• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권10호
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• pp.2509-2528
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• 2012

Time division multiple access (TDMA) is a widely used media access control (MAC) technique that can provide collision-free and reliable communications, save energy and bound the delay of packets. In TDMA, energy saving is usually achieved by switching the nodes' radio off when such nodes are not engaged. However, the frequent switching of the radio's state not only wastes energy, but also increases end-to-end delay. To achieve high energy efficiency and low delay, as well as to further minimize the number of time slots, a multi-objective TDMA scheduling problem for industrial wireless mesh networks is presented. A hybrid algorithm that combines genetic algorithm (GA) and simulated annealing (SA) algorithm is then proposed to solve the TDMA scheduling problem effectively. A number of critical techniques are also adopted to reduce energy consumption and to shorten end-to-end delay further. Simulation results with different kinds of networks demonstrate that the proposed algorithm outperforms traditional scheduling algorithms in terms of addressing the problems of energy consumption and end-to-end delay, thus satisfying the demands of industrial wireless mesh networks.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1432-1435
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• 1996

This paper obtains maximum allowable delay bounds for stability of network-based control systems and presents a network scheduling method which makes the network-induced delay be less than the maximum allowable delay bound. The maximum allowable delay bounds are obtained using the Lyapunov theorem. Using the network scheduling method, the bandwidth of a network can be allocated to each node and the sampling period of each sensor and controller can be determined. The presented method can handle three kinds of data (periodic, real-time asynchronous, and non real-time asynchronous data) and guarantee real-time transmissions of real-time synchronous data and periodic data, and possible transmissions of non real-time asynchronous data. The proposed method is shown to be useful by examples in two types of network protocols such as the token control and the central control.

• 한국통신학회논문지
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• 제32권1A호
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• pp.13-23
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• 2007

본 논문에서는 OFDMA(Orthogonal Frequency Division Multiple Access) 시스템에서 실시간 트래픽 전송을 위한 효율적 패킷 스케줄링 기법을 제안한다. 본 방식은 패킷의 시간 지연 구속을 우선 만족시키면서 데이터 전송률도 향상시키는 기법으로 TEDC(Throughput Enhancement Under Delay-Constraint)라 불리운다. 사용자별 트래픽 특성에 따른 허용 지연 시간(Tolerable Delay Time TDT)을 정의하여 다양한 시간 지연 요구 조건을 차별화 하여 관리함으로써 무선 자원의 사용 효율을 향상시킨다. 논문에서 제안하는 TEDC 방식은 두 단계로 이루어진다. 첫 번째 단계에서는, 실시간 서비스를 위해 요구되는 시간 지연 구속을 만족하기 위해 잔여 허용 시간이 남지 않은 긴급한 사용자들에게 우선적으로 무선자원을 할당한다. 두 번째 단계에서는 첫 번째 단계에서 할당하고 남은 잉여 무선 자원에 대해서 자원의 활용도를 최대화하여 전체 데이터 전송률(Throughput)을 향상시킨다. 제안된 TEDC 방식의 성능은 기존의 자원할당 방식인 Round robin, M-LWDF, EXP 방식과 패킷 손실률, 데이터 전송률, 채널 활용도 측면에서 비교, 분석된다. 시뮬레이션 결과, TEDC 방식이 패킷 손실률, 데이터 전송률, 채널 활용도 측면에서 다른 자원 할당 방식보다 모두 우수한 성능을 보였다.

• 대한전자공학회논문지TC
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• 제40권6호
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• pp.225-236
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• 2003

본 논문에서는 인터넷 차별화 서비스 구조인 지연 비례 서비스를 무선 망 환경에서도 제공할 수 있는 WDPS(Wireless Delay Proportional Service) 스케줄링 알고리즘을 제안한다. WDPS는 무선 망의 버스트 하고 위치-종속적인 채널 에러 특성을 고려하여 현재까지 서비스 된 클래스간 지연 서비스 정도를 근거로 적응적으로 다음에 서비스할 클래스를 선택한다. 제안된 스케줄링 방법은 무선 망 에러로 생기는 클래스큐의 블록킹 문제를 해결하고, 클래스간 공정한 지연 서비스 품질을 제공하며 서비스 보상이 점진적으로 이루어져 하나의 클래스가 독점적으로 무선자원을 사용하지 못하도록 하였다. 모의 실험에서는 제안된 WDPS 스케줄링 방법을 사용하여 기존 인터넷 지연 차별화 서비스를 무선 망에서도 원하는 서비스 요구조건에 맞게 서비스 할 수 있음을 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2369-2373
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• 2001

Usually the static scheduling algorithms such as DMS (Deadline Monotonic Scheduling) or RMS(Rate Monotonic Scheduling) are used for CAN scheduling due to its ease with implementation. However, due to their inherently low utilization of network media, some dynamic scheduling approaches have been studied to enhance the utilization. In case of dynamic scheduling algorithms, two considerations are needed. The one is a priority inversion due to rough deadline encoding into stricted arbitration fields of CAN. The other is an arbitration delay due to the non-preemptive feature of CAN. In this paper, an extended algorithm is proposed from an existing EDS(Earliest Deadline Scheduling) approach of CAN scheduling algorithm haying a solution to the priority inversion. In the proposed algorithm, the available bandwidth of network media can be checked dynamically by all nodes. Through the algorithm, arbitration delay causing the miss of their deadline can be avoided in advance. Also non real-time messages can be processed with their bandwidth allocation. The proposed algorithm can achieve full network utilization and enhance aperiodic responsiveness, still guaranteeing the transmission of periodic messages.

• Journal of Information Processing Systems
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• 제19권4호
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• pp.450-464
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• 2023

To address the problems of large system overhead and low timeliness when dealing with task scheduling in mobile edge cloud computing, a task scheduling and resource management strategy for edge cloud computing based on an improved genetic algorithm was proposed. First, a user task scheduling system model based on edge cloud computing was constructed using the Shannon theorem, including calculation, communication, and network models. In addition, a multi-objective optimization model, including delay and energy consumption, was constructed to minimize the sum of two weights. Finally, the selection, crossover, and mutation operations of the genetic algorithm were improved using the best reservation selection algorithm and normal distribution crossover operator. Furthermore, an improved legacy algorithm was selected to deal with the multi-objective problem and acquire the optimal solution, that is, the best computing task scheduling scheme. The experimental analysis of the proposed strategy based on the MATLAB simulation platform shows that its energy loss does not exceed 50 J, and the time delay is 23.2 ms, which are better than those of other comparison strategies.

• Journal of Communications and Networks
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• 제16권1호
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• pp.36-44
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• 2014

Exploiting the energy-delay tradeoff for energy saving is critical for developing green wireless communication systems. In this paper, we investigate the delay-constrained energy-efficient packet transmission. We aim to minimize the energy consumption of multiple randomly arrived packets in an additive white Gaussian noise channel subject to individual packet delay constraints, by taking into account the practical on-off circuit power consumption at the transmitter. First, we consider the offline case, by assuming that the full packet arrival information is known a priori at the transmitter, and formulate the energy minimization problem as a non-convex optimization problem. By exploiting the specific problem structure, we propose an efficient scheduling algorithm to obtain the globally optimal solution. It is shown that the optimal solution consists of two types of scheduling intervals, namely "selected-off" and "always-on" intervals, which correspond to bits-per-joule energy efficiency maximization and "lazy scheduling" rate allocation, respectively. Next, we consider the practical online case where only causal packet arrival information is available. Inspired by the optimal offline solution, we propose a new online scheme. It is shown by simulations that the proposed online scheme has a comparable performance with the optimal offline one and outperforms the design without considering on-off circuit power as well as the other heuristically designed online schemes.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.75-78
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• 1998

In this paper, we propose a new cell discarding and scheduling scheme which reduce cell loss rate by measuring, in real time, the number of discarded cells in the queuing system with a different loss priority for each class of service such that each class of service meets its cell loss rate requirements and reduce average delay rate for the traffic that is sensitive in cell delay in output buffer of the ATM switch. Throughout the computer simulation, the existing scheduling scheme and proposed scheme are compared with respect to cell loss rate and average delay time.

• 한국컴퓨터정보학회논문지
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• 제6권1호
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• pp.67-73
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• 2001

본 논문에서는 광대역 가입자 엑세스망의 인프라 기술인 ATM 노드에서의 셀 스케줄링 알고리즘을 제안한다. 기존의 트레인 스케줄링 알고리즘(Train scheduling algorithm)이나 챠오 스케쥬링 알고리즘(Chao scheduling algorithm), 동적 스케줄링 알고리즘(Dynamic scheduling algorithm) 등의 ATM 스케줄링 알고리즘들은 셀 손실률이 높고 전송 채널의 낭비가 많은 단점이 있다. 본 연구에서는 다양한 멀티미디어 서비스 제공을 위해 입력 소스 트래픽의 QoS 등급에 기초를 둔 제어 방식을 제안한다. 먼저 다양한 서비스 품질을 만족시키기 위한 스케줄링 알고리즘과 기능적 구조를 설계하고. 모의실험을 통해 패킷 손실율과 평균지연 측면에서 알고리즘의 성능을 고찰한다.

• 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.