• Journal of the Korea Society for Simulation
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• v.14 no.4
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• pp.107-116
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• 2005

The multi user communications that is called as the multicast service should be applied into the evolving mobile networks. In this paper, we propose a fast multicast management scheme for mobile terminals in HMIPv6 (Hierarchical Mobile IPv6) based mobile networks. In HMIPv6 based mobile networks, we consider the mobile terminal mobility that the multicast management scheme during mobile handover is used for the multicast routing changing. The changing impact to the multicast routing Is determined from handovers in intra AR, and in inter AR or MAP. In this paper, we propose multicast supporting schemes that the tunneling scheme is used in intra AR handover, and the previous subscription scheme is used in inter AR handover for considering the changing impact of the multicast routing.

• Journal of Electrical Engineering and information Science
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• v.2 no.5
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• pp.33-39
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• 1997

In this paper we proposed a new traffic load shedding scheme which maximizes the throughput of traffic control by decreasing the load of the hot-spot cell using minimum load cell selection (MLCS) algorithm and deployed control flow of calls to define characteristic for hadoff region. we compared the performance of the random shedding approach with that of the proposed algorithm. The results of simulation show that MLCS algorithm minimizes the cal blocking rate under a high-density traffic compared to the random shedding scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.9
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• pp.1573-1595
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• 2011

In this paper, the outage performance of multiuser multiple-input single-output (MISO) systems exploiting joint spatial and multiuser diversities is investigated for Rayleigh fading channels with outdated feedback. First, we derive closed-form exact outage probabilities for the joint diversity schemes that combine user scheduling with different spatial diversity techniques, including: 1) transmit maximum-ratio combining (TMRC); 2) transmit antenna selection (TAS); and 3) orthogonal space-time block coding (OSTBC). Then the asymptotic outage probabilities are analyzed to gain more insights into the effect of feedback delay. It is observed that with outdated feedback, the asymptotic diversity order of the multiuser OSTBC (M-OSTBC) scheme is equal to the number of transmit antennas at the base station, while that of the multiuser TMRC (M-TMRC) and the multiuser TAS (M-TAS) schemes reduce to one. Further by comparing the asymptotic outage probabilities, it is found that the M-TMRC scheme outperforms the M-TAS scheme, and the M-OSTBC scheme can perform best in the outage regime of practical interest when the feedback delay is large. Theoretical analysis is verified by simulation results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6B
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• pp.921-929
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• 2010

Group communication that involves the setup of a list of users has been a topic of interest in mobile industry. Push to Talk over Cellular (PoC), a group communication service for cellular phone network, is a type of half duplex communications that allows a single person to reach an active talk group without making several calls, but a single button press. Based on this service, we build a new protocol called Push to Talk over Mobile Wimax that uses group communication service in 802.16e network. Also, weper formed simulation to verify and evaluate performance of the designed service in Mobile Wimax network. From the results of performance evaluation, network administrators can evaluate the stability of network and make a better of network's shortcoming and have decision to build the robust network.

• Journal of Ubiquitous Convergence Technology
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• v.1 no.1
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• pp.35-41
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• 2007

In mobile ad-hoc wireless networks, one of the most important challenging issues is how to conserve energy, maximizing the lifetime of route(networks) in the view points of both power and mobility of nodes. However, many transmission methods presented in the previous works can not satisfy these two objectives simultaneously. To obtain these two goals, in this paper we propose an architecture to support power saving transmission services with route stability in mobile ad-hoc wireless networks. The proposed architecture consists of two parts, the underlying route stability method to support route(network) lifetime and the power saving transmission methods. The performance evaluation of the proposed architecture is achieved via simulation and analysis.

• Journal of Digital Contents Society
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• v.14 no.3
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• pp.357-365
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• 2013

The popularization of smart phones changes the usage patterns of mobile communication from voice-centric to data-centric communication. The demand for wireless data communications is rapidly increasing, and thus the need for expanding infrastructure for mobile communication is also rapidly increasing. In this paper, we propose a scheme for reducing the cost for the mobile communication infrastructure by exploiting opportunistic networks in dissemination of multimedia contents. By using this scheme, the large portion of the cost for mobile communication infrastructure could be saved, and the need of users for multimedia contents could be also fulfilled. Our scheme is evaluated using agent-based simulations. The simulation results show that about 70% of mobile communication can be replaced with the data communication through opportunistic networks.

• ETRI Journal
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• v.18 no.2
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• pp.53-60
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• 1996

Blind equalization is a technique for adaptive equalization of a communication channel without the aid of training sequences. This paper proposes a new blind equalization algorithm. The advantage of the new algorithm is that it has the lower residual error than the GA (proposed by Godard) and Sign_GA (proposed by Weerackody et al.). The superior performance of the proposed algorithm is illustrated for the 16-QAM signal constellation. A Rummler channel model is assumed as a transmission medium. The performance of the proposed algorithm is compared to the GA, Sign_GA and Stop & Go Algorithm (SGA). The simulation results demonstrate that an improvement in performance is achieved with the proposed equalization algorithm.

• Journal of Ubiquitous Convergence Technology
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• v.2 no.2
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• pp.97-104
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• 2008

In this paper, we demonstrate the boundary effect of a deployed regions on the effective coverage of a mobile node. A node coverage area is not uniform throughout the entire deployed region. Assuming a uniform coverage can result in significant error in calculations. In this study, we analyze the behavior of a node's coverage area as a function of its transmission range throughout the entire deployed region. Using this analysis, a mathematical model for effective coverage in mobile wireless communications is created. The mathematical model considers the effect of the deployed regions boundaries on the coverage area of a mobile node. Lastly, we present simulation results to verify the analytical model and to compare this model with that of a uniform coverage.

• Journal of KIISE:Computing Practices and Letters
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• v.6 no.4
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• pp.411-420
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• 2000

The performance of soft handoffs of CDMA mobile communication systems is potentially determined by several factors such as handoff-related system parameters (T_ADD, T_DROP, T_COMP, T_TDROP), mobile stations' mobility, service areas, capacity of base stations. Due to the importance of handoffs in mobile communications, several methods have been proposed and tested through computer simulations to prove the efficiency of proposed methods. Different assumptions on the above mentioned factors often produce different simulation results. Therefore, the credibility of a simulation result is directly determined by the objectivity of the assumptions made by the simulation. This paper proposes a new soft handoff method that controls handoff delay time based on a mobile station's speed, and compares it with the current method of CDMA systems. The simulation results showed that the new method is much more efficient for mobile stations that are free in their moving direction and space than for those restricted in their moving direction and space. In addition, the results showed that even the same handoff method may produces different simulation results depending on whether a service area is modeled as two-dimensional space or three-dimensional space. These results indicate the importance of suitable models of user mobility, especially the movement types and space allowed for mobile stations, which have been neglected in simulation studies of mobile communications.

• Korean Management Science Review
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• v.25 no.2
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• pp.43-55
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• 2008

Contingent valuation method(hereafter CVM) is generally believed to be one of the most popular methods used for quantifying the value of non-market goods or services particularly by asking respondents of willingness to pay. This study deals with how to use CVM in calculating the value of mobile telephone service by suggesting methodology of estimation and eliminating biases. This study represents an attempt to estimate the WTP(Willingness To Pay) of the mobile telephone service using the face-to-face interview which is the qualitative technique is used. In this study, by using the single bound dichotomous choice model(SBDC) in order to analyze the valuation of mobile telephone service, WTP was estimated. Also we analyze the factors to pay for mobile service in which it becomes the important factor of demanding services. We used logit model. In order to provide robust estimates of WTP, we have used the Method of Montecarlo Simulation. Consequently, consumers showed that WTP about the mobile communications service is generally high. And it could know that the WTP will fell down as the specialized knowledge about the mobile communications frequency was high. It will be able to become the important part to not only the business carrier but also the policy maker to estimate the economic value of mobile telephone service.