• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.6
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• pp.195-207
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• 2017

Since the smart phone was first introduced, the amount of mobile traffic has increased explosively. The OTT service with personal broadcasting and TV contents and the number of users have been increased in wired network, and there are needs to expand the OTT service to mobile network. In the case of the OTT service in mobile network, the relative small and finite resource may cause the overload of the network due to the massive and high transfer rate. In this paper, we consider a future situation of the OTT user services in the cellular network and propose a novel D2D communication scheme for location-based OTT service, which can reduce and distribute the amount of video traffics. To effectively handle the traffic of OTT services, we propose D2DS and LCS functional blocks in EPC network, which can provide location-based service and D2D management. And, we suggest additional procedures for the location-based service of both content provider and contents receiver UEs with the operation of the proposed D2DS and LCS function block.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.39-45
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• 2011

In this paper, we propose an efficient multichannel MAC protocol with idle nodes assistance to avoid the multi-channel hidden terminal problem in cognitive radio ad hoc network and further to improve the performance of the network. The proposed MAC protocol can be applied to the cognitive radio adhoc network where every node is equipped with the single transceiver and one common control channel exists for control message negotiation. In the proposed protocol, the idle nodes available in the neighbour of communication nodes are utilized because the idle nodes have the information about the channels being utilized in their transmission range. Whenever the nodes are negotiating for the channel, idle nodes can help the transmitting and receiving nodes to select the free data channel for data transfer. With the proposed scheme, we can minimize the hidden terminal problem and decrease the collision between the secondary users when selecting the channel for data transfer. As a result, the performance of the network is increased.

• Journal of Digital Contents Society
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• v.15 no.1
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• pp.1-9
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• 2014

Delay-Tolerant Network (DTN) is an asynchronous networking technology that has been deployed for the networking environment in which steady communication paths are not available, and therefore it stores receiving data in a data storage and forward them only when the communication links are established. DTN can be applied to sensor networks and mobile ad-hoc network (MANET) as well as space communication that supports data transmissions among satellites. In DTN networking environments, it is very important to secure a scheme that has relatively low routing overhead and high reliability, so that it can enhance the overall routing speed and performance. In order for achieving efficient data transmissions among the nodes that have comparatively periodic moving patterns, this paper proposes a time information based DTN routing scheme which is able to predict routing paths. From the simulation results using Omnet++ simulation tools, it has been verified that the proposed time information based DTN routing algorithm shows satisfied levels of routing speed and routing reliability even with lower routing overheads.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.10
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• pp.801-807
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• 2013

WSN consists of hundreds to thousands of sensor nodes. In order to solve the problem of energy consumption imbalance cluster head is reelected in every round, while node authentication scheme is utilized for secure communication. However, re-clustering increases the overhead of sensor nodes and during the node authentication phase the frequent AREQ/AREP message exchange also increases the overhead. Therefore, a secure and energy efficient protocol, by which overhead of sensor nodes is reduced and long time communication is achieved, is required for wireless sensor network. In this paper, an energy efficient and reliable IDE-LEACH protocol for WSN is proposed. The proposed protocol is prolongs networks lifetime about average 20% compared to the LEACH-based protocols and all attending nodes in communication form BS authentication consisted of trusted nodes.

• Journal of Communications and Networks
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• v.15 no.2
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• pp.142-152
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• 2013

The network mobility basic support (NEMO BS) protocol has been investigated to provide Internet connectivity for a group of nodes, which is suitable for intelligent transportation systems (ITS) applications. NEMO BS often increases the traffic load and handover latency because it is designed on the basis of mobile Internet protocol version 6 (MIPv6). Therefore, schemes combining proxy MIPv6 with NEMO (P-NEMO) have emerged to solve these problems. However, these schemes still suffer from packet loss and long handover latency during handover. Fast P-NEMO (FP-NEMO) has emerged to prevent these problems. Although the FP-NEMO accelerates handover, it can cause a serious tunneling burden between the mobile access gateways (MAGs) during handover. This problem becomes more critical as the traffic between the MAGs increases. Therefore, we propose a scheme for designing an improved FP-NEMO (IFP-NEMO) to eliminate the tunneling burden by registering a new address in advance. When the registration is completed before the layer 2 handover, the packets are forwarded to the new MAG directly and thereby the IFP-NEMO avoids the use of the tunnel between the MAGs during handover. For the evaluation of the performance of the IFP-NEMO compared with the FP-NEMO, we develop an analytical framework for fast handovers on the basis of P-NEMO. Finally, we demonstrate that the IFP-NEMO outperforms the FP-NEMO through numerical results.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.3
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• pp.177-183
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• 2020

Steganography uses digital images as a medium for sending secret messages over insecure networks. There is also a least significant bit(LSB) that is a popular method of embedding secret messages in digital images. The goal of steganography is to securely and flawlessly transmit secret messages using stego media over a communication channel. There is a need for a method to improve resistance to reduce the risk of exposure to third parties. To safely hide secret messages, I propose new algorithms that go through crossing, encryption, chaos and concealment steps. After separating Hangul syllables into choseong, jungseong and jongseong, the bitwised message information is encrypted. After applying the logistic map, bitwised information is reconstructed using the position of the chaotic sequence. The secret message is inserted into the randomly selected RGB channel. PSNR and SSIM were used to confirm the effectiveness of the applied results. It was confirmed as 44.392(dB) and 0.9884, respectively.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.10
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• pp.550-560
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• 2002

External sort on cluster computers requires not only fast internal sorting computation but also careful scheduling of disk input and output and interprocessor communication through networks. This is because the overall time for the execution is determined by reflecting the times for all the jobs involved, and the portion for interprocessor communication and disk I/O operations is significant. In this paper, we improve the sorting performance (sorting throughput) on a cluster of PCs with a low-speed network by developing a new algorithm that enables even distribution of load among processors, and optimizes the disk read and write operations with other computation/communication activities during the sort. Experimental results support the effectiveness of the algorithm. We observe the algorithm reduces the sort time by 45% compared to the previous NOW-sort[1], and provides more scalability in the expansion of the computing nodes of the cluster as well.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.11
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• pp.1726-1734
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• 1993

This paper propose a survivable communication network design process using node degree that augments the usual traffic flow and cost analyses with previously ignored topological survivability and computing time considerations. At first, decide a initial topology, and then measure a throughput of network. If the throughput is smaller than the required traffic, add edge to the optimum place by using minimum node degree and link distance. Otherwise, drop useless edge by using maximum node degree, link distance and link utilization. This process is repeated until throughput equals to the required traffics. This Process designs a survivable communication network with the minimized cost and computing time and usual traffic flow. The design proceses that minimized computing time are freely select initial topology and easily design a large network. And these results of algorithm are compared with the Kris and Pramod's in order to analyses the perfmance of the designed network.

• Journal of Satellite, Information and Communications
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• v.5 no.1
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• pp.43-47
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• 2010

In future mobile networks, hybrid/integrated satellite and terrestrial systems will play an important role. Most of the mobile communication systems are focused on the terrestrial systems, in this case, compatibilities between the satellite and terrestrial systems are very important for efficiency of the systems. Terrestrial systems of all the 4G mobile communication adopted the adaptive modulation and coding (AMC) schemes for efficient usage of resources, and the updating interval of resource allocation in an order of msec. However, because of the long round trip delay of satellite systems, we cannot employ the same AMC scheme specified for the terrestrial system, and thus it cannot effectively counteract to short term fadings. In the paper, we propose the method to apply AMC to mobile satellite systems. In addition, in order to effectively counteract to short term fadings, we present the simulation results of the AMC combined with an interleaver.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.7
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• pp.1554-1560
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• 2015

802.11p WAVE is the next-generation wireless communication that can make Ad-hoc network communication possible for Vehicle-to-Vehicle. GBSR protocol, one of the 802.11p WAVE protocols, mainly focuses on improvements in networks that have a tendency to disconnect. However, it does not consider the transmission time and velocity of a packet thus, there is a disadvantage of there being a delay in the transmission velocity, in urgent situations like car accidents, emergency patients transportation and crimes. In this paper, we proposed A-GBSR protocol for transmission of a packet to mobile node which has a high speed through the improved beacon message and Adaptive Neighbor list Management that are considering of the GBSR protocol transmission velocity.