Coverage of renewable powered cellular networks

Session: SS4 Energy‐Aware Communications: no. 1570002605Powering a radio access network using renewables such as wind and solar power promises dramatic reduction of the network operation cost and of the networks' carbon footprints. However, the spatial variation of the energy field can lead to fluctuation in power supplied to the network and thereby affects its coverage. To quantify the effect, the paper considers a cellular downlink network with hexagonal cells and powered by harvesting energy. The network coverage of mobiles is specified by an outage constraint. A novel model of the energy field is developed using stochastic geometry. In the model, fixed maximum energy intensity occurs at Poisson distributed locations, called energy centers; the intensities fall off from the centers following an exponential-decay function of squared distance; the energy intensity at an arbitrary location is given by the decayed intensity from the nearest energy center. First, consider single harvesters deployed on the same sites as base stations (BSs). The mobile outage probability is shown to decrease exponentially with the product of the energy-field parameters: the energy-center density and exponential rate of the energy-decay function. Next, consider distributed harvesters whose generated energy is aggregated and then re-distributed to BSs. As the number of harvesters per aggregator increases, the power supplied to each BS is shown to converge to a constant proportional to the number of harvesters per BS, which counteracts the randomness of the energy field. © 2014 IEEE.published_or_final_versio

Renewables powered cellular networks: Energy field modeling and network coverage

Powering radio access networks using renewables, such as wind and solar power, promises dramatic reduction in the network operation cost and the network carbon footprints. However, the spatial variation of the energy field can lead to fluctuations in power supplied to the network and thereby affects its coverage. This warrants research on quantifying the aforementioned negative effect and designing countermeasure techniques, motivating the current work. First, a novel energy field model is presented, in which fixed maximum energy intensity γ occurs at Poisson distributed locations, called energy centers. The intensities fall off from the centers following an exponential decay function of squared distance and the energy intensity at an arbitrary location is given by the decayed intensity from the nearest energy center. The product between the energy center density and the exponential rate of the decay function, denoted as ψ, is shown to determine the energy field distribution. Next, the paper considers a cellular downlink network powered by harvesting energy from the energy field and analyzes its network coverage. For the case of harvesters deployed at the same sites as base stations (BSs), as γ increases, the mobile outage probability is shown to scale as (cγ-πψ+p), where p is the outage probability corresponding to a flat energy field and $c$ is a constant. Subsequently, a simple scheme is proposed for counteracting the energy randomness by spatial averaging. Specifically, distributed harvesters are deployed in clusters and the generated energy from the same cluster is aggregated and then redistributed to BSs. As the cluster size increases, the power supplied to each BS is shown to converge to a constant proportional to the number of harvesters per BS. Several additional issues are investigated in this paper, including regulation of the power transmission loss in energy aggregation and extensions of the energy field model. © 2002-2012 IEEE.published_or_final_versio

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Dynamic subcarrier allocation for real-Time traffic over multiuser OFDM systems

A dynamic resource allocation algorithm to satisfy the packet delay requirements for real-time services, while maximizing the system capacity in multiuser orthogonal frequency division multiplexing (OFDM) systems is introduced. Our proposed cross-layer algorithm, called Dynamic Subcarrier Allocation algorithm for Real-time Traffic (DSA-RT), consists of two interactive components. In the medium access control (MAC) layer, the users' expected transmission rates in terms of the number of subcarriers per symbol and their corresponding transmission priorities are evaluated. With the above MAC-layer information and the detected subcarriers' channel gains, in the physical (PHY) layer, a modified Kuhn-Munkres algorithm is developed to minimize the system power for a certain subcarrier allocation, then a PHY-layer resource allocation scheme is proposed to optimally allocate the subcarriers under the system signal-to-noise ratio (SNR) and power constraints. In a system where the number of mobile users changes dynamically, our developed MAC-layer access control and removal schemes can guarantee the quality of service (QoS) of the existing users in the system and fully utilize the bandwidth resource. The numerical results show that DSA-RT significantly improves the system performance in terms of the bandwidth efficiency and delay performance for real-time services. © 2009 Fanglei Sun et al.link_to_subscribed_fulltex

How BLUE is the sky? Estimating air qualities in Beijing during the Blue Sky Day period (2008–2012) by Bayesian multi-task LSTM

For over three decades, air pollution has been a major environmental challenge in many of the fast-growing cities of the world, including Beijing, China. Given that any long-term exposure to high levels of air pollution has devastating health consequences, accurately monitoring and reporting air pollution information to the public is critical for ensuring public health and safety, while facilitating rigorous air pollution and health-related scientific research. Recent statistical research examining China’s air quality data has posed questions on data accuracy, especially data reported during the Blue Sky Day (BSD) period (2000–2012), even though the quality of publicly available air quality data in China has improved substantially over the recent years (2013–2017). Until now, no attempts have been made to re-estimate the air quality data during the BSD period. In this study, we propose a multi-task machine-learning model to re-estimate the official air quality data during the recent BSD period, from 2008 to 2012, utilizing PM2.5 data reported by the US Embassy in Beijing and proxy data covering Aerosol Optical Depth (AOD) and meteorology. Results have shown that average re-estimated daily air qualities are respectively 56% and 55% higher than the official ones, for air quality index (AQI) and AQI equivalent PM2.5, during the BSD period, from 2008 to 2012. Moreover, the re-estimated BSD air quality data exhibit reduced statistical discontinuity and irregularity. Our novel data re-estimation methodology can be used to provide more credible historical air quality data for evidence-based environmental and public health studies.This research is supported in part by the Theme-based Research Scheme of the Research Grants Council of Hong Kong, under Grant No. T41-709/17-

Integrated routing and grooming in GMPLS-based optical networks

This paper proposes an integrated routing and grooming algorithm for IP over WDM networks. Assuming a peer model in GMPLS-Based optical networks, we take into account the combined topology and resource usage information on both IP and WDM layers. Based on a clustering technique called Blocking Island Paradigm, we propose an enhanced Blocking Island Graph (BIG) network model with Blocking Island Hierarchy (BIH) to abstract network resources. The main idea of the algorithm is to keep the integrity and load balance of related Blocking Islands. We also combine a cost function in the routing algorithm to groom traffic flows into active lightpaths. The complexity of the algorithm is analyzed to show its efficiency. In the simulation, we compare the algorithm with three other integrated routing algorithms in terms of blocking probability. The three algorithms are: the integrated min-hop (IMH) routing algorithm, the maximum open capacity (MOCA) routing algorithm and the IP-WDM grooming (IWG) algorithm. Simulation results show our algorithm has the best performance.published_or_final_versio

Methabolic and immune aspects of cardiovascular disease in car drivers

Immune and hormonal status, together with metabolic syndrome (MS) clinic, were examined in 207 males - car drivers (CD) suffering arterial hypertension (AH), coronary heart disease (CHD) or their combination (mean age 47.7 ± 5. 1). In CD with MS, prevalence of subclinical hypothyrosis (41.5 %) was almost twice as high as in healthy individuals (22.2 %). Besides, among the former, increased levels of leptin, fibrinogen, ACTH, Cortisol, and decreased T-cell immunity were more prevalent than in CD with isolated AH, and in healthy people. Positive correlation between leptin level and increased body weight, TTG, insulin and triglycerides levels was observed

Occupational contact allergy: The European perspective–Analysis of patch test data from ESSCA between 2011 and 2020

Background: Occupational skin diseases have led the occupational disease statistics in Europe for many years. Especially occupational allergic contact dermatitis is associated with a poor prognosis and low healing rates leading to an enormous burden for the affected individual and for society. Objectives: To present the sensitization frequencies to the most relevant allergens of the European baseline series in patients with occupational contact dermatitis (OCD) and to compare sensitization profiles of different occupations. Methods: The data of 16 022 patients considered having OCD after patch testing within the European Surveillance System on Contact Allergies (ESSCA) network between January 2011 and December 2020 were evaluated. Patients (n = 46 652) in whom an occupational causation was refuted served as comparison group. Results: The highest percentages of OCD were found among patients working in agriculture, fishery and related workers, metal industry, chemical industry, followed by building and construction industry, health care, food and service industry. Sensitizations to rubber chemicals (thiurams, carbamates, benzothiazoles) and epoxy resins were associated with at least a doubled risk of OCD. After a decline from 2014 onwards, the risks to acquire an occupation-related sensitization to methyl(chloro)isothiazolinone (MCI/MI) and especially to methylisothiazolinone (MI) seem to increase again. Sensitization rates to formaldehyde were stable, and to methyldibromo glutaronitrile (MDBGN) slightly decreasing over time. Conclusions: Among allergens in the European Baseline Series, occupational relevance is most frequently attributed to rubber accelerators, epoxy resins and preservatives