Showing papers by "Chan-Byoung Chae published in 2021"

A Vision of an XR-Aided Teleoperation System toward 5G/B5G

Abstract: Extended reality (XR)-aided teleoperation has shown its potential in improving operating efficiency in mission-critical, information-rich, and complex scenarios. The multi-sensory XR devices introduce several new types of traffic with unique quality of service (QoS) requirements, which are usually defined by three measures: human perception, corresponding sensors, and present devices. To fulfill these requirements, cellular-sup-ported wireless connectivity can be a promising solution that can largely benefit robot-to-XR and XR-to-robot links. In this article, we present industrial and piloting use cases and identify the service bottleneck of each case. We then cover the QoS of robot-XR and XR-robot links by summarizing the sensors' parameters and processing procedures. To realize these use cases, we introduce potential solutions for each case with cellular connections. Finally, we build testbeds to investigate the effectiveness of supporting our proposed links using current wireless topologies.

Graph-Theory-Based Resource Allocation and Mode Selection in D2D Communication Systems: The Role of Full-Duplex

Abstract: We propose graph-theory-based mode selection and resource allocation algorithms for device-to-device (D2D) communication systems in which a full-duplex (FD) scheme can be applied. To apply FD in practice, the current half-duplex (HD) communication devices need to be upgraded to FD devices. Replacing all the devices at once, though, is undesirable; implementing FD incurs a high cost. It is prudent then to select the devices that ought to be changed first. This would ensure better performance at reducing frequency range or enhancing sum-rate. To resolve this issue, we suggest an algorithm that selects D2D pairs based on the centrality concept of graph theory. We also propose a resource allocation algorithm modified for FD-applied environments to reduce the range of frequency bands. Numerical analyses confirm that the proposed system achieves a reduction of the used frequency range as well as the theoretical maximum sum-rate performance.

Resource Allocation for Multiuser Molecular Communication Systems Oriented to the Internet of Medical Things

Abstract: Communication between nanomachines is still an important topic in the construction of the Internet of Bio-Nano Things (IoBNT). Currently, molecular communication (MC) is expected to be a promising technology to realize IoBNT. To effectively serve the IoBNT composed of multiple nanomachine clusters, it is imperative to study multiple-access MC. In this article, based on the molecular division multiple access technology, we propose a novel multiuser MC system, where information molecules with different diffusion coefficients are first employed. Aiming at the user fairness in the considered system, we investigate the optimization of molecular resource allocation, including the assignment of the types of molecules and the number of molecules of a type. Specifically, three performance metrics are considered, namely, min–max fairness for error probability, max–min fairness for achievable rate, and weighted sum-rate maximization. Moreover, we propose two assignment strategies for types of molecules, i.e., best-to-best (BTB) and best-to-worst (BTW). Subsequently, for a two-user scenario, we analytically derive the optimal allocation for the number of molecules when types of molecules are fixed for all users. In contrast, for a three-user scenario, we prove that the BTB and BTW schemes with the optimal allocation for the number of molecules can provide the lower and upper bounds on system performance, respectively. Finally, numerical results show that the combination of BTW and the optimal allocation for the number of molecules yields better performance than the benchmarks.

Molecular-Type Permutation Shift Keying in Molecular MIMO Communications for IoBNT

Abstract: Molecular communication (MC) is a bio-inspired communication paradigm, which lays the foundation for the Internet of Bio-NanoThings (IoBNT) in the medical field As a high energy-efficient information transfer method, MC via diffusion (MCvD) is envisioned as a promising candidate for IoBNT but suffers from low date rates due to the long tail of the channel impulse response (CIR) To this end, the multiple-input–multiple-output (MIMO) technique has been introduced to MCvD However, the intersymbol interference (ISI) and interlink interference (ILI) deteriorate the bit error rate (BER) performance of MIMO MCvD systems In this article, molecular type permutation shift keying in the space domain (MTPSK-SD) and time-interleaved MTPSK-SD are proposed for MIMO MCvD systems to improve the BER performance by reducing ILI The principle of MTPSK-SD is further generalized to the spatiotemporal domain, yielding three spatiotemporal modulation schemes, which can provide desirable BER performance without requiring any CIR information in the communication scenarios affected by different levels of ISI and ILI Two low-complexity detectors are proposed to obtain different tradeoffs between anti-ILI and anti-ISI performance Furthermore, a complementary coding scheme, which can effectively reduce the ILI under the considered symmetrical system topology, is designed and applied to all the proposed modulation schemes Additionally, the BER upper bound is analyzed Numerical simulations on BER corroborate the analysis and show that the proposed schemes are promising multimolecule modulation alternatives, which outperform the existing MIMO MCvD modulation schemes

MIMO Operations in Molecular Communications: Theory, Prototypes, and Open Challenges

Abstract: The Internet of Bio-nano Things is a significant development for next generation communication technologies. Because conventional wireless communication technologies face challenges in realizing new applications (e.g., in-body area networks for health monitoring) and necessitate the substitution of information carriers, researchers have shifted their interest to molecular communications (MC). Although remarkable progress has been made in this field over the last decade, advances have been far from acceptable for the achievement of its application objectives. A crucial problem of MC is the low data rate and high error rate inherent in particle dynamics specifications, in contrast to wave-based conventional communications. Therefore, it is important to investigate the resources by which MC can obtain additional information paths and provide strategies to exploit these resources. This study aims to examine techniques involving resource aggregation and exploitation to provide prospective directions for future progress in MC. In particular, we focus on state-of-the-art studies on multiple-input multiple-output (MIMO) systems. We discuss the possible advantages of applying MIMO to various MC system models. Furthermore, we survey various studies that aimed to achieve MIMO gains for the respective models, from theoretical background to prototypes. Finally, we conclude this study by summarizing the challenges that need to be addressed.

A Molecular Spatio-Temporal Modulation Scheme for MIMO Communications

Abstract: In molecular communication via diffusion (MCvD), information is conveyed by diffusing molecules. MCvD enjoys high energy efficiency but suffers from low date rates due to the long tail of the channel impulse response. To this end, the multiple-input multiple-output (MIMO) technique has been introduced to MCvD. However, the inter-symbol interference (ISI) and inter-link interference (ILI) deteriorate the bit error rate (BER) performance of MIMO MCvD systems. In this paper, a novel molecular modulation scheme, called molecular type permutation shift keying in the spatio-temporal domain, is proposed for MIMO MCvD systems to improve the BER performance by combating ILI and ISI. A low-complexity detector without requiring channel impulse response information is proposed. Furthermore, a complementary coding scheme that can effectively reduce ILI is designed. Additionally, the BER upper bound is analyzed. Numerical simulations on BER corroborate the analysis and show that the proposed scheme is a promising multi-molecule modulation alternative, which outperforms the existing MIMO MCvD modulation schemes.

Resource Allocation for Max-Min Rate Fairness in Molecular Communication Systems

Abstract: Molecular communication (MC) is considered to be a promising technology to realize the Internet of Nano Things (IoNT), especially the biomedical IoNT. In the construction of IoNT, communication between nano-machines is still an important topic, where multiple-access MC is imperative to be studied due to the multiple nano-machine clusters in IoNT. In this paper, a novel multi-user MC system based on the molecular division multiple access technology is proposed, where information molecules with different diffusion coefficients are first employed. Moreover, we employ the max-min rate fairness as a criterion to investigate the optimization of molecular resource allocation, including the assignment for types of molecules and the number of associated molecules. Two assignment strategies for types of molecules, i.e., best-to-best (BTB) and best-to-worst (BTW), are proposed. Subsequently, we analytically deduce the optimal allocation for the number of molecules when types of molecules are fixed for all users. Finally, numerical results show that the combination of BTW and the optimal allocation for the number of molecules exhibits the best performance.

An Energy-efficient Aerial Backhaul System with Reconfigurable Intelligent Surface.

Abstract: In this paper, we propose a novel wireless architecture, mounted on a high-altitude aerial platform, which is enabled by reconfigurable intelligent surface (RIS) By installing RIS on the aerial platform, rich line-of-sight and full-area coverage can be achieved, thereby, overcoming the limitations of the conventional terrestrial RIS We consider a scenario where a sudden increase in traffic in an urban area triggers authorities to rapidly deploy unmanned-aerial vehicle base stations (UAV- BSs) to serve the ground users In this scenario, since the direct backhaul link from the ground source can be blocked due to several obstacles from the urban area, we propose reflecting the backhaul signal using aerial-RIS so that it successfully reaches the UAV-BSs We jointly optimize the placement and array-partition strategies of aerial-RIS and the phases of RIS elements, which leads to an increase in energy-efficiency of every UAV-BS We show that the complexity of our algorithm can be bounded by the quadratic order, thus implying high computational efficiency We verify the performance of the proposed algorithm via extensive numerical evaluations and show that our method achieves an outstanding performance in terms of energy-efficiency compared to benchmark schemes

MIMO Operations in Molecular Communications: Theory, Prototypes, and Open Challenges

Abstract: The Internet of Bio-nano Things is a significant development for next generation communication technologies. Because conventional wireless communication technologies face challenges in realizing new applications (e.g., in-body area networks for health monitoring) and necessitate the substitution of information carriers, researchers have shifted their interest to molecular communications (MC). Although remarkable progress has been made in this field over the last decade, advances have been far from acceptable for the achievement of its application objectives. A crucial problem of MC is the low data rate and high error rate inherent in particle dynamics specifications, in contrast to wave-based conventional communications. Therefore, it is important to investigate the resources by which MC can obtain additional information paths and provide strategies to exploit these resources. This study aims to examine techniques involving resource aggregation and exploitation to provide prospective directions for future progress in MC. In particular, we focus on state-of-the-art studies on multiple-input multiple-output (MIMO) systems. We discuss the possible advantages of applying MIMO to various MC system models. Furthermore, we survey various studies that aimed to achieve MIMO gains for the respective models, from theoretical background to prototypes. Finally, we conclude this study by summarizing the challenges that need to be addressed.

RF Lens Antenna Array-Based One-Shot Coarse Pointing for Hybrid RF/FSO Communications

Abstract: Because of its high directivity, free-space optical (FSO) communication offers a number of advantages. It can, however, give rise to major system difficulties concerning alignment between two terminals. During the link-acquisition step (a.k.a. coarse pointing), a ground station can be prevented from acquiring optical links due to pointing errors and insufficient information about unmanned aerial vehicle locations. We propose, in this letter, a radio-frequency (RF) lens antenna array to increase the performance of coarse pointing in hybrid RF/FSO communications. The proposed algorithm using a novel closed-form angle estimator, compared to conventional methods, reduces the minimum outage probability by over a thousand times.