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Scheduling Strategy (scheduling + strategy)

Distribution by Scientific Domains

Information Science and Computing	44%
Engineering	44%

Selected Abstracts

Inter-cell coordination in wireless data networks

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 3 2006
Thomas Bonald
Over the past few years, the design and performance of channel-aware scheduling strategies have attracted huge interest. In the present paper, we examine a somewhat different notion of scheduling, namely coordination of transmissions among base stations, which has received little attention so far. The inter-cell coordination comprises two key elements: (i) interference avoidance and (ii) load balancing. The interference avoidance involves coordinating the activity phases of interfering base stations so as to increase transmission rates. The load balancing aims at diverting traffic from heavily loaded cells to lightly loaded cells. Numerical experiments demonstrate that inter-cell scheduling may provide significant capacity gains. Copyright © 2006 AEIT [source]

Simple On-Line Scheduling Algorithms for All-Optical Broadcast-and-Select Networks

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 1 2000
Marco Ajmone Marsan
This paper considers all-optical broadcast networks providing a number of slotted WDM channels for packet communications. Each network user is equipped with one tunable transmitter and one fixed receiver, so that full connectivity can be achieved by tuning transmitters to the different wavelengths. Tuning times are not negligible with respect to the slot time. A centralized network controller allocates slots in a TDWDM frame according to (long-term) bandwidth requests issued by users. Simple on-line transparent scheduling strategies are proposed, which accommodate bandwidth requests when they are received (on-line approach), with the constraint of not affecting existing allocations when a new request is served (transparency). Strategies that attempt to allocate in contiguous slots all the transmissions of each source on one wavelength reduce overheads, are simple, and provide good performance. Even better performance can be achieved, at the cost of a modest complexity increase, when the transparency constraint is not strictly imposed, i.e., when a full re-allocation of existing connections is performed once in a while. [source]

Fuzzy scheduling strategy for generalized switched server systems and its robustness over system heterogeneity

INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 3 2009
Xingxuan Wang
Generalized switched server system, a discretely controlled continuous-time system, in which N tanks are used to represent N parallel entities, respectively, can be employed to address a class of load-balancing problems. A tank-pair model is a system that consists of two tanks and a single input single output controller, which regulates the inflows of the two tanks to acquire the two uniform levels under the specified inflow constraints. According to a quantized observation of the N tank levels, some discrete events are generated, and based on certain event feedback strategy, switching the location of the tank-pair can control all the N tanks in a time-sharing manner to acquire the N levels uniformity. Different from some existing scheduling strategies, this study proposes a fuzzy scheduling strategy (FSS) for such generalized switched server systems. Special measures are taken to reduce the N -inputs two-outputs fuzzy inference to a two-inputs one-output one, which greatly facilitates fuzzy scheduler design. Simulation results show that the proposed FSS strategy outperforms over the three existing scheduling strategies as a whole, and they also show that the proposed FSS strategy demonstrates high robustness over system heterogeneity. © 2009 Wiley Periodicals, Inc. [source]

Optimizing patient flow in a large hospital surgical centre by means of discrete-event computer simulation models

JOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 6 2008
Rodrigo B. Ferreira MSc
Abstract Objective, This study used the discrete-events computer simulation methodology to model a large hospital surgical centre (SC), in order to analyse the impact of increases in the number of post-anaesthetic beds (PABs), of changes in surgical room scheduling strategies and of increases in surgery numbers. Methods, The used inputs were: number of surgeries per day, type of surgical room scheduling, anaesthesia and surgery duration, surgical teams' specialty and number of PABs, and the main outputs were: number of surgeries per day, surgical rooms' use rate and blocking rate, surgical teams' use rate, patients' blocking rate, surgery delays (minutes) and the occurrence of postponed surgeries. Two basic strategies were implemented: in the first strategy, the number of PABs was increased under two assumptions: (a) following the scheduling plan actually used by the hospital (the ,rigid' scheduling , surgical rooms were previously assigned and assignments could not be changed) and (b) following a ,flexible' scheduling (surgical rooms, when available, could be freely used by any surgical team). In the second, the same analysis was performed, increasing the number of patients (up to the system ,feasible maximum') but fixing the number of PABs, in order to evaluate the impact of the number of patients over surgery delays. Conclusion, It was observed that the introduction of a flexible scheduling/increase in PABs would lead to a significant improvement in the SC productivity. [source]

Performance evaluation of an autonomic network-aware metascheduler for Grids

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2009
A. Caminero
Abstract Grid technologies have enabled the aggregation of geographically distributed resources in the context of a particular application. The network remains an important requirement for any Grid application, as entities involved in a Grid system (such as users, services, and data) need to communicate with each other over a network. The performance of the network must therefore be considered when carrying out tasks such as scheduling, migration or monitoring of jobs. Surprisingly, many existing quality of service efforts ignore the network and focus instead on processor workload and disk access time. Making use of the network in an efficient and fault-tolerant manner is challenging. In a previous contribution, we proposed an autonomic network-aware scheduling architecture that is capable of adapting its behavior to the current status of the environment. Now, we present a performance evaluation in which our proposal is compared with a conventional scheduling strategy. We present simulation results that show the benefits of our approach. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Gain scheduling control of functional electrical stimulation for assisted standing up and sitting down in paraplegia: a simulation study

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 5 2005
Fabio Previdi
Abstract This paper reports on a simulation study that concerns the design of a non-linear controller for the standing up and the sitting down of a paraplegic patient by means of functional electrical stimulation. The simulations refer to a specific experimental device developed at the Fondazione Don Gnocchi (Italy). This is a seesaw, with the patient on one side and a weight on the other side. The patient is seated so that its posture can be fully known in real-time by continuously monitoring the knee joint angle. By delivering a suitable electrical stimulation to the quadriceps muscles groups, the patient can be raised and made to sit via smooth movements. Hitherto, the only feedback control law, which has been implemented in this area, is based on a PID controller and usually provides poor tracking performances. Hence, in this work, a non-linear gain scheduling controller has been designed and tested in a series of simulation experiments. The controller is tuned following a gain scheduling strategy: a set of local linear quadratic controllers is designed using a set of linear tangent models. A global non-linear gain scheduled controller is then obtained via interpolation. The gain- scheduled controller is implemented following an advanced strategy that guarantees that the so-called linearization property holds. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Class-based weighted fair queueing: validation and comparison by trace-driven simulation

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 10 2005
Rachid El Abdouni Khayari
Abstract World-wide web as well as proxy servers rely for their scheduling on services provided by the underlying operating system. In practice, this means that some form of first-come-first-served (FCFS) scheduling is utilized. Although FCFS is a reasonable scheduling strategy for job sequences that do not show much variance, for the world-wide web it has been shown that the requested-object sizes do exhibit heavy tails. Under these circumstances, job scheduling on the basis of shortest-job first (SJF) or shortest remaining processing time (SRPT) has been shown to minimize the total average waiting time. However, these methods have the disadvantage of potential job starvation. In order to avoid the problems of both FCFS and SJF we present in this paper a new scheduling approach called class-based interleaving weighted fair queueing (CI-WFQ). This scheduling approach exploits the specific characteristics of the job stream being served, that is, the distribution of the sizes of the objects being requested, to set its parameters such that good mean response times are obtained and starvation does not occur. In that sense, the new scheduling strategy can be made adaptive to the characteristics of the job stream being served. In this paper we compare the new scheduling approach (using trace-driven simulations) to FCFS, SJF and the recently introduced ,-scheduling, and show that CI-WFQ combines very good performance (as far as mean and variance of response time and blocking probability are concerned) with a scheduling complexity almost as low as for FCFS (and hence, lower than for SJF and ,-scheduling). The use of trace-driven simulation is essential, since the special properties of the arrival process makes analytical solutions very difficult to achieve. Copyright © 2005 John Wiley & Sons, Ltd. [source]