• Journal of KIISE:Information Networking
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• v.29 no.1
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• pp.1-14
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• 2002

The most important issue in providing multimedia traffic on a mobile computing environments is to guarantee the mobile host(client) with consistent QoS(Quality of Service). However, the QoS negotiated between the client and network in one cell may not be honored due to client mobility, causing hand-offs between cells. In this paper, a call admission control mechanism is proposed to provide consistent QoS guarantees for multimedia traffics in a mobile computing environment. Each cell can reserve fractional bandwidths for hand-off calls to its adjacent cells. It is important to determine the right amount of reserved bandwidth for hand-off calls because the blocking probability of new calls may increase if the amount of reserved bandwidth is more than necessary. An adaptive bandwidth reservation based on an MPP(Mobility Pattern Profile) and a 2-tier cell structure has been proposed to determine the amount of bandwidth to be reserved in the cell and to control dynamically its amount based on its network condition. We also propose a call admission control based on this bandwidth reservation and "next-cell prediction" scheme using an MPP. In order to evaluate the performance of our call admission control mechanism, we measure the metrics such as the blocking probability of our call admission control mechanism, we measure the metrics such as the blocking probability of new calls, dropping probability of hand-off calls, and bandwidth utilization. The simulation results show that the performance of our mechanism is superior to that of the existing mechanisms such as NR-CAT1, FR-CAT1, and AR-CAT1.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.36-45
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• 1998

This paper discusses multiple access control aspects for a wireless extension of high-speed asynchronous transfer mode(ATM) networks. One challenging requirement is that mobile systems convey of diverse types of information including voice, computer data, facsimile, and video data that have different quality of service constraints. Basically, a centralized control scheme for a coordinated multiple access is required in order to efficiently accommodate multimedia traffic on wireless links. The proposed scheme dynamically scheduling the mobile terminal, which has data to transfer according to the service, types at base station. In this scheme, the scheduling algorithm is performed on the basis of traffic descriptors and QoS parameters, which required in the connection set up phase. As a consequence, the transmission scheduling is very flexible and can account for the different traffic rate and delay constraints that emerge from voice and data integration. The simulation result shows that the proposed scheme has better performance over other scheduling algorithms.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.1
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• pp.1-12
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• 2004

In this paper, we take advantage of the characteristics of optical burst switching (OBS) to support service-differentiation in optical networks. With the offset time between control packet and burst data, the proposed scheme uses different offset time of each service class. As contrasted with the Previous method, in which the high Priority service use only long offset time, it derives the burst loss rate as a QoS parameter in consideration of conservation law and given service-differential ratios and decides a reasonable offset time for this QoS finally Firstly proposed method classifies services into one of high or low class and is an algorithm deciding the offset time for supporting the required QoS of high class. In order to consider the multi-classes environment, we expand the analysis method of first algorithm and propose the second algorithm. It divides services into one of high or low group according to their burst loss rate and decides the offset time for high group, and lastly cumulates the offset time of each class. The proposed algorithms are evaluated through simulation. The result of simulation is compared with that of analysis to verify the proposed scheme.

• Electronics and Telecommunications Trends
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• v.29 no.3
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• pp.107-117
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• 2014

최근 스마트폰의 보급에 따라 모바일 관련 서비스의 급격한 시장성장으로 인한 무선랜 사용이 급속하게 증가하고 있다. 이로 인한 사용자의 증가는 사용기기의 고밀도화를 야기하였고, 이에 따른 전송신호에 대한 심각한 간섭증가 및 서비스 품질 저하를 초래했다. 본고에서는 현재 무선랜 네트워크의 성능저하의 주요 문제점인, 간섭증가에 대한 해결책으로 고려되고 있는 간섭회피기술과 간섭정렬기술에 대해 살펴본다. 또한 이동통신시스템의 트래픽 분산망으로, 무선랜 네트워크가 제공할 수 있는 성능측면에서 중요하게 고려되고 있는 QoS(Quality of Service) 관리기술에 대해 무선랜 표준그룹의 최근 기술에 대해 살펴보고자 한다. 이들 세 분야에 대한 종합적인 기술개발이 진행될 때 차세대 무선랜 네트워크의 요구되는 성능이 확보될 것이다.

• The KIPS Transactions:PartC
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• v.8C no.4
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• pp.443-450
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• 2001

본 논문에서는 무선 ATM 망에서 VBR(Variable Bit Rate) 트래픽의 QoS(Quality of Service)를 보장하고 무선 채널의 효율성을 극대화 할 수 있는 새로운 동적 슬롯 할당 알고리즘인 NDSA(Neural Dynamic Slot Assignment)를 제안한다. 제안된 알고리즘에서는 ATM 셀 헤더 부분의 GFC(Generic Flow Control) 필드 상에 단말기의 버퍼 상태와 셀 발생률 변화를 부호화 하여 piggybacking 하는 in-band 방식을 채택하였으며 다음 프레임에 할당할 슬롯의 갯수를 기존 방식과는 달리 신경회로망을 이용하여 유동적으로 조절하여 할당함으로써 단말기의 셀 손실이나 지연에 대한 QoS를 보장하고 채널 이용 효율을 높일 수 있었다. 제안된 알고리즘은 BONeS tool을 이용한 시뮬레이션을 통하여 기존의 방식과 비교 분석한 결과 그 정당성을 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12B
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• pp.1017-1027
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• 2006

Recently, Internet service providers are offering triple play service which combines voice and video services with the existing high speed Internet service under the common network infrastructure of IP protocol, so that they can create more benefit from operating a single network architecture. In line with this movement in the convergence of network and services, in this work we propose a bandwidth dimensioning method for the subscriber network of the IP network at flow level. To that purpose, let us propose a series of bandwidth dimensioning methods: bandwidth for best effort service only, bandwidth dimensioning for premium services, and bandwidth dimensioning schemes for the premium Internet services as well as the best effort service which comprise the TPS. Our link dimensioning method is based on the flow level that incorporates the flow blocking probability as a measure of grade of services(GoS), and investigates the characteristics of the proposed methods via extensive numerical experiments. After that, let us carry out a simulation experiment concerning the delay and loss performance of the packet scheduling for the premium services (QoS) using the bandwidth designed by our proposed method, via which the packet level quality of service (QoS) for the proposed link dimensioning method can be observed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9A
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• pp.1282-1289
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• 2000

In this paper we propose a Fractional Channel Reservation (FCS) scheme to satisfy a desired handoof dropping probability and to reduce the blocking probability of new calls using mobility characteristics and incoming handoff rate in mobile communication networks. When the ratio of the handoff call arrival rate is less then the ratio of the new call arrival rete, the proposed scheme is capable of determining the number of the guard channels which can guarantee the Quality of Service(QoS) in terms of the request handoff dropping probability and allocating dynamically the wireless channels the new calls according to the rest of the guard channels to reduce the new call blocking probability. Also we perform mathematical analysis and simulation to evaluate the performance of proposed scheme and compare to conventional guard channel scheme in terms of dropping probability blocking probability and the utilization efficiency of wireless channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6B
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• pp.508-516
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• 2006

The explosive growth of wireless network users and the existence of various wireless services have demanded high rate throughput as well as user's QoS guarantees. Towards this, this paper proposes QoS-oriented subcarrier allocation scheme considering the QoS provisioning of multiple users, which is major requirement for wireless network design point of view. This paper introduces joint RR/K&H combined with M-LWDF(Modified Largest Weighted Delay First) scheme throughout observing statistical channel behavior and real time queuing analysis for appropriate resource allocation tightly connected to multiuser scheduling. Accordingly, the system throughput can be enhanced, and the QoS demanded for delay sensitive services can be satisfied. Furthermore, the proposed scheme is applied for OFDMA(Orthogonal Frequency Division Multiple Access) systems to allocate sub-carriers in optimal way. The simulation results verify plausible performances of proposed resource allocation scheme via showing superior effective capacity under time-varying physical-layer channel behaviors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4B
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• pp.329-337
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• 2009

In wireless networks, maximizing throughput and minimizing energy consumption are two conflicting objectives. For elastic traffic, it is important to enhance the throughput since it directly affects the quality-of-service(QoS) of users. At the same time, the energy consumption should be minimized in order to prolong the battery lifetime of the mobile station. In this paper, we propose an energy efficient sleep scheme that considers throughput and energy saving simultaneously. The proposed scheme is designed for an efficient tradeoff between throughput and energy saving when receiving elastic traffic. Through extensive simulations, we compare the proposed scheme with the conventional scheme. Our proposed scheme outperforms the conventional one in terms of utility, i.e., user satisfaction, which is defined as inversely proportional to the weighted multiplication of service completion time and energy consumption.

• Proceedings of the Korea Contents Association Conference
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• 2006.05a
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• pp.132-135
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• 2006

Recently, multimedia data service using mobile terminal has been increased according to the development of wireless network technology which can be used in an indoor or outdoor environment. However, the wireless network shares the channel and it has a high error rate because of characteristics of transmission media. Therefore, it has a lot of problems for guaranteeing QoS(Quality of Services) in various requirements. This paper suggests a CSD-WRR(Channel State Dependent-WRR) method for compensating the service rate considering the transmission deadline. Simulation results show that the suggested method outperforms the conventional WRR in the view of the deadline miss rate and fairness.