저전력광대역 네트워크를 위한 LoRa: 개요 및 성능향상 기술

조웅 한국전자통신학회 2019 한국전자통신학회 논문지 Vol.14 No.2

저전력광대역 (LPWA: Low Power Wide Area) 네트워크는 기존의 무선통신 기술들에 비해 저전력으로 장거리 통신을 가능하게 하여 사물인터넷의 여러 응용분야에서 적용될 수 있는 기술 중 하나로 고려되어지고 있다. 본 논문에서는 저전력광대역 네트워크의 대표적인 기술 중 하나인 LoRa (Long Range)에 대해 알아본다. 먼저 저전력광대역 네트워크의 일반적인 특징 및 관련기술에 대해 소개한다. 그리고, LoRa의 기술개요, 특징 및 장단점에 대해 소개한다. 마지막으로 LoRa의 성능분석 및 성능을 향상시키기 위해 필요한 기술들을 물리계층과 매체접근제어 계층에 중점을 두고 논의한다. LPWA (Low Power Wide Area) networks have been considered as one of technologies which can be implemented in IoT (Internet of Things) applications by providing less power and longer communication range compared with existing wireless technologies. In this paper, we investigate LoRa which is one of representative technologies for LPWA networks. First, we present general properties and several technologies of LPWA networks. Then, the technical specification, properties, and pros/cons of LoRa are studied. Finally, we discuss LoRa’s performance analysis and its performance enhancement technologies by focusing on physical layer and MAC (Medium Access Control) layer.

IEEE 802.11p 기반 통신시스템의 대용량 전송 성능 측정

조웅,최현경,Cho, Woong,Choi, Hyun-Kyung 한국전자통신학회 2014 한국전자통신학회 논문지 Vol.9 No.12

IEEE 802.11p는 차량통신 시스템의 대표적인 물리계층 및 매체접근제어계층 표준이다. IEEE 802.11p를 기반으로 한 통신시스템의 일대일 통신성능은 링크접속시간, 오류율, 전송용량 (throughput), 등의 다양한 형태로 측정되었다. 본 논문에서는 IEEE 802.11p기반 통신시스템을 이용하여 대용량으로 신호 전송 시 성능을 측정한다. 일대일 통신을 포함하여 최대 32개의 통신시스템을 사용하여 데이터를 전송하였을 경우에 대한 성능을 측정한다. 전송방식은 브로드캐스트와 유니캐스트 두 가지 경우에 대해 고려하며, 통신시스템의 성능은 수신율 및 전송용량을 이용하여 나타낸다. IEEE 802.11p is a representative PHY/MAC layer standard in vehicular communications. The performance of IEEE 802.11p based communication systems has been measured in various criterions such as link setup time, error rate, and throughput for the case of one-to-one. In this paper, we measure the performance of IEEE 802.11p based communication systems in large capacity transmission. The performance of large capacity transmission is measured by considering the maximum 32 simultaneous transmission including one-to-one transmission. We consider two transmission schemes, i.e., broadcasting and unicasting, and the performance is represented as the receiving rate and throughput.

WAVE 핸드오버상에서 수신 신호 세기의 이용

조웅 한국전자통신학회 2012 한국전자통신학회 논문지 Vol.7 No.6

Received signal strength indicator (RSSI) represents the strength of the received signal at the front end of analog-to-digital convertor (ADC) input. RSSI value can be used for deciding the status of channel at the receiver. In this paper, the usage of RSSI in handover is studied using the practical measurement data. We first measure RSSI in 5.9GHz frequency band which is commonly used in wireless access in vehicular environments (WAVE) system. i.e., vehicular communications. Then, to implement a fast handover, the usability of RSSI data is analyzed based on the measured data. We also apply handover in practical highway environments. 수신 신호 세기 (RSSI: Received signal strength indicator)는 아날로그-디지털 변환기 입력단에서 수신신호의 세기를 나타낸다. 통신시스템에서 수신 신호 세기는 수신단에서 채널의 상태를 결정하는데 사용된다. 본 논문에서는 핸드오버상에서 실측값을 바탕으로 한 수신 신호 세기의 이용에 대해 알아본다. 먼저 WAVE (Wireless Access in Vehicular Environments)라 일컫어지는 차량통신을 위한 5.9GHz 주파수대에서 RSSI값을측정한다. 측정된 데이터를 바탕으로 하여 빠른 핸드오버 방식 적용을 위한 수신 신호 세기의 이용에 대해 논의하고, 실제 고속도로 환경에서 RSSI를 이용하여 핸드오버를 적용한다.

1893년 하와이 혁명에 관한 연구

조웅 전남사학회 1994 역사학연구 Vol.8 No.-

차량통신에서의 물리계층 이슈

조웅,Cho, Woong 한국전자통신학회 2012 한국전자통신학회 논문지 Vol.7 No.5

차량통신은 통신시스템과 차량산업을 융합하여 ITS (Intelligent Transport Systems)분야에서 다양한 서비스 제공을 위해 고려되어져 왔다. 일반적으로 차량통신은 WAVE (Wireless Access in Vehicular Environments)라고 알려져 있는 IEEE 802.11p/1609표준을 채택하여 차량간 통신 및 차량-노변기지국간 통신에 이용된다. WAVE 시스템은 OFDM (Orthogonal Frequency Division Multiplexing) 신호를 5.9GHz대의 주파수를 사용하여 신호를 전송하는 시스템이다. 본 논문에서는 차량통신 영역 중 물리계층의 이슈들에 관하여 논의한다. 먼저 WAVE 표준의 물리계층과 5.9GHz대의 신호의 특성에 대해 살펴본 후 신뢰성 있는 통신링크 제공을 위해 물리계층에서 개선되어야할 점에 대해 논의한다. Vehicular communications have been receiving much attention in intelligent transport systems (ITS) by combining communication technology with automobile industries. In general, vehicular communications can be used for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication by adopting IEEE802.11p/1609 standard which is commonly known as wireless access in vehicular environments (WAVE). WAVE system transmits signal in 5.9GHz frequency band with orthogonal frequency division multiplexing (OFDM) signaling. In this paper, we consider physical layer issues in vehicular communications. We first overview the physical (PHY) layer of WAVE standard and properties of 5.9GHz signals, and then physical layer issues to provide reliable communication link are discussed.

테스트베드상에서 WAVE기반 차량통신 시스템의서비스 구현

조웅 한국전자통신학회 2013 한국전자통신학회 논문지 Vol.8 No.10

차량통신은 IT기술과 차량산업을 결합한 대표적인 융합기술이다. WAVE 기술은 전 세계적으로 널리 채택되어 사용되어지고 있는 차량통신 표준이다. 본 논문에서는 WAVE 시스템 이용하여 실제 테스트베드상에서구현한 서비스에 대해 소개한다. 먼저 전체적인 WAVE 시스템에 대해 간략히 살펴본 후 서비스를 구현하기위한 테트스베드에 대해 소개하고, 테스트베드상에서 구현된 차량간통신 및 차량 기지국간통신을 이용한 다양한 응용 서비스에 대해 알아본다. 실제 응용 서비스의 구현을 바탕으로 하여 실제 시스템 구현에 필요한 사항 및 다른 분야와의 융합분야에 대해서도 논의한다. Vehicular communication is one of representative convergence technology which combines information technology and vehicle industry. Wireless Access in Vehicular Environments (WAVE) technology is vehicular communication standard which is widely used in the world. In this paper, we introduce service realization of WAVE based vehicular communication systems in the practical testbed. We review the overall WAVE based systems in brief and introduce the testbed. Then, we investigate various applications using vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications. Based on realization of systems, we discuss practical implementation issues and the convergence area of WAVE systems.

1897년 일본의 하와이 위협

趙雄 전남사학회 1995 역사학연구 Vol.9 No.-

Kinetics Analysis during Stance Phase of Fore Foot Contact Versus Rear Foot Contact in Running

조웅,한재웅,김아영,박성규,김형수 국제물리치료연구학회 2017 Journal of International Academy of Physical Ther Vol.8 No.1

The purpose of this study was to compare and analyze the difference of the ankle joint movements during landing. Seven adult males voluntarily participated in the study and the average foot size of the subjects was 269.8 mm. Image analysis equipment and the ground reaction force plate (landing type) was used to measure th kinetic variables. As a result of this study, it was confirmed that the vertical ground reaction force peak point appeared once in the barefoot with forefoot, while two peak points appeared in the barefoot and functional shoe foot with rear foot landing. About ankle angle, fore foot landing ankle angle, the average with bare foot landing was -10.302° and the average with functional shoe foot landing was -2.919°. Also about rear foot landing, ankle angle was 11.648° with bare foot landing and 15.994° with functional shoe landing. The fore foot landing, ankle joint force analysis produced 1423.966N with barefoot and 1493.264N with functional shoes. But, the rear foot landing, ankle joint force analysis produced 1680.154N with barefoot and 1657.286N with functional shoes. This study suggest that the angle of ankle depends on the landing type and bare foot running/functionalized shod running, and ankle joint forces also depends on landing type.

Practical Implementation of a Collapsed Cone Convolution Algorithm for a Radiation Treatment Planning System

조웅,서태석,박정훈,Lei Xing,이정우 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.12

A collapsed cone convolution algorithm was applied to a treatment planning system for the calculation of dose distributions. The distribution of beam fluences was determined using a three-source model by considering the source strengths of the primary beam, the scattered beam from the primary collimators, and an extra scattered beam from extra structures in the gantry head of the radiotherapy treatment machine. The distribution of the total energy released in media (TERMA) was calculated from the distribution of the fluence by considering several physical effects such as the polyenergetic photon spectra, attenuation of beam fluence in a medium, horn effect, beam-softening effect, and beam transmission through collimators or multi-leaf collimators. The distribution of the doses was calculated by the convolution of the distribution of TERMA and the polyenergetic kernel. The distribution of the kernel was approximated to several tens of collapsed cone lines to express the energies transferred by electrons that originate from the interactions between the photons and the medium. The implemented algorithm was validated by comparing the calculated percentage depth doses (PDD) and dose profiles with the measured PDDs and relevant profiles. In addition, the dose distribution for an irregular-shaped radiation field was verified by comparing the calculated doses with the measured doses obtained via EDR2 film dosimetry and the calculated doses obtained using a different treatment planning system based on the pencil beam algorithm (Eclipse, Varian, Palo Alto, USA). The majority of calculated doses for PDDs, profiles, and the irregular-shaped field showed good agreement with the measured doses within 2% of dose difference, except in the build-up regions. The implemented algorithm was proven to be efficient and accurate for clinical purposes in radiation therapy, and it was found to be easily implementable in treatment planning systems.

여성의 농촌관광 만족과 재방문에 관한 연구

조웅,정용악 한국관광산업학회 2012 Tourism Research Vol.37 No.-

People often travels in a family unit and for such a modern-day society family, those who make a decision is not one but 'mom'. With varied types of travel that each family takes by children age, those families with their kids prefer hands-on experience program, in which case the farmland travel marketing counts and marketing strategy for a decision-making mom will be crucial. According to the study's analysis upon what motivated families to participate in the farmland travel, most of women feel and become aware of their 'ego' when visiting farmland, while taking 'rural atmosphere' into account when visiting again. That women struggle with their urban life and sacrifice their own lives in the name of 'housewife' by putting the familial value first appears to contribute to such results, which signify the direction of farmland travel should chase after, the ego-finding, self-developing, and life-recharging experiences for hectic women. Agin, taking rural atmosphere into account, it is also significant to emphasize the regional peculiarity, environment-friendliness, and village-unit travel system, as well as keeping the natural, cultural, and region-specific values without mere imitation of just another travel packages and villages. What is important here is keeping and developing the conventional value that our ancestors have kept and reflecting such into modern-day travel programs involving hands-on experiences.