• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권10호
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• pp.2376-2394
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• 2013

In order to ensure both of the whole system capacity and users QoS requirements in heterogeneous wireless networks, admission control mechanism should be well designed. In this paper, Multi-agent Q-learning based Admission Control Mechanism (MQACM) is proposed to handle new and handoff call access problems appropriately. MQACM obtains the optimal decision policy by using an improved form of single-agent Q-learning method, Multi-agent Q-learning (MQ) method. MQ method is creatively introduced to solve the admission control problem in heterogeneous wireless networks in this paper. In addition, different priorities are allocated to multiple services aiming to make MQACM perform even well in congested network scenarios. It can be observed from both analysis and simulation results that our proposed method not only outperforms existing schemes with enhanced call blocking probability and handoff dropping probability performance, but also has better network universality and stability than other schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권6호
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• pp.2450-2469
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• 2018

In this paper, we develop a spatiotemporal model to analysis of cellular user in underlay D2D communication by using stochastic geometry and queuing theory. Firstly, by exploring stochastic geometry to model the user locations, we derive the probability that the SINR of cellular user in a predefined interval, which constrains the corresponding transmission rate of cellular user. Secondly, in contrast to the previous studies with full traffic models, we employ queueing theory to evaluate the performance parameters of dynamic traffic model and formulate the cellular user transmission mechanism as a M/G/1 queuing model. In the derivation, Embedded Markov chain is introduced to depict the stationary distribution of cellular user queue status. Thirdly, the expressions of performance metrics in terms of mean queue length, mean throughput, mean delay and mean dropping probability are obtained, respectively. Simulation results show the validity and rationality of the theoretical analysis under different channel conditions.

• Journal of Information Processing Systems
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• 제2권2호
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• pp.88-94
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• 2006

In wireless cellular networks, previous researches on admission control policies and resource allocation algorithm considered the QoS (Quality of Service) in terms of CDP (Call Dropping Probability) and CBP (Call Blocking Probability). However, since the QoS was considered only within a predetermined cell capacity, the results indicated a serious overload problem of systems not guaranteeing both CDP and CBP constraints, especially in the hotspot cell. That is why a close interrelationship between CDP, CBP and cell capacity exists. Thus, it is indispensable to consider optimal cell capacity guaranteeing multiple QoS (CDP and CBP) at the time of initial cell planning for networks deployment. In this paper, we will suggest a distributed determination scheme of optimal cell capacity guaranteeing both CDP and CBP from a long-term perspective for initial cell planning. The cell-provisioning scheme is performed by using both the two-dimensional continuous-time Markov chain and an iterative method called the Gauss-Seidel method. Finally, numerical and simulation results will demonstrate that our scheme successfully determines an optimal cell capacity guaranteeing both CDP and CBP constraints for initial cell planning.

• 전자공학회논문지S
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• 제34S권4호
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• pp.1-11
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• 1997

In this paper, modeling of the communication channel occupancy characteristics at the base station in the wide area radio trunking syste has been performed. Using the results, mathematical analysis for the switching capacity at the network switch has also been done. Specificatlly, we propose a G/M/m queueing model for the single service area modeling, and analyze changes in call blockingprobabilities accoridng to changes in the burstness characteristics of group paging calls. As a result, we have observe dthat the channel occupancy variations become larger as the burstness characteristics become more apparent, to make the call blocking probability higher. Next, based on the single service area analysis, we have anayzed mathematically the average switching capacity required to serve mobile subscribers for a wide area radio trunking sytem, where multiple switching port assignments are required when the people in the same group are distributed over several base stations. Accordingly, we have observed that the average and the variance of switching channel occupancy are closely related to the mobility characteristics of subscribers, and that we need a netowrk switch having bigger capacity as subscribers show wider distribution. Especially, with the call dropping probability within 0.2%, a switch having about 5 to 6 times bigger can be required, compared with the one when the mobility of subscribers is mostly restricte dto a single service area.

• 전자공학회논문지S
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• 제34S권2호
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• pp.11-20
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• 1997

It is a recent trend that mobile communications and PCS are intergrated into the broadband network. Broadband mutlimedia traffic will be transported over the integrated network. In this paper, we propose a connection re-routing method for fast inter-switch hadoffs and dynamic resurce reservation scheme, which is based on the proposed re-routing method, for the ATM-based personal communications network. To reduce the delay for re-routing method, for the ATM-based personal communications network. To reduce the delay for re-routing, the proposed re-routing method is to reserve VPI/VCIs for possible inter-swich handoff calls in advance. Our reservation scheme is to statistically reserve the fixed resources for possible inter-switch handoff calls, according to the QoS of the handoff calls. The simmulation reslts show that our proposed scheme satisfies the required QoS of handoff calls and keep the dropping probability of handoff calls lower than other schemes.

• Journal of information and communication convergence engineering
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• 제6권1호
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• pp.19-23
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• 2008

The AQM (Active Queue Management) starts dropping packets earlier to notify traffic sources about the incipient stage of congestion. The AQM improves fairness between response flow (like TCP) and non-response flow (like UDP), and it can provide high throughput and link efficiency. In this paper, we suggest the QVARED (Queue Variation Adaptive RED) algorithm to respond to bursty traffic more actively. It is possible to provide more smoothness of average queue length and the maximum packet drop probability compared to RED and ARED (Adaptive RED). Therefore, it is highly adaptable to new congestion condition. Our simulation results show that the drop rate of QVARED is decreased by 80% and 40% compare to those of RED and ARED, respectively. This results in shorter end-to-end delay by decreasing the number of retransmitted packets. Also, the QVARED reduces a bias effect over 18% than that of drop-tail method; therefore packets are transmitted stably in the bursty traffic condition.

• 한국통신학회논문지
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• 제25권3B호
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• pp.423-430
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• 2000

Future microcellular systems will require distributed network control. A packet-switched network is suitable for this requirement. The packet reservation multiple access(PRMA) is a Reservation-ALOHA like protocol for wireless terminals to transmit packet speech to a base station. It allows spatially distributed users in cellular systems to transmit packeted voice and data to a common base station using a shared channel. In the existing PRMA, the problem is that the voice packets may collide with the data packets due to simultaneous channel access. the problem may be a major performance degradation factor to a voice and data mixed system. We propose a new PRMA method that integrates voice and data traffic efficiently by resolving the collision problem between data and voice packets. The proposed PRMA method gives a performance improvement than the existing PRAMA method in terms of voice packet dropping probability and data delay characteristic. From analytic results, we can confirm that the proposed PRMA method show a performance improvement than the existing PRMA protocol.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2004년도 춘계학술발표대회
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• pp.1517-1520
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• 2004

핸드오프는 무선 셀룰러 환경에서 사용자의 이동성(Mobility)을 유지해줄 수 있는 가장 중요한 기술 중의 하나이다. 이러한 핸드오프 기술은 사용자가 이동할 주변 셀에 대한 대역폭 예약과 관련이 있다. 효과적인 대역폭 사용을 위하여 사용자의 이동성을 예측하는 기술은 핸드오프 호의 실패율(Dropping Probability)과 핸드오프 지연(Latency)을 줄이는 효과적인 방법이다. 최근에 제시된 ZMHB 알고리즘은 기존의 알고리즘과는 달리 셀 내부의 이동 경로를 저장한 히스토리를 이용하여 사용자가 이동할 셀을 예측하였다. 그러나, 모든 사용자에 대하여 80~85%정도의 예측 정확도만을 보인다. 본 논문에서는 ZMHB 알고리즘에서 사용하는 존(Zone)을 세분화하여 이동 패턴을 저장하고, 이를 예측에 이용하는 Detailed-ZMHB 예측 알고리즘을 제안하고 성능 평가 결과를 보인다.

• 한국정보과학회논문지:정보통신
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• 제30권4호
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• pp.461-473
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• 2003

멀티미디어 어플리케이션은 문자 위주의 어플리케이션과는 달리 데이타의 연속성 때문에 QoS(Quality of Service)에 매우 민감하다. 셀룰러 이동망에서 고속으로 이동중인 사용자의 멀티미디어 어플리케이션에 대해 QoS를 지속적으로 제공하기 위해서는 효율적인 호 수락 기법이 필요하다. 본 논문은 우선순위를 이용한 호 수락 제어를 통해 MH(Mobile Host)에게 지속적인 QoS를 제공하는 2SCA(2-Step Call Admission) 기법을 제시한다. 본 논문에서는 셀의 크기가 작고, 서로 중첩되어 있는 셀 구조를 가정하였으며, MH의 호를 신규호, 핸드오프호 및 QoS 상향조정호로 분류하여 각각 다른 처리 기법을 적용하였다. 2SCA 기법은 기본 호 수락제어와 응용 호 수락제어로 구성되어 있다. 전자는 셀의 가용 대역폭에 따라 호 수락을 결정하며, 후자는 기본 호 수락제어에서 블록킹된 호를 대상으로 각 호의 종류에 따라 DTT(Delay Tolerance Time), PQueue(Priority Queue), UpQueue(Upgrade Queue) 알고리즘을 적용하여 호 수락을 결정한다. 본 논문에서 제시된 2SCA 기법의 성능을 평가하기 위해, 신규호 블록킹률, 핸드오프호 드롭핑률, 대역폭 이용률을 측정하였다. 시뮬레이션 결과, 본 논문의 호 수락 기법이 CSP(Complete Sharing Policy), GCP(Guard Channel Policy) 그리고 AGCP(Adaptive Guard Channel Policy) 등과 같은 기존의 메커니즘보다 우수함을 알 수 있었다.

• 대한전자공학회논문지TC
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• 제39권1호
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• pp.20-33
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• 2002

패킷을 이용한 음성 서비스는 무선 망을 통한 음성 서비스 등으로 구현되고 있으며, 미래의 모든 음성 서비스는 패킷 기반형으로 진화할 것이다. 이러한 측면에서 ATM의 AAL2를 이용한 음성 패킷의 전달은 백본 망에서 음성 패킷의 전달 효율을 증가시키는 대표적인 방법이다. AAL2를 이용한 음성 서비스의 경우, 망의 자원이 허락되면 새로운 호의 연결을 수락한다. 하지만 새로운 호에 의해 발생되는 패킷으로 기존의 AAL2 연결의 전송 지연이 급격하게 증가할 가능성이 존재한다. 따라서 본 논문에서는 AAL2를 이용한 음성 서비스를 제공하는데 있어, AAL2 버퍼 관리 매카니즘으로 N개의 호에 대해 N개의 가상 버퍼를 통하여 각각의 호에 대한 전송지연변이를 계산하고, 전송 지연 변이에 따른 패킷 폐기 알고리즘을 제시한다. 이러한 패킷 폐기 알고리즘은 새로운 호의 수락으로 인해 발생하는 전송지연변이의 증가때문에 기존의 호의 QoS가 급격하게 악화되는 것을 방지한다. 그리고 종단 대 종단 지연에 영향을 미치는 AAL2 패킷 구성과 ATM 셀 구성의 요소를 분석하고, 음성 서비스를 ATM 셀로 만드는 과정을 K-정책을 갖는 M/D/1 큐잉시스템과 MIN(K, Tc) 정책을 갖는 M/D/1 큐잉 시스템으로 모델링함으로써, AAL2 패킷을 ATM 셀로 만드는 과정에서의 ATM 셀 밀집도와 AAL2 버퍼에서의 지연시간을 분석하였다. 제안하는 알고리즘을 모의 실험하여서 큐잉 시스템 모델링 결과와 비교하고 성능 결과를 분석하였다. 성능 분석 결과, AAL2 패킷 생성 시간과 ATM셀 생성 시간은 음성 소스의 갯수가 증가할 경우 전송 지연에 영향을 미치지 못하였으며, 제안하는 알고리즘은 음성 소스의 QoS를 저하하지 않은 수준에서 전송 지연을 낮게 유지할 수 있었다.