An interference-aware virtual clustering paradigm for resource management in cognitive femtocell networks

Femtocells represent a promising alternative solution for high quality wireless access in indoor scenarios where conventional cellular system coverage can be poor. They are randomly deployed by the end user, so only post deployment network planning is possible. Furthermore, this uncoordinated deployment creates severe interference to co-located femtocells, especially in dense deployments. This paper presents a new architecture using a generalised virtual cluster femtocell (GVCF) paradigm, which groups together FAP into logical clusters. It guarantees severely interfering and overlapping femtocells are assigned to different clusters. Since each cluster operates on different band of frequencies, the corresponding virtual cluster controller only has to manage its own FAPs, so the overall system complexity is low. The performance of the GVCF algorithm is analysed from both a resource availability and cluster number perspective. Simulation results conclusively corroborate the superior performance of the GVCF model in interference mitigation, particularly in high density FAP scenarios

A resource need and availability view of the make or ally choice: evidence from the worldwide aircraft industry 1945-2000

This paper investigates why firms choose to undertake product expansion through alliances with competitors rather than on their own.alliance; governance; resource; competence; expansion; growth

Applications of Repeated Games in Wireless Networks: A Survey

A repeated game is an effective tool to model interactions and conflicts for players aiming to achieve their objectives in a long-term basis. Contrary to static noncooperative games that model an interaction among players in only one period, in repeated games, interactions of players repeat for multiple periods; and thus the players become aware of other players' past behaviors and their future benefits, and will adapt their behavior accordingly. In wireless networks, conflicts among wireless nodes can lead to selfish behaviors, resulting in poor network performances and detrimental individual payoffs. In this paper, we survey the applications of repeated games in different wireless networks. The main goal is to demonstrate the use of repeated games to encourage wireless nodes to cooperate, thereby improving network performances and avoiding network disruption due to selfish behaviors. Furthermore, various problems in wireless networks and variations of repeated game models together with the corresponding solutions are discussed in this survey. Finally, we outline some open issues and future research directions.Comment: 32 pages, 15 figures, 5 tables, 168 reference

The Importance of Clusters for Sustainable Innovation Processes: The Context of Small and Medium Sized Regions

The purpose of the current paper is to provide a critical state-of-the-art review of current research on clusters and its correlation to innovation dynamics in small and medium-sized regions. In particular, we focus on the systematization of the main concepts and theoretical insights that are tributary to the cluster overview in terms of its relevance for the sustainability of the innovation processes, knowledge production and diffusion, which take place inside small and medium-sized regions. The present working paper takes into account the initial studies on English industrial districts (in the nineteenth century), passing through the Italian industrial districts (in the 70s and 80s of the twentieth century), until the modern theories of business clusters and innovation systems. These frameworks constitute the basis of an approach to endogenous development, which gives a central role to the interaction between economic actors, the society and the institutions and to the identification, mobilization and combination of potential resources within a particular geographical area.Cluster; Innovation; Endogenous development; Territory.

Does Network Matter in International Expansion? Evidence from Italian SMEs

In order to face the new competitive scenario, Apulian textile firms are involved in a process of change and are trying to adopt a networking approach in analysing the international propensity of SMEs. The case of the textile network in Apulia has been analysed using a semi-structured questionnaire submitted to a sample of family businesses in order to verify the influence of network on their internationalisation process. The contribution that the network can give to the single firm in its internationalisation process depends also on the level of cooperation in the network. In fact, relationships – at least dual vertical relationships – are the key to overcoming size limit and providing value to all the partners involved. The research attempted to offer a better academic understanding of the role of network in international competitive advantage. Future research should be based on cross countries analysis, in order to determine whether or not the set of internal determinants of internationalisation pensity remain stable from one country to another. The findings should also be useful to local governance for a better understanding of the network phenomenon in order to develop appropriate programmes for training and supporting SMEs in the global market. This paper provides a wide analysis of the network role in the internationalisation process in a low technology sector.Internationalisation Strategies, Network Approach

Clustering-Based Materialized View Selection in Data Warehouses

Materialized view selection is a non-trivial task. Hence, its complexity must be reduced. A judicious choice of views must be cost-driven and influenced by the workload experienced by the system. In this paper, we propose a framework for materialized view selection that exploits a data mining technique (clustering), in order to determine clusters of similar queries. We also propose a view merging algorithm that builds a set of candidate views, as well as a greedy process for selecting a set of views to materialize. This selection is based on cost models that evaluate the cost of accessing data using views and the cost of storing these views. To validate our strategy, we executed a workload of decision-support queries on a test data warehouse, with and without using our strategy. Our experimental results demonstrate its efficiency, even when storage space is limited

Industry Cluster and Regional Economic Growth : Evidence from Hungary

Using census-type data of Hungarian firms, we test major hypotheses of spatial economic theories focusing on the impact of industrial and market concentrations on regional economic growth. Our empirical evidence confirms that both industrial and market concentrations have a significant positive impact on production growth. This finding strongly supports the Marshall- Arrow-Romer model of local knowledge externalities, suggesting that investment-driven regional development prevails in Hungary.Industry Cluster, Regional Growth, Knowledge Externalities, Hungary

Explicit probabilistic models for databases and networks

Recent work in data mining and related areas has highlighted the importance of the statistical assessment of data mining results. Crucial to this endeavour is the choice of a non-trivial null model for the data, to which the found patterns can be contrasted. The most influential null models proposed so far are defined in terms of invariants of the null distribution. Such null models can be used by computation intensive randomization approaches in estimating the statistical significance of data mining results. Here, we introduce a methodology to construct non-trivial probabilistic models based on the maximum entropy (MaxEnt) principle. We show how MaxEnt models allow for the natural incorporation of prior information. Furthermore, they satisfy a number of desirable properties of previously introduced randomization approaches. Lastly, they also have the benefit that they can be represented explicitly. We argue that our approach can be used for a variety of data types. However, for concreteness, we have chosen to demonstrate it in particular for databases and networks.Comment: Submitte