An analytical model for optimal spectrum leasing under constraints of quality of service in CRNs

Cognitive radio improves spectrum efficiency and mitigates spectrum scarcity by allowing cognitive users to opportunistically access idle chunks of the spectrum owned by licensed users. In long-term spectrum leasing markets, secondary network operators make a decision about how much spectrum is optimal to fulfill their users' data transmission requirements. We study this optimization problem in multiple channel scenarios. Under the constrains of expected user admission rate and quality of service, we model the secondary network into a dynamic data transportation system. In this system, the spectrum accesses of both primary users and secondary users are in accordance with stochastic processes, respectively. The main metrics of quality of service we are concerned with include user admission rate, average transmission delay and stability of the delay. To quantify the relationship between spectrum provisioning and quality of service, we propose an approximate analytical model. We use the model to estimate the lower and upper bounds of the optimal amount of the spectrum. The distance between the bounds is relatively narrow. In addition, we design a simple algorithm to compute the optimum by using the bounds. We conduct numerical simulations on a slotted multiple channel dynamic spectrum access network model. Simulation results demonstrate the preciseness of the proposed model. Our work sheds light on the design of game and auction based dynamic spectrum sharing mechanisms in cognitive radio networks.

A distributed gateway selection algorithm for UAV networks

In recent years, unmanned aerial vehicle (UAV) has been widely adopted in military and civilian applications. For small UAVs, cooperation based on communication networks can effectively expand their working area. Although the UAV networks are quite similar to the traditional mobile ad hoc networks, the special characteristics of the UAV application scenario have not been considered in the literature. In this paper, we propose a distributed gateway selection algorithm with dynamic network partition by taking into account the application characteristics of UAV networks. In the proposed algorithm, the influence of the asymmetry information phenomenon on UAVs' topology control is weakened by dividing the network into several subareas. During the operation of the network, the partition of the network can be adaptively adjusted to keep the whole network topology stable even though UAVs are moving rapidly. Meanwhile, the number of gateways can be completely controlled according to the system requirements. In particular, we define the stability of UAV networks, build a network partition model, and design a distributed gateway selection algorithm. Simulation results show using our proposed scheme that the faster the nodes move in the network, the more stable topology can be found, which is quite suitable for UAV applications.

Opportunistic offloading of deadline-constrained bulk cellular traffic in vehicular DTNs

The ever-growing cellular traffic demand has laid a heavy burden on cellular networks. The recent rapid development in vehicle-to-vehicle communication techniques makes vehicular delay-tolerant network (VDTN) an attractive candidate for traffic offloading from cellular networks. In this paper, we study a bulk traffic offloading problem with the goal of minimizing the cellular communication cost under the constraint that all the subscribers receive their desired whole content before it expires. It needs to determine the initial offloading points and the dissemination scheme for offloaded traffic in a VDTN. By novelly describing the content delivery process via a contact-based flow model, we formulate the problem in a linear programming (LP) form, based on which an online offloading scheme is proposed to deal with the network dynamics (e.g., vehicle arrival/departure). Furthermore, an offline LP-based
analysis is derived to obtain the optimal solution. The high efficiency of our online algorithm is extensively validated by simulation results.

Building G20 outreach: The role of transnational policy networks in sustaining effective and legitimate summitry

G20 outreach processes, in the form of the Think 20, Labour 20, Business 20, and Civil 20, Youth 20, and Women 20, are a formal attempt by G20 leaders to engage various social sectors with G20 policymaking. This essay contends that G20 outreach processes are best understood as transnational policy networks, which are involved in widening the field of policy communication and deliberation. The importance of these transnational policy networks rest upon their role in developing and disseminating G20 policy priorities and principles; and are an attempt to enhance the legitimacy and influence of the G20 and its policy proposals.

"We agree that, in order to strengthen its ability to build and sustain the political consensus needed to respond to challenges, the G20 must remain efficient, transparent and accountable. To achieve this, we decide to … pursue consistent and effective engagement with non-members, regional and international organisations, including the United Nations, and other actors, and we welcome their contribution to our work as appropriate. We also encourage engagement with civil society.G20 Cannes Summit Final Declaration 2011 (G20 2011)"

The difficulty in balancing the effectiveness and representativeness of the Group of Twenty (G20) has led to sustained questions about its legitimacy (Cooper 2010; Rudd 2011; Cooper and Pouliot 2015). Consequently, while leaders have long sought external advice about the agendas of Group of Seven (G7) summits since 1975, and about the G20 finance ministers and central bank governors’ meetings (G20 FM/CBG) since 1999, there has been intensification, elaboration, and institutionalization of transnational networks of policymakers with respect to the G20 in recent years. These networks are especially evident in the form of the G20 working groups and G20 outreach processes involved in the G20 FM/CBG and the G20 leaders’ forum created in 2008.

G20 working groups include transgovernmental groups of government officials and outside experts within a specific policy area who are charged with preparing material for G20 deliberations. G20 outreach processes are a recent and more formal attempt by G20 leaders to engage various social sectors with the policymaking activity of the G20 and were first considered by the G20 membership in 2010 with a more formal engagement with business interests. This led to the formal development of G20 outreach groups in 2013 in the form of the Think 20 (think tanks), Labour 20, Business 20, Civil 20 and Youth 20, which include representatives from these sectors. In 2015, a Women 20 outreach group was also added. These outreach processes are best understood as transnational policy networks which have been built to support the G20’s capacity to be effective and legitimate.

This essay focuses on G20 outreach processes and examines why and how the G20 has sought to augment its intergovernmental summitry and transgovernmental working groups with transnational policy networks, purposely involving a range of societal interests. Transnational policy networks demonstrate the existence of policymaking practices which include the policy influence of experts and advocates outside government. These networks also indicate the ways in which governments, International Governmental Organizations (IGOs) and summits like the G20 engage society, or where elements of society engage themselves with the policymaking process (Stone 2008). These networks intersect with the intergovernmental activities of leaders and key diplomats, and overlap with the transgovernmental relationships of various levels of government bureaucrats (Baker 2009). One of the principle features of transnational policy networks is the way they create and channel the communication of political ideas and priorities. However, it is important to keep in the mind the purpose and power of actors involved in the network and consider who has the discretion and motivation to create the network in the first instance. As the G20 members stated in 2012, the aspiration for outreach is founded upon an intent to strengthen the G20’s capacity “to build and sustain the political consensus”. Consequently, it is important to consider how the development of transnational policy networks in the form of G20 outreach processes are able to sustain the effectiveness and legitimacy of the G20.

This essay contends that G20 outreach processes are best understood as transnational policy networks. These networks have been built to widen the field of policy communication and deliberation. Furthermore, these outreach processes and networks are an attempt to enhance the legitimacy and influence of the G20 and its policy proposals. While there is no doubt that outreach practices are “ad hoc responses to the widespread charge that the G20 reproduces the politics of exclusion in global governance” (Cooper and Pouliot 2015, 347), these practices have the potential to improve both the effectiveness and legitimacy of the G20. The G20 possesses uncertain legitimacy and members of the G20 demonstrate an awareness of this and a corresponding willingness to actively develop various political practices to support the capacity and legitimacy of the G20.

However, G20 outreach also enables the G20 to place some limit upon the policy narratives and ideas that develop within these policy networks. The G20 is liable to be misunderstood without examining the activity of these transnational networks because the G20 is fundamentally a deliberative policy forum rather than a negotiating forum of binding regulations. Transnational policy networks have the potential to scrutinize and amplify relevant policy ideas and thereby enhance the legitimacy of the G20 and strengthen the capacity of the G20 to address an array of global economic and social problems. However, while some narrative control is important to amplify the G20 agenda, too much narrative control will undermine its legitimacy and capacity to develop broad-based responses to global problems. This essay explores the formation of these transnational policy networks by first outlining the evolution of the purpose and configuration of the G20, then it considers the ways G20 outreach processes constitute transnational policy networks and why they have been established, and lastly, analyses how these networks operate to enhance the legitimacy and effectiveness of the G20.

Trust, security and privacy in emerging distributed systems FGCS

The rapid development and increasing complexity of computer systems and communication networks coupled with the proliferation of services and applications in both Internet-based and ad-hoc based environments have brought network and system security issues to the fore. We have been witnessing ever-increasing cyber attacks on the network and system leading to tarnished confidence and trusts in the use of networked distributed systems. As a result, there is an increasing demand for development of new trust, security and privacy approaches to guarantee the privacy, integrity, and availability of resources in networked distributed systems.

On the race of worms and patches: modeling the spread of information in wireless sensor networks

Sensor networks are a branch of distributed ad hoc networks with a broad range of applications in surveillance and environment monitoring. In these networks, message exchanges are carried out in a multi-hop manner. Due to resource constraints, security professionals often use lightweight protocols, which do not provide adequate security. Even in the absence of constraints, designing a foolproof set of protocols and codes is almost impossible. This leaves the door open to the worms that take advantage of the vulnerabilities to propagate via exploiting the multi-hop message exchange mechanism. This issue has drawn the attention of security researchers recently. In this paper, we investigate the propagation pattern of information in wireless sensor networks based on an extended theory of epidemiology. We develop a geographical susceptible-infective model for this purpose and analytically derive the dynamics of information propagation. Compared with the previous models, ours is more realistic and is distinguished by two key factors that had been neglected before: 1) the proposed model does not purely rely on epidemic theory but rather binds it with geometrical and spatial constraints of real-world sensor networks and 2) it extends to also model the spread dynamics of conflicting information (e.g., a worm and its patch). We do extensive simulations to show the accuracy of our model and compare it with the previous ones. The findings show the common intuition that the infection source is the best location to start patching from, which is not necessarily right. We show that this depends on many factors, including the time it takes for the patch to be developed, worm/patch characteristics as well as the shape of the network.