• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7A
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• pp.451-466
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• 2003

Untethered nodes in mobile ad-hoc networks strongly depend on the efficient use of their batteries. In this paper, we propose a new metric, the drain rate, to forecast the lifetime of nodes according to current traffic conditions. This metric is combined with the value of the remaining battery capacity to determine which nodes can be part of an active route. We describe new route selection mechanisms for MANET routing protocols, which we call the Minimum Drain Rate (MDR) and the Conditional Minimum Drain Rate (CMDR). MDR extends nodal battery life and the duration of paths, while CMDR also minimizes the total transmission power consumed per packet. Using the ns-2 simulator and the dynamic source routing (DSR) protocol, we compare MDR and CMDR against prior proposals for power-aware routing and show that using the drain rate for power-aware route selection offers superior performance results.

• ETRI Journal
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• v.34 no.1
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• pp.98-101
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• 2012

The directional medium access control (MAC) protocol improves the throughput of mobile ad hoc networks but has a deafness problem and requires location information for neighboring nodes. In the dual-channel directional MAC protocol [12], the use of omnidirectional packets does not require the exact location of destination node. In this letter, we propose a tone dual-channel MAC protocol with directional antennas to improve the throughput of mobile ad hoc networks. In the proposed MAC protocol, we use a directional CTS and an out-of-band directional DATA tone with a new blocking algorithm to improve the spatial reuse. We confirm the throughput performance of the proposed MAC protocol by computer simulations using the Qualnet simulator.

• Journal of the Korea Society for Simulation
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• v.13 no.2
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• pp.53-63
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• 2004

In ad hoc networks, the link survivability is firstly considered if a routing between two mobile nodes takes place through wireless environments, because all of mobile nodes participating in a connection dynamically move to anywhere. Also, mobile nodes have multi-role to implement a communication without a static system supported by wired networks. Hence, it is difficult that all mobile nodes continuously provide a reliable connection when the nodes operate each role for the connection. Therefore, it is desired to maximize the lifetime of a route as long as possible for the reliable communication. In this paper, we propose a proactive link management scheme that can provide the continuous route supported by the link handover. It consider the wireless link quality and the power lifetime of a node so that the link handover is implemented for the link survivability without disconnecting the route on the communication.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2B
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• pp.69-75
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• 2008

We propose new routing scheme, Cooperative Diversity-based Routing (CDR)which utilize the cooperative space diversity for power saving and for performance enhancement of wireless ad-hoc networks. The end-to-end performance of the proposed routing, CDR, is analyzed based on the Haenggi's link model. The improved performance is compared with Multi-hop Relay Routing (MRR) by analytical methods. When the required outage probability is $1{\times}10^{-3}$ at the destination node in ad-hoc networks with 7 nodes, we noticed that each node can save power consumption by 21.5 dB in average, by using our proposed CDR compared to MRR.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2A
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• pp.107-112
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• 2009

Spectral efficiency of current two-phase cooperative communications protocols is low since in the second time the relay forwards the same signal received from the source to the destination, the source keeps silent in this time. In this paper, we propose a novel cooperative communications protocol where the signal needed to transmit to the destination is sent in both phases, the source and the relay also transmit different signal to the destination thus no loss of spectral efficiency. This protocol performs signal selection based on log-likelihood ratio (LLR) at relay and maximum likelihood (ML) detection at destination. While existing protocols pay for a worse performance than direct transmission in the low SNR regime which is of special interest in ad hoc networks, ours is better over the whole range of SNR. In addition, the proposal takes advantages of bandwidth efficiency, long delay and interference among many terminals in ad hoc network. Simulation results show that the proposed protocol can significantly save total energy for wireless ad hoc networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9A
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• pp.882-888
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• 2010

Vehicular Ad-Hoc Networks (VANETs) using inter-vehicle communication can potentially enhance traffic safety and facilitate many vehicular applications. Therefore, this paper proposes an inter-vehicle routing protocol called Junction-Assisted Routing (JAR) that uses fixed junction nodes to create the routing paths for VANETs in city environments. JAR is a proactive routing protocol that uses the Expected Transmission Count (ETC) for the road segment between two neighbor junctions as the routing paths between junction nodes. Simulation results showed that the proposed JAR protocol could outperform existing routing protocols in terms of the packet delivery ratio and average packet delay.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1537-1540
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• 2004

이동 Ad-hoc 네트워크는 기존의 인프라스트럭쳐 네트워크가 없이 이동 노드들이 자율적으로 다수의 홉을 통해 통신하는 네트워크다. 이동 Ad-hoc 네트워크의 이동 노드는 스스로 호스트나 라우터가 되며 능동적인 연결 설정이 가능하고 네트워크의 참여 또는 이탈이 자유롭고 베터리로 운영되어 에너지원의 공급이 제한되고 무선 망 특성에 따른 잦은 환경 변화에 의해 네트워크의 토폴로지가 자주 변하는 특성을 가진다. 이러한 Ad-hoc 네트워크의 특성 때문에 기존의 고정적인 유선 망 관리에 비해 Ad-hoc 네트워크에서의 망 관리는 더 힘들고 어려운 연구분야다. 특히, 기존의 중앙 집중식 망 관리와 같은 구조는 Ad-hoc 네트워크의 특성에 적합하지 않다. 이 논문에서는 Ad-hoc 네트워크의 특성에 맞는 자동적이고 적응력 있는 지적 망 관리 구조를 제시한다. 제시한 관리 구조는 JMX(Java Management Extensions)와 Mobile Agent 프레임웍을 이용한 분산 망 관리 구조이다.

• The Journal of the Korea Contents Association
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• v.8 no.7
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• pp.43-52
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• 2008

The AODV routing algorithm in a mobile ad-hoc networks broadcasts RREQ packet to find a route from a source to a destination. An attacker node may intercept a RREQ packet and attack by falsifying a field in that packet. In this paper, we propose a simply modified method which can protect a routing table from an attack to falsify the hop count field in the RREQ packet. When establishing a connection between a source and a destination, we update routing table of each node on the connection based on minimum delay instead of minimum hop count. By doing this, we can protect routing table from an attack to falsify a hop count Our simulation is implemented in Network Simulator(NS-2). We analyze how an attacker affects the mobile ad-hoc networks. The result of the simulation shows that the proposed mechanism transfers a data securely.

• Journal of KIISE:Information Networking
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• v.29 no.3
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• pp.314-323
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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 theme protocols are applied to support real time services like multimedia transmission, they still have problems in ad-hoc networks, where the topology changes drastically. In this paper, we propose a new route selection algorithm which selects the most reliable route that is impervious to route failures by topological changes by mobile hoots. For reliable route selection, the concept of virtual zone (stable zone and caution zone) is proposed. The zone is located in a mobile node'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.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.6
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• pp.205-212
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• 2003

Because a wireless ad hoc network does not have fixed infrastructure, a call admission control approach researched in a wireless network is not feasible to this network. In this paper, we propose call admission control scheme to support this problem and the burst handoff traffic due to group mobility in a wireless ad hoc network. This scheme is an adaptive guard channel scheme which adapt the number of guard channels in each MBS(mobile base station) according to the current estimate of the potential handoff call rate derived from the number of ongoing calls within the coverage area of an MBS that initiate group handoff in a wireless ad hoc network. Our simulation studies are performed for comparisons of the proposed scheme with the other channel allocation schemes. Simulation results show that the proposed scheme efficiently reduces handoff call blocking probability in wireless ad hoc networks.