57544361
Feasibility analysis of hard real-time periodic tasks
The problem of determining the feasibility of hard real-time periodic tasks is known to be co-NP-complete when there exists a task with relative deadline shorter than its period. Thus "Processor Demand Approach (PDA)" for synchronous task sets has been considered as a practical tool to solve the feasibility problem. PDA determines the feasibility of a task set by checking whether there exists a task whose deadline is missed by a certain time which is computed based on the characteristic of the task set. In this paper, we present a new method for feasibility test by combining PDA with the analysis methods for aperiodic scheduling. It is shown that the number of tests required of the new method to determine the feasibility is never greater than the smallest number of tests the existing algorithm requires. Although our method has pseudo-polynomial time complexity, experimental results show that the new method requires significantly less computation to determine feasibility.
5446721
An efficient stream authentication scheme using tree chaining
Recently, the Internet is widely used for distributing stream data. To enable widespread commercial stream services, it is very important to provide data authentication and non-repudiation [1,4]. There are three issues to consider for authenticating live streams. First, for the sender, an authentication scheme must be efficient to support fast packet rates. Second, for receivers, the authentication scheme must assure a high verification probability in spite of a large packet loss (the verification probability is defined as a ratio of verifiable packets to received packets) [4]. Moreover, considering that lots of streams such as stock quote or traffic information have short lifetimes and that audio/video streams have to be played continuously, the verification of each received packet should be done within a short deadline. Third, communication overhead must be low. To achieve these goals, stream authentication schemes amortize each computation-
27314826
Rapid visualization of geometric information in a construction environment
A construction workspace is a dynamic environment that allows little time to obtain and update the graphical and image modeling information that is required in construction equipment operations. Comprehensive 3D models of the workspace require computationally intensive and expensive imaging processing, and usually take much longer than the ongoing construction operations permit. Rapid 3D positioning and modeling in construction can be used to plan, visualize and communicate operations before execution. They can also help to optimize equipment operations, significantly improve safety and enhance a remote operator's spatial perception of the workspace. This paper presents a rapid method, by combining human-assisted graphical workspace modeling with pre-stored CAD models and simple sensors (such as single-axis laser range-finders and remote video cameras), which can significantly reduce the modeling time while potentially increasing the modeling accuracy.
5710671
Distributed management architecture for multimedia conferencing using SIP
As various multimedia communication services are increasingly required by Internet users, several signaling protocols have been proposed for the efficient control of multimedia communication services. However, the model and architecture of multimedia conferencing which is currently being standardized by IETF is not suitable to meet the requirement for the management of large-scale multimedia conferencing service. In this paper, we have presented a management mechanism for distributed architecture of large scale multimedia conferencing service which is based on SIP. The high scalability is achieved by the coordinated distributed conference control and associated media processing without disruption of services. The SIP-based control mechanism for achieving the scalability has been designed in detail. Finally, the performance of the proposed architecture has been evaluated by simulation.