@inproceedings{Kandukuri2021, title = {Software-defined Transmit Array Radio Platform for 5G Wireless Communications}, author = {Somasekhar Kandukuri and Jean-Baptiste Dor\'{e} and David Demmer and Benoit Miscopein }, year = {2021}, date = {2021-11-03}, urldate = {2021-11-03}, booktitle = {IEEE International Conference on Communications 2022, ICC22 }, keywords = {}, pubstate = {forthcoming}, tppubtype = {inproceedings} } @inproceedings{Chung2021b, title = {Demonstration of service continuity based on multi-connectivity with cellular and satellite access networks}, author = {Heesang Chung and Junhyeong Kim and Gosan Noh and Seok Ho Won and Taesang Choi and Ilgyu Kim }, doi = {10.1109/ICTC52510.2021.9621102}, year = {2021}, date = {2021-10-24}, urldate = {2021-10-24}, booktitle = {2021 International Conference on Information and Communication Technology Convergence (ICTC)}, abstract = {Multi-connectivity (MC) with multi-RAT (Radio Access Technology) can be used to enhance data throughput and reliability of wireless communication systems. A Korea-EU joint research named 5G-ALLSTAR has been pursuing a variety of service scenarios with multi-connectivity, and service continuity is one of the most important ones to be proven. The multi-RAT in the 5G-ALLSTAR is comprised of a mmWave-based 5G cellular access network and a satellite access network. We integrated these systems into an MC testbed and validated it to prove the concept and the feasibility of the service continuity. Specifically, we focused on the demonstration of video streaming services which the service continuity can be clearly verified with. To aggregate the data traffic of each RAT, an IP layer traffic controller has been adopted. Testing with the integrated MC testbed showcased the concept of the service continuity successfully. }, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } @article{Priscoli2021, title = {Capacity-Constrained Wardrop Equilibria and Application to Multi-Connectivity in 5G Networks}, author = {Francesco Delli Priscoli and Alessandro Giuseppi and Antonio Pietrabissa }, doi = {10.1016/j.jfranklin.2021.09.025}, year = {2021}, date = {2021-10-03}, urldate = {2021-10-03}, journal = {Journal of the Franklin Institute}, volume = {358}, number = {17}, pages = {9364--9384}, abstract = {In this paper, a distributed, non-cooperative and dynamic load-balancing algorithm is proposed in the context of multi-commodity adversarial network equilibria with constrained providers’ capacities. The algorithm is proven to converge to a generalised Wardrop user-equilibrium, referred to as Beckmann equilibrium in the literature, in which, for each commodity, the latencies of the unsaturated providers are equalized. The algorithm is then used as a Multi-connectivity algorithm in the context of 5G heterogeneous networks, in which the user equipments are able to use different access networks simultaneously to increase the transmission capacity and/or to improve the transmission reliability. The proposed controller provides a solution for dynamic traffic steering by distributing the traffic load over the available heterogeneous access points, considered as capacity providers. Simulation results validate the approach. The developed network simulator is available as an open-source environment De Santis et al. (2020).}, keywords = {5G, multi-connectivity, wardrop equilibria}, pubstate = {published}, tppubtype = {article} } @inproceedings{Dor\'{e}2021b, title = {FPGA Implementation of a Wideband Multi-Gb/s 5G BF-OFDM Transceiver}, author = {Jean-Baptiste Dor\'{e} and Marc Laugeois and Nicolas Cassiau and Xavier Popon }, doi = {10.1109/EuCNC/6GSummit51104.2021.9482424}, year = {2021}, date = {2021-07-28}, urldate = {2021-07-28}, booktitle = {2021 Joint European Conference on Networks and Communications 6G Summit (EuCNC/6G Summit)}, pages = {502--507}, publisher = {IEEE}, abstract = {This paper describes a Field Programmable Gate Array (FPGA) implementation of a multi-Gb/s Block Filtered (BF) OFDM transceiver, fully 5G NR compatible. The main obstacles for such a work are (i) the support of multiple configurations and parameters, (ii) the high bandwidth w.r.t the board clock frequency and (iii) the intrinsic complexity of BF-OFDM. We prove that despite these barriers an hardware implementation of this waveform is possible, even with a bandwidth up to 400 MHz. We based our developments on the following pillars: smart layout of the basic modules, parallelization of dedicated functions design and ad hoc architecture. Measurements and complexity analysis demonstrate the high flexibility of BF-OFDM.}, keywords = {5G, BF-OFDM, FPGA, parallelization, wideband}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{nokey, title = {Hierarchical RL for Load Balancing and QoS Management in Multi-Access Networks}, author = {Antonio Ornatelli and Andrea Tortorelli and Alessandro Giuseppi and Francesco Delli Priscoli }, doi = {10.1109/MED51440.2021.9480246}, year = {2021}, date = {2021-07-15}, urldate = {2021-07-15}, booktitle = {2021 29th Mediterranean Conference on Control and Automation (MED) }, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{nokey, title = {A Distributed Reinforcement Learning approach for Power Control in Wireless Networks}, author = {Antonio Ornatelli and Andrea Tortorelli and Francesco Liberati }, doi = {10.1109/AIIoT52608.2021.9454208}, year = {2021}, date = {2021-06-21}, urldate = {2021-06-21}, booktitle = {2021 IEEE World AI IoT Congress (AIIoT)}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{nokey, title = {Iterative MPC for Energy Management and Load Balancing in 5G Heterogeneous Networks}, author = {Antonio Ornatelli and Andrea Tortorelli and Alessandro Giuseppi }, doi = {10.1109/UEMCON51285.2020.9298113}, year = {2020}, date = {2020-12-25}, urldate = {2020-12-25}, booktitle = {2020 11th IEEE Annual Ubiquitous Computing, Electronics \& Mobile Communication Conference (UEMCON) }, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{Giuseppi2020e, title = {Design and Simulation of the Multi-RAT Load-balancing Algorithms for 5G-ALLSTAR Systems}, author = {Alessandro Giuseppi and Syed Maaz Shahid and Emanuele De Santis and Seok Ho Won and Sungoh Kwon and Taesang Choi}, doi = {10.1109/ICTC49870.2020.9289485}, issn = {2162-1233}, year = {2020}, date = {2020-12-21}, booktitle = {2020 International Conference on Information and Communication Technology Convergence (ICTC)}, publisher = {IEEE}, abstract = {This paper introduces algorithms for the multi-RAT load balancing function to maximize QoE in terrestrial and satellite combined system developed in the 5G-ALLSTAR project. The pros and cons of the considered algorithms are described and the simulator is also described in the paper with the on-going performance evaluation processes.}, keywords = {5G, load-balancing, multi-connectivity, multi-RAT, Satellite-terrestrial communication}, pubstate = {published}, tppubtype = {inproceedings} } @article{Yeom2020, title = {Performance analysis of satellite and terrestrial spectrum-shared networks with directional antenna}, author = {Jeong Seon Yeom and Gosan Noh and Heesang Chung and Ilgyu Kim and Bang Chul Jung }, doi = {10.4218/etrij.2020-0185}, year = {2020}, date = {2020-11-16}, urldate = {2020-11-16}, journal = {ETRI Journal}, volume = {42}, number = {5}, pages = {712--720}, abstract = {Abstract Recently, to make the best use of limited and precious spectrum resources, spectrum sharing between satellite and cellular networks has received much interest. In this study, we mathematically analyze the success probability of a fixed (satellite) earth station (FES) based on a stochastic geometry framework. Both the FES and base stations (BSs) are assumed to be equipped with a directional antenna, and the location and the number of BSs are modeled based on the Poisson point process. Furthermore, an exclusion zone is considered, in which the BSs are prohibited from locating in a circular zone with a certain radius around the FES to protect it from severe interference from the cellular BSs. We validate the analytical results on the success probability of the cognitive satellite-terrestrial network with directional antennas by comparing it using extensive computer simulations and show the effect of the exclusion zone on the success probability at the FES. It is shown that the exclusion zone-based interference mitigation technique significantly improves the success probability as the exclusion zone increases.}, keywords = {cognitive satellite-terrestrial network, poisson point process, spectrum sharing, stochastic geometry, success probability}, pubstate = {published}, tppubtype = {article} } @article{Kim2020b, title = {Design of cellular, satellite, and integrated systems for 5G and beyond}, author = {Junhyeong Kim and Guido Casati and Nicolas Cassiau and Antonio Pietrabissa and Alessandro Giuseppi and Dong Yan and Emilio Calvanese Strinati and Marjorie Thary and Danping He and Ke Guan and Heesang Chung and Ilgyu Kim}, doi = {10.4218/etrij.2020-0156}, year = {2020}, date = {2020-11-16}, urldate = {2020-11-16}, journal = {ETRI Journal}, volume = {42}, number = {5}, pages = {669--685}, abstract = {5G AgiLe and fLexible integration of SaTellite And cellulaR (5G-ALLSTAR) is a Korea-Europe (KR-EU) collaborative project for developing multi-connectivity (MC) technologies that integrate cellular and satellite networks to provide seamless, reliable, and ubiquitous broadband communication services and improve service continuity for 5G and beyond. The main scope of this project entails the prototype development of a millimeter-wave 5G New Radio (NR)-based cellular system, an investigation of the feasibility of an NR-based satellite system and its integration with cellular systems, and a study of spectrum sharing and interference management techniques for MC. This article reviews recent research activities and presents preliminary results and a plan for the proof of concept (PoC) of three representative use cases (UCs) and one joint KR-EU UC. The feasibility of each UC and superiority of the developed technologies will be validated with key performance indicators using corresponding PoC platforms. The final achievements of the project are expected to eventually contribute to the technical evolution of 5G, which will pave the road for next-generation communications.}, keywords = {5G-ALLSTAR, millimeter-wave, multi-connectivity, New Radio, satellite communications, vehicular communications}, pubstate = {published}, tppubtype = {article} } @article{Mukherjee2020, title = {A supervised-learning-based spatial performance prediction framework for heterogeneous communication networks}, author = {Shubhabrata Mukherjee and Taesang Choi and Md Tajul Islam and Baek-Young Choi and Cory Beard and Seuck Ho Won and Sejun Song}, doi = {10.4218/etrij.2020-0188}, year = {2020}, date = {2020-11-16}, urldate = {2020-11-16}, journal = {ETRI Journal}, volume = {42}, number = {5}, pages = {686-699}, abstract = {In this paper, we propose a supervised-learning-based spatial performance prediction (SLPP) framework for next-generation heterogeneous communication networks (HCNs). Adaptive asset placement, dynamic resource allocation, and load balancing are critical network functions in an HCN to ensure seamless network management and enhance service quality. Although many existing systems use measurement data to react to network performance changes, it is highly beneficial to perform accurate performance prediction for different systems to support various network functions. Recent advancements in complex statistical algorithms and computational efficiency have made machine-learning ubiquitous for accurate data-based prediction. A robust network performance prediction framework for optimizing performance and resource utilization through a linear discriminant analysis-based prediction approach has been proposed in this paper. Comparison results with different machine-learning techniques on real-world data demonstrate that SLPP provides superior accuracy and computational efficiency for both stationary and mobile user conditions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } @article{Strinati2020, title = {6G in the Sky: On-Demand Intelligence at the Edge of 3D Networks}, author = {Emilio Calvanese Strinati and Sergio Barbarossa and Taesang Choi and Antonio Pietrabissa and Alessandro Giuseppi and Emanuele {De Santis} and Josep Vidal and Zdenek Becvar and Thomas Haustein and Nicolas Cassiau and Francesca Costanzo and Junhyeong Kim and Ilgyu Kim}, doi = {10.4218/etrij.2020-0205}, year = {2020}, date = {2020-10-20}, urldate = {2020-10-20}, journal = {ETRI Journal}, volume = {42}, number = {5}, pages = {643--657}, abstract = {Sixth generation will exploit satellite, aerial, and terrestrial platforms jointly to improve radio access capability and unlock the support of on-demand edge cloud services in three-dimensional (3D) space, by incorporating mobile edge computing (MEC) functionalities on aerial platforms and low-orbit satellites. This will extend the MEC support to devices and network elements in the sky and forge a space-borne MEC, enabling intelligent, personalized, and distributed on-demand services. End users will experience the impression of being surrounded by a distributed computer, fulfilling their requests with apparently zero latency. In this paper, we consider an architecture that provides communication, computation, and caching (C3) services on demand, anytime, and everywhere in 3D space, integrating conventional ground (terrestrial) base stations and flying (non-terrestrial) nodes. Given the complexity of the overall network, the C3 resources and management of aerial devices need to be jointly orchestrated via artificial intelligence-based algorithms, exploiting virtualized network functions dynamically deployed in a distributed manner across terrestrial and non-terrestrial nodes.}, keywords = {3D connectivity, 3D networks, 3D services, 5G, 6G, B5G, high-altitude platform stations, mobile edge computing, non-terrestrial communications, satellite, unmanned aerial vehicle}, pubstate = {published}, tppubtype = {article} } @inproceedings{Jaeckel2020, title = {A 5G-NR Satellite Extension for the QuaDRiGa Channel Model}, author = {Stephan Jaeckel and Leszek Raschkowski and Lars Thiele}, url = {https://arxiv.org/abs/2010.01002}, year = {2020}, date = {2020-10-01}, urldate = {2020-10-01}, booktitle = {IEEE 93rd Vehicular Technology Conference: VTC2021-Spring}, abstract = {Low Earth orbit (LEO) satellite networks will become an integral part of the global telecommunication infrastructure. Modeling the radio-links of these networks and their interaction with existing terrestrial systems is crucial for the design, planning and scaling of these networks. The 3rd generation partnership project (3GPP) addressed this by providing guideline for such a radio-channel model. However, the proposed model lacks a satellite orbit model and has some inconsistencies in the provided parameters. This is addressed in this paper. We provide a non-geostationary-satellite model that can be integrated into geometry-based stochastic channel models (GSCMs) such as QuaDRiGa. We then use this model to obtain the GSCM parameters from a simplified environment model and compare the results to the 3GPP parameter-set. This solves the inconsistencies, but our simplified approach does not consider many propagation effects. Future work must therefore rely on measurements or accurate Ray-tracing models to obtain the parameters.}, keywords = {5G, channel model, QuaDRiGa, satellite}, pubstate = {forthcoming}, tppubtype = {inproceedings} } @inproceedings{Ornatelli2020b, title = {User-aware centralized resource allocation in heterogeneous networks}, author = {Antonio Ornatelli and Alessandro Giuseppi and Vincenzo Suraci and Andrea Tortorelli}, doi = {10.1109/MED48518.2020.9183080}, year = {2020}, date = {2020-09-01}, urldate = {2020-09-01}, booktitle = {2020 28th Mediterranean Conference on Control and Automation}, abstract = {In the last two years, in Europe, 5G networks and services proliferated. The integration of 5G networks with other radio access networks is considered one of the key enablers for matching the challenging 5G Quality of Service requirements. In particular, the integration with high throughput satellites promises to increase the network performances in terms of resilience and Quality of Service. The present work addresses this problem and presents a user-aware resource allocation methodology for heterogeneous networks. Said methodology is articulated in two-steps: at first, the Analytical Hierarchy Process is used for deciding the network over which traffic is steered and, then, a Cooperative Game for allocating resources within the network is set up. Simulations are presented for validating the proposed approach.}, keywords = {heterogeneous network, resource allocation}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{Giuseppi2020f, title = {Traffic steering and network selection in 5G networks based on Reinforcement Learning}, author = {Alessandro Giuseppi and Antonio Pietrabissa and Francesco Liberati and Roberto German\`{a} and Francesco Delli Priscoli}, doi = {10.23919/ECC51009.2020.9143837}, year = {2020}, date = {2020-07-20}, urldate = {2020-07-20}, booktitle = {European Control Conference 2020}, abstract = {This paper presents a controller for the problem of Network Selection in 5G Networks, based on Reinforcement Learning. The problem of Network Selection and Traffic Steering is modeled as a Markov Decision Process and a Q- Learning based control solution is designed to meet 5G requirements, such as Quality of Experience (QoE) maximization, Quality of Service (QoS) assurance and load balancing. Numerical simulations preliminarily validate the proposed approach on a simulated scenario considered in the European project H2020 5G-ALLSTAR.}, keywords = {5G, Network Selection, reinforcement learning, traffic steering}, pubstate = {published}, tppubtype = {inproceedings} } @article{Shahid2020, title = {Load Balancing for 5G Integrated Satellite-Terrestrial Networks}, author = {Syed Maaz Shahid and Yemane Teklay Seyoum and Seok Ho Won and Sungoh Kwon}, doi = {10.1109/ACCESS.2020.3010059}, issn = {2169-3536}, year = {2020}, date = {2020-07-17}, urldate = {2020-07-17}, journal = {IEEE Access}, volume = {8}, pages = {132144-132156}, abstract = {We propose a load balancing algorithm for a multi-RAT (radio access technology) network including a non-terrestrial network (NTN) and a terrestrial network (TN). Fifth generation (5G) and beyond-5G networks consider NTNs to provide connectivity and data delivery to large numbers of user equipments (UEs). However, previous load balancing algorithms do not consider the coexistence of NTNs and TNs and ignore the different resource allocation units in a multi-RAT network. Hence, we define a radio resource utilization ratio (RRUR) as a common load metric to measure the cell load of each RAT and employ an adaptive threshold to determine overloaded cells. The proposed algorithm consists of two steps to overcome the uneven load distribution across 5G cells: intra-RAT load balancing and inter-RAT load balancing. Based on the RRUR of a cell, the algorithm first performs intra-RAT load balancing by offloading the appropriate edge UEs of an overloaded cell to underutilized neighboring cells. If the RRUR of the cell is still higher than a predefined threshold, then inter-RAT load balancing is performed by offloading the delay-tolerant data flows of UEs to a satellite link. Furthermore, the algorithm estimates the impact of moving loads to the target cell load to avoid unnecessary load balancing actions. Simulation results show that the proposed algorithm not only distributes the load across terrestrial cells more evenly but also increases network throughput and the number of quality of service satisfied UEs more than previous load balancing algorithms.}, keywords = {}, pubstate = {published}, tppubtype = {article} } @article{Giuseppi2020, title = {Chance-Constrained Control With Lexicographic Deep Reinforcement Learning}, author = {Alessandro Giuseppi and Antonio Pietrabissa}, doi = {10.1109/lcsys.2020.2979635}, year = {2020}, date = {2020-07-01}, urldate = {2020-07-01}, journal = {IEEE Control Systems Letters}, volume = {4}, number = {3}, pages = {755--760}, publisher = {Institute of Electrical and Electronics Engineers (IEEE)}, abstract = {This letter proposes a lexicographic Deep Reinforcement Learning (DeepRL)-based approach to chance-constrained Markov Decision Processes, in which the controller seeks to ensure that the probability of satisfying the constraint is above a given threshold. Standard DeepRL approaches require i) the constraints to be included as additional weighted terms in the cost function, in a multi-objective fashion, and ii) the tuning of the introduced weights during the training phase of the Deep Neural Network (DNN) according to the probability thresholds. The proposed approach, instead, requires to separately train one constraint-free DNN and one DNN associated to each constraint and then, at each time-step, to select which DNN to use depending on the system observed state. The presented solution does not require any hyper-parameter tuning besides the standard DNN ones, even if the probability thresholds changes. A lexicographic version of the well-known DeepRL algorithm DQN is also proposed and validated via simulations.}, keywords = {constrained control, deep reinforcement learning, Markov decision processes}, pubstate = {published}, tppubtype = {article} } @inproceedings{Ma2020a, title = {Characterization for High-Speed Railway Channel enabling Smart Rail Mobility at 22.6 GHz}, author = {Lei Ma and Ke Guan and Dong Yan and Danping He and Bo Ai and Junhyeong Kim and Heesang Chung}, doi = {10.1109/WCNC45663.2020.9120474}, issn = {1558-2612}, year = {2020}, date = {2020-05-01}, urldate = {2020-05-01}, booktitle = {2020 IEEE Wireless Communications and Networking Conference (WCNC)}, pages = {1-6}, abstract = {The millimeter wave (mmWave) communication with large bandwidth is a key enabler for both the fifth-generation mobile communication system (5G) and smart rail mobility. Thus, in order to provide realistic channel fundamental, the wireless channel at 22.6 GHz is characterized for a typical high-speed railway (HSR) environment in this paper. After importing the three-dimensional environment model of a typical HSR scenario into a self-developed high-performance cloud-computing Ray-Tracing platform \textendash CloudRT, extensive raytracing simulations are realized. Based on the results, the HSR channel characteristics are extracted and analyzed, considering the extra loss of various weather conditions. The results of this paper can help for the design and evaluation for the HSR communication systems enabling smart rail mobility.}, keywords = {5G, High-speed railway, mmWave, radio propagation, ray-tracing, smart rail mobility}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{Kim2020, title = {5G-ALLSTAR: An Integrated Satellite-Cellular System for 5G and Beyond}, author = {Junhyeong Kim and Guido Casati and Antonio Pietrabissa and Alessandro Giuseppi and Emilio Calvanese Strinati and Nicolas Cassiau and Gosan Noh and Heesang Chung and Ilgyu Kim and Marjorie Thary and Jean-Michel Houssin and Federico Pigni and Sylvain Colombero and Pierre Dal Zotto and Leszek Raschkowski and Stephan Jaeckel}, doi = {10.1109/WCNCW48565.2020.9124751}, year = {2020}, date = {2020-04-01}, urldate = {2020-04-01}, booktitle = {2020 IEEE Wireless Communications and Networking Conference Workshops (WCNCW)}, pages = {1-6}, abstract = {This paper provides an overview of recent research activities of the 5G AgiLe and fLexible integration of SaTellite And cellulaR (5G-ALLSTAR) project which aims to develop Multi-Connectivity technology that integrates the cellular and satellite networks to provide seamless, reliable and ubiquitous broadband services. 5G-ALLSTAR also entails developing millimeter-wave (mmWave) 5G New Radio (NR)-based cellular access system and investigating the feasibility of NR-based satellite access for providing broadband and reliable 5G services. In addition, spectrum sharing between cellular and satellite networks is studied. With all the technologies developed, 5G-ALLSTAR will showcase the first fully integrated satellite and cellular prototype system for 5G and beyond 5G (B5G) services at a big event (e.g., sporting event like Roland-Garros) in 2021. This paper also provides a preliminary techno-economic analysis on potential use cases targeting vertical markets, and introduces recent standardization activities of relevance.}, keywords = {5G-ALLSTAR, millimeter wave, multi-connectivity, New Radio, satellite, vehicular communications}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{Giuseppi2020b, title = {Network Selection in 5G Networks Based on Markov Games and Friend-or-Foe Reinforcement Learning}, author = {Alessandro Giuseppi and Emanuele De Santis and Francesco Delli Priscoli and Seok Ho Won and Taesang Choi and Antonio Pietrabissa}, doi = {10.1109/WCNCW48565.2020.9124723}, year = {2020}, date = {2020-04-01}, urldate = {2020-04-01}, booktitle = {2020 IEEE Wireless Communications and Networking Conference Workshops (WCNCW)}, pages = {1-5}, abstract = {This paper presents a control solution for the optimal network selection problem in 5G heterogeneous networks. The control logic proposed is based on multi-agent Friend-or-Foe Q-Learning, allowing the design of a distributed control architecture that sees the various access points compete for the allocation of the connection requests. Numerical simulations validate conceptually the approach, developed in the scope of the EU-Korea project 5G-ALLSTAR}, keywords = {5G, Markov Games, Multi-Agent Reinforcement Learning, Network Selection}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{Wu2020, title = {Millimeter-Wave Channel Characterization for Vehicle-to-Infrastructure Communication}, author = {Lina Wu and Danping He and Ke Guan and Bo Ai and Junhyeong Kim and Heesang Chung}, doi = {10.23919/EuCAP48036.2020.9136022}, year = {2020}, date = {2020-03-01}, urldate = {2020-03-01}, booktitle = {2020 14th European Conference on Antennas and Propagation (EuCAP)}, pages = {1-5}, abstract = {The vehicle-to-infrastructure (V2I) communication can capture infrastructure data and provide travelers with real-time traffic information, which can significantly improve road safety. Millimeter-wave (mmWave) with large bandwidth has been introduced as a key technology to achieve ultra-reliable, low latency, and high-data-rate V2I communication. In this paper, the V2I communication in mmWave band (22.1GHz-23.lGHz) is characterized for typical urban and highway scenarios. By considering the different deployments involving overtaking and traffic flow, the simulations are conducted by employing the self-developed ray-tracing. The key channel parameters, including received power, Rician K-factor, root-mean-square delay spread and angular spreads, are analyzed and compared between different deployments. Moreover, the impacts of the multiple antennas and beam switching technologies at the vehicle are evaluated as well. This work aims to help the researchers understand the channel characteristics of the V2I communication in mmWave band and support communication system design for vehicular communications.}, keywords = {mmWave, radio propagation, ray-tracing, V2I communication}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{cassiau:hal-02864733, title = {Satellite and terrestrial multi-connectivity for 5G: making spectrum sharing possible}, author = {Nicolas Cassiau and Gosan Noh and Stephan Jaeckel and Leszek Raschkowski and Jean-Michel Houssin and Laurent Combelles and Marjorie Thary and Junhyeong Kim and Jean-Baptiste Dor\'{e} and Marc Laugeois}, url = {https://hal.archives-ouvertes.fr/hal-02864733}, year = {2020}, date = {2020-01-01}, urldate = {2020-01-01}, booktitle = {IEEE Wireless Communications and Networking Conference (WCNC 2020)}, address = {Seoul, South Korea}, abstract = {This paper reports the first results of the 5G-ALLSTAR project [1] aiming at providing solutions and enablers for spectrum sharing in a 5G cellular and satellite multi-connectivity context. First, we present an exhaustive study of the frequency bands eligible for these systems in the short and medium term. A ray-tracing based and a geometry-based stochastic channel models developed in the project are then described. These models can be used to simulate systems involving terrestrial and non-terrestrial networks. We then describe three different ways investigated in the project for managing interference: signal processing (hardware implementation of a 5G New Radio compatible physical layer), beamforming (steering and switching beams in order to avoid the interference while preserving the spectral efficiency) and radio resource management (tool designed for joint optimization of satellite and terrestrial resource sharing).}, keywords = {5G, multi-connectivity, satellite, spectrum sharing}, pubstate = {published}, tppubtype = {inproceedings} } @article{Giuseppi2020a, title = {Wardrop Equilibrium in Discrete-Time Selfish Routing with Time-Varying Bounded Delays}, author = {Alessandro Giuseppi and Antonio Pietrabissa}, doi = {10.1109/tac.2020.2981906}, year = {2020}, date = {2020-01-01}, urldate = {2020-01-01}, journal = {IEEE Transactions on Automatic Control}, pages = {1--1}, publisher = {Institute of Electrical and Electronics Engineers (IEEE)}, abstract = {This paper presents a multi-commodity, discrete-time, distributed and non-cooperative routing algorithm, which is proved to converge to an equilibrium in the presence of heterogeneous, unknown, time-varying but bounded delays. Under mild assumptions on the latency functions which describe the cost associated to the network paths, two algorithms are proposed: the former assumes that each commodity relies only on measurements of the latencies associated to its own paths; the latter assumes that each commodity has (at least indirectly) access to the measures of the latencies of all the network paths. Both algorithms are proven to drive the system state to an invariant set which approximates and contains the Wardrop equilibrium, defined as a network state in which no traffic flow over the network paths can improve its routing unilaterally, with the latter achieving a better reconstruction of the Wardrop equilibrium. Numerical simulations show the effectiveness of the proposed approach.}, keywords = {LaSalle’s invariance principle, selfish routing, time-delay systems, Wardrop equilibrium}, pubstate = {published}, tppubtype = {article} } @article{Noh2020, title = {Outage Analysis for Terrestrial-Satellite Spectrum Sharing}, author = {Gosan Noh and Heesang Chung and Ilgyu Kim}, doi = {10.1109/LCOMM.2020.3006133}, issn = {1558-2558}, year = {2020}, date = {2020-01-01}, urldate = {2020-01-01}, journal = {IEEE Communications Letters}, pages = {1-1}, abstract = {This letter investigates the effect of the interference due to spectrum sharing between terrestrial and satellite systems. Based on a realistic coexistence model, we provide an exact closed-form outage probability expression of the satellite link in the presence of the terrestrial interference. We assume Nakagami fading both for terrestrial and satellite links, with an additional consideration for the shadowed Rician fading satellite link. Numerical results show that uncontrolled terrestrial interference can significantly degrade the outage performance of the satellite link. The obtained formulas are useful in predicting and preventing harmful interference when designing coexistence mechanisms for terrestrial and satellite systems.}, keywords = {5G, interference, outage analysis, satellite}, pubstate = {published}, tppubtype = {article} } @article{Yan2020, title = {Channel Characterization for Vehicle-to-Infrastructure Communications in Millimeter-Wave Band}, author = {Dong Yan and Ke Guan and Danping He and Bo Ai and Zan Li and Junhyeong Kim and Heesang Chung and Zhangdui Zhong}, doi = {10.1109/ACCESS.2020.2977208}, issn = {2169-3536}, year = {2020}, date = {2020-01-01}, urldate = {2020-01-01}, journal = {IEEE Access}, volume = {8}, pages = {42325-42341}, abstract = {In recent years, the intelligent transport system (ITS) has been developed rapidly because of global urbanization and industrialization, which is considered as the key enabling technology to improve road safety, traffic efficiency, and driving experience. To achieve these goals, vehicles need to be equipped with a large number of sensors to enable the generation and exchange of high-rate data streams. Recently, millimeter-wave (mmWave) technology has been introduced as a means of meeting such a high data rate requirement. In this paper, a comprehensive study on the channel characteristics for vehicle-to-infrastructure (V2I) link in mmWave band (22.1-23.1 GHz) for various road environments and deployment configurations is conducted. The self-developed ray-tracing (RT) simulator is employed with the calibrated electromagnetic (EM) parameters. The three-dimensional (3D) environment models are reconstructed from the OpenStreetMap (OSM). In the simulations, not only the vehicle user equipment (UE) moves, but also the other vehicles such as cars, delivery vans, and buses move around the vehicle UE. Moreover, the impacts of the receiver (Rx) multiple antennas and beam switching technologies at the vehicle UE are evaluated as well. The channel parameters of the V2I link in mmWave band, including received power, Rician $K$ -factor, root-mean-square delay spread, and angular spreads are explored in the target scenarios under different simulation deployments. This work aims to help the researchers understand the channel characteristics of the V2I links in mmWave band and support the link-level and system-level design for future vehicular communications.}, keywords = {5G, mmWave, radio propagation, ray-tracing, vehicle-to-infrastructure link}, pubstate = {published}, tppubtype = {article} } @article{Ma2020, title = {Satellite-Terrestrial Channel Characterization in High-Speed Railway Environment at 22.6 GHz}, author = {Lei Ma and Ke Guan and Dong Yan and Danping He and Nuno R Leonor and Bo Ai and Junhyeong Kim}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019RS006995}, doi = {10.1029/2019RS006995}, year = {2020}, date = {2020-01-01}, urldate = {2020-01-01}, journal = {Radio Science}, volume = {55}, number = {3}, abstract = {Abstract The integration of satellite and terrestrial communication systems plays a vital role in the fifth-generation mobile communication system (5G) for the ubiquitous coverage, reliable service, and flexible networking. Moreover, the millimeter wave (mmWave) communication with large bandwidth is a key enabler for 5G intelligent rail transportation. In this paper, the satellite-terrestrial channel at 22.6 GHz is characterized for a typical high-speed railway (HSR) environment. The three-dimensional model of the railway scenario is reconstructed and imported into the Cloud Ray-Tracing (CloudRT) simulation platform. Based on extensive ray-tracing simulations, the channel for the terrestrial HSR system and the satellite-terrestrial system with two weather conditions are characterized, and the interference between them are evaluated. The results of this paper can help for the design and evaluation for the satellite-terrestrial communication system enabling future intelligent rail transportation.}, keywords = {5G, mmWave, radio propagation, Railway communication, ray-tracing, satellite, Satellite-terrestrial communication}, pubstate = {published}, tppubtype = {article} } @inproceedings{Choi2020, title = {Management and Orchestration Architecture for Integrated Access of Satellite and Terrestrial in 5G}, author = {Taesang Choi and Seok Ho Won and Alessandro Giuseppi and Antonio Pietrabissa and Sungoh Kwon}, doi = {10.1109/ICOIN48656.2020.9016484}, issn = {1976-7684}, year = {2020}, date = {2020-01-01}, urldate = {2020-01-01}, booktitle = {2020 International Conference on Information Networking (ICOIN)}, pages = {40-45}, abstract = {Multi-RAT access network, or heterogeneous access network, is considered to be the key enabling technology to satisfy the 5G requirements, such as high data rate, ultra-low latency and reliability. To make efficient use of all the available network resources, various research activities on multi-connectivity have been proposed to simultaneously connect, steer, and orchestrate across multiple different radio access technologies. Standardization of the management and orchestration of multi-connectivity environment, however, has just been initiated, thus further research and development is required. This paper proposes a novel management and orchestration architecture for integrated access of satellite and terrestrial in 5G. It especially focuses on the traffic steering and load-balancing of heterogeneous multi-RAT access environment.}, keywords = {5G, Computer architecture, heterogeneous network, high data rate, integrated access, load-balancing, management and orchestration, management standardization, mobility management (mobile radio), multi-connectivity, multiple different radio access technologies, network resources, orchestration architecture, QoS/QoE management, Quality of experience, Quality of service, radio access networks, Rats, reliability, satellite, telecommunication traffic, traffic steering, ultra-low latency}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{Kim2019a, title = {A Study on Frequency Planning of MN System for 5G Vehicular Communications}, author = {Junhyeong Kim and Sung-Woo Choi and Gosan Noh and Heesang Chung and Ilgyu Kim}, doi = {10.1109/ICTC46691.2019.8939787}, issn = {2162-1233}, year = {2019}, date = {2019-10-01}, urldate = {2019-10-01}, booktitle = {2019 International Conference on Information and Communication Technology Convergence (ICTC)}, pages = {1442-1445}, abstract = {Recently in Korea, a research project has been launched to develop Moving Network (MN) system, which is a millimeter-wave (mmWave)-band vehicular communications system aiming to provide public transportation (e.g., city buses, express buses) with broadband mobile wireless backhaul (MWB). The MN system is designed to operate in Flexible Access Common Spectrum (FACS), which is the unlicensed band of 22-23.6 GHz that has been designated by the Korean government, thereby allowing onboard passengers to use Gigabit Wi-Fi for free. Although it is possible to utilize a very high bandwidth of 1.6 GHz in FACS, it is necessary to investigate the proper frequency planning (FP) for MN system that can effectively mitigate inter-cell interference (ICI) so as to optimize the system performance. For this reason, in this paper, we investigate three different FP strategies for MN system and conduct a simple performance evaluation. Simulation results show that as inter-site distance (ISD) gets closer, the reverse frequency reuse (R-FR)-based FP achieves better signal-to-interference-plus-noise ratio (SINR) and capacity performances than the other FPs.}, keywords = {5G, frequency planning, frequency reuse, Moving Network, vehicular communications}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{8891407, title = {A Spatially Consistent Geometric D2D Small-Scale Fading Model for Multiple Frequencies}, author = {Stephan Jaeckel and Leszek Raschkowski and Frank Burkhardt and Lars Thiele}, doi = {10.1109/VTCFall.2019.8891407}, issn = {2577-2465}, year = {2019}, date = {2019-09-01}, urldate = {2019-09-01}, booktitle = {2019 IEEE 90th Vehicular Technology Conference (VTC2019-Fall)}, pages = {1-5}, abstract = {The 3rd generation partnership project (3GPP) new radio (NR) channel model introduced spatial consistency and a correlation model for multiple frequencies. Future extensions of this model will incorporate mobility at both ends of the link. These features are essential for many emerging wireless technologies in the 5G era. However, the existing small-scale-fading (SSF) model does not integrate these features coherently. To solve this problem, we propose a new SSF model that seamlessly integrates with the remaining NR model and allows the simultaneous simulation of all three features. We demonstrate this integration by showing that the output of the new SSF model agrees well with large-scale fading (LSF) parameter distributions provided by 3GPP. This enables the simulation of new wireless technology proposals that were difficult to realize with existing geometry-based stochastic channel models (GSCMs).}, keywords = {channel model, D2D, spatial consistency}, pubstate = {published}, tppubtype = {inproceedings} } @article{8792135, title = {6G: The Next Frontier: From Holographic Messaging to Artificial Intelligence Using Subterahertz and Visible Light Communication}, author = {Emilio Calvanese Strinati and Sergio Barbarossa and Jose Luis Gonzalez-Jimenez and Dimitri Ktenas and Nicolas Cassiau and Luc Maret and Cedric Dehos}, doi = {10.1109/MVT.2019.2921162}, issn = {1556-6080}, year = {2019}, date = {2019-09-01}, urldate = {2019-09-01}, journal = {IEEE Vehicular Technology Magazine}, volume = {14}, number = {3}, pages = {42-50}, abstract = {With its ability to provide a single platform enabling a variety of services, such as enhanced mobile broadband communications, virtual reality, automated driving, and the Internet of Things, 5G represents a breakthrough in the design of communication networks. Nevertheless, considering the increasing requests for new services and predicting the development of new technologies within a decade, it is already possible to envision the need to move beyond 5G and design a new architecture incorporating innovative technologies to satisfy new needs at both the individual and societal levels.}, keywords = {6G, artificial intelligence, visible light communication}, pubstate = {published}, tppubtype = {article} } @inproceedings{8757021, title = {Millimeter-Wave Communications for Smart Rail Mobility: From Channel Modeling to Prototyping}, author = {Ke Guan and Danping He and Bo Ai and Bile Peng and Andrej Hrovat and Junhyeong Kim and Zhangdui Zhong and Thomas K\"{u}rner}, doi = {10.1109/ICCW.2019.8757021}, issn = {2474-9133}, year = {2019}, date = {2019-05-01}, urldate = {2019-05-01}, booktitle = {2019 IEEE International Conference on Communications Workshops (ICC Workshops)}, pages = {1-6}, abstract = {In this paper, we present an integration solution from channel modeling to prototyping, to realize millimeter-wave (mmWave) communications for smart rail mobility. In order to involve the railway features in the channel models, two mmWave channel models are established based on ray-tracing simulations in realistic railway scenarios. Moreover, the challenges raised by mmWave directional network under high mobility is overcome by our solutions concerning handover scheme, random access procedure, and beamforming strategies. By integrating these key enabling technologies, we prototype the mobile hotspot network (MHN) system which realizes 1.25 Gbps downlink data throughput in a subway line with the train speed of 80 km/h.}, keywords = {channel model, mmWave}, pubstate = {published}, tppubtype = {inproceedings} } @article{Kim2019, title = {A Comprehensive Study on mmWave-Based Mobile Hotspot Network System for High-Speed Train Communications}, author = {Junhyeong Kim and Mathis Schmieder and Michael Peter and Heesang Chung and Sung-Woo Choi and Ilgyu Kim and Youngnam Han}, doi = {10.1109/TVT.2018.2865700}, issn = {1939-9359}, year = {2019}, date = {2019-03-01}, urldate = {2019-03-01}, journal = {IEEE Transactions on Vehicular Technology}, volume = {68}, number = {3}, pages = {2087-2101}, abstract = {This paper presents a comprehensive study on millimeter-wave-based mobile hotspot network (MHN) system for high-speed train (HST) communications, including system design, field trial, channel modeling based on measurement campaign, simulation, and validation. First, an overview of the MHN system and the design of an MHN enhanced (MHN-E) system including physical layer specification and single frequency network are provided. Second, the overall design of prototypes for MHN conventional (MHN-C) and MHN-E systems is presented, and then the recent experimental results of a field trial conducted at Seoul subway line 8 with the MHN-C prototype and demonstrations with the MHN-E prototype are analyzed. Third, this paper presents a measurement campaign investigating channel characteristics of a rural HST environment and a QuaDRiGa-based channel model developed based on the parameters extracted from the measurement. Finally, a computer simulation is conducted to validate the performance of the MHN-E system at high mobility of up to 500 km/h under the QuaDRiGa channel model, which suggests a good methodology for the validation of HST communication systems at the highmobility since it is impractical to be tested by real testbeds as of now. The simulation results revealed that the MHN-E system is capable of providing a broadband mobile wireless backhaul with a peak data rate exceeding 5 Gb/s at a speed of 500 km/h.}, keywords = {high-speed train, mmWave, mobile hotspot}, pubstate = {published}, tppubtype = {article} } @inproceedings{Pham-Viet2019, title = {Current Development of Vector Tracking Loops for Stand-Alone GNSS Receivers in Urban Canyons}, author = {Hung Pham-Viet and Sungoh Kwon and Seok Ho Won}, url = {https://www.eiric.or.kr/literature/ser_view.php?SnxGubun=INKO\&mode=total\&searchCate=literature\&gu=INME011A9\&cmd=qryview\&SnxIndxNum=221111\&rownum=\&totalCnt=1\&rownum=1\&q1_t=Q3VycmVudCBEZXZlbG9wbWVudCBvZiBWZWN0b3IgVHJhY2tpbmcgTG9vcHMgZm9yIFN0YW5kLUFsb25lIEdOU1MgUmVjZWl2ZXJzIGluIFVyYmFuIENhbnlvbnM=\&listUrl=L3NlYXJjaC9yZXN1bHQucGhwP1NueEd1YnVuPUlOS08mbW9kZT10b3RhbCZzZWFyY2hDYXRlPWxpdGVyYXR1cmUmcTE9Q3VycmVudCUyMERldmVsb3BtZW50JTIwb2YlMjBWZWN0b3IlMjBUcmFja2luZyUyMExvb3BzJTIwZm9yJTIwU3RhbmQtQWxvbmUlMjBHTlNTJTIwUmVjZWl2ZXJzJTIwaW4lMjBVcmJhbiUyMENhbnlvbnM=\&q1=Current+Development+of+Vector+Tracking+Loops+for+Stand-Alone+GNSS+Receivers+in+Urban+Canyons}, year = {2019}, date = {2019-01-01}, urldate = {2019-01-01}, booktitle = {KICS Winter Conference 2019}, publisher = {KICS}, abstract = {Recently, with the development of signal processing methods the accuracy of global navigation satellite system (GNSS) services has been improved. However, in urban environment, since the main challenges are multipath, non-line-ofsight (NLOS), weak signals and low accessibility to satellite in the sky, the positioning is unreliable, inaccuracy, therefore, it decreases the potential for various positioning applications. Vector-based tracking has been applied in modern GNSS receivers as the perfect approach instead of conventional tracking. This paper reviews the literature regarding the performance of vector-based methods applied in GNSS receivers under harsh environments. Under a range of conditions, the vector tracking loops demonstrate their robustness against many error sources in GNSS applications. Moreover, the development as well as the application of different methods based on vector tracking loop also rises a promising for further researches. The goad of paper is to provide the state of art relating to vector tracking loop for future approaches in positioning in urban canyons.}, keywords = {GNSS, satellite, vector tracking loops}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{miscopein:cea-01986524, title = {Air Interface Challenges and Solutions for future 6G Networks}, author = {Benoit Miscopein and Jean-Baptiste Dor\'{e} and Emilio Calvanese Strinati and Dimitri Kt\'{e}nas and Sergio Barbarossa}, url = {https://hal-cea.archives-ouvertes.fr/cea-01986524}, year = {2019}, date = {2019-01-01}, urldate = {2019-01-01}, booktitle = {1st 6G Wireless Summit}, abstract = {5G networks are expected to be deployed in 2020 and are considered as a global game changer from a technological, economic, societal and environmental perspective with very aggressive performance levels in terms of latency, energy efficiency, wireless broadband capacity, elasticity, etc. Many experts say that the next big step for cellular networks is not 5G but its cloudification that will support the explosion of radically new services and applications ranging from immersive five-sense media to ambient sensing intelligence and a pervasive introduction of artificial intelligence. In our vision, the next generation of wireless systems will transform the 5G service-oriented networks into user and machine ad-hoc dynamic (re)configuration of network slices. This will be enabled by software-defined end-to-end solutions from the core to the radio access network, including the air interface as well as the RF and antenna systems which are envisioned as one of the keys to meet the user/service requirements. Users and machines will be indeed able to dynamically (re)configure network slices thanks to intelligent personal edges. This paper presents our perspective of the 6G air interface and raise the concept of software defined artificial intelligence and air interface (SD-AI 2) as a framework of 6G air interface. This concept is an extension of the one initially proposed for 5G [1]. Instead of a global optimized air interface, we envisage to bring agility and flexibility to air interface with the help of artificial intelligence and learning techniques to improve efficiency. The paper describes the proposed context and highlights the technical challenges at different levels.}, keywords = {6G, air interface, artificial intelligence, beyond 5G, mobile edge cloud}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{Lisi2019, title = {Multi-Connectivity in 5G terrestrial-Satellite Networks: the 5G-ALLSTAR Solution}, author = {Federico Lisi and Giacinto Losquadro and Andrea Tortorelli and Antonio Ornatelli and Manuel Donsante}, url = {https://arxiv.org/abs/2004.00368 http://proceedings.kaconf.org/papers/2019/ka17_2.pdf}, year = {2019}, date = {2019-01-01}, urldate = {2019-01-01}, booktitle = {Ka and Broadband Communications, Navigation and Earth Observation Conference}, journal = {arXiv preprint arXiv:2004.00368}, abstract = {The 5G-ALLSTAR project is aimed at integrating Terrestrial and Satellite Networks for satisfying the highly challenging and demanding requirements of the 5G use cases. The integration of the two networks is a key feature to assure the service continuity in challenging communication situations (e.g., emergency cases, marine, railway, etc.) by avoiding service interruptions. The 5G-ALLSTAR project proposes to develop Multi-Connectivity (MC) solutions in order to guarantee network reliability and improve the throughput and latency for each connection between User Equipment (UE) and network. In the 5G-ALLSTAR vision, we divide the gNB in two entities: 1) gNB-CU (Centralized Unit) and 2) gNB-DU (Distributed Unit) The gNB-CU integrates an innovative Traffic Flow Control algorithm able to optimize the network resources by coordinating the controlled gNB-DUs resources, while implementing MC solutions. The MC permits to connect each UE with simultaneous multiple access points (even different radio access technologies). This solution leads to have independent gNB-DU/s that contain the RLC, MAC and PHY layers. The 5G-ALLSTAR MC algorithms offer advanced functionalities to RRC layer (in the gNB-CU) that is, in turn, able to set up the SDAP, the PDCP and the lower layers in gNB-DU. In this regard, the AI-based MC algorithms, implemented in gNB-CU, by considering the network performances in the UE surrounding environment as well as the UE QoS requirements, will dynamically select the most promising access points able to guarantee the fulfilment of the requirements also enabling the optimal traffic splitting to cope with the connection reliability. In this paper, we present also an innovative AI-based framework, included within the Traffic Flow Control, able to address the MC objectives, by implementing a Reinforcement Learning algorithm in charge of solving the network control problem.}, keywords = {5G, multi-connectivity, satellite}, pubstate = {published}, tppubtype = {inproceedings} } @article{Yi2019, title = {Characterization for the Vehicle-to-Infrastructure Channel in Urban and Highway Scenarios at the Terahertz Band}, author = {Haofan Yi and Ke Guan and Danping He and Bo Ai and Jianwu Dou and Junhyeong Kim}, doi = {10.1109/ACCESS.2019.2953890}, issn = {2169-3536}, year = {2019}, date = {2019-01-01}, urldate = {2019-01-01}, journal = {IEEE Access}, volume = {7}, pages = {166984-166996}, abstract = {With the challenge to form the networks of the Intelligent Transportation Systems (ITS), both technologies of vehicles and wireless communication are required to be connected tightly. In terms of wireless communication, the communication system in the terahertz (THz) frequency range with ultra-large bandwidth is a potential technology to support very high-data-rate wireless transmission at the age of beyond fifth-generation mobile communications (B5G). In this paper, the carrier frequency of 300 GHz with 8 GHz bandwidth vehicle-to-infrastructure (V2I) channel is characterized for the urban and highway scenario, respectively. The self-developed ray-tracing (RT) simulator is employed with the calibrated electromagnetic (EM) parameters. Since the wavelength of carrier frequency approaches the diameters of raindrops and snowflakes, the significant influence of the precipitation on the channel characterization is studied in our work as well. The large-scale parameters of the THz V2I channel, including path loss, Rician K-factor, root-mean-square (RMS) delay spread, and angular spreads are explored in the target scenarios under sunny, rainy, and snowy conditions, respectively. The channel characteristics studied in this paper can be used to support the link-level and system-level design for the future THz vehicular communications.}, keywords = {Channel characteristics, radio propagation, ray-tracing, terahertz communication, vehicle-toinfrastructure channel}, pubstate = {published}, tppubtype = {article} } @article{Kim2019b, title = {Efficient Groupcast Schemes for Vehicle Platooning in V2V Network}, author = {Junhyeong Kim and Youngnam Han and Ilgyu Kim}, doi = {10.1109/ACCESS.2019.2955791}, issn = {2169-3536}, year = {2019}, date = {2019-01-01}, urldate = {2019-01-01}, journal = {IEEE Access}, volume = {7}, pages = {171333-171345}, abstract = {Recently, groupcast has taken a lot of attention for vehicle platooning in vehicle-to-vehicle (V2V) network. In general, a traditional groupcast scheme by retransmission where source vehicle user equipment (S-VE) repeatedly transmits the same packet to destination VEs (D-VEs) is implemented in two ways; repetitive transmission for a predetermined number of times without receiving hybrid automatic repeat request (HARQ)-ACK/NACK from the D-VEs, and retransmission based on the HARQ-ACK/NACK. Although the former scheme is very easy to implement, it may lead to inefficient resource utilization due to excessive retransmissions. For the latter, the same problem arises when link quality between S-VE and D-VE is constantly poor. Hence, in this paper, we first investigate a heuristic scheme that can yield the superior performance of groupcast success rate with low computational complexity. Then, a groupcast scheme with the joint control of retransmission VE (R-VE) selection and time domain resource allocation is investigated by formulating a Markov decision process (MDP). The goal of the second proposed scheme is to find an optimal joint strategy for R-VE selection and time domain resource allocation that can minimize total time consumption while satisfying desired performance in terms of groupcast success rate. Simulation results validate that the proposed schemes significantly improve the groupcast success rate and the efficiency of time domain resource utilization, and greatly reduce the completion time of groupcast as compared with the two traditional groupcast schemes.}, keywords = {groupcast, MDP, V2V communications, vehicle platooning}, pubstate = {published}, tppubtype = {article} } @article{Yan2019, title = {Channel Characterization for Satellite Link and Terrestrial Link of Vehicular Communication in the mmWave Band}, author = {Dong Yan and Haofan Yi and Danping He and Ke Guan and Bo Ai and Zhangdui Zhong and Junhyeong Kim and Heesang Chung}, doi = {10.1109/ACCESS.2019.2956821}, issn = {2169-3536}, year = {2019}, date = {2019-01-01}, urldate = {2019-01-01}, journal = {IEEE Access}, volume = {7}, pages = {173559-173570}, abstract = {In the vision of intelligent transportation, vehicles are expected to feature with advanced applications, such as automatic road enforcement, dynamic traffic light sequence, and autonomous driving. Therefore, real-time and fast dynamic information exchanges are required, and vehicle-to-everything (V2X) communications are highly demanded. In this work, the channel characteristics of vehicular communication are analyzed in the millimeter-wave (mmWave) band at 22.1-23.1 GHz. Specifically, two types of links (the satellite link and the terrestrial link) are considered in urban and highway scenarios with different weather conditions. The ray-tracing simulator together with calibrated electromagnetic parameters is employed to practically generate wideband channels. The key channel parameters of each link including the received power, Rician K -factor, root-mean-square delay spread, and angular spreads are explored. The co-channel interferences between the two links are analyzed as well. The observations and conclusions of this work can be useful for the design of V2X communication technologies.}, keywords = {5G, mmWave, radio propagation, ray-tracing, satellite, vehicular communications}, pubstate = {published}, tppubtype = {article} } @inproceedings{8644076, title = {Realistic Channel Characterization for 5G Millimeter-Wave Railway Communications}, author = {Ke Guan and Danping He and Bo Ai and Andrej Hrovatz and Junhyeong Kim and Zhangdui Zhong and Thomas K\"{u}rner}, doi = {10.1109/GLOCOMW.2018.8644076}, year = {2018}, date = {2018-12-01}, urldate = {2018-12-01}, booktitle = {2018 IEEE Globecom Workshops (GC Wkshps)}, pages = {1-6}, abstract = {In this paper, we characterize the channel for fifth-generation (5G) millimeter-wave (mmWave) railway communications. In order to involve the railway features in the channel models, we realize extensive ray-tracing simulations in the 60 GHz band with 8 GHz bandwidth in realistic mmWave railway scenarios. The four angular spreads - azimuth angular spread of arrival (ASA) and departure (ASD), elevation angular spread of arrival (ESA) and departure (ESD) - are extracted and analyzed in detail. This angular domain information together with our previous work on path loss exponent, shadow factor, Ricean K-factor, and root-mean-square (RMS) delay spread, characterize the 5G mmWave railway channel comprehensively. The two parameter tables can be input into the standard channel models.}, keywords = {mmWave}, pubstate = {published}, tppubtype = {inproceedings} } @inproceedings{8566834, title = {Channel Characteristics in Rural Railway Environment at 28 GHz}, author = {Longhe Wang and Bo Ai and Ke Guan and Danping He and Zhangdui Zhong and Junhyeong Kim}, doi = {10.1109/ITST.2018.8566834}, year = {2018}, date = {2018-10-01}, urldate = {2018-10-01}, booktitle = {2018 16th International Conference on Intelligent Transportation Systems Telecommunications (ITST)}, pages = {1-5}, abstract = {Nowadays, rail traffic is expected to evolve into a new era of "smart rail mobility", where trains, infrastructure, travelers and goods will be increasingly interconnected. Railway communications are required to support various high-data-rate applications, the communication system should be carefully designed, which makes railway scenario becomes an important communication scenario in the 5G era. Millimeter-wave (mmWave) bands and novel technologies like resource allocation, multiple access and multiple-output beam-forming are proposed in the realization of this goal. In this paper, the mmWave channel characteristics of rural railway scenario are studied via a calibrated ray-tracing simulator. The large-scale parameters of the channel characteristics, including the path loss, root-mean-square (RMS) delay spread, Rician K-factor, angular spreads, and cross-polarization ration (XPR) are explored. The statistical properties, decorrelation distance and cross-correlations are analyzed. The studied channel characteristics can be practically used to support the link level and system level design of the communication system in the similar environments.}, keywords = {mmWave}, pubstate = {published}, tppubtype = {inproceedings} }