Spectrum sharing security and attacks in CRNs: a review

Cognitive Radio plays a major part in communication technology by resolving the shortage of the spectrum through usage of dynamic spectrum access and artificial intelligence characteristics. The element of spectrum sharing in cognitive radio is a fundament al approach in utilising free channels. Cooperatively communicating cognitive radio devices use the common control channel of the cognitive radio medium access control to achieve spectrum sharing. Thus, the common control channel and consequently spectrum sharing security are vital to ensuring security in the subsequent data communication among cognitive radio nodes. In addition to well known security problems in wireless networks, cognitive radio networks introduce new classes of security threats and challenges, such as licensed user emulation attacks in spectrum sensing and misbehaviours in the common control channel transactions, which degrade the overall network operation and performance. This review paper briefly presents the known threats and attacks in wireless networks before it looks into the concept of cognitive radio and its main functionality. The paper then mainly focuses on spectrum sharing security and its related challenges. Since spectrum sharing is enabled through usage of the common control channel, more attention is paid to the security of the common control channel by looking into its security threats as well as protection and detection mechanisms. Finally, the pros and cons as well as the comparisons of different CR - specific security mechanisms are presented with some open research issues and challenges

Performance analysis of a novel decentralised MAC protocol for cognitive radio networks

Due to the demand of emerging Cognitive Radio (CR) technology to permits using the unused licensed spectrum parts by cognitive users (CUs) to provide opportunistic and efficient utilisation of the white spaces. This requires deploying a CR MAC with the required characteristics to coordinate the spectrum access among CUs. Therefore, this paper presents the design and implementation of a novel Medium Access Control (MAC) protocol for decentralised CRNs (MCRN). The protocol provides efficient utilisations of the unused licensed channels and enables CUs to exchange data successfully over licensed channels. This is based on the observation procedure of sensing the status of the Licensed Users (LUs) are ON or OFF over the licensed channels. The protocol is validated with the comparison procedure against two different benchmark protocols in terms of the network performance; communication time and throughput. Therefore, performance analysis demonstrated that the proposed MCRN perform better and achieve higher throughput and time benefits than the benchmarks protocols

A Novel Device-to-Device Discovery Scheme for Underlay Cellular Networks

Tremendous growing demand for high data rate services such as video, gaming and social networking in wireless cellular systems, attracted researchers' attention to focus on developing proximity services. In this regard, device-to-device (D2D) communications as a promising technology for future cellular systems, plays crucial rule. The key factor in D2D communication is providing efficient peer discovery mechanisms in ultra dense networks. In this paper, we propose a centralized D2D discovery scheme by employing a signaling algorithm to exchange D2D discovery messages between network entities. In this system, potential D2D pairs share uplink cellular users' resources with collision detection, to initiate a D2D links. Stochastic geometry is used to analyze system performance in terms of success probability of the transmitted signal and minimum required time slots for the proposed discovery scheme. Extensive simulations are used to evaluate the proposed system performance.Comment: Accepted for publication in 25'th Iranian Conference on Electrical Engineering (ICEE2017

Power Control and Channel Allocation for D2D Underlaid Cellular Networks

Device-to-Device (D2D) communications underlaying cellular networks is a viable network technology that can potentially increase spectral utilization and improve power efficiency for proximitybased wireless applications and services. However, a major challenge in such deployment scenarios is the interference caused by D2D links when sharing the same resources with cellular users. In this work, we propose a channel allocation (CA) scheme together with a set of three power control (PC) schemes to mitigate interference in a D2D underlaid cellular system modeled as a random network using the mathematical tool of stochastic geometry. The novel aspect of the proposed CA scheme is that it enables D2D links to share resources with multiple cellular users as opposed to one as previously considered in the literature. Moreover, the accompanying distributed PC schemes further manage interference during link establishment and maintenance. The first two PC schemes compensate for large-scale path-loss effects and maximize the D2D sum rate by employing distance-dependent pathloss parameters of the D2D link and the base station, including an error estimation margin. The third scheme is an adaptive PC scheme based on a variable target signal-to-interference-plus-noise ratio, which limits the interference caused by D2D users and provides sufficient coverage probability for cellular users. Closed-form expressions for the coverage probability of cellular links, D2D links, and sum rate of D2D links are derived in terms of the allocated power, density of D2D links, and path-loss exponent. The impact of these key system parameters on network performance is analyzed and compared with previous work. Simulation results demonstrate an enhancement in cellular and D2D coverage probabilities, and an increase in spectral and power efficiency.Comment: 35 page

A direct solution for blind separation of sources

International audienceThe paper proposes a direct estimation of the mixing matrix and not a tuning of the separation matrix as usually done. The method is based on resolution of a set of 8 equations involving cumulants up to order 4 of the mixture signals, which may be reduce to resolution to a second order polynomial equation. Experimental results and robustness suggest to use the method as a preliminary step to propose good starting points

Simulation discounted cash flow valuation for internet companies

Discounted cash flow (DCF) is the most accepted approach for company valuation. It is well grounded in theory and practice. However, the DCF approach, which is commonly used for traditional companies valuation, presents a number of serious weaknesses within the Internet companies’ context. One of these weaknesses is tackling the uncertainty that characterize future cash flows of these companies. Specifically DCF assumes that future cash flow streams are highly predictable. The effects of uncertainty are therefore tackled implicitly by discounting the expected value of the cash flows at a risk-adjusted interest rate. However, under uncertainty, future cash flows of these companies can no longer be characterized by a single value but rather by a range of values of its possible consequences. This paper looks at the way in which uncertainty can be incorporated into the traditional DCF approach so that the latter, which is otherwise conceptually sound, becomes relevant. This is done by recognizing that the DCF input variables are uncertain and will have a probability distribution pertaining to each of them. Thus by utilizing a probability-based valuation model (using Monte Carlo Simulation) it is possible to incorporate uncertainty into the analysis and address the shortcomings of the current model. The MC simulation assigns a range of values in order to cope with uncertainty underlies each key cash flow variable. The process leads to a probability distribution of the valuation criterion used, giving investors a quantitative measure of risk involved

Acute Phase Hyperglycemia among Patients Hospitalized with Acute Coronary Syndrome: Prevalence and Prognostic Significance

AbstractObjectives: Regardless of diabetes status, hyperglycemia on arrival for patients presenting with acute coronary syndrome, has been associated with adverse outcomes including death. The aim of this study is to look at the frequency and prognostic significance of acute phase hyperglycemia among patients attending the coronary care unit with acute coronary syndrome over the in-hospital admission days.Methods: The study included 287 consecutive patients in the Al- Faiha Hospital in Basrah (Southern Iraq) during a one year period from December 2007 to November 2008. Patients were divided into two groups with respect to admission plasma glucose level regardless of their diabetes status (those with admission plasma glucose of <140 mg/dl (7.8 mmol/L) and those equal to or more than that). Acute phase hyperglycemia was defined as a non-fasting glucose level equal to or above 140 mg/dl (7.8 mmol/L) regardless of past history of diabetes.Results: Sixty one point seven percent (177) of patients were admitted with plasma glucose of ≥140 mg/dl (7.8 mmol/L). There were no differences were found between both groups regarding the mean age, qualification, and smoking status, but males were predominant in both groups. A family history of diabetes, and hypertension, were more frequent in patients with plasma glucose of ≥140 mg/dl (7.8 mmol/L). There were no differences between the two groups regarding past history of ischemic heart disease, stroke, lipid profile, troponin-I levels or type of acute coronary syndrome. Again heart failure was more common in the admission acute phase hyperglycemia group, but there was no difference regarding arrhythmia, stroke, or death. Using logistic regression with heart failure as the dependent variable we found that only the admission acute phase hyperglycemia (OR=2.1344, 95�0CI=1.0282-4.4307; p=0.0419) was independently associated with heart failure. While male gender, family history of diabetes mellitus, hypertension and diabetes were not independently associated with heart failure.Conclusion: Admission acute phase hyperglycemia of ≥140 mg/dl (7.8 mmol/L) was associated with heart failure in this study

Ecosystem Monitoring and Port Surveillance Systems

International audienceIn this project, we should build up a novel system able to perform a sustainable and long term monitoring coastal marine ecosystems and enhance port surveillance capability. The outcomes will be based on the analysis, classification and the fusion of a variety of heterogeneous data collected using different sensors (hydrophones, sonars, various camera types, etc). This manuscript introduces the identified approaches and the system structure. In addition, it focuses on developed techniques and concepts to deal with several problems related to our project. The new system will address the shortcomings of traditional approaches based on measuring environmental parameters which are expensive and fail to provide adequate large-scale monitoring. More efficient monitoring will also enable improved analysis of climate change, and provide knowledge informing the civil authority's economic relationship with its coastal marine ecosystems