Efficient Wireless Security Through Jamming, Coding and Routing

There is a rich recent literature on how to assist secure communication between a single transmitter and receiver at the physical layer of wireless networks through techniques such as cooperative jamming. In this paper, we consider how these single-hop physical layer security techniques can be extended to multi-hop wireless networks and show how to augment physical layer security techniques with higher layer network mechanisms such as coding and routing. Specifically, we consider the secure minimum energy routing problem, in which the objective is to compute a minimum energy path between two network nodes subject to constraints on the end-to-end communication secrecy and goodput over the path. This problem is formulated as a constrained optimization of transmission power and link selection, which is proved to be NP-hard. Nevertheless, we show that efficient algorithms exist to compute both exact and approximate solutions for the problem. In particular, we develop an exact solution of pseudo-polynomial complexity, as well as an epsilon-optimal approximation of polynomial complexity. Simulation results are also provided to show the utility of our algorithms and quantify their energy savings compared to a combination of (standard) security-agnostic minimum energy routing and physical layer security. In the simulated scenarios, we observe that, by jointly optimizing link selection at the network layer and cooperative jamming at the physical layer, our algorithms reduce the network energy consumption by half

Impact of Mobility and Wireless Channel on the Performance of Wireless Networks

This thesis studies the impact of mobility and wireless channel characteristics, i. e. , variability and high bit-error-rate, on the performance of integrated voice and data wireless systems from network, transport protocol and application perspectives. From the network perspective, we study the impact of user mobility on radio resource allocation. The goal is to design resource allocation mechanisms that provide seamless mobility for voice calls while being fair to data calls. In particular, we develop a distributed admission control for a general integrated voice and data wireless system. We model the number of active calls in a cell of the network as a Gaussian process with time-dependent mean and variance. The Gaussian model is updated periodically using the information obtained from neighboring cells about their load conditions. We show that the proposed scheme guarantees a prespecified dropping probability for voice calls while being fair to data calls. Furthermore, the scheme is stable, insensitive to user mobility process and robust to load variations. From the transport protocol perspective, we study the impact of wireless channel variations and rate scheduling on the performance of elastic data traffic carried by TCP. We explore cross-layer optimization of the rate adaptation feature of cellular networks to optimize TCP throughput. We propose a TCP-aware scheduler that switches between two rates as a function of TCP sending rate. We develop a fluid model of the steady-state TCP behavior for such a system and derive analytical expressions for TCP throughput that explicitly account for rate variability as well as the dependency between the scheduler and TCP. The model is used to choose RF layer parameters that, in conjunction with the TCP-aware scheduler, improve long-term TCP throughput in wireless networks. A distinctive feature of our model is its ability to capture variability of round-trip-time, channel rate and packet error probability inherent to wireless communications. From the application perspective, we study the performance of wireless messaging systems. Two popular wireless applications, the short messaging service and multimedia messaging service are considered. We develop a mathematical model to evaluate the performance of these systems taking into consideration the fact that each message tolerates only a limited amount of waiting time in the system. Using the model, closed-form expressions for critical performance parameters such as message loss, message delay and expiry probability are derived. Furthermore, a simple algorithm is presented to find the optimal temporary storage size that minimizes message delay for a given set of system parameters

An approach to well bore wall stability analysis by MATLAB and FLAC3D software for Salman oil field

Instability in wellbore wall is one of the most serious difficulties in drilling, because this problem can ultimately delay the drilling operations, increase cost of drilling and in some cases lead to the wellbore becoming abandoned. Now a day, with consideration of physical and chemical characteristics of mud we can apply the necessary changes to the composition of mud and make the wellbore wall more stable. With the help of the science of rock mechanics and the full knowledge of the characteristics of formation, the optimum path to drilling wellbore and the mud window can be calculated. In this research, first stability of the shale layer in wellbore 2SK5 in Salman oil field using analytical method (MATLAB software) and numerical method (FALC3D software) with the use of three criteria of failure of Mohr Coulomb, Mogi Coulomb and Drucker Prager will be studied and at the same time comparisons of applications of above criteria in stability of wellbore and comparisons of occurred difficulties in drilling this wellbore will be studied, and recommendations concerning drilling wellbore in the mentioned oil field will be presented, also at the same time some research work will be carried out in assessing drilling deviational wellbores in oil fields and effect of different stress regimes for calculating optimum direction and angle of deviation. Therefore, we conclude that stability of the wellbore with the increase in angle of deviation of wellbore does not necessarily decrease from that of its right angled one (90 degrees) , unless in a case when stress is normal or the principal horizontal stresses are equal. Also, when stress regime is normal, drilling in the direction of minimum horizontal stress and decrease in angle of deviation of the wellbore from that of right angled one will be most stabilizing for the wellbore, but drilling in this direction in the other two stress regimes will result maximum instability

Sulfur isotope geochemistry of the Chodarchay Cu-Au deposit, Tarom, NW Iran

The Chodarchay porphyry–high-sulfidation epithermal Cu-Au deposit in the Tarom subzone of the western Alborz structural zone of NW Iran is related to quartz-monzonite and alkali-granite intrusions that were emplaced within the volcanic-volcaniclastic rocks of Karaj Formation during Tertiary. The Chodarchay deposit formed as a high-sulfidation epithermal overprint on porphyry type mineralization. The mineralization occurred as stockwork, dissemination, veinlet, open space filling and breccias. Chalcopyrite, pyrite, sphalerite, and galena are the main sulfide minerals in the area. The sulfur isotope composition of sulfide minerals from the Chodarchay deposit is positive, ranging from 0.2 to 6.8 ‰. The sphalerite-galena isotope geothermometer shows 360 °C for the crystallization temperature. Sulfur was sourced from a homogeneous magma, and its isotopic composition decreases with depth and temperature decreasing due to fluid oxidation changes. Therefore, sulfur isotope assemblages show a systematic spatial distribution within the Chodarchay system.Peer ReviewedPreprin

Mineralogy, alteration, and sulfur isotope geochemistry of the Zehabad intermediate-sulfidation epithermal deposit, NW Iran

The Zehabad Pb-Zn-Au-Ag (Cu) deposit lies in the Alborz magmatic arc of northwestern Iran. Ore-bearing breccia veins hosted by Eocene tuffs emplaced along the 80–130° trending fault and fracture zone. Mineralization occurs in the contact of the late Eocene igneous bodies and the Eocene volcanic and volcanosedimentary Karaj Formation. Mineralization formed in five stages: 1) disseminated framboidal pyrite and minor chalcopyrite and sphalerite; 2) quartz veins containing chalcopyrite, bornite, pyrite, and sphalerite; 3) deposition of specularite and gold grains hosted in quartz veins that crosscut chalcopyrite; 4) the main stage of mineralization that contains galena, sphalerite, tennantite-tetrahedrite, pyrite, sulfosalts, and gold; 5) barren quartz-calcite veins with sulfide mineral fragments of earlier stages. The hydrothermal alteration from closest to the veins outwards includes: a) silicification; b) phyllic with quartz, pyrite, sericite, and calcite; c) argillic with illite, kaolinite, and montmorillonite; d) propylitic containing epidote, calcite, chlorite, and sericite and; e) carbonatization that crosscuts all previous alteration types. Quartz and calcite are the most important gangue minerals at the deposit and show a close relationship with mineralization. Sulfur isotope compositions (0.8‰ to –10.1‰) suggest that the ore-forming fluids derived from magmatic sources with a temperature range of 276–288 °C. According to the field (macroscopic), microscopic, alteration, and sulfur isotope studies, the Zehabad base and precious metal mineralization is considered an intermediate-sulfidation epithermal deposit.Peer ReviewedPostprint (published version

WebPro: A proxy-based approach for low latency web browsing on mobile devices

Abstract—To load a webpage, a web browser first downloads the base HTML file of the page in order to discover the list of objects referenced in the page. This process takes roughly one round-trip time and constitutes a significant portion of the web browsing delay on mobile devices as wireless networks suffer from longer transmission and access delays compared to wired networks. In this work, we propose a solution for eliminating this initial delay, which is transparent to end systems, does not require modifying HTTP, and is well suited for web browsing on mobile devices. Our solution, called WebPro, relies on a network proxy that builds an up-to-date database of resource lists for the websites visited frequently by network users. The proxy resides in the wired part of the network, and hence can afford to pro-actively build and refresh the resource list database periodically. When a request for a webpage comes to the proxy, it simultaneously fetches the base HTML and all referenced objects required to render the webpage using the corresponding resource list stored in the local database. We have built a working prototype of WebPro and have conducted live experiments over WiFi and LTE networks. Our results show an average of 26% reduction in page load time for a mix of popular web sites chosen from categories such as news, sports and shopping. Moreover, in comparison to another best known proxy-based solution, WebPro provides delay reductions ranging from 5 % to 51 % for a variety of web sites. Keywords—Web browsing, Mobile devices, Browsing delay

Sr Isotopic Ratios of two Magmatic Series Unraveling the Role of Crustal Contamination in NW Firoozeh, NE Iran

AbstractTertiary basalts of NW Firoozeh in northeastern Iran are alkaline and evolve gradually towards the subalkaline andesites and dacites. Unvariant Sr isotopic ratios in the basalts, andesites and dacites indicate that the evolution of their parental melt towards progressively more differentiated melt occurred in the absence of crustal contamination. On the contrary, progressively higher Sr isotopic ratios in the alkaline basaltic trachyandesites to trachytes from NW Firoozeh suggest that crustal contamination played a significant role in the evolution of the alkaline rocks