• Journal of Communications and Networks
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• v.13 no.4
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• pp.385-392
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• 2011

A loop can take place in the process of managing tree topology for mobility management of mobile nodes in infrastructure-based mobile ad hoc networks. The formation of a loop degrades an effective bandwidth of the wireless network by passing an identical message repeatedly within the same loop. Therefore, the loop should be resolved to revert the system back to the normal state. In this paper, we propose a simple and novel mechanism that detects and resolves a loop quickly by tracking the depth of trees. The mobility management approach that employs the loop resolution method is evaluated comparatively with the original tree-based one and the hybrid one. It is shown that the proposed approach far outperforms the other approaches, and it is robust against the rapid changes in network topology.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.92-101
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• 2012

Security support is a significant factor in ad hoc networks. Especially in dynamic topologies, key agreement with private key updating is essential in providing a secure system. And it is also necessary to protect the identities of individual nodes in wireless environments to avoid personal privacy problems. However, many of the existing key agreement schemes for ad hoc networks do not consider these issues concurrently. This paper proposes an anonymous ID-based private key update scheme and a key agreement scheme for mobile ad hoc networks. We also suggest a method of rekeying between different domains using service-coordinators. These schemes are secure against various attacks and are suitable for service-oriented mobile ad hoc networks.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.4
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• pp.87-97
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• 2009

A Mobile Ad hoc Network (MANET) is characterized by multi-hop wireless connectivity, frequently changing network topology with mobile nodes and the efficiency of the dynamic routing protocol plays an important role in the performance of the network. In this paper, the performance of five routing protocols for MANET is compared by using OPNET modeler: AODV, DSR, GRP, OLSR and TORA. The various performance metrics are examined, such as packet delivery ratio, end-to-end delay and routing overhead with varying data traffic, number of nodes and mobility. In our simulation results, OLSR shows the best performance in terms of data delivery ratio in static networks, while AODV has the best performance in mobile networks with moderate data traffic. When comparing proactive protocols (OLSR, GRP) and reactive protocols (AODV, DSR) with varying data traffic in the static networks, proactive protocols consistently presents almost constant overhead while the reactive protocols show a sharp increase to some extent. When comparing each of proactive protocols in static and mobile networks, OLSR is better than GRP in the delivery ratio while overhead is more. As for reactive protocols, DSR outperforms AODV under the moderate data traffic in static networks because it exploits caching aggressively and maintains multiple routes per destination. However, this advantage turns into disadvantage in high mobility networks since the chance of the cached routes becoming stale increases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7B
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• pp.1009-1017
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• 2010

Offering of different attractive opportunities by different wireless technologies trends the convergence of heterogeneous networks for the future wireless communication system. To make a seamless handover among the heterogeneous networks, the optimization of the power consumption, and optimal selection of interface are the challenging issues. The access of multi interfaces simultaneously reduces the handover latency and data loss in heterogeneous handover. The mobile node (MN) maintains one interface connection while other interface is used for handover process. However, it causes much battery power consumption. In this paper we propose an efficient interface selection scheme including interface selection algorithms, interface selection procedures considering battery power consumption and user mobility with other existing parameters for overlaying networks. We also propose a priority based network selection scheme according to the service types. MN‘s battery power level, provision of QoS/QoE and our proposed priority parameters are considered as more important parameters for our interface selection algorithm. The performances of the proposed scheme are verified using numerical analysis.

• Electronics and Telecommunications Trends
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• v.33 no.5
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• pp.24-32
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• 2018

With the advent of new convergence services, the requirements of 5G mobile communication systems are being newly derived. The 5G mobile communication system has been evolving to solve requirements that cannot be satisfied with existing 4G mobile communication systems, such as a high user experience transmission rate, short transmission delay, and high connection density. The evolution of a 5G mobile communication system to meet the new requirements is expected to be dominated by the UDN environment in which a number of small cells are concentrated. The 5G wireless backhaul system, which has advantages in terms of initial installation and operation cost, is expected to be an indispensable choice for connecting many small cells and core networks. This paper therefore looks at the frequency band characteristics and requirements applicable to 5G wireless backhaul systems that can accommodate new situations, and introduces key related technologies that can satisfy the 5G wireless backhaul requirements.. In addition, we describe the research and development trends of a 5G wireless backhaul system that is currently under development.

• Journal of Communications and Networks
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• v.17 no.2
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• pp.100-109
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• 2015

Mobile phone carriers face challenges from three synergistic dimensions: Wireless, social, and mobile. Despite significant advances that have been made about social networks and human mobility, respectively, our knowledge about the interplay between two layers remains largely limited, partly due to the difficulty in obtaining large-scale datasets that could offer at the same time social and mobile information across a substantial population over an extended period of time. In this paper, we take advantage of a massive, longitudinal mobile phone dataset that consists of human mobility and social network information simultaneously, allowing us to explore the impact of human mobility patterns on the underlying social network. We find that human mobility plays an important role in shaping both local and global structural properties of social network. In contrast to the lack of scale in social networks and human movements, we discovered a characteristic distance in physical space between 10 and 20 km that impacts both local clustering and modular structure in social network. We also find a surprising distinction in trajectory overlap that segments social ties into two categories. Our results are of fundamental relevance to quantitative studies of human behavior, and could serve as the basis of anchoring potential theoretical models of human behavior and building and developing new applications using social and mobile technologies.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.6
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• pp.85-92
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• 2010

In this paper, we propose a Clustering-based Cooperative Routing using OFDM (CCRO) for supporting transmission efficiency in mobile wireless sensor networks. The main features and contributions of the proposed method are as follows. First, the clustering method which uses the location information of nodes as underlying infrastructure for supporting stable transmission services efficiently is used. Second, cluster-based cooperative data transmission method is used for improving data transmission and reliability services. Third, OFDM based data transmission method is used for improving data transmission ratio with channel efficiency. Fourth, we consider realistic approach in the view points of the mobile ad-hoc wireless sensor networks while conventional methods just consider fixed sensor network environments. The performance evaluation of the proposed method is performed via simulation using OPNET and theoretical analysis. The results of performance evaluation show improvement of transmission efficiency.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.141-150
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• 2011

In this paper, we propose a Cross-Layer Cooperative Routing(CLCR) architecture to support transmission efficiency in mobile wireless sensor networks. The main features and contributions of the proposed architecture and method are as follows. First, the clustering which uses the location information of nodes is utilized as infrastructure. Second, a cross-layer strategy which uses the technologies of network layer, MAC layer, physical layer together to support transmission efficiency and channel efficiency for cooperative-aided routing and transmission. Third, we consider realistic approach in the view points of the mobile ad-hoc wireless sensor networks while conventional methods just consider fixed sensor network environments. The performance evaluation of the proposed method is performed via simulation using OPNET and theoretical analysis. The results of performance evaluation of the proposed CLCR show improvement of transmission efficiency by the proposed CLCR.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.3
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• pp.943-961
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• 2020

With the advent of IoT technology and Big Data computing, the importance of WSNs (Wireless Sensor Networks) has been on the rise. For energy-efficient and collection-efficient delivery of any sensed data, lots of novel wireless medium access control (MAC) protocols have been proposed and these MAC schemes are the basis of many IoT systems that leads the upcoming fourth industrial revolution. WSNs play a very important role in collecting Big Data from various IoT sensors. Also, due to the limited amount of battery driving the sensors, energy-saving MAC technologies have been recently studied. In addition, as new IoT technologies for Big Data computing emerge to meet different needs, both sensors and sinks need to be mobile. To guarantee stability of WSNs with dynamic topologies as well as frequent physical changes, the existing MAC schemes must be tuned for better adapting to the new WSN environment which includes energy-efficiency and collection-efficiency of sensors, coverage of WSNs and data collecting methods of sinks. To address these issues, in this paper, a self-organization scheme for mobile sensor networks with mobile multiple sinks has been proposed and verified to adapt both mobile sensors and multiple sinks to 3-dimensional group management MAC protocol. Performance evaluations show that the proposed scheme outperforms the previous schemes in terms of the various usage cases. Therefore, the proposed self-organization scheme might be adaptable for various computing and networking environments with big data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7B
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• pp.628-640
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• 2004

The demand for next generation networks can be condensed into always-best-connected, ubiquitous, mobile, all-lP, and converged networks. IPv6 has been introduced for all-IP ubiquitous communications, and vehicles are coming to represent an important communication platform. In this paper. we propose various resource management schemes for in-vehicle mobile networks, which are adaptive to different hardware configurations. We focus on power and wireless bandwidth since they are critical resources for mobile communications. Based on the mobility characteristics of in-vehicle networks, we propose vehicle-aware power saving schemes. The main idea behind these power saving schemes is to adjust mobile router (MR) advertisement interval and binding lifetime. In addition, according to different wireless environments, we propose adaptive bandwidth management schemes using multihoming: best-connected MR selection based on location, and high-data-rate MR selection based on priority By mathematical analysis, it is shown that our schemes save power prominently for both the dormant nodes and active nodes. In addition, simulation results show that proposed multiple mobile router architecture outperforms previous simple redundant router architecture in preserving session and providing sufficient bandwidth.