Laura Carrea | University of Reading (original) (raw)

Papers by Laura Carrea

In this thesis, a probabilistic approach to the problem of packet forwarding in information centr... more In this thesis, a probabilistic approach to the problem of packet forwarding in information centric networks is analysed and further developed. This type of networks are based on information identifiers rather than on the traditional host addresses. The approach is compact forwarding where the Bloom filter is the key method for aggregating forwarding information that allows moving packets at line speed labelled with fiat identifiers. The Bloom filter reduces state at the nodes, simplifies multicast delivery and introduces new trade-offs in the traditional routing and forwarding design space. However) it is a lassy method which produces some potential bandwidth penalties, loops, packet storms, and security issues due to false positives. This thesis focuses on false posit ive control for the probabilistic in-packet forwarding method and proposes two approaches either to reduce false positives or to exploit them in a useful way. One approach consists of a mechanism to carefully select ...

This release includes polygons of 4264 waterbodies used with Calimnos v1.4. This data set is used... more This release includes polygons of 4264 waterbodies used with Calimnos v1.4. This data set is used to delineate waterbodies in the Copernicus Land Monitoring Service (Lake Water products) and the European Space Agency Lakes_cci project (Lake Water-Leaving Reflectance). The polygons are created in Well-Known-Text format, based on the ESA Land Cover CCI project Maximum Water Extent raster v4. The polygons have been manually corrected to not include upstream or downstream rivers or dams, but do not systematically exclude islands within the maximum water extent. Polygons used in the Lakes_cci (around 2000 out of 4264) have further been harmonized with the Lake Surface Water Temperature land/water mask, based on the same source. Identifiers used in this dataset refer to definitions from four sources, by the first four characters used for the filename: GLWD - numbering corresponds to the Global Lakes and Wetlands Database HYLA - numbering corresponds to the Hydrolakes database GLBL - lake ...

IEICE Proceeding Series

Information-Centric Networking (ICN) is a new communication paradigm that shifts the focus from c... more Information-Centric Networking (ICN) is a new communication paradigm that shifts the focus from content location to content objects themselves. Users request the content by its name or some other form of identifier. Then, the network is responsible for locating the requested content and sending it to the users. Despite a large number of works on ICN in recent years, the problem of scalability of ICN systems has not been studied and addressed adequately. This is especially true when considering real-world deployments and the so-called alternative networks such as community networks. In this work, we explore the applicability of ICN principles in the challenging and unpredictable environments of community networks. In particular, we focus on stateless content dissemination based on Bloom filters (BFs). We highlight the scalability limitations of the classical single-stage BF based approach and argue that by enabling multiple BF stages would lead to performance enhancements. That is, a multi-stage BF based content dissemination mechanism could support large network topologies with heterogeneous traffic and diverse channel conditions. In addition to scalability improvements, this approach also is more secure with regard to Denial of Service attacks.

Day-to-day variations in surface air temperature affect society in many ways; however, daily surf... more Day-to-day variations in surface air temperature affect society in many ways; however, daily surface air temperature measurements are not available everywhere. A global daily analysis cannot be achieved with measurements made in situ alone, so incorporation of satellite retrievals is needed. To achieve this, we must develop an understanding of the relationships between traditional (land and marine) surface air temperature measurements and retrievals of surface skin temperature from satellite measurements, i.e. Land Surface Temperature, Ice Surface Temperature, Sea Surface Temperature and Lake Surface Water Temperature. These relationships can be derived either empirically or with the help of a physical model. Here we discuss the science needed to produce a fully-global daily analysis (or ensemble of analyses) of surface air temperature on the centennial scale, integrating different ground-based and satellite-borne data types. Information contained in the satellite retrievals would b...

ArXiv, 2016

The Bloom filter (BF) is a space efficient randomized data structure particularly suitable to rep... more The Bloom filter (BF) is a space efficient randomized data structure particularly suitable to represent a set supporting approximate membership queries. BFs have been extensively used in many applications especially in networking due to their simplicity and flexibility. The performances of BFs mainly depends on query overhead, space requirements and false positives. The aim of this paper is to focus on false positives. Inspired by the recent application of the BF in a novel multicast forwarding fabric for information centric networks, this paper proposes the yes-no BF, a new way of representing a set, based on the BF, but with significantly lower false positives and no false negatives. Although it requires slightly more processing at the stage of its formation, it offers the same processing requirements for membership queries as the BF. After introducing the yes-no BF, we show through simulations, that it has better false positive performance than the BF.

arXiv: Optics, 2013

Geometric Polarimetry has recently been introduced as a new analytical framework to express funda... more Geometric Polarimetry has recently been introduced as a new analytical framework to express fundamental relationships in polarimetry, characterizing these in geometric terms which guarantees their invariance with respect to spatial reference frame and choice of basis. It was shown via a rigorous derivation from Maxwell's equations that there is a formal argument for representing elementary coherent states algebraically as spinors, and geometrically as generators of the Poincare' sphere. While it was only considered the characterization of field states, there is in remote sensing contexts a corresponding need also to characterize the polarization states of antennas. This needs to be completely generic and not dependent on the detailed structure of the antenna. This paper presents a derivation based on Schelkunov's reaction theorem which fulfils these requirements. The statement of the theorem is translated from its usual form to a tensor representation, and this is finall...

Bulletin of the American Meteorological Society, 2021

For reasons other than the climate, 2020 was an extraordinary year. The COVID-19 pandemic has aff... more For reasons other than the climate, 2020 was an extraordinary year. The COVID-19 pandemic has affected almost all of us, changing the lives of many people around the globe. While the economic disruption associated with COVID-19 led to modest estimated reductions of 6-7% (e.g., le Quere et al. 2020; Friedlingstein et al. 2020; BP Statistical Review of the World Energy 2021) in global anthropogenic carbon dioxide (CO 2) emissions, atmospheric CO 2 levels continued to grow rapidly-a reminder of its very long residence time in the atmosphere and the challenge of reducing atmospheric CO 2. As we show in this chapter, the climate has continued to respond to the resulting warming from these increases in CO 2 and other greenhouse gases such as methane and nitrous oxide, which also experienced record increases in 2020. The year 2020 was one of the three warmest since records began in the mid-to-late 1800s, with global surface temperatures around 0.6°C above the 1981-2010 average, despite the El Niño-Southern Oscillation progressing from neutral to La Niña conditions by August (see section 4b). Lower tropospheric temperatures matched those from 2016, the previous warmest year. Meanwhile, stratospheric temperatures continued to cool as a result of anthropogenic CO 2 increases. Along with the above-average surface temperatures, an unprecedented (since instrumental records began) geographic spread of heat waves and warm spells occurred. Antarctica observed its highest temperature on record (18.3°C) at Esperanza in February. In August, Death Valley, California, reported the highest temperature observed anywhere on Earth since 1931 (preliminary value of 54.4°C). Consequently, many permafrost measurement sites experienced their highest temperatures on record; Northern Hemisphere (NH) snow cover was below the 51-year average and the fourthleast extensive on record. Glaciers in alpine regions experienced their 33rd consecutive year of negative mass balance and 12th year of average losses of more than 500 mm depth. On average, NH lakes froze over 3 days later and thawed 5.5 days earlier than the 1981-2010 average during the 2019/20 winter, which was the third-shortest ice cover season since 1979/80. The atmosphere responded to higher temperatures accordingly by holding more water. Total column water vapor was high relative to the 1981-2010 average, ranging from 0.75 to 1.06 mm over ocean and 0.58 to 0.94 mm over land, but did not reach the record values of 2016. At the surface, specific humidity over oceans was at record high levels (0.23 to 0.41 g kg −1) and was well above average over land (0.14 to 0.36 g kg −1). Conversely, relative humidity was well below average over land (-1.28 to-0.68 %rh), continuing the long-term declining trend. Precipitation increased compared to 2019, driven largely by land values, but there were few exceptional extreme precipitation events, coupled with below-average cloudiness over most of the land. More lakes showed positive water level anomalies than 2019, and in East Africa, Lake Victoria's level rose by over a meter due to a wet long-rains season. Soil moisture and terrestrial water storage showed stronger regional variations than in previous years, with East Africa and India being especially moist. Global drought area continued to increase for most of the year, reaching a peak in October, with the third-highest global land area experiencing extreme drought according to the Palmer Drought

Bulletin of the American Meteorological Society, 2020

Day-to-day variations in surface air temperature affect society in many ways, but daily surface a... more Day-to-day variations in surface air temperature affect society in many ways, but daily surface air temperature measurements are not available everywhere. Therefore, a global daily picture cannot be achieved with measurements made in situ alone and needs to incorporate estimates from satellite retrievals. This article presents the science developed in the EU Horizon 2020–funded EUSTACE project (2015–19, www.eustaceproject.org) to produce global and European multidecadal ensembles of daily analyses of surface air temperature complementary to those from dynamical reanalyses, integrating different ground-based and satellite-borne data types. Relationships between surface air temperature measurements and satellite-based estimates of surface skin temperature over all surfaces of Earth (land, ocean, ice, and lakes) are quantified. Information contained in the satellite retrievals then helps to estimate air temperature and create global fields in the past, using statistical models of how s...

Inland Waters, 2020

In 2018 Europe experienced the warmest May-October (Northern Hemisphere Warm Season) since air te... more In 2018 Europe experienced the warmest May-October (Northern Hemisphere Warm Season) since air temperature records began. In this study, we ran model simulations for 46,557 lakes across Europe to investigate the influence of this heatwave on surface water temperature. We validated the model with satellite-derived lake surface temperatures for 115 lakes from 1995 to 2018. Using the validated model, we demonstrated that, during May-Oct 2018, mean and maximum lake surface temperatures were 1.5°C and 2.4°C warmer than the base-period average (1981-2010). A lake model experiment demonstrated that, on average, the increase in air temperature was the dominant driver of surface water temperature change. However, in some lake regions, other meteorological forcing had a greater influence. Notably, higher than average solar radiation and lower than average wind speed exacerbated the influence of the heatwave on lake surface temperature in many regions, particularly Fennoscandia and Western Europe. To place our results in the context of projected 21 st century climate change, we then ran the lake model with input data from state-of-the-art climate model projections under three emissions scenarios. Under the scenario with higher emissions (Representative Concentration Pathway 8.5), we demonstrated that by the end of the 21 st century, the lake surface temperatures that occurred during the heatwave of 2018 will become increasingly common across many lake regions in Europe.

Bulletin of the American Meteorological Society, 2019

Editor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-res... more Editor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.

Bulletin of the American Meteorological Society, 2018

Editor’s note: For easy download the posted pdf of the State of the Climate for 2018 is a low-res... more Editor’s note: For easy download the posted pdf of the State of the Climate for 2018 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.

IEEE Transactions on Antennas and Propagation, 2017

IEEE Transactions on Geoscience and Remote Sensing, 2017

2016 10th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP), 2016

Among the new communication paradigms recently proposed, information-centric networking (ICN) is ... more Among the new communication paradigms recently proposed, information-centric networking (ICN) is able to natively support content awareness at the network layer shifting the focus from hosts (as in traditional IP networks) to information objects. In this paper, we exploit the intrinsic content-awareness ICN features to design a novel multi-source routing mechanism. It involves a new network entity, the ICN mediator, responsible for locating and delivering the requested information objects that are chunked and stored at different locations. Our approach imposes very limited signalling overhead, especially for large chunk sizes (MBytes). Simulations show significant latency reduction compared to traditional routing approaches.

Scientific Data

A consistent dataset of lake surface water temperature, ice cover, water-leaving reflectance, wat... more A consistent dataset of lake surface water temperature, ice cover, water-leaving reflectance, water level and extent is presented. The collection constitutes the Lakes Essential Climate Variable (ECV) for inland waters. The data span combined satellite observations from 1992 to 2020 inclusive and quantifies over 2000 relatively large lakes, which represent a small fraction of the number of lakes worldwide but a significant fraction of global freshwater surface. Visible and near-infrared optical imagery, thermal imagery and microwave radar data from satellites have been exploited. All observations are provided in a common grid at 1/120° latitude-longitude resolution, jointly in daily files. The data/algorithms have been validated against in situ measurements where possible. Consistency analysis between the variables has guided the development of the joint dataset. It is the most complete collection of consistent satellite observations of the Lakes ECV currently available. Lakes are o...

13th International Conference on Microwaves, Radar and Wireless Communications. MIKON - 2000. Conference Proceedings (IEEE Cat. No.00EX428), 2000

The aim of this work is to develop a coherent polarimetric model and to find a geometrical descri... more The aim of this work is to develop a coherent polarimetric model and to find a geometrical description of a monochromatic wave. The spinor form of the electrical field, its links to the coherency matrix and the Poincare' sphere are introduced with the aim to obtain a geometrical representation of the spinor. It consists, from the "polarization point of view", on the polarization vector and a tangential plane to the Poincare' sphere where it is possible to visualize the zero phase.

14th International Conference on Microwaves, Radar and Wireless Communications. MIKON - 2002. Conference Proceedings (IEEE Cat.No.02EX562), 2002

ABSTRACT The concept of scattering is one of the mechanisms that polarimetry seeks to express thr... more ABSTRACT The concept of scattering is one of the mechanisms that polarimetry seeks to express through data. A multiplicative decomposition of the scattering matrix is developed and it is applied to the polarimetric image of a guard-rail. The image contains just one scattering center and so it results are particularly suitable to investigate the information that the polarimetric property of an object can deliver.

15th International Conference on Microwaves, Radar and Wireless Communications (IEEE Cat. No.04EX824), 2004

... Laura Carrea*, Gerd Wanielik*, Madhu Chandra" ... Following Boerner [8] to compute t... more ... Laura Carrea*, Gerd Wanielik*, Madhu Chandra" ... Following Boerner [8] to compute the copolar nulls, and using the scattering matrix in function of the polar decomposition parameters in the symmetric case (I), (6), (9), the angle < between the copolar nulls p1 and p2 is just a ...

Geoscience Data Journal, 2015