A control-based middleware framework for quality-of-serviceadaptations

In heterogeneous environments with performance variations present, multiple applications compete for and share a limited amount of system resources and suffer from variations in resource availability. These complex applications are desired to adapt themselves and to adjust their resource demands dynamically. On one hand, current adaptation mechanisms built within an application cannot preserve global properties such as fairness; on the other hand, adaptive resource management mechanisms built within the operating system are not aware of data semantics in the application. In this paper, we present a novel middleware control framework to enhance the effectiveness of quality-of-service (QoS) adaptation decisions by dynamic control and reconfiguration of internal parameters and functionalities of a distributed multimedia application. Our objective is to satisfy both system-wide properties (such as fairness among concurrent applications) and application-specific requirements (such as preserving the critical performance criteria). The framework is modeled by the task control model and the fuzzy control model, based on rigorous results from the control theory, and verified by the controllability and adaptivity of a distributed visual tracking application. The results show validation of the framework, i.e., critical application quality parameters can be preserved via controlled adaptation     

Adaptive systems for improved media streaming experience

Supporting streaming media applications over current packet network infrastructures represents a challenging task in many regards. For one, the lack of quality of service (QoS) guarantees in existing networks such as the Internet means that time-constrained media packets will face dynamic variations in bandwidth, loss rate, and delay as they traverse the network from the sender to the receiver. The variable rate of media traffic represents yet another difficulty when transmission constraints need to be met. Finally, the heterogeneity of client devices and access bandwidth coupled with custom user preferences exacerbate the problem of smooth and quality-optimized media playback even further. In this article we provide an overview of the various techniques for media and streaming strategy adaptation, which can be employed to deal with the difficulties imposed by such dynamic environments. These techniques depend on the characteristics of the media application, in particular on the network streaming infrastructure and the timing constraints imposed on the media packets' delivery. We survey adaptation techniques that act on the encoding of the multimedia information, on the scheduling of the media packets, or that try to combat transmission errors. We also briefly overview some media-friendly networking solutions, which contribute to increased QoS by incorporating some level of intelligence in intermediate network nodes. Finally, we describe a few open challenges in media streaming, emphasizing strategies based on promising cross-layer approaches where adaptation strategies are applied in a coordinated manner, across different layers of the network protocol stack     

动态测试中的参数校准

由于动态测试所需要测试的动态参数持续时间很短,且频率成分丰富,所以对测试系统的精度提出了很高的要求,对动态测试过程中的各种参量进行校准就显得尤为必要。本文结合一个具体的应用环境设计了一套专门的动态测试参数校正系统,重点介绍了该校正系统的原理,并较为详尽地分析了不同环境对系统的影响,给出了动态测试参数校正系统的设计方案。     

Middleware to support sensor network applications

Current trends in computing include increases in both distribution and wireless connectivity, leading to highly dynamic, complex environments on top of which applications must be built. The task of designing and ensuring the correctness of applications in these environments is similarly becoming more complex. The unified goal of much of the research in distributed wireless systems is to provide higher-level abstractions of complex low-level concepts to application programmers, easing the design and implementation of applications. A new and growing class of applications for wireless sensor networks require similar complexity encapsulation. However, sensor networks have some unique characteristics, including dynamic availability of data sources and application quality of service requirements, that are not common to other types of applications. These unique features, combined with the inherent distribution of sensors, and limited energy and bandwidth resources, dictate the need for network functionality and the individual sensors to be controlled to best serve the application requirements. In this article, we describe different types of sensor network applications and discuss existing techniques for managing these types of networks. We also overview a variety of related middleware and argue that no existing approach provides all the management tools required by sensor network applications. To meet this need, we have developed a new middleware called MiLAN. MiLAN allows applications to specify a policy for managing the network and sensors, but the actual implementation of this policy is effected within MiLAN. We describe MiLAN and show its effectiveness through the design of a sensor-based personal health monitor.     

Mobile agent based framework for mobile ubiquitous application development

Ubiquitous computing which enabled by the availability of mobile, heterogeneous devices that supply context information, is currently not matured by the lack of programming support for the design and development of context-aware applications. Especially, ubiquitous computing environment is not static which can be compensable dynamically according to need of environment. Mobile agent is a very efficient framework applications can cooperative in heterogeneous environment. Therefore, we have developed a mobile agent based framework that significantly eases the development of mobile, context-aware applications. The framework allows developers to fuse data from disparate sensors, represent application context, and reason efficiently about context, without the need to write complex code. An event based communication paradigm designed specifically for ad-hoc wireless environments is incorporated, which supports loose coupling between sensors, actuators and application components.     

An infrastructure for social software

In a virtual world, as DVE (distributed virtual environment) applications are often called, logistic support must be supplied by software. As the range of DVE applications expands, they will need software support of a kind rarely envisioned by previous generations of programmers. A new breed of programs is required: social software. The overriding point of social software is not simulation but conversation. Its applications are not substitutes for real-world interaction, but extensions of it. Its “worlds” are not virtual in the customary sense; they are real media for meeting others online. Designers of social software are less concerned with how well their on-screen objects mimic real-world objects than with how well they connect their users to each other. Simulation environments can be thought of as being like the “preview” mode of a word processor, designed to match the look of a printed document. Social environments, by comparison, are like hypertext, opening up avenues of communication that were unforeseen in the media that preceded them. The disparate programs meant for virtual worlds will need a common platform to underpin widespread social interaction     

Adaptive action selection without explicit communication formultirobot box-pushing

The paper describes a novel action selection method for multiple mobile robots box-pushing in a dynamic environment. The robots are designed to need no explicit communication and be adaptive to dynamic environments by changing modules of behavior. The various control methods for a multirobot system have been studied both in centralized and decentralized approaches, however, they needed explicit communication such as a radio, though such communication is expensive and unstable. Furthermore, though it is a significant issue to develop adaptive action selection for a multirobot system to a dynamic environment, few studies have been done on it. Thus, we propose action selection without explicit communication for multirobot box-pushing which changes a suitable behavior set depending on a situation for adaptation to a dynamic environment. First, four situations are defined with two parameters: the existence of other robots and the task difficulty. Next, we propose an architecture of action selection which consists of a situation recognizer and sets of suitable behaviors to the situations and carefully design the suitable behaviors for each of the situations. Using the architecture, a mobile robot recognizes the current situation and activates the suitable behavior set to it. Then it acts with a behavior-based approach using the activated behaviors and can change the current situation when the environment changes. We fully implement our method on four real mobile robots and conduct various experiments in dynamic environments. As a result, we find out our approach is promising for designing adaptive multirobot box-pushing     

Adaptive Dissemination of Data in Time-Critical Asymmetric Communication Environments

The proliferation of new data-intensive applications in asymmetric communication environments has led to an increasing interest in the development of push-based techniques, in which the information is broadcast to a large population of clients in order to achieve the most efficient use of the limited server and communication resources. It is important to note that quite often the data that is broadcast is time-critical in nature.Most of the related current research focuses on a pure push-based approach (Broadcast Disks model), where the transmission of data is done without allowing explicit requests from the users. More recently, some bidirectional models incorporating a low-capacity uplink channel have been proposed in order to increase the functionality of the Broadcast Disks model. However, the impact of integration of the uplink channel has been investigated using only static client profiles or ignoring the existence of time-sensitive data. None of the existing models integrates all the characteristics needed to perform effectively in a real-world, dynamic time-critical asymmetric communication environment.In this paper we present an adaptive data dissemination model and the associated on-line scheduling algorithms. These improve the functionality and performance of bidirectional broadcast models, maximizing the total number of satisfied users in asymmetric communication environments with dynamic client profiles and time requirements (e.g., mobile systems). This is achieved by means of dynamic adaptation of the broadcast program to the needs of the users, taking into account the bandwidth constraints inherent in asymmetric communication environments and the deadline requirements of the user requests. Performance is evaluated by simulation of a real-time asymmetric communication environment.     

Disconnection Modes for Mobile Databases

As mobility permeates into todays computing and communication arena, we envision application infrastructures that will increasingly rely on mobile technologies. Traditional database applications and information service applications will need to integrate mobile entities: people and computers. In this paper, we develop a distributed database framework for mobile environments. A key requirement in such an environment is to support frequent connection and disconnection of database sites. We present algorithms that implement this framework in an asynchronous system.     

Adaptation Mechanisms for Transactions in Mobile Computing Environments

Advances in wireless communication technologies and portable computers have turned mobile computing into a reality. These environments are characterized by a high dynamism that can hamper the execution of applications. This paper presents a set of adaptation mechanisms that can be used within a transaction context to overcome the high dynamism and resource restrictions of the mobile environment. Three adaptation mechanisms were proposed: isolation level, operation mode and transaction mobility.     

A programmable MAC framework for utility-based adaptive quality ofservice support

We describe the design and evaluation of a programmable medium access control framework which is based on a hybrid centralized/distributed data link controller. The programmable framework and its associated algorithms are capable of supporting adaptive real-time applications over time-varying and bandwidth limited networks (e.g., wireless networks) in a fair and efficient manner taking into account application-specific adaptation needs. The framework is flexible, extensible and supports the dynamic introduction of new adaptive services on-demand. As part of the service creation process, applications interact with a set of distributed adaptation handlers to program services without the need to upgrade the centralized adaptation controller. This approach is in contrast to existing techniques that offer a fixed set of “hard-wired” services at the data link from which applications select. We present a framework where a centralized adaptation controller responsible for the fair allocation of available bandwidth among adaptive applications is driven by application specific bandwidth utility curves. A set of distributed adaptation handlers execute at edge devices interacting with a central controller allowing applications to program their adaptation needs in terms of utility curves, adaptation time scales and adaptation policy. The central controller offers a set of simple meta-services called “profiles” that distributed handlers use to build sophisticated adaptive real-time services     

Ocean parameter adaptive time synchronization algorithm for ocean sensor network

An ocean parameter adaptive time synchronization (OPA-Sync) algorithm was proposed,which based on the influence of ocean parameters in different conditions.It improved the adaptation of time synchronization algorithm by adjusting the ocean parameters in the complex and varied environment.And the algorithm was optimized to improve the operation efficiency.Simulation results show that OPA-Sync can be adapted to different ocean environments,which is better than other existing time synchronization algorithms on the synchronization precision and efficiency.     

Quantitative analysis of visibility determinations for networked virtual environments

The Area-Of-Interest (AOI) model is a simple and popular technique used in many applications to determine the region which needs to be considered and processed for each entity (e.g., user). One example application is object visibility determination around user-representing avatars in virtual environments or networked games. There exist a number of variations of the AOI model and in our prior work we have demonstrated how object-oriented visibility determination is more suitable for networked virtual environments than conventional user-oriented visibility determination. Here we extend our work to study a unified and comprehensive analytical model that reveals fundamental properties about the different visibility determination techniques under a variety of virtual environment settings. We also present what the best operational scenarios are for each different approach. Although our discussion and analytical results are focused on the visibility domain, the arguments and conclusions can be extended to various applications or services where spatial attributes are required.     

Adaptive rate-controlled scheduling for multimedia applications

We present a framework for integrated scheduling of continuous media (CM) and other applications. The framework, called ARC scheduling, consists of a rate-controlled on-line CPU scheduler, an admission control interface, a monitoring module, and a rate adaptation interface. ARC scheduling allows threads to reserve CPU time for guaranteed progress. It provides firewall protection between threads such that the progress guarantee to a thread is independent of how other threads actually make scheduling requests. Rate adaptation allows a CM application to adapt its rate to changes in its execution environment. We have implemented the framework as an extension to Solaris 2.3. We present experimental results which show that ARC scheduling is highly effective for integrated scheduling of CM and other applications in a general purpose workstation environment. ARC scheduling is a key component of an end system architecture we have designed and implemented to support networking with quality of service guarantees. In particular, it enables protocol threads to make guaranteed progress     

Protection Management for Guaranteed User‐Driven Virtual Circuit Services in Dynamic Multi‐domain Environments: Design Issues and Challenges

Fault management of virtualized network environments using user‐driven network provisioning systems (NPSs) is crucial for guaranteeing seamless virtual network services irrespective of physical infrastructure impairment. The network service interface (NSI) of the Open Grid Forum reflects the need for a common standard management API for the reservation and provisioning of user‐driven virtual circuits (VCs) across global networks. NSI‐based NPSs (that is, network service agents) can be used to compose user‐driven VCs for mission‐critical applications in a dynamic multi‐domain. In this article, we first attempt to outline the design issues and challenges faced when attempting to provide mission‐critical applications using dynamic VCs with a protection that is both user‐driven and trustworthy in a dynamic multi‐domain environment, to motivate work in this area of research. We also survey representative works that address inter‐domain VC protection and qualitatively evaluate them and current NSI against the issues and challenges.     

Dynamic Reconfiguration Based on Goal-Scenario by Adaptation Strategy

The self-adaptation of software systems is a complex process that depends on several factors that can change during the system operational lifetime. But, Today’s workflow management systems are only applicable in a secure and safe manner if the business process to be supported is well-structured and there is no need for ad hoc deviations at runtime. Hence, it is necessary to define mechanisms for providing a self-adaptive system the capability of reconfiguration during run-time the process that controls its adaptation. In this paper, we provide rapid dynamic reconfiguration using the workflow based on goal-scenario as the basis to set up strategies in accordance with the adaptive judgment. Also, we provide a sophisticated approach which fosters learning from past process changes by process variants through the order matrix. We present a formal foundation for the support of dynamic structural workflow changes of running. Our approach uses estimates based goal-scenario to determine which remaining parts of running workflows are affected by the external environment and is able to predictively perform suitable adaptation. This helps to ensure that necessary adaptation are performed in time with minimal user interaction which is especially valuable in change of external environment.     

Dynamic Multiresolution Data Dissemination in Wireless Sensor Networks

Recent years have seen the deployments of wireless sensor networks (WSNs) in a variety of applications to gather the information about physical environments. A key requirement of many data-gathering WSNs is to deliver the information about dynamic physical phenomena to users at multiple temporal resolutions. In this paper, we propose a novel solution called the Minimum Incremental Dissemination Tree (MIDT) for dynamic multiresolution data dissemination in WSNs. MIDT includes an online tree construction algorithm with an analytical performance bound and two lightweight tree adaptation heuristics for handling data requests with dynamic temporal resolutions. Our simulations based on realistic settings of Mica2 motes show that MIDT outperforms several typical data dissemination schemes. The two tree adaptation heuristics can effectively maintain desirable energy efficiency of the dissemination tree while reducing the overhead of tree reconfigurations under representative traffic patterns in WSNs.     

Transit tomography using probabilistic time geography: planning routes without a road map

There is a diversity of ways to determine a user's location in a pervasive environment today. On a large scale, this diversity often results in variability of location tracking conditions throughout the environment. For an important class of pervasive applications, which often rely on the ubiquitous availability of location tracking – location-based pervasive applications, the consistency of their behaviour under this variability cannot be guaranteed. This type of limitation raises a need for the adaptation of the application's behaviour that would reflect this variability. We investigated empirically how visualising different aspects of uncertainty about location and of the behaviour of localisation systems affects users’ impressions about a location-based application. The two components – an ontology that models properties of localisation systems and a set of mapping rules that define how these properties should be visualised in a user interface – are at the core of our approach to providing awareness. The results of the investigation show that the additional visual demand, intended for raising users’ awareness of uncertainty about their location tracking conditions, is perceived to be beneficial by users. We also reveal that different characteristics of this awareness are of different importance to users. Furthermore, we conclude that the particular importance depends on users’ personal profiles (e.g. their eyesight level), on the distance between the users (e.g. knowing about someone else's state is less important if they are far) and on the quality of tracking (the importance increases in problematic areas). On the basis of the obtained results and observations, we suggest a set of guidelines and visualisations, which could be used in designing pervasive applications that require location tracking.     

On optimal batch rekeying for secure group communications in wireless networks

Advances in wireless communications and mobile computing have led to the emergence of group communications and applications over wireless. In many of these group interactions, new members can join and current members can leave at any time, and existing members must communicate securely to achieve application-specific missions or network-specific functionality. Since wireless networks are resource-constrained, a key challenge is to provide secure and efficient group communication mechanisms that satisfy application requirements while minimizing the communication cost. Instead of individual rekeying, i.e., performing a rekey operation right after each join or leave request, periodic batch rekeying has been proposed to alleviate rekeying overhead in resource-constrained wireless networks. In this paper, we propose an analytical model to address the issue of how often batch rekeying should be performed. We propose threshold-based batch rekeying schemes and demonstrate that an optimal rekey interval exists for each scheme. We further compare these schemes to identify the best scheme that can minimize the communication cost of rekeying while satisfying application requirements when given a set of parameter values characterizing the operational and environmental conditions of the system. In a highly dynamic wireless environment in which the system parameter values change at runtime, our work may be used to adapt the rekeying interval accordingly.     

Temperature control with a neural fuzzy inference network

Although multilayered backpropagation neural networks (BPNNs) have demonstrated high potential in adaptive control, their long training time usually discourages their applications in industry. Moreover, when they are trained online to adapt to plant variations, the over-tuned phenomenon usually occurs. To overcome the weakness of the BPNN, we propose a neural fuzzy inference network (NFIN) suitable for adaptive control of practical plant systems in general and for adaptive temperature control of a water bath system in particular. The NFIN is inherently a modified Takagi-Sugeno-Kang (TSK)-type fuzzy rule based model possessing a neural network's learning ability. In contrast to the general adaptive neural fuzzy networks, where the rules should be decided in advance before parameter learning is performed, there are no rules initially in the NFIN. The rules in the NFIN are created and adapted as online learning proceeds via simultaneous structure and parameter identification. The NFIN has been applied to a practical water bath temperature control system. As compared to the BPNN under the same training procedure, the simulated results show that not only can the NFIN greatly reduce the training time and avoid the over-tuned phenomenon, but the NFIN also has perfect regulation ability. The performance of the NFIN is compared to that of the traditional PID controller and fuzzy logic controller (FLC) on the water bath temperature control system. The three control schemes are compared, with respect to set point regulation, ramp-point tracking, and the influence of unknown impulse noise and large parameter variation in the temperature control system. The proposed NFIN scheme has the best control performance