4G mobile networks were the first to allow packet-switched voice calls, supported by an optional IP-based infrastructure called IP Multimedia Subsystem (IMS). These are part of the Voice over Long Term Evolution (VoLTE) service, called afterward Voice over New Radio (VoNR) in 5G. In parallel, 3GPP defined the possibility of user terminals accessing either a 4G Evolved Packet Core (EPC) or a 5G Core (5GC) Network also via non-3GPP access. Non-3GPP access represents an alternative to the use of 4G/5G licensed frequencies of the MNO, leveraging Internet connectivity of an Internet Service Provider (ISP) to perform the same IP-based 4G/5G services, and in particular VoLTE/VoNR. Although, especially for untrusted non-3GPP access, any IP-based access technology is applicable, the initial reference is Wi-Fi access, which is available in practice in all smartphones. Consequently, the new 3GPP Voice over Wi-Fi (VoWiFi) service was introduced, also called commercially Wi-Fi Calling. VoWiFi is then subject to network conditions not fully under the control of the Mobile Network Operator (MNO), not only related to Wi-Fi access, but also to the whole end-to-end data path across shared networks and the Internet. In this article, the VoWiFi technology and protocols are presented in detail, through a review of 3GPP specifications and by performing real calls using a national LTE MNO and a Xiaomi smartphone. The purpose of the article is to present the application traffic pattern and to assess the network conditions under which VoWiFi calls are of good quality. These results are useful to define end-to-end Network requirements for assuring a satisfactory VoWiFi service to end users.

In a 5G System (5GS), in addition to the standard 3GPP Access via a gNodeB (Radio Access Network (RAN)), there is the possibility to access 5G services also via alternative access networks with the use of dedicated inter-working gateways, such as the Non-3GPP Inter-Working Function (N3IWF). In this alternative type of access, defined as Non-3GPP access, the User Equipment (UE) can establish a 5G compliant data connection, for instance via Wi-Fi, to the 5G Core (5GC) Network. Furthermore, Non-3GPP access can represent a gapfiller for the use of Non-Terrestrial Network (NTN)-based access, which is often non-3GPP as of today, to a 5GC Network. Non3GPP access to a 5GC is useful to enhance coverage in underserved areas (rural, off-shore, in flight, indoor, etc.), as well as enabling compelling use-cases deploying Non Public Networks (NPN) leveraging unlicensed Wi-Fi access, including possible backhaul connectivity via, e.g., Satellite. In this context, we propose an innovative approach to offer part of the 5G services via Local Edge Services (LES), directly hosted and handled by the N3IWF component. Even if this approach is outside the scope of present 3GPP specifications, it can be beneficial in several use cases by serving directly the contents next to the users. To prove the feasibility of this approach, we present in this paper a real-time demonstrator implementing with success the LES component in an end-to-end realistic 5GS deployment, using emulated UEs, a custom N3IWF implementation and a commercial 5GC.

Web-based services have nowadays aggregated the majority of applications, ranging from multimedia delivery to instant messaging, embracing requirements from different classes of users (i.e., gamers, streamers, professionals, etc.). The common factor is the need for connectivity everywhere and every time at high performance and quality, while the services traffic profiles and the users' behaviour can be drastically different. This need is fully satisfied by the recent 5G mobile networks, where the coexistence of heterogeneous applications with different Quality of Service (QoS) levels is possible, defining new vertical markets and cutting-edge applications. In this context, we propose a Flexible Web Traffic Generator (FWTG) tool to model the dynamics of recent applications and user interactions in a realistic way, allowing the generation of real-time HTTP traffic and the possibility to inject it into real networks. FTWG represents a valid in-laboratory solution for the rapid configuration and applications performance evaluation of network slices in the context of 5G Non-Public Networks (NPN), pursuing an effective emulation approach. The advantage of this approach is that it allows the evaluation of real traffic response to different network configurations (and vice-versa), using components, equipment and network functions of the target network under test. After the description of the rationale and the methodology for defining FWTG models and their implementation, we defined a set of Key Performance Indicators (KPI) generated by the tool (e.g., number of requested objects and size, request rate, throughput, etc.). Then, we present initial validation tests on a Linux-based testbed representing the 5G-based scenarios of interest, emulating also a satellite backhaul as representative of a use-case requiring cost-effective dimensioning. Numerical outcomes of running FWTG in different configurations are then provided, considering a variation of the number of users sharing the same resources, their composition and traffic type, showing with concrete examples the usefulness and flexibility of FWTG in supporting 5G network configuration optimizations. Definitively, the tool is released as Open Source software on Gitlab.

The design and implementation of an efficient end-to-end IP-based infrastructure for the delivery of multimedia content is of paramount importance in current public networks, dominated by the constant growth of video streaming traffic. Content Delivery Networks (CDNs) represent the main technological solution to manage the huge volumes of traffic involved, by guaranteeing high quality levels to applications and low impact to the core networks, thanks to the efficient distribution of content among edge caches that are located as close as possible to end-users. Nonetheless, the hierarchical data distribution associated with CDNs can be in principle subject to inefficiencies, as well as performance limitations in case of congested segments along the end-to-end delivery path. In this context, we propose the exploitation of satellite multicast capabilities offered by modern high throughput satellite (HTS) platforms, in a virtualized-compatible model, to compensate for flaws of terrestrial networks . The role of satellite communication is to offer multicast support (as a complement to landline connectivity) with wide geographical service areas based on the available satellite beams, enabling a popularity-based content distribution support. In addition, multi-beam satellite technology allows for a more fine-grained approach to popularity evaluation based on user location. The proposed service and the related network configuration are described in the paper, in relation with current and future SatCom platforms. We then present the results of the proposed CDN caching algorithms in a simulated environment, showing promising results associated with a preliminary performance evaluation.

5G is a cornerstone in the evolution of mobile communication networks, representing the most advanced and available standard at the state of art. Characterized by higher data rate and capacity, actually the real revolution of 5G relies in its capability to offer advanced and heterogeneous services by the full abstraction and slicing of network resources, realizing a service-oriented full-IP high-performance network over a common infrastructure, even belonging to different operators. Another key aspect, which is specifically addressed in this paper, is the possibility to access the services offered by the 5G network using non-3GPP access, and in particular Wi-Fi. This feature can allow access from home Access Points or using public Hotspots, even where there is no 5G coverage or roaming. At the same time, other types of IP access, including terrestrial wired options, are allowed by 3GPP specifications. Such a flexibility allows, although not explicitly mentioned, to consider as well satellite-based non-3GPP access methods, thus enabling wide-coverage use-cases and rural areas coverage. In the paper we discuss the network function required to enable non-3GPP access to 5G Core Networks, namely N3IWF, and the impact in using as access network a VSAT satellite link. After a focus on protocol stacks and signalling procedures, we implemented such an access on a real time Linux testbed including a 5G rel. 15 compliant Core Network, a N3IWF network function and a satellite emulation to assess control procedures timings, User plane latency and overhead.

TCP Wave relies on a disruptive communication paradigm based on bursts, to overcome limitations of legacy TCP with modern applications and challenging network scenarios. This protocol was already validated with appealing results via simulations. This work now presents its implementation in the Linux kernel, focusing on the adaptations needed to deal with real networking systems. A Linux implementation paves the way to validate the protocol algorithms and working principles on real communication environments, thus drawing its operational perimeter. In this regard, the most ambitious goal is to show the bright side of the burst transmission as a novel opportunity for performance optimization in the future Internet connectivity scenarios. TCP Wave performance is therefore compared with reference TCP congestion schemes currently included in the Linux kernel, namely BBR and Cubic, under a large set of network configurations. A vast gamut of performance indicators are presented and discussed, including throughput, latency, fairness, friendliness, loss management and reaction to network and traffic changes. Definitely, this paper is a manifest for the real TCP Wave implementation in Linux, which can act as reference for future works.

Video streaming today shows a widespread success, representing already the greatest portion of the Internet's IP traffic. The most common approach in today's networks is to adopt HTTP-based solutions, such as the Dynamic Adaptive Streaming over HTTP (DASH) protocol. This choice allows using general purpose web clients (web browsers) to access video streaming, while implementing a client-side dynamic rate adaptation of the streaming service. In fact, such HTTP-based approach must cope with intrinsic dynamism of the client's access network, which is a function of concurrent traffic from either the same user or other users sharing the same network resources. In addition, the network virtualization era fosters dynamic management of virtual resources that can lead to even further network variability, with significant changes of the end-to-end link characteristics in terms of bottleneck bandwidth and physical delay. Last but not least, the fruitful utilization of the satellite component in the future 5G networks implies to experience physical delay changes over a larger value range. Therefore, DASH flows will run on communication scenarios with higher and higher variability: this means that the client-side dynamic adaptation feature of DASH becomes a critical component of the whole service. This paper aims to investigate performance of two main DASH Adaptive Bit Rate (ABR) algorithm categories, throughput-based and buffer-based, over a simulated time-varying end-to-end link modeling the joint effects of continuous traffic and link changes. The goal is to provide statistical overview on the DASH ABR adaptation on challenging scenarios in order to draw some baseline recommendations for possible enhancements or modifications. The overall performance analysis is based on a customized script running in the Network Simulator 3 (NS-3).

Network Function Virtualization (NFV) allows a fast deployment of customized solutions when and where needed, supporting breakthrough operational models compliant to multi-tenancy and slicing paradigms. This approach enables challenging communication scenarios overcoming possible performance flaws as well as enabling new disruptive services within future 5G based networks. In this framework a virtual Performance Enhancing Proxy (vPEP) is proposed, to foster the efficient use of satellite links either as a supplementary or complementary backhauling. The vPEP objective is to efficiently manage both switch-over (for performance optimization) and failover (for service continuity) of end-to-end Web traffic within an hybrid terrestrial/satellite backhaul network. To this aim, vPEP leverages several features of the new QUIC protocol, such as the 0-RTT establishment of secure communications and the connection-oriented flow management over a UDP-based connectionless transport. In this paper we describe the vPEP implementation as well as a Proof-of-Concept (PoC) demonstrator used for the validation activities.

The availability of multiple technologies to access the Internet is even more common in today's connectivity scenarios. As an example, smartphones make use of 3G/4G data technology but, when a Wi-Fi access point is available, they switch from 3G/4G (which typically is a paid per volume service) to the wireless local access. The same principle is applicable for fixed access, when terrestrial ADSL or optical fiber and satellite technologies can be typically available in the same place. This paper focuses on the simultaneous availability of different access technologies with the capability to use them in combination, to offer better performance than the traditional single technology access.

The 5G standardization activities are going to be finalized. The full set of specifications for the next generation telecommunication systems, which will be based on flexible network management and new services definition, is expected for mid 2018 (release 15) and for mid 2019 (release 16). At the same time, High Throughput Satellite (HTS) platforms faced a wide adoption for the provision of Internet access and are recently gaining a significant interest as complementary connectivity able to support 5G architectures, leading to significant investments for the development and deployment of future platforms. In the view of a synergy between terrestrial and satellite networks to provide 5G services, the satellite access can play a meaningful role to support/complement terrestrial networks for its peculiar characteristics of coverage, broadcasting/multicasting, synchronization, etc. To this aim, the system availability and bandwidths available must be carefully assessed when the hybrid network is tailored to specific 5G services. The Athena Fidus system has been realized to support civil and governmental services and is today operational. In this paper, the characteristics of Athena Fidus DVB-S2/DVB-RCS links are considered to identify the set of services that will be possible to offer, focusing on nominal IP-based bandwidth and availability. The objective is to draw the operational context to be considered for the potential utilization of Athena Fidus in the next communication systems.

In the definition of advanced 5G scenarios, one of the possible configurations including the satellite link is to consider it to provide a supplementary capacity to enhance backhauling towards data networks. The peculiar satellite physical characteristics and the resulting challenging communication environment (i.e., large propagation delays, possible losses, etc.) are usually tackled with the introduction of Performance Enhancing Proxies (PEPs) agents aimed to improve performance. In this regard, 5G offers the cutting-edge capability to exploit virtualization and slicing concepts, so that PEP can be implemented as a set of Virtualized Network Functions (VNFs) to be dynamically deployed into the network responding to the specific requirement of the target service slice. In this paper we discuss this approach, validated in the frame of an European Space Agency (ESA) project, where a hybrid terrestrial-satellite backhaul is envisaged to enhance performance and system. In particular, we present a QUIC proxy as distributed VNFs aimed to efficiently manage the hybrid link allowing an efficient failover in case of terrestrial link outage or unavailability.

The exploitation of Internet services leveraging multiple and different access links simultaneously is becoming a compelling use-case in current networks and upcoming 5G scenarios. In fact, recent network architectures and technologies enable multi-link access with the aim to improve both performance and service resilience/reliability. Performance improvement mainly concerns the increase of physical bandwidth through the “bonding” of multiple links, whereas reliability comes from the opportunity to implement handover and failover procedures over multiple links. At the transport layer, MP-TCP protocol was introduced as response to these needs to efficiently work on multiple links. Nonetheless, when one of the links in use is satellite (being very different in characteristics with regard to terrestrial links), it is possible to reach sub-optimal performance. The scope of the paper is to show in depth the working principles of MP-TCP before addressing, in such challenging environment, the impact of different network configurations by using a real Linux-based testbed. The results obtained can be considered as useful recommendations to future Internet Service Providers for their network configuration.

We present the design and implementation aspects of a virtualized Performance Enhancing Proxy (vPEP), in a 5G compliant architecture involving the satellite as an alternate, additional backhaul link. The deployment of hybrid terrestrialsatellite configurations is realized through the vPEP agent, meant as a chain of Virtual Network Functions (VNFs), enhancing protocol performance and/or bringing value-added services in the end-to-end path. To this end, we discuss a possible integration approach of the satellite link into the 5G service-based architecture, outlining key functional components. In addition, we present a preliminary evaluation study employing a vPEP embodying the QUIC protocol in a possible web-browsing, 5G optimized slice.

TCP Wave changes the typical TCP transmission paradigm by replacing the ACK-clocked sliding window with self-scheduled bursts. In response to bursts, unmodified TCP receivers generate ACK trains, which carry useful information about the end-to-end link characteristics. TCP Wave inspects ACK-train flow to measure the following parameters: (i) ACK train spread (namely ACK train dispersion) and (ii) RTT variations. The former is expected to provide the overall "service capacity", meant as the maximum capacity allowed over the end-to-end path, while the latter is considered as a congestion indicator. The joint use of such measurements allows TCP Wave to fine-tune the transmission rate to accurately match current network resource availability in the bottleneck link. This paper analysis TCP Wave ACK train-based measurements on a broad set of simulated links compliant to characteristics of today's real networks. To this scope, a testbed with TCP Wave implementation on Linux OS is used to perform tests varying both bottleneck capacity and physical latency.

Contention Resolution Diversity Slotted ALOHA (CRDSA) random access scheme, introduced in the DVB-RCS2/NG standard, is specifically designed to support the transfer of a variety of traffic profiles that Machine to Machine (M2M) and Internet of Things (IoT) applications may generate. Protocols for M2M and IoT has recently receiver substantial upgrades, but still mainly designed with an underlying terrestrial network in mind. If clusters of sensor nodes exchange data via satellite terminals toward a sink via short-lived TCP/IP connections, many shortcomings may incur. This work aims at investigating in details the behavior for such data transfer in presence of a shared random access channel, and the advantages when using a new TCP version specifically designed for satellite links, namely TCP Wave. In particular, through a detailed simulation campaign based on the NS3 simulator, this work assesses the completion time of data delivery for M2M elastic traffic via CRDSA satellite random access, when standard TCP (NewReno) or dedicated satellite TCP (Wave) is adopted.

Telecommunication networks are complex systems in term of design, development, management and maintenance. The degree of complexity greatly increases when the network is composed of several segments adopting different technologies and standards, as well as the sharing of common resources. Development of suitable models of networking and their implementation using simulation and emulation tools are of paramount importance to address such a complexity in a laboratory-controlled environment. To tackle different aspects of satellite and terrestrial integrated networks, which cover different protocol layers and technology standards, different simulative or emulative approaches are possible. A presentation and selection of simulation and emulation tools is presented in this paper, followed by the description of results obtainable with the selected tools in some explicative study-cases.

New High Throughput Satellite (HTS) systems allow high throughput IP uplinks/contribution at Ka-band frequencies for relatively lower costs when compared to broadcasting satellite uplinks at Ku band. This technology offers an advantage for live video contribution from remote areas, where the terrestrial infrastructure may not be adequate. On the other hand, the Ka-band is more subject to impairments due to rain or bad weather. This paper addresses the target system specification and provides an optimized approach for the transmission of IP-based video flows through HTS commercial services operating at Ka-band frequencies. In particular, the focus of this study is on the service requirements and the propagation analysis that provide a reference architecture to improve the overall link availability. The approach proposed herein leads to the introduction of a new concept of live service contribution using pairs of small satellite antennas and cheap satellite terminals.

TCP Wave is an innovative transport protocol adopting a burst-based transmission approach, instead of the traditional window-based one. In TCP Wave the underlying IP packet transmission process results completely changed because of an internal timer to schedule bursts, which replaces the ACK-clocked transmission of all TCP versions. So far, TCP Wave capabilities have been assessed in a large gamut of scenarios but mainly limited to unidirectional bulk-like transfers involving a TCP sender and a TCP receiver. In this paper, TCP Wave behavior and performance are evaluated for the first time with real HTTP running applications, which are characterized by: a request/response interactive traffic model, a short and, in some cases, spaced objects transmissions and a mutual role of TCP peers that can act either as sender or receiver according to the application operations. TCP Wave procedures were accurately adapted to be suitable in this scenario and will be described in details. Finally, ns-3 simulator was setup and test campaign was performed, including both a real Web server and an HTTP client.

The paper describes the project “Integrated technologies for fire monitoring and first alert” proposed by the authors to satisfy technical requirements of the Firefighter Bodies with particular attention to the monitoring of wood fires and release of chemical materials. The target system is composed of three sub-systems: sensors to detect target parameters, telecommunications to transfer sensor data in real time and for first alert management, fire evolution real time simulator to support decisions. The project aims also to integrate the three subsystems facing and solving technical/scientific issues to provide a significant applicative high value.

After a shipwreck people wear life vest and the available telecommunication systems for rescue operations offer, in the best case, just approximate localization of relicts or lifeboats. A communication system tailored to provide a reliable and real time updated map of positions and health conditions of floating people can improve efficiency of rescue operation. The aim of the SMARTSOS system is to introduce the capability for each person, equipped with GPS receiver and health sensors, to send information at low cost to a remote location, maximizing delivery probability and quality of service, ensuring also data integrity. Each life vest will be equipped with a terminal able to exchange data only with other life vest terminals; a subset of all life vests (masters) will be equipped also with very small Low Earth Orbit (LEO) or GEO satellite terminal to provide long range connectivity; the space segment and the remote service center will complete the architecture. To maximize message delivery probability and to limit power we propose a joint exploitation of linear Network Coding and a store-and-forward mechanism. Each node overhears broadcast communications of neighbors, gathers messages and code them with its own message to rebroadcast the result with an uncoded copy of its message. On the other side, the rescue team will get the position grid and health information of shipwrecked people, planning operations accordingly. The paper describes the system architecture and a project that will include the design of the Network Coding scheme and its validation via simulations and trials with prototypes.