• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.6
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• pp.15-21
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• 2009

The goal of wireless sensor networks is to collect sensing data on specific region over wireless communication. Sink node gathers all local sensing data, processes and transmits them to users who use sensor networks. Generally, senor nodes are low-cost, low power devices with limited sensing, computation and wireless communication capabilities. And sensor network applies to multi-hop communication on large-scale network. As neighboring sensor nodes have similar data, clustering is more effective technique for 'data-aggregation'. In cluster formation technique based on multi-hop, it is necessary that the number of cluster member nodes should be distributed equally because of the balance of cluster formation To achieve this, we propose a method to customize cluster member nodes for energy-efficiency in wireless sensor networks.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.12
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• pp.1395-1402
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• 2015

An electric heat tracing system manages the temperature of pipes used in a plant. We propose a Zigbee-based wireless system so called the TESCON(: TEmperature Sensing and CONtrol) to monitor and control the electric heat tracing system in an integrated way. Simulations have been done to analyze the performance of the TESCON system. The performance of the TESCON system is validated by obtaining similar results via testbed operation. We also suggest an extension method of the TESCON system based on the hierarchical tree topology by adopting techniques such as network partition, channel reuse and frame aggregation.

• Proceedings of the Korea Contents Association Conference
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• 2006.11a
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• pp.469-473
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• 2006

Nowadays, to realize ubiquitous computing environment, many research activities have been going on within various kinds of research domains including automatic identification, sensor network, home network, telematics and so on. Especially, RFID middle-ware that supports the aggregation of RFID tag data, control and management, and the integration with legacy systems has recently gained a lot of attention. Meanwhile, EPCglobal defined an ALE(Application Level Events) standard specification, which exists between RFID readers and applications, and substitutes the previous systems called Savant. In the specification internal structures and implementation technologies of ALE are not mentioned and only external interfaces are defined. This approach easies the verification of standard compliance and inter-operability of the layer. In this paper, we present the design of ALE-compliant RFID middle-ware systems that process RFID tag data efficiently.

• Journal of Broadcast Engineering
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• v.19 no.4
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• pp.510-520
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• 2014

By adopting the MAC(Media Access Control) protocol which enables to pack multiple MPDUs(MAC-level Protocol Data Units) into a single PPDU(Physical Layer Protocol Data Unit), IEEE 802.11n WLAN supports high throughput. Up to now, there have been a lot of existing channel information-based A-MPDU schemes dynamically determining the number of MSDUs according to the wireless channel condition information which is sent from the receiver to sender. However, the channel information-based scheme has a serious drawback having a high system overhead due to the frequent channel feedback information. To reduce the system overhead, the proposed BA-base dynamic A-MPDU scheme simply chooses the number of MSDUs to be retransmitted by not the frequent channel feedback information but the BA signal representing whether MPSUs belonging to the A-MPDU are received or not. Through NS-2(Network Simulator-2), we found that the proposed scheme had higher throughput and lower packet error rate than the existing fixed A-MPDU scheme.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2815-2822
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• 2011

Clustering method in wireless sensor networks is the technique that forms the cluster to aggregate the data and transmit them at the same time that they can use the energy efficiently. In this paper, I propose the hierarchical unequal clustering method using cluster group model. This divides the entire network into two layers. The data aggregated from layer 2 consisted of cluster group is sent to layer 1, after re-aggregation the total data is sent to base station. This method decreases whole energy consumption by using cluster group model with multi-hop communication architecture. Hot spot problem can be solved by establishing unequal cluster. I also show that proposed hierarchical unequal clustering method is better than previous clustering method at the point of network energy efficiency.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.1-10
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• 2009

Energy efficient operations are essential to increase the life time of wireless sensor network. A cluster-based protocol is the most common approach to preserve energy during a data aggregation. This paper deals with an energy awareness and autonomous clustering method based on time delay. This method consists of three stages. In the first phase, Candidate Cluster Headers(CCHs) are selected based on a time delay which reflects the remaining energy of a node, with considering coverage efficiency of a cluster. Then, time delay is again applied to declare Cluster Headers(CHs) out of the CCHs. In the last phase, the issue on an orphan node which is not included into a cluster is resolved. The simulation results show that the proposed method increases the life time of the network around triple times longer than LEACH(Low Energy Adaptive Cluster Hierarchy). Moreover, the cluster header frequency is less diverse, and the energy on cluster heads is less spent.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.8
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• pp.999-1005
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• 2020

While search portals' 'Portal News' account for the largest portion of aggregated news outlet, its neutrality as an outlet is questionable. This is because news aggregation may lead to prejudiced information consumption by recommending biased news articles. In this paper we introduce a new method of measuring political bias of news articles by using deep learning. It can provide its readers with insights on critical thinking. For this method, we build the dataset for deep learning by analyzing articles' bias from keywords, sourced from the National Assembly proceedings, and assigning bias to said keywords. Based on these data, news article bias is calculated by applying deep learning with a combination of Convolution Neural Network and Recurrent Neural Network. Using this method, 95.6% of sentences are correctly distinguished as either conservative or progressive-biased; on the entire article, the accuracy is 46.0%. This enables analyzing any articles' bias between conservative and progressive unlike previous methods that were limited on article subjects.

• Journal of Korean Society of Transportation
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• v.25 no.4
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• pp.123-133
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• 2007

This study analyzed whether a transit network with hierarchy is efficient or not, and if transit network hierarchy has cost efficiency, then which condition guarantees the efficiency of the transit network hierarchy. The authors modeled the total cost of the transit network and suggested the conditions in which the transit network hierarchy has cost efficiency through comparing the cost of the transit network with and without hierarchy. The efficiency of transit network hierarchy is guaranteed when the travel cost savings induced by using a higher hierarchy transit network is larger than the increasing non-travel cost, which is the sum of access cost, waiting cost, and operating cost, induced by the introduction of a higher hierarchy transit network. This result is consistent with common sense and with the concept of cost and benefit analysis. If a passenger traveling within the area divided by a higher hierarchy transit network uses only a lower hierarchy transit network and the passenger traveling out of the area divided by the higher hierarchy transit network uses both lower and higher hierarchy transit networks, the travel demand using the higher hierarchy transit network is inversely proportional to the square of the line spacing. This means that the transit network becomes more efficient and small increases of travel demand guarantee the efficiency of the transit network hierarchy as the connectivity of the network becomes higher. This result shows that transit networks have economies of aggregation. This study is the first analytical research on transit network hierarchy and is expected to be a basis for numerical research. However, numerical research should complement this study, since analytical research has some limitations for considering a real network.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.12
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• pp.1244-1248
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• 2010

The previous study of Digital Broadcasting Recommendation system is based on user explicit profiling information. But user profile is always changing and the exact extraction of user profile is very important in recommendation system like Digital TV using many user interactions. This paper is studied of realtime user profiles aggregation through user remote controller input and matching this profiles with contents meta-data like contents genre information, event information, content viewing time. It is not used commercial database system and network communication solution considering embedded system hardware restriction. And it is considered people want different content genre based on watching time. From the results of this paper, there are improvement of user satisfaction of contents recommendation.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10b
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• pp.138-142
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• 2006

분산 센서 네트워크에 대한 연구는 정보 융합 방법론상에서 활발히 진행되고 있다. 기존의 센서 네트워크에서 정보의 융합을 위한 데이터의 수집은 센서 노드가 싱크 노드로 수집된 데이터를 전송함으로써 이루어지며 싱크 노드로 수집된 데이터는 어플리케이션에 의해 활용된다. 이때 여러 센서 노드가 어플리케이션에 필요한 데이터를 중복적으로 수집할 경우 중복된 데이터를 싱크노드로 전송하는데 있어 불필요한 에너지를 소모하게 된다. 이는 결국 전체적인 센서 네트워크의 수명을 감소시키는 원인이 된다. 이러한 문제는 어플리케이션에 따라 요구하는 데이터만을 선택적으로 수집함으로써 해결할 수 있다. 이러한 과정을 수행하기 위해 각 센서 노드가 어플리케이션의 요구사항에 맞도록 데이터 중복성에 대한 처리과정을 수반해야한다. 그러나 일반적으로 센서 노드는 자원이 한정이 되어있기 때문에 다양한 어플리케이션의 요구에 따른 중복성 처리 프로세스를 모두 가지고 있을 수는 없다. 따라서 모바일 에이전트를 활용하여 데이터의 중복성 문제를 해결할 수 있다. 또한 센서 네트워크에서 고려되는 에너지 효율, 네트워크 대역폭 문제를 해결할 수 있으며 시스템 확장성이 용이하다.