• Journal of the Korea Society of Computer and Information
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• v.11 no.3
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• pp.1-10
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• 2006

It is widely accepted that the coverage with high user densities can only be achieved with small cell such as micro- and pico-cell. The smaller cell size causes frequent handovers between cells and a decrease in the permissible handover Processing delay. This may result in the handover failure. in addition to the loss of some Packets during the handover. In these cases. re-transmission is needed in order to compensate errors, which triggers a rapid degradation of throughput. In this paper, we propose a new handover scheme in the next generation mobile communication systems, in which the handover setup process is done in advance before a handover request by predicting the handover cell based on mobile terminal's current position and moving direction. Simulation is focused on the handover failure rate and Packet loss rate. The simulation results show that our proposed method provides a better performance than the conventional method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2A
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• pp.26-33
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• 2005

Exact prediction of resource demands for future calls enhances the efficiency of the limited resource utilization in resource reservation methods for potential calls in wireless IP networks. In this paper, we propose a LMS-Wiener resource(bandwidth) prediction for future handoff calls, and then an the proposed method is compared with an existing Wiener-based method in terms of prediction error through our simulations. In our simulations, we assume that handoff call arrivals follow a non-Poisson process and each handoff call has an non-exponentially distributed channel holdingtime in the cell, considering that handoff call arrival pattern is not Poisson distribution but non-Poisson for long periods of time in wireless picocellular IP networks. Simulation results show that the prediction error in the proposed method converges to the lower value while in an existing method increase as time is passed. Therefore we may conclude that the proposed method improves the efficiency of resource utilization by more exactly predicting resource demands for future handoff calls than an existing method.

• The KIPS Transactions:PartC
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• v.9C no.3
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• pp.385-398
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• 2002

To accommodate the increasing number of mobile terminals in the limited radio spectrum, wireless systems have been designed as micro/picocellular architectures for a higher capacity. This reduced coverage area of a cell has caused a higher rate of hand-off events, and the hand-off technology for efficient process becomes a necessity to provide a stable service. Population-based Bandwidth Reservation(PBR) Scheme is proposed to provide prioritized handling for hand-off calls by dynamically adjusting the amount of reserved bandwidth of a cell according to the amount of cellular traffic in its neighboring cells. We analyze the performance of the PBR scheme according to the changes of a fractional parameter, f, which is the ratio of request reservation to the total amount of bandwidth units required for hand-off calls that will occur for the next period. The vague of this parameter, f should be determined based on QoS(Quality of Service) requirement. To meet the requirement the value of Parameter(f) must be able to be adjusted dynamically according to the changing traffic conditions. The best value of f can be determined by a function of the average speed of mobile stations, average call duration, cell size, and so on. This paper considers the average call duration and the cell size according to the speed of mobile stations. Although some difference exists as per speed, in the range of 0.4 $\leq$ f $\leq$ 0.6, Blocking Probability, Dropping Probability and Utilization show the best values.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.471-480
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• 2000

With the limited wireless resources, various traffic in the cellular system is served based on micro-cell or pico-cell structure. The rapid increase in the number of mobile users results in the frequent handoff which is becoming a critical issue. In this paper, we propose a channel allocation scheme to reduce the probability of handoff failure. In this scheme, we provide a guard channel for each service to handle the handoff processes. It maintains the low probability of failure in handoff calls. To prevent the performance degradation due to the traffic variation, we use a channel arbitration method that adaptively manages the number of channels based on the call density. We evaluated the performance in terms of the initial call blocking probability and the handoff call blocking probability for various traffic and motility. We found that the proposed scheme keeps the lower probability of call blocking through the efficient channel arbitration than other suggested methods even for the irregular traffic conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.770-777
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• 2007

Smaller cell size in the micro-cell or pico-cell structure brings about more frequent hand-overs between cells, and higher speed movement of the mobile terminal makes short the permissible time interval for executing these hand-over procedures. In this situation the hand-over failure may occur or some packets may be lost during the hand-over. Moreover a rapid degradation of throughput is triggered by packet re-transmission for compensating such errors. The QoS (Quality of Services) of mobile multimedia applications with higher bits rate requirements and higher speed mobility are severely affected by even shot service interruption. This paper proposes a new hand-over scheme to provide seamless services in the next generation mobile communication systems. Simulation is done to evaluate the performance of the proposed scheme based on its hand-over failure rate and packet loss rate.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.1299-1302
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• 2001

인터넷의 폭발적인 증가와 다양한 무선 서비스에 대한 수요 증가에 따라 용량이 크고, 데이터 전송 속도가 빠르며, 멀티미디어를 지원 할 수 있는 무선 인터넷 서비스가 필요하게 되었다. 또한 증가하는 사용자수를 수용하기 위해서 마이크로/피코 셀(micro/pico cell)을 도입하게 되었고, 이로 인하여 빈번한 핸드오프가 발생하게 되었다[1,2]. 이를 해결하기 위해서 MRSVP(Mobile Resource reservation protocol)와 같은 무선 자원예약 프로토콜이 제안되어지고 있다(4). 제안된 MRSVP 에서는 자원예약 지역의 불명확성과 지나친 신호부하를 초래하게 되었고, 이를 해결하기 위해서 본 논문에서는 계층적 MRSVP(H-MRSVP)를 이용한 새로운 호 제어기법과 무선 자원 예약 기법에 대해 연구하였다.