Service-oriented smart home applications: composition, code generation, deployment, and execution

A smart home usually has a variety of devices or home appliance, instead of designing software for a specific home, this paper proposes a service-oriented framework with a set of ontology systems to support service and device publishing, discovery of devices and their services, composition of control software using existing control services that wrap devices, deployment, and execution of the composed service in an computing environment, monitoring the execution, and recovery from device failure. The ontology systems specify semantic information about devices, services, and workflows used in various smart home, and users can compose and recompose services for their specific needs. New devices, workflows, and services can be added into ontology. Most of the steps in this process can be automated including code generation. For example, service composition will be carried out in three steps: abstract workflow design, function construction, and device discovery, and different codes can be generated for different computing platforms such as Java and Open Services Gateway initiative environments. In this way, a variety of smart home can be constructed rapidly using the framework by discovery and composition using existing services and workflows. This paper illustrates this framework using a media control example to illustrate the ontology, discovery, composition, deployment, execution, monitoring, and recovery.     

Voltage-Clock Scaling for Low Energy Consumption in Fixed-Priority Real-Time Systems

Power and energy constraints are becoming increasingly prevalent in real-time embedded systems. Voltage-scaling is a promising technique to reduce energy and power consumption: clock speed tends to decrease linearly with supply voltage while power consumption goes down quadratically. We therefore have a tradeoff between the energy consumption of a task and the speed with which it can be completed. The timing constraints associated with real-time tasks can be used to resolve this tradeoff. In this paper, we present two algorithms for voltage-scaling. Assuming that a processor can operate in one of two modes: high voltage and low voltage, we show how to schedule the voltage settings so that deadlines are met while reducing the total energy consumed. We show that significant reductions can be made in energy consumption.     

Routing algorithm of minimizing maximum link congestion on grid networks

Wireless Networks - As regular topology networks, grid networks are widely adopted in network deployment. Link congestion and routing path length are two critical factors that affect the delay and...     

Evaluation of Error Recovery Blocks Used for Cooperating Processes

Three alternatives for implementing recovery blocks (RB's) are conceivable for backward error recovery in concurrent processing. These are the asynchronous, synchronous, and the pseudorecovery point implementations. Asynchronous RB's are based on the concept of maximum autonomy in each of concurrent processes. Consequently, establishment of RB's in a process is made independently of others and unbounded rollback propagations become a serious problem. In order to completely avoid unbounded rollback propagations, it is necessary to synchronize the establishment of recovery blocks in all cooperating processes. Process autonomy is sacrificed and processes are forced to wait for commitments from others to establish a recovery line, leading to inefficiency in time utilization. As a compromise between asynchronous and synchronous RB's we propose to insert pseudorecovery points (PRP's) so that unbounded rollback propagations may be avoided while maintaining process autonomy. We developed probabilistic models for analyzing these three methods under standard assumptions in computer performance analysis, i.e., exponential distributions for related random variables. With these models we have estimated 1) the interval between two successive recovery lines for asynchronous RB's, 2) mean loss in computation power for the synchronized method, and 3) additional overhead and rollback distance in case PRP's are used.     

Schedulable garbage collection in CLI virtual execution system

Virtual software execution environment, known as Virtual Machine (VM), has been gaining popularity through Java Virtual Machine (JVM) and Common Language Infrastructure (CLI). Given their advantages in portability, productivity, and safety, etc., applying VM to real-time embedded systems can leverage production cost, fast time-to-market, and software integrity. However, this approach can only become practical once the VM operations and application tasks are made schedulable jointly. In this paper, we present a schedulable garbage collection algorithm applicable on real-time applications in CLI virtual machine environment. To facilitate the scheduling of real-time applications and garbage collection operations, we make the pause time due to garbage collection controllable, and the invocation of garbage collection predictable. To demonstrate the approach, a prototype for a schedulable garbage collection has been implemented in CLI execution environment. The garbage collection is carried out by a concurrent thread while meeting a targeted pause time and satisfying the memory requests of applications. A cost model of garbage collection is established based on measured WCET such that the execution time and overhead of garbage collection operations can be predicted. Finally, we illustrate a joint scheduling algorithm to meet the time and memory constraints of real-time systems.     

An Efficient Scheduling Discipline for Packet Switching Networks Using Earliest Deadline First Round Robin

This paper addresses a frame-oriented scheduling discipline, EDF-RR (earliest deadline first round robin), for OQ (output-queued) switch architecture and data traffic consisting of fixed-length cells. Bandwidth reservation for an active session is performed by holding a number of cell slots for the session in a repeatedly-transferred frame. Each cell that is going to be transferred in the frame is assigned a virtual release time and a virtual deadline according to the bandwidth reservation scheme. The transmitting order of the cells in the frame is determined by non-preemptive non-idling EDF algorithm so that cells of a backlogged session in the frame are distributed as uniformly as possible. Through the analysis applying real-time scheduling theory and network calculus as well as network simulation, EDF-RR takes the advantage of O(1) computational complexity, and possesses tight delay bounds and lenient buffer requirements. The proposed scheduling discipline is appropriate for distributed real-time systems as we show that sessions can be configured based on message traffic models and deadline requirements. Also, a modified version of EDF-RR, called EDF-DRR, can be applied as traffic regulator when jitter requirements exist among active sessions. This work was sponsored in part by the Federal Aviation Administration (FAA) via grant DTFA03-01-C-00042. Findings contained herein are not necessarily those of the FAA.     

A unified method for evaluating real-time computer controllers and its application

A computer-controlled system is a synergistic coupling of the controlled process and the controller computer. We have defined new performance measures for real-time controller computers based on this coupling. We present a systematic study of a typical critical controlled process in the context of new performance measures that express the performance of both controlled processes and controller computers (taken as a unit) on the basis of a single variable: controller response time. Controller response time is a function of current system state, system failure rate, electrical and/or magnetic interference, etc., and is therefore a random variable. Control overhead is expressed as monotonically nondecreasing function of the response time and the system suffers catastrophic failure, or dynamic failure, if the response time for a control task exceeds the corresponding system hard deadline, if any. The controlled-process chosen for study is an aircraft in the final stages of descent, just prior to landing. Control constraints are particularly severe during this period, and great care must be taken in the design of controllers that handle this process. First, the performance measures for the controller are presented. Second, control algorithms for solving the landing problem are discussed, and finally the impact of our performance measures on the problem is analyzed, showing that the performance measures and the associated estimation method have potential use for designing and/or evaluating real-time controllers and controlled process. In common with all other control techniques, the computational complexity involved in obtaining these measures is susceptible to the curse of dimensionality.