Interference-Based Optimal Power-Efficient Access Scheme for Cognitive Radio Networks

In this paper, we propose a new optimization-based access strategy of multipacket reception (MPR) channel for multiple secondary users (SUs) accessing the primary user (PU) spectrum opportunistically. We devise an analytical model that realizes the multipacket access strategy of SUs that maximizes the throughput of individual backlogged SUs subject to queue stability of the PU. All the network receiving nodes have MPR capability. We aim at maximizing the throughput of the individual SUs such that the PU's queue is maintained stable. Moreover, we are interested in providing an energy-efficient cognitive scheme. Therefore, we include energy constraints on the PU and SU average transmitted energy to the optimization problem. Each SU accesses the medium with certain probability that depends on the PU's activity, i.e., active or inactive. The numerical results show the advantage in terms of SU throughput of the proposed scheme over the conventional access scheme, where the SUs access the channel randomly with fixed power when the PU is sensed to be idle

Unleashing the secure potential of the wireless physical layer: Secret key generation methods

AbstractWithin the paradigm of physical layer security, a physical layer characteristic is used as a common source of randomness to generate the secret key. This key is then used to encrypt the data to hide information from eavesdroppers. In this paper, we survey the most recent common sources of randomness used to generate the secret key. We present the steps used to extract the secret key from the estimated common source of randomness. We describe the metrics used to evaluate the strength of the generated key. We follow that with a qualitative comparison between different common sources of randomness along with a proposed new direction which capitalizes on hybridization of sources of randomness. We conclude by a discussion about current open research problems in secret key generation

Разработка генератора последовательностей цифровых импульсов: реферат дипломной работы / Писарик Ирина Владимировна; БГУ, Факультет радиофизики и компьютерных технологий, Кафедра информатики и компьютерных систем; науч. рук. Чудовский В. А.

In this study, the authors discuss relay selection schemes with the objective to minimise outage probability for a network consisting of a single source, multiple relays and a single destination. The relays are powered by radio frequency signals from the source. For a successful transmission, at least one of the relay nodes should be able to decode the source signals and have enough energy to relay the information to the destination. The authors assume that a relay node cannot decode information and harvest energy from the source signals simultaneously. The authors formulate an optimisation problem to minimise outage probability for the system. The relay selection scheme and the outage performance depend on the availability of the channel state information (CSI) on the source-relay and the relay-destination links. Based on the availability of the CSI on the relay-destination link, the authors propose relay selection schemes for different scenarios and evaluate the performance numerically. The results show that the availability of the CSI on the relay-destination link at the relay node helps to improve the outage performance considerably. The authors characterise the outage probability for the schemes analytically; and numerically compute the optimal number of relays which provide the optimal outage performance for a given scheme

Native Umbilical Defect for Laparoscopic Entry

Background: The presence of defects in native umbilical in adults and its use as laparoscopic first entry site is poorly documented. It would likely be a safer method than the Veress needle and direct trocar insertion. This work aimed to report the prevalence and size of native umbilical defects, and their relationship with gender, age and body mass index. Methods: In 160 consecutive laparoscopic operations, a trans-umbilical incision was made and a defect at its base was looked for. When found, the defect was measured and used as the first port entry site. Relationships of presence of native defects and their sizes in relation to gender, age and BMI were analyzed. Results: The prevalence of a native defect in this series was 90%. Its presence had no relation with gender, age or BMI. Its size, however, positively correlated with age and BMI. No complications were related to the defect’s use for first laparoscopic entry site. Conclusion: A native umbilical defect is present in 90% of adults. Whenever present, it is recommended for use as the first port entry site by an open technique. This method is simple and safe and avoids unnecessarily inducing another defect. Keywords: Laparoscopy, Open technique, Access, Native defect, Umbilical defec

Factors Affecting Outcomes of COVID-19 Infection among Older Adults with Type 2 Diabetes: A Single Center, Cross-Sectional Study

Objective: COVID-19 infection and the factors affecting it are major concerns worldwide. This retrospective study aimed to investigate clinical, laboratory and radiological characteristics associated with disease severity and hospitalization among older adults with type 2 diabetes mellitus (T2D) with COVID-19. Materials and methods: A retrospective case series study was conducted to review the records of older adults with T2D infected with COVID-19. Sociodemographic, COVID-19-related data, laboratory tests at the time of COVID-19 diagnosis and CT findings were collected. Bivariate and multivariate regression analysis were done to determine the predictors of the studied outcome, either hospitalization or complete recovery. Results: A total of 343 patients’ records were reviewed, with a mean age of 73.6 ± 6.4 years. Most of patients had fever and cough at the time of diagnosis and ground glass opacities was found on CT in 62.1% of patients. Hospitalized patients had higher duration of diabetes, suffered more from dyspnea, body aches and chest pain, had higher HbA1c, CRP and ferritin and lower lymphocytes and hemoglobin. Fasting plasma glucose and HbA1c positively affected the duration from onset of symptoms till resolution, while hemoglobin level negatively affected it. Logistic regression analysis revealed that duration of diabetes, HbA1c, ferritin and dyspnea were significant predictors of hospitalization. Conclusions: Among older adults with T2D infected with COVID-19, poor glycemic control is associated with higher risk of hospitalization and longer duration till recovery of symptoms. Longer duration of diabetes, high serum ferritin and the presence of dyspnea are associated with higher risk for hospitalization among these patients

A roadmap toward implementing health technology assessment in Egypt

BackgroundThe Egyptian healthcare system is currently in the early phase of health technology assessment (HTA) implementation. The aim of this study is to propose an implementation roadmap based on the national healthcare system status.MethodsA survey was conducted among Egyptian healthcare sector decision-makers to assess the current and future (preferred) HTA implementation status in Egypt based on a widely used international scorecard methodology. Subsequently, interviews were conducted with experts representing middle- and top-tier management in the Egyptian healthcare system to interpret the survey results and recommend specific actions.ResultsExperts recommended more capacity-building programs for HTA and health economics. Additionally, they proposed establishing HTA units in separate healthcare authorities and merging them into a single central HTA unit in the long term. Regarding the scope of implementation, experts recommended commencing with the assessment of innovative pharmaceuticals, and thereafter, expanding the scope to cover all health technologies in the long term. Additionally, they recommended using innovative tools such as “multi-criteria decision analysis (MCDA)” for tendering, and “managed entry agreements” for reimbursement decisions. Local burden of diseases and costing studies were also recommended to facilitate the implementation of HTA.ConclusionExperts agreed that several actions are required for successful HTA implementation in Egypt, including coordination between HTA bodies, application of an explicit MCDA framework, and strengthening of local evidence generation. To implement these actions, investment in technical capacity-building is indispensable. Most experts favored using multiple and soft cost-effectiveness thresholds. Efforts should be made to publish HTA submission guidelines and timelines of the processes