• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2022.05a
• /
• pp.527-528
• /
• 2022

It is not easy to identify the location of mobile terminals based on drones in the mountainous area, the densely populated urban area, or the space where mobile terminals can easily move by using equipments or modules that can recognize the location of sensors or mobile terminals with LBS (Location-Based Service). However, although the performance of GPS has developed due to the development of technology, it is still widely used in position recognition systems using GPS modules in the sea and onshore, and there is much room for more utilization. Currently, most of the existing sensor networks need to send at least three location information messages to mobile terminals with location information that a plurality of mobile base stations depend on GPS. However, location recognition of mobile repeaters that maintain a certain movement speed using acceleration sensors is necessary for efficient communication network connection.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.4
• /
• pp.752-757
• /
• 2016

Machine to Machine (M2M) communications is communications between a business application and devices via a communication network without any direct human interaction. The aim of our research is to connect any M2M device with an M2M AS (Application server) through an IMS (IP Multimedia Subsystem) Network Core using a M2M Gateway, in order to develop an M2M Horizontal Services Platform over IMS. An IP Multimedia Subsystem (IMS) is an architectural framework defined by the wireless standards body of the 3rd Generation Partnership Project (3GPP) for delivering IP multimedia services to mobile users. This paper shows the design and implementation of a Horizontal M2M Network Services Platform over an IP Multimedia Subsystem (IMS) using the Message Session Relay Protocol (MSRP). We summarize the protocols and architectures that formed the basis for the creation of our architecture. We provide a detailed description of our architecture design, describing the call flow of the proposed architecture and the entities operating in each process. We also describe the design and implementation process detailing the different tools used, explaining the selection of each component and its importance; also how we designed and implemented the M2M gateway, M2M Application Server, Open IMS Core, business application and M2M devices.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.4A
• /
• pp.356-368
• /
• 2011

While most of the public radio spectrum bands are allocated to licensed users, cognitive radio has been considered as a promising technology for the efficient spectrum utilization. In this new technology, secondary users opportunistically use the temporally underutilized licensed bands as long as they do not give the harmful interference to primary users. In this paper, we focus on the infra-structured network condition in which the cognitive radio network consists of a cognitive radio base station and multiple secondary users. Upon detecting a primary user, the entire cognitive radio network generally switches to another available channel, even if most of the on-going communications still does not interfere with the primary user. Moreover, the network re-entry process on a new channel causes the service disruption of the on-going communications. For this reason, in this paper, we propose a relaying scheme for efficient frequency usage, in which the secondary user out of the interference range of a primary user performs as a relaying node for the secondary user possibly interfering with a primary user. The entire spectrum switching is not required, and thus, we can avoid the service disruption of the on-going communications as much as possible.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.1C
• /
• pp.89-96
• /
• 2012

Since tactical robots are going to be grown and tactical data communications will be more network-centric, the reliability of wireless tactical data networks is going to be very important in the future. However, the connectivity of such wireless tactical data networks can be extremely uncertain in practical circumstances. In this paper, we propose a searching technique to find out the weak boundary area of the network connectivity using a small UAV(unmanned aerial vehicle) which has a simple polling access function to wireless nodes on the ground in wireless tactical data networks. The UA V calculates the network topology of the wireless tactical data networks and coverts it to the Lapalcian matrix. In the proposed algorithm, we iteratively search the eigenvalues and find a minimum cut in the network resulting in finding the weak boundary of the connectivity for the wireless tactical data networks. If a UAV works as a relay nodes for the weak area, we evaluate that the throughput performance of the proposed algorithm outperforms star connection method and MST(minimum Spanning Tree) connection method. The proposed algorithm can be applied for recovering the connectivity of wireless tactical data networks.

• Journal of KIISE:Computing Practices and Letters
• /
• v.13 no.3
• /
• pp.153-164
• /
• 2007

The Access Grid (AG) provides collaboration environments over the IP multicast networks by enabling efficient exchange of multimedia contents among remote users; however, since lots of current networks are still multicast-disabled, it is not easy to deploy this multicast-based multi-party AG. For this problem, the AG provides multicast bridges as a solution by putting a relay server into the multicast networks. Multicast-disabled clients make UDP connections with this relay server and receive forwarded multicast traffics in unicast UDP packets. This solution is facing several limitations since it requires duplicate forwarding of the same packet for each unicast peer. Thus, in this paper, we propose an alternate solution for the multicast connectivity problem of the AG based on the UMTP (UDP multicast tunneling protocol). By taking advantage of flexibilities of UMTP, the proposed solution is designed to improve the efficiency of network and system utilization, to allow reuse of multicast-based AG applications without modification, and to partially address the NAT/firewall traversal issues. To verify the feasibility of proposed solution, we have implemented a prototype AG connectivity tool based on the UMTP, named as the AG Connector.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.3
• /
• pp.21-31
• /
• 2014

In this paper, we propose VLC(visible light communication) based multi-hop multimedia data transmission system. The main contributions and features of the proposed system are as follows. First, the contribution of this research is to develope the LED communication based multi-hop transmission network system which can transmit multimedia data(audio data, video data) with long distance. Second, the developed system has the following features: In transmitter, audio data and video data are transmitted via multi-hops using two channels. The relay in audio channel receives digital audio signal by using photo diode and then transmits the signal to receiver after error checking and amplifying. The receiver receives the encoded audio data via photo diode and then converts to analog audio signal by using decoding and amplifying. The relay in video channel receives video signal by using photo diode and then amplify the video signal using OP-AMP and then transmits the signal to receiver. The receiver amplifies the received signal from photo diode and then sends it to the monitor. The performance evaluation of the proposed system is conducted in the laboratory with fluorescent light source. The results of the performance evaluation confirm that the system can provide high quality multimedia data transmission from transmiter to receiver via multi-hop relays in a long distance while we can see there are differences in the transmitted multimedia(audio and video) quality according to the used LED colors.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.1
• /
• pp.96-107
• /
• 2015

VANET technologies provide real-time traffic information for mitigating traffic jam and preventing traffic accidents, as well as in-vehicle infotainment service through Telematics/Intelligent Transportation System (ITS). Due to the rapid increasement of various requirements, the vehicle communication with a limited resource and the fixed frame architecture of the conventional techniques is limited to provide an efficient communication service. Therefore, a new flexible operation depending on the surrounding situation information is required that needs an adaptive design of the network architecture and protocol for efficiently predicting, distributing and sharing the context-aware information. In this paper, Vehicle-to-Infrastructure (V2I) based on communication between vehicle and a Road Side Units (RSU) and Vehicle-to-Vehicle (V2V) based on communication between vehicles are effectively combined in a new MAC architecture and V2I and V2V vehicles collaborate in management. As a result, many vehicles and RSU can use more efficiently the resource and send data rapidly. The simulation results show that the proposed method can achieve high resource utilization in accordance. Also we can find out the optimal transmission relay time and 2nd relay vehicle selection probability value to spread out V2V/V2I collaborative schedule message rapidly.

• Journal of KIISE:Computing Practices and Letters
• /
• v.15 no.10
• /
• pp.724-739
• /
• 2009

This paper suggests the energy-efficient message delivery scheme and the software platform which exploits the multiple network interfaces of the mobile terminals and GPS in the current mobile devices. The mobile terminals determine the delivery method among 'direct', 'indirect', and 'WAN' based on the position information of itself and other terminals. 'Direct' method sends a message directly to the target terminal using local RAT. 'Indirect' method extends the service area by exploiting intermediate terminals as relay node. If the target terminal is too far to reach through 'direct' or 'indirect' method, the message is sent using wireless WAN technology. Our proposed scheme exploits the position information and, thus, power consumption is drastically reduced in determining handover time and direction. Network simulation results show that our proposed delivery scheme improves the message transfer efficiency and the handover detection latency. We implemented a message platform in a smart phone realizing the proposed delivery scheme. We compared our platform with other typical message platforms from energy efficiency aspect by observing the real power consumption and applying the mathematical modeling. The comparison results show that our platform requires significantly less power.

• The Journal of the Korea Contents Association
• /
• v.18 no.3
• /
• pp.611-625
• /
• 2018

With innovative advances in wireless communication technology, many researches for extending network lifetime in maximum by using energy harvesting have been actively performed on the area of network resource optimization, QoS-guaranteed transmission, energy-intelligent routing and etc. As known well, it is very hard to guarantee end-to-end network delay due to uncertainty of the amount of harvested energy in multi-hop RF(radio frequency) energy harvesting wireless networks. To minimize end-to-end delay in multi-hop RF energy harvesting networks, this paper proposes an energy efficient routing metric based on interference aware and protocol which takes account of various delays caused by co-channel interference, energy harvesting time and queuing in a relay node. The proposed method maximizes end-to-end throughput by performing avoidance of packet congestion causing load unbalance, reduction of waiting time due to exhaustion of energy and restraint of delay time from co-channel interference. Finally simulation results using ns-3 simulator show that the proposed method outperforms existing methods in respect of throughput, end-to-end delay and energy consumption.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.6
• /
• pp.180-187
• /
• 2013

In this paper, we propose a LED communication based multi-hop audio data transmission network system. The main contribution and features of the proposed system are as follows. First, the contribution of this research is to develope the LED communication based multi-hop transmission network system which can transmit audio data signal with long distance via multi-hops. Second, the developed system has the following features: In transmitter, audio data is transmitted after encoding with S/PDIF format via a general LED. The relay receives digital audio signal by using photo diode and then transmits the signal to receiver after error checking and amplifying. The receiver receives the encoded audio data via photo diode and then converts to analog audio signal by using decoding and amplifying. The performance evaluation of the proposed system is conducted in the laboratory with fluorescent light source. The results of the performance evaluation confirm that the system can provide high quality audio transmission from transmiter to receiver via multi-hop relays in a long distance while we can see there are differences in the transmitted audio quality according to the used LED colors.