843 research outputs found

    Tree formation with physical layer security considerations in wireless multi-hop networks

    No full text
    Physical layer security has emerged as a promising technique that complements existing cryptographic approaches and enables the securing of wireless transmissions against eavesdropping. In this paper, the impact of optimizing physical layer security metrics on the architecture and interactions of the nodes in multi-hop wireless networks is studied. In particular, a game-theoretic framework is proposed using which a number of nodes interact and choose their optimal and secure communication paths in the uplink of a wireless multi-hop network, in the presence of eavesdroppers. To this end, a tree formation game is formulated in which the players are the wireless nodes that seek to form a network graph among themselves while optimizing their multi-hop secrecy rates or the path qualification probabilities, depending on their knowledge of the eavesdroppers' channels. To solve this game, a distributed tree formation algorithm is proposed and is shown to converge to a stable Nash network. Simulation results show that the proposed approach yields significant performance gains in terms of both the average bottleneck secrecy rate per node and the average path qualification probability per node, relative to classical best-channel algorithms and the single-hop star network. The results also assess the properties and characteristics of the resulting Nash networks.This work was supported in part by the Australian Research Council's Discovery Projects funding scheme (project no. DP110102548), and in part by an AFOSR MURI Grant (FA9550-10-1-0573)

    Telematics programme (1991-1994). EUR 15402 EN

    Get PDF

    A new business model?

    Get PDF
    The paper delivers an analysis of the “New Economy” focussing on the roles of new business models, the capital market and venture capital. The capital market created a double standard in the 1990s: A high return on capital was required from old economy firms whereas money was thrown at new economy firms which had a business idea that stimulated the fantasies of financial investors but no earnings. Through the gradual burst of the tech stock bubble since spring 2000 it has come to the eyes of the public that many new economy start ups were unable to recover their costs. This paper shows that business models related to the internet can only work under certain conditions. The sectoral distribution of power, for example, determines the prospects of the single firms to realise e-commerce in a profitable way. Digital technologies do not necessarily enhance profitability. On the contrary, they can increase competition and lead to lower profit rates. The limitation of competition appears to be a central condition of successful cost recovery. The venture capital cycle has been an important driving force of the new economy boom, but it can also be momentum of a longer crisis. Enormous amounts of money have been channeled to new economy start ups hoping that successful IPOs will one day give venture capitalists a high return. But the burst of the bubble has brought down the IPO activity and interrupted the valorisation cycle of venture capital. Financial investors have reacted to the crisis by shifting their capital to even riskier investments, as the come-back of hedge funds indicates. --

    Economic advantages of a municipal motor truck terminal in Boston, Massachusetts

    Full text link
    Thesis (M.B.A.)--Boston Universit

    Notes

    Get PDF

    Towards efficacy and efficiency in sparse delay tolerant networks

    Get PDF
    The ubiquitous adoption of portable smart devices has enabled a new way of communication via Delay Tolerant Networks (DTNs), whereby messages are routed by the personal devices carried by ever-moving people. Although a DTN is a type of Mobile Ad Hoc Network (MANET), traditional MANET solutions are ill-equipped to accommodate message delivery in DTNs due to the dynamic and unpredictable nature of people\u27s movements and their spatio-temporal sparsity. More so, such DTNs are susceptible to catastrophic congestion and are inherently chaotic and arduous. This manuscript proposes approaches to handle message delivery in notably sparse DTNs. First, the ChitChat system [69] employs the social interests of individuals participating in a DTN to accurately model multi-hop relationships and to make opportunistic routing decisions for interest-annotated messages. Second, the ChitChat system is hybridized [70] to consider both social context and geographic information for learning the social semantics of locations so as to identify worthwhile routing opportunities to destinations and areas of interest. Network density analyses of five real-world datasets is conducted to identify sparse datasets on which to conduct simulations, finding that commonly-used datasets in past DTN research are notably dense and well connected, and suggests two rarely used datasets are appropriate for research into sparse DTNs. Finally, the Catora system is proposed to address congestive-driven degradation of service in DTNs by accomplishing two simultaneous tasks: (i) expedite the delivery of higher quality messages by uniquely ordering messages for transfer and delivery, and (ii) avoid congestion through strategic buffer management and message removal. Through dataset-driven simulations, these systems are found to outperform the state-of-the-art, with ChitChat facilitating delivery in sparse DTNs and Catora unencumbered by congestive conditions --Abstract, page iv

    Socio-economic aware data forwarding in mobile sensing networks and systems

    Get PDF
    The vision for smart sustainable cities is one whereby urban sensing is core to optimising city operation which in turn improves citizen contentment. Wireless Sensor Networks are envisioned to become pervasive form of data collection and analysis for smart cities but deployment of millions of inter-connected sensors in a city can be cost-prohibitive. Given the ubiquity and ever-increasing capabilities of sensor-rich mobile devices, Wireless Sensor Networks with Mobile Phones (WSN-MP) provide a highly flexible and ready-made wireless infrastructure for future smart cities. In a WSN-MP, mobile phones not only generate the sensing data but also relay the data using cellular communication or short range opportunistic communication. The largest challenge here is the efficient transmission of potentially huge volumes of sensor data over sometimes meagre or faulty communications networks in a cost-effective way. This thesis investigates distributed data forwarding schemes in three types of WSN-MP: WSN with mobile sinks (WSN-MS), WSN with mobile relays (WSN-HR) and Mobile Phone Sensing Systems (MPSS). For these dynamic WSN-MP, realistic models are established and distributed algorithms are developed for efficient network performance including data routing and forwarding, sensing rate control and and pricing. This thesis also considered realistic urban sensing issues such as economic incentivisation and demonstrates how social network and mobility awareness improves data transmission. Through simulations and real testbed experiments, it is shown that proposed algorithms perform better than state-of-the-art schemes.Open Acces

    A new business model?

    Full text link
    "The paper delivers an analysis of the 'New Economy' focussing on the roles of new business models, the capital market and venture capital. The capital market created a double standard in the 1990s: A high return on capital was required from old economy firms whereas money was thrown at new economy firms which had a business idea that stimulated the fantasies of financial investors but no earnings. Through the gradual burst of the tech stock bubble since spring 2000 it has come to the eyes of the public that many new economy start ups were unable to recover their costs. This paper shows that business models related to the internet can only work under certain conditions. The sectoral distribution of power, for example, determines the prospects of the single firms to realise e-commerce in a profitable way. Digital technologies do not necessarily enhance profitability. On the contrary, they can increase competition and lead to lower profit rates. The limitation of competition appears to be a central condition of successful cost recovery. The venture capital cycle has been an important driving force of the new economy boom, but it can also be momentum of a longer crisis. Enormous amounts of money have been channeled to new economy start ups hoping that successful IPOs will one day give venture capitalists a high return. But the burst of the bubble has brought down the IPO activity and interrupted the valorisation cycle of venture capital. Financial investors have reacted to the crisis by shifting their capital to even riskier investments, as the come-back of hedge funds indicates." (author's abstract)"Die Autoren liefern einen Beitrag zum VerstĂ€ndnis der 'New Economy', indem sie die Bedeutung neuer GeschĂ€ftsmodelle, nĂ€mlich des Kapitalmarkts und des Risikokapitals, herausarbeiten. Der Kapitalmarkt operierte in den 1990er Jahren mit zweierlei Maß: Von Unternehmen der 'Old Economy' wurden hohe Kapitalrenditen gefordert, wĂ€hrend Unternehmen der 'New Economy' es leicht hatten, Geld zu bekommen, sofern sie nur eine GeschĂ€ftsidee hatten, die die Phantasie der Finanzinvestoren stimulierte. Durch den Kursverfall der 'Technologieaktien' seit dem FrĂŒhjahr 2000 wurde deutlich, daß viele 'Start-up'-Unternehmen der New Economy unfĂ€hig waren, ihre Kosten zu decken. Die Autoren zeigen, daß GeschĂ€ftsmodelle, die sich auf das Internet beziehen, nur unter bestimmten Bedingungen profitabel sind. Die sektorale Machtverteilung entscheidet beispielsweise ĂŒber die Chancen von Unternehmen, den E-Commerce in profitabler Weise zu nutzen. Digitale Technologien können auch die Konkurrenz verschĂ€rfen und zu sinkenden Profitraten fĂŒhren. Die Begrenzung der Konkurrenz ist eine zentrale Voraussetzung erfolgreicher Kostendeckung. Der Zyklus der Risikokapitalinvestitionen war eine wichtige Triebkraft des New- Economy-Booms, aber er könnte sich ebenso als Moment einer lĂ€nger andauernden Krise erweisen. Enorme BetrĂ€ge wurden in der Hoffnung in die 'Start-ups' der New Economy gelenkt, daß erfolgreiche BörsengĂ€nge den Risikokapitalisten eines Tages hohe Gewinne bescheren wĂŒrden. Seitdem die spekulative Blase an den AktienmĂ€rkten geplatzt ist, gibt es kaum noch BörsengĂ€nge, so daß der Verwertungszyklus des Risikokapitals unterbrochen ist. Finanzinvestoren haben auf die Krise reagiert, indem sie ihr Kapital auf noch riskantere Investments verlagert haben, wie das Comeback der Hedgefonds zeigt." (Autorenreferat
    • 

    corecore