In this thesis, a study of the capacity of a suggested three - dimensional Air-to-Ground cellular system is being made. The Outside Cell Interference Factor (OCIF) is being calculated through simulations for reverse and forward link using seven loops, from the interfering cells around the desired cell for different values of the maximum height of the cell and its radius. Capacity per cell as well as delay and throughput for packet data transmission was calculated for the first time through closed form equations, with the use of the load factor, the activity factor and sectoring gain using the Automatic Repeat Request (ARQ) algorithm for the correction of errors. Moreover, in this thesis, the algorithm which has been created is being analyzed and used for the simulations. Moreover, for the first time, a case study has been made involving the study of capacity of the Air – to - Ground system for the airports of Greece, in three basic scenarios in which the number of the users, the delay and the throughput per cell is being calculated. In the first scenario, we are restricting to the three major airports of the country, while in the second it expands to six airports covering from the radio-coverage side almost all Greece. In the first two scenarios the same cell radius of 175 km is being used, while in the third the radius is reduced to 100 km and the airports are increased to nineteen. In all three scenarios we assume that all the users use the same service. The voice services are also studied of 12.2 kbps and data with transmission rate 64, 128 and 384 kbps. From scenarios 1 and 2 (cell radius 175 km), it was found that we can service at the same time up to 179 voice subscribers per cell at bit rate 12.2 kbps which reduces to 33 users for video call of 64 kbps and in 18 for video call of 128 kbps. In scenario 3 (cell radius 100km),it was found that we can serve at the same time until 126 voice subscribers per cell at bit rate 12.2 kbps which reduces to 23 users for video call of the 64 kbps and in 13 for video call of 128 kbps. In scenario 3 although the capacity per cell is lower than in scenarios 1 and 2, it provides greater total capacity (for all Greece) in relation to these scenarios.

Unmanned Aerial Vehicles (UAV) are expected to be deployed both by government and industry. Rules for integrating commercial UAVs into a nation's airspace still need to be defined, safety being the main concern. As part of this thesis, the communication needs of UAVs as important requirement for UAV integration into the national airspace is considered. Motivated by recent prediction of UAV quantities, revealing the importance of Micro UAVs (MAV) and Small UAVs (SUAV), the thesis determines spectral requirements for control and non-payload communication (CNPC). We show that spectral efficiency, particularly in the downlink, is critical to the large-scale deployment of UAVs. Due to the limited range of small SUAV and MAV systems, communication between air and ground elements of these UAVs is established through radio Line-of-Sight (LoS) links. Ultimately, efficient LoS UAV systems are based on a better understanding of channels in the downlink, i.e. air-to-ground (A2G) channels, and also on efficient waveform as well as spectrum management implementation. Because of limited research in wideband aeronautical channel modeling, we have derived an A2G channel prototype applicable to SUAV and MAV. As part of the research at Wire- less@VT in designing and prototyping Orthogonal Frequency Division Multiplexing (OFDM) waveforms, this thesis derives the optimal parameters for SUAV and MAV A2G channels. Finally, the thesis discusses concepts that relate flight route with spectrum management as well as opportunities for a more dynamic spectrum allocation for UAV communication systems. / Master of Science

Unmanned Aerial Vehicles (UAVs) connected to cellular networks present novel challenges and opportunities in mobility management and localization, distinct from those faced by terrestrial users. This thesis presents an integrated approach, combining two key aspects essential for the integration of UAVs with cellular networks. Firstly, it introduces the mobility management challenges for cellular-connected UAVs, which differ significantly from terrestrial users. While terrestrial mobility management primarily aims to prevent radio link failures near cell boundaries, aerial users experience fragmented and overlapping coverage with line-of-sight conditions involving multiple ground base stations (BSs). Thus, mobility management for UAVs extends beyond link failure avoidance, aiming to minimize unnecessary handovers while ensuring extended service availability, particularly in up-link communication. Line-of-sight conditions from a UAV to multiple BSs increase the likelihood of frequent handovers, resulting in control packet overheads and communication delays. This thesis proposes two approaches to address these challenges: 1) A model-based service availability-aware Mobility Robustness Optimization (MRO) adapting handover parameters to maintain high service availability with minimal handovers, and 2) A model-free approach using Deep Q-networks to decrease unnecessary handovers while preserving high service availability. Simulation results demonstrate that both the proposed algorithms converge promptly and increase the service availability by more than 40 %  while the number of handovers is reduced by more than 50%  as compared to traditional approaches. Secondly, to assess the ability of a network to support the range-based localization for cellular-connected UAVs, an analytical framework is introduced. The metric B-localizability is defined as the probability of successfully receiving localization signals above a specified Signal-to-Interference plus Noise Ratio (SINR) threshold from at least B ground BSs. The framework, accounting for UAV-related parameters in a three-dimensional environment, provides comprehensive insights into factors influencing localizability, such as distance distributions, path loss, interference, and received SINR. Simulation studies explore the correlation between localizability and the number of participating BSs, SINR requirements, air-to-ground channel characteristics, and network coordination. Additionally, an optimization problem is formulated to maximize localizability, investigating the impact of UAV altitude across different scenarios. Our study reveals that in an urban macro environment, the effectiveness of cellular network-based localization increases with altitude, with localizability reaching 100% above 60 meters. This finding indicates that utilizing cellular networks for UAV localization is a viable option. / Unmanned Aerial Vehicles (UAV) anslutna till cellulära nätverk presenterar nya utmaningar och möjligheter inom mobilitetshantering och lokalisering, skilda från dem som markanvändare står inför. Denna avhandling presenterar ett integrerat tillvägagångssätt, som kombinerar två nyckelaspekter som är väsentliga för integrationen av UAV:er med cellulära nätverk. För det första introducerar den mobilitetshanteringsutmaningarna för mobilanslutna UAV:er, som skiljer sig avsevärt från markbundna användare. Medan markbunden mobilitetshantering i första hand syftar till att förhindra radiolänkfel nära cellgränser, upplever antennanvändare fragmenterad och överlappande täckning med siktlinjeförhållanden som involverar flera markbasstationer (BS). Mobilitetshantering för UAV sträcker sig sålunda bortom att undvika länkfel, och syftar till att minimera onödiga överlämningar samtidigt som man säkerställer utökad servicetillgänglighet, särskilt i upplänkskommunikation. Synlinjeförhållanden från en UAV till flera BS:er ökar sannolikheten för frekventa överlämningar, vilket resulterar i kontrollpaketkostnader och kommunikationsförseningar. Denna avhandling föreslår två tillvägagångssätt för att möta dessa utmaningar: 1) En modellbaserad tjänsttillgänglighetsmedveten Mobility Robustness Optimization (MRO) som anpassar parametrar för överlämning för att bibehålla hög servicetillgänglighet med minimal överlämning, och 2) Ett modellfritt tillvägagångssätt med Deep Q- nätverk för att minska onödiga överlämningar samtidigt som hög servicetillgänglighet bibehålls. Simuleringsresultat visar att båda de föreslagna algoritmerna konvergerar snabbt och ökar tjänstens tillgänglighet med mer än 40% medan antalet överlämningar minskas med mer än 50% jämfört med traditionella metoder. För det andra, för att bedöma förmågan hos ett nätverk att stödja den räckviddsbaserade lokaliseringen för de cellulärt anslutna UAV:erna, introduceras ett analytiskt ramverk.Metriska B-lokaliseringsförmågan definieras som sannolikheten för att framgångsrikt ta emot lokaliseringssignaler över en specificerad signal-till-interferens plus brusförhållande (SINR) tröskel från minst B jord BSs.Ramverket, som tar hänsyn till UAV-relaterade parametrar i en tredimensionell miljö, ger omfattande insikter i faktorer som påverkar lokaliserbarhet, såsom avståndsfördelningar, vägförlust, störningar och mottagen SINR. Simuleringsstudier undersöker korrelationen mellan lokaliserbarhet och antalet deltagande BS:er, SINR-krav, luft-till-mark-kanalegenskaper och nätverkskoordination. Dessutom har ett optimeringsproblem formulerats för att maximera lokaliseringsförmågan, undersöka effekten av UAV-höjd över olika scenarier. Vår studie avslöjar att i en urban makromiljö ökar effektiviteten av mobilnätsbaserad lokalisering med höjden, med lokaliserbarhet som når 100% över $60$ meter. Detta fynd indikerar att användning av mobilnät för UAV-lokalisering är ett gångbart alternativ. / <p>QC 20240319</p>

Permanent connectivity to the Internet has become the defacto standard in the second decade of the 21st century. However, on-board aircraft connectivity is still limited. While the number of airlines offering in-flight connectivity increases, the current performance is insufficient to satisfy several hundreds of passengers simultaneously. There are several options to connect aircraft to the ground, i.e. direct air-to-ground, satellites and relaying via air-to-air links. However, each single solution is insufficient. The direct air-to-ground coverage is limited to the continent and coastal regions, while the satellite links are limited in the minimum size of the spot beams and air-to-air links need to be combined with a link to the ground. Moreover, even if a direct air-to-ground or satellite link is available, the peak throughput offered on each link is rarely achieved, as the capacity needs to be shared with other aircraft flying in the same coverage area. The main challenge in achieving a high throughput per aircraft lies in the throughput allocation. All aircraft should receive a fair share of the available throughput. More specifically, as an aircraft contains a network itself, a weighted share according to the aircraft size should be provided. To address this problem, an integrated air-to-ground network, which is able to provide a high throughput to aircraft, is proposed here. Therefore, this work introduces a weighted-fair throughput allocation scheme to provide such a desired allocation. While various aspects of aircraft connectivity are studied in literature, this work is the first to address an integrated air-to-ground network to provide high-throughput connectivity to aircraft. This work models the problem of throughput allocation as a mixed integer linear program. Two throughput allocation schemes are proposed, a centralized optimal solution and a distributed heuristic solution. For the optimal solution, two different objectives are introduced, a max-min-based and a threshold-based objective. The optimal solution is utilized as a benchmark for the achievable throughput for small scenarios, while the heuristic solution offers a distributed approach and can process scenarios with a higher number of aircraft. Additionally, an option for weighted-fair throughput allocation is included. Hence, large aircraft obtain a larger share of the throughput than smaller ones. This leads to fair throughput allocation with respect to the size of the aircraft. To analyze the performance of throughput allocation in the air-to-ground network, this work introduces an air-to-ground network model. It models the network realistically, but independent from specific network implementations, such as 5G or WiFi. It is also adaptable to different scenarios. The aircraft network is studied based on captured flight traces. Extensive and representative parameter studies are conducted, including, among others, different link setups, geographic scenarios, aircraft capabilities, link distances and link capacities. The results show that the throughput can be distributed optimally during high-aircraft-density times using the optimal solution and close to optimal using the heuristic solution. The mean throughput during these times in the optimal reference scenario with low Earth orbit satellites is 20 Mbps via direct air-to-ground links and 4 Mbps via satellite links, which corresponds to 10.7% and 1.9% of the maximum link throughput, respectively. Nevertheless, during low-aircraft-density times, which are less challenging, the throughput can reach more than 200 Mbps. Therefore, the challenge is on providing a high throughput during high-aircraft-density times. In the larger central European scenario, using the heuristic scheme, a minimum of 22.9 Mbps, i.e. 3.2% of the maximum capacity, can be provided to all aircraft during high-aircraft-density times. Moreover, the critical parameters to obtain a high throughput are presented. For instance, this work shows that multi-hop air-to-air links are dispensable for aircraft within direct air-to-ground coverage. While the computation time of the optimal solution limits the number of aircraft in the scenario, larger scenarios can be studied using the heuristic scheme. The results using the weighted-fair throughput allocation show that the introduction of weights enables a user-fair throughput allocation instead of an aircraft-fair throughput allocation. As a conclusion, using the air-to-ground model and the two introduced throughput allocation schemes, the achievable weighted-fair throughput per aircraft and the respective link choices can be quantified.

This dissertation presents research performed in the areas of radio wave propagation measurement and modeling, smart antenna arrays, and software-defined radio development. A four-channel, wideband, software-defined receiver was developed to serve as a test bed for wideband measurements and antenna array experiments. This receiver was used to perform vector channel measurements in terrestrial and air-to-ground environments using an antenna array. ent results served as input to radio channel simulations based on three geometric channel models. The simulation results were compared to measurement results to evaluate the performance of the radio channel models under test. Criteria for evaluation include RMS delay spread, excess delay spread, signal envelope fading, antenna diversity gain, and gain achieved through the use of a two-dimensional rake receiver. This research makes contributions to the wireless communications field through analysis, development, measurement, and simulation that builds upon past theoretical and experimental results. Contributions include a software-defined radio architecture, based on object oriented techniques, that has been developed and successfully demonstrated using the wideband receiver. This research has produced new wideband vector channel measurements to provide extensive characterization results facilitating simulation of emerging wireless technology for commercial and military communications systems. Original ways of interpreting multipath component strength and correlation for antenna arrays have been developed and investigated. A novel geometric air-to-ground ellipsoidal channel model has been developed, simulated, and evaluated. Other contributions include an evaluation of two popular radio channel models, a geometric channel simulator for producing channel impulse responses, and analytical derivation results related to channel modeling geometries and multipath channel measurement processing. In addition to new results, existing theory and earlier research results are discussed. Fundamental theory for antenna arrays, vector channels, multipath characterization, and channel modeling is presented. Contemporary issues in software radio and object orientation are described, and measurement results from other propagation research are summarized. / Ph. D.

The primary goal for the conceptual design phase of a generic air-to-ground missile is to reach an optimal external configuration which satisfies the flight performance requirements such as flight range and time, launch mass, stability, control effectiveness as well as geometric constraints imposed by the designer. This activity is quite laborious and requires the examination and selection among huge numbers of design alternatives. This thesis is mainly focused on multi objective optimization techniques for an air to-ground missile design by using heuristics methods namely as Non Dominated Sorting Genetic Algorithm and Multiple Cooling Multi Objective Simulated Annealing Algorithm. Futhermore, a new hybrid algorithm is also introduced using Simulated Annealing cascaded with the Genetic Algorithm in which the optimized solutions are passed to the Genetic Algorithm as the intial population. A trade off study is conducted for the three optimization algorithm alternatives in terms of accuracy and quality metrics of the optimized Pareto fronts.

This thesis deals with the Air to Ground Heat Exchangers (AGHEx) and their effects on the hygienic quality of the supplied air and the microbial microclimate in the interior of buildings. The theoretical part focuses on current findings and knowledge in the field of warm air heating, ventilation of the low-energy and energy passive houses and ground heat exchanger for the ventilation systems to family houses. The next chapter deals with the quality of the indoor environment and the influence on HVAC systems on the building microclimate. The experimental part of the thesis presents the results of energy simulations of operation of air to ground heat exchanger, obtained using the simplified model, and the data from long-term monitoring of experimental AGHEx built at FME BUT. Furthermore, the results of microbiological research of several already operating air to ground heat exchangers are evaluated. The research was carried out using two different sampling methods: the method using swabs taken from the pipe wall, and the sedimentation (gravimetric) method. The conclusion part mentions the practical experiences of users and knowledge of the author relating to the design, operation and use of air to ground heat exchangers.

Airplanes have different ways to connect to the ground, including satellite air-to-ground communication (SA2GC) and direct air-to-ground communication (DA2GC). Each connection/link offers a different varying amount of transmission capacity over flight time. The traffic generated in the airplane must be forwarded/sent to ground over the available links. It is however not clear how the traffic should be forwarded so that traffic quality of service (QoS) requirements are met. The thesis at hand considers this question, and implements an algorithm handling the forwarding decision with three different forwarding schemes. Those consider traffic parameters in calculating a value assigned to each traffic flow, over a combination of priority, delay requirement and the number of times a traffic flow is dropped. The forwarding algorithm relies on proposed in-flight broadband connectivity (IFBC) network traffic and air-to-ground (A2G) link models, which aim at approximating the network environment of future IFBC networks. It is shown that QoS requirements of traffic flows in terms of packet loss and delay cannot be satisfied with capacities offered by current DA2GC and SA2GC technology. For a future scenario, with higher assumed link capacities, the QoS requirements are met to a higher extent. This is shown in lower packet loss and delay experienced by the respective traffic flows. Further, it is shown that the performance can be improved with specific forwarding schemes used by the forwarding algorithm. It is also investigated how a web cache can be used as a fallback technology. For this a required web cache hit rate is found, which should be high enough to offload the network with content served from the cache. Overall, the thesis aims at proposing an efficient traffic forwarding technique, and at giving insight into an alternative if this technique fails. / Flygplan har olika sätt att ansluta till marken, inklusive satellit-mark-kommunikation (SA2GC) och direkt luft till markkommunikation (DA2GC). Varje anslutning/länk erbjuder en annan varierande mängd överföringskapacitet under flygtid. Den trafik som genereras i flygplanet måste vidarebefordras/skickas till marken över de tillgängliga länkarna. Det är emellertid inte klart hur trafiken ska vidarebefordras så att trafiksäkerhetskvaliteten (QoS) uppfylls. Avhandlingen handlar om denna fråga och implementerar en algoritm som hanterar vidarebefordringsbeslutet med tre olika vidarebefordringssystem. De betraktar trafikparametrar vid beräkning av ett värde som tilldelas varje trafikflöde, över en kombination av prioritet, fördröjningskrav och antalet gånger ett trafikflöde tappas. Vidarebefordringsalgoritmen är beroende av föreslagna bredbandsförbindelser (IFBC) i nätverk och A2G-länkmodeller, som syftar till att approximera nätverksmiljön för framtida IFBC-nätverk. Det visas att QoS-krav på trafikflöden när det gäller paketförlust och fördröjning inte kan tillgodoses med kapacitet som erbjuds av nuvarande DA2GC- och SA2GC-teknik. För ett framtida scenario, med högre antagna länkkapacitet, uppfylls QoS-kraven i högre utsträckning. Detta visas med lägre paketförlust och fördröjning som upplevs av respektive trafikflöden. Vidare är det visat att prestanda kan förbättras med specifika vidarekopplingsscheman som används av vidarebefordringsalgoritmen. Det undersöks också hur en webbcache kan användas som en återgångsteknik. För detta hittas en obligatorisk webbcache-träfffrekvens, som bör vara tillräckligt hög för att ladda upp nätverket med innehåll som serveras från cacheminnet. Sammanfattningsvis syftar uppsatsen till att föreslå en effektiv trafiköverföringsteknik och att ge insikt om ett alternativ om denna teknik misslyckas.

Providing mobile broadband (MBB) coverage to passengers in planes (and other yingobjects) has been one of the very important requirements by airline industry for sometime. With the emergence of high-capacity wireless network concepts, there is a renewedeort in dening systems based on 5G (also dened as NR, new radio) for air-to-ground(A2G) communication. When passenger planes have been taken into consideration, a fewhundreds of passengers may need to be supported, thus requiring a high-capacity backhaullink. When 5G is used for such A2G link, beamforming and other advanced physicallayer techniques can be used between the ground stations and ying objects to obtainhigh-data rate and reliable new radio link. This masters thesis work includes link andsystem level evaluations of such NR systems when beamforming, large bandwidth, higherantenna gains, coordination between ground stations, etc., are deployed. The evaluationswere carried out in Ericsson's internal state-of-the-art simulators. The study providesbaseline for system design principles for future A2G system based on NR. Also a properpropagation model for A2G communication has been identied and beamforming solutionwith other related techniques that could be used in A2G scenario have been investigated. / Att tillhandahålla mobil bredbandstäckning till passagerare i flygplan (samt andraluftburna föremål) har varit ett viktigt krav från flygsindustrin på senare tid. Medframväxten av trådlösa nätverkskoncept med hög kapacitet har en förnyad insats uppståttför att definiera system baserade på 5G (också kallat New Radio (NR)) för Airplane-to-Ground (A2G) kommunikation. För passagerarplan så kan hundratals passagerare behövatäckning, vilket kräver en backhaul-länk med hög kapacitet. När 5G används för en sådanA2G-länk så kan såkallad lobformning och andra avancerade tekniker användas mellanmarkstationerna och flygande objekt för att erhålla hög datahastighet och tillförlitlig radiolänk. I denna uppsats ingår länk- och systemnivåutvärderningar av sådana NR-systemnär lobformning, stor bandbredd, antenn-amplifikation, koordinering mellan markstationeretc utplaceras. Utvärderingarna genomfördes i Ericssons interna simulatorer. Studienger vägledning för principer inom systemdesign för framtida A2G-system baserat på NR.En lämplig utbredningsmodell för radiovågor för A2G-kommunikation har identifieratsoch en metod för lobformning och andra relaterade tekniker som kan användas i A2Gscenariothar också undersökts.

Den ökade tekniska utvecklingen och användandet av obemannade system ställer krav på en förståelse för dess inverkan på krigföringen. Urban miljö är ofta oundviklig vid markstrid och medför utmaningar som korta stridsavstånd, ökad risk för vådabekämpning och snabba stridsförlopp. Ett system som patrullrobot kan bidra till förbandens förmågor genom spaning, verkan och möjlighet till flexibel manövrering. Arbetet besvarar frågeställningen ”Hur kan patrullrobotsystem medföra militär nytta vid ett markförbands anfall i bebyggelse?” med utgångspunkt i den teoretiska referensramen militär nytta. Analysverktygen utgörs av SWOT-analyser och teorins dimensioner för militär effektivitet, militär lämplighet samt överkomlig kostnad. Syftet med arbetet är att utforska hur patrullrobotsystem kan medföra militär nytta vid anfall mot hastigt uppkomna mål. Resultatet visade att patrullrobotsystem kan anses ha flera möjligheter till att medföra militär nytta. Anledningen är främst de karaktäristiska egenskaperna gällande dess sensorer och en inbyggd verkansdel som bidrar till möjlighet för spaning och precisionsbekämpning. Det tekniska systemet har således en god övergripande förmåga att utföra uppdrag i urban miljö genom exempelvis ökad underrättelseinhämtning och reducerad risk för sidoskador. Patrullrobotsystemet tyder även ha en god förmåga att kunna interageras med andra system och bidra till en synergieffekt. Vidare är den ekonomiska faktorn oftast lägre i jämförelse med andra vapensystem som har liknande precision vid långa avstånd. Likt andra militära system är det dock av vikt att användandet övervägs och är i enlighet med de lagar, förordningar och etiska principer som är fastställda. Tydliga målsättningar underlättar ett optimerat användande av systemet. / The increased technological development and the use of unmanned systems are requiring an understanding of their impact on warfare. Urban environments are often unavoidable in ground combat and bring challenges such as short combat distances, increased risk of friendly fire and rapid combat progress. A system such as a loitering munition can contribute to the unit's abilities through reconnaissance, damage and the possibility of flexible maneuvering. This thesis report answers the question "How can loitering munition systems entail military utility in the context of a ground unit's attack in urban warfare?" based on the theoretical frame of military utility. The analysis tools consist of SWOT analysis and the theory's dimensions of military effectiveness, military suitability and affordability. The purpose is to explore how loitering munition systems can entail military utility in attacks against rapidly emerging targets. The result showed that loitering munition systems can be considered to have several opportunities to entail military utility. The reason is mainly the characteristic features regarding its sensors and a built-in warhead that contributes to the possibility of reconnaissance and precision strike. Thus, the technical system has a comprehensive ability to carry out missions in an urban environment through, for instance, increased intelligence and reduced risk of collateral damage. The loitering munition system also indicates a great ability to interact with other systems and contributes to a synergy effect. Furthermore, the economic factor is usually lower in comparison to other weapon systems with equivalent precision throughout long distances. Nonetheless, as for other military systems, it is important that the use is considered and is in accordance with the laws, regulations and ethical principles that have been established. Clear objectives make it easier to optimize the use of the system.