Enabling On-Demand Cyber-Physical Control Applications with UAV Access Points

Achieving cyber-physical control over a wireless channel requires satisfying both the timeliness of a single packet and preserving the latency reliability across several consecutive packets. To satisfy those requirements as an ubiquitous service requires big infrastructural developments, or flexible on-demand equipment such as UAVs. To avoid the upfront cost in terms of finance and energy, this paper analyzes the capability of UAV access points (UAVAPs) to satisfy the requirements for cyber-physical traffic. To investigate this, we perform a Gilbert-Eliott burst-error analysis that is analytically derived as a combination of two separate latency measurement campaigns and provide an upper-bound analysis of the UAVAP system. The analysis is centered around a UAVAP that uses its LTE connection to reach the backhaul, while providing service to ground nodes (GNs) with a Wi-Fi access point (AP). Thus, we combine both measurement campaigns to analyze the plausibility of the described setup in casual, crowded or mixed network settings.Comment: To be published in proceedings of VTC-fall 202

Effect of data scaling on color device model fitting

Output devices in print production can be characterized by different characterization methods. One commonly used method of color device characterization is least squares fitting. In essence, the least squares fitting is used to determine the coefficients of a predetermined polynomial, such that the sum of squared differences between the values predicted by the model and the empirical data is minimal. The choice of the polynomial order and the cross product terms which best describe the behavior of a certain device is not obvious. This paper is a part of a larger study which investigates the criteria in the measurement data which can be used for optimal model selection. The part of the study covered in this paper addresses the data over fitting problem. It is investigated by comparing the performance of models of different polynomial orders on two different domains.Peer Reviewe

Dynamic Standalone Drone-Mounted Small Cells

This paper investigates the feasibility of Dynamic Horizontal Opportunistic Positioning (D-HOP) use in Drone Small Cells (DSCs), with a central analysis on the impact of antenna equipment efficiency onto the optimal DSC altitude that has been chosen in favor of maximizing coverage. We extend the common urban propagation model of an isotropic antenna to account for a directional antenna, making it dependent on the antenna's ability to fit the ideal propagation pattern. This leads us to define a closed-form expression for calculating the Rate improvement of D-HOP implementations that maintain constant coverage through antenna tilting. Assuming full knowledge of the uniformly distributed active users' locations, three D-HOP techniques were tested: in the center of the Smallest Bounding Circle (SBC); the point of Maximum Aggregated Rate (MAR); and the Center-Most Point (CMP) out of the two aforementioned. Through analytic study and simulation we infer that DSC D-HOP implementations are feasible when using electrically small and tiltable antennas. Nonetheless, it is possible to achieve average per user average rate increases of up to 20-35% in low user density scenarios, or 3-5% in user-dense scenarios, even when using efficient antennas in a DSC that has been designed for standalone coverage.Comment: To be published in proceedings of EuCNC'2

On Addressing Heterogeneity in Federated Learning for Autonomous Vehicles Connected to a Drone Orchestrator

In this paper we envision a federated learning (FL) scenario in service of amending the performance of autonomous road vehicles, through a drone traffic monitor (DTM), that also acts as an orchestrator. Expecting non-IID data distribution, we focus on the issue of accelerating the learning of a particular class of critical object (CO), that may harm the nominal operation of an autonomous vehicle. This can be done through proper allocation of the wireless resources for addressing learner and data heterogeneity. Thus, we propose a reactive method for the allocation of wireless resources, that happens dynamically each FL round, and is based on each learner’s contribution to the general model. In addition to this, we explore the use of static methods that remain constant across all rounds. Since we expect partial work from each learner, we use the FedProx FL algorithm, in the task of computer vision. For testing, we construct a non-IID data distribution of the MNIST and FMNIST datasets among four types of learners, in scenarios that represent the quickly changing environment. The results show that proactive measures are effective and versatile at improving system accuracy, and quickly learning the CO class when underrepresented in the network. Furthermore, the experiments show a tradeoff between FedProx intensity and resource allocation efforts. Nonetheless, a well adjusted FedProx local optimizer allows for an even better overall accuracy, particularly when using deeper neural network (NN) implementations

Research of armament application on light ground wheeled vehicles

Dat je pregled i analiza performansi lakih vojnih terenskih točkaških vozila (LVTTV), lakih komercijalnih terenskih točkaških vozila (LKTTV) u Pik-ap verziji i postojećih sistema naoružanja pogodnih za primenu na LKTTV Pik-ap verzija. Posebno je razmotrena problematika elastično-prigušnog oslanjanja naoružanja pri njegovom jediničnom dejstvu. Definisana je metodologija i projektovana je i realizovana oprema za simulaciju impulsne sile u cilju statičkih i dinamičkih ispitivanja sistema vozilo-platforma-naoružanje u laboratorijskim uslovima. Prikazan je postupak ispitivanja pri statičkom opterećenju sistema i dinamičkih ispitivanja sistema vozilo-platforma-naoružanje u uslovima kontinuirane impulsne sile u cilju odredjivanja pomeranja šasije u zonama točkova i napona u šasiji vozila i osloncima platforme za prihvat naoružanja. Postavljen je matematički model sistema vozilo-platforma-naoružanje i data teorijska pomeranja šasije vozila u zonama točkova pri jediničnoj impulsnoj sili odnosno impulsu.The review and analysis of the performances of military ground wheeled vehicles (LVTTV), light commercial wheeled ground vehicles (LKTTV) of Pick-up version and current systems of armament convenient for the application on LKTTV Pick-up versions, were given. The issues of elastic-absorbtion suspension of armament during its single shooting function was analised in detail. The methodology was defined, the equipment for the simulation of impulse force was designed and realised with purpose of static and dynamic tests of the vehicle-platform-armament system in the laboratory conditions. The test procedure of static and dynamic loads of system vehicle-platform-armament in conditions of continual impulse force was presented. The aim of these tests was the determination of motion of vehicle chassis in the stress of vehicle chassis and platform supports for the armament. The mathematical model of vehicle-platform-armamaent system was defined and theoretical motions of vehicle chassis in the wheels zones under the single impulse force, were given

Optimizacija modela izlaznih uređaja u grafičkoj reprodukciji

Prijelazom postupaka grafičke reprodukcije s konvencionalnih na digitalne, koji je započeo u drugoj polovici 80‐ih godina 20.st., otvorio se prostor razvoju različitih tehnologija. Tada su različiti proizvođači softvera i opreme razvijali vlastite sustave upravljanja bojama. Kako su ti sustavi bili ograničeni na platforme i softverske pakete za koje su bili razvijeni, proizvođači su 1993.g. osnovali Međunarodni konzorcij za boje (ICC – International Color Consortium), s ciljem razvoja univerzalnog sustava upravljanja bojama, neovisnog o platformi, operacijskom sustavu i softverskim paketima. Glavna namjera je bila, a i danas je, razvoj standarda zapisa profila uređaja te registracija potpisa i opisa podatkovnih struktura profila. Profili uređaja opisuju njihova svojstva reprodukcije boja, definirajući vezu između izvornog ili odredišnog prostora boja i poveznog prostora boja. Tijekom 2003.g. ICC i Tehnički odbor za grafičku tehnologiju, TC130 pri Međunarodnoj organizaciji za standarde, sklopili su ugovor kojim su se obavezali na suradnju u razvoju ISO standarda na osnovama dotadašnjeg rada ICC‐a. ICC profil je računalna datoteka, čiji je zapis i podatkovne strukture standardizirao ICC. Uz to, ICC u svojim publikacijama daje načelne smjernice za korištenje podatkovnih struktura profila prilikom karakterizacije uređaja. No, to je sve što je kod tih datoteka standardizirano. Kako se pri izradi profila uređaja na osnovi mjerenja izrađuje matematički model uređaja, izbor matematičke funkcije, kao i njezine raspodjele po podatkovnim strukturama profila, ostavljaju se razvojnim inženjerima softvera. Pri tome se koriste modeli za koje je dosadašnjim istraživanjima dokazano da dobro opisuju određeni tip uređaja. No, oni se u pojedinačnim slučajevima mogu pokazati nepreciznima. Razvijeni su različiti modeli za opis uređaja, a često se u tu svrhu koriste regresijski modeli. Polinom proizvoljnog, unaprijed zadanog reda i broja članova prilagođava se podacima u smislu najmanjih kvadratnih odstupanja. Izbor optimalnoga reda i članova za neki određeni uređaj nije očigledan. Cilj ovoga istraživanja bilo je određivanje signifikantnih članova modela za različite uređaje i pronalaženje veze između signifikantnosti pojedinih članova i karakteristika podataka o uređaju. U prvome dijelu istraživanja jednome modelu koji je odabran kao osnovni dodavani su proizvoljno odabrani članovi. Evaluacijom preciznosti na tri domene i jednom procesu utvrđeno je kako neki članovi mogu povećati, a neki smanjiti sposobnost prilagodbe i moć predviđanja modela, a učinak može biti različit na različitim domenama. U drugome dijelu istraživanja provedena su dva postupka eliminacije, eliminacija skupina članova i eliminacija članova na maksimalnim modelima za osam procesa i utvrđena je signifikantnost pojedinih članova u različitim procesima. Iako su se reducirani modeli pokazali preciznijima, zbog velikih međuovisnosti članova modela nije utvrđeno postojanje uzorka u izboru članova za pojedine procese pa ovim pristupom nije utvrđena veza između signifikantnosti članova i karakteristika podataka o uređaju

Performance Trade-Offs in Cyber–Physical Control Applications With Multi-Connectivity

Modern communication devices are often equipped with multiple wireless communication interfaces with diverse characteristics. This enables exploiting a form of multi-connectivity known as interface diversity to provide path diversity with multiple communication interfaces. Interface diversity helps to combat the problems suffered by single-interface systems due to error bursts in the link, which are a consequence of temporal correlation in the wireless channel. The length of an error burst is an essential performance indicator for cyber–physical control applications with periodic traffic, as this defines the period in which the control link is unavailable. However, the available interfaces must be correctly orchestrated to achieve an adequate trade-off between latency, reliability, and energy consumption. This work investigates how the packet error statistics from different interfaces impact the overall latency–reliability characteristics and explores mechanisms to derive adequate interface diversity policies. For this, we model the optimization problem as a partially observable Markov decision process (POMDP), where the state of each interface is determined by a Gilbert–Elliott model whose parameters are estimated based on experimental measurement traces from LTE and Wi-Fi. Our results show that the POMDP approach provides an all-round adaptable solution, whose performance is only 0.1% below the absolute upper bound, dictated by the optimal policy under the impractical assumption of full observability