Interconnected Communication Networks Research Articles

Network Creation Games with Traceroute-Based Strategies

Network creation games have been extensively used as mathematical models to capture the key aspects of the decentralized process that leads to the formation of interconnected communication networks by selfish agents. In these games, each user of the network is identified by a node and selects which link to activate by strategically balancing his/her building cost with his/her usage cost (which is a function of the distances towards the other player in the network to be built). In these games, a widespread assumption is that players have a common and complete information about the evolving network topology. This is only realistic for small-scale networks as, when the network size grows, it quickly becomes impractical for the single users to gather such a global and fine-grained knowledge of the network in which they are embedded. In this work, we weaken this assumption, by only allowing players to have a partial view of the network. To this aim, we borrow three popular traceroute-based knowledge models used in network discovery: (i) distance vector, (ii) shortest-path tree view, and (iii) layered view. We settle many of the classical game theoretic questions in all of the above models. More precisely, we introduce a suitable (and unifying) equilibrium concept which we then use to study the convergence of improving and best response dynamics, the computational complexity of computing a best response, and to provide matching upper and lower bounds to the price of anarchy.

Mean Field Games in Nudge Systems for Societal Networks

We consider the general problem of resource sharing in societal networks, consisting of interconnected communication, transportation, energy, and other networks important to the functioning of society. Participants in such network need to take decisions daily, both on the quantity of resources to use as well as the periods of usage. With this in mind, we discuss the problem of incentivizing users to behave in such a way that society as a whole benefits. To perceive societal level impact, such incentives may take the form of rewarding users with lottery tickets based on good behavior and periodically conducting a lottery to translate these tickets into real rewards. We will pose the user decision problem as a mean field game and the incentives question as one of trying to select a good mean field equilibrium (MFE). In such a framework, each agent (a participant in the societal network) takes a decision based on an assumed distribution of actions of his/her competitors and the incentives provided by the social planner. The system is said to be at MFE if the agent’s action is a sample drawn from the assumed distribution. We will show the existence of such an MFE under general settings, and also illustrate how to choose an attractive equilibrium using as an example demand-response in the (smart) electricity network.

Optimal Coupling Patterns in Interconnected Communication Networks

Traffic dynamics on single or isolated complex networks has been extensively studied in the past decade. Recently, several coupled network models have been developed to describe the interactions between real-world networked systems. In a system of interconnected networks, the coupling links refer to the physical links between networks and provide paths for traffic transmission. Thus, the coupling pattern, i.e., the way coupling links are added, has a profound influence on the overall traffic performance. In this paper, we employ a simulated annealing (SA) algorithm to find a near-optimal configuration of the coupling links, which effectively improves the overall traffic capacity compared with random, assortative and disassortative couplings. Furthermore, we investigate the optimal configuration of coupling links given by the SA algorithm and develop a faster method to select the coupling links.

The Celtic Question: An Assessment of Identity Definition in the European Iron Age

The identity of the “Celts” has played an integral role in understandings of the Iron Age and the more recent socio-political history of Europe. However, the terms and attitudes which have been in place since the 19th century have created a field of research characterized by assumptions about a ‘people’ and a culture. Previous study of the “Celts” has been conducted in three main areas—genetics, linguistics, and material culture from the archaeological record. Through the reassessment of these three fields, substantial divergence in the patterns and trends between fields, as well as the highly regional nature of the evidence has been revealed within the vast interconnected trade and communication network that developed in Iron Age Europe. As a result, the unitary phenomenon identified under the term “Celts” is actually that network. This paper argues that “Celtic” should be redefined as the label for that trade and communication network, not as a label for a group, culture, or people, enabling the establishment of new identities for the regional populations of the European Iron Age.

Computational analysis of cascading failures in power networks

This paper focuses on cascading line failures in the transmission system of the power grid. Such a cascade may have a devastating effect not only on the power grid but also on the interconnected communication networks. Recent large-scale power outages demonstrated the limitations of epidemic- and percolation-based tools in modeling the cascade evolution. Hence, based on a linearized power flow model (that substantially differs from the classical packet flow models), we obtain results regarding the various properties of a cascade. Specifically, we consider performance metrics such as the the distance between failures, the length of the cascade, and the fraction of demand (load) satisfied after the cascade. We show, for example, that due to the unique properties of the model: (i) the distance between subsequent failures can be arbitrarily large and the cascade may be arbitrarily long, (ii) a large set of initial line failures may have a smaller effect than a failure of one of the lines in the set, and (iii) minor changes to the network parameters may have a significant impact. Moreover, we show that finding the set of lines whose removal has the most significant impact (under various metrics) is NP-Hard. Moreover, we develop a fast algorithm to recompute the flows at each step of the cascade. The results can provide insight into the design of smart grid measurement and control algorithms that can mitigate a cascade.

High-resolution deep imaging of live cellular spheroids with light-sheet-based fluorescence microscopy

Conventional two-dimensional cell monolayers do not provide the geometrical, biochemical and mechanical cues found in real tissues. Cells in real tissues interact through chemical and mechanical stimuli with adjacent cells and via the extracellular matrix. Such a highly interconnected communication network extends along all three dimensions. This architecture is lost in two-dimensional cultures. Therefore, at least in many cases, two-dimensional cell monolayers do not represent a suitable in vitro tool to characterize accurately the biology of real tissues. Many studies performed over the last few years have demonstrated that the differences between three-dimensional and two-dimensional cultured cells are striking at the morphological and molecular levels and that three-dimensional cell cultures can be employed in order to shrink the gap between real tissues and in vitro cell models. End-point and long-term imaging of cellular and sub-cellular processes with fluorescence microscopy provides direct insight into the physiological behavior of three-dimensional cell cultures and their response to chemical or mechanical stimulation. Fluorescence imaging of three-dimensional cell cultures sets new challenges and imposes specific requirements concerning the choice of a suitable microscopy technique. Deep penetration into the specimen, high imaging speed and ultra-low intensity of the excitation light are key requirements. Light-sheet-based fluorescence microscopy (LSFM) offers a favorable combination of these requirements and is therefore currently established as the technique of choice for the study of three-dimensional cell cultures. This review illustrates the benefits of cellular spheroids in the life sciences and suggests that LSFM is essential for investigations of cellular and sub-cellular dynamic processes in three-dimensions over time and space.

Interconnected communications networks and home market effects

Abstract. This study develops a model of trade that highlights the effects of the interconnection of country‐specific communications networks as a driving force behind trade in high‐tech products with positive transport costs. By constructing a two‐country model of monopolistic competition with two production factors, it is shown that the locational decisions of firms may magnify the influence of interconnected networks. In a reversal of the standard home market effects, the abundance of unskilled labour in the developing countries can attract high‐tech firms from the developed countries. JEL classification: D43, F12, L13

On the enlargement of interconnected communications networks in the world economy

This note develops a multi-country model of trade that captures the role of country-specific communications network interconnectivity, which enhances trade in intermediate business services. The effect of an enlargement of the network, which implies an increase in the number of countries connected through networks, is examined. It is shown that, from the viewpoint of the connected countries, an enlargement of the interconnected networks has two conflicting effects: gains due to increased specialization and losses from a deterioration in the terms of trade.

EGF receptor transactivation by G-protein-coupled receptors requires metalloproteinase cleavage of proHB-EGF.

Cross-communication between different signalling systems allows the integration of the great diversity of stimuli that a cell receives under varying physiological situations. The transactivation of epidermal growth factor receptor (EGFR)-dependent signalling pathways upon stimulation of G-protein-coupled receptors (GPCRs), which are critical for the mitogenic activity of ligands such as lysophosphatidic acid, endothelin, thrombin, bombesin and carbachol, provides evidence for such an interconnected communication network. Here we show that EGFR transactivation upon GPCR stimulation involves proHB-EGF and a metalloproteinase activity that is rapidly induced upon GPCR-ligand interaction. We show that inhibition of proHB-EGF processing blocks GPCR-induced EGFR transactivation and downstream signals. The pathophysiological significance of this mechanism is demonstrated by inhibition of constitutive EGFR activity upon treatment of PC3 prostate carcinoma cells with the metalloproteinase inhibitor batimastat. Together, our results establish a new mechanistic concept for cross-communication among different signalling systems.

Performance of Double-Tier Access-Control Schemes Using a Polling Backbone for Metropolitan and Interconnected Communication Networks

We consider a double-tier communication network architecture for metropolitan area and packet radio networks for controlling the access of network terminals into a single shared broadcast channel. Terminals are organized into local groups in accordance with their geographical proximity or other criteria. Each local group can be associated with a primary station. The latter can serve as an unbuffered repeater for terminal transmissions unto the multiple-access channel. A polling policy is used by the primary stations to gain access into the shared communications backbone. Once a primary station is provided access into the channel, it initiates a local access control procedure. Message delay performance results and bounds are obtained for general reservation local-access procedures. In particular, we analyze and present performance results for a polling/tree-random-access procedure which can be effectively used for many packet radio and cellular digital radio networks, as well as for a polling/positionalpriority scheme for CATV and fiber-optic based networks.

Synchronous digit switching in highly interconnected communication networks

Highly interconnected networks to be used for the distribution of high-speed digital information are currently the subject of design studies by both civil and military research organisations. One problem in such networks is that any frequency asynchronism between the oscillators which control digit switching at trunk exchanges can result in loss of information. Methods of controlling the frequency of oscillators to develop a common average frequency at all exchanges and so prevent information loss are discussed in the paper.The absence of a reference frequency, coupled with the effects of transmission delay between exchanges, can result in a controlled frequency which is outside the tolerance band of the uncontrolled frequencies. This feature applies when a linear control characteristic is employed and leads to an argument which favours a nonlinear characteristic. Control-loop stability is discussed, the bandwidth of the circuit used to extract digit-timing information being shown to be a critical factor affecting stability.