• 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.

• 대한전자공학회논문지TC
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• 제40권12호
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• pp.46-58
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• 2003

최근의 인터넷은 기존의 최선형 서비스구조(best-effort)에서 벗어나 별도의 차별화 된 트래픽 처리와 서비스품질(QoS)을 요구하는 응용들을 지원할 수 있는 네트워크 구조 및 트래픽 엔지니어링 기술을 요구하고있다. 더욱이 유선에서 무선으로 인터넷이 확장되면서 위치-종속적이며 버스트하게 발생되는 에러로 인해 기존의 패킷 스케줄링 방법으로는 정의된 서비스 품질을 제공할 수 없다. 따라서 본 논문에서 무선 인터넷 차별화 서비스 네트워크 환경에서도 정의된 서비스 품질을 제공할 수 있는 WDSPS(Wireless DiffServ Packet Scheduling) 스케줄링 알고리즘을 제안한다. 제안된 스케줄링 알고리즘은 무선망 에러로 생기는 클래스 큐의 블록킹 문제를 해결하고, 차별화 서비스 망에서 요구하는 각 클래스간 패킷 처리율, 패킷 지연, 패킷 손실률 등의 관점에서 차별화 서비스를 제공하며, 클래스 및 플로우간 효율적인 보상 방법으로 서비스 보상이 점진적으로 이루어져 하나의 클래스 및 플로우가 독점적으로 무선자원을 사용하지 못하도록 하였다. 모의 실험에서는 제안된 WDSPS 스케줄링 방법을 사용하여 다양한 무선 환경에서 서비스 클래스간 차별화 된 서비스를 제공하며 전체 서비스 처리율을 향상시킬 수 있음을 보였다.

• 전기학회논문지
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• 제56권12호
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• pp.2262-2264
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• 2007

In this paper, we propose a distributed opportunistic scheduling scheme for wireless LAN network. Proportional fair scheduling is one of the opportunistic scheduling schemes and used for centralized networks, whereas we design distributed proportional fair scheduling (DPFS). In the proposed DPFS scheme, each receiver estimates channel condition and calculates independently its own priority with probabilistic manner, which can reduce excessive probing overhead required to gather the channel conditions of all receivers. We evaluate the proposed DPFS using extensive simulation and simulation results show that DPFS obtains up to 23% higher throughput than conventional scheduling schemes and has a flexibility to control the fairness and throughput by controlling the system parameter.

• 경영과학
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• 제24권1호
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• pp.113-126
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• 2007

This paper deals with a mathematical approach for finding the time-fractions for the time-fraction based scheduling method in multimedia wireless networks. By introducing a constraint that regulates the performance fairness amongst users, we present a systematic method for harmonizing both the system and user performance. Numerical results show that the time-fraction based scheduling method reinforced with our scheme is very effective especially in multimedia environments.

• Journal of Information Processing Systems
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• 제5권3호
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• pp.135-144
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• 2009

Most of the tasks in wireless sensor networks (WSN) are requested to run in a real-time way. Neither EDF nor FIFO can ensure real-time scheduling in WSN. A real-time scheduling strategy (RTS) is proposed in this paper. All tasks are divided into two layers and endued diverse priorities. RTS utilizes a preemptive way to ensure hard real-time scheduling. The experimental results indicate that RTS has a good performance both in communication throughput and over-load.

• Journal of Information Technology Applications and Management
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• 제23권2호
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• pp.61-80
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• 2016

The wireless mesh network (WMN) is a next-generation technology for data networking that has the advantage in cost and the flexibility in its construction because of not requiring the infra-structure such as the ethernet. This paper focuses on the optimal link scheduling problem under the wireless mesh network to effectuate real-time streaming by using the constraint programming. In particular, Under the limitation of half-duplex transmission in wireless nodes, this paper proposes a solution method to minimize the makespan in scheduling packet transmission from wireless nodes to the gateway in a WMN with no packet transmission conflicts due to the half-duplex transmission. It discusses the conflicts in packet transmission and deduces the condition of feasible schedules, which defines the model for the constraint programming. Finally it comparatively shows and discusses the results using two constraint programming solvers, Gecode and the IBM ILOG CP solver.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권12호
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• pp.4856-4871
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• 2015

Backpressure based scheduling has been considered as a promising technique for improving the throughput of a wide range of communication networks. However, this scheduling technique has not been well studied for heterogeneous wireless networks. In this paper, we propose a virtual-queue based backpressure scheduling (VQB) algorithm for heterogeneous multi-hop wireless networks. The VQB algorithm introduces a simple virtual queue for each flow at a node for backpressure scheduling, whose length depends on the cache size of the node. When calculating flow weights and making scheduling decisions, the length of a virtual queue is used instead of the length of a real queue. We theoretically prove that VQB is throughput-optimal. Simulation results show that the VQB algorithm significantly outperforms a classical backpressure scheduling algorithm in heterogeneous multi-hop wireless networks in terms of the packet delivery ratio, packet delivery time, and average sum of the queue lengths of all nodes per timeslot.

• 한국컴퓨터정보학회논문지
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• 제23권9호
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• pp.43-50
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• 2018

In this paper, we propose a hexagon model-based efficient beacon frame scheduling approach for wireless sensor networks. The existing beacon frame scheduling approaches use a lot of slots and subslots for the beacon frame scheduling. Thus, the data from source nodes are not efficiently delivered to a sink node. Also in case a sink node needs to broadcast a beacon frame to the nodes in the network, delivering the beacon frame to the network nodes is not efficient as well. Thus, to solve the problem, we use a hexagon model to find the number of slots and subslots for the beacon frame scheduling. By using them for the beacon frame scheduling, the proposed approach performs better than other approaches in terms of the data transmission delay, the number of received data, the beacon transmission delay and the number of relaying the beacon frames.

• Journal of Communications and Networks
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• 제7권4호
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• pp.408-416
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• 2005

Quality of service (QoS) provision is an important and indispensable function for multi-service wireless networks. In this paper, we present a new scheduling/admission control frame­work, including an efficient rate-guaranteed opportunistic scheduling (ROS) scheme and a coordinated admission control (ROS­CAC) policy to support statistic QoS guarantee in multi-service wireless networks. Based on our proposed mathematical model, we derive the probability distribution function (PDF) of queue length under ROS and deduce the packet loss rate (PLR) for individual flows. The new admission control policy makes admission decision for a new incoming flow to ensure that the PLR requirements of all flows (including the new flow) are satisfied. The numerical results based on ns-2 simulations demonstrate the effectiveness of the new joint packet scheduling/admission control framework.

• 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.