• Journal of Industrial Convergence
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• v.7 no.1
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• pp.21-31
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• 2009

Multicast is a network technology for the delivery of information to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the multiple destinations split. This thesis designed a group certificate that can authenticate group information safety between cores based on CBT, proposed a multicast security system that can control some security key.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.8
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• pp.1083-1093
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• 1993

Recently, some applications require the multicast service that transmit messages to multiple destinations in computer communication network enviroment. Multicast service is to send messages to the group which consists of a number of processes. A multicast group is a collection of processes which are destinations of the transmitted messages and these processes may run on one or more hosts. Therefore, it is important to manage each member of process groups in order to provide efficient multicast services. In this paper, we design and implement group management system to support multicast services. Group Management System was designed with Process Group Management System(PGMS) and Host Group Management System(HGMS). We have implemented basic primitives of PGMS, HGMS. Also, membership tree management algorithm is designed and implemented. Membership tree provides the relation of the members of multicast groups and routing Informations.

• Journal of Communications and Networks
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• v.13 no.5
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• pp.511-517
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• 2011

The capacity of wireless ad-hoc networks is analyzed for all kinds of information dissemination based on single and multiple packet reception schemes under the physical model. To represent the general information dissemination scheme, we use (n, m, k)-cast model [1] where n, m, and k (k ${\leq}$ m) are the number of nodes, destinations and closest destinations that actually receive packets from the source in each (n, m, k)-cast group, respectively. We first consider point-to-point communication, which implies single packet reception between transmitter-receiver pairs and compute the (n, m, k)-cast communications. Next, the achievable throughput capacity is computed when receiver nodes are endowed with multipacket reception (MPR) capability. We adopt maximum likelihood decoding (MLD) and successive interference cancellation as optimal and suboptimal decoding schemes for MPR. We also demonstrate that physical and protocol models for MPR render the same capacity when we utilize MLD for decoding.

• Journal of Communications and Networks
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• v.17 no.3
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• pp.241-246
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• 2015

In this paper, we consider a relaying system which employs a single relay in a wireless network with distributed sources and destinations. Here, all source, destination, and relay nodes are equipped with multiple antennas. For amplify-and-forward relay systems, we confirm the achievable sum rate through a joint multiple source precoders and a single relay filter design. To this end, we propose a new linear processing scheme in terms of maximizing the sum rate performance by applying a blockwise relaying method combined with geometric programming techniques. By allowing the global channel knowledge at the source nodes, we show that this joint design problem is formulated as a standard geometric program, which can guarantees a global optimal value under the modified sum rate criterion. Simulation results show that the proposed blockwise relaying scheme with the joint power allocation method provides substantial sum rate gain compared to the conventional schemes.

• The Transactions of the Korea Information Processing Society
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• v.5 no.6
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• pp.1610-1619
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• 1998

The ABR service class provides feedback based traffic control to transport bursty data traffic efficiently. Feedback based congestion control has first been studied to be applied to unicast connections. Recently. several congestion control algorithms for multicast connections have also been proposed as the number of ABR applications requiring multicast increases. With feedback based congestion control, the effectiveness of a traffic control scheme diminishes as propagation delay increases. Especially for a multicast connection, a remote destination may suffer unfair service compared to a local destination due to the delayed feedback. Amelioration of the disadvantages caused by feedback delay is therefore more important for remote destinations in multicast connections. This paper proposes a new switch behavior to provide effective feedback based mathc control for rentoh destinations. The proposed switches adjust the service rate dynamically in accordance woth the state of the downstream, that is, the congestion of the destinaion is immediately controlled by the nearest apstream switch before the source to ramp down the transmission rate of the connection. The proposed switch has an implementation overhead to have a separate buffer for each VC to adjust the service rate in accordance with a backward Rm cell of each VC. The buffer requirement id also increased at intermediate switches. Simulation results show that the proposed switch reduces the cell loss rate in both the local and the remote destinations and slso amelioratd the between the two destinations.

• Journal of the Korean Society for Railway
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• v.5 no.2
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• pp.77-83
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• 2002

In this paper we present a nonlinear programming model for the train seat capacity distribution with a numerical example. The model finds the optimal capacity distribution methods which minimize the sum of the differences between the demands and the seat capacities. Also the model provides the information on the degree of the discrepancy between the demand and the seat capacities. One can use the model as a tool for planning train seat capacity planning.

• Physical Therapy Korea
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• v.14 no.3
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• pp.81-89
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• 2007

The purpose of this study was to utilize the K-MBI (Korean Modified Barthel Index) and subscales of K-MBI in predicting the length of hospital stay (LOS) and the discharge destinations for stroke patients. The study population consisted of 97 stroke patients (57 men and 40 women) admitted to the Seoul National University at the Bundang Hospital. All participants were assessed by K-MBI at admission and discharge after rehabilitation therapy and the information available was investigated at admission. The data were analyzed by using the Mann-Whitney U test, the stepwise multiple regression and the logistic regression. The median LOS was 30 days (mean, 32.8 days; range, 22 to 43 days). The K-MBI score at initiation of rehabilitation therapy (p<.001), the type of stroke and living habits before a stroke were the main explanatory indicators for LOS (p<.05). Within the parameters of K-MBI measured at initiation for rehabilitation, feeding and chair/bed transfer were the explanatory factors for LOS prediction (p<.01). Confidence in the prediction of LOS was 20%. Significant predictors of discharge destination in a logistic regression model were the discharge K-MBI score, sex and hemiplegic side. Dressing in items of discharge K-MBI was the significant predictor of discharge destination. The K-MBI score was the most important factor to predict LOS and discharge destination. Knowledge of these predictors can contribute to more appropriate treatment and discharge planning.

• Journal of Communications and Networks
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• v.8 no.1
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• pp.116-122
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• 2006

Most of the multimedia applications require strict quality of service (QoS) guarantee during the communication between a single source and multiple destinations. This gives rise to the need for an efficient QoS multicast routing strategy. Determination of such QoS-based optimal multicast routes basically leads to a multi-objective optimization problem, which is computationally intractable in polynomial time due to the uncertainty of resources in Internet. This paper describes a network model for researching the routing problem and proposes a new multicast tree selection algorithm based on genetic algorithms to simultaneously optimize multiple QoS parameters. The paper mainly presents a QoS multicast routing algorithm based on genetic algorithm (QMRGA). The QMRGA can also optimize the network resources such as bandwidth and delay, and can converge to the optimal or near-optimal solution within few iterations, even for the networks environment with uncertain parameters. The incremental rate of computational cost can close to polynomial and is less than exponential rate. The performance measures of the QMRGA are evaluated using simulations. The simulation results show that this approach has fast convergence speed and high reliability. It can meet the real-time requirement in multimedia communication networks.

• Korean Journal of Optics and Photonics
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• v.8 no.5
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• pp.431-437
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• 1997

A gradient-index (GRIN) substrate is proposed as a novel signal propagation medium of planar optics. The GRIN substrate provides planar-optics designers not only a 3-dimensional signal propagation space, but also an additional smart optical functioning component like as a diffraction-limited imaging lens. The novel and smart functioning of the GRIN substrate was confirmed by experiment on imaging of an input signal to multiple destinations.

• Journal of Communications and Networks
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• v.14 no.3
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• pp.243-251
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• 2012

Under the power-based capture model, a transmission is successfully received at the destination, even in the presence of other transmissions and background noise, if the received signal-to-interference-plus-noise ratio exceeds a capture threshold. We evaluate the spectral efficiency of simple multi-user channels by combining the basic capture model with a communication-theoretic model. The result is a more refined capture model that incorporates key system design parameters (such as achievable bit rate, target bit error rate, channel bandwidth, and modulation signal constellations) that are absent from the basic capture model. The relationships among these parameters can serve as a tool for optimizing the network performance.