• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.3
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• pp.109-115
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• 2009

Recently, the relay communication is focused for the power saving and coverage extension of ad-hoc networks. For the high date rate transmission, it is proposed to adapt OFDMA relays. In this paper, we assume the 2 hop cooperative OFDMA relays between the source and the destination. The performance of 3 different relaying methods are derived and compared. We noticed that the selective OFDMA relaying method has the best performance followed by opportunistic OFDMA relaying and repetition-based OFDMA relaying method under the same threshold mutual information rate.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.205-206
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• 2006

In this paper, we have proposed an ad-hoc routing protocol named "RRMR (Reliable and Resilient Multipath Routing)" that is expanded from AODV to acquire multiple path at one time. This protocol needs less overhead to configure data routing paths and the paths are maintained to transmit data stably. To get these advantages, RRMR protocol is constructed by expanding from multipath acquiring and maintaining method based on distance vector method and hop-by-hop routing of AODV.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.167-168
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• 2006

Mobile Ad Hoc Networks (MANETs) has the characteristics such as dynamic network topology, constrained power capacity, constrained wireless bandwidth and quality, etc. For MANETs AODV (Ad-Hoc On-Demand Distance Vector) routing protocol has been proposed. However AODV routing protocol has some inefficiency related to re-routing path establishment corresponding to node's failure. In this paper, we propose a Self-Healing Routing Technique for MANETs that uses the one-hop nodes from the failed node to set up the routing path efficiently. We also include simulation results to show the performance of our method.

• Proceedings of the Korean Society of Computer Information Conference
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• 2014.01a
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• pp.355-356
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• 2014

기존의 MANET 환경에서 동작하는 계층화된 데이터 전송 프로토콜은 각 계층이 독립적인 기능을 수행하기 때문에 노드의 이동 상황에 따라 변하는 네트워크 환경을 잘 반영하지 못하고 있다. 본 논문에서는 라우팅 계층과 MAC 계층 간의 상호 작용을 통하여 MANET의 2-홉 거리에 있는 노드 수를 반영하여 더 우수한 성능을 나타내는 Cross-Layer 모델 기반의 브로트캐스트 기법을 제안한다. 본 논문에서 제안하는 Cross-Layer 모델은 IEEE 802.11 MAC 프로토콜을 수정하여 이동 노드 주위의 상태에 따라 브로드캐스트 패킷을 적응적으로 전송하도록 동작한다.

• Journal of Industrial Technology
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• v.27 no.B
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• pp.37-42
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• 2007

A mobile ad hoc network (MANET) is a kind of wireless ad hoc network. It is a self-configuring network of mobile nodes connected by wireless links. Infostation is a lower cost and low power system that provides very high bit rate with limited coverage. In this study, we propose search and rescue system that combines MANET of climbers with Infostations. A climber shares location information of climbers with other climbers while climbing, and delivers the information to Infostations. This system is an intermittent network due to the mobility of nodes. From the system, we can track the locations of missing climbers. Ultimately, proposed system achieves low cost and reduces memory requirement using Infestations. We also analyze the performance of the proposed system by simulation. From the performance analysis results, we expect that the proposed system will be very useful to early detect climbers' locations in emergency situations in Korea mountain areas.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.3
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• pp.113-121
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• 2019

Algorithms for geographical routing and location update attract the researchers' interests in wireless ad hoc networks. Even though many various schemes have been proposed, most of them cause scalability problem in small groups of nodes. To defeat this problem, flooding algorithm is widely utilized due to low complexity. However, there is no previous research work to evaluate flooding algorithm through implementation instead of simulation. In this paper, we present implementation of flooding algorithm on Raspberry Pi and performance evaluation results.

• Annual Conference of KIPS
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• 2009.04a
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• pp.838-841
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• 2009

본 논문에서는 DSDV 프로토콜을 사용하여 MN의 이동으로 포워딩이 실패하면 smooth handoff방식을 사용하지 않고 바로 애드 혹 라우팅 기법을 통해 이동 노드를 통해 데이터그램을 전달하도록 하는 실험을 수행하였는데, DSDV 라우팅 프로토콜을 사용한 방식의 경우 핸드오프가 발생하지 않은 경우와 거의 같은 성능을 나타냈으며, MN의 개수에 따라서는 전송지연시간이 증가하나 핸드오프 발생간격에는 거의 무관하며 기존의 방식들에 비해 전송지연시간이 작아짐을 확인할 수 있다. 중계 노드의 이동은 DSDV 라우팅 방식의 가장 큰 문제점이지만 중계 노드의 이동속도가 실제로는 5m/sec이내가 대부분이므로 크게 문제되지는 않는다. 이와 같은 연구 결과를 캠퍼스와 같이 제한된 지역에서 활용할 경우 smooth handoff의 속도 지연에 대한 문제를 줄일 수 있을 것으로 예상된다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.3
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• pp.175-183
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• 2008

In wireless sensor networks with ad hoc networking capability, sensor nodes are battery operated and are usually disposable once deployed. As a result, each sensor node senses and communicates with limited energy and, thus, energy efficiency has been studied as a key design factor which determines lifetime of a wireless sensor network, and it is more improved recently by using so-called cross-layer optimization technique. In this paper, we propose and implement a new energy saving mechanism that reduces energy consumption during data collection by controlling transmission power at sensor nodes and then measure its performance in terms of lifetime improvement for the wireless sensor network platform ZigbeX. When every sensor node transmits sensed data to its clusterhead, it controls its transmission power down to as low level as communication is possible, resulting in energy saving. Each sensor node controls its transmission power based on RSSI(Received Signal Strength Indicator) of the packet received from its clusterhead. In other words, the sensor node can save energy by controlling its transmission power down to an appropriate level that its clusterhead safely receives the packet it transmits. According to the repetitive experiment of the proposed scheme on the ZigbeX platform using the packet analyzer developed by us, it is observed that the network lifetime is prolonged by up to 21.9% by saying energy during the data collection occupying most amount of network traffic.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.405-406
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• 2012

A sensor network is composed of a large number of sensor nodes which have sensing, computation and wireless communication capabilities. The sensor node sends such collected data, usually via radio transmitter, to a command center (sink) either directly or through a data concentration center (a gateway). These sensor networks can be used for various application areas such as health, military, home network, managing inventory, monitoring disaster areas and so on. Moreover, owing to the rapid growth of mobile technology, high-performance smartphones are widespread and in increasing cases are utilized as a terminal device. In this paper, we propose a home management system using smartphone and sensor networks.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.91-96
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• 2012

Ad-hoc networks can be used various environment, which it is difficult to construct infrastructures, such as shadowing areas, disaster areas, war area, and so on. In order to support to considerable and various wireless services, more spectrum resources are needed. However, efficient utilization of the frequency resource is difficult because of spectrum scarcity and the conventional frequency regulation. Ad-hoc networks employing cognitive radio (CR) system that guarantee high spectrum utilization provide effective way to increase the network capacity. In CR based wireless ad-hoc networks, cluster-head decides the existence of primary user using sensing information of primary user from each ad-hoc device. However, it is still defective research to decide cluster head among the a lot of ad-hoc devices. So, in this paper, we show the decision method of cluster head in CR based wireless and detection probabilities of primary user based on decision method of cluster head.