• The Journal of the Korea Contents Association
• /
• v.8 no.6
• /
• pp.43-53
• /
• 2008

Hyper text transfer protocol (HTTP) over transmission control protocol (TCP) is currently used to transfer objects in the Internet. Stream control transmission protocol (SCTP), an alternative to TCP, which allows for independent delivery among streams, and can thus reduce the mean response delay of web object. We present an analytical model to find the mean response delay for HTTP over SCTP, therefore, estimate the effectiveness of SCTP over TCP. Typical TCP delay models assume the wired environment. On the contrary, the proposed model in this paper assumes the multiple packet losses and wireless environment where fast retransmission is not possible due to small window. The estimated mean response time can be used the benchmark to meet quality of service (QoS) at end-user. We validate the accuracy of our model using experiments. It is shown that the differences between the results from model and those from experimental are very small below 6 % on average. We also find that the mean response delay for HTTP over SCTP is less than that for HTTP over TCP.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.2A
• /
• pp.86-96
• /
• 2006

In recent year, EPON(Ethernet PON) system is expected to be more attractive solutions for high speed, broadband access networks in next generation access networks due to the conversionce of low-cost ethernet equipment and low-cost fiber infrastructure. Upstream channel control algorithm is essential to hare upstream bandwidth in EPON. In this paper, we suggest HUHG(High Utilization and Hybrid Granting) algorithm for supporting high bandwidth utilization and QoS for different service class. This algorithm improves bandwidth utilization as removing or diminishing idle time of upstream channel using characteristics of fixed EF(Expedited Forwarding) sub-cycle. The proposed algorithm also minimizes the packet delay and delay variation of EF class. We conduct detailed simulation experiments using OPNET to study the performance and validate the effectiveness of the proposed algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.1B
• /
• pp.27-34
• /
• 2010

As VoIP systems move to wireless environments with much higher average packet loss rates than wired networks, it becomes less possible for the network to assure a reasonable QoS. So, real-time quality monitoring for mobile VoIP applications is an important issue to be explored. In this paper, we explore perceptual quality dependency on two parameters: the burst loss rate and average burst length. Also, we propose a simple 'moving average' approach with $\alpha$ aiming to measure those parameters on real-time basis. In order to find how accurately the two parameters measured estimate the real perceptual quality, we compare actual measured PESQ scores with estimated value by matching the measured quality metric to the trained MOS table. Finally, we propose the quality-based accounting system, which can set obvious continuities between quality and billing.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.13 no.5
• /
• pp.903-909
• /
• 2010

ADAS is the air defense control system performing air surveillance and identification of ROK and near air. This system is self-developed by Air Force, currently operated successfully as the alternative system of MCRC. ADAS processes converting and combining transferred the real time radar data detected by radars. additionally, it displays significant radar data as producing in tracks. Then, it uses the message queue for IPC(Inter Process Communication). the various tactical data processed in the server is ultimately send to the network management process through the message queue for transmitting to the weapon director console. the weapon director receives this transmitted tactical data through the console to execute air defense operations. However, there is a problem that data packet is delayed or lost since the weapon Director does not receive as the amount of tactical data from the server overflowed with air tracks and missions increased. This paper improved the algorism to display and transmit the various tactical data processed from ADAS server to numbers of the weapon director console in the real time without any delay or lost. Improved the algorism, established at exercise, the development server in the real operation network and the weapon director console, is proved by comparing the number of sending tactical data packets in the server and receiving packets in the weapon director.

• Journal of the Korea Society of Computer and Information
• /
• v.19 no.12
• /
• pp.227-237
• /
• 2014

The purpose of this paper is to implement a multiple bio-signal central monitoring system based on textile fabrics flexible platform which can obtain and monitor bio signals(heart rate, body temperature, electrocardiography, electromyogram) of workers in special working environments and additional situational information (3-axis acceleration, temperature, humidity, illumination, surrounding image). This system can prevent various accidents that may occur in the remote work environment and provide fast and efficient response by detecting workers' situations in real-time. For it, the textile fabrics flexible platform was made as innerwear or outerwear so that it does not interfere with workers' performance while collecting bio-signal and situational information, and obtained information is sent to the central monitoring system through wireless communication. The central monitoring system is based on wireless medical telemetry service of WMTS (Wireless Medical Telemetry Service); can monitor from 2 to 32 people simultaneously; and was designed so that it can be expanded. Also, in this study, to verify performance of the WMTS communication model, packet transmission rates were compared according to the distance.

• Journal of Korea Multimedia Society
• /
• v.10 no.10
• /
• pp.1295-1309
• /
• 2007

A wireless access point is used for all communications in the infrastructure mode wireless home networking, including communication between mobile nodes in the same service area. When a mobile station in the infrastructure mode wireless home networking moves into a dead zone, the communication between the mobile station and the access point is disconnected. To solve this problem, the existing wireless home network platforms focus on the ad hoc mode wireless home networking. However, the performance of an ad hoc network is poorly decreased when the number of mobile participating in the ad hoc network increases. In addition, although the ad hoc routing technique is necessary to support seamless communication of mobile nodes, the existing routing protocols, such as AODV and DSR, do not consider that a wireless channel state could affect performance significantly. Therefore, we propose a wireless home networking platform based on the ESCOD (End-to-end Seamless multi-hop COnnection based on Dual network mode) technique incorporating the VLR (Virtual Link Routing) scheme that supports end-to-end seamless connections. Extensive experiments show that the proposed wireless home networking platform incorporating the VLR scheme outperforms wireless home networking platforms based on the AODV and the DSR routing protocols respectively in terms of low packet transmission failure rate, fast packet transmission time, high TCP performance, and a wider coverage area of wireless home networks.

• Journal of KIISE:Information Networking
• /
• v.36 no.1
• /
• pp.34-42
• /
• 2009

In this paper, we propose a practical hybrid transport error control scheme to provide SVC video streaming service over error-prone IP networks. Many error control mechanisms for various video coding standards have been proposed in the literature. However, there is little research result which can be practically applicable to the multilayered coding structure of SVC(the scalable extension of H.264/AVC). We present a new hybrid transport error control scheme that efficiently combines layered Forward Error Correction(FEC) and Automatic Repeat Request(ARQ) for better packet-loss resilience. In the proposed hybrid error control, we adopt ACK-based ARQ instead of NACK-based ARQ to maximize throughput which is the amount of effective data packets delivered over a physical link per time unit. In order to prove the effectiveness of the proposed hybrid error control scheme, we adopt NIST-Net network emulator which is a general-purpose tool for emulating performance dynamics in IP networks. It is shown by simulations over the NIST-Net that the proposed hybrid error control scheme shows improved packet-loss resilience even with much less number of overhead packets compared to various conventional error control schemes.

• Journal of Broadcast Engineering
• /
• v.13 no.1
• /
• pp.6-16
• /
• 2008

An instable wireless channel condition causes more packet losses and retransmissions due to interference, fading, station mobility, and so on. Therefore video streaming service over a wireless networks is a challenging task because of the changes in the wireless channel conditions and time-constraints characteristics of the video streaming services. To provide efficient video streaming over a wireless networks, QoS-enhanced MAC protocol, IEEE 802.11e, is standardized recently. Tn this paper, we propose a new network-adaptive H.264 video streaming mechanism in the IEEE 802.11e wireless networks. To improve the quality of video streaming services, video stream has to adapt to the changes in the wireless channel conditions. The wireless channel conditions are estimated by the packet loss probability and informed to the application layer by the cross-layering. According to the wireless channel information, the video streaming application filters out the low-priority data. This adaptation mechanism efficiently uses system resources because it drops the low-priority data in advance. Therefore, our cross-layer design can provide improved video streaming services to the end-user. Through the implementation and performance evaluation, we prove that the proposed mechanism improves the QoS of the video streaming by providing the smoothed playback.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.9
• /
• pp.39-48
• /
• 2008

Recently, many multimedia services have emerged in Internet such as real-time and non- real time services. However, in this Internet environment, we have some limitations to satisfy each service feature. To guarantee the service features in Measurement-Based Admission Control(MBAC) based system on the flow-aware network, there is the method applying Dynamic Priority Scheduling(DPS) algorithm that gives a higher priority to an earlier incoming flow in all of the link bandwidth. This paper classifies all flows under several groups according to flow characteristics on per-flow MBAC algorithm based system. In each flow group, DPS algorithm is applied. This paper proposes two methods that are a DPS based bandwidth borrowing method and a bandwidth dynamic allocation method. The former is that if low priority class has available bandwidths, the flow of high priority class borrows the bandwidth of low priority class when high priority flow has insufficient bandwidth to connect a flow call. The later is that the each group has a minimum bandwidth and is allocated the bandwidth dynamically according to the excess rate for available bandwidth. We compare and analyze the characteristics of the two proposed methods through the simulation experiments. As the results of the experiment, the proposed methods are more effective than existing DPS based method on the packet loss and delay characteristics. Consequently the proposed two methods are very useful in various multimedia network environments.

• The KIPS Transactions:PartC
• /
• v.13C no.4 s.107
• /
• pp.471-480
• /
• 2006

Recently, multimedia communication services, such as video conferencing and voice over IP, have been rapidly spread. H.323 is an international standard that specifies the components, protocols and procedures that provide multimedia communication services of real-time audio, video, and data communications over packet networks, including IP based networks. H.323 is applied to many commercial services because it supports various network environments and has a good performance. But communication services based on H.323 may have some problem because of current network trouble or mis-implementation of H.323. The understanding of this problem is a critical issue because it improves the quality of service and is easy to service maintenance. In this paper, we implement the analysis system for H.323 protocol wihch includes H.245, H.225.0, RTP, RTCP, and so on. Tills system is able to capture, parse, and present the H.323 protocol in real-time. Through the operation test and performance evaluation, we prove that our system is a useful to analyze and understand the problems for communication services based on H.323.