A simulation scheme which fully reflects the 3D nature of tunable multi-section distributed Bragg reflector lasers is presented. In the simulator used for this work, 3D charge carrier transport is modeled by the drift...
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The ongoing challenge of supporting high performance communications, real-time critical and secure applications leads to a shift from traditional IP networks towards a more intelligent, end-to-end, service-aware netwo...
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ISBN:
(纸本)0769519210
The ongoing challenge of supporting high performance communications, real-time critical and secure applications leads to a shift from traditional IP networks towards a more intelligent, end-to-end, service-aware network paradigm. Future networks have to i) be more content or application-aware;ii) provide dynamic features for service creation;iii) observe and enforce network-wide policies;and finally, iv) enable control from the network provider to the end-user. This paper presents the technical aspects of a policy based auditing system for a QoS-enabled network. The goal is to define the architecture of policy-based network QoS control and to develop and implement a prototype to evaluate this architecture.
Wireless mobile devices (mobile phones or PDAs) gain more and more simultaneous access to different physical access networks like GSM, UMTS or Wireless LAN. This paper analyzes and describes how digital broadcast netw...
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ISBN:
(纸本)0769519210
Wireless mobile devices (mobile phones or PDAs) gain more and more simultaneous access to different physical access networks like GSM, UMTS or Wireless LAN. This paper analyzes and describes how digital broadcast networks like DAB and DVB can be used for mobile devices. A communication model is provided which allows optimized dynamic selection of up- and downstreams according to particular communication needs. Further a testbed, containing a DAB transmitter, a DAB receiver and software components, is introduced.
Locating suitable resources within a Peer-2-Peer (P2P) system is a computationally intensive process, with no guarantee of quality and suitability of the discovered resources. An alternative approach is to categorise ...
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ISBN:
(纸本)0769520235
Locating suitable resources within a Peer-2-Peer (P2P) system is a computationally intensive process, with no guarantee of quality and suitability of the discovered resources. An alternative approach is to categorise peers based on the services they provide - leading to the interaction between peers with common goals to form societies/communities. Organization of peers in different communities is suggested to be useful for efficient resource discovery. We analyse the types of communities that may be useful, and how they may be structured.
Server replication is a common approach to improving. the scalability of a service on the Internet. For this approach, the task of finding an appropriate server from a set of replicas is a critical issue. We. have pro...
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ISBN:
(纸本)0769519210
Server replication is a common approach to improving. the scalability of a service on the Internet. For this approach, the task of finding an appropriate server from a set of replicas is a critical issue. We. have proposed in a previous work an architecture where a broker is used to provide server selection on a per session basis. When the-number of servers and/or the number of clients becomes large, a single broker may not have sufficient capacity to handle the load. An extended architecture based on the replication of brokers is therefore considered. We first discuss alternative organizations that support access to multiple brokers and the needed cooperation between brokers in order to achieve server selection effectively. We then propose a server selection policy for our multiple broker architecture and evaluate its performance by simulation.
In a distributed Database System (DDBS), transactions on objects can be read requests or write requests in a random manner The replication algorithm of objects critically affects the system performance. In this paper ...
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This paper investigates the placement of a finite set of web cache proxies in a computer network with a planar graph topology, based on a dynamic programming approach. Three criteria are defined for the web proxy plac...
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ISBN:
(纸本)0769519210
This paper investigates the placement of a finite set of web cache proxies in a computer network with a planar graph topology, based on a dynamic programming approach. Three criteria are defined for the web proxy placement: 1) the min-sum strategy with consolidated request forwarding (MS-CRF);2) the min-sum criterion with immediate request forwarding (MS-IRF);and 3) the min-max with immediate request forwarding (MM-IRF). Optimal placement is obtained under MS-CRF Under the MS-IRF and MM-IRF, a near optimal placement is achieved. This can be improved through a refinement strategy. The paper deals with the cylindrical mesh topology as a general topology on which any planar graph can be embedded.
To obtain good performance in messaging over mobile networks, we have developed a Gateway. Gateway is a message hub that transmits information using store-and-forward messaging and provides powerful optimization and d...
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ISBN:
(纸本)0769519210
To obtain good performance in messaging over mobile networks, we have developed a Gateway. Gateway is a message hub that transmits information using store-and-forward messaging and provides powerful optimization and data transformation. The SmartCaching component provides generic caching in an N-tier architecture, an essential function of Gateway. Gateway can be integrated into Pronto, a middleware system for mobile applications with messaging as a basis [15]. Pronto then offers: 1) a lightweight client of Message Oriented Middleware (MOM) based on Java Message Service(JMS), 2) Gateway for reliable and efficient transmission between mobile devices and a server and 3) Serverless JMS based on IP multicast. Integration of Gateway within Pronto provides a solution for mobile application-specific problems such as resource constraints, network characteristics, and data optimization.
This paper focuses on the development of miniaturised modular wireless sensor networks that can be used to realise distributed autonomous sensors for future ad-hoc networks. Such modular, mobile networks are key enabl...
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ISBN:
(纸本)0780379915
This paper focuses on the development of miniaturised modular wireless sensor networks that can be used to realise distributed autonomous sensors for future ad-hoc networks. Such modular, mobile networks are key enabling technologies in the field of ubiquitous computing and wearable electronics. The Ambient systems team in the NMRC has adopted a phased approach to developing ultra-miniature sensor nodes with a goal of implementation of a linin 3 (or less) autonomous sensor module. This paper will detail the progress through phases 1 and 2. The phase 1 modules are 25mm cubes, fabricated as a 3-D stackable modular PCB, which can be mounted on mobile devices or worn on the body;they can measure acceleration, rotation, shock, elevation etc. and have an ultra low-power RF channel-shared link to a base station. There are numerous possible applications in the fields of sports, exercise, entertainment and health. Extra panels, including sensory, memory or computation can be designed and added as needed. This make the phase 1 module a powerful test platform for developing future automous sensorsystems. The phase 2 modules have a much reduced form factor, approximately a 1cm cube;as well as the modularity developed in phase 1, the phase 2 form contains actuators and a PLD platform.
Corporate IT as well as individuals show increasing interest in reliable outsourcing of storage infrastructure. Decentralized solutions with their resilience against partial outages are among the most attractive appro...
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ISBN:
(纸本)0769520235
Corporate IT as well as individuals show increasing interest in reliable outsourcing of storage infrastructure. Decentralized solutions with their resilience against partial outages are among the most attractive approaches. Irrespective of the form of the relationship, be it based on a contract or on the more flexible cooperative model, the problem of verifying whether someone promising to store one's data actually does so remains to be solved, especially in the presence of multiple replicas. In this paper, we introduce a lightweight mechanism that allows the data originator or a dedicated verification agent to build up trust in the replica holder by means of protocols that do not require prior trust or key establishment. We show how naive versions of the protocol do not prevent cheating, and then strengthen it by adding means that make it economically attractive to be honest. This provides a foundation for further work in providing trustworthy distributed storage.
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