Static type information to improve the IDE features of hybrid dynamically and statically typed languages

The flexibility offered by dynamically typed programming languages has been appropriately used to develop specific scenarios where dynamic adaptability is an important issue. This has made some existing statically typed languages gradually incorporate more dynamic features to their implementations. As a result, there are some programming languages considered hybrid dynamically and statically typed. However, these languages do not perform static type inference on a dynamically typed code, lacking those common features provided when a statically typed code is used. This lack is also present in the corresponding IDEs that, when a dynamically typed code is used, do not provide the services offered for static typing. We have customized an IDE for a hybrid language that statically infers type information of dynamically typed code. By using this type information, we show how the IDE can provide a set of appealing services that the existing approaches do not support, such as compile-time type error detection, code completion, transition from dynamically to statically typed code (and vice versa), and significant runtime performance optimizations. We have evaluated the programmer׳s performance improvement obtained with our IDE, and compared it with similar approaches.     

Programmable mobile networks

Existing mobile systems (e.g., mobile IP, mobile ATM and third generation cellular systems) lack the intrinsic architectural flexibility to deal with the complexity of supporting adaptive mobile applications in wireless and mobile environments. We believe that there is a need to develop alternative network architectures from the existing ones to deal with the demands placed on underlying mobile signalling, adaptation management and wireless transport systems in support of new mobile services, e.g. interactive multimedia and web access. In this paper we present the design, implementation and evaluation of mobiware, a middleware technology that enables the introduction of new services in mobile networks. Mobiware provides a toolkit that service providers can utilize to build services that can dynamically exploit the intrinsic scalable properties of mobile multimedia applications in response to time-varying mobile network conditions. Based on an open programmable networking paradigm, mobiware runs on mobile devices, wireless access points and mobile-capable switch/routers providing a set of open programmable interfaces and distributed objects for adaptive mobile networking. Mobiware is software-intensive and is built on CORBA and Java distributed object technologies. The source code for mobiware v1.0 is freely available (comet.columbia.edu/mobiware) for experimentation.     

支持多类业务的移动Ad Hoc网络拓扑透明MAC调度码

设计了一类用于支持多种业务类型的移动自组织网络拓扑透明媒质接入控制(MAC)调度码。这类调度码保证最低优先级用户在一帧中至少有一个时隙成功传输信息的前提下,码长最小。这种调度码设计方案不仅简单易行,而且发送时隙选择灵活。性能分析表明,基于这类调度码的无线网络能够支持多个业务类型的用户,并为各类用户提供有保证的服务质量。     

An application adaptation layer for wireless sensor networks

In wireless sensor networks, poor performance or unexpected behavior may be experienced for several reasons, such as trivial deterioration of sensing hardware, unsatisfactory implementation of application logic, or mutated network conditions. This leads to the necessity of changing the application behavior after the network has been deployed. Such flexibility is still an open issue as it can be achieved either at the expense of significant energy consumption or through software complexity. This paper describes an approach to adapt the behavior of running applications by intercepting the calls made to the operating system services and changing their effects at run-time. Customization is obtained through small fragments of interpreted bytecode, called adaptlets, injected into the network by the base station. Differently from other approaches, where the entire application is interpreted, adaptlets are tied only to specific services, while the bulk of the application is still written in native code. This makes our system able to preserve the compactness and efficiency of native code and to have little impact on the overall application performance. Also, applications must not be rewritten because the operating system interfaces are unaffected. The adaptation layer has been implemented in the context of TinyOS using an instruction set inspired to the Java bytecode. Examples that illustrate the programming of the adaptation layer are presented together with their experimental validation.     

Mobile code paradigms and security issues

Programs are no longer constrained to execute on the nodes where they reside, and many systems therefore support code mobility. Although mobile code has yet to fully realize its promise of increased system flexibility, scalability, and reliability, the marketplace has embraced mobile code implementations such as Java.Jini, PostScript, and .NET. Several mobile code paradigms exist, and mobile code use raises many security concerns. Here, we map a taxonomy of mobile code paradigms to a taxonomy of network security vulnerabilities, revealing that many important security issues are being ignored.     

The SATIN Component System-A Metamodel for Engineering Adaptable Mobile Systems

Mobile computing devices, such as personal digital assistants and mobile phones, are becoming increasingly popular, smaller, and more capable. We argue that mobile systems should be able to adapt to changing requirements and execution environments. Adaptation requires the ability-to reconfigure the deployed code base on a mobile device. Such reconfiguration is considerably simplified if mobile applications are component-oriented rather than monolithic blocks of code. We present the SATIN (system adaptation targeting integrated networks) component metamodel, a lightweight local component metamodel that offers the flexible use of logical mobility primitives to reconfigure the software system by dynamically transferring code. The metamodel is implemented in the SATIN middleware system, a component-based mobile computing middleware that uses the mobility primitives defined in the metamodel to reconfigure both itself and applications that it hosts. We demonstrate the suitability of SATIN in terms of lightweightedness, flexibility, and reusability for the creation of adaptable mobile systems by using it to implement, port, and evaluate a number of existing and new applications, including an active network platform developed for satellite communication at the European space agency. These applications exhibit different aspects of adaptation and demonstrate the flexibility of the approach and the advantages gained     

一种基于Jini技术的移动Agent模型

移动Agent被普遍认为是一种有潜力的网络分布式计算技术,但至今仍没得到广泛的应用,主要是因为移动A-gent中尚存在一些主要问题,如环境灵活性、通信、代码迁移、安全等。针对这些问题,提出了一种基于Jini技术的移动Agent模型。通过将Jini中的查找、发现、租约、远程事件、对象存储等概念和服务加入到移动Agent中,创建了一个包含两种网络中间件(代理基站和代理站点)的动态分布式移动Agent模型,该模型提供了一种新的查找、通信、安全和容错方案以提高移动代理的健壮性、安全性和代理间的交互性。同时对该模型中关键技术的实现机制作了分析。     

移动数据业务管理平台研究

本文结合移动数据业务的发展趋势,给出了一种基于分布式组件技术的多层软件体系架构的移动数据业务管理平台DSMP的设计框架,提出了DSMP的体系架构模型,从系统门户 、应用服务、数据存储等方面探讨了DSMP子系统的具体设计和实现方法,在适应未来移动数据业务的灵活性、多样性、复杂性方面进行了探索和研究。     

A Novel Intermediary Framework for Dynamic Edge Service Composition

Multimedia content,user mobility and heterogeneous client devices require novel systems that are able to support ubiquitous access to the Web resources.In this scenario,solutions that combine flexibility,efficiency and scalability in offering edge services for ubiquitous access are needed.We propose an original intermediary framework,namely Scalable Intermediary Software Infrastructure (SISI),which is able to dynamically compose edge services on the basis of user preferences and device characteristics.The SISI framework exploits a per-user profiling mechanism,where each user can initially set his/her personal preferences through a simple Web interface,and the system is then able to compose at run-time the necessary components.The basic framework can be enriched through new edge services that can be easily implemented through a programming model based on APIs and internal functions.Our experiments demonstrate that flexibility and edge service composition do not affect the system performance.We show that this framework is able to chain multiple edge services and to guarantee stable performance.     

INSIGNIA: An IP-Based Quality of Service Framework for Mobile ad Hoc Networks

We present the design, implementation, and evaluation of INSIGNIA, an IP-based quality of service framework that supports adaptive services in mobile ad hoc networks. The framework is based on an in-band signaling and soft-state resource management approach that is well suited to supporting mobility and end-to-end quality of service in highly dynamic environments where the network topology, node connectivity, and end-to-end quality of service are time varying. Architecturally INSIGNIA is designed to support fast reservation, restoration, and end-to-end adaptation based on the inherent flexibility and robustness and scalability found in IP networks. We evaluate the framework, paying particular attention to the performance of the in-band signaling system, which helps counter time-varying network dynamics in support of the delivery of adaptive services. Our results show the benefit of our framework under diverse mobility, traffic, and channel conditions.     

手机二维码在国内的发展及应用

手机二维码是将二维条码和无线移动终端结合的产物,它一方面具有二维条码的特点,另一方面利用移动网络实现手机增值服务.文章介绍了手机二维码在国内的发展现状和成功应用案例.     

Advanced mobile agent security models for code integrity and malicious availability check

Mobile agent technology is an emerging paradigm in distributed computing environment and it holds a potential status in the relevant research field due to its unique capabilities like flexibility, dynamic customization and robust interaction in unreliable networks. But the limited security perspectives and shortfalls of the mobile agent environments degrade its usage in a variety of application domains. Even though some of the protection models are available for protecting the environments, they are not efficient in handling the security issues. To make the mobile agent environment secure, this paper proposed advanced models to improve the efficiency of the existing Malicious Identification Police model for scanning the incoming agent to detect the malicious activities and to overcome the availability of vulnerabilities in the existing Root Canal algorithm for code integrity checks. The MIP model is extended with the policy to differentiate the agent owners in the distributed environment and the Root Canal algorithm is improved as eXtended Root Canal algorithm. The experimental results of the advanced models show that though these mechanisms take more time complexity than the existing malicious identification police model and Root Canal model, these models are efficient in protecting the agent code integrity and scanning the agent for malicious activities. Also the new models possess less time complexity compared to the other related existing models in the secure mobile agent environment.     

CCM中应用服务器的研究与实现

传统的构件模型依赖于特定平台的底层服务,重用程度较低。本文遵循CCM3．0规范,深入阐述了CORBA分布构件模型的基本原理及其实现方案,并将底层服务与业务逻辑分离,降低了应用开发的复杂度,并达到了二进制代码级的重用,实现了服务端程序的跨平台与可维护。     

基于移动代理的主动网络

在介绍主动网络的基础上,提出了一个在移动代理系统基础上建立的安全而高效的主动网络系统框架MANet(mobile agents based active network).通过将程序代码和数据封装成主动数据包在主动结点上作为代理来运行,这个框架实现了集成化的主动网络,并且通过基于CodeBroker的代码装载和缓存技术改善了整个主动网络的性能和灵活性.     

Wukong: A cloud-oriented file service for mobile Internet devices

Along with the rapid growth of heterogeneous cloud services and network technologies, an increasing number of mobile devices use cloud storage services to enlarge their capacity and share data in our daily lives. We commonly use cloud service client-side software in a straightforward fashion. However, when more devices and users participate in heterogeneous services, the difficulty of managing these services efficiently and conveniently increases. In this paper, we report a novel cloud-oriented file service, Wukong, which provides a user-friendly and highly available facilitative data access method for mobile devices in cloud settings. Wukong supports mobile applications, which may access local files only, transparently accessing cloud services with a relatively high performance. To the best of our knowledge, Wukong is the first file service that supports heterogeneous cloud services for mobile devices by using the innovative storage abstraction layer. We have implemented a prototype with several plugins and evaluated it in a systematic way. We find that this easily operable file service has a high usability and extensibility. It costs about 50 to 150 lines of code to implement a new backend service support plugin. Wukong achieves an acceptable throughput of 179.11 kB/s in an ADSL environment and 80.68 kB/s under a countryside EVDO 3G network with negligible overhead.     

窃听攻击下子空间码的安全性

子空间码与随机线性网络编码相结合的网络系统具有编译码复杂度低、无需附加编码矢量和非相干通信等优点,曾被用于网络纠错。针对子空间码在窃听攻击下的安全性能,将攻击者猜测信源消息的成功概率作为子空间码的安全性度量。基于Cai和Yeung提出的网络窃听模型,采用线性代数和组合学方法,定量计算了攻击者的猜测概率并得到了闭式解。分析结果表明,子空间码具有概率意义下的弱安全性,但与许多完美安全或弱安全编码方案相比,子空间码具有复杂度低、灵活性高、拓扑不受限、可对抗多边窃听等优势,因此子空间码适用于计算受限且安全性能要求不高的应用。     

Personalised code generation from large schema sets for geospatial mobile applications

XML and XML Schema are used in the geospatial domain for the definition of standards that enhance the interoperability between producers and consumers of spatial data. The size and complexity of these geospatial standards and their associated schemas have been growing with time reaching levels of complexity that make it difficult to build systems based on them in a timely and cost-effective manner. The problem of producing XML processing code based on large schemas has been traditionally solved by using XML data binding generators. Unfortunately, this solution is not always effective when code is generated for resource-constrained devices, such as mobile phones. Large and complex schemas often result in the production of code with a large size and a complicated structure that might not fit the device limitations. In this article we present the instance-based XML data binding approach to produce more compact application-specific XML processing code for geospatial applications targeted to mobile devices. The approach tries to reduce the size and complexity of the generated code by using information about how schemas are used by individual applications. Our experimental results suggest a significant simplification of XML Schema sets to the real needs of client applications accompanied by a substantial reduction of size of the generated code.     

Hybrid weighted bit flipping low density parity check decoding

Low density parity check codes (LDPC) exhibit near capacity performance in terms of error correction. Large hardware costs, limited flexibility in terms of code length/code rate and considerable power consumption limit the use of belief-propagation algorithm based LDPC decoders in area and energy sensitive mobile environment. Serial bit flipping algorithms offer a trade-off between resource utilization and error correction performance at the expense of increased number of decoding iterations required for convergence. Parallel weighted bit flipping decoding and its variants aim at reducing the decoding iteration and time by flipping the potential erroneous bits in parallel. However, in most of the existing parallel decoding methods, the flipping threshold requires complex computations.In this paper, Hybrid Weighted Bit Flipping (HWBF) decoding is proposed to allow multiple bit flipping in each decoding iteration. To compute the number of bits that can be flipped in parallel, a criterion for determining the relationship between the erroneous bits in received code word is proposed. Using the proposed relation the proposed scheme can detect and correct a maximum of 3 erreneous hard decision bits in an iteration. The simulation results show that as compared to existing serial bit flipping decoding methods, the number of iterations required for convergence is reduced by 45% and the decoding time is reduced by 40%, by the use of proposed HWBF decoding. As compared to existing parallel bit flipping decoding methods, the proposed HWBF decoding can achieve similar bit error rate (BER) with same number of iterations and lesser computational complexity. Due to reduced number of decoding iterations, less computational complexity and reduced decoding time, the proposed HWBF decoding can be useful in energy sensitive mobile platforms.     

The relationship between quality of service perceived and delivered in mobile Internet communications

Today mobile network operators offer a wide variety of mobile Internet services to their customers including mobile email, banking, and news services. The acceptance of these services is heavily based on quality of service (QoS) experienced by the user. So far the discussion of QoS has been very network centric and the key to user satisfaction has been the network performance. In this paper we analyze the relationship between QoS perceived by the customer and network performance offered by the service provider. We conduct a lab experiment where network performance variables were controlled. Statistical analysis of the results indicates that there is no 1:1 correspondence or even truly linear relationship between network performance and perceived QoS as recommended by the International Telecommunications Union-Telecommunication (ITU-T). Instead the relationship varied from application to application. We examine several usability factors as potential reasons behind this phenomenon and make suggestions for future research.     

Designing a videoconference system for active networks

Active networks are receiving increasing attention due to their promise of great flexibility in tailoring services to applications. This capability stems from the exploitation of network devices whose behaviour can be changed dynamically by applications, possibly using technologies and architectures originally conceived for mobile code systems. Notwithstanding the promise of active networks, real-world applications that clearly benefit by them are still missing. In this paper we describe the design of a videoconference system conceived expressly for operation over active networks. The goal of this activity is to pinpoint the benefits that mobile code and active networks bring to this application domain and to provide isnights for the exploitation of these concepts in other application domains.