• Journal of Advanced Marine Engineering and Technology
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• v.37 no.2
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• pp.199-204
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• 2013

Marine data communications still look for a novel data communication system at sea because of the restriction of bandwidths and costs of current carriers. In order to make the most efficient use of the broadband land carriers at sea, this paper proposes a routing scheme (MCS-NTC) at a marine MANET model. The routing scheme optimizes the route by choosing optimal nodes and carriers among the traditional and land carriers based on normalized transmission characteristics of applications and carriers. The performance is compared with the max-win method (OMH-MW) scheme considering the specific values of transmission characteristics. The result shows that our scheme derives more efficient routes than the previous one in terms of the transmission characteristics such as bandwidth, cost, delay, the number of hops and carriers.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.58-65
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• 2008

This paper presents a new geographic distributed hash table (GDHT) for MANETs or Mesh networks, where virtual geographic protocol is used. In previous wort GDHT is applied to a network scenario based on two dimensional Cartesian coordinate system. Further, logical data space is supposed to be uniformly distributed. However, mobile node distribution in a network using virtual geographic routing is not matched to data distribution in GDHT. Therefore, if we apply previous GDHT to a virtual geographic routing network, lots of DHT data are probably located at boundary nodes of the network or specific nodes, resulting in long average-delay to discover resource (or service). Additionally, in BVR(Beacon Vector Routing) or LCR(Logical Coordinate Routing), because there is correlation between coordinate elements, we cannot use normal hash function. For this reason, we propose to use "geographic hash function" for GDHT that matches data distribution to node distribution and considers correlation between coordinate elements. We also show that the proposed scheme improves resource discovery efficiently.

• Journal of KIISE:Information Networking
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• v.36 no.5
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• pp.405-412
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• 2009

Mobile ad hoc networks (MANETs) allow mobile nodes to communicate among themselves via wireless multiple hops without the help of the wired infrastructure. In the MANET, it is required not only a route setup mechanism that makes nodes not within each other's transmission range communicate but also mechanism in order for a node to auto-configure a unique address. In this paper, we propose an address auto-configuration mechanism when MANET is connected to the Internet via several Internet Gateways and all gateways advertise the same network prefix. By using the proposed mechanism, once a node configures an Internet topologically correct and globally unique IP address, then the node can utilize the configured address even though the node moves within the MANET. Through the simulations, we analyze the performance of our proposed mechanism and, from the simulation results, we show that out proposed mechanism outperforms the existing mechanism.

• The Journal of the Korea Contents Association
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• v.14 no.11
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• pp.16-27
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• 2014

In this paper, we propose an efficient grid based routing scheme using the location information in order to reduce the routing cost in mobile ad-hoc networks. In our proposed scheme, all nodes can be a candidate to forward messages to the specified destination node and reduce the management cost of head nodes because they do not exist. The intermediate nodes determine the next hop relaying messages on the basis of location relations between a node and a grid zone. The proposed scheme explores the routing path considering the direction of a node using the coordinate of a grid zone and neighbor node information. It also maintains the routing path considering connectivities among the nodes. In order to show the superiority of the proposed routing scheme, we compare it with the existing grid based routing scheme in terms of the overhead of message, the success rate of transmission.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8B
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• pp.647-656
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• 2012

TDMA MAC protocol in MANET requires precise network synchronization between nodes though network topology changes continuously due to node mobility and the effect of propagation environment. In this paper we propose in-band cross-layer network synchronization architecture for TDMA-based MANETs. In the proposed architecture TDMA MAC protocol and proactive routing protocol cooperate closely to rapidly detect network partition and merge caused by node mobility and to precisely maintain network synchronization. We also implement the proposed synchronization architecture in OPNET simulator and evaluate the performance of it in various simulation scenarios. Simulation results show that our architecture stably maintains network time synchronization in both network partition and merge situations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3A
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• pp.221-231
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• 2006

TCP is needed as a transport protocol to provide reliable end-to-end message delivery for MANETs in order to achieve a smooth integration with the fixed Internet. Particularly, TCP has its variants, namely TCP-Reno and TCP-Vegas. However, there has been no research work on extensive performance comparison of TCP-Reno and TCP-Vegas over AODV and OLSR. This paper is the first trial to perform the research by using ns-2 simulator. Through the extensive simulations, we found that which to select among routing protocols is more important than which to select among TCP variants, because the performance difference between TCP-Reno and TCP-Vegas over uy selected routing protocol is not so much outstanding. Particularly, TCP-Vegas relies on an accurate BaseRTT estimation in order to decide the sending rate of a TCP Sender. However, it cannot be directly applied to MANET because a route change makes the Base an used over a Previous Path obsolete. Therefore, we propose a technique for improving the performance of TCP-Vegas by considering the route change, and show the performance improvement through simulation study.