• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권5호
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• pp.1642-1661
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• 2015

Wireless mesh networks are a special type of broadcast networks which cover the qualifications of both ad-hoc as well as infrastructure mode networks. These networks offer connectivity to the last mile through hop to hop communication and by comparatively reducing the cost of infrastructure in terms of wire and hardware. Channel assignment has always been the focused area for such networks specifically when using non-overlapping channels and sharing radio frequency spectrum while using multiple radios. It has always been a challenge for mesh network on impartial utilization of the resources (channels), with the increase in users. The rational utilization of multiple channels and multiple radios, not only increases the overall throughput, capacity and scalability, but also creates significant complexities for channel assignment methods. For a better understanding of research challenges, this paper discusses heuristic methods, measurements and channel utilization applications and also examines various researches that yield to overcome this problem. Finally, we highlight prospective directions of research.

• Journal of electromagnetic engineering and science
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• 제11권2호
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• pp.128-132
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• 2011

In interference tolerance based spectrum sharing systems, primary receivers (PRs) are protected by a predefined peak or average interference power constraint. To implement such systems, cognitive radio (CR) transmitters are required to adjust their transmit power so that the interference power received at the PR receivers is kept below the threshold value. Hence, a CR-transmitter requires knowledge of its channel and the primary receiver in order to allocate the transmit power. In practice, it is impossible or very difficult for a CR transmitter to have perfect knowledge of this channel state information (CSI). In this paper, we investigate the impact of imperfect knowledge of this CSI on the performances of both a primary and cognitive radio network. For fixed transmit power, average interference power (AIP) constraint can be maintained through knowledge of the channel distribution information. To maintain the peak interference power (PIP) constraint, on the other hand, the CR-transmitter requires the instantaneous CSI of its channel with the primary receiver. First, we show that, compared to the PIP constraint with perfect CSI, the AIP constraint is advantageous for primary users but not for CR users. Then, we consider a PIP constraint with imperfect CSI at the CR-transmitter. We show that inaccuracy in CSI reduces the interference at the PR-receivers that is caused by the CR-transmitter. Consequently the proposed schemes improve the capacity of the primary links. Contrarily, the capacities of the CR links significantly degrade due to the inaccuracy in CSI.

• 전자통신동향분석
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• 제30권3호
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• pp.84-94
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• 2015

5G와 IoT로 인한 무선 트래픽 급증에 대응하기 위해서는, 무선망 성능 및 주파수효율 향상, 신규주파수할당, 주파수 공동사용 기술 개발 등이 복합적으로 적용되어야 달성 가능하다. 그의 일환으로, LTE를 비면허 대역에 사용하려는 LTE-U(Long Term Evolution-Unlicensed)라는 새로운 패러다임의 수평적 주파수 공동사용 기술을, 이동통신에 적용하려는 시도가 진행되고 있다. LTE-A의 주파수 집성기술을 활용하여, 1차 캐리어를 면허 대역 LTE 기반으로 하고, 2차 캐리어를 비면허 대역 LTE로 묶어서 고속으로 데이터를 전송하는 기술이다. 우선적으로 5GHz 비면허 대역에 적용을 검토하고 있는데, 기존에 사용하던 Wi-Fi 및 기상레이다 등과의 공정한 공존(fair coexistence)이 가장 중요하다. 따라서 각국의 5GHz 주파수 대역 규제 현황, 공존을 위한 LBT(Listen-Before-Talk)통신 메커니즘, 표준화 현황을 살펴본다. 또한 이해 당사자인 Wi-Fi, LTE, 이용자, 기술기준의 입장을 살펴보고, 구현이슈, 지적소유권 동향 등을 검토하고, 기술적 및 정책적 대응전략을 살펴본다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 춘계학술대회
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• pp.591-593
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• 2016

Device-to-device (D2D) communications underlaid cellular infrastructure is an competitive local area services technology to promote spectrum usage for next generation cellular networks. These potential can only be tap through efficient interference coordination. Previous works only concentrated on interference from D2D pairs whiles interference from CUs to D2D pairs were neglected. This work focus on solving uplink interference problem emanating from multiple CUs sharing its resource with multiple D2D pairs. The base station (BS) acting as a supervisor selfishly institute a pricing scheme to manage the interference it experience from D2D pairs based on its Quality of service (QoS) requirement. D2D pairs following the supervisor make power allocation decisions considering the price from the BS in a non-cooperative game fashion. In order for the D2D pairs to also meet their QoS requirement, they suggest a price to the BS called discount price which reflects the interference they receive from the CUs. Finally, we analyze the proposed approach.

• 한국측량학회지
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• 제25권1호
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• pp.69-75
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• 2007

The information in physical planning field shows the socio-economic potentials of land resources while cadastral data does the physical and legal realities of the land. The two domains commonly deal with land information but have different views. Cadastre has to evolved to the multi-purpose ones which provide value-added information and support a wide spectrum of decision makers by mixing their own information with other spatial/non-spatial databases. In this context, the demands of data exchange between the two domains is growing up but this cannot be done without resolving the heterogeneity between the two information applications. Both of either discipline sees the reality within its own scope, which means each has a unique way to abstract real world phenomena to the database. The heterogeneity problem emerges when an GIS is autonomously and independently established. It causes considerable communication difficulties since heterogeneity of representations forms unique data semantics for each database. The semantic heterogeneity obviously creates an obstacle to data exchange but, at the same time, it can be a key to solve the problems too. Therefore, the study focuses on facilitating data sharing between the fields of cadastre and physical planning by resolving the semantic heterogeneity. The core job is developing a conversion mechanism of cadastral data into the information for the physical planning by DB coupling techniques.

• 한국유기농업학회지
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• 제16권3호
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• pp.239-258
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• 2008

This study identifies the spectrum of different forms of sharing labor in farm houses following the increase in the production of organic produce and deals with the gender division of labor and every day life of the farm households. The increased labor burdens of organic farming give more work opportunities to wives, weakening the gender barriers. However, some of the farm households seeking for economic feasibility are strengthening the gender barriers by specialized work divisions, leading to outside order labor of harvest, sorting, and packaging in order to increase efficiency in agricultural management in extreme cases. Even in the alternative distribution system, farm households has become subject to the distribution system as it is shown that coop claimed the segmentation of sorting work. This is because the convenience of the customers goes before the advantages of producers. Jinju, seeking for economic feasibility, has established the springboard for growth by greenhouse through monoculture and specialization and are operating economic growth stably. Farm couples with this condition, where their incomes are relatively high, are attempting to recharge their energy during low seasons. It is expected that this will be a model case of conventionalization of organic farming. Significance of organic farming in this matter is discussed.

• ETRI Journal
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• 제43권3호
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• pp.389-399
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• 2021

In this paper, we propose one-bit feedback-based distributed beamforming (DBF) techniques for simultaneous wireless information and power transfer in interference channels where the information transfer and power transfer networks coexist in the same frequency spectrum band. In a power transfer network, multiple distributed energy transmission nodes transmit their energy signals to a single energy receiving node capable of harvesting wireless radio frequency energy. Here, by considering the Internet-of-Things sensor network, the energy harvesting/information decoding receivers (ERx/IRx) can report their status (which may include the received signal strength, interference, and channel state information) through one-bit feedback channels. To maximize the amount of energy transferred to the ERx and simultaneously minimize the interference to the IRx, we developed a DBF technique based on one-bit feedback from the ERx/IRx without sharing the information among distributed transmit nodes. Finally, the proposed DBF algorithm in the interference channel is verified through the simulations and also implemented in real time by using GNU radio and universal software radio peripheral.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권6호
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• pp.2240-2254
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• 2021

We investigate the channel allocation problem in an ultra-dense device-to-device (D2D) enabled cellular network in underlaying mode where multiple D2D users are forced to share the same channel. Two kinds of low complexity solutions, which just require partial channel state information (CSI) exchange, are devised to resolve the combinatorial optimization problem with the quality of service (QoS) guaranteeing. We begin by sorting the cellular users equipment (CUEs) links in sequence in a matric of interference tolerance for ensuring the SINR requirement. Moreover, the interference quota of CUEs is regarded as one kind of communication resource. Multiple D2D candidates compete for the interference quota to establish spectrum sharing links. Then base station calculates the occupation of interference quota by D2D users with partial CSI such as the interference channel gain of D2D users and the channel gain of D2D themselves, and carries out the channel allocation by setting different access priorities distribution. In this paper, we proposed two novel fast matching algorithms utilize partial information rather than global CSI exchanging, which reduce the computation complexity. Numerical results reveal that, our proposed algorithms achieve outstanding performance than the contrast algorithms including Hungarian algorithm in terms of throughput, fairness and access rate. Specifically, the performance of our proposed channel allocation algorithm is more superior in ultra-dense D2D scenarios.

• 인간행동과 음악연구
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• 제19권2호
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• pp.27-53
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• 2022

본 연구는 고기능 자폐스팩트럼장애(ASD) 아동을 대상으로 학교에서 보편적으로 경험하게 되는 사회적 상황을 기반으로 구성된 음악극을 적용하였을 때 의사소통기술에 어떠한 변화를 보이는 지 알아보고자 진행되었다. 본 연구에 적용된 음악극은 실제적 상황에 대한 이해, 음악 안에서의 목표 행동 및 언어적 표현의 습득, 역할극을 통한 상황적 맥락 내 목표 행동의 실제적 적용을 유도하는 단계적 구조로 구성되었다. 대상자는 평균 연령 9세의 ASD 아동 3명이며, 주 2회 40분씩 총 8회기의 그룹 중재가 진행되었다. 결과분석을 위해 또래 및 성인(즉, 연구자) 대상 의견 개시 및 조율 행동, 대상자 간 자발적 상호작용 행동을 관찰하였으며, 사회적 기술 평정척도 실시를 통해 중재 전후 일상생활에서 나타나는 사회적 행동에 변화가 있는지 비교하였다. 분석 결과, 모든 대상자는 또래 대상 의견 개시 및 조율 행동과 성인 대상 자발적 상호작용 행동이 증가한 것으로 나타났다. 반면 또래에게 나타나는 자발적 상호작용 행동과 성인 대상 의견 개시 및 조율 행동에 있어서는 대상자 언어 및 발달 수준에 따라 개별적인 차이가 있었다. 이러한 결과는 사회적 상황 기반 음악극이 ASD 아동이 경험하는 사회적 환경과 유사한 맥락을 제시함으로써 실제적으로 요구되는 의사소통 행동과 타인과의 상호작용 시 자신의 행동을 보다 효과적으로 조절하도록 촉진할 수 있는 가능성을 뒷받침한다. 또한, 본 연구는 ASD 아동의 사회적 의사소통 향상을 위한 중재의 범위를 확장하고, 다각적 전략을 제시했다는 데 그 의의가 있다.

• 한국전자파학회논문지
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• 제28권12호
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• pp.974-981
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• 2017

전 세계적으로 무선국의 급격한 확대로 인해 해외에서는 사전조정제도로서 주파수 코디네이터 제도를 운영하고 있다. 이에 따라 국내에도 향후에는 5G, 면허 및 비면허 기반의 소출력 장거리 IoT 기기 등 많은 종류의 무선국 확대가 예상되고, 특히 융합상품으로 출시되는 드론, 전파자원의 불요발사, 주파수공동사용 등 자원의 문제가 야기되고 있어 상기제도 또는 다른 방안의 제도 도입을 검토할 필요가 있다. 본 논문에서는 무선국 인 허가제도의 개요와 타 산업 인 허가에 대해 조사한 내용을 소개하고 무선국 인 허가와 타 산업을 위주로 총 19가지의 절차 법령을 조사하였으며 인 허가 절차에 대한 도표를 도시화하고, 유사한 타 산업 인 허가에 대한 비교항목 선정과 공통점 및 특이점을 분석하여 실선 그래프 방식을 이용하여 개별제도 상호 간의 차이점을 비교분석하였다. 또한 이를 통해 향후에 드론과 같은 융합상품에 발생될 우려가 있는 문제점에 대해 논의하고 시사점을 고찰하였다.