Differentially secure multicasting

In this age of information, the efficient use of electronic communications is essential. As technology advances and becomes more complex, it is imperative that groups be able to discuss ideas and disseminate information among members effectively. Multicast groups are established to facilitate these information transactions. Since the members of these groups may be spread across the globe, the communications must be secure as well as efficient. Secure multicasting is an active area of research today. Though the areas of secure multicast group architecture, key distribution, and sender authentication are under scrutiny, one topic that has not been explored is how to integrate these with multilevel security. Multilevel security is the ability to distinguish subjects according to classification levels, which determines to what degree they can access confidential objects. In the case of groups, this means that some members can exchange messages at a higher sensitivity level than others. The Bell-La Padula model outlines the rules of these multilevel accesses. In multicast groups that employ multilevel security, some of these rules are not desirable so a modified set of rules was developed and is termed differential security. This thesis proposes three possible methods in which to set up a differenti0y secure multicast group: a naive approach, a multiple tree differential security (DiffSec) approach, and a single DiffSec tree approach. In order to evaluate the performances (in terms of the number of links used per packet transmitted) of these approaches, extensive simulation experiments were conducted by varying the network connectivity and group size for both uniform and nonuniform membership distribution across security levels. Our studies show that the multiple tree and single DiffSec tree approaches perform much better than the naive situation. While the multiple tree approach could be implemented using current technology, this scheme consumes many times more addresses and network resources than the single DiffSec tree approach. From our studies, we conclude that the single DiffSec tree is a viable option for supporting multilevel security as it maximizes the resource utilization and is also scalable

Rate splitting in MIMO RIS-assisted systems with hardware impairments and improper signaling

In this paper, we propose an optimization framework for rate splitting (RS) techniques in multiple-input multiple-output (MIMO) reconfigurable intelligent surface (RIS)-assisted systems, possibly with I/Q imbalance (IQI). This framework can be applied to any optimization problem in which the objective and/or constraints are linear functions of the rates and/or transmit covariance matrices. Such problems include minimum-weighted and weighted-sum rate maximization, total power minimization for a target rate, minimum-weighted energy efficiency (EE) and global EE maximization. The framework may be applied to any interference-limited system with hardware impairments. For the sake of illustration, we consider a multicell MIMO RIS-assisted broadcast channel (BC) in which the base stations (BSs) and/or the users may suffer from IQI. Since IQI generates improper noise, we consider improper Gaussian signaling (IGS) as an interference-management technique that can additionally compensate for IQI. We show that RS when combined with IGS can substantially improve the spectral and energy efficiency of overloaded networks (i.e., when the number of users per cell is larger than the number of transmit/receive antennas).The work of Ignacio Santamaria has been partly supported by the project ADELE PID2019-104958RB-C43, funded by MCIN/AEI/10.13039/501100011033. The work of Eduard Jorswieck was supported in part by the Federal Ministry of Education and Research (BMBF, Germany) in the program of “Souver¨an. Digital. Vernetzt.” joint project 6G-RIC, project identification number: 16KISK020K and 16KISK031

Impulse radio ultra wideband over fiber techniques for broadband in-building network applications

In recent years, the demand for high bandwidth and mobility from the end users has been continuously growing. To satisfy this demand, broadband communication technologies that combined the benefit of both wired and wireless are considered as vital solutions. These hybrid optical wireless solutions enable multi-Gbit/s transmission as well as adequate flexibility in terms of mobility. Optical fiber is the ideal medium for such hybrid solution due its signal transparency and wide bandwidth. On the other hand, ultra wideband(UWB) radio over optical fiber technology is considered to be one of the key promising technologies for broadband communication and sensor network applications. The growing interest for UWB is mainly due to its numerous attractive features, such as low power spectral density, tolerance to multipath fading, low probability of interception, coexistence with other wireless services and capability of providing cost-effective > 1 Gb/s transmission. The main idea of UWB over fiber is to deliver UWB radio signals over optical channels, where the optical part serves as a backbone communication infrastructure to carry the UWB signal with a bandwidth of several GHz. This enables multiple novel applications such as: range extension of high speed wireless personal area networks (WPANs), low cost distributed antenna systems, secure and intelligent networks, or delivering broadband services to remote areas. In particular, this thesis deals with novel concepts on shaping and generation of IR-UWB pulses, theoretical and experimental demonstrations over different fiber types, routing of integrated wired/wireless IR-UWB services and effect of fiber types on ranging/localization of IR-UWB-over-fiber systems. Accordingly, this thesis investigates techniques for delivery of high data rate wireless services using impulse radio ultra wideband (IR-UWB) over fiber technology for both access and in-building network applications. To effectively utilize the emission mask imposed for UWB technologies by the Federal Communications Commission(FCC), novel pulse shaping techniques have been investigated and experimentally demonstrated. Comparison of the proposed pulses with conventional ones in terms of the compliance to the FCC-mask requirements, spectral power efficiencies and wireless coverage has been theoretically studied. Simple and efficient optical generation of the new pulse has been experimentally demonstrated. Furthermore, performance evaluation of 2 Gb/s transmission of IR-UWB over different types of fiber such as 25 km silica single-mode, 4.4 km silica multi-mode and 100 m plastic heavily-multi-mode fiber have been performed. To improve the functionalities of in-building networks for the delivery of wireless services; techniques that provide flexibility in terms of dynamic capacity allocation have been investigated. By employing wavelength conversion based on cross-gain modulation in optical semiconductor amplifiers(SOA), routing of three optical channels of IR-UWB over fiber system has been experimentally realized. To reduce the cost of the overall system and share the optical infrastructure, an integrated testbed for wired baseband data and wireless IR-UWB over 1 km SMF-28 fiber has been developed. Accordingly, 1.25 Gb/s wired baseband and 2 Gb/s wireless IR-UWB data have been successfully transmitted over the testbed. Furthermore, to improve the network flexibility, routing of both wired baseband and wireless signals has been demonstrated. Additionally, the ranging and localization capability of IR-UWB over fiber for in-door wireless picocells have been investigated. The effect of different fiber types (4 km SMF, 4.4 km GI-MMF and 100 m PF GI-POF) on the accuracy of the range estimation using time-of-arrival (ToA) ranging technique has been studied. A high accuracy in terms of cm level was achieved due to the combined effect of high bandwidth IR-UWB pulses, short reach fiber and low chromatic dispersion at 1300nm wavelength. Furthermore, ranging/ localization using IR-UWB over fiber system provides additional benefit of centralizing complex processing algorithms, simplifying radio access points, relaxing synchronization requirement, enabling energy-efficient and efficient traffic management networks. All the concepts, design and system experiments presented in this thesis underline the strong potential of IR-UWB for over optical fiber(silica and plastic) techniques for future smart, capacity and energy-efficient broadband in-building network applications

Up-to-the-Minute Privacy Policies via Gossips in Participatory Epidemiological Studies

Researchers and researched populations are actively involved in participatory epidemiology. Such studies collect many details about an individual. Recent developments in statistical inferences can lead to sensitive information leaks from seemingly insensitive data about individuals. Typical safeguarding mechanisms are vetted by ethics committees; however, the attack models are constantly evolving. Newly discovered threats, change in applicable laws or an individual's perception can raise concerns that affect the study. Addressing these concerns is imperative to maintain trust with the researched population. We are implementing Lohpi: an infrastructure for building accountability in data processing for participatory epidemiology. We address the challenge of data-ownership by allowing institutions to host data on their managed servers while being part of Lohpi. We update data access policies using gossips. We present Lohpi as a novel architecture for research data processing and evaluate the dissemination, overhead, and fault-tolerance

A multicast overlay scheme for wavelength division multiplexed passive optical networks.

Zhang, Yin.Thesis submitted in: December 2008.Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.Includes bibliographical references (leaves 56-60).Abstracts in English and Chinese.Chapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Telecommunications network hierarchy --- p.2Chapter 1.2 --- PON architectures for access networks --- p.4Chapter 1.2.1 --- TDM-PON --- p.5Chapter 1.2.2 --- WDM-PON --- p.7Chapter 1.3 --- Data delivery mode in WDM-PON --- p.8Chapter 1.3.1 --- Point-to-point --- p.8Chapter 1.3.2 --- Broadcast --- p.9Chapter 1.3.3 --- Multicast --- p.10Chapter 1.4 --- Motivation of this thesis --- p.10Chapter 1.5 --- Outline of this thesis --- p.13Chapter Chapter 2 --- Previous Multicast Architectures in WDM-PON --- p.14Chapter 2.1 --- Introduction --- p.15Chapter 2.2 --- Previous WDM-PON architectures with multicast capability --- p.15Chapter 2.2.1 --- Subcarrier multiplexing --- p.16Chapter 2.2.2 --- All-optical based multicast enabled architecture --- p.18Chapter 2.3 --- Summary --- p.21Chapter Chapter 3 --- A Multicast enabled WDM-PON Architecture Using ASK-DPSK Orthogonal Modulation --- p.23Chapter 3.1 --- Introduction --- p.24Chapter 3.2 --- System architecture --- p.25Chapter 3.3 --- Experimental Demonstration --- p.27Chapter 3.4 --- Discussion --- p.31Chapter 3.5 --- Summary --- p.36Chapter Chapter 4 --- A WG filtering and its suppression in quaternary ASK-DPSK based multicast enabled WDM-PON --- p.37Chapter 4.1 --- Introduction --- p.38Chapter 4.2 --- Principle of narrowband filtering --- p.38Chapter 4.3 --- Simulation model --- p.40Chapter 4.4 --- Simulation results and discussion --- p.42Chapter 4.4.1 --- Different extinction ratios --- p.43Chapter 4.4.2 --- Different AWG filter shape and bandwidth --- p.47Chapter 4.5 --- Summary --- p.50Chapter Chapter 5 --- Summary and Future Works --- p.51Chapter 5.1 --- Summary of the thesis --- p.52Chapter 5.2 --- Future works --- p.53List of Publications --- p.55BIBLIOGRAPHY --- p.5

A manifesto for future generation cloud computing: research directions for the next decade

The Cloud computing paradigm has revolutionised the computer science horizon during the past decade and has enabled the emergence of computing as the fifth utility. It has captured significant attention of academia, industries, and government bodies. Now, it has emerged as the backbone of modern economy by offering subscription-based services anytime, anywhere following a pay-as-you-go model. This has instigated (1) shorter establishment times for start-ups, (2) creation of scalable global enterprise applications, (3) better cost-to-value associativity for scientific and high performance computing applications, and (4) different invocation/execution models for pervasive and ubiquitous applications. The recent technological developments and paradigms such as serverless computing, software-defined networking, Internet of Things, and processing at network edge are creating new opportunities for Cloud computing. However, they are also posing several new challenges and creating the need for new approaches and research strategies, as well as the re-evaluation of the models that were developed to address issues such as scalability, elasticity, reliability, security, sustainability, and application models. The proposed manifesto addresses them by identifying the major open challenges in Cloud computing, emerging trends, and impact areas. It then offers research directions for the next decade, thus helping in the realisation of Future Generation Cloud Computing

Power, Policy, and Digital Switchover: An Analysis of Communication Policy Making and its Challenges for Regulating Ghana’s Digital Television Sector

This thesis examines communication policy making in Ghana during the country’s digital switchover process launched in 2010. The thesis argues that Ghana’s digital switchover policy making process was an opportunity to refashion policy and regulatory structures towards the public interest that went beyond the modernisation of broadcasting transmission infrastructure and the innovations digital switchover brought. The thesis investigates whether, and the extent to which, structural and institutional characteristics in the communication policy arena facilitated or hindered broadcasting policy making, and explains the persistence of the analogue era broadcasting regulatory regime in the digital multichannel television market. Ghana’s return to Constitutional rule since 1992 led to the liberalisation of the broadcasting sector, permitting private ownership of broadcast media for the first time in the country’s history, as well as the reconfiguration of the communication policy making arena (and the wider policy environment), with more actors engaged in policy making. Yet, the manner in which this was achieved sustained the capability of state policy actors in the communication sector to influence the shape, pace and direction of policy due to the concentration of power within the Executive that granted the government excessive power. The thesis draws on political science and sociological concepts and approaches to analyse original qualitative data based on extensive documentary analysis and elite interviews with policy actors, during Ghana’s digital switchover policy making process from 2010. The study finds that political events during Ghana’s transition to Constitutional rule in the early 1990s, after ten years of military autocratic rule was the critical juncture that laid the foundation for a path-dependent communication policy making trajectory. Overtime this has produced a fractured and uncoordinated broadcasting policy making context whereby policy makers act without much consideration for the wider interest of the sector, whilst non-state policy actors remain ineffective to sustain advocacy that would serve the public interest. This played out during Ghana’s digital switchover process as the dominance of state-controlled policy actors ensured the framing of domestic digital switchover policy objectives along narrow externally set priorities at the expense of longstanding and pertinent broadcasting policy and regulatory concerns that could have been part of the country’s digital switchover policy making agenda. The study maintains that as the full implications of the digital switchover process on Ghana’s broadcasting sector becomes apparent, the continued lack of an adequate policy and regulatory framework for the new digital television broadcasting market, and, indeed the larger broadcasting sector, does not serve the public interest and as such, it impoverishes the broadcasting service available to citizens