The evolution of wireless devices along with the increase in user mobility have created new challenges such as network partitioning and intermittent connectivity. These new challenges have become apparent in many situ...
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The evolution of wireless devices along with the increase in user mobility have created new challenges such as network partitioning and intermittent connectivity. These new challenges have become apparent in many situations where the transmission of critical data is of high priority. Disaster rescue groups, for example, are equipped with numerous devices which constantly gather and transmit various forms of data. The challenge of establishing communication between groups of this type has led to an evolutionary form of networks which we consider in this paper, namely, delay tolerant mobile networks (DTMNs). Nodes in DTMNs usually form clusters that we define as regions. Nodes within each region have end-to-end paths between them. Both regions, as well as nodes within a region, can be either stationary or mobile. For such environments, we propose using a dedicated set of messengers that relay message bundles between these regions. Our goal is to understand how messenger scheduling can be used to improve network performance and connectedness. We develop several classes of messenger scheduling algorithms which can be used to achieve inter-regional communication in such environments. We use simulation to better understand the performance and tradeoffs between these algorithms
This paper considers the problem of scheduling multiple users in the downlink of a time-slotted cellular data network. For such a network, opportunistic scheduling algorithms exploit the time-varying radio channel and...
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This paper considers the problem of scheduling multiple users in the downlink of a time-slotted cellular data network. For such a network, opportunistic scheduling algorithms exploit the time-varying radio channel and improve the system performance. This paper introduces a new optimum scheduling algorithm that maximizes the sum of average user performance subject to certain minimum and maximum performance constraints. The proposed algorithm, which is named as throughput constrained opportunistic scheduling (TCOS), is an extension of the framework proposed by Liu et al. For memory less fading channels, TCOS performs identically to another optimum algorithm. For fading channels with memory, TCOS significantly improves system performance. The TCOS with the minimum and maximum performance constraints offers better service differentiation among different classes of users than opportunistic scheduling algorithm provides with only minimum performance constraints
By means of dynamic system-level simulations, this work evaluates whether the studied Packet scheduling (PS) algorithms are capable of guaranteeing the quality of service (QoS) of the voice over IP (VoIP) on a scenari...
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ISBN:
(纸本)9781424436446
By means of dynamic system-level simulations, this work evaluates whether the studied Packet scheduling (PS) algorithms are capable of guaranteeing the quality of service (QoS) of the voice over IP (VoIP) on a scenario where the VoIP and Web browsing services will compete for the same resources and there is a maximum allowed end-to-end delay for VoIP packets. Two sets of algorithms were considered: QoS-differentiated and non-QoS-differentiated algorithms. It was verified the system capacity gains when the VoIP delay budget is increased. Regarding the PS performance, those algorithms able to perform QoS differentiation presented better performance in terms of system capacity and QoS compared to those non-QoS-differentiated algorithms. Among the former category, those that take into consideration delay requirements of the VoIP service presented the best overall capacity for all traffic mixes and delay budgets.
To overcome the disadvantages of the existing task duplication-based algorithms, this paper discusses the scheduling objectives of distributed real-time tasks, presents a novel structure called scheduled cluster tree,...
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To overcome the disadvantages of the existing task duplication-based algorithms, this paper discusses the scheduling objectives of distributed real-time tasks, presents a novel structure called scheduled cluster tree, and proposes a general optimization method for various task duplication-based algorithms. According to the result of experiments, PSO_I and PSO_II are both general algorithms that improve the schedules generated by various task duplication-based algorithms. PSO_I aims to optimize the schedules in minimizing the number of required processors without affecting the optimal scheduling length acquired. PSO_II aims to increase the utilization of processors at the acceptable expense of the scheduling length (i.e., in the range of deadline) besides minimizing the number of required processors. The time complexities of both methods match approximately that of the typical task duplication-based algorithms, e.g., the task duplication based scheduling algorithm and the optimal scheduling algorithm based on task duplication
Low energy consumption is an important problem in real-time embedded systems and loop is the most energy consuming part in most cases. Due to the uncertainties in execution time of some tasks, this paper models each v...
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Low energy consumption is an important problem in real-time embedded systems and loop is the most energy consuming part in most cases. Due to the uncertainties in execution time of some tasks, this paper models each varied execution time as a probabilistic random variable. We use rotation scheduling and DVS (Dynamic Voltage Scaling) to minimize the expected total energy consumption while satisfying the timing constraint with a guaranteed confidence probability. Our approach can handle loops efficiently. In addition, it is suitable to both soft and hard real-time systems. And even for hard real-time, we have good results.
For a just-in-time production scheme in large manufacturing systems we describe a considerable methodological extension into an integrated automated manufacturing system that is supported by a distributed real-time co...
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For a just-in-time production scheme in large manufacturing systems we describe a considerable methodological extension into an integrated automated manufacturing system that is supported by a distributed real-time computer system. This allows for higher flexibility in demand fluctuation as well as for a larger variety of products. At the same time better adaptability of transportation planning and transportation cost reduction are achieved through their integration. For this integrated scheduling we will present new bidding algorithms. Eventually, in an extension of the presented scheduling algorithms, novel fault tolerant strategies are included for overcoming or neutralizing the effect of transient machine failures. These are handled by cooperating local schedulers and managed to guarantee a minimal damage of schedules and its propagation, in the presence of failures. Through their integration into the production and transportation scheduling the advantages of the just-in-time approach (no storage costs) are preserved in principle while a near-optimal way for the affected jobs is found to meet their deadlines. The results of our extensive simulation experiments for a real production scenario are also discussed.
scheduling theory generally assumes that real-time systems are mostly composed of activities with hard real-time requirements. Many systems are built today by composing different applications or components in the same...
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scheduling theory generally assumes that real-time systems are mostly composed of activities with hard real-time requirements. Many systems are built today by composing different applications or components in the same system, leading to a mixture of many different kinds of requirements with small parts of the system having hard real-time requirements and other larger parts with requirements for more flexible scheduling and for quality of service. Hard real-time scheduling techniques are extremely pessimistic for the latter part of the application, and consequently it is necessary to use techniques that let the system resources be fully utilized to achieve the highest possible quality. This paper presents a framework for a scheduling architecture that provides the ability to compose several applications or components into the system, and to flexibly schedule the available resources while guaranteeing hard real-time requirements. The framework (called FSF) is independent of the underlying implementation, and can run on different underlying scheduling strategies. It is based on establishing service contracts that represent the complex and flexible requirements of the applications, and which are managed by the underlying system to provide the required level of service.
In this work' we will investigate the performance of different strategies when trying to schedule mixed traffic (video streaming with tight bounds on the delay jitter, and unconstrained delay data with a given thr...
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In this work' we will investigate the performance of different strategies when trying to schedule mixed traffic (video streaming with tight bounds on the delay jitter, and unconstrained delay data with a given throughput target) over a multi-carrier code division multiple access (MC-CDMA) air interface. In particular, a channel- and application- aware scheduling strategy is proposed and compared to a traditional maximum throughput algorithm. In our approach, fluctuations in the channel conditions of different users can be exploited via statistical multiplexing, while application-specific constraints (eg, on the delay of the relevant service) are also considered in the scheduling decision. Furthermore, we apply buffer management at the radio link layer to drop (possibly) outdated packets that are of less importance to the achievable quality. We will show that with clever choice of the parameters of our advanced algorithm we can support a larger number of satisfied video users at the expense of an increased average transmission delay for data users.
In supply chain-oriented management, facility layout is a main factor for the enterprise's benefit. There were few papers solving the discrete formulation of facility layout for its weakness though it has been dee...
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In supply chain-oriented management, facility layout is a main factor for the enterprise's benefit. There were few papers solving the discrete formulation of facility layout for its weakness though it has been deeply deliberated. An improved genetic algorithms-based approach was presented for solving a supply chain-oriented and dynamic discrete facility layout problem. Determining proper locations for given departments on facility layout problem (FLP) was one task in facility layout planning. Its objective was to minimize material handling costs or total distance that walk back and forth. Detailed information has been acquired by the author using survey, sample analysis, case study, numerical analysis, application, genetic operation and systematic thinking. In summing up it may be stated that numerical analysis and case study of DongBei special steel group in China show the effectiveness and practicality of the proposed model, software and genetic algorithm dealing with such kind of problems
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