• Journal of Korea Multimedia Society
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• v.16 no.2
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• pp.180-189
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• 2013

The SMART Highway project combines road construction with advanced technology and vehicle telecommunications. Its expected outcome is a world-leading intelligent road that is green, fast, and comfortable. A vehicular ad-hoc network(VANET) is the core technology of the SMART Highway, whose transport operation is based on road vehicles. The VANET is a next-generation networking technology that enables wireless communication between vehicles or between vehicles and a road side unit(RSU). In the VANET system, a vehicle accident is likely to cause a serious disaster. Therefore, some information on safety is essential to serve as the key exchange protocol for communication between vehicles. However, the key exchange scheme of the general network proposed for a fast-moving communication environment is unsuitable for vehicles. In this paper, communication between multiple vehicles more efficient and secure key exchange at the vehicle certification by signcryption is proposed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10B
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• pp.865-875
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• 2008

In this paper, we propose a reliable multicast scheme for the tactical wireless ad hoc network where the members share the situation and operation data. Our scheme consists of two phases to guarantee the reliability. During the dissemination phase, we utilizes an epidemic approach similar to gossip-based ad hoc routing. Then the group members interchange the message reception state information periodically so that they are able to recover missing packets from the other members. We evaluate the performance of our scheme through extensive simulations using the network simulator in comparison with other existing reliable multicast schemes in mobile ad hoc network. Our scheme shows higher packet delivery ratio regardless of the mobility and imposes much lower control overhead to the non-group members compared with the existing schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6A
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• pp.577-584
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• 2010

In this paper, a cooperative MAC protocol that is reliable over bad wireless channel environments and thus can enhance the system performance much more is proposed. Its performance is evaluated with the computer simulation. The system throughput and average waiting delay are used as performance measures. According to numerical results, the proposed MAC protocol provides better system throughput by 24% than the traditional rDCF scheme. From the average waiting delay point of view, when the number of terminals is small, the proposed MAC protocol has the better performance in an average view-point than the rDCF scheme. However, when the number of terminals is large, the proposed MAC protocol provides a little worse performance than the rDCF scheme. That is because, when the number of terminals is large, the dominant factor affecting the system performance is channel contention procedure, which results in lots of collisions. However, if the queuing delays in the waiting buffers are included for calculating the average waiting delay, then the total system delay will be smaller than the rDCF scheme.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.8
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• pp.1098-1104
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• 2011

Data communications networks at sea can be modelled by multi-layered networks with traditional carriers (RF, satellites), and BWA (wireless LAN, WiBro, LTE), which partially makes it possible the high speed communication services (WWW, VoIP) at sea. In this paper, a novel routing scheme (CPR) is proposed which selects an optimal carrier for each hop in routes based on carrier preferences (CP). The carrier preferences are measured proactively depending on the feasibility of transmission characteristics (transmission rate, cost, and latency time) of the carriers for each application. Performance was compared with that of the OMH-MW (Optimal Medium per Hop based on Max-Win) routing scheme.

• Journal of Advanced Navigation Technology
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• v.14 no.4
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• pp.495-503
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• 2010

The clustering is an important mechanism thai provides information for mobile nodes efficiently and improves the processing capacity for routing and the allocation of bandwidth. This paper proposes a clustering scheme based on the fuzzy relevance degree to solve problems such as node distribution found in the dynamic property due to mobility and flat structure and to enhance the routing performance. The proposed scheme uses the fuzzy relevance degree, ${\alpha}$, to select the cluster head for clustering in FSV (Fuzzy State Viewing) structure. The fuzzy relevance ${\alpha}$ plays the role in CH selection that processes the clustering in FSV. The proposed clustering scheme is used to solve problems found in existing 1-hop and 2-hop clustering schemes. NS-2 simulator is used to verify the performance of the proposed scheme by simulation. In the simulation the proposed scheme is compared with schemes such as Lowest-ID, MOBIC, and SCA. The simulation result showed that the proposed scheme has better performance than the other existing compared schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.12
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• pp.817-821
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• 2014

As users generate lots of contents independently of time and places anytime and anywhere together with a rapid development of mobile wireless communication technologies and an explosive dissemination of smart devices, content centric networking (CCN) has emerged as a new networking architecture. However, as CCN is based on one to one message exchanges, it is not appropriate for ad hoc network environment that has frequent network topology changes, which results in high control overhead and low transmission throughput. So, this paper proposes the new content sharing methods using group interest messages in CCN ad hoc environment. It is shown from the simulation that the proposed method can provide low control overhead and high transmission throughput.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.69-78
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• 2009

DV-Hop algorithm is not accurate in estimating geographic location of nodes because the average size for one hop is calculated without considering of the positioning error. In this paper, a novel algorithm based on DV-Hop algorithm is proposed for the approach to estimating the average size of a hop by minimizing anchor's positioning error using Least Square Error with other anchors. Moreover, unknown nodes have their own average size for one hop to compensate for the location error of the unknown occurring as more than the minimum hop counts to the distance. Simulation results show that the proposed algorithm has more accuracy than DV-Hop has in positioning.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.52-59
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• 2008

Most pier performance analysis results for ad-hoc routing protocols have been based upon the model which each node in the network moves independently without restriction. In most real environments, however, it is very common for a group or multiple groups to move under the direction of group leader or group leaders instead of each node's independent movement. This paper presents the performance analysis of routing protocols for mobile ad-hoc network under group mobility environment. The comparative simulations have been made between a table-driven protocol, DSDV, and two on-demand protocols, AODV and DSR, under a group mobility model, RPGM, which is suitable for the practical applications such as military tactical operation. Multiple group movements are also included. The results show that the protocol performances for single group movement are very similar to node independent movement case. However some differences have been observed by varying pause time and connectivity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.2
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• pp.155-164
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• 2013

Two design techniques for more accurate and more convenient hybrid positioning system with visible light communication (VLC) and ad-hoc wireless network infrastructure are proposed, in order to overcome the problems of high estimation error, high cost, and limited service range of the conventional positioning techniques. First method is based on a non-carrier VLC based hybrid positioning technique for applications involving of low data rate optical sensing and narrow-range visible light reception from transmitter, and long-range positioning. The second method uses a 4 MHz carrier VLC-based hybrid positioning technique for a high data rate optical sensing and wide-range visible light receiving from transmitter, and mid-range positioning applications. In indoor environments with obstacles where there are long-range 7731.4cm and mid-range 2368cm distances between an observer and a target respectively, the hybrid positioning developed with two design techniques are tested, and the proposed system is verified and analyzed in this paper.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.4
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• pp.371-380
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• 2020

Video is principal information that facilitates commander's immediate command decision. Due to fading characteristics of radio link, however, it is difficult to stably transmit video in a multi-hop wireless environment. In this paper, we propose a MANET structure composed of a link adaptive routing protocol and a TDMA MAC protocol to stably transmit video traffic in a ultra-narrowband video streaming network. The routing protocol can adapt to link state change and select a stable route. The TDMA protocol enables collision-free video transmission to a destination using multi-hop dynamic resource allocation. As a result of simulation, the proposed MANET structure shows better video transmission performance than proposed MANET structure without link quality adaption, AODV with CSMA/CA, and OLSR with CSMA/CA structures.