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One of the basic requirements of today's sophisticated world is the availability of electrical energy, and neglect of this matter may have irreparable damages such as an extensive blackout. The problems which were introduced about the traditional power grid, and also, the growing advances in smart technologies make the traditional power grid go towards smart power grid. Although widespread utilisation of telecommunication networks in smart power grid enhances the efficiency of the system, it will create a critical platform for cyber attacks and penetration into the system. Automatic generation control (AGC) is a fundamental control system in the power grid, and it is responsible for controlling the frequency of the grid. An attack on the data transmitted through the telecommunications link from the sensors to the AGC will cause frequency deviation, resulting in disconnection of the load, generators and ultimately global blackout. In this study, by using a Kalman filter and a proposed detector, a solution has been presented to detect the attack before it can affect the system. Contrary to existing methods, this method is able to detect attacks that are stealthy from the area control error signal and χ2-detector. Simulations confirm the effectiveness of this method.

The article studies the steady-state performance of a diffusion least-mean squares (LMS) adaptive network with imperfect communications where the topology is random (links may fail at random times) and the communication in the channels is corrupted by additive noise. Using the established weighted spatial–temporal energy conservation argument, the authors derive a variance relation which contains moments that represent the effects of noisy links and random topology. The authors evaluate these moments and derive closed-form expressions for the mean-square deviation, excess mean-square error and mean-square error to explain the steady-state performance at each individual node. The mean stability analysis is also provided. The derived theoretical expressions have good match with simulation results. Nevertheless, the important result is that the noisy links are the main factor in performance degradation of a diffusion LMS algorithm running in a network with imperfect communications.

This study proposes a new analytical model of a multi-service switching network with overflow links with finite capacity in the first stage of the network. The proposed model assumes that overflow links can service a number of selected call classes from among all classes offered to the network. A particular attention is given to the method for a determination of the effective availability parameter for networks with overflow links. The proposed model can be also used to determine the dependence between the internal blocking probability and the capacity of overflow links. A relevant simulation study has confirmed high accuracy of the proposed method as well as the applicability of the model in engineering practice, in modelling of multi-stage switching networks both optical and electronic.

Commercial microwave links (MWLs) were suggested about a decade ago as a new source for quantitative precipitation estimates (QPEs). Meanwhile, the theory is well understood and rainfall monitoring with MWLs is on its way to being a mature technology, with several well-documented case studies, which investigate QPEs from multiple MWLs on the mesoscale. However, the potential of MWLs to observe microscale rainfall variability, which is important for urban hydrology, has not been investigated yet. In this paper, we assess the potential of MWLs to capture the spatio-temporal rainfall dynamics over small catchments of a few square kilometres. Specifically, we investigate the influence of different MWL topologies on areal rainfall estimation, which is important for experimental design or to a priori check the feasibility of using MWLs. In a dedicated case study in Prague, Czech Republic, we collected a unique dataset of 14 MWL signals with a temporal resolution of a few seconds and compared the QPEs from the MWLs to reference rainfall from multiple rain gauges. Our results show that, although QPEs from most MWLs are probably positively biased, they capture spatio-temporal rainfall variability on the microscale very well. Thus, they have great potential to improve runoff predictions. This is especially beneficial for heavy rainfall, which is usually decisive for urban drainage design.

As the Internet takes an increasingly central role in the authors communications infrastructure, the slowness of routing convergence after network failure is becoming a significant problem in the current link-state-based routing protocol. There is an alternative approach, which is to compute backup routes that allow the failure to be repaired locally by the routers that detect the failure without informing other routers of the failure immediately. Failure insensitive routing (FIR) adopts this approach, in which packet forwarding is based on not only the destination but also the link it arrives from. However, FIR faces two problems. First, a packet may travel an unnecessary path, which degrades resource utilisation efficiency. Second, FIR may fail to set a re-route path even though an active path is available. This study proposes a resilient routing scheme that avoids these two problems by enhancing FIR. It is named smart FIR (S-FIR). Upon failure, S-FIR employs a backup routing table based on the unexpected link from which a packet arrives so that subsequent packets can be forwarded to a different next hop to avoid roll back, whereas the original FIR forwards every packet based on the current working routing table. Numerical results indicate that S-FIR reduces the path length significantly, compared with the original FIR. In addition, in case of any link failure, S-FIR is proven to guarantee that any packet reaches its destination as long as there is a valid path. S-FIR provides more robust routing than FIR.

The ability to predict the runoff response of an urban catchment to rainfall is crucial for managing drainage systems effectively and controlling discharges from urban areas. In this paper we assess the potential of commercial microwave links (MWL) to capture the spatio-temporal rainfall dynamics and thus improve urban rainfall-runoff modelling. Specifically, we perform numerical experiments with virtual rainfall fields and compare the results of MWL rainfall reconstructions to those of rain gauge (RG) observations. In a case study, we are able to show that MWL networks in urban areas are sufficiently dense to provide good information on spatio-temporal rainfall variability and can thus considerably improve pipe flow prediction, even in small subcatchments. In addition, the better spatial coverage also improves the control of discharges from urban areas. This is especially beneficial for heavy rainfall, which usually has a high spatial variability that cannot be accurately captured by RG point measurements.

Cooperative diversity plays an important role in combating channel fading and increasing reliability of wireless communication links. The main purpose of cooperative diversity is to transmit the same data from multiple sources. Hence, there is no inherent capability in the cooperative diversity schemes to deal with scalable types of data, for example, scalable video coded signals. The authors introduce a two-phase cooperative multicast scheme based on superposition coding to transmit scalable video signals. The new scheme mixes the superposition with cooperative diversity, and chooses the right parameters in both schemes to enhance the system's multicast capability. This study also derives an exact closed-form expression of the average multicast group throughput in case of Rayleigh flat fading channel. The closed-form expression allows system designers to choose the correct cooperation and superposition parameters to satisfy the network operator needs. Simulations show that, in addition to the additional degrees of freedom resulting from using cooperation with superposition, the proposed scheme outperforms the conservative scheme and schemes solely exploiting cooperative relaying or superposition. Simulations show that the new scheme can increase the average network throughput more than four times compared to the conservative scheme.

Maximum likelihood (ML) carrier-frequency offset estimation for orthogonal frequency-division multiple access uplink is a complex multi-parameter estimation problem. The ML approach is a global optima search problem, which is prohibitive for practical applications because of the requirement of multidimensional exhaustive search for a large number of users. There are a few attempts to reduce the complexity of ML search by applying evolutionary optimisation algorithms. In this study, the authors propose a novel canonical particle swarm optimisation (CPSO)-based scheme, to reduce the computational complexity without compromising the performance and premature convergence. The proposed technique is a two-step process, where, in the first step, low resolution alternating projection frequency estimation (APFE) is used to generate a single better positioned particle for CPSO, followed by an actual CPSO procedure in second step. The mean square error performance of the proposed scheme is compared with existing low complexity algorithms namely APFE and linear particle swarm optimisation with mutation. Simulation results presented in this study show that the new scheme completely avoids premature convergence for a large number of users as high as 32.

For twenty-five years following the Voyager mission, scientists speculated about Saturn's largest moon, a mysterious orb clouded in orange haze. Finally, in 2005, the Cassini-Huygens probe successfully parachuted down through Titan's atmosphere, all the while transmitting images and data. In the early 1980s, when the two Voyager spacecraft skimmed past Titan, Saturn's largest moon, they transmitted back enticing images of a mysterious world concealed in a seemingly impenetrable orange haze.Titan Unveiledis one of the first general interest books to reveal the startling new discoveries that have been made since the arrival of the Cassini-Huygens mission to Saturn and Titan. Ralph Lorenz and Jacqueline Mitton take readers behind the scenes of this mission. Launched in 1997, Cassini entered orbit around Saturn in summer 2004. Its formidable payload included the Huygens probe, which successfully parachuted down through Titan's atmosphere in early 2005, all the while transmitting images and data--and scientists were startled by what they saw. One of those researchers was Lorenz, who gives an insider's account of the scientific community's first close encounter with an alien landscape of liquid methane seas and turbulent orange skies. Amid the challenges and frayed nerves, new discoveries are made, including methane monsoons, equatorial sand seas, and Titan's polar hood. Lorenz and Mitton describe Titan as a world strikingly like Earth and tell how Titan may hold clues to the origins of life on our own planet and possibly to its presence on others. Generously illustrated with many stunning images,Titan Unveiledis essential reading for anyone interested in space exploration, planetary science, or astronomy. A new afterword brings readers up to date on Cassini's ongoing exploration of Titan, describing the many new discoveries made since 2006.

Communications are required and critical to the success of space missions. This chapter summarizes the theoretical background for telecommunications link analysis and telecommunications design control. It defines the signal performance metrics, such as signal‐to‐noise‐spectral‐density ratios. In addition, the component link parameters that enhance or impair the performance are also defined. The chapter describes the statistical technique that has been used in the design of deep space telecommunications systems. The design procedure for deep space telecommunications systems design and the selection of a particular criterion for conservatism are both driven by weather conditions in the signal path between the ground station antenna and the spacecraft on telecommunications performance. The percentile technique for incorporating weather into telecommunications design control requires the preparations of two design control tables. There are two techniques for incorporating weather into telecommunications design control. The chapter explains the percentile weather technique in detail.