• Journal of Digital Contents Society
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• v.14 no.4
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• pp.429-437
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• 2013

Recently, wireless mesh network has been focused as a core technology for resolving the issues of shadow zone and distributed bypass route as it has broad service coverage as well as good scalability features. It, however, provides users with relatively lower QoS than infrastructure-based networks. In order for addressing this QoS issue and also enhancing the routing performance of mobile WiMax mesh network, this paper proposes a load sensing QoS routing (LSQR) scheme. In the proposed LSQR, each node figures out network congestion status and selects a bypass route accordingly. With this scheme, we can expect good load balancing effect by changing the routing paths from centralized links to distributed links under a heavy traffic condition. From the simulation results using NS-2, it has been verified that the LSQR shows lower packet loss rates and data transmission delays than the existing representative routing schemes.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1023-1026
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• 2005

In the ubiquitous computing environment, an intelligent vehicle is defined as a sensor node with a capability of intelligence and communication in a wire and wireless network space. To make it real, a lot of problems should be addressed in the aspect of vehicle mobility, in-vehicle communication, common service platform and the connection of heterogeneous networks to provide a driver with several intelligent information services beyond the time and space. In this paper, we present an intelligent information system for managing in-vehicle sensor network and a vehicle gateway for connecting the external networks. The in-vehicle sensor network connected with several sensor nodes is used to collect sensor data and control the vehicle based on CAN protocol. Each sensor node is equipped with a reusable modular node architecture, which contains a common CAN stack, a message manager and an event handler. The vehicle gateway makes vehicle control and diagnosis from a remote host possible by connecting the in-vehicle sensor network with an external network. Specifically, it gives an access to the external mobile communication network such as CDMA. Some experiments was made to find out how long it takes to communicate between a vehicle's intelligent information system and an external server in the various environment. The results show that the average response time amounts to 776ms at fixed place, 707ms at rural area and 910ms at urban area.

• Journal of KIISE:Information Networking
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• v.35 no.1
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• pp.34-45
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• 2008

In dynamic wireless sensor networks where sources and sinks are moving or are created/died, control overheads for route establishment are increased and thus become one of the major factors for energy consumption. This study introduces prefetching and pruning for Directed Diffusion to remove redundant control messages. Prefetching collects path information for each event with "AnyEvent" in advance and gives quick responses without further flooding of requests. Pruning accumulates history information from previous requests and replies, and then stops forwarding a request towards where the event does not exist. Simulation results with ns show that it is possible to build implicit and soft infrastructures within a Directed Diffusion system through these active collection and passive accumulation and they improve energy consumption more as control overhead goes higher.

• International Commerce and Information Review
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• v.12 no.3
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• pp.55-78
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• 2010

This study analyses recent development of digital contents industry. The purpose of this study is to show how the convergence phenomenon is occurring in the digital contents industry. Furthermore, this study examines the influence of digital convergence on the digital contents industry. The characteristics of the digital contents industry falls roughly into three features. To begin with, technical aspect of the industrial feature is that digitalized contents can be used in various digital devices, namely OSMU(One Source Multi Use). The second feature is related to protection of copyright against illegal file sharing and downloading. One final point is that platform for distribution channels has been universal by digital convergence. To sum up, the notable feature of digital contents industry is high value-added. Also, digital contents industry is composed of users, digital device, network, and universal contents. Users are the key component of digital contents industry, who is distinguished from consumers. Digital devices such as mobile phone, PDA can play all kinds of digital contents and make users communicate in two-ways. Portable devices also allow the users to consume digital contents at any place. Digital contents can be distributed by both wire and wireless networks. And most of transactions can be made through networks. There are three key issues about digital convergence. Entry barriers for market become lowered; the age of contents users is changed from old generation to young generation. And the form of contents devices is changing rapidly. Traditional contents field such as movie, music, broadcasting, publishing, animations are combined into one digital contents territory. As a result, this paper suggests that digital convergence phenomenon will be accelerating for the future. According to the result of this study, the advent of digital convergence and e-Commerce will have significant influence on trade of digital contents.

• The KIPS Transactions:PartB
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• v.8B no.5
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• pp.441-446
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• 2001

On global interconnectivity, the activation of real-time and worldwide contents will permeate and impact all aspects of day-to-day life well throughout this century. In managing contents and models, we too will see the impact of this rapidly changing environment. The real time availability of contents pertaining to a companys supply chain through means of the Internet and mobile networks(e.g., the IMT-2000) will necessitate a change in decision-making processes for effective management of contents and models. To increase the availability of many contents and models, a management system should have adaptive function in proving adequate content and model for companies. In the respect of management of contents and models, this paper discusses a production mechanism of meta-knowledge for effectively managing contents and models. Through two experimental analyses with the production mechanism, it is proven that the system enabling adaptive contents and models provision goes beyond existing ones in view of efficiency of management of contents and models in the wire and wireless networks.

• Journal of the Korea Society for Simulation
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• v.17 no.3
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• pp.1-8
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• 2008

It is essential to maintain constant QoS despite of cell overload or erroneous wireless link during transmission because QoS of a multimedia service may be severely degraded by small delay or packet loss. This paper deals with a cell selection method for supporting the QoS of multimedia services over heterogeneous networks. The proposed scheme is based on Fuzzy Multi-Criteria Decision Making (FMCDM), in which uncertain parameters such as user system preference, the communication cost and cell load, and the transmission delay are used in the decision process using the aggregation function in fuzzy set theory. In this scheme, errors in the evaluation parameters impose milder changes on the total evaluation value than in binary logics. Simulation is focused on the average delay and packet loss rate, and the simulation results show that our proposed method provides mobile terminals the optimal performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3747-3765
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• 2017

Existing authentication mechanisms in cellular mobile communication networks are realized in the upper layer by employing cryptographic techniques. Authentication data are broadcasted over the air in plaintext, enabling attackers to completely eavesdrop on the authentication and get some information about the shared secret key between legitimate nodes. Therefore, reusing the same secret key to authenticate several times results in the secret key's information leakage and high attacking rate. In this paper, we consider the most representative authentication mechanism, Authentication and Key Agreement (AKA), in cellular communication networks and propose an enhanced AKA scheme based on Physical Layer Authentication (AKA-PLA). Authentication responses generated by AKA are no longer transmitted in plaintext but masked by wireless channel characteristics, which are not available to adversaries, to generate physical layer authentication responses by a fault-tolerant hash method. The authenticator sets the threshold according to the authentication requirement and channel condition, further verifies the identity of the requester based on the matching result of the physical layer authentication responses. The performance analyses show that the proposed scheme can achieve lower false alarm rate and missing rate, which are a pair of contradictions, than traditional AKA. Besides, it is well compatible with AKA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10B
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• pp.891-899
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• 2006

Generally, a geographical area consists of many regions called cells in wireless networks. Each mobile host(MH) in a cell communicates with a base station(BS) located in the center of the cell. The BSs are connected to each other by a static wired network. Since users are expected to move around during communication sessions, one of the most important QoS factors is related to the handoff. But, the handoff could fail due to unavailability of sufficient bandwidth in the next cell. As the individual cell size gradually shrinks to accommodate increasing the number of MHs, the probability of successful handoffs can be dropped. In this paper, we suppose a bandwidth reservation method to guarantee MHs against connection failure in case of frequent handoffs. This method predicts the mobility based on the geographical information and assigns the bandwidth reservation in proportion to the speed of MHs' motion. As a result, we can expect more exact moving path of MH and to reduce the waste of bandwidth.

• Journal of Korean Society of Transportation
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• v.26 no.6
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• pp.93-101
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• 2008

With a spread of mobile devices, the growing trend of integrating wireless communications technologies into transportation systems is advanced. In particular, vehicular ad hoc networks (VANETs) enable vehicles to share traffic information that they have through intervehicle communications. This research focused on the design of an integrated transportation and communication simulation framework to build an environment that is more realistic than previous studies developed for studying VANETs. Developing a VANET-based information model, this research designed an integrated transportation and communication simulation framework in which these independent simulation tools not supporting High Level Architecture (HLA) were tightly coupled and finely synchronized. As a case study, a VANET-based traffic information system was demonstrated based on a real road network and real traffic data. The experiment results showed that the simulation framework was well integrated. The simulation framework designed in this study is expected to contribute to developing the environment to experiment a wide range of VANET applications.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1447-1453
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• 2014

Wireless Body Area Networks (WBAN), standardized as IEEE 802.15.6, enable digital devices on/around the human body to communicate with one another. WBAN is essentially a person's piconet consisting of a master (mobile) device and several slave devices, which follows his/her mobility pattern, and hence, occasionally collides with another piconet as people meet or pass by. As such, a mechanism to detect collision and avoid interference is needed for intra-piconet communications. In this paper, we focus on this notorious problem of piconet collision and propose Distributed Time Division Piconet Coexistence (DTDPC) using local time offset exchange as a simple, attractive solution. The proposed DTDPC provides different level of services for various applications. Besides our simulation results have shown that the proposed solution outperforms the conventional CSMA protocols.