Seunghae Kim

An Energy Efficient Cluster Formation and Maintenance Scheme for Wireless Sensor Networks

Nowadays, wireless sensor networks (WSNs) comprise a tremendously growing infrastructure for monitoring the physical or environmental conditions of objects. WSNs pose challenges to mitigating energy dissipation by constructing a reliable and energy saving network. In this paper, we propose a novel network construction and routing method by defining three different duties for sensor nodes, that is, node gateways, cluster heads, and cluster members, and then by applying a hierarchical structure from the sink to the normal sensing nodes. This method provides an efficient rationale to support the maximum coverage, to recover missing data with node mobility, and to reduce overall energy dissipation. All this should lengthen the lifetime of the network significantly.

K-GENI testbed deployment and federated meta operations experiment over GENI and KREONET

The classical Internet has confronted many drawbacks in terms of network security, scalability, and performance, although it has strongly influenced the development and evolution of diverse network technologies, applications, and services. Therefore, new innovative research on the Future Internet has been performed to resolve the inherent weaknesses of the traditional Internet, which, in turn, requires new at-scale network testbeds and research infrastructure for large-scale experiments. In this context, K-GENI has been developed as an international programmable Future Internet testbed in the GENI spiral-2 program, and it has been operational between the USA (GENI) and Korea (KREONET) since 2010. The K-GENI testbed and the related collaborative efforts will be introduced with two major topics in this paper: (1) the design and deployment of the K-GENI testbed and (2) the federated meta operations between the K-GENI and GENI testbeds. Regarding the second topic in particular, we will describe how meta operations are federated across K-GENI between GMOC (GENI Meta Operations Center) and DvNOC (Distributed virtual Network Operations Center on KREONET/K-GENI), which is the first trial of an international experiment on the federated network operations over GENI.

Lightweight Key Renewals for Clustered Sensor Networks

In sensor networks, sensors are likely to be c aptured by attackers because they are usually deployed in an unprotected or even a hostile environment . If an adversarial compromises a sensor, he/she uses the keys from the compromised sensor to uncover the keys of others sensors. Therefore, it is very important to renew the keys of sensors in a proactive or reactive manner. Even though many group key renewal schemes have been proposed, they have some security flaws. First, they employ a single group key in a cluster so that the compromise of one sensor discloses the group key . Second, they evict the compromised nodes by updating the compromised keys with non-compromised keys. This eviction scheme is useless when the non-compromised keys are exhausted due to the increase of compromised nodes. In this paper, we propose a lightweight key renewal scheme , which evicts the compromised nodes clearly by reforming clusters excluding compromised nodes. Besides, in a cluster, each member employs a pairwise key for communication with its CH (Cluster Head) so that our scheme is tolerable against sensor compromise. Our simulation results prove that the proposed scheme is more tolerable against the compromise of sensors and it is more energy-saving than the group key renewal schemes.

Aggregation management design for user-defined network infrastructure.

Recently, OpenFlow and FlowVisor are the most promising architecture components of the software-defined networks (SDNs). The evolution of these components brought the revolution of utilizing network elements for the shared and virtual network infrastructure, however from the aspects of production networks, it still lacks of some key component. For example, policy-based services provisioning for user-defined requirement is an indispensable part. Hence, innovative aggregation management design for virtual network management system framework must be developed and tested. This paper describes an initial design to user-defined network infrastructure in order to make it capable of running policy-based engineering related experiments. We developed the framework regarding the real use cases upon the shared and virtual network in KREONET infrastructure. Moreover, we also presented perflow-user-defined specifications which include max rate limiter and dynamic priority assignment strategy to enhance the validation performance of our system for production networks.

A method for enhancing end-to-end transfer efficiency via performance tuning factors on dedicated circuit networks with a public cloud platform

There has been a great deal of recent research interest regarding the storage and utilization of big data via remote cloud platforms. The efficiency of large data transfers from remote cloud platforms is a critical issue, and dedicated networks are used for data transfer. To resolve the data transfer efficiency issue, it is necessary to tune the L2-related performance items in the transport equipment and to regulate performance factors, such as window size, between IP layer servers, during the configuration of an end-to-end research network. It is also necessary to tune factor values related to performance items in transport equipment. System level kernel parameter tuning is also needed and results in improved throughput. Here, we measure throughput according to L2-related tuning factors and IP levels, including kernel parameter turning, and present an analysis of the measurement results. The experimental results show that end-to-end servers with tuned factors, in addition to system level kernel parameter tuning, can effectively utilize the available bandwidth.

A revised cache allocation algorithm for VoD multicast service

The Internet is replacing the traditional telephone network as the ubiquitous network infrastructure. Internet customers are increasing at an exponential rate and will continue to increase in the near future. Among the various Internet services, IPTV VoD (Video on Demand) service is expected to be one of the most popular services. In general, for deploying streamed video service, it is likely to use proxy by locating it nearby end-users. The use of proxy in on-demand media streaming service can help reduce the server streaming load and reduce the startup delay of media playback due to swift retrieval of beginning portion of media. We had proposed a cache allocation scheme for server-proxy media streaming environment by utilizing the advantage of threshold-based multicast mechanism. However it suffer from a little radical change of threshold value. In this paper, enhanced multicast-based server-proxy on-demand media streaming algorithm to IPTV VoD services is presented from the storage, caching size and bandwidth requirement viewpoints.

Integrated SDN and Non-SDN Network Management Approaches for Future Internet Environment

For years, computer scientists have been dreaming of innovating Internet in terms of performance, reliability, energy efficiency, security, and so on. However, it is nearly impossible to carry out practical large-scale experiments and verification, since new software and programs are hardly evaluated on the current Internet environment where routers and switches are totally closed. In this context, Software Defined Networking (SDN) concept has been introduced to deploy software-oriented and open programmable network coupled tightly with traditional Internet (non-SDN) environment. This tight integration results in easy and efficient deployment of SDN domains into non-SDN infrastructure, but it is also required that integrated management methods for SDN and non-SDN be developed. This paper proposes how SDN and non-SDN can be managed in an integrated manner in terms of two aspects: (1) non-SDN driven management approach and (2) SDN oriented management approach, in order to achieve reliable Future Internet environment.

A Virtualized Network Model for Wellness Information Technology Research

It occurs the needs of video-conferencing to exchange the know-how between domestic hospitals and medical school. It is the time to study of deducting a new wellness service considering diverse opinions. In this paper, we study the secure transfer of wellness information, especially medical data and for sharing to the network model.

A Study on PDR Heading Angle Error Correction Algorithm Using WLAN Based Localization Information

Indoor localization is a core technology for providing ‘Seamless LBS(Location Based Service)’. Localization is divided as two parts, which are indoor localization and outdoor localization. At the outdoor localization, dominant technology is existed like a GPS. However, this technology cannot be used in the indoor due to restriction of arrival of signal. Therefore, study of indoor localization technology is needed for providing precise position information as a GPS of the outdoor. For this, recently research institution, laboratory are developed various indoor system which is using various communication technologies. Geomagnetic sensor typically is used to estimate the direction of the user by PDR. To calculate the azimuth from geomagnetic sensors, the error of estimated azimuth can occur by axis change of geomagnetic sensors. However, regardless of the position of user, azimuth information can be obtained in WLAN-based localization system. To overcome this PDR problem, this thesis introduces research for improve estimation the direction of user using WLAN-based localization information.

Sidelobe Suppression Methods of Cubic-Phase Linear Chirp in Two-Ray Multipath Model for UWB Ranging

The UWB communication system occupies a very large bandwidth, 7.5 GHz. This enables high precision ranging that provides correct position information. In this paper, we will present a method to reduce side-lobes in receiver. Reducing side-lobes can enhance the accuracy of ranging system. Ranging system with high ratio of main-lobe to 1st side-lobe produces lower calculation error in ranging. Proposed cubic-phase chirp signal method can reduce the power of 1st side-lobe, that is, realize higher accurate ranging.