• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.7
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• pp.1-8
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• 2011

Vehicular Ad-hoc Network (VANET) is a special form of Mobile Ad-hoc Network designed to provide communications among nearby vehicles without communications infrastructure. Some characteristics in VANET environment such as high mobility, dynamic topology and selfishness of nodes can cause degradation of network quality. In this paper, we propose an adaptive incentive/topology control scheme to improve network quality in VANET by stimulating real time data forwarding and reporting changes of network topology. In the proposed scheme, an incentive suggested by the source node is updated in real time simultaneously with data transmission to stimulate real time data forwarding. In addition, when the order of the nodes in the path is changed, nodes which report the changes of network topology will get an additional incentive. By computer simulation, it is shown that the proposed incentive/topology control scheme outperforms the conventional schemes with respect to data delivery time and data delivery ratio.

• Journal of Digital Convergence
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• v.15 no.8
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• pp.45-58
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• 2017

The international freight forwarders in South Korea currently have fierce competition. However, there are still a very small number of studies Korea locally and globally on the service quality of international freight forwarding industry. This study aims to extract international freight forwarders' service quality factors reflecting the characteristics of freight forwarding industry. Measures of service quality have been selected after literature review and interviews, and then surveys have been conducted on exporters and importers in Korea. The collected data has been analyzed using the exploratory factor analysis. As a result, two service quality factors of international freight forwarders have been extracted: operation characteristics factor defined as accuracy, speediness timeliness and stability, and customer orientation factor defined as professionalism and empathy. An important contribution of this study is that it presents the service quality factors reflecting the characteristics of freight forwarding industry unlike precedent studies. A future research topic is to find out which of the two service quality factors influences more on customer loyalty.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5B
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• pp.378-389
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• 2006

An IP address lookup scheme has become a critical issue increasingly for high-speed networking techniques due to the advent of IPv6 based on 128bit. In this paper, a novel global IPv6 unicast address lookup scheme is proposed for next generation internet routers. The proposed scheme perform a variable multiple hashing based on prefix grouping. Accordingly, it should not only minimize overflows with the proper number of memory modules, but also reduce a memory size required to organize forwarding tables. It has the fast building and searching mechanisms for forwarding tables during only a single memory access. Besides, it is easy to update forwarding tables incrementally. In the simulation using CERNET routing data as a 6bone test phase, we compared the proposed scheme with a similar scheme using a uniform multiple hashing. As a result, we verified that the number of overflows is reduced by 50% and the size of memory for forwarding tables is shrunken by 15% with 8 tables.

• Journal of KIISE:Information Networking
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• v.33 no.2
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• pp.149-155
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• 2006

Existing routing protocols for mobile ad hoc networks (MANETs) have assumed that all nodes voluntarily participate in forwarding others' packets. In the case when a MANET consists of nodes belonging to multiple organizations, mobile nodes may deliberately avoid packet forwarding to save their own energy, resulting in network performance degradation. In this paper, to make nodes volunteer in packet forwarding, a credit payment scheme called Protocol-Independent Fairness Algorithm (PIFA) is proposed. PIFA can be utilized irrespective of the type of basic routing protocols, while previous methods are compatible only with source routing mechanisms like DSR. According to simulation results, we can know that PIFA can prevent network performance degradation by inducing selfish nodes to participate in packet forwarding.

• The KIPS Transactions:PartC
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• v.17C no.1
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• pp.109-118
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• 2010

Proxy mobile IPv6 (PMIPv6) protocol is a network-based mobility management protocol to support mobility for IPv6 nodes without host involvement. In PMIPv6, the Mobile Access Gateway (MAG) incurs a high signaling cost to update the location of a mobile node to the remote Local Mobility Anchor (LMA) if it moves frequently. This increases network overhead on the LMA, wastes network resources, and lengthens the delay time. Therefore, we propose a new mobility management scheme for minimizing signaling cost using the pointer forwarding. Our proposal can reduce signaling costs by registration with the neighbor MAG instead of the remote LMA using the pointer forwarding. The cost analysis using imbedded Markov chain presented in this paper shows that our proposal can achieve performance superior that of PMIPv6 scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12B
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• pp.1075-1082
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• 2008

A greedy forwarding algorithm is one of the most suitable solutions for routing in vehicular ad-hoc networks. Compared to conventional routing protocols for mobile ad-hoc networks, greedy forwarding based routing protocols maintain only local information of neighbors instead of per-destination routing entries, and thus they show better performance in highly-mobile vehicular ad-hoc networks. With greedy forwarding, each node learns its geographical position and periodically broadcasts a beacon message including its position information. Based on the position information, each node selects a neighbor node located closest to the destination node as the next forwarder. One of the most serious problems in greedy forwarding is the lost link problem due to the mobility of nodes. In this paper, we propose a new algorithm to reduce the lost link problem. The proposed algorithm aims to find an efficient and stable routing path by taking account of the position of neighbors and the last beacon reception time. Our simulation results show that the proposed algorithm outperforms the legacy greedy algorithm and its variants.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.745-759
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• 2011

In this paper, we propose the global handover mechanism that is able to provide the unlimited range of next-generation multimedia mobile services in an integrated environment. This mechanism consists of a multicast source based forwarding scheme and a global session management scheme. Global session management scheme provides LMA session information management, global mobility and route optimization. Multicast source based forwarding scheme delivers data between previously attached LMA and newly attached LMA without packet loss. In addition, this scheme removes the redundancy of buffered data. We present a performance evaluation and features analysis by the simulations using the ns-2. Global session management scheme has a less handover latency, propagation delay and signaling cost than the conventional methods. Multicast source based forwarding scheme can deliver buffer data without loss and it has less buffer size than conventional method.

• Journal of Internet Computing and Services
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• v.15 no.2
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• pp.9-18
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• 2014

The sensors attached on/in a person are moved since human body frequency changes their activity, therefore in wireless body area networks, nodal mobility and non-line-of-sight condition will impact on performance of networks such as energy efficiency and reliable communication. We then proposed schemes which study on forwarding decisions against frequent change of topology and channel conditions to increase reliable connections and improve energy efficiency. In this work, we control the size of packets, forwarding rate based on ratio of input links and output links at each node. We also robust the network topology by extending the peer to peer IEEE 802.15.4-based. The adaptive topology from chain-based to grid-based can optimal our schemes. The simulation shows that these approaches are not only extending network lifetime to 48.2 percent but also increase around 6.08 percent the packet delivery ratio. The "hot spots" problem is also resolved with this approach.

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.97-106
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• 2005

Generally, network QoS is determined by timeliness, bandwidth, and reliability, As IT technologies are growing day by day, the bandwidth and reliability factors are expected to be able to satisfy user's requirements. The timeliness factor, however, has not fully met user's requirements yet. In this paper, we propose a packet forwarding scheme named POSIA (Packet forwarding Scheme based on Interworking Architecture) that can provide quite a good QoS (quality of service) by minimizing processing time which is the major part of the timeliness factor. Based on path and resource reservation mechanism, the proposed POSIA makes routers on the packet forwarding path synchronize with each other and then forward packets, The POSIA has been verified to outperform the existing MPLS packet forwarding scheme through computer simulations using OPNET.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2459-2464
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• 2009

In sensor network there are no nodes or servers that are exclusively responsible for packet forwarding and routing. Instead, sensor nodes participating in network communications perform these activities. Thus, they are vulnerable to the alteration and forgery of message in the process of packet forwarding and routing. To solve this problem, a security to ensure authentication and integrity of routing and forwarding messages should be required. To do this, we propose the hash chain-based digital signature model where it takes less time to compute in generating and verifying the digital signature model, unlike he public key-based digital signature model, and verify if this model is proper by comparing computation times between tow models.