• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.534-539
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• 2005

The key in wireless sensor networks, which consist of a number of sensor nodes, is an energy efficiency. Many routing protocols have been proposed for prolonging network lifetime and reducing traffic in wireless sensor networks. Wireless sensor networks usually use wireless ad-hoc network protocols for routing, but these protocols are not well-suited for wireless sensor networks due to many reasons. In this paper, RM-flooding protocol is proposed for reducing routing overhead occurred when packet flooding. The nodes using this routing protocol can consume the limited energy effectively, and exchange information with remote nodes usulg information receiving from multipath. So, RM-flooding prolongs the network's lifetime.

• Journal of KIISE
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• v.45 no.3
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• pp.195-199
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• 2018

Recently, with increasing scale of internet of Things (IoT), a large amount of data are generated and various services using such data are emerging. Therefore, a protocol suitable for IoT environment that can efficiently process / transmit big data is needed. MQTT is a lightweight messaging protocol for IoT environment. Although MQTT protocol can use TLS to provide security, it has a problem in that handshake and packet overhead will increase when TLS is used. Therefore, this paper proposed as Secure_MQTT protocol. It can provide stronger security by using lightweight encryption algorithm for MQTT protocol.

• The Journal of the Korea Contents Association
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• v.2 no.3
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• pp.119-126
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• 2002

The QoS(Quality of Service) guarantee mechanism is one of critical issues in the wireless network. Real-time applications like VoIP(Voice over IP) in All-IP networks need smooth handoffs in order to minimize or eliminate packet loss as a Mobile Host(MH) transitions between network links. In this paper, we design a new multicasting algorithm using DB(Dynamic Buffering) mechanism for Mobile-IPv6. A key feature of the new protocol is the concepts of the DB and MRA(Multicast Routing Agent) to reduce delivery path length of the multicast datagram. Particularly, the number of tunneling and average routing length of datagram are reduced relatively, the multicast traffic load is also decreased.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.4
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• pp.529-546
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• 2010

Greedy forwarding is the key mechanism of geographic routing and is one of the protocols used most commonly in wireless sensor networks. Greedy forwarding uses 1-hop local information to forward packets to the destination and does not have to maintain the routing table, and thus it takes small overhead and has excellent scalability. However, the signal intensity reduces exponentially with the distance in realistic wireless sensor network, and greedy forwarding consumes a lot of energy, since it forwards the packets to the neighbor node closest to the destination. Previous proposed greedy forwarding protocols are the sender-based greedy forwarding that a sender selects a neighbor node to forward packets as the forwarding node and hence they cannot guarantee energy efficient forwarding in unpredictable wireless environment. In this paper, we propose the receiver-based greedy forwarding called RGF where one of the neighbor nodes that received the packet forwards it by itself. In RGF, sender selects several energy efficient nodes as candidate forwarding nodes and decides forwarding priority of them in order to prevent unnecessary transmissions. The simulation results show that RGF improves delivery rate up to maximum 66.8% and energy efficiency, 60.9% compared with existing sender-based greedy forwarding.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.9
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• pp.358-365
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• 2003

To support Internet traffic efficiently over ATM networks, Guaranteed Frame Rate(GFR) has been proposed in the ATM Forum. GFR provides minimum rate guarantees to VCs and allows any excess bandwidth in the network to be shared among the contending VCs in a fair manner. In this paper, we proposed a new fuzzy logic based buffer management algorithm that provides MCR guarantee and fair sharing to GFR VCs. A key feature of proposed algorithm is its ability to accept or drop a new incoming packet dynamically based on buffer condition and load ratio of VCs. This is achieved by using fuzzy logic controller for the production of a drop factor. Simulation results show that proposed scheme significantly improves fairness and TCP throughput compared with previous schemes.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.1
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• pp.20-24
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• 2009

sensor node work limited energy. It is undesirable or impossible to replace the batteries that are depleted of energy because of characteristics of the sensor network. Due to the specific energy constrained environment, MAC design for sensor networks generally has to take energy consumption as one of its primary concerns. But in sensor networks, latency has been a key factor affecting the applicability of sensor networks to some delay-sensitive applications. Therefore, we propose MAC protocols based DSMAC in this paper. Which is able to dynamically change the sleeping and duty cycle of sensors is adjusted to adapt to packet amounts in buffer. Proposed MAC has energy efficiency and low latency, compared DSMAC.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1435-1440
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• 2014

Nodes in WSNs must operate under limited energy resource. Controlling access to the channel in WSNs plays a key role in determining channel utilization and energy consumption. This paper introduces a priority-based time slot allocation protocol for hybrid TDMA/CSMA MAC in WSNs. This protocol combines both TDMA and CSMA techniques while introducing prioritization by (m,k)-firm constraint. The performance of this protocol is obtained through simulations for various number of nodes and show significant improvements in delay and packet delivery ratio compared to S-MAC.

• ETRI Journal
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• v.38 no.1
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• pp.9-17
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• 2016

We demonstrate a time- and wavelength-division multiplexed passive optical network system employing a vertical-cavity surface-emitting laser array-based optical line terminal transceiver and a tunable bidirectional optical subassembly-based optical network terminal transceiver. A packet error-free operation is achieved after a 40 km single-mode fiber bidirectional transmission. We also discuss an arrayed waveguide grating, a photo detector array based on complementary metal-oxide-semiconductor photonics technologies, and low-cost key devices for deployment in access networks.

• Journal of Communications and Networks
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• v.14 no.5
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• pp.578-587
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• 2012

One of the key elements in the emerging, packet-based long term evolution (LTE) cellular systems is the deployment of multiple femtocells for the improvement of coverage and data rate. However, arbitrary overlaps in the coverage of these femtocells make the handover operation more complex and challenging. As the existing handover strategy of LTE systems considers only carrier to interference plus noise ratio (CINR), it often suffers from resource constraints in the target femtocell, thereby leading to handover failure. In this paper, we propose a new efficient, multi-objective handover solution for LTE cellular systems. The proposed solution considers multiple parameters like signal strength and available bandwidth in the selection of the optimal target cell. This results in a significant increase in the handover success rate, thereby reducing the blocking of handover and new sessions. The overall handover process is modeled and analyzed by a three-dimensional Markov chain. The analytical results for the major performance metrics closely resemble the simulation results. The simulation results show that the proposed multi-objective handover offers considerable improvement in the session blocking rates, session queuing delay, handover latency, and goodput during handover.

• The Transactions of the Korea Information Processing Society
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• v.4 no.11
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• pp.2701-2710
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• 1997

Recursive circulant graph has recently developed as a new model of multiprocessors, and drawn considerable attention to supercomputing, In this paper, we investigate the routing of a message i recursive circulant, that is a key to the performance of this network. On recursive circulant network, we would like to transmit m packets from a source node to a destination node simultaneously along paths, where the ith packet will traverse along the ith path $(o{\leq}i{\leq}m-1)$. In oder for all packets to arrive at the destination node quickly and securely, the ith path must be node-disjoint from all other paths. For construction of these paths, employing the Hamiltonian Circuit Latin Square(HCLS), a special class of $(n{\times}n)$ matrices, we present $O(n^2)$ parallel routing algorithm on recursive circulant network.