• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.3
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• pp.491-497
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• 2012

Network coding is that the nodes can combine and mix the packets rather than merely forward them. Therefore, network coding is expected to improve throughput and channel efficiency in the wireless network. Relevant researches have been carried out to adapt network coding to wireless multi-hop network. In this paper, we designed the network coding for bidirectional traffic service in routing layer and IP layer of Ad-hoc network. From the simulation result, the traffic load and the end to end distance effect the performance of the network coding. As end to end distance and the traffic load become larger, the gain of network coding become more increased.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.65-70
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• 2013

In this paper, we propose a multi-hop cooperative transmission protocol to obtain energy savings in static wireless networks. Each terminal in the network is equipped with a single antenna and each receiver uses equal gain combining technique (EGC) to combine received signals. We also propose a power allocation strategy which optimizes the total transmit power at each stage. Monte-Carlo simulations are presented to evaluate and compare performance of the proposed protocol with the multi-hop direct transmission (MDT) and the cooperative routing protocol proposed by Khadani [8], in terms of the average total transmit power and the average number of required stages.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.9
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• pp.751-764
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• 2013

In cognitive radio ad-hoc networks, common control channel overload and packet collisions are occured due to indiscriminate broadcasting of control packets. So that the path reliability is reduced and control channel is easily saturated. In this paper, we propose a new routing algorithm considering the probability of appearance of primary user and channel status of neighbor nodes. When the source node needs to transmit a data packet to the destination, it performs route discovery process by exchanging control messages using a control channel in ADOV CR Ad-hoc networks. If any intermediate node doesn't have common data channel with previous node to transmit data, it doesn't rebroadcast control packet. And if it has common data channels with previous node, each node determines channel contribution factor with the number of common channels. Based on the channel contribution factor, each node performs different back-off broadcasting. In addition, each node controls control packet flooding by applying to proposed advanced mode using such as number of available channels and channel stability. With the proposed method, the number of control packets to find the data transmission path and the probability of collision among control packets can be decreased. While the path reliability can be increased. Through simulation, we show that our proposed algorithm reduces packet collisions in comparison with the traditional algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.8A
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• pp.569-580
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• 2003

One of the important advantages of multichannel switches is the incorporation of inherent fault tolerance into the switching fabric. For example, if a link which belongs to the multichannel group fails, the remaining links can assume responsibility for some of the traffic on the failed link. On the other hand, if faults occur in the switching elements, it can lead to erroneous routing and sequencing in the multichannel switch. We investigate several fault localization algorithms in multichannel crossbar ATM switches with a view to early fault recovery, The optimal algorithm gives the best performance in terms of time to localization but is computationally complex which makes it difficult to implement. We develop an on-line algorithm which is computationally mote efficient than the optimal algorithm. We evaluate its performance through simulation. The simulation results show that performance of the on line algorithm is only slightly sub-optimal for both random and bursty traffic. Finally a fault recovery algorithm is described which utilizes the information provided by the fault localization algorithm.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.115-117
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• 2006

IEEE 802.11 표준은 채널 상태에 따라 다양한 전송 속도를 지원하며, 무선랜 환경에서 이러한 특성을 활용하는 연구들이 진행되어 왔다. 그러나, 모바일 애드 혹 네트워크 환경에서 다중전송속도를 활용하는 연구는 거의 이루어지지 않았다. 본 논문은 모바일 애드 혹 네트워크에서 동적으로 다중전송속도를 활용하여 채널 효율을 높이는 알고리즘을 제안한다. 제안 기법은 MAC 계층과 네트워크 계층 중간에 위치하며 각 계층에 독립적으로 동작한다. 라우팅 프로토콜에서 결정한 다음 홉에 더불어, 제안 기법은 더 빠른 전송 속도를 갖는 중계 경로를 탐색한다. 또한, 패킷의 크기에 따라 경쟁 부하를 고려하여 선택적으로 전송 경로를 변경한다. 모의 실험을 통한 성능 평가는 제안 기법의 우수한 성능을 입증한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11B
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• pp.981-988
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• 2008

In this paper, the efficient AODV routing algorithm in MANET is proposed. Because transmission channel has a high error rate and loss in MANET, the number of hops can't be regarded as an absolute network metric. After measuring FER periodically at the data link layer using cross-layer design, the scheme that every node forwards the weight of link status in the reserved field of AODV protocol is used. In order to find the efficient route, we design AODV to be able to select an optimal route that has a good channel status by evaluating the sum of weight. The proposed AODV improves throughput, routing overhead and average end-to-end delay in comparison with the generic AODV.

• Journal of KIISE:Information Networking
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• v.36 no.4
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• pp.286-296
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• 2009

A major challenge in next generation optical Internet (NGOI) networks based on dense-wavelength division multiplexing (DWDM) is the provision of guaranteed quality-of-service (QoS) for a wide variety of multimedia applications. One of the critical issues in NGOI is the routing and wavelength assignment problem that is embossed as very important and plays a key role in improving the global efficiency for capacity utilization. But the previous researches had the delay problem, and the path routed by higher priority nodes may be congested and interfere with potential future multicast session requests. To overcome these problems, in this research we suggest a Priority-based Minimum Interference Path Multicast Routing (PMIPMR) algorithm, a new routing algorithm which finds alternative routes based on node priorities and Virtual Source (VS) nodes that has both splitting and wavelength conversion, and then chooses a path that does not interfere with potential future multicast session requests when congestions occur in the network. The PMIPMR algorithm reduces blocking rate significantly and increases the wavelength utilization by avoiding congestion in future multicast session requests.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.223-225
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• 2005

센서네트워크에서 이동물체의 경로 추적과 같이 실시간으로 패킷이 목적노드에 도착하여야 데이터가 유효한 응용의 경우에는 패킷 전송의 실시간을 보장할 수 있는 전송경로설정이 필요하다. 본 논문에서는 패킷을 전송하는데 있어서 지연시간을 증가시키는 요소인 혼잡상황과 낮은 링크 퀄리티를 가지는 경로를 회피함으로 전송지연시간을 최소로 줄이는 전송경로 설정 기법을 제안한다 네트워크의 위상에 따라 노드마다 다른 양상을 보이는 채널 부하도를 효과적으로 측정하고 네트워크의 혼잡상황을 판단하는 기준으로 삼는다. 이와 함께 링크의 전송 성공률을 이용하여 이웃 노드들의 전송경로 선택의 적합도를 계산하고 확률적으로 경로를 선택한다.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.395-398
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• 2011

현대 정보전에서 Ad-hoc 네트워크는 전술 네트워크를 가능할 수 있게 하는 주요 통신 기술이다. 전장 환경에서 노드 파괴나 이동으로 인해 링크실패가 빈번하게 발생되며, 이를 자율적으로 복구할 수 있는 기능을 지녀야만 한다. 그러나 무선링크의 한정된 자원 사용하기 때문에 빈번한 라우팅 트래픽은 네트워크의 자원을 공유하는 데이터 패킷 수신율이나 지연시간에 영향을 줄 수 있다. 본 논문에서는 전술 환경에서 무선 채널의 불규칙에 따른 영향과 이로 인한 문제점을 지적하고 경로 복구 지연시간을 최소화 하며 제한된 무선 링크의 가용 대역폭을 효율적으로 활용할 수 있는 방법을 제안한다.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.05d
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• pp.685-689
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• 2002

Ad hoc 네트워크에서 클러스터 구성은 채널의 효율적 사용, 제어메시지의 교환부하 감소, 이동성 관리 용이, 그리고 QoS라우팅 지원등의 이점을 지닌다. 이런 이유로 인해 클러스터 구조는 자주 변경되지 않아야 하고, 노드의 이동성을 반영하여 클러스터를 구성하여야 한다. 그러나 기존의 클러스터 구성에 관한 연구에서는 노드의 이동성을 고려하지 않고 있으며, 이동성을 고려하는 경우에는 이동속도만을 고려하여 클러스터를 구성함으로써 클러스터의 잦은 변경을 유발한다. 이에 본 논문은 단위 시간당 클러스터 변경 횟수, 현재 클러스터에 체류한시간, 그리고 평균적으로 클러스터에 체류한 시간을 이용하여 이동성을 고려한다. 또한 라우팅 효율성을 위해, 차수도 고려하여 클러스터를 구성한다. 그리고 클러스터 구성절차의 적절한 수행횟수를 보장하기 위하여 LCC[4]의 수정된 클러스터 구조 유지전략을 제공한다.