• KIPS Transactions on Computer and Communication Systems
• /
• v.1 no.1
• /
• pp.35-46
• /
• 2012

The development of wireless communication systems has resulted in the availability of several access technologies at any geographic area, such as 3G networks, wireless local area networks (WLANs) and wireless broadband networks. The development of these technologies is provided for users who have experienced mobile network environments which are slow or fast-movement environment and change distance between the AP(Access Point). This paper describes network performance issues in various environmental changes. Also, Fuzzy logic is applied to evaluate the performance in vehicle networks around users' environmental factors to focusing on the minimizing of transfer time and costs. First, WLAN and 3G networks fixed distance between AP, Second, WLAN and 3G networks random distance between APs, finally above two environmental with vehicle Ad hoc networks is analyzed. These V2I and V2V environmental condition are assumed. Results which based on Fuzzy logic suggest an optimal performance in vehicle network environments according to vehicle speed and distance between APs. Proposed algorithm shows 21% and 13% improvement of networks performance in V2I and V2V environment.

• Annual Conference of KIPS
• /
• 2016.10a
• /
• pp.775-778
• /
• 2016

로봇 주행 기술은 전통적인 로봇요소 기술 외에도 여러 기술로 대상 응용서비스에 따라 IT 기술과 적극적인 융합을 통해 다양한 주행방법과 주행성능이 향상되고 있다. 본 논문에서는 대표적인 실내 모바일 로봇인 로봇 청소기를 대상으로 기존의 방법인 적외선과 카메라 방법이 아닌 보통 가정에도 쉽게 존재하는 AP를 이용해 목표를 설정하여 포섭구조 이론을 기반으로 동적인 환경에서도 충전 스테이션 까지 자율 주행이 가능한 로봇 알고리즘을 설계하였다. 그 결과 동적인 환경을 설정하여 로봇이 AP를 찾아가는 것을 확인하였고 주행 경로와 경과 시간을 표로 도출하여 다른 경우를 예측할 수 있게 하였다. 향후 행동 기반 로봇과 다양한 센서를 이용하여 로봇의 위치와 목표점 사이의 최단거리 경로를 구하여 주행하는 것이 목표이다.

• Annual Conference of KIPS
• /
• 2015.10a
• /
• pp.566-568
• /
• 2015

최근 IETF(Internet Engineering Task Force) CoRE(Constrained RESTful Environment) 워킹그룹에서 IoT 프로토콜로 CoAP(Constrained Application Protocol)을 표준으로 채택하였다. 본 논문에서는 모바일 환경에서 CoAP 프로토콜을 이용한 자원 디렉토리 기반의 IoT 노드와 스마트폰 연결 구조를 제시한다. 스마트폰과 IoT(Internet of Things) 노드 사이에 자원 디렉토리를 두고, 이를 통해 스마트폰은 IoT 노드를 검색하고 상황 정보를 습득할 수 있도록 하고 있다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39C no.1
• /
• pp.1-8
• /
• 2014

This paper proposed a method that prevents data leakage and modulation and detects an unauthorized device by using AP and mobile device. Most of existing method for detecting and preventing an unauthorized device are similar to type of Evil Twin. However, in previous studies can not resolve many security accident and have the problem to cope with effectively security accident on various network. In order to solve these problem, companies prepare security accident through the varies policy and guideline. but It is hard to prevent all security accident because it is consistently increasing everyday. This paper suggests technique of detecting and preventing an unauthorized device using Context Awareness and Mobile Device Management. Firstly, when mobile device go into internal network, server distinguish access permission and authorization of mobile device using acquiring the conetxt information of mobile device. By using this result, server applies the appropriate management technique to the mobile device for leakage and accident of internal network.

• Proceedings of the Korea Contents Association Conference
• /
• 2009.05a
• /
• pp.682-686
• /
• 2009

The MAC protocol of HiperLAN/2 is based on TDMA/TDD. The radio channels are assigned by AP(Access Point) that is centrally operated. Mobile terminal that data transmission is necessary to uplink requests radio resource to AP through RCH channel. The changing number of RCHs in each MAC frame is important because too many RCHs may result in a waste of radio resources and too few RCHs may result in many access collisions and prolong time that connect to AP. Therefore, number of RCH should be allocated properly according to traffic. From these viewpoint, this paper proposes an advanced scheme that dynamically changed the number of RCH which is based on the number of success and collision of RR message in previous MAC frame. To prove efficiency of proposed scheme, a lots of simulations are conducted and analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.3A
• /
• pp.293-302
• /
• 2004

Wireless LAN is a rather mature communication technology that connects mobile terminals. A typical wireless LAN system is composed of one AP and more than one terminals, which is called a BSS. Terminals near to an AP can receive high rate data but terminals far from an AP may not receive data with guaranteed high speed rate because received signal strength is weakened. This paper proposes a method to allow high speed data transmission by grouping terminals and using part of wireless terminals as repeaters. We compare and analyze proposed grouping algorithms based on Depth First Search and Breadth First Search via simulations. A grouping algorithm based on Breadth First Search is shown to be more effective in term of efficiency and coverage.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2009.10a
• /
• pp.987-990
• /
• 2009

The MAC protocol of HiperLAN/2 is based on TDMA/TDD. The radio channels are assigned by AP(Access Point) that is centrally operated. Mobile terminal that data transmission is necessary to uplink requests radio resource to AP through RCH channel. The changing number of RCHs in each MAC frame is important because too many RCHs may result in a waste of radio resources and too few RCHs may result in many access collisions and prolong time that connect to AP. Therefore, number of RCH should be allocated properly according to traffic. From these viewpoint, this paper proposes an advanced scheme that dynamically changed the number of RCH which is based on the number of success and collision of RR message in previous MAC frame. To prove efficiency of proposed scheme, a lots of simulations are conducted and analyzed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2009.05a
• /
• pp.455-458
• /
• 2009

Bluetooth technology has been applied to mobile device, personal computers, peripherals, information and variety of consumer electronics. Not also the original Bluetooth technology must be especially focused in the application of mobile phone but applications such as wireless headsets and dial-up networking may be increased. However Bluetooth is so only focused to wireless headset application that the various software applications are presently ignored. In this paper, we propose the framework design to implement Bluetooth profile for kiosk servers, which can be used in Theater, train station, bank, government and public offices. Then mobile devices capable of processing user's input/output can be remotely accessed in these servers by using Bluetooth module and AP, although Kiosk servers are only processed user input data.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.2A
• /
• pp.142-152
• /
• 2010

When a mobile station(MS) performs a handover, in the IEEE 802.11 WLAN, MS's channel scanning for discovering new available APs is the dominating factor in handover latency, accounting 90% of overall latency. In order to reduce such a scanning latency, we focus on the method for reducing the number of channels for the MS in handover process to scan. With the help of IEEE 802.21 information server(IS), a proper order of groups of channels to be scanned is offered by the current AP depending on the information of neighbor APs in terms of the distance from serving AP, traffic load and network topology. By using this scanning order, the passive scanning of a MS in normal operation enables the MS to filter out the unavailable channels, and thus to classify the candidate channels of neighbor APs into three groups. Then, a handover-imminent MS can perform the active scanning from the most reliable group of channels. Simulation results show that the proposed scanning scheme reduce the scanning latency in comparison with the conventional scheme.

• Journal of KIISE:Computing Practices and Letters
• /
• v.13 no.5
• /
• pp.260-270
• /
• 2007

Owing to the improved wireless communication technologies, it is possible to provide streaming service of multimedia with PDAs and mobile phones in addition to desktop PCs. Since mobile client devices have low computing power and low network bandwidth due to wireless network, the transcoding technology to adapt media for mobile client devices considering their characteristics is necessary. However, since mobile clients use wireless network and the wireless network have less stable bandwidth according to distance from AP and environments, it is hard to support stable QoS to mobile clients. In this paper, we propose a dynamic bit rate control method for transcoding in order to supprot stable QoS of streaming media service to mobile clients via wireless network. The proposed method is shown to serve seamless streaming media service with adaptive bit rate control according to state of wireless network in real time and to reduce transmission failure from experiment.