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Network re-optimization is a process that must be triggered periodically in order to improve the inefficient resource allocation of online routing heuristics due to the uncertainty of online lightpath demand arrivals and departures. Network re-optimization involves two tasks: a) finding new lightpaths for a (sub)set of current demands, i.e. rerouting, and b) migrating the current traffic to the ne
As average packet sizes in wireless networks shrink and data rates increase, the fundamental CSMA mechanism in the 802.11 protocol family is put under stress. With the emerg- ing 802.11ax standard, the carrier sensing mechanism is low- ering the efficiency of the protocol to the level of random access (ALOHA), and as future-generation 802.11 standards emerge, CSMA-based protocols will fall below t
A new proof of the equivalence of the Taut String Algorithm and the one-dimensional Rudin–Osher–Fatemi model is presented. Based on duality and the projection theorem in Hilbert space, the proof is strictly elementary. Existence and uniqueness of solutions (in the continuous case) to both denoising models follow as by-products. The standard convergence properties of the denoised signal, as the reg
I syfte att utvärdera effekten av dubbdäcksförbudet på Friggagatan med avseende på luftkvaliteten har Miljöförvaltningen i Göteborg på uppdrag av trafikkontoret i Göteborg utfört luftkvalitetsmätningar på Friggagatan mellan 2013-01-01 och 2013-09-30. Dessutom utförde Miljöförvaltningen mätningar av dubbdäcksanvändningen på Friggagatan, vid Drottningtorget och i Haga. Vidare användes även mätdata f
This paper discusses the relevance of transient events of strong large-scale ocean evaporation (SLOE) for the deuteriumexcess of marine boundary layer vapor d using a theoretical framework that invokes the closure assumption. We argue that during SLOE events, d is essentially determined by the evaporation flux signature. Distinct high d during SLOE with global-mean values in the range of 12‰-23‰ d
Multi-cell wireless systems usually encounter both intra-cell and inter-cell interference, which can be mitigated via coordinated multipoint (CoMP) transmission. Previous works on multi-cell analysis in the microwave band generally consider fully digital beamforming, requiring a complete radio-frequency chain behind each antenna. This is practically infeasible for millimeter-wave (mmWave) systems
This work demonstrates the sensitivity of lens antenna arrays operating at millimeter-wave (mmWave) frequencies. Considering a Rotman lens array in receive mode, our investigation focuses on its most imperative defect: aberration of electromagnetic (EM) energy. Aberration leads to spillover of electric fields to neighboring ports, reducing the lens' ability to focus the EM energy to a desired port
Lens–based massive multiple–input multiple–output (MIMO) systems have considerable potential to reduce signal processing cost at millimeter–wave frequencies. As a result, they are able to lower the effective channel dimension via beam selection, realized with a network of radio–frequency (RF) switches. However, lens arrays suffer from the inherent quantization of the beamspace, as well as errors d
In this paper, we take a fundamental look at the interference characteristics of a lens-based millimeter-wave (mmWave) multiuser multiple-input multiple-output system (MU-MIMO) system. We consider a hybrid architecture, implemented via a bank of radio-frequency (RF) switches which perform beam selection followed by low-complexity uplink maximum-ratio combining (MRC) at baseband. Considering a Rotm
We consider a massive multiple-input multiple- output system with minimum-mean-squared-error processing on the uplink. A novel analytical framework is proposed to approximate the instantaneous signal-to-interference-plus-noise- ratio (SINR) of an arbitrary user terminal, as well as, the system sum spectral efficiency. Unlike previous studies, our methodology considers spatially correlated Ricean f
The Asian Summer Monsoons (ASM) represent the main source of precipitation in China and East Asia with about one third of the world population and a region of widespread civilizations. Identifying the temporal and spatial patterns (pathways) of these monsoonal events during the Late Holocene to today has been a matter of debate amongst the scientific community. Here we show that the distribution
We present a method for augmenting a nominal controller with a peak filter to achieve improved rejection of narrowband disturbances. The method is based on consideration of the open-loop Nyquist curve, which arguably makes it more intuitive and flexible than previous approaches. We also comment on some implementation aspects, and give an application example based on a control problem at a particle
The Northern Hemisphere experienced dramatic changes during the last glacial, featuring vast ice sheets and abrupt climate events, while high northern latitudes during the last interglacial (Eemian) were warmer than today. Here we use high-resolution aerosol records from the Greenland NEEM ice core to reconstruct the environmental alterations in aerosol source regions accompanying these changes. S
This package facilitates working with probability distributions by means of Monte-Carlo methods, in a way that allows for propagation of probability distributions through functions. This is useful for, e.g., nonlinear uncertainty propagation. A variable or parameter might be associated with uncertainty if it is measured or otherwise estimated from data. We provide two core types to represent proba
We consider the problem of feasible coordination control for multiple homogeneous or heterogeneous mobile vehicles subject to various constraints (nonholonomic motion constraints, holonomic coordination constraints, equality/inequality constraints etc). We develop a general framework involving differential-algebraic equations and viability theory to describe and determine coordination feasibility
Future internet-of-things systems need to be able to combine heterogeneous services and support weak connectivity. In this paper, we introduce ComPOS, a new domain-specific language for composing services in IoT systems. We show how Maria, a bird watcher, can use ComPOS to build a system that allows her to spy on birds in the garden while she is not at home. We demonstrate how ComPOS handles the u
Ice-core timescales are vital for the understanding of past climate; hence they should be updated whenever significant amounts of new data become available. Here, the Greenland ice-core chronology GICC05 was revised for the last 3835 years by synchronizing six deep ice cores and three shallow ice cores from the central Greenland ice sheet. A new method was applied by combining automated counting o
The widely accepted “Milankovitch theory” explains insolation-induced waxing and waning of the ice sheets and their effect on the global climate on orbital timescales. In the past half century, however, the theory has often come under scrutiny, especially regarding its “100-ka problem.” Another drawback, but the one that has received less attention, is the “monsoon problem,” which pertains to the
Understanding atmospheric response to radiative forcing, including the intensity and distribution of wind patterns is critical as this might have important implications in the coming decades. Long-term episodes of reduced solar activity (i.e. Grand Solar Minima, GSM) have triggered rapid climate change in the past, recorded in proxy-based records, including varved sediments from Meerfelder Maar, G
