• Journal of Communications and Networks
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• 제11권5호
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• pp.464-472
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• 2009

In this paper, we propose a packet scheduling algorithm for cellular relay networks by considering relay selection, variation of channel quality, and packet delay. In the networks, mobile users are equipped with not only cellular but also user relaying radio interfaces, where base station exploits adaptive high speed downlink channel. Our proposed algorithm selects a user with good cellular channel condition as a relay station for other users with bad cellular channel condition but can get access to relay link with good quality. This can achieve flexible packet scheduling by adjusting transmission rates of cellular link. Packets are scheduled for transmission depending on scheduling indexes which are calculated based on user's achieved transmission rate, packet utility, and proportional fairness of their throughput. The performance results obtained by using computer simulation show that the proposed scheduling algorithm is able to achieve high network capacity, low packet loss, and good fairness in terms of received throughput of mobile users.

• ETRI Journal
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• 제26권5호
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• pp.391-396
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• 2004

In this paper, we propose a packet scheduling discipline called packet loss fair scheduling, in which the packet loss of each user from different real-time traffic is fairly distributed according to the quality of service requirements. We consider an orthogonal frequency division multiple access (OFDMA) system. The basic frame structure of the system is for the downlink in a cellular packet network, where the time axis is divided into a finite number of slots within a frame, and the frequency axis is segmented into subchannels that consist of multiple subcarriers. In addition, to compensate for fast and slow channel variation, we employ a link adaptation technique such as adaptive modulation and coding. From the simulation results, our proposed packet scheduling scheme can support QoS differentiations while guaranteeing short-term fairness as well as long-term fairness for various real-time traffic.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 ICEIC The International Conference on Electronics Informations and Communications
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• pp.39-41
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• 2004

In this paper, I propose a thread scheduling policy for faster packet processing on the network processors with multithreaded multiprocessor architecture. To implement the proposed policy, I derived several basic parameters related to the thread scheduling and included a new parameter representing the packet contents and the features of the multithreaded architecture. Through the empirical study using a network processor, I proved the proposed scheduling ploicy provides better throughput and load balancing compared to the generally used thread scheduling policy.

• 산업경영시스템학회지
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• 제30권1호
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• pp.59-65
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• 2007

HPI (High-speed Portable Internet) system which provides high speed internet services is going to be commercialized soon. Since HPI provides simultaneously four different service types such as UGS (Unsolicited Grant Service), rtPS (real time Polling Service), nrtPS(non-real time Polling Service), and BE (Best Effort) under different QoS (Quality of Service) requirements and limited wireless channel resources, efficient packet scheduling mechanisms are necessary to increase the utilization of channels as well as to satisfy the various QoS requirements. This study regards the traffic data to be served as time series and proposes a new packet scheduling algorithm based on the nonparametric statistical test. The performance of the newly proposed algorithm is evaluated through the simulation analysis using a simulator that can evaluate the performance of packet scheduling mechanisms under various values of system parameters and measures such as packet delay time, data transmission rate, number of loss packets, and channel utilization.

• ETRI Journal
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• 제27권6호
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• pp.777-787
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• 2005

In this paper, we propose an urgency- and efficiency-based wireless packet scheduling (UEPS) algorithm that is able to schedule real-time (RT) and non-real-time (NRT) traffics at the same time while supporting multiple users simultaneously at any given scheduling time instant. The UEPS algorithm is designed to support wireless downlink packet scheduling in an orthogonal frequency division multiple access (OFDMA) system, which is a strong candidate as a wireless access method for the next generation of wireless communications. The UEPS algorithm uses the time-utility function as a scheduling urgency factor and the relative status of the current channel to the average channel status as an efficiency indicator of radio resource usage. The design goal of the UEPS algorithm is to maximize throughput of NRT traffics while satisfying quality-of-service (QoS) requirements of RT traffics. The simulation study shows that the UEPS algorithm is able to give better throughput performance than existing wireless packet scheduling algorithms such as proportional fair (PF) and modified-largest weighted delay first (M-LWDF), while satisfying the QoS requirements of RT traffics such as average delay and packet loss rate under various traffic loads.

• 한국통신학회논문지
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• 제34권3A호
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• pp.244-257
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• 2009

본 연구에서는 우선 삼성 전자에서 제시한 MMR에서 기회적 패킷 스케줄링 방법을 분석 하고 시뮬레이션을 통해 효율성을 검증해 보았다. 아울러 제안된 방법 하에서 수율과 공평성 사이의 관계를 조사 하였다. 본 연구의 주된 목적은 MMR에서 사용자의 QoS 요구 조건을 고려한 기회적 패킷 스케줄링 방법을 제안 하는 것이다. 시뮬레이션을 사용하여 제안된 방법의 성능을 i) QoS 를 고려하지 않은 순수한 기회적 패킷 스케줄링 방법의 성능 그리고 ii) QoS 만을 고려하고 기회적 패킷 스케줄링은 활용하지 않는 패킷 스케줄링 방법의 성능과 비교 분석하였다.

• 한국통신학회논문지
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• 제34권11B호
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• pp.1151-1168
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• 2009

멀티미디어의 프레임들은 QoS에 각각 다른 정도의 영향을 미치기 때문에, 패킷 손실을 줄이는 것이 항상 QoS를 향상시키는 것은 아니다. 사용자가 느끼는 QoS를 극대화하기 위해 본 논문은 중요성 기반 패킷 스케줄링을 제안한다. 중요성 기반 패킷 스케줄링 기법은 패킷 스케줄링의 두 가지 근본적인 문제를 해결한다. 하나는 "무엇을 보내는 가"이고 다른 하나는 "언제 보내는 가" 이다. 이용 가능한 대역폭이 계속 변화할 때, 대역폭에 적응하기 위해 모든 패킷을 보낼 수 없을 경우에는 일부의 패킷을 선택해서 보낼 수밖에 없다. 이를 위해 패킷 Significance를 제안하는데, 패킷 Significance는 효과적으로 프레임 상관관계를 파악하고 프레임의 중요도를 정량화한다. 그리디(greedy) 접근 기법이 패킷 선택 문제에 사용되었고, 패킷 Significance가 전송 스케줄링에 고려되었다. 널리 공개된 MPEG-4 비디오 클립이 실험에 사용되었으며, 시뮬레이션 소프트웨어에 디코딩 엔진이 삽입되었고, 성능 평가를 위해 PSNR을 측정하였다. 크기 기반 패킷 스케줄링 기법 및 비트 레이트 기반 최선(bit-rate based best-effort) 스케줄링 기법과 성능을 비교 분석하였다. 제안하는 기법이 더 중요한 패킷에 차별화 된 보호기능을 성공적으로 부여하며, QoS를 크게 향상시키는 것을 확인할 수 있었다.

• Journal of Communications and Networks
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• 제8권3호
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• pp.297-305
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• 2006

High-rate wireless personal area network (HR-WPAN) has been standardized by the IEEE 802.15.3 task group (TG). To support multimedia services, the IEEE 802.15.3 TG adopts a time-slotted medium access control (MAC) protocol controlled by a central device. In the time division multiple access (TDMA)-based wireless packet networks, the packet scheduling algorithm plays a key role in quality of service (QoS) provisioning for multimedia services. In this paper, we propose an adaptive cross-layer packet scheduling method for the TDMA-based HR-WPAN. Physical channel conditions, MAC protocol, link layer status, random traffic arrival, and QoS requirement are taken into consideration by the proposed packet scheduling method. Performance evaluations are carried out through extensive simulations and significant performance enhancements are observed. Furthermore, the performance of the proposed scheme remains stable regardless of the variable system parameters such as the number of devices (DEVs) and delay bound.

• 전기학회논문지
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• 제57권11호
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• pp.2124-2126
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• 2008

In the wireless communication systems, the demand of multimedia services is also increased. Unlike typical data packets, realtime service such as VoIP packets have delay bound and low loss rate requirement. In this paper we propose a new scheduling algorithm that be able to allocate resources to the different kinds of services such as VoIP and data packet. The proposed algorithm considers both time delay and channel condition toe determine the priority. Simulation results show that the proposed algorithm works more efficiently than the conventional algorithms.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1721-1723
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• 2002

In 3rd-generation mobile communication systems providing packet service, optimal scheduling algorithms we needed to increase service efficiency. In this paper, three scheduling algorithms (SP, EDF, and RPQ) which have been studied in the field of computer networks are applied with transmit power constraint to an interference-limited CDMA system, proving to be efficient.