• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1B
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• pp.7-20
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• 2011

Recently, Proxy Mobile IPv6(PMIPv6) networks have been studied as the mobility management protocol to effectively use limited wireless resources. And the multicasting, which is core technology of the Internet broadcast system such as mobile IPTV, has been discussed mainly based on PMIPv6 network. However, multicasting based on PMIPv6 network causes disconnection of services because it does not solve problems of packet loss during binding and group joining procedure. Hence, we propose a seamless multicast scheme which prevents packet loss in PMIPv6 networks. The proposed scheme achieves lower latency than the existing scheme because it combines binding and group joining procedure, a1so it does not cause about packet losses due to performing buffering. We proved the performance using the simulations.

• The Journal of the Korea Contents Association
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• v.6 no.3
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• pp.46-54
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• 2006

Various schemes for mobility are currently studied in ITU-T, 3GPP, IETF, and so on. Mobility support in NGN for seamless service is necessarily required. Currently proposed mechanisms are MIPV6,0, Q.MMF, and IMS. However the performance comparison of all existing schemes is not examined as yet. That is, the existing methods need to be compared according to each performance parameter. So, in this paper, we investigate and compare the performances of MIPv6,0, Q.MMF, IMS to location registration. In addition, this paper presents the performance comparison of handover latency times. For this, we use NS-2 simulator. As a result of analysis, Q.MMF shown the best performance as it is measured the minimum time and cost. And it has low handover latency time in comparison with other mechanisms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3B
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• pp.207-215
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• 2006

It has known that the handover based on MIP in mobile environments has many constraints for proving seamless service due to well hon problems. Although there has been researching for the solutions, such as MRSVP and HMRSVP etc, it is difficult to do the research related with QoS due to the issues based on MIP used as a seamless mobility. In this paper, the seamless provides in a mobility based on SCTP, which is applied by IntServ for end-to-end QoS service. The paper also proposes the path management scheme for saving reservation cost. the scheme searches a new path on the moving mobile terminal and reserves the resources on the path for providing seamless QoS service. The paper is also analyzed on the comparition between a SCTP based and MIP based solutions. the scheme is evaluated using the cost effect saved for resource reservation.

• Journal of KIISE:Information Networking
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• v.36 no.4
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• pp.309-321
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• 2009

Nowadays, requests of connecting to the Internet while moving are increasing more and more, and various technologies have been developed for satisfying those requests. The IETF nemo WG standardized "Network Mobility Basic Support Protocol" for supporting mobile network through extending existing MIPv6 protocol for supporting host mobility. But, mobile networks can be nested while they are changing their location. And if they are multi -level nested, that causes some problems because of protocol characteristic. In this paper, we try to solve the problem that is complicated routing path caused by multi-level nesting of mobile networks with our limited prefix delegation method. We give a little modification to the standard protocol and add some functions to mobile router. With results from analysis, we could say that our method has better performance than other proposed methods.

• Journal of Broadcast Engineering
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• v.23 no.6
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• pp.813-823
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• 2018

UHD content is characterized by higher bandwidth requirements to provide seamless playback. The existing HTTP adaptive streaming scheme periodically requests video segment of lower quality than the available bandwidth in the steady state. In the steady state, the On-Off pattern is repeated due to the difference of the available bandwidth and the encoding rate of the content. And the repeated Off interval is causing the problem that can not efficiently use the available bandwidth. In the wireless environment where the delay and loss rate are higher with large bandwidth fluctuations, this problem is exacerbated because the available bandwidth is estimated inaccurately. Therefore, in this paper, we propose a segment scheduling scheme for efficient bandwidth utilization of UHD contents streaming in wireless environment. Proposed scheme is a group segment that simultaneously reqeusts multiple segments in one request message in order to reduce frequency of OFF interval. Through simulation, Our scheme improves bandwidth utilization.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2004-2010
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• 2009

The characteristic of the backbond for distribution service in WMNs(Wireless Mesh Networks) is that WMNs has multiple links connected to mesh points and dynamic routing protocol such as AODV to establish routing paths. When the terminal is communicating with the service through new AP, mobile nodes can resume communication by setting only the link between new AP and mobile node in the case of existing WLANs, but WMNs needs path establishment process in multihop networks. Our goal in this paper is to support the seamless communication service by eliminating path establishment delay in WMNs. We present the method that eliminates the handover latency by predicting the location of handover using GPS information and making the paths to their destination in advance. We implement mesh nodes using embedded board that contains proposed handover method and evaluate performance of handover latency. Our experiment shows that handover delay time is decreased from 2.47 to 0.05 seconds and data loss rate is decreased from 20~35% in the existing method to 0~10% level.

• Journal of Broadcast Engineering
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• v.22 no.5
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• pp.618-631
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• 2017

In this paper, we propose a modification of fuzzy logic based DASH adaptation algorithm(FDASH) for seamless media service in time-varying network conditions. The proposed algorithm selects more appropriate bit-rate for the next segment by the modification of the Fuzzy Logic Controller(FLC) and reduces the number of video bit-rate changes by applying Segment Bit-rate Filtering Module(SBFM). Also, we apply the Start Mechanism for clients not to watch the low quality videos in the very beginning stage of streaming service and add the Sleeping Mechanism to avoid any buffer overflow expected. Ultimately, we verified by using NS-3 Network Simulator that the proposed method shows better performance compared to FDASH. According to the experimental results, there is no buffer underflow/overflow within the limited buffer size, which is not guaranteed in FDASH on the other hand. Also, we confirmed that mFDASH has almost the same level of average video quality against FDASH and reduces about 50% of number of video bit-rate changes compared to FDASH in Point-to-Point network and Wi-Fi network.

• Journal of KIISE:Information Networking
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• v.32 no.2
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• pp.203-214
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• 2005

The integration of 3G networks and WLANs as complementary has been begun to attract much attention in industry as well as academia. This topic is becoming a burning issue, and one of the key questions which it raises is how to support a seamless vertical handoff. This paper introduces a new network interface selection algorithm for energy-efficient vertical handoff in tightly coupled systems capable of supporting seamless handoff. Our proposed scheme, Wise Interface Selection (WISE) switches the active network interface, after taking into consideration the characteristics of the network interface cards and the current level of data traffic, with the cooperation of the mobile terminals and network. Network interface switching operates independently on both the downlink and the uplink for the purpose of energy conservation. We show through simulation that less energy is consumed with WISE than when only a 3G network or WLAN interface is used, resulting in a longer lifetime for the mobile terminals. In the case of TCP connections, additional throughput gain can also be obtained.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.9
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• pp.1703-1710
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• 2008

As the performance of digital camera keeps going on, the digital camera becomes into wide use recently so that the number of digital images taken by digital camera is increased rapidly. Given the augmentation of digital images, the digital photo frame has appeared for storing and enjoying the digital image and receives attention as the price of digital frame becomes down. However, users with the existing digital frame only could display the digital images and stream media stored in local disk. In the paper, we design and implement a new digital photo frame baled on ubiquitous which could provide a more variety of service to the user. With the proposed digital photo frame, the user could obtain the environment information and the digital image from multimedia sensor network. The users also could enjoy the various stream media stored in the remote streaming server seamlessly. In addition, the user could update the digital image through the web site at anywhere.

• Journal of IKEEE
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• v.15 no.2
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• pp.179-189
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• 2011

This paper presents an SVC based multi-channel transmission technique. Transmission of high definition multimedia and its service efficiency can be significantly improved by the proposed method. In this method, the HD stream is divided into the two layer streams, i.e., a base layer stream and an enhancement layer stream. The divided streams are transmitted through a primary channel and an auxiliary channel, respectively. The proposed technique provides a noble mode switching technique which enables a seamless service of HD multimedia even under the conditions of abrupt and intermittent deterioration of the auxiliary channel. When the enhancement layer stream is disrupted by the channel monitoring in the mode switching algorithm, the algorithm works further to maintain the spatial and time resolution of the HD multimedia by upsampling and interpolating the base layer stream, consequently serving for the non disrupted play of the media. Moreover, the adoption of an adaptive switching algorithm significantly reduces the frequency of channel disruption avoiding the unnecessary switching for the short period variations of the channel. The feasibility of the proposed technique is verified through the simulation study with an example application to the simultaneous utilization of both Ku and Ka bands for HD multimedia broadcasting service. The rainfall modeling and the analysis of the satellite channel attenuation characteristics are performed to simulate the quality of service performance of the proposed HD broadcasting method. The simulation results obtained under a relatively poor channel (weather) situations show that the average lasting period of enhancement layer service is extended from 9.48[min] to 23.12[min] and the average switching frequency is reduced from 3.84[times/hour] to 1.68[times/hour]. It is verified in the satellite example that the proposed SVC based transmission technique best utilizes the Ka band channel for the service of HD broadcasting, although it is characterized by its inherent weather related poor reliability causing severe limitations in its independent application.