• 인터넷정보학회논문지
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• 제24권1호
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• pp.17-26
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• 2023

A smart city is a massive internet of things (IoT) environment, where all terminal devices are connected to a network to create and share information. In accordance with massive IoT environments, millions of IoT devices are connected, and countless data are generated in real time. However, since heterogeneous IoT devices are used, collecting the logs for each IoT device is difficult. Due to these issues, when an IoT device is invaded or is engaged in malicious behavior, such as infection with malware, it is difficult to respond quickly, and additional damage may occur due to information leakage or stopping the IoT device. To solve this problem, in this paper, we propose identifying the attack technique used for initial access to IoT devices through MITRE ATT&CK, collect the logs that can be generated from the identified attack technique, and use them to identify the cause of malware infection.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권1호
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• pp.185-201
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• 2023

Grant-free random access (GFRA) can reduce the access delay and signaling cost, and satisfy the short transmission packet and strict delay constraints requirement in internet of things (IoT). IoT is a major trend in the future, which is characterized by the variety of applications and devices. However, most existing studies on GFRA only consider a single type of device and omit the effect of access delay. In this paper, we study GFRA in multicell massive multipleinput multiple-output (MIMO) systems where different types of devices with various configurations and requirements co-exist. By introducing the backoff mechanism, each device is randomly activated according to the backoff parameter, and active devices randomly select an orthogonal pilot sequence from a predefined pilot pool. An analytical approximation of the average spectral efficiency for each type of device is derived. Based on it, we obtain the optimal backoff parameter for each type of devices under their delay constraints. It is found that the optimal backoff parameters are closely related to the device number and delay constraint. In general, devices that have larger quantity should have more backoff time before they are allowed to access. However, as the delay constraint become stricter, the required backoff time reduces gradually, and the device with larger quantity may have less backoff time than that with smaller quantity when its delay constraint is extremely strict. When the pilot length is short, the effect of delay constraints mentioned above works more obviously.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권8호
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• pp.3068-3078
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• 2015

Although the massive MIMO system supports a high throughput, it requires a lot of channel information for channel compensation. For the reduction of overhead, the massive MIMO system generally uses TDD as duplexing scheme. Therefore, the massive MIMO system is sensitive to rapidly changing fast fading in according to time. For the improvement of reduced SINR by fast fading, the adaptive power control is proposed. Unlike the conventional scheme, the proposed scheme considers mobility of device for adaptive power control. The simulation of the proposed scheme is performed with consideration for mobility of device. The result of the simulation shows that the proposed scheme improves SINR. Since SINR is decreased in according to the number of device in the network by unit of cell, each base station can accommodate more devices by the proposed scheme. Also, because the massive MIMO system with high SINR can use high order modulation scheme, it can support higher throughput.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권2호
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• pp.974-987
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• 2018

This paper presents a novel and efficient data transmission scheme based on mobile edge computing for the massive IoT environments which should support various type of services and devices. Based on an accurate and precise synchronization process, it maximizes data transmission throughput, and consistently maintains a flow's latency. To this end, the proposed efficient software defined data transmission scheme (ESD-DTS) configures and utilizes synchronization zones in accordance with the 4 usage cases, which are end node-to-end node (EN-EN), end node-to-cloud network (EN-CN), end node-to-Internet node (EN-IN), and edge node-to-core node (EdN-CN); and it transmit the data by the required service attributes, which are divided into 3 groups (low-end group, medium-end group, and high-end group). In addition, the ESD-DTS provides a specific data transmission method, which is operated by a buffer threshold value, for the low-end group, and it effectively accommodates massive IT devices. By doing this, the proposed scheme not only supports a high, medium, and low quality of service, but also is complied with various 5G usage scenarios. The essential difference between the previous and the proposed scheme is that the existing schemes are used to handle each packet only to provide high quality and bandwidth, whereas the proposed scheme introduces synchronization zones for various type of services to manage the efficiency of each service flow. Performance evaluations show that the proposed scheme outperforms the previous schemes in terms of throughput, control message overhead, and latency. Therefore, the proposed ESD-DTS is very suitable for upcoming 5G networks in a variety of massive IoT environments with supporting mobile edge computing (MEC).

• 한국인터넷방송통신학회논문지
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• 제21권1호
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• pp.43-48
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• 2021

데이터 전송률을 증가시키기 위한 가장 효과적인 방법 중의 하나는 대용량 안테나 기술을 사용하는 것이다. 대용량 안테나 방식에서는 기지국에 수십 또는, 수백 개의 안테나를 설치하고 다중 사용자 기법을 통해 공간 다이버시티 이득을 향상시키는 방식이다. 다중 사용자 기법을 적용하면 사용자간 간섭이 발생하는데, 기존에는 수신기의 복잡도를 줄이고 간섭 신호를 제거하기 위하여 최대 비율 결합기를 사용하였다. 그러나, 동시 전송 단말 개수가 증가하면, 기존 수신기의 성능이 크게 열화되는 현상이 발생한다. 이러한 문제를 해결하기 위하여, 본 논문에서는 등록된 단말로부터의 간섭은 완벽하게 제거하고, 등록되지 않은 단말들로부터의 간섭은 줄여주는 검파기를 제안한다. 그리고 나서, 제안하는 검파기의 복잡도를 줄이기 위하여 적응형 검파기를 제안한다. 모의실험을 통하여, 제안하는 검파기가 기존의 검파기보다 더 우수한 비트 오율 성능을 갖는다는 것을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권2호
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• pp.742-756
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• 2022

A flood of information has occurred with the rise of the internet and digital devices in the fourth industrial revolution era. Every millisecond, massive amounts of structured and unstructured data are generated; smartphones, wearable devices, sensors, and self-driving cars are just a few examples of devices that currently generate massive amounts of data in our daily. Machine learning has been considered an approach to support and recognize patterns in data in many areas to provide a convenient way to other sectors, including the healthcare sector, government sector, banks, military sector, and more. However, the conventional machine learning model requires the data owner to upload their information to train the model in one central location to perform the model training. This classical model has caused data owners to worry about the risks of transferring private information because traditional machine learning is required to push their data to the cloud to process the model training. Furthermore, the training of machine learning and deep learning models requires massive computing resources. Thus, many researchers have jumped to a new model known as "Federated Learning". Federated learning is emerging to train Artificial Intelligence models over distributed clients, and it provides secure privacy information to the data owner. Hence, this paper implements Federated Averaging with a Deep Neural Network to classify the handwriting image and protect the sensitive data. Moreover, we compare the centralized machine learning model with federated averaging. The result shows the centralized machine learning model outperforms federated learning in terms of accuracy, but this classical model produces another risk, like privacy concern, due to the data being stored in the data center. The MNIST dataset was used in this experiment.

• 전자통신동향분석
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• 제37권1호
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• pp.32-41
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• 2022

With the development of computing technology, the convergence of ICT with existing traditional industries is being attempted. In particular, with the recent advent of 5G, connectivity with numerous AuT (autonomous Things) in the real world as well as simple mobile terminals has increased. As more devices are deployed in the real world, the need for technology for devices to learn and act autonomously to communicate with humans has begun to emerge. This article introduces "Device to the Edge," a new computing paradigm that enables various devices in smart spaces (e.g., factories, metaverse, shipyards, and city centers) to perform ultra-reliable, low-latency and high-speed processing regardless of the limitations of capability and performance. The proposed technology, referred to as EdgeCPS, can link devices to augmented virtual resources of edge servers to support complex artificial intelligence tasks and ultra-proximity services from low-specification/low-resource devices to high-performance devices.

• 한국통신학회논문지
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• 제41권11호
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• pp.1349-1355
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• 2016

5G 이동통신 예상 시나리오 중 하나로, 저 용량 전송을 하는 수많은 모바일 단말 및 센서 들이 급증할 것으로 예상하고 있다. 이러한 저 용량, 초 다수 기기들을 지원하기 위해서 저 복잡도를 갖는 단일 반송파 시스템이 고려될 수 있다. 이러한 조건을 만족시키기 위해, 본 논문에서는 단일 반송파 기반의 기존 CDMA(Code Division Multiple Access) 시스템 보다 2배의 유저를 수용할 수 있는 복소수 스프레딩을 사용하는 CDMA 시스템을 제안한다. 본 논문에서 제안하는 시스템은 Multi-level BPSK(Binary Phase Shift Keying) 변조를 사용한다. 제안하는 시스템은 실수와 허수로 구성된 칩 코드를 이용하여 전송하고자 하는 심볼을 스프레딩 한다. 시뮬레이션의 결과로 기존 CDMA 시스템에 비하여 BER(Bit Error Rate) 성능이 약 3dB 열화되나, 기존의 CDMA 시스템 대비 2배의 유저를 수용할 수 있어서 다중접속 효율 향상을 확인하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.64-67
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• 2003

The authors have settled general modular design by analyzing related literatures, but general modular design are too massive to be applicable to all process devices. So, the common parts have to be selected, applied, and modified for the devices. We have chosen the dry pulverizing/mixing device for example. We have elected the target modules of this device such as flange, hinge, bolt, nut coupling. The remote assembling and disassembling possibilities of the selected modules have been analyzed from the viewpoints of visibility, interference, approach, weight and so on. We have presented final modular design proper to the target modules. The modular designs which have adopted the modular property been analyzed. The modular design points are comprised of common and unique points. Some points are common for several devices, such as bolt, flange and so on. Others are unique for each device, such as power transmission coupling. The experimental devices have been modified by these modular design points and the design drawings have been presented.

• 디지털콘텐츠학회 논문지
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• 제15권4호
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• pp.527-532
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• 2014

최근 모바일 스마트 기기의 보급으로 스마트 기기에 탑재된 다양한 센서에서 수집되는 대량의 데이터를 분석하여 처리하는 빅 데이터의 시대는 위치기반 서비스(LBSs: Location-Based Services)에 까지 확대대고 있다. 이동객체 위치 예측 기술은 차세대 시공간 정보 서비스에서 요구하는 필수적인 기술로 많은 연구가 진행되어 왔다. 그러나 대부분의 기존연구는 특정 어플리케이션에 종속적인 이동객체 위치 예측 질의처리 연구로서 증가하는 차세대 시공간 정보 서비스의 기술적 요구를 반영하기가 어렵다. 따라서 본 논문은 실세계 공간 네트워크에서 이동객체들의 초대용량 시공간적 데이터를 토대로 필수적으로 예측에 필요한 기본적이고 다양한 질의를 효율적으로 처리할 수 있는 범용적 분산 이동객체 예측 질의처리 프레임워크 설계를 제안한다.