• Journal of applied mathematics & informatics
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• v.33 no.1_2
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• pp.211-217
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• 2015

A dynamic spectrum access scheme with channel partitioning for secondary handover calls in cognitive radio networks is proposed to reduce forced termination probability due to spectrum handover failure. A continuous-time Markov chain method for evaluating its performance such as blocking probability, forced termination probability, and throughput is presented. Numerical and simulation results are provided to demonstrate the effectiveness of the proposed scheme with channel partitioning.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.757-763
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• 2011

This paper presents a channel reservation scheme using Wiener prediction model in order to reduce the rate of forced termination of cognitive users in cognitive radio networks. The proposed method uses Wiener prediction model to predict the number of radio channel required by the reappearance of primary users, and then calculates and reserves the number of channels that cognitive users demand for their spectrum handoff. Through the simulation we investigate cognitive users' forced termination rate and blocking rate with and without channel reservation. In addition we show the bandwidth utilization efficiency for both cases. The results show that the proposed scheme can reduce the forced termination rate of cognitive users at the cost of slightly increasing in blocking rate. Also it is seen that there is little difference in bandwidth utilization efficiency for both cases.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.160-162
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• 2003

Termination cryostat for 22.9kV, 1.26kA-class HTS power cable has been designed. The cryostat consists of vacuum vessel, liquid nitrogen vessel, current lead and HTS power cable. The current lead and the HTS power cable are connected in liquid nitrogen vessel cooled by forced-circulation subcooled liquid nitrogen. The maximum total heat load of this cryostat is expected to be 150w. In this paper, the detailed design of the termination cryostat is mentioned.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1333-1343
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• 2016

Spectrum sharing in centrally controlled cognitive radio (CR) networks has been widely studied, however, research on channel access for distributively controlled individual cognitive users has not been fully characterized. This paper conducts an analysis of random channel access of cognitive users controlled in a distributed manner in a CR network. Based on the proposed estimation method, each cognitive user can estimate the current channel condition by using its own Markov-chain model and can compute its own blocking probability, collision probability, and forced termination probability. Using the proposed scheme, CR with distributed control (CR-DC), CR devices can make self-controlled decisions based on the status estimations to adaptively control its system parameters to communicate better.

• Journal of the Korea Society for Simulation
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• v.11 no.1
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• pp.45-58
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• 2002

In the wireless communication systems of the next generation, the hard handover may frequent]y occur between the existing 2G(2nd generation) and the 3(1(3rd generation). When it occurs between the 2G and the 3G, the call setup procedure will be added to MT(Mobile Terminal), the relay bases in 2G and 3G, and the switches. It causes total time to handle the hangover to increase. Therefore, the forced termination probability may be increased since relative time decreases. In this paper, we propose a method to decrease the forced termination. The method execute the handover procedure with speed and direction of the MT preestimated in the inner cell when MT enters the boundary cell.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.1
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• pp.145-150
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• 2010

In this paper, the performance of cognitive radio network is analyzed in terms of Erlang capacity. To improve the Erlang capacity with respect to primary user (PU) and secondary user (SU) traffic, we propose an efficient radio resource management scheme utilizing the buffer for new SUs and interrupted SUs. Markov model is developed, and analyzed to derive the performances of the proposed spectrum sharing scheme in both primary system and secondary system. To determine the Erlang capacity region, the blocking probability, the forced termination probability and the non-completion probability are calculated. Simulation results provide insight into the advantages of the buffer utilization. It is observed that the supportable traffic loads of PU and SU can be increased significantly according to the buffer length.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.1
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• pp.24-32
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• 2006

In this paper, we proposed the multimedia call admission control algorithm with the bandwidth reservation based on the prediction of wireless terminal's location to guarantee quality of service for multimedia applications in cellular networks. This algorithm aims at minimizing possible errors In predicting the moving direction of terminals using a mobility prediction scheme. This prediction reduces the size of bandwidth reserved redundantly. In order to evaluate the performance of the algorithm, the blocking rate of new calls and the forced termination rate of hand-off calls are measured and compared the results with those of existing schemes. The results of the experiment revealed that the algorithm presented in this paper achieved better performance with lower call blocking rates and forced-termination rates than those of other methods.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.29 no.4
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• pp.100-106
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• 2006

We analyze a voice/data integrated traffic model of the cellular mobile communication system with hybrid guard channels for voice and handoff calls. In a multi-service integrated wireless environment, quality of service guarantee is crucial for smooth transportation of real time information. Real time voice traffic requires a guaranteed upper bounded on both delay and packet error rate, whereas data traffic does not. Voice traffic has high transmission priority over data packets. Thus one of the important problems is the design of admission control schemes which can efficiently accommodate the differential quality of service requirements. In this paper, a hybrid guard channel scheme is considered in which arriving calls are assigned channels as long as the number of busy channels in the cell is below a predetermined first threshold. When the number of busy channels reaches the first threshold, new originating data calls are queued in the infinite data buffer. Then reaches second threshold, only handoff calls are assigned the remaining channels and new originating voice calls are blocked. We evaluate the system by a two-dimensional Markov chain approach and generating function method and obtain performance measures included blocking probability and forced termination probability.

• Toxicological Research
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• v.7 no.2
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• pp.165-171
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• 1991

Effects of forced physical exercise on the CCl4 hepatotoxicity were examined in adult female rats. Rats were treated with CCl4 (2 mmol/kg, ip) and introduced into a cylindrical cage rotating at 9 rpm for 20 min/hr for 6 hr. Eighteen hr following the termination of exercise serum sorbitol dehydrogenase (SDH), glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT) activities and glucose-6-phosphatase activity were determined as parameters for hepatotoxicity. Physical exercise inhibited the $CCI_{4-}$induced increases in SDH, GOT, GPT activity, and glucose-6-phosphatase activity were determined as parameters for hepatotoxicity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5A
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• pp.294-304
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• 2003

For an efficient software download in cellular CDMA systems, session admission control based on area (SACA) is presented. In the SACA scheme, the base station only allows mobile terminal to start session when the mobile locates near the base station of a cell. A mobile that is located near cell center can request software download session, but the mobile that is far away from the center can request session only after arriving near the cell center. Session duration time follows exponential and Pareto distribution. Performance is analyzed in terms of handoff rate, mean channel holding time, session blocking probability and handoff forced termination probability. As analysis results, handoff rate between cells in the proposed scheme is reduced to 30 ~ 250 % compared to conventional scheme, according to traffic characteristics such as terminal speed, session duration time and the size of the allowable zone area in a cell for the start of the session. And new session blocking probability slightly decreases to 5 ~ 20 %, but handoff session forced termination probability drastically decreases to 35 ~ 220 %.