Object-based storage is a storage architecture that manages data as objects, as opposed to other storage architectures like file systems which manage data as a file hierarchy and block storage which manages data as blocks within sectors and tracks. In general, each object typically includes the data itself, a variable amount of metadata, and a globally unique identifier. Object storage seeks to enable capabilities not addressed by other storage architectures such as data replication and data distribution at object-level granularity. A distributed data store is a computer network where information is stored on more than one node, often in a replicated fashion. Recently, there are many excellent researches target on energy aware, performance-aware, and trade-of on cloud storage. However, less on the scheduling on the cost-efficient designs. This paper, aims to evaluate the data storage performance with hybrid storage. We try to provide a cost-aware scheme for tier-based hybrid storage. Our scheme can provide a proper placement for data. Thus, users and venders can use lower cost to get the performance that they need.

Our aim in the research is to address the scheduling problem of a uniform multiprocessor platform with a periodic task set. The processors in the platform have the same instruction architecture. Besides, each processor has a limited range of discrete available speeds and the speed of each processor can be adjusted independently from each other. We propose an off-line task-to-processor assignment algorithm, the Largest Task First with Available Speed Considerations (LTFwAS) algorithm to consider discrete available speeds for the processors. The algorithm can derive a feasible task assignment with the minimal energy consumption and has the time complexity of O(MNX), where M, N, and X are the numbers of uniform processors, tasks, and available speeds, respectively. A series of experiments are conducted to evaluate the proposed algorithm. The experimental results demonstrate that the performance of the proposed LTFwAS algorithm is greatly similar to that of the optimal algorithm.

ABSTRACT In order to satisfy quality‐of‐service requirements for real‐time multimedia applications over wireless networks, IEEE 802.11e has been proposed to enhance wireless‐access functionalities. In IEEE 802.11e, collisions occur frequently as the system load becomes heavy, and then, the latency for successfully transmitting data is lengthened seriously because of contention, handshaking, and backoff overheads for collision avoidance. In this paper, we propose a fragment‐based retransmission (FBR) scheme with quality‐of‐service considerations for IEEE 802.11e‐based wireless local area networks. Our FBR can be used in all proposed fragmentation‐based schemes and greatly decrease redundant transmission overheads. By utilizing FBR, the retransmission delay will be significantly improved to conform strict time requirements for real‐time multimedia applications. We develop an analytical model and a simulation model to investigate the performance of FBR. The capability of the proposed scheme is evaluated by a series of simulations, for which we have encouraging results. Copyright © 2011 John Wiley & Sons, Ltd.

ZigBee, a unique communication standard designed for low-rate personal area networks, has extremely low complexity, cost, and power consumption for wireless connectivity in inexpensive, portable, and mobile devices. Among the well-known ZigBee topologies, the cluster tree is especially suitable for wireless sensor networks because of its support for power saving operations and light-weight routing. However, the restricted routing paths caused by the cluster tree would form transmission bottlenecks such that it is difficult to guarantee quality of service (QoS) for critical packet deliveries in mission-critical networks. To address the problem, we propose a QoS-oriented framework with an analytical model to provide stochastic QoS guarantees for urgent information deliveries in ZigBee cluster-tree networks. Through analysis and simulations, we demonstrate the efficacy of the proposed framework.

IEEE 802.11 wireless networks utilize a hard handoff scheme when a mobile station is travelling from one area of coverage to another within a transmission duration. When the station is running a real-time multimedia application receiving data from the wireless network, in each pair of neighboring MAPs, contention scheme is used to transmit data. The latency for successfully transmitting data is seriously lengthened so that the deadlines of data frames are missed with high probabilities. In this paper, we propose a fuzzy-based cross-layer transmission (FCLT) scheme with QoS considerations for IEEE 802.11 mesh wireless networks, which utilizes the grey model and the fuzzy theorem. In the handoff procedure, some ratio of real-time data frames will be relayed to the next MAP based on received signal strength indication of PHY layer and contention window of MAC layer, which can meet the minimal QoS requirements. By utilizing FCLT, the ratios of data frames missing deadlines will be significantly improved to meet timing requirements for real-time multimedia applications. We develop a simulation model to investigate the performance of FCLT. The capability of the proposed scheme is evaluated by a series of experiments, for which we have encouraging results.

Security has become one of the major issues for data communication over wired and wireless networks. Different from the past work on the designs of cryptography algorithms and system infrastructures, we aim at the proposing of a dynamic routing algorithm that could randomize delivery paths for data transmission. The algorithm is easy to implement and compatible with popular routing protocols, such as routing information protocol in wired networks and destination-sequenced distance vector protocol in wireless networks, without introducing extra control messages. An analytic study on the proposed algorithm is presented, and a series of simulation experiments are conducted to verify the analytic results and to show the capability of the proposed algorithm.

In order to satisfy QoS requirements for real-time multimedia applications over wireless networks, IEEE 802.11e has been proposed to enhance wireless-access functionalities. However, as system load is heavy, collisions occur most often and then the time needed for successfully transmitting data is lengthened seriously due to contention, handshaking, and long backoff processes for collision avoidance. It is important to keep QoS requirements satisfied. Therefore, we propose a fragment-based retransmission (FBR) scheme with QoS considerations for IEEE 802.11 wireless local area networks (WLAN). By utilizing IEEE 802.11e with FBR, the retransmission delay will be improved to conform strict time requirements for real-time multimedia applications. The capability of the proposed scheme is evaluated by a series of experiments, for which we have encouraging results.

Energy-efficient designs have played import roles for hardware and software implementations for a decade. With the advanced technology of VLSI circuit designs, energy-efficiency can be achieved by adopting the dynamic voltage scaling (DVS) technique. In this paper, we survey the studies for energy-efficient scheduling in real-time systems on DVS platforms to cover both theoretical and practical issues.

This research is motivated by the needs of dwell scheduling over multiple transmitters/receivers in many real radar systems. We propose a linear-programmingbased approach with efficient implementations to minimize the number of radar tasks being dropped from the system and to balance workloads over multiple transmitters/ receivers. A priority-based task dropping policy and an incremental version of the task assignment algorithm are proposed for task dropping and on-line implementations. The capability of the proposed algorithm is evaluated by a series of experiments, for which we have encouraging results.

In recent years, many modern phased-array radars are built with commercial off-the-shelf components, and the functions of many hardware components are also reimplemented by software modules. In such systems, radar tasks could be modeled as distributed real-time tasks which require end-to-end deadline guarantees and have precedence constraints. Different from most previous work on either algorithms with restrictions in resource utilization or heuristics without analytical ways for schedulability guarantees, the objective of this paper is to propose a joint real-time scheduling algorithm for both transmitter/receiver and signal processor workloads with an analytical framework for offline probabilistic analysis and online admission control. The strength of our approach is verified by analysis results and a series of experiments based on a real phased-array radar for air defense frigates

A multifunction phased array radar must search and track suspicious targets in its surveillance space in a real-time fashion. With inefficient scheduling implementations in many traditional systems, much radar resource is wasted with a very limited performance gain. This paper targets one of the most important issues in the design of modern phased array radars: real-time dwell scheduling. We formalize the typical workload of a modern phased array radar and propose a rate-based approach to schedule radar dwells in a real-time fashion. We show how to reserve radar resources to guarantee the minimum radar operation without sacrificing the stability of the system. The strength of our approach is verified by a series of simulation experiments based on a real phased array radar for air defense frigates [A. G. Huizing et al. (1996)]. A significant improvement in the performance of phased array radars was shown.

In recent years, many modern phased array radars are built with commercial-off-the-shelf components, and the functions of many hardware components are also re-implemented by software modules. In such systems, radar tasks could be modelled as distributed real-time tasks, which require end-to-end deadline guarantees and have precedence constraints. Different from most previous work on either algorithms with restrictions in resource utilization or heuristics without analytical ways for schedulability guarantees, the objective of This work is to propose a joint real-time scheduling algorithm for both transmitter/receiver and signal processor workloads with an analytical framework for off-line probabilistic analysis and online admission control. The strength of our approach is verified by analysis results and a series of experiments based on a real phased array radar for air defense frigates [A. G. Huizing et al. (1996)].

While there has been a significant amount of research in real-time concurrency control, little work has been done in logging and recovery for real-time databases. This paper proposes a two-version approach which considers both real-time concurrency control and recovery. We propose a network-server-based architecture and algorithms which can not only reduce the blocking time of higher-priority transactions and improve the response time of client-side read-only transactions, but also provide a diskless runtime logging mechanism and an efficient and predictable recovery procedure. The performance of the algorithms was verified by a series of simulation experiments by comparing the algorithms with the well-known Priority Ceiling Protocol (PCP), the Read/Write PCP, the New PCP, and the 2-version two-phase locking protocol, for which we have very encouraging results. The schedulability of higher-priority transactions and the response time of client-side read-only transactions were all greatly improved.

With the advance of hardware and software technology, modern phased array radars are now built with commercial-off-the-shelf (COTS) components, and it opens up a new era in real-time resource scheduling of digital signal processing. This paper targets the essential issues in building a component-oriented signal processor (SP), which is one of the two major modules in modern phased array radars. We propose a simple but effective task allocation policy and a real-time scheduling algorithm to address the design objectives of SPs. We are able to bound the number of processing units needed for a component-oriented SP in the design time, while everything was done empirically in the past. A series of experiments was done to demonstrate the strength of our methodology.

With the advance of hardware and software technology, modern phased array radars are now built with commercial off-the-shelf (COTS) components, and it opens up a new era in real-time resource scheduling of digital signal processing. This paper targets the essential issues in building a component-oriented signal processor (SP), which is one of the two major modules in modern phased array radars. We propose a simple but effective task allocation policy and a real-time scheduling algorithm to address the design objectives of SPs. We are able to bound the number of processing units needed for a component-oriented SP in the design time, while everything was done empirically in the past. A series of experiments were done to demonstrate the strength of our methodology.