Integration of Heterogeneous Networks: Protocols, Technologies, and Applications

Today, the possibility of being connected to the Internet at every time and without interruption is almost a reality. The great capabilities of new generation cellular networks and their wide coverage enable people to use the innumerable resources of the Internet, almost everywhere and in any mobility scenario. All modern mobile devices have multiple interfaces to get connected to the Internet, and (almost) all smartphone users think to know which interface is the best one to use in a specific situation. In particular, despite the great improvement of cellular networks, in certain situations, the use of an alternative network (for instance, WiFi, is to be preferred). Therefore, the selection of the best network is not straightforward. If we change perspective and we do not talk about people and their smartphones, rather about mobile machines (say vehicles) that have to stay connected in order to provide or to receive a certain service, then the matter of finding, at every time, the best network to connect to, appears a little more urgent. Furthermore, since in some situations it could be very important to have a performing connection, for example with very low delay, then it is evident that the selection of the best network is not trivial. The characteristics of the networks to use, in order to choose the best network, are different according to the application at hand. A world where machines move automatically and use the Internet just like humans seems at the moment far away, but it is rapidly approaching. Besides the problem of network selection, one could wonder why one should just use the best network, instead of using all networks available in order to get the best "sides" of all? The development of efficient methods for the integration of multiple networks is an interesting but still open research area. This thesis focuses on the interaction and integration of heterogeneous networks. Several innovative protocols, technologies, and applications developed, in order to make network integration easier for humans and automatic for machines, will be presented

Mobility: a double-edged sword for HSPA networks

This paper presents an empirical study on the performance of mobile High Speed Packet Access (HSPA, a 3.5G cellular standard) networks in Hong Kong via extensive field tests. Our study, from the viewpoint of end users, covers virtually all possible mobile scenarios in urban areas, including subways, trains, off-shore ferries and city buses. We have confirmed that mobility has largely negative impacts on the performance of HSPA networks, as fast-changing wireless environment causes serious service deterioration or even interruption. Meanwhile our field experiment results have shown unexpected new findings and thereby exposed new features of the mobile HSPA networks, which contradict commonly held views. We surprisingly find out that mobility can improve fairness of bandwidth sharing among users and traffic flows. Also the triggering and final results of handoffs in mobile HSPA networks are unpredictable and often inappropriate, thus calling for fast reacting fallover mechanisms. We have conducted in-depth research to furnish detailed analysis and explanations to what we have observed. We conclude that mobility is a double-edged sword for HSPA networks. To the best of our knowledge, this is the first public report on a large scale empirical study on the performance of commercial mobile HSPA networks

Speedtest-Like Measurements in 3G/4G Networks: The MONROE Experience

Mobile Broadband (MBB) Networks are evolving at a fast pace, with technology enhancements that promise drastic improvements in capacity, connectivity, coverage, i.e., better performance in general. But how to measure the actual performance of a MBB solution? In this paper, we present our experience in running the simplest of the performance test: "speedtest-like" measurements to estimate the download speed offered by actual 3G/4G networks. Despite their simplicity, download speed measurements in MBB networks are much more complex than in wired networks, because of additional factors (e.g., mobility of users, physical impairments, diversity in technology, operator settings, mobile terminals diversity, etc.).,, We exploit the MONROE open platform, with hundreds of multihomed nodes scattered in 4 different countries, and explicitly designed with the goal of providing hardware and software solutions to run large scale experiments in MBB networks. We analyze datasets collected in 4 countries, over 11 operators, from about 50 nodes, for more than 2 months. After designing the experiment and instrumenting both the clients and the servers with active and passive monitoring tools, we dig into collected data, and provide insight to highlight the complexity of running even a simple speedtest. Results show interesting facts, like the occasional presence of NAT, and of Performance Enhancing Proxies (PEP), and pinpoint the impact of different network configurations that further complicate the picture. Our results will hopefully contribute to the debate about performance assessment in MBB networks, and to the definition of much needed benchmarks for performance comparisons of 3G, 4G and soon of 5G networks"

Multi-layer traffic control for wireless networks

Le reti Wireless LAN, così come definite dallo standard IEEE 802.11, garantiscono connettività senza fili nei cosiddetti “hot-spot” (aeroporti, hotel, etc.), nei campus universitari, nelle intranet aziendali e nelle abitazioni. In tali scenari, le WLAN sono denotate come “ad infrastruttura” nel senso che la copertura della rete è basata sulla presenza di un “Access Point” che fornisce alle stazioni mobili l’accesso alla rete cablata. Esiste un ulteriore approccio (chiamato “ad-hoc”) in cui le stazioni mobili appartenenti alla WLAN comunicano tra di loro senza l’ausilio dell’Access Point. Le Wireless LAN tipicamente sono connesse alla rete di trasporto (che essa sia Internet o una Intranet aziendale) usando un’infrastruttura cablata. Le reti wireless Mesh ad infrastruttura (WIMN) rappresentano un’alternativa valida e meno costosa alla classica infrastruttura cablata. A testimonianza di quanto appena affermato vi è la comparsa e la crescita sul mercato di diverse aziende specializzate nella fornitura di infrastrutture di trasporto wireless e il lancio di varie attività di standardizzazione (tra cui spicca il gruppo 802.11s). La facilità di utilizzo, di messa in opera di una rete wireless e i costi veramente ridotti hanno rappresentato fattori critici per lo straordinario successo di tale tecnologia. Di conseguenza possiamo affermare che la tecnologia wireless ha modificato lo stile di vita degli utenti, il modo di lavorare, il modo di passare il tempo libero (video conferenze, scambio foto, condivisione di brani musicali, giochi in rete, messaggistica istantanea ecc.). D’altro canto, lo sforzo per garantire lo sviluppo di reti capaci di supportare servizi dati ubiqui a velocità di trasferimento elevate è strettamente legato a numerose sfide tecniche tra cui: il supporto per l’handover tra differenti tecnologie (WLAN/3G), la certezza di accesso e autenticazione sicure, la fatturazione e l’accounting unificati, la garanzia di QoS ecc. L’attività di ricerca svolta nell’arco del Dottorato si è focalizzata sulla definizione di meccanismi multi-layer per il controllo del traffico in reti wireless. In particolare, nuove soluzioni di controllo del traffico sono state realizzate a differenti livelli della pila protocollare (dallo strato data-link allo strato applicativo) in modo da fornire: funzionalità avanzate (autenticazione sicura, differenziazione di servizio, handover trasparente) e livelli soddisfacenti di Qualità del Servizio. La maggior parte delle soluzioni proposte in questo lavoro di tesi sono state implementate in test-bed reali. Questo lavoro riporta i risultati della mia attività di ricerca ed è organizzato nel seguente modo: ogni capitolo presenta, ad uno specifico strato della pila protocollare, un meccanismo di controllo del traffico con l’obiettivo di risolvere le problematiche presentate precedentemente. I Capitoli 1 e 2 fanno riferimento allo strato di Trasporto ed investigano il problema del mantenimento della fairness per le connessioni TCP. L’unfairness TCP conduce ad una significativa degradazione delle performance implicando livelli non soddisfacenti di QoS. Questi capitoli descrivono l’attività di ricerca in cui ho impiegato il maggior impegno durante gli studi del dottorato. Nel capitolo 1 viene presentato uno studio simulativo delle problematiche di unfairness TCP e vengono introdotti due possibili soluzioni basate su rate-control. Nel Capitolo 2 viene derivato un modello analitico per la fairness TCP e si propone uno strumento per la personalizzazione delle politiche di fairness. Il capitolo 3 si focalizza sullo strato Applicativo e riporta diverse soluzioni di controllo del traffico in grado di garantire autenticazione sicura in scenari di roaming tra provider wireless. Queste soluzioni rappresentano parte integrante del framework UniWireless, un testbed nazionale sviluppato nell’ambito del progetto TWELVE. Il capitolo 4 descrive, nuovamente a strato Applicativo, una soluzione (basata su SIP) per la gestione della mobilità degli utenti in scenari di rete eterogenei ovvero quando diverse tecnologie di accesso radio sono presenti (802.11/WiFi, Bluetooth, 2.5G/3G). Infine il Capitolo 5 fa riferimento allo strato Data-Link presentando uno studio preliminare di un approccio per il routing e il load-balancing in reti Mesh infrastrutturate.Wireless LANs, as they have been defined by the IEEE 802.11 standard, are shared media enabling connectivity in the so-called “hot-spots” (airports, hotel lounges, etc.), university campuses, enterprise intranets, as well as “in-home” for home internet access. With reference to the above scenarios, WLANs are commonly denoted as “infra-structured” in the sense that WLAN coverage is based on “Access Points” which provide the mobile stations with access to the wired network. In addition to this approach, there exists also an “ad-hoc” mode to organize WLANs where mobile stations talk to each other without the need of Access Points. Wireless LANs are typically connected to the wired backbones (Internet or corporate intranets) using a wired infrastructure. Wireless Infrastructure Mesh Networks (WIMN) may represent a viable and cost-effective alternative to this traditional wired approach. This is witnessed by the emergence and growth of many companies specialized in the provisioning of wireless infrastructure solutions, as well as the launch of standardization activities (such as 802.11s). The easiness of deploying and using a wireless network, and the low deployment costs have been critical factors in the extraordinary success of such technology. As a logical consequence, the wireless technology has allowed end users being connected everywhere – every time and it has changed several things in people’s lifestyle, such as the way people work, or how they live their leisure time (videoconferencing, instant photo or music sharing, network gaming, etc.). On the other side, the effort to develop networks capable of supporting ubiquitous data services with very high data rates in strategic locations is linked with many technical challenges including seamless vertical handovers across WLAN and 3G radio technologies, security, 3G-based authentication, unified accounting and billing, consistent QoS and service provisioning, etc. My PhD research activity have been focused on multi-layer traffic control for Wireless LANs. In particular, specific new traffic control solutions have been designed at different layers of the protocol stack (from the link layer to the application layer) in order to guarantee i) advanced features (secure authentication, service differentiation, seamless handover) and ii) satisfactory level of perceived QoS. Most of the proposed solutions have been also implemented in real testbeds. This dissertation presents the results of my research activity and is organized as follows: each Chapter presents, at a specific layer of the protocol stack, a traffic control mechanism in order to address the introduced above issues. Chapter 1 and Charter 2 refer to the Transport Layer, and they investigate the problem of maintaining fairness for TCP connections. TCP unfairness may result in significant degradation of performance leading to users perceiving unsatisfactory Quality of Service. These Chapters describe the research activity in which I spent the most significant effort. Chapter 1 proposes a simulative study of the TCP fairness issues and two different solutions based on Rate Control mechanism. Chapter 2 illustrates an analytical model of the TCP fairness and derives a framework allowing wireless network providers to customize fairness policies. Chapter 3 focuses on the Application Layer and it presents new traffic control solutions able to guarantee secure authentication in wireless inter-provider roaming scenarios. These solutions are an integral part of the UniWireless framework, a nationwide distributed Open Access testbed that has been jointly realized by different research units within the TWELVE national project. Chapter 4 describes again an Application Layer solution, based on Session Initiation Protocol to manage user mobility and provide seamless mobile multimedia services in a heterogeneous scenario where different radio access technologies are used (802.11/WiFi, Bluetooth, 2.5G/3G networks). Finally Chapter 5 refers to the Data Link Layer and presents a preliminary study of a general approach for routing and load balancing in Wireless Infrastructure Mesh Network. The key idea is to dynamically select routes among a set of slowly changing alternative network paths, where paths are created through the reuse of classical 802.1Q multiple spanning tree mechanisms

Dynamic optimization of the quality of experience during mobile video watching

Mobile video consumption through streaming is becoming increasingly popular. The video parameters for an optimal quality are often automatically determined based on device and network conditions. Current mobile video services typically decide on these parameters before starting the video streaming and stick to these parameters during video playback. However in a mobile environment, conditions may change significantly during video playback. Therefore, this paper proposes a dynamic optimization of the quality taking into account real-time data regarding network, device, and user movement during video playback. The optimization method is able to change the video quality level during playback if changing conditions require this. Through a user test, the dynamic optimization is compared with a traditional, static, quality optimization method. The results showed that our optimization can improve the perceived playback and video quality, especially under varying network conditions

Efficient content-distribution in a hybrid opportunistic network

Information or content centric networking is believed by many to have great potential to be the appropriate networking paradigm for the future Internet. In information centric networking, focus is shifted from the end-points in the network to the information objects themselves, with less care being placed on from where the information is fetched. In addition to the benefits this networking paradigm has in fixed networks, it also simplifies operation in mobile networks and has the potential to improve performance. In this paper, we describe one way in which the NetInf network architecture can be used in a hybrid mobile network in an urban setting, and run simulations to evaluate the benefits that this approach can yield, both to the end users (in terms of improved performance such as reduced latency with over 50%), as well as to the operators in terms of a reduction of traffic load in the cellular access networks with up to 97%

Context-aware QoS provisioning for an M-health service platform

Inevitably, healthcare goes mobile. Recently developed mobile healthcare (i.e., m-health) services allow healthcare professionals to monitor mobile patient's vital signs and provide feedback to this patient anywhere at any time. Due to the nature of current supporting mobile service platforms, m-health services are delivered with a best-effort, i.e., there are no guarantees on the delivered Quality of Service (QoS). In this paper, we argue that the use of context information in an m-health service platform improves the delivered QoS. We give a first attempt to merge context information with a QoS-aware mobile service platform in the m-health services domain. We illustrate this with an epilepsy tele-monitoring scenario

Comparison of vertical handover decision-based techniques in heterogeneous networks

Industry leaders are currently setting out standards for 5G Networks projected for 2020 or even sooner. Future generation networks will be heterogeneous in nature because no single network type is capable of optimally meeting all the rapid changes in customer demands. Heterogeneous networks are typically characterized by some network architecture, base stations of varying transmission power, transmission solutions and the deployment of a mix of technologies (multiple radio access technologies). In heterogeneous networks, the processes involved when a mobile node successfully switches from one radio access technology to the other for the purpose of quality of service continuity is termed vertical handover or vertical handoff. Active calls that get dropped, or cases where there is discontinuity of service experienced by mobile users can be attributed to the phenomenon of delayed handover or an outright case of an unsuccessful handover procedure. This dissertation analyses the performance of a fuzzy-based VHO algorithm scheme in a Wi-Fi, WiMAX, UMTS and LTE integrated network using the OMNeT++ discrete event simulator. The loose coupling type network architecture is adopted and results of the simulation are analysed and compared for the two major categories of handover basis; multiple and single criteria based handover methods. The key performance indices from the simulations showed better overall throughput, better call dropped rate and shorter handover time duration for the multiple criteria based decision method compared to the single criteria based technique. This work also touches on current trends, challenges in area of seamless handover and initiatives for future Networks (Next Generation Heterogeneous Networks)