• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.1
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• pp.23-31
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• 2000

In this paper, we propose an adaptive handover scheme in wireless network. The proposed handover scheme is a hybrid type of virtual path extension and rerouting. The proposed handover scheme chooses the virtual path management scheme according to the service QoS instead of the network topology which is used in the previous hybrid handover schemes. The proposed scheme supports the seamless service and small buffering during virtual path rerouting handover through the multicasting service. To evaluate the performance of the proposed scheme, we computed the number of signaling message used for handover and perform computer simulation. The simulation results show that the proposed scheme provides more efficiency in the handover delay and seamless service than the previous methods.

• Journal of Broadcast Engineering
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• v.13 no.6
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• pp.951-961
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• 2008

Cooperative diversity is a cooperative technique which exploits user diversity by decoding the combined signal of the relayed signal and the direct signal in wireless multi-hop networks. Using the cooperation, the performance of the network system can be improved because cooperative diversity which is very strong against the fading channels can be achieved. In this paper, we propose the technique that provides the enhanced visual quality of the reconstructed video using the cooperative diversity with the FMO which is the error resilience tool of H.264/AVC standardization over wireless networks. The eye-tracker can detect the gaze point of user and transmit the gaze information to the nodes. After receiving the gaze information of user, each node performs ROI encoding according to the received gaze information. After encoding, video sources are divided into ROI and Non-ROI. Through the simulation results, the better visual quality of the reconstructed video is achieved when ROI and Non-ROI are transmitted through different channels.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.489-491
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• 2002

The need for video diagnosis in medicine has been increased and real-time transfer of digital video will be an important component in PACS and telemedicine. But, Network environment has certain limitations that the required throughput can not satisfy quality of service (QoS). MPEG-4 ratified as a moving video standard by the ISO/IEC provides very efficient video coding covering the various ranges of low bit-rate in network environment. We implemented MPEG-4 CODEC (coder/decoder) and applied various compression ratios to moving ultrasound images. These images were displayed in random order on a client monitor passed through network. Radiologists determined subjective opinion scores for evaluating clinically acceptable image quality and then these were statistically processed in the t-Test method. Moreover the MPEG-4 decoded images were quantitatively analyzed by computing peak signal-to-noise ratio (PSNR) to objectively evaluate image quality. The bit-rate to maintain clinically acceptable image quality was up to 0.8Mbps. We successfully implemented the adaptive throughput or bit-rate relative to the image quality of ultrasound sequences used MPEG-4 that can be applied for diagnostic performance in real-time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.4835-4855
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• 2015

TV white space (TVWS) is showing promise to become the first widespread practical application of cognitive technology. In fact, regulators worldwide are beginning to allow access to the TV band for secondary users, on the provision that they access the geolocation database. Device-to-device (D2D) can improve the spectrum efficiency, but large-scale D2D communications that underlie TVWS may generate undesirable interference to TV receivers and cause severe mutual interference. In this paper, we use an established geolocation database to investigate the power allocation problem, in order to maximize the total sum throughput of D2D links in TVWS while guaranteeing the quality-of-service (QoS) requirement for both D2D links and TV receivers. Firstly, we formulate an optimization problem based on the system model, which is nonconvex and intractable. Secondly, we use an effective approach to convert the original problem into a series of convex problems and we solve these problems using interior point methods that have polynomial computational complexity. Additionally, we propose an iterative algorithm based on the barrier method to locate the optimal solution. Simulation results show that the proposed algorithm has strong performance with high approximation accuracy for both small and large dimensional problems, and it is superior to both the active set algorithm and genetic algorithm.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.219-236
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• 2014

In this paper, we propose a novel Proxy Mobile IPv6 network bandwidth-efficient handoff scheme. MN are classified into slow and fast one. At first MN should be registered in the microcell for bandwidth efficient handoff scheme. microcell is overlapped to handle the overflow session request which is nested. Overflow session request in macrocell requests to go back from the boundary of the microcell to new microcell. If idle session traffic is in a cell, it is requested by the target microcell. Analysis model was developed, an existing session of the session blocking probability and forcing termination probability of the session request have improved considerably. If the total traffic load of the system is not very large, the proposed scheme has the best bandwidth efficiency and provides better quality of service (QoS) to MN without costs of a lot of processing on the system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.11
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• pp.30-40
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• 2001

In this paper, we propose a dynamic slot allocation algorithm for efficient transmission of VBR services in wireless ATM networks. The proposed algorithm is based on a hybrid dynamic parameter(DP) control which combines the strength of in-band control and out-of-band control by considering the variation characteristics of buffer length in distributed mobile terminals. This algorithm consists of four sub-algorithms: dynamic parameter determination algorithm, dynamic parameter transmission algorithm, estimation algorithm of the number of request slots, and prorated-allocation algorithm. As the proposed allocation algorithm based on the hybrid DP control scheme can offer nearly precise MAC level estimations of the requirements for each VBR, the algorithm makes it possible to obtain ideal allocation efficiency. The allocation efficiency of the algorithm is shown by numerical analysis. Simulation results show that the proposed algorithm has better performance than conventional schemes in terms of allocation efficiency, delay and cell loss ratio under VBR traffic.

• Journal of KIISE:Computing Practices and Letters
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• v.6 no.2
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• pp.234-243
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• 2000

We design a modified network architecture with condsidering current Internet network model and traffic characteristics, and propose EDCBT(Enhanced Dispersed Core-based Tree) multicast routing protocol, which enhances scalabity, reliability, end-to-end delay and resource utilization EDBCT adopts bidirectional dispersed shared trees and manages both of intradomain and interdomain multicast trees for a multicast group. Each regional multicast tree is estabilshed from its core router and they are interconnected by the operation between border routers on edges of each regional network. As a result, interdomain multicast tree can be easily established. We introduce a new concept named RBTS(Region-based Tree Switching), which dramatically enhances QoS and network utilization. Finally, protocol performance and the effect of core router location are evaluated with MIL3 OPNet network simulator, in terms of end-to-end delay, packet loss and throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.680-687
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• 2013

We investigate a generalized combined power and rate adaptation scheme in direct-sequence (DS) code-division multiple-access (CDMA) communications over Nakagami fading channels. The transmission power allocated to user i is proportional to $G^p_i$, where $G_i$ is the channel gain of user i and p is a real number, and the data rate (i.e., spreading gain) is jointly adapted so that a desired QoS is maintained. We analyze the average data rate of the proposed adaptation scheme subject to fixed average and peak transmission power constraints. Our results show that the proposed joint adaptation scheme provides a significant performance improvement over power-only and rate-only adaptation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2118-2135
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• 2012

With the rapid development of heterogeneous emerging wireless technologies and numerous types of mobile devices, the need to support robust mobile video streaming based on the seamless handover in Future Internet is growing. To support the seamless handover, several IP-based mobility management protocols such as Mobile IPv6 (MIPv6), fast handover for the MIPv6 (FMIPv6), Hierarchical MIPv6 (HMIPv6) and Proxy Mobile IPv6 (PMIPv6) were developed. However, MIPv6 depreciates the Quality-of-Service (QoS) and FMIPv6 is not robust for the video services in heterogeneous emerging wireless networks when the Mobile Node (MN) may move to another visited network in contrast with its anticipation. In Future Internet, the possibility of mobile video service failure is more increased because mobile users consisting of multiple wireless network interfaces (WNICs) can frequently change the access networks according to their mobility in heterogeneous wireless access networks such as 3Generation (3G), Wireless Fidelity (Wi-Fi), Worldwide Interoperability for Microwave Access (WiMax) and Bluetooth co-existed. And in this environment, seamless mobility is coupled according to user preferences, enabling mobile users to be "Always Best Connected" (ABC) so that Quality of Experience is optimised and maintained. Even though HMIPv6 and PMIPv6 are proposed for the location management, handover latency enhancement, they still have limit of local mobility region. In this paper, we propose a robust mobile video streaming in Heterogeneous Emerging Wireless Systems. In the proposed scheme, the MN selects the best-according to an appropriate metric-wireless technology for a robust video streaming service among all wireless technologies by reducing the handover latency and initiation time when handover may fail. Through performance evaluation, we show that our scheme provides more robust mechanism than other schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.5
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• pp.859-876
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• 2010

In this paper, we propose a hierarchical application traffic classification system as an alternative means to overcome the limitations of the port number and payload based methodologies, which are traditionally considered traffic classification methods. The proposed system is a new classification model that hierarchically combines a binary classifier SVM and Support Vector Data Descriptions (SVDDs). The proposed system selects an optimal attribute subset from the bi-directional traffic flows generated by our traffic analysis system (KU-MON) that enables real-time collection and analysis of campus traffic. The system is composed of three layers: The first layer is a binary classifier SVM that performs rapid classification between P2P and non-P2P traffic. The second layer classifies P2P traffic into file-sharing, messenger and TV, based on three SVDDs. The third layer performs specialized classification of all individual application traffic types. Since the proposed system enables both coarse- and fine-grained classification, it can guarantee efficient resource management, such as a stable network environment, seamless bandwidth guarantee and appropriate QoS. Moreover, even when a new application emerges, it can be easily adapted for incremental updating and scaling. Only additional training for the new part of the application traffic is needed instead of retraining the entire system. The performance of the proposed system is validated via experiments which confirm that its recall and precision measures are satisfactory.