• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.66-73
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• 2008

At MANET, Broadcasting message transmission makes throughput decrease because all of MANET nodes are participated at retransmitting broadcasting messages. Especially, burst RREQ transmission causes broadcasting message congestion and inter-RREQ transmission delay. In this paper, we propose a RREQ aggregation method applied to the sender node and intermediate node for solving the problem caused by burst RREQ generation. And we analysis performance of the proposed method by examining at the real testbed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.9
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• pp.3120-3137
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• 2021

Small-sized IoT wireless sensing devices can be deployed with small aircraft such as drones, and the deployment of mobile IoT devices can be relocated to suit data collection with efficient relocation algorithms. However, the terrain may not be able to predict its shape. Mobile IoT devices suitable for these terrains are hopping devices that can move with jumps. So far, most hopping sensor relocation studies have made the unrealistic assumption that all hopping devices know the overall state of the entire network and each device's current state. Recent work has proposed the most realistic distributed network environment-based relocation algorithms that do not require sharing all information simultaneously. However, since the shortest path-based algorithm performs communication and movement requests with terminals, it is not suitable for an area where the distribution of obstacles is uneven. The proposed scheme applies a simple Monte Carlo method based on relay nodes selection random variables that reflect the obstacle distribution's characteristics to choose the best relay node as reinforcement learning, not specific relay nodes. Using the relay node selection random variable could significantly reduce the generation of additional messages that occur to select the shortest path. This paper's additional contribution is that the world's first distributed environment-based relocation protocol is proposed reflecting real-world physical devices' characteristics through the OMNeT++ simulator. We also reconstruct the three days-long disaster environment, and performance evaluation has been performed by applying the proposed protocol to the simulated real-world environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.12
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• pp.2392-2400
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• 2015

Zigbee, which was a representative standard technology for dealing low energy and mesh networks in large deployment area such as smart home, smart building, and massive sensor networks, has been developed and deployed for increasing communication area by using Ad hoc method. It has been originally developed based on IEEE 802.15.4 standard so every node needs 48bit unique address defined by IEEE. However, it is absolutely inefficient to assign an unique address to every communication node where it would be deployed through large-scale network area, e.g., smart lighting and massive sensor networks, because there could be variously multiple companies to deploy network infrastructure and they could have different policy to assign node ID. To prevent the problem, this paper proposes a method of dynamic PANID assignment in overall Personal Coordinators, and also proposes a method for addressing PANID conflict problem which could be derived from dynamic PANID assignment.

• Journal of Korea Multimedia Society
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• v.8 no.7
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• pp.974-987
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• 2005

As the ad hoc networks have been received a great deal of attention to not only the military but also the industry applications, some security mechanisms are required for implementing a practical ad hoc application. In this paper, we propose a security architecture in ad hoc networks for the purpose of supporting ID-based public key cryptosystems because of the advantage that ID-based schemes require less complex infrastructure compared with the traditional public key cryptosystems. We assume a trusted key generation center which only issues a private key derived from IDs of every nodes in the system setup phase, and use NIL(Node ID List) and NRL(Node Revocation List) in order to distribute the information about IDs used as public keys in our system. Furthermore, we propose a collaborative status checking mechanism that is performed by nodes themselves not by a central server in ad-hoc network to check the validity of the IDs.

• Journal of KIISE:Databases
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• v.37 no.2
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• pp.121-126
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• 2010

This paper proposes an efficient index scheduling technique for kNN query processing in multiple wireless broadcast channel environment. Previous works have to wait for the next cycle if the required child nodes of the same parent node are allocated in the same time slot on multiple channel. Our proposed method computes the access frequencies of each node of R tree at the server before the generation of the R-tree index broadcast schedule. If they have high frequencies, we allocate them serially on the single channel. If they have low frequencies, we allocate them in parallel on the multiple channels. As a result, we can reduce the index node access conflicts and the long broadcast cycle. The performance evaluation shows that our scheme gives the better performance than the existing schemes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.10 s.101
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• pp.965-972
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• 2005

In this paper, we first review LDPC codes in general and a belief propagation algorithm that works in logarithm domain. LDPC codes, which is chosen for second generation digital video broadcasting standard, are required a large number of computation due to large size of coded block and iteration. Therefore, we presented two kinds of low computational algorithm for LDPC codes. First, sequential decoding with partial group is proposed. It has same H/W complexity, and fewer number of iteration's are required at same performance in comparison with conventional decoder algerian. Secondly, early detection method for reducing the computational complexity is proposed. Using a confidence criterion, some bit nodes and check node edges are detected early on during decoding. Through the simulation, we knew that the iteration number are reduced by half using subset algorithm and computational complexity of early detected method is about $50\%$ offs in case of check node update, $99\%$ offs in case of check node update compared to conventional scheme.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.20-28
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• 2007

Zigbee sensor network base on IEEE802.15.4 has local address of 2 byte on transmit packet data which is pick up the address for each sensor node. Sensor network is requested low power, low cost, many nodes at hues physical area. There for Zigbee is very good solution supporting for next Ubiquitous generation but the Zigbee sensor network has address allocation problem of each sensor node. Is established standard from Zigbee Alliance, to the address allocation method uses Cskip algorithm. The Cskip algorithm use the hazard which allocates an address must blow Hop of the maximum modification and child node number. There is to address allocation and from theoretically it will be able to compose a personal 65536 sensor nodes only actual with concept or space, only 500 degree will be able to compose expansion or the low Zigbee network. We proposed an address allocation method using coordinate value for Zigbee sensor network.

• Journal of the Korea Society of Computer and Information
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• v.10 no.2 s.34
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• pp.187-197
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• 2005

All sensors in Ubiquitous sensor network have to communicate with limited battery If we adopt current authentication, there are difficulties to keep sensor network because heavy calculation in each sensor needs more power and lifetime of sensor could be short relatively because of the effect. This paper suggests network structure which is using RM(RegisterManarer) and AM(AuthenticationManager) to solve power Problem on authentication, and su99ests mutual-authentication protocol with low Power which supports a session key by mutual-authentication. RM and AM manage algorithm with fast calculation to keep the safety by doing key generation. encryption/decryption. authentication instead of each sensor node . Processing time to authenticate sensor node is 2.96$\%$ fast in the same subnet, and 12.91$\%$ fast in different subnet. Therefore. the suggested way Provides expanded lifetime of censor node and is more effective as sensor network size is bigger and bigger.

• The KIPS Transactions:PartC
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• v.10C no.4
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• pp.413-422
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• 2003

An active network is a new generation network based on a software-intensive network architecture in which applications are able to inject new strategies or code into the infrastructure for their immediate needs. Therefore, the secure active node architecture is needed to give the capability defending an active node against threats that may be more dynamic and powerful than those in traditional networks. In this paper, a security enforcement engine is proposed to secure active networks. We implemented an operating engine with security, authentication and a authorization modules. Using this engine, it is possible that active networks are protected from threats of the malicious active node.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.11
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• pp.2069-2074
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• 2006

The Next generation network may describe one integrated network by IP (Internet Protocol) convergence and combining various access technologies. The IP version 6 (IPv6) becomes fundamental protocol and the terminal offered various services is having mobility, multihoming, and intelligent as well as smaller. In this convergence network, which integrate mobile network, broad cast network, and Internet as well as PSTN, can provide all of the service. In this context, we will briefly present that the end node should be required ubiquitous computing and networking. That is to say that we must guarantee the end node in any time, my place, my where, and offer continuously services to the node. As like this, Service Mobility is given if a user can obtain subscribed and personalized services consistently even if connected to a foreign network service provider. In other words, Service mobility allows users to maintain access to their services even while moving or changing devices and network service providers. In this paper, we have to refer technical consideration items to make the service mobility framework.