In a peer-to-peer wireless network, efficient distributed scheduling algorithms generally require all active nodes to acquire the state information of their respective neighbors, e.g., their queue lengths. However, in...
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ISBN:
(纸本)9781479930012
In a peer-to-peer wireless network, efficient distributed scheduling algorithms generally require all active nodes to acquire the state information of their respective neighbors, e.g., their queue lengths. However, information exchange between nodes is challenging in the absence of a collision-free schedule, mainly due to the half duplex design of today's radios. This paper studies medium access control (MAC) with the help of a physical layer technique that allows all nodes to efficiently exchange state messages with one-hop neighbors at the same time. Low-complexity distributed scheduling algorithms using simultaneous message exchange are proposed for two interference models. One of the algorithms is shown to produce schedules realizable by the greedy maximal scheduling algorithm under the node-exclusive interference model. Simulations demonstrate that both algorithms outperform some popular distributed random access schemes.
First, this paper describes several scheduling algorithms of grid spatial database, that is the random scheduling algorithm,. queue length algorithm, visit cost algorithm and queue visit cost algorithm Second, we make...
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ISBN:
(纸本)9781424435197
First, this paper describes several scheduling algorithms of grid spatial database, that is the random scheduling algorithm,. queue length algorithm, visit cost algorithm and queue visit cost algorithm Second, we make some simulation experiments on the operating capacity, operating time as well as processing unit utilization to these algorithms respectively with task capacity of 500,1000,2000,5000;at last, the results show that queue visit cost algorithm is the best one among them to deal with tasks under the grid spatial database environment, which can improve the efficiency of system operation, and let the system achieve the best operation status.
The performance of ATM switches are mainly influenced by switching fabric and scheduling algorithms. Input buffered switches have the strong advantage of efficient crossbar usage. This paper presents an input-queued c...
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The performance of ATM switches are mainly influenced by switching fabric and scheduling algorithms. Input buffered switches have the strong advantage of efficient crossbar usage. This paper presents an input-queued crossbar switches fabric supporting high speed switching, analyzes the scheduling algorithms for unicast trafficts and multicast traffic based on virtualoutput queueing (VOQ).Focusing on their performance issues, some typical schedulers are compared.
This paper addresses the problem of static and dynamic variable voltage scheduling of multi-rate periodic task graphs (i.e., tasks with precedence relationships) and aperiodic tasks in heterogeneous distributed real-t...
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ISBN:
(纸本)0769514413
This paper addresses the problem of static and dynamic variable voltage scheduling of multi-rate periodic task graphs (i.e., tasks with precedence relationships) and aperiodic tasks in heterogeneous distributed real-time embedded systems. Such an embedded system may contain general-purpose processors, field-programmable gate arrays (FPGAs) and application-specific integrated circuits (ASICs). Variable voltage scheduling is performed only on general-purpose processors. The static scheduling algorithm constructs a variable voltage schedule via heuristics based on critical path analysis and task execution order refinement. The algorithm redistributes the slack in the initial schedule and refines task execution order in an efficient manner. The variable voltage schedule guarantees all the hard deadlines and precedence relationships of periodic tasks. The dynamic scheduling algorithm is also based on an initially valid static schedule. The objective of the on-line scheduling algorithm is to provide best-effort service to soft aperiodic tasks, as well as to reduce the system power consumption by deter-mining clock frequencies (and correspondingly supply voltages) for different tasks at run-time, while still guaranteeing the deadlines and precedence relationships of hard real-time periodic tasks.
With ever-increasing demands for bandwidth optical packet/burst switching is used to utilise more of the available capacity of optical networks. In current prototypes of optical switches time and wavelength multiplexi...
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ISBN:
(纸本)9781479932146;9781479932139
With ever-increasing demands for bandwidth optical packet/burst switching is used to utilise more of the available capacity of optical networks. In current prototypes of optical switches time and wavelength multiplexing are combined to resolve packet contentions by means of Fiber Delay Lines and wavelength converters in the switching elements. Although optical switches have lower energy consumption than their electronic counterparts, it remains substantial. Since wavelength converters contribute significantly to the switches overall energy consumption, they should be used sparingly, rather than continuously. Current scheduling algorithms however do not take the usage of wavelength converters (and the related energy consumption) into account. To this end, we developed and evaluated new cost-based scheduling algorithms, which take both gap and delay into account to schedule an incoming packet. The performance improvement of these algorithms over existing algorithms can be traded off for a significant reduction in up-time of the wavelength converters by introducing a conversion cost in the involved cost function. This is backed by Monte Carlo simulation results, in which the algorithms are applied both in a void-filling and non-void-filling setting. The algorithms are of the same implementation complexity as current algorithms, and thus of immediate value to switch designers.
The performance evaluation is one of the most important issues for packet scheduling algorithms. The algorithms will be varied with the performance criteria. Because the packet scheduling algorithm has multiple perfor...
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ISBN:
(纸本)0780370937
The performance evaluation is one of the most important issues for packet scheduling algorithms. The algorithms will be varied with the performance criteria. Because the packet scheduling algorithm has multiple performance objects, how to reach multiple objects simultaneously is one difficult problem. This paper provides a set of integrated performance evaluating criteria from network traffic control model, and the criteria integrates several objects, such as the network performance, user's QoS requirement and system fairness. Then it is discussed and analyzed in details. Moreover, the integrated performance evaluating criteria can be applied to performance evaluation and improvement in network traffic control strategy and algorithms.
In this paper we study, the problem of providing real-time service to hard and soft real-time messages in wavelength division multiplexing (WDM) optical networks. We propose and evaluate a set of scheduling algorithms...
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ISBN:
(纸本)0818690143
In this paper we study, the problem of providing real-time service to hard and soft real-time messages in wavelength division multiplexing (WDM) optical networks. We propose and evaluate a set of scheduling algorithms which schedule message transmissions in single-hop WDM passive star networks based on specific time constraints. We compare the performances of our algorithms with that of the typical WDM scheduling algorithm which does not consider the time constraint of the transmitted messages by discrete-event simulations and an analytical model. We find that the improvement on real-time performance can be attributed to our scheduling algorithms where the time constraint of messages has been taken into consideration. This study suggests that when scheduling real-time messages In WDM networks, one has to consider not only the problem of resources allocation in the network but also the problem of sequencing messages based on their rime constraints.
On-demand broadcast is an effective wireless data dissemination technique to enhance system scalability and capability to handle dynamic data access patterns. Previous studies on time-critical on-demand data broadcast...
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ISBN:
(纸本)9781424437511
On-demand broadcast is an effective wireless data dissemination technique to enhance system scalability and capability to handle dynamic data access patterns. Previous studies on time-critical on-demand data broadcast were under the assumption that each client requests only one data item at a time. With rapid growth of time-critical information dissemination services in emerging applications, there is an increasing need for systems to support efficient processing of real-time multi-item requests. Little work, however, has been done. In this work, we study the behavior of six representative single-item request based scheduling algorithms in time-critical multi-item request environments. The results show that the performance of all algorithms deteriorates when dealing with multi-item requests. We observe that data popularity, which is an effective factor to save bandwidth and improve performance in scheduling single-item requests, becomes a hindrance to performance in multi-item request environments. Most multi-item requests scheduled by these algorithms suffer from a starvation problem, which is the root of performance deterioration.
The deployment of femto-cells in fifth-generation (5G) systems is necessary thanks to their advantages in terms of the number of supported users, and the reduction of energy consumption, thus it's promising to ado...
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ISBN:
(纸本)9781538681732
The deployment of femto-cells in fifth-generation (5G) systems is necessary thanks to their advantages in terms of the number of supported users, and the reduction of energy consumption, thus it's promising to adopt this concept to meet the 5G networks' requirements. However, the allocation of resources and the management of traffic while maintaining the quality of service (QoS);constitutes a major challenge in terms of fairness and perceived throughput at the terminal level. In this paper, a number of scheduling algorithms planned to be used in 5G, namely the Proportional Fair (PF) algorithm, the Exponential Proportional Fair algorithm (EXP / PF) and the algorithm Maximum Largest Weighted Delay First (MLWDF) are studied and compared in terms of equity (Fairness Index), useful rate (Goodput) and spectral efficiency, at the level of femto-cells in the downward direction.
Wireless Sensor Network (WSN), a network of randomly distributed unreliable sensor nodes, is a new genesis of Real-Time Embedded Systems that has become a big research area. Since the basic component of WSN i.e. senso...
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ISBN:
(纸本)9781538684924
Wireless Sensor Network (WSN), a network of randomly distributed unreliable sensor nodes, is a new genesis of Real-Time Embedded Systems that has become a big research area. Since the basic component of WSN i.e. sensor nodes have reduced energy, energy has become an important issue for WSNs with ascending applications. scheduling, one of the resource constraints of WSN, is an important WSN parameter that reduces energy usage, delay, improves network lifetime and also the fair transmission of all data packets. Hence, it is important that we study all the scheduling schemes. This paper explores the different types scheduling algorithms of WSN. A Comparative Analysis of the scheduling algorithms has also been done.
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