A General Buffer Scheme for the Windows Scheduling Problem

Broadcasting is an efficient alternative to unicast for delivering popular on-demand media requests. Broadcasting schemes that are based on windows scheduling algorithms provide a way to satisfy all requests with both low bandwidth and low latency. Consider a system of n pages that need to be scheduled (transmitted) on identical channels an infinite number of times. Time is slotted, and it takes one time slot to transmit each page. In the windows scheduling problem (WS) each page i, 1 ≤ i ≤ n, is associated with a request window wi. In a feasible schedule for WS, page i must be scheduled at least once in any window of wi time slots. The objective function is to minimize the number of channels required to schedule all the pages. The main contribution of this paper is the design of a general buffer scheme for the windows scheduling problem such that any algorithm for WS follows this scheme. As a result, this scheme can serve as a tool to analyze and/or exhaust all possible WS-algorithms. The buffer scheme is based on modelling the system as a nondeterministic finite state machine in which any directed cycle corresponds to a legal schedule and vice-versa. Since WS is NP-hard, w

Efficient Broadcast Disks Program Construction in Asymmetric Communication Environments

ABSTRACT A well-known technique for broadcast program construction is the Broadcast Disks. However, it has important disadvantages, as for example that the broadcast program construction procedure leaves some parts of the broadcast program empty. This paper proposes a new approach for the construction of the broadcast program. Specifically, it presents three new algorithms, which face the problems of the Broadcast Disk Technique. According to our approach, the broadcast program is constructed with the minimum possible length, respecting the selected disk relative frequencies and keeps the average delays of retrieving data-items low. The constructed broadcast programs have no empty parts and retain their desired properties in any combination of disk relative frequencies. Experimental results show that this approach is more efficient than Broadcast Disks in all cases

Continuous Access of Broadcast Data Using Artificial Pointers in Wireless Mobile Computing

In a ubiquitous information environment, massive number of users carrying their portable computers can retrieve information anywhere and anytime using wireless mobile computing technologies. Wireless data broadcasting as a way of disseminating information to the large number of clients, has an inherent advantage by providing all types of users global access to information. An adaptive access method, which tolerates the access failure, has been proposed in an error-prone mobile environment. However the influence of version bits to deal with the updates of the broadcast data has not been exploited for the broadcast with modified but the same size and structure update. The basic idea is to distinguish the type of update that does not influence the change in the size and structure of the broadcast has been introduced. To deal with the types of updates, we classified the users in mobile computing environment into the users in system and the new users. In the proposed continuous algorithms, the user in systems record the previous result and use it efficiently to access the desired records with less number of probes in the broadcast, which is updated by a stream of same size and structure bits. In the performance analysis, the experimental results show that the proposed modified progression method has the best performance, as it requires the minimum cost to access the broadcast data

Real-Time Mutable Broadcast Disks

There is an increased interest in using broadcast disks to support mobile access to real-time databases. However, previous work has only considered the design of real-time immutable broadcast disks, the contents of which do not change over time. This paper considers the design of programs for real-time mutable broadcast disks - broadcast disks whose contents are occasionally updated. Recent scheduling-theoretic results relating to pinwheel scheduling and pfair scheduling are used to design algorithms for the efficient generation of real-time mutable broadcast disk programs.National Science Foundation (CCR-9706685, CCR-9596282