Nowadays, we can get the wireless devices easily, such as cell phone, PDA, etc. It can make the life convenient. The P2P network which has been constructed by the wireless devices does not need the central server. They can communicate by themselves. Not only have protected in the privacy, but also add the convenience. The reason is that the devices are portable, we can get the newest information. Some P2P software focuses on the sharing. They can share files with other peer. The file can separate into several modes. The software will share these nodes. Every peer shares his own node, and it will speed up the rate of sharing. There are some selfish peers in this environment, and they will not want to share their own node. Moreover, some of them share the incorrect file. The software will solve this kind of problem by some mechanism. And it set some incentive mechanism to make the sharing to go on. Because the wireless devices are portable, we can use these devices for exchanging immediate information. Sharing the files is similar to the exchanging. Both of the users trust each other. They can exchange automatically. So, our research has designed a reputation based mechanism for exchanging. The users can evaluate each other to exchanging the information automatically. By this mechanism, the user in our system will exchange continuously. We can reach our purpose which makes the user in our environment can exchange automatically.

This research identifies and analyzes the breadth and depth of the network of non-profit environmental organizations, sportsmen-oriented conservation groups, county conservation districts and state parks that advocate for or against Marcellus Shale drilling within northeastern and southwestern Pennsylvania where drilling occurs. The purpose of this study is to identify where resources are being mobilized and where environmental activities that focus on Marcellus Shale issues are underrepresented in the state. Results show that the counties with a higher number of gas wells do not necessarily have a higher level of environmental advocacy and that a lack of resources is a common barrier to this type of work. Organizations are better connected locally within the northeast. Counties which need to bolster their Marcellus Shale advocacy efforts in the northeast include: Carbon, Pike, Potter, Sullivan, Susquehanna and Wayne; and in the southwest: Beaver, Bedford, Blair, Fayette, Fulton, Greene, Somerset and Washington. / McAnulty College and Graduate School of Liberal Arts; / Graduate Center for Social and Public Policy / MA; / Thesis;

Large scale networks face daily thousands of network attacks. No matter the strength of the existing security defending mechanisms, these networks remain vulnerable, as new tools and techniques are being constantly developed by hackers. A new promising technology that lures the attackers in order to monitor their malicious activities and divulge their intentions is emerging with Virtual Honeypots. In the present thesis, we examine an extensive security mechanism based on three different open source low interaction honeypots. We implement this mechanism at our university campus network in an attempt to identify the potential threats and methods used against our network. The data gathered by our honeypots reveal valuable information regarding the types of attacks, the vulnerable network services within the network and the malicious activities launched by attackers.

Localization and coverage are two important and closely related problems in wireless ad hoc networks. Localization aims to determine the physical locations of devices in a network, while coverage determines if a region of interest is sufficiently monitored by devices. Localization systems require a high degree of coverage for correct functioning, while coverage schemes typically require accurate location information. This thesis investigates the relationship between localization and coverage such that new schemes can be devised which integrate approaches found in each of these well studied problems. This work begins with a thorough review of the current literature on the subjects of localization and coverage. The localization scheduling problem is then introduced with the goal to allow as many devices as possible to enter deep sleep states to conserve energy and reduce message overhead, while maintaining sufficient network coverage for high localization accuracy. Initially this sufficient coverage level for localization is simply a minimum connectivity condition. An analytical method is then proposed to estimate the amount of localization error within a certain probability based on the theoretical lower bounds of location estimation. Error estimates can then be integrated into location dependent schemes to improve on their robustness to localization error. Location error estimation is then used by an improved scheduling scheme to determine the minimum number of reference devices required for accurate localization. Finally, an optimal coverage preserving sleep scheduling scheme is proposed which is robust to localization error, a condition which is ignored by most existing solutions. Simulation results show that with localization scheduling network lifetimes can be increased by several times and message overhead is reduced while maintaining negligible differences in localization error. Furthermore, results show that the proposed coverage preserving sleep scheduling scheme results in fewer active devices and coverage holes under the presence of localization error.

Smart phones and tablet computers have greatly boosted the demand for services via wireless access points, keeping constant pressure on the network providers to deliver vast amounts of data over the wireless infrastructure. To enlarge coverage and enhance throughput, relaying has been adopted in the new generation of wireless communication systems, such as in the Long-Term Evolution Advanced standard,  and will continue to play an important role in the next generation wireless infrastructure. Depending on functionality, relaying can be characterizing into three main categories: amplify-and-forward (AF), compression-and-forward (CF), and decode-and-forward (DF).  In this thesis, we investigate different cooperative strategies in wireless networks when relaying is in use. We first investigate  the capacity outer and inner bounds for a wireless multicast relay network where two sources, connected by error-free backhaul, multicast to two destinations with the help of a full-duplex relay node.  For high-rate backhaul scenarios, we find the exact cut-set bound of the capacity region by extending the proof of the converse for the Gaussian relay channel. For low-rate backhaul scenarios, we present two genie-aided outer bounds by extending the previous proof and introducing two lemmas on conditional (co-)variance. Our inner bounds are derived from various cooperative strategies by combining DF/CF/AF relaying with network coding schemes. We also extend the noisy network coding scheme and the short-message noisy network coding approach to correlated sources. For low-rate backhaul, we propose a new coding scheme, partial-decode-and-forward based linear network coding. We derive the achievable rate regions  for these schemes and measure the performance in term of achievable rates over Gaussian channels. By numerical investigation we observe significant gains over benchmark schemes and demonstrate that the gap between upper and lower bounds is in general not large. We also show that for high-rate backhaul, the cut-set bound can be achieved  when the signal-to-noise ratios lie in the sphere defined by the source-relay and relay-destination channel gains. For wireless networks with independent noise, we propose a simple framework to get capacity outer and inner bounds based on the ``one-shot'' bounding models. We first extend the models for two-user broadcast channels to many-user scenarios and then establish the gap between upper and lower bounding models. For networks with coupled links, we propose  a channel decoupling method which can decompose the network into overlapping multiple-access channels and broadcast channels.  We then apply the one-shot models and create an upper bounding network with only  bit-pipe connections. When developing the lower bounding network, we propose a  two-step update of these models for each coupled broadcast and multiple-access channels. We demonstrate by some examples that the resulting upper bound is in general very good and the gap between the upper and lower bounds is usually not large. For relay-aided downlink scenarios, we propose a cooperation scheme by cancelling interference at the transmitter. It is indeed a symbol-by-symbol approach to one-dimension dirty paper coding (DPC). For finite-alphabet signaling and interference, we derive the optimal (in terms of maximum mutual information) modulator under a given power constraint. A sub-optimal modulator is also proposed by formulating an optimization problem that maximizes the minimum distance of the signal constellation, and this non-convex optimization problem is approximately solved by semi-definite relaxation.  Bit-level simulation shows that the optimal and sub-optimal modulators can achieve significant gains over the Tomlinson-Harashima precoder (THP) benchmark and over non-DPC reference schemes, especially when the power of the interference is larger than the power of the noise. / <p>QC 20121015</p>

Multi-channel wireless networks represent a direction that future state-of-the-art fourth generation (4G) wireless communication standards evolve towards. The IEEE 802.16 family of standards, or referred to as WiMAX, has emerged as one of the most important 4G networks to provide high speed data communication in metropolitan areas. There will be huge challenges in designing the networking protocols to allow WiMAX to provide high quality of services. How to effectively control the errors in the wireless channels and how to efficiently manage the scarce spectrum and power resources in different communication scenarios are crucial for network performance. This thesis aims to solve these challenges to improve the performance of multi-channel wireless networks, using WiMAX as a representative, through a number of techniques. First, we take advantage of the favorable properties of network coding, and design the adaptive MAC-layer and symbol-level network coding protocols. They tightly integrate with WiMAX physical and MAC layers, effectively perform error control, and efficiently utilize scarce wireless spectrum. Second, we investigate multicast services and the femto-cell architecture in WiMAX, and offer a cooperative multicast scheduling protocol as well as a cognitive WiMAX architecture with femto cells. They implement dynamic resource allocation in the networks through techniques of cooperative communication and dynamic optimization. Evaluated with rigorous analysis and extensive simulations, our proposed protocols are able to achieve substantial performance improvement over traditional protocols in the literature.

A complex adaptive systems approach has been permeating organizational studies and the field of supply network management helping to describe and explain supply network dynamics and emergent inter-firm structures. This has improved our theoretical knowledge of the nature of supply networks transforming raw materials into products, within a constantly changing environment. From the early days of simple structures, describing bi-lateral, local arrangements between firms for the creation of relatively simple products, we are now in an environment of various supply network archetypes, describing different global sourcing regimes of highly integrated, sophisticated products within multi-tier networks. This thesis is a study of the coevolution of the firm and supply network in the commercial aerospace manufacturing sector producing jetliners of 100 or more seats. One of the contributions of this research is to demonstrate how the holistic approach of complexity science can be applied to describe, understand and gain new insight into the coevolution of the firm and the supply network. Based on the findings of multiple interviews and questionnaires in eight global aerospace firms across multiple supply chain tiers, this research finds high-performing clusters of inter-firm characteristics, plus the aspects of structure and integration which deliver the supply network performance. Practitioners can use these specific results to examine their own firms and the new coevolutionary conceptual framework developed in the thesis may aid future research studies of complex adaptive systems in practice. The simple survey design and analysis method used in the final research stage of this research, has the potential for use in other industries, markets and other complex adaptive systems generally to examine performance outcomes and the effects of having or adopting new inter-firm characteristics. Finally, implications for policy include the potential to legitimize supply networks in order to stimulate competition and innovation in the economy.

Multi-channel wireless networks represent a direction that future state-of-the-art fourth generation (4G) wireless communication standards evolve towards. The IEEE 802.16 family of standards, or referred to as WiMAX, has emerged as one of the most important 4G networks to provide high speed data communication in metropolitan areas. There will be huge challenges in designing the networking protocols to allow WiMAX to provide high quality of services. How to effectively control the errors in the wireless channels and how to efficiently manage the scarce spectrum and power resources in different communication scenarios are crucial for network performance. This thesis aims to solve these challenges to improve the performance of multi-channel wireless networks, using WiMAX as a representative, through a number of techniques. First, we take advantage of the favorable properties of network coding, and design the adaptive MAC-layer and symbol-level network coding protocols. They tightly integrate with WiMAX physical and MAC layers, effectively perform error control, and efficiently utilize scarce wireless spectrum. Second, we investigate multicast services and the femto-cell architecture in WiMAX, and offer a cooperative multicast scheduling protocol as well as a cognitive WiMAX architecture with femto cells. They implement dynamic resource allocation in the networks through techniques of cooperative communication and dynamic optimization. Evaluated with rigorous analysis and extensive simulations, our proposed protocols are able to achieve substantial performance improvement over traditional protocols in the literature.

Localization and coverage are two important and closely related problems in wireless ad hoc networks. Localization aims to determine the physical locations of devices in a network, while coverage determines if a region of interest is sufficiently monitored by devices. Localization systems require a high degree of coverage for correct functioning, while coverage schemes typically require accurate location information. This thesis investigates the relationship between localization and coverage such that new schemes can be devised which integrate approaches found in each of these well studied problems. This work begins with a thorough review of the current literature on the subjects of localization and coverage. The localization scheduling problem is then introduced with the goal to allow as many devices as possible to enter deep sleep states to conserve energy and reduce message overhead, while maintaining sufficient network coverage for high localization accuracy. Initially this sufficient coverage level for localization is simply a minimum connectivity condition. An analytical method is then proposed to estimate the amount of localization error within a certain probability based on the theoretical lower bounds of location estimation. Error estimates can then be integrated into location dependent schemes to improve on their robustness to localization error. Location error estimation is then used by an improved scheduling scheme to determine the minimum number of reference devices required for accurate localization. Finally, an optimal coverage preserving sleep scheduling scheme is proposed which is robust to localization error, a condition which is ignored by most existing solutions. Simulation results show that with localization scheduling network lifetimes can be increased by several times and message overhead is reduced while maintaining negligible differences in localization error. Furthermore, results show that the proposed coverage preserving sleep scheduling scheme results in fewer active devices and coverage holes under the presence of localization error.

Previous research has shown that individuals endorsing inattention and hyperactivity-impulsivity have deficient performance on tasks tapping different aspects of attention. Although there is empirical evidence suggesting that the behavioral domains of inattention and hyperactivity-impulsivity are linked to functioning of independent and separate brain areas and neurotransmitter systems, cognitive characterization of adults presenting with problems within these domains is not complete. The aim for this study was to identify the cognitive correlates of the core behavioral domains that define the diagnosis of AD/HD (i.e., inattention and hyperactivity-impulsivity) in a sample of college students, utilizing a computerized attention task, the Attention Network Test (ANT). Different ANT task components have been found to activate separate brain areas linked to the functioning of alerting, orienting and executive attention, and have the potential to provide an indication of the efficiency of these brain networks. In addition to completing the ANT, the participants filled out questionnaires covering common symptoms of adult AD/HD, anxiety and depression. Hierarchical regression analyses revealed that there were no reliable relationships between self-reported symptoms of current inattention and hyperactivity-impulsivity and ANT performance. Further, self-reported depression and/or anxiety did not seem to impact the efficiency of attention networks to a significant degree in this study sample. Gender proved to be the most consistent predictor of ANT performance. Female gender was related to poorer executive attention efficiency. An exploratory ANCOVA revealed that individuals reporting high levels of impulsivity and emotional lability had poorer executive attention efficiency in comparison to those reporting these behaviors and problems to a lesser extent. Future research is needed in order to further explore the relationship between ANT performance and behavioral expressions of adult AD/HD and other neurological and psychiatric conditions.