• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1322-1330
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• 1999

The major source of errors in high-speed networks such as Broadband ISDN(B-ISDN) is buffer overflow during congested conditions. These congestion errors are the dominant sources of errors in high-speed networks and result in cell losses. Conventional communication protocols use error detection and retransmission to deal with lost packets and transmission errors. As an alternative, we have presented a method to recover consecutive cell losses using forward error correction(FEC) in ATM(Asynchronous Transfer Mode) networks to reduce the problem. The method finds the lost cells by observing new cell sequence number($SN^{\ast}$). We have used the LI field together with SN and ST fields to consider the $SN^{\ast}$ which provides more correcting coverage than SN in ATM standards. The $SN^{\ast}$ based on the additive way such as the addition of LI capacity to original SN capacity is numbered a repeatedly 0-to-80 cycle. Another extension can be based on the multiplicative way such that LI capacity is multiplied by SN capacity. The multiplicative $SN^{\ast}$ is numbered in a repeatedly 0-to-1025 cycle.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.12
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• pp.2687-2696
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• 2011

A Clustering problem is one of the organizational problems to improve network lifetime and scalability in underwater acoustic sensor networks. This paper propose an algorithm to obtain an optimal clustering solution to be able to minimize a total transmission power for all deployed nodes to transmit data to the sink node through its clusterhead. In general, as the number of nodes increases, the amount of calculation for finding the solution would be too much increased. To obtain the optimal solution within a reasonable computation time, we propose a genetic algorithm to obtain the optimal solution of the cluster configuration. In order to make a search more efficient, we propose some efficient neighborhood generating operations of the genetic algorithm. We evaluate those performances through some experiments in terms of the total transmission power of nodes and the execution time of the proposed algorithm. The evaluation results show that the proposed algorithm is efficient for the cluster configuration in underwater acoustic sensor networks.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.744-761
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• 2016

For about the past decade and a half research efforts into cognitive radio networks (CRNs) have increased dramatically. This is because CRN is recognized as a technology that has the potential to squeeze the most out of the existing spectrum and hence virtually increase the effective capacity of a wireless communication system. The resulting increased capacity is still a limited resource and its optimal allocation is a critical requirement in order to realize its full benefits. Allocating these additional resources to the secondary users (SUs) in a CRN is an extremely challenging task and integer programming based optimization tools have to be employed to achieve the goals which include, among several aspects, increasing SUs throughput without interfering with the activities of primary users. The theory of the optimization tools that can be used for resource allocations (RA) in CRN have been well established in the literature; convex programming is one of them, in fact the major one. However when it comes to application and implementation, it is noticed that the practical problems do not fit exactly into the format of well established tools and researchers have to apply approximations of different forms to assist in the process. In this survey paper, the optimization tools that have been applied to RA in CRNs are reviewed. In some instances the limitations of techniques used are pointed out and creative tools developed by researchers to solve the problems are identified. Some ideas of tools to be considered by researchers are suggested, and direction for future research in this area in order to improve on the existing tools are presented.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.784-795
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• 2016

In this paper, we investigate the resource allocation problem in time-varying heterogeneous wireless networks (HetNet) with multi-homing user equipments (UE). The stochastic optimization model is employed to maximize the network utility, which is defined as the difference between the HetNet's throughput and the total energy consumption cost. In harmony with the hierarchical architecture of HetNet, the problem of stochastic optimization of resource allocation is decomposed into two subproblems by the Lyapunov optimization theory, associated with the flow control in transport layer and the power allocation in physical (PHY) layer, respectively. For avoiding the signaling overhead, outdated dynamic information, and scalability issues, the distributed resource allocation method is developed for solving the two subproblems based on the primal-dual decomposition theory. After that, the adaptive resource allocation algorithm is developed to accommodate the timevarying wireless network only according to the current network state information, i.e. the queue state information (QSI) at radio access networks (RAN) and the channel state information (CSI) of RANs-UE links. The tradeoff between network utility and delay is derived, where the increase of delay is approximately linear in V and the increase of network utility is at the speed of 1/V with a control parameter V. Extensive simulations are presented to show the effectiveness of our proposed scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.11
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• pp.5276-5298
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• 2019

Internet of Things (IoT) based sensor networks have gained unprecedented popularity in recent years. With the exponential explosion of the objects (sensors and mobiles), the bandwidth and the speed of data transmission are dwarfed by the anticipated emergence of IoT. In this paper, we propose a novel heterogeneous IoT model integrated the power line communication (PLC) and WiFi network to increase the network capacity and cope with the rapid growth of the objects. We firstly propose the mean transmission delay calculation algorithm based the 3D Markov chain according to the multi-priority of the objects. Then, the attractor selection algorithm, which is based on the adaptive behavior of the biological system, is exploited. The combined the 3D Markov chain and the attractor selection model, named MASM, can select the optimal path adaptively in the heterogeneous IoT according to the environment. Furthermore, we verify that the MASM improves the transmission efficiency and reduce the transmission delay effectively. The simulation results show that the MASM is stable to changes in the environment and more applicable for the heterogeneous IoT, compared with the other algorithms.

• Journal of Computing Science and Engineering
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• v.6 no.3
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• pp.227-242
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• 2012

Vehicular Ad Hoc Networks (VANETs) are highly dynamic and unstable due to the heterogeneous nature of the communications, intermittent links, high mobility and constant changes in network topology. Currently, some of the most important challenges of VANETs are the scalability problem, congestion, unnecessary duplication of data, low delivery rate, communication delay and temporary fragmentation. Many recent studies have focused on a hybrid mechanism to disseminate information implementing the store and forward technique in sparse vehicular networks, as well as clustering techniques to avoid the scalability problem in dense vehicular networks. However, the selection of intermediate nodes in the store and forward technique, the stability of the clusters and the unnecessary duplication of data remain as central challenges. Therefore, we propose an adaptable destination-based dissemination algorithm (DBDA) using the publish/subscribe model. DBDA considers the destination of the vehicles as an important parameter to form the clusters and select the intermediate nodes, contrary to other proposed solutions. Additionally, DBDA implements a publish/subscribe model. This model provides a context-aware service to select the intermediate nodes according to the importance of the message, destination, current location and speed of the vehicles; as a result, it avoids delay, congestion, unnecessary duplications and low delivery rate.

• Journal of Advanced Navigation Technology
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• v.13 no.2
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• pp.224-230
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• 2009

In the latest date, medical body area networks (MBANs) are emerging as a new technology for diagnosis the human body. MBANs in the health care fields are based on short-range and low-power (e.g. ubiquitous computing) among small-sized devices, and have been used by means of medical services. In this paper, we proposed an emergency message transmission protocol using carrier sense multiple access/time division multiple access in MBANs. This scheme focuses on dependability and power-efficiency. In order to increase the reliability of the transmission, this scheme modified a MCTA slot of IEEE 802.15.3 standard to a SR-MCTA slot. SR-MCTA slot is assigned by MBAN coordinator according to requesting terminal nodes. The method, having the priority of transmission, occurs a collision packet randomly. Results from this proposed solution revel that reservation-based TDMA medical body area network(MBAN) protocol for transmitting emergency message was improved in terms of transmission delay.

• Journal of KIISE:Information Networking
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• v.37 no.1
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• pp.42-49
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• 2010

Because sensor nodes operate with the limited power based on battery which cannot be easily replaced, energy efficiency is a fundamental issue pervading the design of communication protocols developed for wireless sensor networks. In wireless networks, energy efficient MAC protocols can usually be described as being either a contention-based protocol or a schedule-based protocol. It is suitable to use combination of both contention-based protocol and schedule-based protocol, because the strengths and weaknesses of these protocols are contrary to each other. In this paper, in order to minimize energy consumption of sensor nodes and maximize network lifetime, we propose a new MAC protocol called "Tiered-MAC" The Tiered-MAC uses a schedule-based TDMA inside maximum transmission range of sink node and a contention-based CSMA otherwise. Therefore, by efficiently managing the congested traffic area, the Tiered-MAC reduces the unnecessary energy consumption. Based on the ns-2 simulation result, we prove that the Tiered-MAC improves the energy-efficiency of sensor network nodes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.4
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• pp.698-706
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• 2016

In order to move mobile robots to desired locations in a minimum time, optimal control problems have to be solved; however, their analytic solutions are almost impossible to obtain due to robot nonlinear equations. This paper presents a method to get optimal control gains of mobile robots using genetic algorithms. Since the optimal control gains of mobile robots depend on the initial conditions, the initial condition range is discretized to form some grid points, and genetic algorithms are applied to provide the optimal control gains for the corresponding grid points. The optimal control gains for general initial conditions may be obtained by use of neural networks. So the optimal control gains and the corresponding grid points are used to train neural networks. The trained neural networks can supply pseudo-optimal control gains. Finally simulation studies have been conducted to verify the effectiveness of the method presented in this paper.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.461-465
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• 2007

MANET(Mobile Ad hoc Networks) is free-mobility formation of mobile nodes in the wireless networks. Generally, wireless networks has two main type of structures which Tree and Mesh. These general structure is difficult to do which connectivity, redundancy transmit and network continuant. In this paper, we would suggest a new ODDMRP(Ontology Doppler effect-based Dynamic Multicast Routing Protocol) technology for effective MANET which Ontology Doppler effect-based. ODDMRP consist of the parameters for node entropy when using Doppler effect which moving position of round node, moving time, and distribution chart in velocity also it express distance of destination node and property structure organization. It would be used to provide improvement to keep the optimal communication routing and also could be improve network stabilization, and continuation durability of connectivity.