• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.12
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• pp.539-546
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• 2002

In this paper, we consider a wireless multimedia environment to service both real-time video traffic and non-real-time WWW-application traffic In our suggested new packet scheduling algorithm, we consider both the accumulation counter and SIR to reduce delay in real-time traffic. In addition, our packet scheduling algorithm gives priority first to real-time video traffic service and then to non-real-time internet Packet service when real-time traffic service is absent. From the simulation results, we find that the AC (Accumulation Counter) scheme has much smaller delay than the conversional M-LWDF scheme for real-time video data users, which has a special quality sensitive to its own delay. We also consider the transmission structure of using both the frame period in the time-axis and the OVSF codes in the code-axis at the same time, which is similar to the structure of HSDPA system.

• Journal of the Korea Computer Industry Society
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• v.2 no.9
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• pp.1225-1232
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• 2001

In this paper, we investigate the scheduling algorithm of router system for Internet services on large scale ATM networks based on the quality-of-service(QoS) level of the input source traffics. We suggest an approprite scheduling algorithm in order to satisfy their QoS requirements. For this purpose, we first study the service requirements of the multiplexer in Internet. Second, we suggest functional architecture of the multiplexer for real time services and the scheduling algorithm to satisfy various QoS requirements. Finally, the performance measures of interest, namely steady-state average delay time and fairness of network resources, are discussed by simulation results.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.399-401
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• 1999

최근 컴퓨터 네트워크를 통한 화상회의, 화상전화 VOD 등과 같은 응용 프로그램들이 실시간 통신을 필요로 한다. 이러한 실시간 통신에 적합한 ATM은 유연한 통신 서비스와 높은 질의 서비스를 제공함으로서 차세대 통신 네트웍으로 기대가 되고 있다. ATM 네트웍 막에서 실시간 통신을 하기 위해서는 실시간 데이터들이 지연한계를 만족해야 한다. 만약 이러한 지연한계를 만족시키지 못할 경우에는 서비스의 질이 떨어지거나 아니면 데이터가 아예 필요가 없어지게 된다. 이미 실시간 통신을 하기 위해 Virtual Clock, Stop-and-Go, EDF 등에 많은 패킷 스위치 스케줄링 정책들이 개발 되어져 왔다. 그러나 이러한 스위치 스케줄링 정책들은 대부분 그 방법의 복잡성 때문에 실제로 ATM 상에서 적용시키기가 힘들다. 본 논문에서는 ATM 네트웍 망에서 화상 통신을 하기 위해 적합한 새로운 스위치 모델인 TCRM-DS를 제시한다. TCRM-DS는 기존의 TCRM 모델의 장점인 단순성과 효율성을 그대로 유지하면서 TCRM 모델의 단점인 비 실시간 데이터에 대한 비효율적 처리를 개선한 것이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.13-23
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• 2007

In this paper, a packet scheduling scheme that supports real-time traffic having multi-level delay constraints in OFDMA systems is proposed. The proposed scheme pursues to satisfy the delay constraint first, and then manage the residual radio resource in order to enhance the overall throughput. A parameters named tolerable delay time (TDT) is newly defined to deal with the differentiated behaviors of packet scheduling according to the delay constraint level. Assuming that the packets violating the delay constraint are discarded, the proposed scheme is evaluated in terms of the packet loss probability, throughput, channel utilization. It is then compared with existing schemes for real-time traffic support such as the Exponential Scheduling (EXP) scheme, the Modified Largest Weighted Delay First (M-LWDF) scheme, and the Round robin scheme. The numerical results show that the proposed scheduling scheme performs much better than the aforementioned scheduling schemes in terms of the packet loss probability, while slightly better in terms of throughput and channel utilization.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.505-507
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• 2004

IEEE 802.11 무선랜 표준에서 MAC(Media Access Control)은 동기와 비동기의 두 가지 타입의 서비스를 지원한다. 동기적 실시간 트래픽은 PCF(Point Coordination Function)에 의해서 폴링 엑세스 기법에 의해 처리된다. 비동기적 비실시간 트래픽은 CSMA/CA 프로토콜 기반의 DCF(Distributed Coordination function)에 의해 처리된다. 그래서 실시간 트래픽은 지연과 패킷손실에 민감하고 비실시간 트래픽은 에러와 처리율에 민감하기 때문에 적당한 트래픽 스케줄링 알고리즘이 설계되어질 필요가 있다. 하지만 IEEE 802.11 무선랜 표준은 실시간 트래픽을 효율적으로 서비스를 해주지 못하고 있다. 그래서 본 논문에서는 PCF 구간내에서 서비스를 받지 못한 실시간 트래픽 스테이션들을 DCF 구간에서 우선적으로 서비스함으로써 QoS를 향상시킬 수 있다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1465-1468
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• 2003

본 연구는 실시간 서비스 트래픽, 즉 보장형 서비스를 위한 스케줄링 알고리즘들에 대한 성능 분석에 대한 연구이다. 특히 실시간 데이터 전송의 경우, 작은 지연 시간을 요구하면서 안정된 QoS를 요구하고 있다. 기존에 알려진 FQ, WFQ, WF2Q, Virtual Clock 스케줄링 알고리즘들을 사용해서 대기류의 수학적 모델이 아닌 시뮬레이션 도구를 사용하여, 지연에 민감한 보장형 서비스 트래픽에 대한 시간 복잡도, 공정성, 처리율 측면으로 성능을 분석하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.6
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• pp.1065-1071
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• 2009

Satellite application services can be divided into realtime services like voice communications and non-real time services like traditional data communications. To support both types of services on the same On-Board Switching(OBS), a scheduler which depends on their service classes is required. A fixed priority scheduling policy has a starvation problem. In this paper we propose a scheduling scheme based on premium and age. Premium is a fixed value which is given to a certain class of services. Age is another parameter of the scheduling policy and it will be increased by one for every scheduling cycle. The scheme we propose chooses a packet which has the largest sum of its age and premium. Simulation results indicate that the proposed approach shows better performance in both average cell delay and std-dev of cell delay for the lower class of service. There is no staying in infinite starvation state.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3B
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• pp.171-182
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• 2003

In this paper, we propose an efficient and simple fair queueing algorithm, called Minimum Possible Virtual Start Time Fair Queueing (MPSFQ), which has O(1) complexity for the virtual time computation while it has good delay and fairness properties. The key idea of MPSFQ is that it has an easy system virtual time recalibration method while it follows a rate-proportional property. MPSFQ algorithm recalibrates system virtual time to the minimum possible virtual start time of all backlogged sessions. We will show our algorithm has good delay and fairness properties by analysis.

• Journal of the Korea Society of Computer and Information
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• v.29 no.1
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• pp.1-9
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• 2024

This paper proposes an integration of the ED-H scheduling algorithm, known for optimal real-time scheduling, with the LoRaEnergySim simulator. This integration facilitates the simulation of interactions between real-time scheduling algorithms for tasks with time constraints in Class-A LoRaWAN Class-A devices using a super-capacitor-based energy harvesting system. The time and energy characteristics of LoRaWAN status and state transitions are extracted in a log format, and the task model is structured to suit the time-slot-based ED-H scheduling algorithm. The algorithm is extended to perform tasks while satisfying time constraints based on CPU executions. To evaluate the proposed approach, the ED-H scheduling algorithm is executed on a set of tasks with varying time and energy characteristics and CPU occupancy rates ranging from 10% to 90%, under the same conditions as the LoRaEnergySim simulation results for packet transmission and reception. The experimental results confirmed the applicability of co-simulation by demonstrating that tasks are prioritized based on urgency without depleting the supercapacitor's energy to satisfy time constraints, depending on the scheduling algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7B
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• pp.653-663
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• 2002

UMTS/GPRS has its own QoS architecture, but additionally needs to support IP-QoS to provide Internet services. This paper describes an IP-QoS provisioning mechanism in the MPLS-based UMTS/GPRS network. We propose a QoS framework that includes the functional architecture of the MPLS-based GPRS networks and the efficient scheduling mechanism based on Diffserv model. The proposed scheduling mechanims is especially focused on the QoS support for real-time services. It also includes a new buffer management scheme that combines the priority queuing and weighted round robin method. The ns-2 simulator has been used to verify the validity of the proposed scheduling method.