• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1215-1223
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• 2014

In multi-hop wireless networks, a message transmission path is set up on demand by a route discovery step, where a shortest path is used in general. The shortest path, however, normally uses the nodes near the center area, which causes a high traffic load in that area and reduces the message transmission reliability. We propose a stable routing protocol considering the remaining energy of nodes. Our protocol uses ETX as a link performance estimator and tries to avoid the nodes with smaller energy. By doing this, we can reduce the route failure probability and packet loss. We have evaluated the performance of the proposed protocol using QualNet and compared with AODV and MRFR protocols. The simulation result shows that our protocol has a similar performance as MRFR in terms of end-to-end message reception ratio, average message delay and delay jitter, but outperforms MRFR in terms of traffic load distribution.

• Journal of KIISE:Information Networking
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• v.29 no.3
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• pp.224-232
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• 2002

The routing protocols designed for wired networks can hardly be used for mobile ad-hoc networks due to limited bandwidth of wireless transmission and unpredictable topological change. Recently, several routing protocols for mobile ad-hoc networks have been proposed. However, when these protocols are applied to support real time services like multimedia transmission, they still have problems in ad-hoe networks, where the topology changes drastically. In this paper, we propose a new route selection algorithm which selects the most reliable rouse that is impervious to route failures by topological changes by mobile hosts. For reliable route selection, the concept of virtual zone (stable lone and caution zone) is proposed. The lone is located in a mobile node's transmission range and determined by mobile node's mobility information received by Global Positioning System (GPS). The proposed algorithm is applied to the route discovery procedure of the existing on-demand routing protocol, AODV, and evaluated by simulation in various traffic conditions and mobility patterns.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.6
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• pp.588-594
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• 2010

In a multi-hop wireless sensor network, broadcasting is an elementary operation to support command message sending, route discovery and other application tasks. Broadcasting by flooding may cause serious redundancy, contention, and collision in the network, which is referred to as the broadcast storm problem. Many broadcasting schemes have been proposed to give better performance than simple flooding in wireless sensor network. How to decide whether re-broadcast or not also poses a dilemma between reach ability and efficiency under different host densities. In this paper, we present popular broadcasting schemes, which can reduce re-broadcast packets and improve SRB(Saved ReBroadcast). Simulation results show different levels of improvement over the simple flooding scheme.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.520-524
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• 2007

제한된 전지를 사용하는 노드들로 이루어진 이동 애드혹 네트워크 환경에서 멀티 홉 간의 에너지 효율적인 경로 설정은 매우 중요한 이슈이다. 이러한 문제를 해결하기 위해서 본 논문에서는 이동 애드혹 네트워크 환경에서 자주 사용되는 라우팅 프로토콜 중 하나인 AODV(Ad-hoc On-demand Distance Vector) 라우팅 프로토콜을 기반으로, 네트워크 계층과 MAC계층의 자원을 크로스 레이어 기법을 활용하여 에너지 효율적인 크로스 레이어 라우팅 프로토콜을 제안한다. 네트워크 계층에서의 이웃노드에 관한 상태 정보를 크로스 레이어 기법을 활용하여 MAC 계층의 back-off time을 적절히 조절함으로써 프레임의 충돌을 줄이고, 패킷의 경로를 설정하는데 있어서 신뢰성과 효율성을 부여하기 위한 방법으로 MAC계층의 자원을 활용하여 얻은 Collision-Level을 사용한다. 또한 Collision Level은 패킷 경로 선택에 사용되는 지연시간을 적응성 있게 줄이는 자원으로 사용된다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10A
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• pp.956-963
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• 2008

In a multi-hop wireless ad hoc network broadcasting is an elementary operation to support route discovery, address resolution and other application tasks. Broadcasting by flooding may cause serious redundancy, contention, and collision in the network which is referred to as the broadcast storm problem. Many broadcasting schemes have been proposed to give better performance than simple flooding in wireless ad hoc network. How to decide whether re-broadcast or not also poses a dilemma between reachability and efficiency under different host densities. In this paper, we propose enhanced broadcasting schemes, which can reduce re-broadcast packets without loss of reachability. Simulation results show that proposed schemes can offer better reachability as well as efficiency as compared to other previous schemes.

• Journal of KIISE:Information Networking
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• v.35 no.5
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• pp.409-414
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• 2008

In mobile ad hoc networks, most of on demand routing protocols such as DSR and AODV do not deal with traffic load during the route discovery procedure. To solve the congestion and achieve load balancing, many protocols have been proposed. However, the existing load balancing schemes has only considered avoiding the congested route in the route discovery procedure or finding an alternative route path during a communication session. To mitigate this problem, we have proposed a new scheme which considers the packet bursting mechanism in congested nodes. The proposed packet bursting scheme, which is originally introduced in IEEE 802.11e QoS specification, is to transmit multiple packets right after channel acquisition. Thus, congested nodes can forward buffered packets promptly and minimize bottleneck situation. Each node begins to transmit packets in normal mode whenever its congested status is dissolved. We also propose two threshold values to define exact overloaded status adaptively; one is interface queue length and the other is buffer occupancy time. Through an experimental simulation study, we have compared and contrasted our protocol with normal on demand routing protocols and showed that the proposed scheme is more efficient and effective especially when network traffic is heavily loaded.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2004-2010
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• 2009

The characteristic of the backbond for distribution service in WMNs(Wireless Mesh Networks) is that WMNs has multiple links connected to mesh points and dynamic routing protocol such as AODV to establish routing paths. When the terminal is communicating with the service through new AP, mobile nodes can resume communication by setting only the link between new AP and mobile node in the case of existing WLANs, but WMNs needs path establishment process in multihop networks. Our goal in this paper is to support the seamless communication service by eliminating path establishment delay in WMNs. We present the method that eliminates the handover latency by predicting the location of handover using GPS information and making the paths to their destination in advance. We implement mesh nodes using embedded board that contains proposed handover method and evaluate performance of handover latency. Our experiment shows that handover delay time is decreased from 2.47 to 0.05 seconds and data loss rate is decreased from 20~35% in the existing method to 0~10% level.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.863-866
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• 2010

무선 센서 네트워크의 규모가 커짐에 따라 대규모의 센서 네트워크의 활용에 대한 기대가 커지고 있다. 기존 IEEE 802.15.4 를 이용한 네트워크의 규모에 따른 한계를 극복하기 위해 듀얼 라디오 센서 네트워크에 대한 많은 연구가 진행되고 있다. 듀얼 라디오 센서 네트워크는 단일 라디오를 내장한 전통적인 센서 노드(싱글 라디오 노드)에 듀얼 라디오 인터페이스(IEEE 802.11g, IEEE 802.15.4)를 내장한 센서(듀얼 라디오 노드)를 포함하여 클러스터를 구성한다. 본 논문에서는 이러한 듀얼 라디오 환경에서 효과적으로 동작하는 라우팅 프로토콜을 제안한다. 듀얼 라디오 노드는 네트워크 상에서 클러스터 헤드 역할을 하고 상위 계층을 이루며, 일반 노드는 클러스터 멤버 역할을 하는 하위 계층을 이룬다. 본 논문에서는 각 계층의 네트워크가 나타내는 특징을 이동성이 적거나 높은 네트워크의 특징으로 대입하여, 상위 계층에는 Pro-Active 프로토콜, 하위 계층에는 Re-active 프로토콜이 효과적임을 설명한다. 이를 바탕으로 듀얼 라디오 센서 네트워크에 적합한 라우팅 프로토콜로써 Pro-Active 프로토콜을 대표하는 DSDV 와 Re-Active 프로토콜을 대표하는 AODV 를 조합한 하이브리드 라우팅 프로토콜을 제안한다. 제안한 프로토콜의 성능을 확인하기 위해 센서네트워크 테스트베드를 구성하여 라우팅 복구 시간과 패킷 전송 안정성에 대한 성능을 입증한다.