The application of drones, also known as unmanned aerial vehicles deployed as unmanned aerial base stations (UABSs), has received extensive interest for public safety communications (PSC) to fill the ...coverage gaps and establish ubiquitous connectivity. In this article, we design a PSC LTE-Advanced air–ground-based HetNet (AG-HetNet) that is a scenario representation of a geographical area during and after a disaster. As part of the AG-HetNet infrastructure, we have UABSs and ground user equipment (GUE) flocking together in clusters at safe places or evacuation shelters. AG-HetNet uses cell range expansion (CRE), intercell interference coordination (ICIC), and 3D beamforming techniques to ensure ubiquitous connectivity. Through system-level simulations and using a brute-force technique, we evaluate the performance of the AG-HetNet in terms of fifth-percentile spectral efficiency (5pSE) and coverage probability. We compare system-wide 5pSE and coverage probability when UABSs are deployed on a hexagonal grid and for different clustering distributions of GUEs. The results show that reduced power subframes (FeICIC) defined in 3GPP Release-11 can provide practical gains in 5pSE and coverage probability than the 3GPP Release-10 with almost blank subframes (eICIC).
Ensuring ubiquitous mission-critical public safety communications (PSC) to all the first responders in the public safety network is crucial at an emergency site. Recently, the use of unmanned aerial ...vehicles (UAVs) has received extensive interest for PSC to fill the coverage holes and establish reliable connectivity. The UAVs can be deployed as unmanned aerial base stations (UABSs) as part of a heterogeneous network (HetNet) PSC infrastructure. In this paper, we design a PSC LTE-Advanced HetNet for different path loss models and deployment mechanism for UABSs. We enhance the system-wide spectral efficiency (SE) of this PSC HetNet by apply cell range expansion (CRE) to UABSs and mitigating the inter-cell interference arising in the HetNet by applying 3GPP Release-10 enhanced inter-cell interference coordination (eICIC) and 3GPP Release-11 further-enhanced inter-cell interference coordination (FeICIC). Through Monte Carlo simulations, we compare the system-wide fifth percentile SE when UABSs are deployed on a hexagonal grid and when their locations are optimized using a genetic algorithm, while also jointly optimizing the CRE and the inter-cell interference coordination parameters. Our results show that at optimized UABS locations, reduced power subframes defined in 3GPP Release-11 can provide considerably better fifth percentile SE than the 3GPP Release-10 with almost blank subframes (eICIC).
Unmanned aerial vehicles (UAVs) can play a key role in meeting certain demands of cellular networks. UAVs can be used not only as user equipment (UE) in cellular networks but also as mobile base ...stations (BSs) wherein they can either augment conventional BSs by adapting their position to serve the changing traffic and connectivity demands or temporarily replace BSs that are damaged due to natural disasters. The flexibility of UAVs allows them to provide coverage to UEs in hot-spots, at cell-edges, in coverage holes, or regions with scarce cellular infrastructure. In this work, we study how UAV locations and other cellular parameters may be optimized in such scenarios to maximize the spectral efficiency (SE) of the network. We compare the performance of machine learning (ML) techniques with conventional optimization approaches. We found that, on an average, a double deep Q learning approach can achieve 93.46% of the optimal median SE and 95.83% of the optimal mean SE. A simple greedy approach, which tunes the parameters of each BS and UAV independently, performed very well in all the cases that we tested. These computationally efficient approaches can be utilized to enhance the network performance in existing cellular networks.
Wireless systems using low-power wireless communication protocol are rapidly gain popularity in the license-free industrial scientific, and medical (ISM) frequency bands. One such emerging trend in ...ISM frequency bands is home automation. Historically, all the home devices were once unconnected, today are now being connected either by a wired or wireless connection. The low-power wireless communication protocols enable integration of all the digital home devices into a single system and enhance end user product experience. The rapid prototyping of these end user product using programmable radio system such as software-defined radio has been the game-changer in the field of home automation. In this article, we present an overview of popular ISM bands in different regions of the world. Furthermore, we analyze the signals from the wireless electric switch using a software-defined radio in 433 MHz ISM band.
In this letter, a receding horizon path planning algorithm is introduced for unmanned aerial vehicle swarms to cooperatively localize a moving radio frequency transmitter. In the core of the proposed ...algorithm is a model to predict the Fisher information matrix. Using this prediction model, we formulate the most favorable course of action to solve the path planning using local optimization, which helps the system as a whole to achieve the goal over a finite receding horizon. The effectiveness of the proposed algorithm is demonstrated by comparing the proposed mechanism with the non-predictive cooperative technique through computer simulation. It is shown that the expected estimation error can be significantly reduced using the proposed method.
Effective emergency and natural disaster management depend on the efficient mission-critical voice and data communication between first responders and victims. Land mobile radio system (LMRS) is a ...legacy narrowband technology used for critical voice communications with limited use for data applications. Recently, long term evolution (LTE) emerged as a broadband communication technology that has a potential to transform the capabilities of public safety technologies by providing broadband, ubiquitous, and mission-critical voice and data support. For example, in the United States, FirstNet is building a nationwide coast-to-coast public safety network based on LTE broadband technology. This paper presents a comparative survey of legacy and the LTE-based public safety networks, and discusses the LMRS-LTE convergence as well as mission-critical push-to-talk over LTE. A simulation study of LMRS and LTE band class 14 technologies is provided using the NS-3 open source tool. An experimental study of APCO-25 and LTE band class 14 is also conducted using software-defined radio to enhance the understanding of the public safety systems. Finally, emerging technologies that may have strong potential for use in public safety networks are reviewed.
Unmanned aerial vehicles (UAVs) enabled networks can enhance wireless connectivity and support emerging services. However, this would require system-level understanding to modify and extend the ...existing terrestrial network infrastructure. In this study, the authors integrated UAVs as user equipment and base stations into an existing long term evolution (LTE)-Advanced heterogeneous network (HetNet) and provide system-level insights of this three-tier LTE-Advanced air-ground HetNet (AG-HetNet). The performance of AG-HetNet was evaluated through brute-force technique and heuristics algorithms in terms of the fifth percentile spectral efficiency (5pSE) and coverage probability. In particular, system-wide 5pSE and coverage probability were compared, when unmanned aerial base stations (UABSs) are deployed on a fixed hexagonal grid and when their locations are optimised using a genetic algorithm (GA) and elitist harmony search algorithm based on the genetic algorithm (eHSGA); while jointly optimising the inter-cell interference coordination (ICIC) and cell range expansion (CRE) network parameters for different ICIC techniques. The simulation results show that the heuristic algorithms (GA and eHSGA) outperform the brute-force technique and achieve better peak values of coverage probability and 5pSE. Simulation results also show that a trade-off exists between peak values and computation time when using heuristic algorithms. Furthermore, the three-tier hierarchical structuring of reduced power subframes further-enhanced ICIC (FeICIC) defined in 3GPP Rel-11 provides considerably better 5pSE and coverage probability than the 3GPP Rel-10 with almost blank subframes eICIC. They also investigated the network performance for different practical deployment heights of UABS and they found low-altitude UABSs to perform sparsely better than medium-altitude UABSs.
Ensuring ubiquitous mission-critical public safety communications (PSC) to all the first responders in the public safety network is crucial at an emergency site. The first responders heavily rely on ...mission-critical PSC to save lives, property, and national infrastructure during a natural or human-made emergency. The recent advancements in LTE/LTE-Advanced/5G mobile technologies supported by unmanned aerial vehicles (UAV) have great potential to revolutionize PSC.However, limited spectrum allocation for LTE-based PSC demands improved channel capacity and spectral efficiency. An additional challenge in designing an LTE-based PSC network is achieving at least 95% coverage of the geographical area and human population with broadband rates. The coverage requirement and efficient spectrum use in the PSC network can be realized through the dense deployment of small cells (both terrestrial and aerial). However, there are several challenges with the dense deployment of small cells in an air-ground heterogeneous network (AG-HetNet). The main challenges which are addressed in this research work are integrating UAVs as both aerial user and aerial base-stations, mitigating inter-cell interference, capacity and coverage enhancements, and optimizing deployment locations of aerial base-stations.First, LTE signals were investigated using NS-3 simulation and software-defined radio experiment to gain knowledge on the quality of service experienced by the user equipment (UE). Using this understanding, a two-tier LTE-Advanced AG-HetNet with macro base-stations and unmanned aerial base-stations (UABS) is designed, while considering time-domain inter-cell interference coordination techniques. We maximize the capacity of this AG-HetNet in case of a damaged PSC infrastructure by jointly optimizing the inter-cell interference parameters and UABS locations using a meta-heuristic genetic algorithm (GA) and the brute-force technique. Finally, considering the latest specifications in 3GPP, a more realistic three-tier LTE-Advanced AG-HetNet is proposed with macro base-stations, pico base-stations, and ground UEs as terrestrial nodes and UABS and aerial UEs as aerial nodes. Using metaheuristic techniques such as GA and elitist harmony search algorithm based on the GA, the critical network elements such as energy efficiency, inter-cell interference parameters, and UABS locations are all jointly optimized to maximize the capacity and coverage of the AG-HetNet.
Enabling seamless and mission critical voice and data services is a key requirement for public safety networks during the emergency and natural disaster scenarios. The ability to save lives depends ...on the reliable and effective communication amongst the first responders and victims. Land Mobile Radio System (LMRS) is a legacy technology which has been used for public safety communication scenarios for decades. It has been designed as a narrowband technology for critical voice communications with limited use for data applications. With the evolution of broadband technologies that enable wideband data transmission, there is a significant potential to transform the capabilities of public safety communication technologies. In the United States, FirstNet is building a nationwide public safety communication system that uses band class 14 and the broadband Long Term Evolution (LTE) systems, which is designed for broadband voice and data to ensure reliable and high-quality services at all times. This paper presents a study of legacy public safety networks and the FirstNet system that is based on the LTE technology. A simulation study of LTE band class 14 environment is also provided using the NS-3 simulation environment.
Unmanned aerial vehicles (UAVs) can supplement the existing ground-based heterogeneous cellular networks (Het-Nets), by replacing/supporting damaged infrastructure, providing real-time video support ...at the site of an emergency, offloading traffic in congested areas, extending coverage, and filling coverage gaps. In this paper, we introduce distributed algorithms that leverage UAV mobility, enhanced inter-cell interference coordination (ICIC), and cell range expansion (CRE) techniques defined in 3GPP Release-10 and 3GPP Release-11. Through Monte-Carlo simulations, we compare the system-wide 5th percentile spectral efficiency (5pSE) while optimizing the performance using a brute force algorithm, a heuristic-based sequential algorithm, and a deep Q-learning algorithm. The autonomous UAVs jointly optimize their location, ICIC parameters, and CRE to maximize 5pSE gains and minimize the outage probability. Our results show that the ICIC technique relying on a simple heuristic outperforms the ICIC technique based on deep Q-learning. Taking advantage of the multiple optimization parameters for interference coordination, the heuristic based ICIC technique can achieve 5pSE values that are reasonably close to those achieved with exhaustive brute force search techniques, at a significantly lower computational complexity.
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