference...

An EHF satellite system for land-mobile applications to be integrated with a terrestrial cellular system is described in the paper. An approach to evaluate the carrier-to-cochannel interference occurring in a multispot satellite coverage adopting frequency reuse is introduced and results from the analysis are shown. Criteria for spectrum efficiency...

The authors have previously dealt with spectral efficiency issues, discussing the problems related to their proper definition and evaluation in order to find out which aspects are relevant for comparison among different solutions and which aspects determine only the final absolute value (see 41st IEEE Vehicular Technology Conference, St. Louis, USA...

A simulation program has been carried out to further check the simplified method proposed by Immovilli and Merani (see ibid., vol.27, no.15, p.1365-7, 1991) for the analytical evaluation of outage probability in cellular mobile radio systems, due to cochannel interference and random propagation phenomena, nonselective in type. The results of the tw...