• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1076-1085
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• 2004

Recently, the demands for real-time service and multimedia data are rapidly increasing. There are significant redundancies between header fields both within the same packet header and in consecutive packets belonging to the same packet stream. And there are many overheads in using the current UDP/IP protocol. Header compression is considered to enhance the transmission efficiency for the payload of small size. By sending the static field information only once initially and by utilizing dependencies and predictability for other fields, the header size can be significantly reduced for most packets. This work describes an implementation for header compression of the headers of IP/UDP protocols to reduce the overhead on Ethernet network. Typical UDP/IP Header packets can be compressed down to 7 bytes and the header compression system is designed and implemented in Linux environment. Using the Header compression system designed between a server and clients provides have the advantage of effective data throughput in network. Since the minimum packet size in Ethernet is 64 bytes, the amount of reduction by header compression in practical chatting environment was 6.6 bytes.

• The KIPS Transactions:PartB
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• v.15B no.6
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• pp.585-594
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• 2008

The issues that we should consider in the process of providing mobile web service using a mobile device are seamless service and QoS-guaranteed service. HMIPv6 has MAP because of improving packet loss and transmission delay due to disconnection. However, a load is concentrated on HMIPv6 because of receiving and delivering packet for MN. Owing to this, real time data fails to be processed quickly, and also adaptive mobile service is required for QoS guaranteed service. However, this method demands the response time cost of contents service owing to the hardware differences of various devices. Therefore, we improve the process performance of real time data by applying a queue in MAP for seamless service in this paper. For decreasing response time cost, we propose mobile web service method which has reusable cache of contents using the elements of contents. The result of a numerical formula and simulation shows that our proposed method is superior under various system conditions.

• Journal of the Korea Society of Computer and Information
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• v.15 no.6
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• pp.57-64
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• 2010

Due to the limited storage space in video proxy server, it is often required to replace the old video data which is not serviced for long time with the newly requested video. This replacement causes the service delay and increase of network traffic. To circumvent this problem, we propose the an efficient replacement scheme in a video proxy server. In addition, we present a video data management technique for decreasing the number of replacement in video proxy server. For this purpose, we employ a memory in video proxy server. If the video segment which is loaded in memory is requested once again by a different user, this segment is resided in memory. The video in the memory is stored in the video proxy server depending on the consuming pattern by users. The simulation results show that the proposed algorithm performs better than other algorithms in terms of packet hit rate and number of packet replacement.

• Journal of the Korea Society of Computer and Information
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• v.19 no.5
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• pp.61-69
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• 2014

Collaborative filtering recommendation creates similar item subset or similar user subset based on user preference about items and predict user preference to particular item by using them. Thus, if preference matrix has low density, reliability of recommendation will be sharply decreased. To solve these problems we suggest Hybrid Preference Prediction Technique Using Weighting based Data Reliability. Preference prediction is carried out by creating similar item subset and similar user subset and predicting user preference by each subset and merging each predictive value by weighting point applying model condition. According to this technique, we can increase accuracy of user preference prediction and implement recommendation system which can provide highly reliable recommendation when density of preference matrix is low. Efficiency of this system is verified by Mean Absolute Error. Proposed technique shows average 21.7% improvement than Hao Ji's technique when preference matrix sparsity is more than 84% through experiment.

• Journal of Communications and Networks
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• v.18 no.3
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• pp.460-475
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• 2016

The existing Proxy Mobile IPv6 suffers from a long handover latency which in turn causes significant packet loss that is unacceptable for seamless realtime services such as multimedia streaming. This paper proposes an OpenFlow-enabled proxy mobile IPv6 (OF-PMIPv6) in which the control of access gateways is centralized at an OpenFlow controller of a foreign network. The proposed OF-PMIPv6 separates the control path from the data path by performing the mobility control at the controller, whereas the data path remains direct between a mobile access gateway and a local mobility anchor in an IP tunnel form. A group of simple OpenFlow-enabled access gateways performs link-layer control and monitoring activities to support a comprehensive mobility of mobile nodes, and communicates with the controller through the standard OpenFlow protocol. The controller performs network-layer mobility control on behalf of mobile access gateways and communicates with the local mobility anchor in the Proxy Mobile IPv6 domain. Benefiting from the centralized view and information, the controller caches the authentication and configuration information and reuses it to significantly reduce the handover latency. An analytical analysis of the proposed OF-PMIPv6 reactive and proactive handover schemes shows 43% and 121% reduction in the handover latency, respectively, for highly utilized network. The results gathered from the OF-PMIPv6 testbed suggest similar performance improvements.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.193-197
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• 2015

Recently, the new issues for the safety and the information delivery system in the ship are raised. The deployment and the efficient algorithms of deploying the wireless sensor networks instead of using the built-in wired networks or the setup of the new wired networks is more desirable than the deployment of the wired networks in a ship after its final production since it can reduce the cost and the time of the brand new wired networks by reshaping some of the internal structure of the ship. In this paper, the shipboard signal propagation measurement system based on the signature sequence-three way slave mode are designed and its measureed data are analysed after measuring the signal propagation characteristics. Consequently, it is expected that the reliable and cost-effective signal measurement system with the three way algorithm for the deployment of the shipboard wireless networks can be achieved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.43-51
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• 2015

Upcoming cellular networks such as LTE-advanced and IEEE 802.16m are enhanced by relay stations to support high data rate multimedia services and minimize the shadow zone with low cost. Enhancing the relay stations, however, divides the multihop cellular network into smaller microcells and the distance between microcells is closer, which intends large intra-cell and inter-cell interference. Especially the access link on downlink in the OFDMA cellular network is the throughput bottleneck due to the severe interference caused by base stations and relay stations transmitting large data to mobile stations simultaneously. In this paper, we present interference aware channel allocation algorithm to avoid severe interference on multihop cellular networks with random topology. Proposed algorithm increases SINR(signal to interference plus noise ratio) and decreases number of required control messages for channel allocation, so that increases overall throughput on the networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.183-186
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• 2015

Recently, the demand for the safety and the information delivery system in the ship increases. The deployment of the wireless sensor networks instead of using the built-in wired networks or the setup of the new wired networks is more desirable than the deployment of the wired networks in a ship after its final production since it can reduce the cost and the time of the brand new wired networks by deforming some of the internal structure of the ship. In this paper, the shipboard signal propagation measurement system based on the signature sequence-two way slave mode are designed and its measurement data are analysed after measuring the signal propagation characteristics. Consequently, it is expected that the reliable and cost-effective signal measurement system for the deployment of the shipboard wireless networks can be built.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.371-377
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• 2011

Users of the Information Age, IT usage patterns of the wired broadband information services and various forms of the same quality wireless multimedia services are required. Changes of these times the next-generation mobile communications (IMT-Advanced) has emerged as the necessity of developing its current voice and packet data communications on the move in the high-speed 100Mbps, 1Gbps in stationary and slow data transmission rates up to fixed-mobile convergence based on needed to provide ubiquitous service platform for the realization of IMT-Advanced is the time for preparation. In particular, 3-5GHz band, focused on mobile communications can be used to secure the necessary frequency band relocated and the existing crosstalk analysis methodology developed for the services rendered, and the frequency of such results to obtain new spectrum for IMT-Advanced for the country to secure the frequency characteristics and IMT-Advanced 3-5GHz band for the radio frequency of the characterization techniques necessary to develop a national wireless communication interference and frequency-based technology acquisition and management skills were identified.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.4
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• pp.381-391
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• 2013

Wireless transmission of uncompressed video guarantees higher quality with lower latency than compressed video transmission. Although current wireless technologies cannot fully cover required data rates of about a few Gb/s for full high definition resolution, some wireless technologies such as ultra-wideband (UWB) provide 1 Gb/s data rate which is adequate for uncompressed video transmission in portable devices. In this paper, we propose an uncompressed video transmission system for wireless mirroring services in portable devices. We firstly simulated the performance of uncompressed video transmission using single or multiple 1 Gb/s UWB technology. Then we implemented hardware-based uncompressed video processing block and Gb/s wireless MAC accelerator. Finally, we show the implementation result and the demonstration of uncompressed HD video transmission using multiple 1 Gb/s UWB PHYs.