• Journal of the Korea Society for Simulation
• /
• v.15 no.3
• /
• pp.87-91
• /
• 2006

With the growth of the internet, the number of wireless internet users has increased continuously up to date. However, mobile communications could not support high speed transmission rate with cheap communication fee and wireless LAN has problems in providing terminal mobility and wide area connectivity, respectively. So the WMAN standard has been newly designed to make up for these limits. The initial 802.16 specification effectively offers a solution for providing fixed users with high speed wireless communication but it does not offer terminal mobility. So the 802.16d and 802.16e have been developed as the next generation solution that can support various PHY layer (SC, SCa, OFDM, OFDMA) and offer the terminal mobility. In this paper, we propose an effective uplink scheduling algorithm for VoIP with using UGS, and we show that our proposed algorithm is superior in view of average delay and management of uplink bandwidth to conventional rtPS algorithm and the scheme in reference, with using NS-2 network simulator.

• 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 KIISE:Information Networking
• /
• v.34 no.1
• /
• pp.48-61
• /
• 2007

WiBro (Wireless Broadband) service, developed in Korea, can provide the host mobility while its users hang around within the subnet. Next-generation Internet protocols, IPv6 and Mobile IPv6 (MIPv6), provide a plenty of addresses to the nodes and enable the handover between different subnets. However, MIPv6 is not enough to support a real time service such as VoIP (Voice over IP) due to the long latency, and it is necessary to develop an enhanced handover mechanism which is optimized to the WiBro networks. In this paper, we suggest an improved fast handover mechanism while the mobile node moves around WiBro networks. The proposal is based on Fast Mobile IPv6 (FMIPv6) which is the representative protocol for fast handover, and reduces the handover latency by the close interaction between the link layer (WiBro MAC) and IP layer (FMIPv6). Finally, we analyze the performance of proposed mechanism through the mathematical analysis.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2014.05a
• /
• pp.578-581
• /
• 2014

Blackhole attack, a kinds of attacks to routing function, can cause critical effects to network transmission function, Especially, on MANET(Mobile Ad-hoc Network) which it is not easy to prepare functions to respond malicious intrusion, transmission functions of entire networks could be degraded. In this paper, effects of blackhole attack to network transmission performance is analyzed on lattice structured MANET. Specially, performance is measured for various location of blackhole attack on lattice MANET, and compared with the performance of random structured MANET. This paper is done with computer simulation, VoIP(Voice over Internet Protocol) traffic is used in simulation. The results of this paper can be used for data to deal with blackhole attack.

• Proceedings of the Korean Society for Quality Management Conference
• /
• 2009.10a
• /
• pp.89-94
• /
• 2009

In the past few years with the popularization of the Internet using mobile devices such as the universal in the field of information technology has made rapid development and spread, the width and speed of change is also expected to grow much. As a result Internet telephony (VoIP) was to emerging, VoIP as a leader in next-generation converged services, the proliferation of IPTV services, including the successful introduction and subsequent convergence of the early to gauge whether the settlement is much distance in terms of importance. Therefore, this research using the Internet and telephone customer satisfaction survey, and Kano analysis is important from the perspective of the customer requirements by looking at what the Internet phone service in the development and improvement priorities are supposed to be able to stand.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2015.04a
• /
• pp.90-92
• /
• 2015

최근 IT기술의 발달과 의료 서비스의 증가로 웨어러블 헬스케어에 대한 관심이 높아지고 있다. 기존 원칙 진료 시스템에서는 의사와 환자의 직접적인 대면 없이 진료데이터만으로 환자를 판단함으로 인하여 의료서비스의 질이 저하되는 문제가 있었다. 또한 원격진료만으로는 사용자의 증상을 정확하게 전달 할 수 가 없기 때문에 원격진료에 대한 사용자의 만족도가 낮았다. 이를 위해 본 논문에서는 VoIP 환경에서 화상진료를 지원하는 SIP 기반 스마트폰 헬스케어 시스템을 제안한다.

• Proceedings of the Korea Contents Association Conference
• /
• 2009.05a
• /
• pp.884-888
• /
• 2009

Vehicular Adhoc Networks (VANET), a Vehicle-to-Infrastucture or Vehicle-to-Vehicle communication technology, is an area that makes more specific use of Mobile Adhoc Networks(MANET). VANET's Quality of Service(QoS) focuses on preventing possible emergencies like car crash from happening by immediately transmitting information to the cars around, while MANET's QoS is being studied for the quality of multimedia data such as Video on Demand(VoD), Video streaming, Voice over IP(VoIP), etc. In this paper, I structure the actual network configuration using Link State Routing(LSR), implement QoS Provisioning Model using Common Open Policy Service(COPS), and suggest more effective k-hop Cluster and inter-domain policy negotiation which fit better to the characteristics of VANET.

• 한국정보통신설비학회:학술대회논문집
• /
• 2009.08a
• /
• pp.99-103
• /
• 2009

Recently, as wired and wireless communication services have rapidly developed and multimodal mobile devices which have various characteristics have widely spread, the need for new convergence services increases. The growing population of VoIP technologies and the high communication expense yield that the market of IP based telephony such as WiFi phone and IP phone is substituted for one of the conventional PSTN telephony. With the help of this trend, the wireline network operators desire to find a market in mobile networks. Therefore, they focus on Fixed Mobile Convergence (FMC) service as one of the key factors to accomplish this goal. FMC services are able to provide the mobility of voice services between circuit switched and packet switched networks. IP Multimedia Subsystem (IMS) based Voice Call Continuity (VCC) is one of the schemes to embody FMC services. As Application Server (AS) which has this VCC function provides seamless handover of services between heterogeneous networks, FMC subscribers can communicate seamlessly with others m WiFi domain and COMA domain using WiFi-COMA dual phone. Most of enterprises have already introduced IP network infrastructure and IP-PBX (Private Branch eXchange) for telephony. However, the problems of high communication cost and work inefficiency due to frequent outside jobs or business trips have remained. In order to solve these problems, demands for enterprise FMC services increase. In this paper, we introduce a new IP-PBX based VCC model that can provide seamless handover of voice services between WiFi and COMA networks for enterprise users and we investigate some interworking and security issues between Soft Switch (SSW) and IMS, or between IMSs. In addition, we introduce a new service that can provide the continuity of voice sessions as well as video sessions using Multimedia Session Continuity (MMSC) technology which has evolved from VCC. This service is expected to be one of the next-generation personalized services based on user's context.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38B no.5
• /
• pp.355-367
• /
• 2013

In the Policy and Charging Control(PCC) architecture of the 3GPP and WiMAX forum, the Policy and Charging Rule Function(PCRF) controls and configures the policies of quality of services(QoS) and accounting to a Policy and Charging Rule Enforcement Function(PCEF). In this paper, we categorize the errors into three types that include a disconnection with peer entity, a delayed or no response and a response with failure result, and propose a scheme to automatically synchronize the data between the PCRF and the PCEF for each type of error. Also, we conduct a quantitative analysis to see how much it can help to maintain the cell capacity of the mobile VoIP service in a WiBro network, which is implemented in Korea according to the standards of WiMAX. We can see that our proposed scheme improves the performances of PCC by preventing the waste of radio resources, the overload of systems, the memory leakage of servers, the system shutdown, and so on. We have validated the scheme by implementation, and reflected it in WiMAX standard documents.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2011.10a
• /
• pp.261-264
• /
• 2011

Corded telephone to the phone using a wireless phone as the trend to switch, free Wi-Fi-enabled mobile phones, netbooks, and mobile devices, are spreading rapidly. But wireless Internet phone calls using your existing Internet network to deliver Internet services because it has a vulnerability that will occur. Government agencies are using Voice over Internet Protocol(VoIP) calls from the current wired and wireless connection and usage is increasing. In this paper, we have discovered that the vulnerability of wireless internet Wi-Fi AP and the FMC administrative agencies, such as VoIP on your wireless device to study the vulnerability. Wi-Fi AP and the FMC is to analyze the vulnerability. VoIP call interception, attack, attack on the base of the experiment is the analysis. Security-enhanced VoIP call for a Wi-Fi AP and the FMC's defense against man-in-the-middle attacks and is the study of security measures.