Dynamic Hierarchical Cache Management for Cloud RAN and Multi- Access Edge Computing in 5G Networks

Cloud Radio Access Networks (CRAN) and Multi-Access Edge Computing (MEC) are two of the many emerging technologies that are proposed for 5G mobile networks. CRAN provides scalability, flexibility, and better resource utilization to support the dramatic increase of Internet of Things (IoT) and mobile devices. MEC aims to provide low latency, high bandwidth and real- time access to radio networks. Cloud architecture is built on top of traditional Radio Access Networks (RAN) to bring the idea of CRAN and in MEC, cloud computing services are brought near users to improve the user’s experiences. A cache is added in both CRAN and MEC architectures to speed up the mobile network services. This research focuses on cache management of CRAN and MEC because there is a necessity to manage and utilize this limited cache resource efficiently. First, a new cache management algorithm, H-EXD-AHP (Hierarchical Exponential Decay and Analytical Hierarchy Process), is proposed to improve the existing EXD-AHP algorithm. Next, this paper designs three dynamic cache management algorithms and they are implemented on the proposed algorithm: H-EXD-AHP and an existing algorithm: H-PBPS (Hierarchical Probability Based Popularity Scoring). In these proposed designs, cache sizes of the different Service Level Agreement (SLA) users are adjusted dynamically to meet the guaranteed cache hit rate set for their corresponding SLA users. The minimum guarantee of cache hit rate is for our setting. Net neutrality, prioritized treatment will be in common practice. Finally, performance evaluation results show that these designs achieve the guaranteed cache hit rate for differentiated users according to their SLA

Nonemergent craniotomy surgical site infection: a retrospective cohort study

Contextualização: A incidência de infeção de local cirúrgico após craniotomia (SSI-CRAN) varia amplamente e está associada com graves consequências. O objetivo deste estudo é estimar a taxa de SSI-CRAN no serviço de neurocirurgia de um centro terciário e estabelecer os seus fatores de risco. Métodos: Todos os doentes adultos consecutivos submetidos a craniotomia não emergente num centro terciário entre Janeiro 2019 a Outubro 2019 foram avaliados retrospetivamente. Dados demográficos, clínicos e cirúrgicos foram recolhidos. O outcome principal deste estudo foi o desenvolvimento de SSI-CRAN até 30 dias após cirurgia, usando as definições do European Centre for Disease Prevention and Control (eCDC). Foi realizada análise uni- e multivariada para estabelecer fatores de risco para SSI-CRAN. Resultados: Dos 271 doentes incluídos, 15 (5.5%) desenvolveram SSI-CRAN até 30 dias após cirurgia, sendo que 11 /73.3%) foram infeções de órgão-espaço. Os microorganismos mais comumente envolvidos foram cocos gram-positivo, particularmente S. epidermidis (n=4, 66,7%). Na análise univariada, ausência de normotermia (60.0% vs. 15.8% no grupo com e sem SSI-CRAN, respetivamente; p < 0.001) e leak líquido céfalo-raquidiano (LCR) (40.0% vs. 2.4%; p < 0,001) estiveram associados de forma estatisticamente significativa com o desenvolvimento de SSI-CRAN. Na análise multivariada, normotermia (OR = 0.200, IC 95% [0,058-0,687]; p = 0.011) foi o único fator protetor e leak LCR (OR = 12.152, IC 95% [2,684 - 55,010]; p = 0.001) foi o único fator de risco independente para o desenvolvimento de SSI-CRAN. Conclusão: A incidência cumulativa de SSI-CRAN até 30 dias após cirurgia foi 5.5%. Leak LCR e a ausência de normotermia foram os únicos fatores de risco independentes para o desenvolvimento de SSI-CRAN. Os dados fornecidos neste estudo podem ser considerados no desenho de estratégias preventivas promovendo a redução da incidência de infeção de local cirúrgico.Background: The incidence of surgical site infection after craniotomy (SSI-CRAN) varies widely and is associated with major consequences. The aim of this study is to estimate the SSI-CRAN rate at the neurosurgery department of a tertiary center and to establish its risk factors. Methods: All consecutive adult patients who underwent nonemergent craniotomy at a tertiary center from January 2018 to October 2019 were retrospectively assessed. Demographic, clinical and surgical data were collected. The main outcome of our study was the development of SSI within 30 days post-surgery, as defined by the European Centre for Disease Prevention and Control (eCDC) guidelines. Univariate and multivariate analysis was performed to establish risk factors for SSI-CRAN. Results: From the 271 patients enrolled in this study, 15 (5.5%) developed SSI-CRAN within 30 days post-surgery, 11 (73.3%) of which were organ-space. The most common causative microorganisms were gram-positive cocci, particularly S. epidermidis (n=4, 66.7%). In the univariate analysis, absence of normothermia (60.0% vs. 15.8% in the group with SSI-CRAN and in the group without SSI-CRAN, respectively; p < 0.001) and cerebrospinal (CSF) leakage (40.0% vs. 2.4%; p < 0,001) were associated with SSI-CRAN. In the multivariate analysis, normothermia (OR = 0.200, 95% CI [0,058-0,687]; p = 0.011) was the only protective factor and CSF leakage (OR = 12.152, 95% CI [2,684 - 55,010]; p= 0.001) was the only independent risk factors for SSI-CRAN. Conclusion: The cumulative incidence of SSI-CRAN within 30 days post-surgery was 5.5%. CSF leakage and the absence of normothermia were the only independent risk factors for SSI-CRAN. The data provided in this study can be considered in the design of preventive strategies aimed to reduce the incidence of surgical site infection

Risk factors for surgical site infection after craniotomy: a prospective cohort study

Background: Although surgical site infection after craniotomy (SSI-CRAN) is a serious complication, risk factors for its development have not been well defined. We aim to identify the risk factors for developing SSI-CRAN in a large prospective cohort of adult patients undergoing craniotomy. Methods: A series of consecutive patients who underwent craniotomy at a university hospital from January 2013 to December 2015 were prospectively assessed. Demographic, epidemiological, surgical, clinical and microbiological data were collected. Patients were followed up in an active post-discharge surveillance programm e for up to one year after surgery. Multivariate analysis was carried out to identify independent risk factors for SSI-CRAN. Results: Among the 595 patients who underwent craniotomy, 91 (15.3%) episodes of SSI-CRAN were recorded, 67 (73.6%) of which were organ/space. Baseline demographic characteristics were similar among patients who developed SSI-CRAN and those who did not. The most frequent causative Gram-positive organisms were Cutibacterium acnes (23.1%) and Staphylococcus epidermidis (23.1%), whereas Enterobacter cloacae (12.1%) was the most commonly isolated Gram-negative agent. In the univariate analysis the factors associated with SSI-CRAN were ASA score > 2 (48.4% vs. 35.5% in SSI-CRAN and no SSI-CRAN respectively, p = 0.025), extrinsic tumour (28.6% vs. 19.2%, p = 0.05), and re-intervention (4.4% vs. 1.4%, p =  2 (AOR: 2.26, 95% CI: 1.32-3.87; p = .003) and re-intervention (OR: 8.93, 95% CI: 5.33-14.96; p < 0.001) were the only factors independently associated with SSI-CRAN. Conclusion: The risk factors and causative agents of SSI-CRAN identified in this study should be considered in the design of preventive strategies aimed to reduce the incidence of this serious complication