@article{maeng_ozdemir_guvenc_sichitiu_dutta_mushi_2023, title={AERIQ: SDR-Based LTE I/Q Measurement and Analysis Framework for Air-to-Ground Propagation Modeling}, ISSN={["1095-323X"]}, DOI={10.1109/AERO55745.2023.10115787}, abstractNote={In this paper, we introduce AERIQ: a software-defined radio (SDR) based I/Q measurement and analysis framework for wireless signals for aerial experimentation. AERIQ is integrated into controllable aerial vehicles, it is flexible, repeatable, and provides raw I/Q samples for post-processing the data to extract various key parameters of interest (KPIs) over a 3D volume. Using SDRs, we collect I/Q data with unmanned aerial vehicles (UAVs) flying at various altitudes in a radio dynamic zone (RDZ) like outdoor environment, from a 4G LTE eNB that we configure to operate at 3.51 GHz. Using the raw I/Q samples, and using Matlab's LTE Toolbox, we provide a step-by-step description for frequency offset estimation/correction, synchronization, cell search, channel estimation, and reference signal received power (RSRP). We provide various representative results for each step, such as RSRP measurements and corresponding analytical approximation at different UAV altitudes, coherence bandwidth and coherence time of the channel at different UAV altitudes and link distances, and kriging based 3D RSRP interpolation. The collected raw data as well as the software developed for obtaining and post-processing such data are provided publicly for potential use by other researchers. AERIQ is also available in emulation and testbed environments for external researchers to access and use as part of the NSF AERPAW platform at NC State University.}, journal={2023 IEEE AEROSPACE CONFERENCE}, author={Maeng, S. J. and Ozdemir, O. and Guvenc, I. and Sichitiu, M. L. and Dutta, R. and Mushi, M.}, year={2023} }
 @article{maeng_park_guvenc_2023, title={Analysis of UAV Radar and Communication Network Coexistence With Different Multiple Access Protocols}, volume={71}, ISSN={["1558-0857"]}, url={https://doi.org/10.1109/TCOMM.2023.3305509}, DOI={10.1109/TCOMM.2023.3305509}, abstractNote={Unmanned aerial vehicles (UAVs) are expected to be used extensively in the future for various applications, either as user equipment (UEs) connected to a cellular wireless network, or as an infrastructure extension of an existing wireless network to serve other UEs. Next generation wireless networks will consider the use of UAVs for joint communication and radar and/or as dedicated radars for various sensing applications. Increasing number of UAVs will naturally result in larger number of communication and/or radar links that may cause interference to nearby networks, exacerbated further by the higher likelihood of line-of-sight signal propagation from UAVs even to distant receivers. With all these, it is critical to study network coexistence of UAV-mounted base stations (BSs) and radar transceivers. In this paper, using stochastic geometry, we derive closed-form expressions to characterize the performance of coexisting UAV radar and communication networks for spectrum overlay multiple access (SOMA) and time-division multiple access (TDMA). We evaluate successful ranging probability (SRP) and the transmission capacity (TC) and compare the performance of TDMA and SOMA. Our results show that SOMA can outperform TDMA on both SRP and TC when the node density of active UAV-radars is larger than the node density of UAV-comms.}, number={11}, journal={IEEE TRANSACTIONS ON COMMUNICATIONS}, author={Maeng, Sung Joon and Park, Jaehyun and Guvenc, Ismail}, year={2023}, month={Nov}, pages={6578–6592} }
 @article{maeng_chowdhury_guvenc_bhuyan_dai_2023, title={Base Station Antenna Uptilt Optimization for Cellular-Connected Drone Corridors}, volume={59}, ISSN={["1557-9603"]}, url={https://doi.org/10.1109/TAES.2023.3237994}, DOI={10.1109/TAES.2023.3237994}, abstractNote={Reliable wireless coverage in drone corridors is critical to enable a connected, safe, and secure airspace. To support beyond-visual-line-of-sight operations of aerial vehicles in a drone corridor, cellular base stations (BSs) can serve as a convenient infrastructure as they are widely deployed to provide seamless wireless coverage. However, antennas in the existing cellular networks are downtilted to optimally serve their ground users, which results in coverage holes at higher altitudes when they are used to serve drones. In this article, we consider the use of additional uptilted antennas at each cellular BS and optimize the uptilt angle to maximize the wireless coverage probability across a given drone corridor. Through numerical results, we characterize the optimal value of the antenna uptilt angle for a given antenna pattern as well as the minimum/maximum altitudes of the drone corridor.}, number={4}, journal={IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS}, author={Maeng, Sung Joon and Chowdhury, Md Moin Uddin and Guvenc, Ismail and Bhuyan, Arupjyoti and Dai, Huaiyu}, year={2023}, month={Aug}, pages={4729–4737} }
 @article{raouf_maeng_guvenc_ozdemir_sichitiu_2023, title={Cellular Spectrum Occupancy Probability in Urban and Rural Scenarios at Various UAS Altitudes}, ISSN={["2166-9570"]}, DOI={10.1109/PIMRC56721.2023.10293763}, abstractNote={The ever-growing demand for wireless connectivity, coupled with limited spectrum resources, has resulted in spectrum congestion and interference. This research investigates the probability of occupancy in common sub-6 GHz cellular network bands based on measurements conducted in urban and rural environments. Specifically, we analyze the spectrum occupancy of various long-term evolution (LTE), 5th generation (5G) and Citizens Broadband Radio Service (CBRS) bands used in the United States, considering both uplink and downlink transmissions at altitudes up to 180 meters. Additionally, we explore the influence of altitude on the probability of spectrum occupancy in these bands. Our findings reveal that the probability of occupancy is generally higher in the downlink compared to the uplink. Moreover, we observe that line-of-sight (LoS) signals play a critical role in higher altitudes. These results provide insights spectrum utilization in various cellular bands across different altitudes, with implications on interference and spectrum coexistence between terrestrial networks and unmanned aerial systems (UASs) in the future.}, journal={2023 IEEE 34TH ANNUAL INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, PIMRC}, author={Raouf, Amir Hossein Fahim and Maeng, Sung Joon and Guvenc, Ismail and Ozdemir, Ozgur and Sichitiu, Mihail}, year={2023} }
 @article{maeng_ozdemir_guvenc_sichitiu_mushi_dutta_2023, title={LTE I/Q Data Set for UAV Propagation Modeling, Communication, and Navigation Research}, volume={61}, ISSN={["1558-1896"]}, DOI={10.1109/MCOM.005.2200784}, abstractNote={Unmanned aerial vehicles (UAVs) have recently been gaining considerable attention due to their vast range of potential applications. To facilitate UAV use cases involving beyond visual line of sight (BVLOS), cellular networks have emerged as ground connectivity points, enabling remote control and payload communication for UAV links. However, the availability of limited datasets obstructs the study of cellular technology coverage for UAV flights at different altitudes and the development of machine learning (ML) techniques for improving UAV communication and navigation. In this article, we introduce raw LTE in-phase and quadrature (I/Q) sample data sets obtained from physical field experiments of the NSF AERPAW experimentation platform. A UAV equipped with a software-defined radio (SDR) was flown at altitudes ranging from 30 m to 110 m, collecting raw I/Q samples from an SDR-based LTE base station operating at 3.51 GHz. We have implemented a standardized metadata format that can be used to replicate the results obtained from the collected datasets. The post-processing of raw I/Q samples is described and representative results are provided. In the end, we give examples of potential uses of the provided dataset, post-processing sample code, and I/Q collection sample experiment code by other ML, wireless, and UAV researchers.}, number={9}, journal={IEEE COMMUNICATIONS MAGAZINE}, author={Maeng, Sung Joon and Ozdemir, Ozgur and Guvenc, Ismail and Sichitiu, Mihail L. and Mushi, Magreth and Dutta, Rudra}, year={2023}, month={Sep}, pages={90–96} }
 @article{kwon_maeng_guvenc_2023, title={RF SSSL by an Autonomous UAV with Two-Ray Channel Model and Dipole Antenna Patterns}, ISSN={["2166-9570"]}, DOI={10.1109/PIMRC56721.2023.10294058}, abstractNote={Advancements in unmanned aerial vehicle (UAV) technology have led to their increased utilization in various commercial and military applications. One such application is signal source search and localization (SSSL) using UAVs, which offers significant benefits over traditional ground-based methods due to improved RF signal reception at higher altitudes and inherent autonomous 3D navigation capabilities. Nevertheless, practical considerations such as propagation models and antenna patterns are frequently neglected in simulation-based studies in the literature. In this work, we address these limitations by using a two-ray channel model and a dipole antenna pattern to develop a simulator that more closely represents real-world radio signal strength (RSS) observations at a UAV. We then examine and compare the performance of previously proposed linear least square (LLS) based localization techniques using UAVs for SSSL. Localization of radio frequency (RF) signal sources is assessed based on two main criteria: 1) achieving the highest possible accuracy and 2) localizing the target as quickly as possible with reasonable accuracy. Various mission types, such as those requiring precise localization like identifying hostile troops, and those demanding rapid localization like search and rescue operations during disasters, have been previously investigated. In this paper, the efficacy of the proposed localization approaches is examined based on these two main localization requirements through computer simulations.}, journal={2023 IEEE 34TH ANNUAL INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, PIMRC}, author={Kwon, Hyeokjun and Maeng, Sung Joon and Guvenc, Ismail}, year={2023} }
 @article{maeng_ozdemir_nandakumar_guvenc_sichitiu_dutta_mushi_2023, title={Spectrum Activity Monitoring and Analysis for Sub-6 GHz Bands Using a Helikite}, ISSN={["2155-2487"]}, DOI={10.1109/COMSNETS56262.2023.10041314}, abstractNote={In this paper, we report sub-6 GHz spectrum measurement results at multiple ground fixed nodes and a helikite flying at altitudes up to 500 feet. Measurements are carried out at the NSF AERPAW platform in Raleigh, NC. We first describe our measurement methodology using software defined radios (SDRs) and explain the details of the measurement environment. Subsequently, we analyze the impact of terrain, measurement altitude, measurement frequency, and the time of the day on spectrum measurements for various different sub-6 GHz bands. In particular, we present spectrum occupancy results from various different LTE bands first in a rural environment, and then in an urban campus environment. Results show that for both environments, measured power at a given spectrum band increases with altitude up to 500 feet. On the other hand, in the urban environment, an abrupt increase in the aggregate received power is observed in all considered bands as the helikite rises above the buildings, when compared with the more gradual increase of the received power in same bands for the rural environment.}, journal={2023 15TH INTERNATIONAL CONFERENCE ON COMMUNICATION SYSTEMS & NETWORKS, COMSNETS}, author={Maeng, S. J. and Ozdemir, O. and Nandakumar, H. N. and Guvenc, I. and Sichitiu, M. L. and Dutta, R. and Mushi, M.}, year={2023} }
 @article{raouf_maeng_guvenc_ozdemir_sichitiu_2023, title={Spectrum Monitoring and Analysis in Urban and Rural Environments at Different Altitudes}, ISSN={["2577-2465"]}, DOI={10.1109/VTC2023-Spring57618.2023.10200994}, abstractNote={Due to the scarcity of spectrum resources, the emergence of new technologies and ever-increasing number of wireless devices operating in the radio frequency spectrum lead to data congestion and interference. In this work, we study the effect of altitude on sub-6 GHz spectrum measurement results obtained at a Helikite flying over two distinct scenarios; i.e., urban and rural environments. Specifically, we aim at investigating the spectrum occupancy of various long-term evolution (LTE), 5th generation (5G) and citizens broadband radio service (CBRS) bands utilized in the United States for both uplink and downlink at altitudes up to 180 meters. Our results reveal that generally the mean value of the measured power increases as the altitude increases where the line-of-sight links with nearby base stations is more available. SigMF-compliant spectrum measurement datasets used in this paper covering all the bands between 100 MHz to 6 GHz are also provided.}, journal={2023 IEEE 97TH VEHICULAR TECHNOLOGY CONFERENCE, VTC2023-SPRING}, author={Raouf, Amir Hossein Fahim and Maeng, Sung Joon and Guvenc, Ismail and Ozdemir, Ozgur and Sichitiu, Mihail}, year={2023} }
 @article{maeng_anjinappa_guvenc_2022, title={Coverage Probability Analysis of Passive Reflectors in Indoor Environments}, volume={26}, ISSN={["1558-2558"]}, url={https://doi.org/10.1109/LCOMM.2022.3193810}, DOI={10.1109/LCOMM.2022.3193810}, abstractNote={Since millimeter wave (mmWave) and sub-terahertz bands are highly vulnerable to blockage and penetration loss effects, wireless coverage enhancement is one of the critical challenges in indoor mmWave deployments. In particular, when the line-of-sight (LoS) link is blocked, a strong non-LoS (NLoS) path can provide a stable link quality. One of the efficient ways to improve the NLoS link is the use of strategically placed passive reflectors. In this letter, we study the indoor coverage improvement by using a transparent passive reflector attached on a wall. We consider an indoor open-door scenario, where the LoS link is blocked by the walls for receivers inside the room, and the coverage can only be achieved via an NLoS link through a passive reflector. We analytically derive closed-form equations of the reflection visibility probability and the coverage probability. By simulation and analytical results, we show the coverage dependency on the location and size of the reflector.}, number={10}, journal={IEEE COMMUNICATIONS LETTERS}, author={Maeng, Sung Joon and Anjinappa, Chethan K. and Guvenc, Ismail}, year={2022}, month={Oct}, pages={2287–2291} }
 @article{maeng_guvenc_sichitiu_floyd_dutta_zajkowski_ozdemir_mushi_2022, title={National Radio Dynamic Zone Concept with Autonomous Aerial and Ground Spectrum Sensors}, ISSN={["2164-7038"]}, DOI={10.1109/ICCWORKSHOPS53468.2022.9814648}, abstractNote={National radio dynamic zone (NRDZs) are intended to be geographically bounded areas within which controlled experiments can be carried out while protecting the nearby licensed users of the spectrum. An NRDZ will facilitate research and development of new spectrum technologies, waveforms, and protocols, in typical outdoor operational environments of such technologies. In this paper, we introduce and describe an NRDZ concept that relies on a combination of autonomous aerial and ground sensor nodes for spectrum sensing and radio environment monitoring (REM). We elaborate on key characteristics and features of an NRDZ to enable advanced wireless experimentation while also coexisting with licensed users. Some preliminary results based on simulation and experimental evaluations are also provided on out-of-zone leakage monitoring and real-time REMs.}, journal={2022 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS WORKSHOPS (ICC WORKSHOPS)}, author={Maeng, S. J. and Guvenc, I and Sichitiu, M. L. and Floyd, B. and Dutta, R. and Zajkowski, T. and Ozdemir, O. and Mushi, M.}, year={2022}, pages={687–692} }
 @article{maeng_guvenc_sichitiu_ozdemir_2022, title={Out-of-Zone Signal Leakage Sensing in Radio Dynamic Zones}, ISSN={["1550-3607"]}, DOI={10.1109/ICC45855.2022.9838534}, abstractNote={Radio dynamic zones (RDZs) are geographically bounded areas where novel advanced wireless technologies can be developed, tested, and improved, without the concern of interfering to other incumbent radio technologies nearby the RDZ. In order to operate an RDZ, use of a real-time spectrum monitoring system carries critical importance. Such a monitoring system should detect out-of-zone (OoZ) signal leakage outside of the RDZ, and if the interference to nearby receivers is intolerable, the monitoring system should be capable of mitigating such interference. This can e.g. be achieved by stopping operations inside the RDZ or switching to other bands for RDZ operation. In this paper, we introduce a spectrum monitoring concept for OoZ signal leakage detection at RDZs, where sensor nodes (SNs) are installed at the boundary of an RDZ and monitor the power leakage from multiple transmitters within the RDZ. We propose a prediction algorithm that estimates the received interference at OoZ geographical locations outside of the RDZ, using the measurements obtained at sparsely located SNs at the RDZ boundary. Using computer simulations, we evaluate the performance of the proposed algorithm and study its sensitivity to SN deployment density.}, journal={IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC 2022)}, author={Maeng, Sung Joon and Guvenc, Ismail and Sichitiu, Mihail L. and Ozdemir, Ozgur}, year={2022}, pages={5579–5584} }
 @article{maeng_yapici_guvenc_bhuyan_dai_2022, title={Precoder Design for Physical-Layer Security and Authentication in Massive MIMO UAV Communications}, volume={71}, ISSN={["1939-9359"]}, url={https://doi.org/10.1109/TVT.2022.3141055}, DOI={10.1109/TVT.2022.3141055}, abstractNote={Supporting reliable and seamless wireless connectivity for unmanned aerial vehicles (UAVs) has recently become a critical requirement to enable various different use cases of UAVs. Due to their widespread deployment footprint, cellular networks can support beyond visual line of sight (BVLOS) communications for UAVs. In this paper, we consider cellular connected UAVs (C-UAVs) that are served by massive multiple-input-multiple-output (MIMO) links to extend coverage range, while also improving physical layer security and authentication. We consider Rician channel and propose a novel linear precoder design for transmitting data and artificial noise (AN). We derive the closed-form expression of the ergodic secrecy rate of C-UAVs for both conventional and proposed precoder designs. In addition, we obtain the optimal power splitting factor that divides the power between data and AN by asymptotic analysis. Then, we apply the proposed precoder design in the fingerprint embedding authentication framework, where the goal is to minimize the probability of detection of the authentication tag at an eavesdropper. In simulation results, we show the superiority of the proposed precoder in both secrecy rate and the authentication probability considering moderate and large number of antenna massive MIMO scenarios.}, number={3}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Maeng, Sung Joon and Yapici, Yavuz and Guvenc, Ismail and Bhuyan, Arupjyoti and Dai, Huaiyu}, year={2022}, month={Mar}, pages={2949–2964} }
 @article{maeng_deshmukh_guvenc_bhuyan_dai_2021, title={Interference Analysis and Mitigation for Aerial IoT Considering 3D Antenna Patterns}, volume={70}, ISSN={["1939-9359"]}, url={https://doi.org/10.1109/TVT.2020.3046121}, DOI={10.1109/TVT.2020.3046121}, abstractNote={Due to dense deployments of Internet of things (IoT) networks, interference management becomes a critical challenge. With the proliferation of aerial IoT devices, such as unmanned aerial vehicles (UAVs), interference characteristics in 3D environments will be different than those in the existing terrestrial IoT networks. In this paper, we consider 3D topology IoT networks with a mixture of aerial and terrestrial links, with low-cost cross-dipole antennas at ground nodes and both omni-directional and cross-dipole antennas at aerial nodes. Considering a massive-access communication scenario, we first derive the statistics of the channel gain at IoT receivers in closed form while taking into account the radiation patterns of both ground and aerial nodes. These are then used to calculate the ergodic achievable rate as a function of the height of the aerial receiver and the cumulative interference. We propose a low-complexity interference mitigation scheme that utilizes 3D antenna radiation pattern with different dipole antenna settings. Our results show that using the proposed scheme, the ergodic achievable rate improves as the height of the aerial receivers increases. In addition, we also show that the ratio between the ground and aerial receivers that maximizes the peak rate increases with the height of the aerial IoT receiver.}, number={1}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Maeng, Sung Joon and Deshmukh, Mrugen A. and Guvenc, Ismail and Bhuyan, Arupjyoti and Dai, Huaiyu}, year={2021}, month={Jan}, pages={490–503} }
 @article{maeng_yapici_guvenc_dai_bhuyan_2021, title={Power Allocation for Fingerprint-Based PHY-Layer Authentication with mmWave UAV Networks}, ISSN={["1550-3607"]}, DOI={10.1109/ICC42927.2021.9500273}, abstractNote={Physical layer security (PLS) techniques can help to protect wireless networks from eavesdropper attacks. In this paper, we consider the authentication technique that uses fingerprint embedding to defend 5G cellular networks with unmanned aerial vehicle (UAV) systems from eavesdroppers and intruders. Since the millimeter wave (mmWave) cellular networks use narrow and directional beams, PLS can take further advantage of the 3D spatial dimension for improving the authentication of UAV users. Considering a multi-user mmWave cellular network, we propose a power allocation technique that jointly takes into account splitting of the transmit power between the precoder and the authentication tag, which manages both the secrecy as well as the achievable rate. Our results show that we can obtain optimal achievable rate with expected secrecy.}, journal={IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC 2021)}, author={Maeng, Sung Joon and Yapici, Yavuz and Guvenc, Ismail and Dai, Huaiyu and Bhuyan, Arupjyoti}, year={2021} }
 @article{bhuyan_guvenc_dai_sichitiu_singh_rahmati_maeng_2021, title={Secure 5G Network for a Nationwide Drone Corridor}, ISSN={["1095-323X"]}, DOI={10.1109/AERO50100.2021.9438162}, abstractNote={5G can provide the multiplicative capacity gains needed to support a large number of drones/UAS (Unmanned Aircraft Systems). 5G cellular networks with newly available millimeter wave (mmWave) frequency bands can provide wireless communication links for control as well as data traffic for drones and drone swarms. Drones are becoming increasingly important for commercial uses such as delivery and transportation as well as for public safety search and rescue of natural disaster victims, surveillance of remote critical infrastructure, surveys of environmental quality in protected regions, and detection of threats during major public events. This paper presents research findings in the following areas critical to validating the effectiveness of providing required 5G access to the drones with security, reliability, and spectral efficiency: 1) Radio coverage for the drone corridor by adding a separate set of antennas for coverage in the air while the conventional set of antennas continues to provide coverage on the ground. Beam transmission and validation with ray-tracing simulations are covered. 2) Optimization of uplink communication from a swarm of drones with a single mmWave beam by grouping the drones with power allocations for non-orthogonal multiple access (NOMA). 3) Optimization of the network lifetime of a swarm of drones resulting in suitable trajectories in the presence of interference. 4) Methods including precoding that can enhance physical layer security with channel information about the interference source. The paper concludes with plans for future research to provide further scientific basis for the proposed cellular drone network.}, journal={2021 IEEE AEROSPACE CONFERENCE (AEROCONF 2021)}, author={Bhuyan, Arupjyoti and Guvenc, Ismail and Dai, Huaiyu and Sichitiu, Mihail L. and Singh, Simran and Rahmati, Ali and Maeng, Sung Joon}, year={2021} }