• Journal of Communications and Networks
• /
• v.14 no.4
• /
• pp.461-466
• /
• 2012

Any future heterogeneous overlay network system must be able to support ubiquitous access across multiple wireless networks. To coordinate these diverse network environments, one challenging task is a call admission decision among different types of network. In this paper, we propose a new call admission control scheme to provide quality of service (QoS) while ensuring system efficiency. Based on the interplay between network structure and dynamics, we estimate the network's QoS level and adjust the service price adaptively with the aim of maximizing the network performance. A simulation shows that the proposed scheme can approximate an optimized solution while ensuring a well-balanced network performance in widely different network environments.

• Proceedings of the IEEK Conference
• /
• 1999.11a
• /
• pp.125-128
• /
• 1999

In this paper, we propose a QoS-sensitive admission threshold method for the transmission of the non-real tine data packet such that the quality of services for both voice and data traffics are maintained to a required level. By detecting the active voice traffic during the current time slot, the non-real-time data packets are transmitted up to an admission threshold level during the next time slot. We found out that the optimum admission threshold is four voice traffic resources lower from the maximum allowable threshold to maintain the outage probability within 1% when the connected voice users are 15.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.21 no.4
• /
• pp.104-114
• /
• 2007

In this paper, an Ad-hoc Routing Protocol that works in wireless Ad-hoc communication networks with multiple radios and multiple channels and that controls call admission based on bandwidth measurement is proposed. Unlike the conventional Ad-hoc node with a single radio using a single channel, an Ad-hoc node of the protocol proposed, the MCQosR(Multiple Channel Quality of Service Routing), has multiple radios and uses multiple channels, which allows full duplex transmission between wireless Ad-hoc nodes, and reduces intra interference on the route. Also, a fixed channel only for reception at each node enables the estimation of the available bandwidth, which is used to control the call admission for QoS provision. The performance of the MCQosR was verified by simulation.

• Management Science and Financial Engineering
• /
• v.14 no.1
• /
• pp.35-63
• /
• 2008

We discuss the problem of selecting profitable customer orders arriving at a company providing two classes of services. For an arriving customer order for the first class, the company 1) makes a decision whether to accept or reject it (admission control), or 2) decides a price of the order to offer to an arriving customer (pricing control). The customer order undergoing processing in the system may be cancelled owing to unavoidable circumstances with the customer. The second class of service is provided as a sideline, which prevents the server from being idle when all the customer orders for the first class are completed and delivered. This yields the sideline profit. We discuss both admission control and pricing control problems in an identical framework as well as examine the structure of the optimal policies maximizing the total expected present discounted net profit gained over an infinite planning horizon.

• 유체기계공업학회:학술대회논문집
• /
• 2005.12a
• /
• pp.324-330
• /
• 2005

For axial-type turbines which operate at partial admission, a performance prediction model is developed. In this study, losses generated within the turbine are classified to windage loss, expansion loss and mixing loss. The developed loss model is compared with experimental results. Particularly, if a turbine operates at a very low partial admission rate, a circular-type nozzle is more efficient than a rectangular-type nozzle. For this case, a performance prediction model is developed and an experiment is conducted with the circular-type nozzle. The predicted result is compared with the measured performance, and the developed model quite well agrees with the experimental results. So the developed model could be applied to predict the performance of axial-type turbines which operate at various partial admission rates or with different nozzle shape.

• The KSFM Journal of Fluid Machinery
• /
• v.9 no.4 s.37
• /
• pp.13-19
• /
• 2006

For axial-type turbines which operate at partial admission, a performance prediction model is developed. In this study, losses generated within the turbine are classified to windage loss, expansion loss and mixing loss. The developed loss model is compared with experimental results. Particularly, if a turbine operates at a very low partial admission rate, a circular-type nozzle is more efficient than a rectangular-type nozzle. For this case, a performance prediction model is developed and an experiment is conducted with the circular-type nozzle. The predicted result is compared with the measured performance, and the developed model quite well agrees with the experimental results. So the developed model could be applied to predict the performance of axial-type turbines which operate at various partial admission rates or with different nozzle shape.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.03a
• /
• pp.391-397
• /
• 2004

The performance characteristics of partial admission supersonic turbines are analyzed by using the commercial CFD program FLUENT6.0. The governing equations were discretized with Euler implicit method in time and 2nd-order upwind scheme of FVM in space. The k-$\varepsilon$ turbulence model was utilized to describe the turbulent flow field. In order to investigate the nozzle--rotor interactions and the effect of partial admission, the flows in supersonic turbine rotor cascades with a nozzle are computed. Extensive computations of partial admission supersonic turbines provide the shock structures and flow patterns in the nozzle and rotor. It is clearly shown that the nozzle flow is highly affected by the shocks or expansion waves propagated from the rotor leading edge. And the rotor flow is also affected by the shocks or wakes originated from the nozzle.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.22 no.3
• /
• pp.593-603
• /
• 1997

Connection admission decision in ATM networks requires decision made in real time using fast algorithm. It is difficult to construct a model of the multiplexed traffic and thus, approximation of the traffic load is necessary. In this paper, we propose a measurement-based dynamic CAC(Connection admission Control) in ATM(Asynchronous Transfer Mode) networks, which observes current traffic by the moving window and set the window size to the value which is computed from the measured cell loss amount. It is based on the measurements of the traffic load over an admission period that is load enough to reflect the current traffic behavior instead of analytic modeling. And, the dynamic reallocation of bandwidth for each class leads to effective bandwidth utilization. The performance of proposed method is analyzed through computer simulation. The performance of proposed method is analyzed by using SIMAN simulation package and FORTRAN language. As can be seen in the simulation result, cell loss performance and bandwidth utilization have been increased.

• Journal of the Institute of Convergence Signal Processing
• /
• v.1 no.2
• /
• pp.97-104
• /
• 2000

Effective call admission control is desirable to control an ATM traffics. It should provide high fairness and utilization for different kinds of services during call admission. Complete bandwidth sharing method is efficient for utilization of bandwidth but not efficient for fairness of call admission. Complete bandwidth partitioning method is efficient for fairness but not efficient for utilization. We propose a new CST(Complete Sharing with Threshold) algorithm using threshold on a total link to improve fairness and utilization.

• Journal of Preventive Medicine and Public Health
• /
• v.19 no.2 s.20
• /
• pp.314-321
• /
• 1986

Forced vital capacities (FVC's) and forced expiratory volumes in one second $(FEV_{1.0}'s)$ of 26 pneumoconiosis patients were checked at admission and were followed up for 10 months through hospitalization. FVC's and $FEV_{1.0}'s$ were slightly improved in 10 months after admission. The improvement of FVC's was statistically significant. In the group of large opacities in chest radiographs, FVC's and $FEV_{1.0}'s$ were lower than those values in small opacity group at admission but improved more progressively. Similar finding was noted in the group of emphysema; those values were lower at admission but improved more progressively than those of non-emphysema group.