The newly emerging wireless backhaul network has fundamental difficulties in supporting Voice over IP (VoIP) applications due to the MAC overheads introduced by huge amounts of small packets. Packet aggregation is a promising approach to mitigate these overheads. However, previous approaches to such problems are often stringent, not adaptive to the change of channel conditions. They are operated by each TAP (Transit Access Point) separately without any coordination in the use of shared channels. As a result, they fail to ensure the VoIP quality in terms of delay and loss. The major contribution of this paper is the proposal of a coordinated aggregation algorithm, which is adaptive and distributed. By coordinating with neighboring TAPs, the proposed algorithm is able to assign an appropriate aggregation rate to each TAP, aiming at better channel utilization and lower packet loss and delay. We evaluate this design by comprehensive analysis and simulations. The simulation results show that our algorithm significantly improves the VoIP capacity in wireless backhaul networks and outperforms existing aggregation algorithms.

With the invention of new interaction devices and the requirements for ubiquitous access to application systems, user's interactions have moved beyond the desktop and evolved into a trend of ongoing development. The context in which the application is being used becomes an integral part of the activity carried out with the system. The inclusion of context-awareness provides convenience and efficiency to users for their ubiquitous access. Traditional human-computer interface (HCI) theories are now inadequate for developing these context-aware applications, as we believe that the notion of context should be extended to different categories: computing contexts, user contexts, and physical contexts for ubiquitous computing. This demands a new paradigm for system requirements elicitation and design in order to make good use of such extended context information. In this paper, we introduce a methodology for the elicitation of context-aware requirements and the matching of context-awareness features to the target context by capability matching. Based on this model, we analyze the design issues of some common ubiquitous access situations and show how to fit them systematically into a context-aware application by considering the requirements of a ubiquitous tourist application. Copyright 2005 ACM.

Context-aware applications can better meet users' needs when sensing agents installed in the environment automatically provide input relevant to the application. However, this non-intrusive context usage may cause privacy concerns since sensitive user data could be leaked to unauthorized parties. Therefore, data privacy protection becomes one of the major issues for context-aware applications. In this paper, in order to provide services based on various levels of privacy concerns, we extend the Platform for Privacy Preferences of W3C and define a specification for representing user privacy preferences for context-aware applications. We also propose a privacy infrastructure, which could be installed as a plug-in service for middleware supporting context-aware applications. This infrastructure enables the middleware to automatically generate a privacy policy and the user preference file according to the current context. The middleware simply matches these two files to decide whether to proceed with the application. We demonstrate the efficacy of this approach through a prototype implementation.

Results are presented of an analysis of several defect models using data collected from two large commercial projects. Traditional models typically use either program matrices (i.e. measurements from software products) or testing time or combinations of these as independent variables. The limitations of such models have been well-documented. The models considered use the number of defects detected in the earlier phases of the development process as the independent variable. This number can be used to predict the number of defects to be detected later, even in modified software products. A strong correlation between the number of earlier defects and that of later ones was found. Using this relationship, a mathematical model was derived which may be used to estimate the number of defects remaining in software. This defect model may also be used to guide software developers in evaluating the effectiveness of the software development and testing processes.>

A major portion of the effort expended in developing commercial software today is associated with program testing. Schedule and/ or resource constraints frequently require that testing be conducted so as to uncover the greatest number of errors possible in the time allowed. In this paper we describe a study undertaken to assess the potential usefulness of various product-and process-related measures in identifying error-prone software. Our goal was to establish an empirical basis for the efficient utilization of limited testing resources using objective, measurable criteria. Through a detailed analysis of three software products and their error discovery histories, we have found simple metrics related to the amount of data and the structural complexity of programs to be of value for this purpose.

The theory of software science was developed by the late M. H. Halstead of Purdue University during the early 1970's. It was first presented in unified form in the monograph Elements of Software Science published by Elsevier North-Holland in 1977. Since it claimed to apply scientific methods to the very complex and important problem of software production, and since experimental evidence supplied by Halstead and others seemed to support the theory, it drew widespread attention from the computer science community.

Abstract When a document is prepared using a computer system, it can be checked for spelling errors automatically and efficiently. This paper reviews and compares several methods for searching an English spelling dictionary. It also presents a new technique, hash‐bucket search, for searching a static table in general, and a dictionary in particular. Analysis shows that with only a small amount of space beyond that required to store the keys, the hash‐bucket search method has many advantages over existing methods. Experimental results with a sample dictionary using double hashing and the hash‐bucket techniques are presented.

The evaluation of programmers' performance has been an important subjecl in recent years. Making the reasonable assumption that a good programmer would consistently write programs of high quality, the problem of evaluation would be simplified if an objective measure of quality were available which could be applied to a sample program. This paper describes an experiment to study the relationship between grades in a programming course, which are the accepted evaluations of student programmers, and certain objectively computed software science parameters on program samples. The data shows that two of the parameters are correlated to the grades.

The study of abstract models of computer systems using deterministic methods has produced sigmficant insight into the behavior of such systems in recent years This paper considers a model of a minicomputer network which consists of an arbitrary number of identical processors Each processor in the network has a fixed, though possibly different sized, private memory The network processes a set of tasks with known execution times and memory requirements One of the problems a designer of such a network must solve is to determine the memory sizes for such a system Algorithms to determine the memory configuration are presented and analyzed using worst-case bounds and computer s~mulation KEY WORDS AND PHRASES deterministic models, design algorithms, system configuration, computer networks, multiprocessor systems CR CATE(,ORIES 4 32, 5 39 General

No abstract available.

This paper considers a model of a computing system with several independent but identical processors, each with a private memory of limited, and possibly different, storage capacity. The tasks are assumed to have known resource demands expressed as processing times and memory requirements. Several scheduling strategies are evaluated by worst-case performance bounds and simulation results. Both preemptive and nonpreemptive scheduling are considered. An optimal preemptive algorithm is given to find the shortest schedule for a task set with no precedence constraints.

ABST~tACT.In multiprogramming computer systems, the scheduling strategy used to select tasks to be activated is an important factor in the achievement of the performance goals of the system.One form of analysm of scheduling algorithms represents the system as an abstract model of computation and then formally analyzes the algorithms operating in the context of the model.This paper presents an abstract system model which consists of several identical and independent task processors and a memory of arbitrary size Tasks are represented by processing-time and memory requirements which must be met by the model.Worst-case performance bounds are derived for sever al simple scheduling algortthms.A new heuristic algorithm, which uses a look-ahead strategy, is introduced This algorithm is shown to be better in many cases than the simpler algorithms when the worst-case performance bounds are compared.

This paper presents a description and analysis of a task scheduling algorithm which is applicable to third generation computer systems. The analysis is carried out using a model of a computer system having several identical task processors and a fixed amount of memory. The algorithm schedules tasks having different processor-time and memory requirements. The goal of the algorithm is to produce a task schedule which is near optimal in terms of the time required to process all of the tasks. An upper bound on the length of this schedule is the result of deterministic analysis of the algorithm. Computer simulations demonstrate the applicability of the algorithm in actual systems, even when some of the basic assumptions are violated.

An algorithm for obtaining all simple disjunctive decompositions of a switching function is described. It operates on a function given as an expression using the operations AND, EXCLUSIVE OR, and complementation. It uses necessary conditions for the existence of a decomposition to eliminate sets of bound sets from consideration. Thus this technique differs from existing methods in that it attempts to test fewer bound sets at the expense of additional analysis. The algorithm can also be applied to functions given in a canonical form. It is shown that for a collection of functions of n variables chosen at random, the time required grows as n3. Previous methods, on the other hand, have an exponential growth rate.

An algorithm for obtaining all simple disjunctive decompositions of a switching function is described. The algorithm proceeds by testing for all decompositions with a bound set of size two. Under given conditions, this test for a pair of variables will show that some larger bound sets, containing the two variables for which the test was conducted, cannot yield a decomposition. The remaining bound sets require further testing. Thus this algorithm differs from existing techniques in that it attempts to test fewer bound sets at the expense of additional analysis. The relative merit of this algorithm is discussed.