• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.1031-1038
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• 2004

The call admission control algorithm of hybrid scheme is proposed to enhance the QoS(quality of service) of attempted multimedia calls. In the initial stage of 3rd generation multimedia services networks, the major limitations include the small sefyice coverage and the limited radio link capacity. Because the initial massive deployment of network elements such as base stations, base station controllers, and mobile switching centers is restricted to populated areas and the other areas should be covered with the fewer network elements, the radio channel resources are hmited and coverage network is supposed to be established. Therefore the QoS of multimedia services is expected to be severely degraded when tentative traffic hot spot occurs frequently. Thus, the blocking probability of attempted calls mcreases when relatively large number of users try to place multimedia calls in a hot spot area of the wireless networks. In this situation, the proposed hybrid scheme can mitigate the degradation of the QoS of multimedia services by using the available radio channels of the neighboring cells.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5B
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• pp.338-347
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• 2012

In this paper, we propose the cooperative transmission scheme (CTS) for system throughput maximization in OFDMA based enterprise femtocell networks. In our scheme, the user equipment (UE) can receive the desired signal from serving femtocell BS (fBS) as well as an adjacent fBS. Thus, UE achieves an improved signal to interference plus and noise ratio (SINR) by the synchronized two signals. The performances of this strategy consider not only the call-level quality of service (QoS) but also the packet-level QoS. We first measure the call blocking probability and utilization for the downlink resources for various offered load in femtocell. Based on that, the outage probability and effective throughput of the system are simulated. Simulation results show that the proposed scheme can reduce the outage probability for enterprise femtocell compared with conventional systems.

• Journal of Satellite, Information and Communications
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• v.1 no.1
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• pp.12-19
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• 2006

In this paper, we propose the bandwidth borrowing scheme which improves the performance of the cal admission control of the integrated GEO satellite networks. In general, target transmission rates of communications and streaming services are fixed, but data services do not have the target transmission rates. Therefore, we can control the transmission rates for data services flexibly according to the system loading situation. When the available bandwidth of the system is insufficient, the bandwidth borrowing scheme gives the bandwidth to request real time services by the transmission rates control of data services through packet scheduler. We make the queueing model for our system model and demonstrate the results through simulations. The simulation results show that there is a 8.7-35.2 dB gain at the total blocking probability according to the use of bandwidth borrowing scheme.

• The KIPS Transactions:PartC
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• v.9C no.2
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• pp.283-292
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• 2002

This paper develops a scheme of resource management for guaranteeing QoS of realtime traffic in wireless mobile internet environments Mobile terminal has significant impact on the QoS originating mobility provided to a real-time application. The currently proposed MRSVP is not clear the boundary of resource reservation tregion and also can give rise to signal overhead to maintain sessions. To solve above problem, we propose the new reservation protocol, mobile cluster based H-MRSVP to combine MRSVP with moving cluster concept. In this paper, we analytically design our model for guaranteeing the QoS of realtime traffic and compare the three schemes: guard channel allocation schemes, DCA and our model. The performance measures are the probabilities of new call blocking, handoff dropping, resource utilization and service completion versus the system offered Erlang load. Consequently, Simulation indicate our model is more flexible than DCA in a view pint of channel utilization and gains the advantage over guard channel scheme with respects to the mobility.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.346-348
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• 2002

차량 항법 시스템(Car Navigation System)은 요즘 많은 발전을 거듭하여 차량 이용시 사용자가 가고자하는 목적지까지의 길을 쉽게 안내하고 있다. 이런 기술의 발전은 단순한 정적인 길 안내(Static Route Guidance) 뿐만 아니라. 동적인 길 안내(Dynamic Route Guidance)를 함으로써 자동차 운전자가 쉽고 빠른 길을 안내 받을 수 있게 되었다. 그러나 이러한 교통정보는 매우 변화가 심하므로 최초로 경로를 전송 받은 후 그 경로상에 교통정보가 변화하였다면, 이미 전송 받은 경로는 실시간으로 적극적으로 대응할 수 없고 실제 막히는 길로 안내할 수 있다. 목적지까지의 거리가 먼 경우 이런 현상이 더욱 심하게 나타날 수 있다. 이런 경우 운전자는 실제로는 막히는 길로 안내 받을 수 밖에 없다. 이런 문제점을 해결하기 위해 교통정보를 수집하는 기존의 시스템에 Ad Hoc 네트워킹이 가능한 시스템을 탑재한 교통정보 수집 차량(Probe Car)을 이용한다. 정보 수집 차량이 극심한 정체를 발견하면 근처를 지나는 경로를 가진 차량에게 이를 전달하여 새로운 경로를 다운받을 수 있도록 한다. 이런 방법은 Ad Hoc Relaying System〔l〕을 이용하여 가능하며, 센터에 수집되고 가공되는 시간을 최대한 줄일 수 있으며, 센터의 통신 오버헤드를 최소화할 수 있다. 또한 기지국에 호가 집중되어 call blocking이 발생함 경우에 이를 해결할 수 있다.

• ETRI Journal
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• v.21 no.4
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• pp.23-28
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• 1999

In this paper, we analyze the performance benefits of broadband ATM networks when the call control and management flows are separated from user data flows. The virtual path tunneling concept for control and management flows are applied to the same physical ATM networks. The behaviors of channel throughput and transfer delay are analyzed. It results that the proposed virtual short-cut paths can maintain the network being stable with acceptable bandwidth. They are very useful to provide the stable control and management capabilities for Internet and mobile applications in the broadband ATM networks. In our numerical results, the effective throughputs of the proposed virtual shout-ut channel are about three times than those of end-to-end user data channels with hop distances of 10, and about two times than those with hop distance of 5 when the link blocking probability increases to 0.1. It concludes that the effective channel bandwidth are greatly reduced down while physical links are not stable and user traffic flows are occasionally overflowed.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.3
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• pp.1-7
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• 1989

A new algorithm for frequency channel assignment in high capacity cellular mobile communication systems is proposed. The algorithm is the advanced type of the fixed channel assignment scheme. It enables calls having all nominal channels busy to be served by adjacent cells have idle channels. Thus, it considerably reduces the blocking probability compared with the fixed channel assignment. Simulation has been performed for a 49-cell system having uniform traffic density hexagonal array as a representative system lay out. Results showed that new algorithm is better than the fixed channel assignment scheme in high capacity cellular mobile communication systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10A
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• pp.1529-1539
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• 2000

The contact procedure of access channel necessary to set up the originating call has a close relation with the performance and capacity of the base station system in CDMA cellular network. This paper investigates the structure and the operation of the backward channel of IS-95 CDMA standard and explains the related system parameters. We can derive the throughput of the CDMA access channel depending on the arrivals of the access probes per access channel slot, given the system parameters such as cell radius, the maximum number of retransmission, and the error rates of the access and paging channel. It shows that the performance in throughput is much better in the CDMA IS-95 access channel than in the slotted aloha channel. It also gives the reasonable number of the trafic channels in a cell with the given blocking probability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.559-567
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• 2015

This paper focuses on evaluating the performance of a cellular network using power control based frequency reuse partitioning (FRP) in downlink (DL). In our work, in order to have the realistic environment, the spectral efficiency of the system is evaluated through traffic analysis, which most of the previous works did not consider. To further decrease the cell edge user's outage, the concept of power ratio is introduced and applied to the DL FRP based cellular network. In considering network topology, we first divide the cell coverage area into two regions, the inner and outer regions. We then allocate different sub-bands in the inner and outer regions of each cell. In the analysis, for each zone ratio, the performance of FRP system is evaluated for the given number of power ratios. We consider performance metrics such as call blocking probability, channel utilization, outage probability and effective throughput. The simulation results show that there is a significant improvement in the outage experienced by outer UEs with power control scheme compared to that with no power control scheme and an increase in overall system throughput.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.1
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• pp.73-81
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• 2007

This paper analyzes the performance of the handover in an overlaid micro/macro cellular system suited for mobile communication environments. In proposed model, it is analyzed the performance of case that subscriber who move with high speed does handover to a macrocell instead of doing handover by microcell. For an easy analysis, a circle shaped cell model are assumed both in microcell and macrocell. The reservation channel scheme is adopted in microcell for a low-speed mobile while a scheme using queue is used in macrocell for a high-speed mobile. The analytic results show that the proposed scheme provides a lower handover failure relatively than in a non-overlaid cellular system with slightly increased new call blocking probability.