• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.142-152
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• 2016

GPS is not able to be used for indoor positioning and currently most of techniques emerging to overcome the limit of GPS utilize private wireless networks. However, these methods require high costs for installation and maintenance, and they are inappropriate to be used in the place where precise positioning is needed as in indoor parking lots. This paper proposes a vehicular indoor positioning method based on QR-code recognition. The method gets an absolute coordinate through QR-code scanning, and obtain the location (an relative coordinate) of a black-box camera using the tilt and roll angle correction through affine transformation, scale transformation, and trigonometric function. Using these information of an absolute coordinate and an relative one, the precise position of a car is estimated. As a result, average error of 13.79cm is achieved and it corresponds to just 27.6% error rate in contrast to 50cm error of the recent technique based on wireless networks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.1009-1016
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• 2015

In this paper, we propose EPCM(Efficient Prediction-based Context-awareness Matrix) algorithm analyzing connectivity by predicting cluster's context data such as velocity and direction. In the existing DTN, unrestricted relay node selection causes an increase of delay and packet loss. The overhead is occurred by limited storage and capability. Therefore, we propose the EPCM algorithm analyzing predicted context data using context matrix and adaptive revision weight, and selecting relay node by considering connectivity between cluster and base station. The proposed algorithm saves context data to the context matrix and analyzes context according to variation and predicts context data after revision from adaptive revision weight. From the simulation results, the EPCM algorithm provides the high packet delivery ratio by selecting relay node according to predicted context data matrix.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10B
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• pp.894-903
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• 2008

The position of sensors generally affects coverage, communication costs, and resource management of surveillance sensor networks. Thus we are required to place a sensor in the best location. However, it is difficult to consider that terrain and climate factors influencing sensors when sensor nodes are deployed in the real world, such as a mountain area or a downtown area. We therefore require a sensor deployment method for detecting effectively targets of interest in terms of surveillance area coverage in such environment. Thus in this paper, we analyze various environmental factors related to sensor deployment, and quantify these factors to use when we deploy sensors. By considering these quantified factors, we propose a practical and effective method for deploying sensors in terms of sensing coverage. We also demonstrate the propriety of the proposed method through implementing a sensor deployment management system according to the method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.1
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• pp.63-71
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• 2013

In order to support mobility for sink groups, it is important to get the current location of a mobile sink group and then to offer the location to a source. Typically, previous works calculate a region including all member sinks by flooding; then, it notifies this region information to a source. However, flooding and location updates are periodically performed regardless of the group movement so that it causes considerable control overhead. In this paper, we propose an energy-efficient scheme supporting mobile sink groups. The proposed scheme obtains a location of a group without flooding. It exploits the inherent property of mobile sink groups which could approximate entire group movement by only partial member sinks movement. Also, the scheme learns group location by back-propagation learning method through exploiting overhearing feature in wireless communication environment. Our simulation studies show that the proposed scheme significantly improves in terms of energy consumption compared to the previous work.

• Journal of KIISE:Information Networking
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• v.31 no.6
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• pp.573-581
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• 2004

Recently, the rapid growth of Internet technology and the deployment of high speed networks make many kinds of multimedia services possible. Preexisting multimedia services are designed based on the client/server model which has the problems such as the network failure and the low speed communication due to the high load on the central server. In order to solve these problems, peer-to-peer networks are introduced and expanded through Internet environments. In this paper, we propose a pure peer-to-peer network based resource discovery mechanism for multimedia services. In the proposed scheme, each host maintains the location information of resources which are recently requested by other hosts as well as that oi the replicas of local resources. The proposed scheme has the faster response time and incurs the smaller traffic than the preexisting discovery schemes in pure peer-to-peer network environments. Also, by decentralizing the location information and differentiating the reply path, our proposed scheme can solve the search result loss problem that occurs when the network is unsettled.

• Journal of KIISE:Information Networking
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• v.30 no.2
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• pp.179-188
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• 2003

Advances in wireless networking technology has engendered a new paradigm of computing, called mobile computing, in which users carrying portable devices have access to a shared infrastructure independent of their physical locations. Wireless communication has some restraints such as disconnection, low bandwidth, a variation of available bandwidth, network heterogeneity, security risk, small storage, and low power. Power adaptation routing scheme overcome the shortage of power by adjusting the output power, was proposed. Existing power saving routing algorithm has some minor effect such as seceding from shortest path to minimize the power consumption, and number of nodes that Participate in routing than optimal because it select a next node with considering only consuming power. This paper supplements the weak point in the existing power saving routing algorithm as considering the gradual approach to final destination and the number of optimal nodes that participate in routing.

• Journal of KIISE:Information Networking
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• v.35 no.3
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• pp.227-234
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• 2008

The development of wireless network technology allows high data rate seamless communication irrespective of the place and time in various emerging mobile service environment. Unlike wired networks, however, wireless networks utilize expensive limited bandwidth. MBS(Multicast Broadcast Service), which is supported by mobile WiMAX system based on IEEE802.16e, overcomes this problem using a shared downlink channel for efficiently supporting a number of users. However. the coverage and throughput of the system are significantly affected by the channel condition. In this paper we propose on MBS system employing Mobile Multi-Hop Relay(MMR) and adaptive modulation and coding(AMC) scheme. The result of NS-2 computer simulation shows that the throughput and transmission time are substantially improved by the proposed approach compared to the existing MBS system.

• The Journal of the Korea Contents Association
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• v.11 no.4
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• pp.101-111
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• 2011

Due to recent development in wireless communication technologies and mobile information devices, the services on ubiquitous computing technology without time and place restriction have been spotlighted. Moreover, the interest of the Wireless Sensor Networks (WSNs) and context-awareness technologies have largely been escalating and their technologies utilization is active in the various applications such as healthcare, farm management and so on. However, the direct adaption of the existing context-awareness technique to the WSN technology has several drawbacks as follows. First, such systems waste precious energy of sensor nodes, due to unnecessary data transmissions. Secondly, since the existing work was designed to support only specific applications, it is required to implement a new context-awareness application for a specific purpose. Therefore, we, in this paper, propose a new real-time monitoring system based on context-awareness in WSNs. Our system not only enhances energy efficiency by reducing data transmissions by doing context-awareness on a sensor node, but also is scalable in terms of supporting new context-awareness functionalities through modularization.

• Journal of Internet Computing and Services
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• v.13 no.3
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• pp.23-30
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• 2012

In order to show the gap between theory and practice, this paper first gives some experimental results for theoretical and real neighbor sets on a test-bed sensor network. The results prove that existing management protocols (e.g., duty-cycling, routing or aggregation) based on the theoretical communication radius cannot achieve their original goal, efficiency. In this paper, we present a practical duty-cycling mechanism based on the real neighbor set, allowing for energy-efficiency. It also guarantees to suppress duplicated transmissions of sensing values with similarity within a specific threshold in each zone (i.e., a portion of intended divided network). Simulation results performed with a set of real sensor data show that our mechanism increases the network life time while guaranteeing the transmission of necessary sensing values.

• Journal of Broadcast Engineering
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• v.14 no.2
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• pp.189-196
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• 2009

We propose a hybrid broadcast scheduling based on a combination of periodic and on-demand data scheduling methods for mobile data broadcasting in convergence networks from communication and broadcasting. We consider an environment in which the forward channel is for data broadcasting and the reverse channel is for sending data requests via cellular phones, WLAN, WiBro, etc. Collecting statistics of requests from clients, the server partitions the data items into hot-item and cold-item sets. Hot items are sent based on a push-based scheduling. An on-demand scheduling method is applied to cold items. Performance evaluation from simulations shows that our proposed scheduling algorithm yields small response time with high successful response ratio.