Analysing Internet Software Retrieval Systems: Modeling and Performance Comparison

Nowadays, there exist web sites that allow users to retrieve and install software in an easy way. The performance of these sites may be poor if they are used in wireless networks; the reason is the inadequate use of the net resources that they need. If these kinds of systems are designed using mobile agent technology the previous problem might be avoided. In this paper, we present a comparison between the performance of a software retrieval system especially designed to be used in a wireless network and the performance of a software retrieval system similar to the well-known Tucows.com web site. In order to compare performance, we make use of a software performance process enriched with formal techniques. The process has as important features that it uses UML as a design notation and it uses stochastic Petri nets as formal model. Petri nets provide a formal semantics for the system and a performance model.     

Location-dependent queries in mobile contexts: distributed processing using mobile agents

With the current advances of mobile computing technology, we are witnessing an explosion in the development of applications that provide mobile users with a wide range of services. In this paper, we present a system that supports distributed processing of continuous location-dependent queries in mobile environments. The system that we propose presents the following main advantages: 1) it is a general solution for the processing of location-dependent queries in scenarios where not only the users issuing queries, but also other interesting objects can move; 2) it performs an efficient processing of these queries in a continuous way; 3) it is especially well adapted to environments where location data are distributed in a network and processing tasks can be performed in parallel, allowing a high scalability; and 4) it optimizes wireless communications. We use mobile agents to carry the processing tasks wherever they are needed. Thus, agents are in charge of tracking the location of interesting moving objects and refreshing the answer to a query efficiently. We evaluate the usefulness of the presented proposal showing that the system achieves a good precision and scales up well.     

Integrating context-aware public displays into a mobile hospital information system

Hospitals are convenient settings for deployment of ubiquitous computing technology. Not only are they technology-rich environments, but their workers experience a high level of mobility resulting in information infrastructures with artifacts distributed throughout the premises. Hospital information systems (HISs) that provide access to electronic patient records are a step in the direction of providing accurate and timely information to hospital staff in support of adequate decision-making. This has motivated the introduction of mobile computing technology in hospitals based on designs which respond to their particular conditions and demands. Among those conditions is the fact that worker mobility does not exclude the need for having shared information artifacts particular locations. In this paper, we extend a handheld-based mobile HIS with ubiquitous computing technology and describe how public displays are integrated with handheld and the services offered by these devices. Public displays become aware of the presence of physicians and nurses in their vicinity and adapt to provide users with personalized, relevant information. An agent-based architecture allows the integration of proactive components that offer information relevant to the case at hand, either from medical guidelines or previous similar cases.     

区域性中轨道卫星移动通信系统“时间决定”星座设计

区域性卫星移动通信系统对于发展中国家具有十分重要的意义,特别是对于中国这样幅员辽阔且在广大农村地区缺乏基本通信手段的国家.采用中轨星座是解决这一问题的有效途径.本文提出了一种用于区域性系统的中轨星座设计方法:"时间决定"星座设计.该星座可为特定地区提供性能优越的服务,它提供的服务可以是时限的,也可以是非时限的.利用这种设计方法可以为中国设计经济的卫星移动通信系统星座方案,同时这些星座方案也可为美国大陆提供优越的服务.     

Improving Delay and Jitter Performance in Wireless Mesh Networks for Mobile IPTV Services

Wireless mesh networking has recently emerged as a promising technology for the next-generation wireless networks. In wireless mesh networks (WMNs), it is practically attractive to support the low-cost quality-of-service (QoS) guaranteed mobile TV service. To meet this need, our study addresses how to improve the delay and jitter performance of mobile IPTV services over IEEE 802.11 based WMN. Particularly, we first discuss the adaptation of IEEE 802.11 MAC layer to construct a WMN with emphasis on mobile IPTV service; we then develop an enhanced version of Guaranteed-Rate (GR) packet scheduling algorithm, namely virtual reserved rate GR (VRR-GR), to further reduce the delay and suppress the jitter in multiservice network environment. Simulation results show that our proposed approach can satisfyingly prioritize mobile IPTV services in WMN, while providing non-IPTV services with what they need as well.      

A Load-Balancing and Push-Out Scheme for Supporting QoS in MANETs

Currently, mobile ad hoc networks (MANETs) lack load-balancing capabilities, and thus, they fail to provide good performance especially in the case of a large volume of traffic. Ad hoc networks lack also service differentiation. However, in these wireless environments, where channel conditions are variable and bandwidth is scarce, the differentiated services developed for the Internet are suboptimal without lower layers' support. The IEEE 802.11 standard for Wireless LANs is the most widely used WLAN standard today. It has a mode of operation that can be used to provide service differentiation, but it has been shown to perform badly. In this paper, we present a simple but very effective method for support Quality of Service, by the use of load-balancing and push-out scheme. This approach offers to the mobile node: the ability to alleviate congestion by traffic distribution of excessive load, and to support priority of packets in the single MAC buffer. We evaluate the performance of our algorithm and compare it with the original IEEE 802.11b protocol. Simulation results show that this new approach reduces packet loss rate and increases throughput as well as provides service differentiation in the MAC layer.     

EIM: An Enforceable Incentive Mechanism for Dynamic Non-cooperative Multi-radio Channel Allocation in Wireless Mobile Networks

Multi-radio channel allocation (MRCA) is a key issue to improve the system performance supporting all kinds of mobile applications in wireless networks. However, existed work on non-cooperative MRCA just considers the cases under the extreme saturation load condition and static game, which means that it is assumed that all the nodes always have packets to send and mobile terminals just change the channel once. Such assumption is obviously impractical for actual wireless network and isn’t suitable for the mobility of applications without intelligent spectrum management. Meanwhile, the existed schemes are unable to support mobile applications with time-varying channel. In this paper, an enforceable incentive mechanism called EIM is proposed for dynamic non-cooperative multi-radio channel allocation to support mobile applications. In order to optimize the overall performance of mobility management, in the proposed EIM, the strong assumption of saturation network traffic is relaxed, which makes the mobile terminals are able to have time-varying bandwidth requirements. Then, the MRCA problem is modeled as an infinite repeated game. Detailed theoretical analysis proves that there exist multiple pure Nash Equilibriums (NEs) for the game, and, under certain condition, there also exist NEs which are not Pareto-Optimal. Hence, based on the punishment strategy, the proposed EIM can achieve social welfare. Detailed numerical and simulation results show that the proposed EIM can improve the system throughput about 15 % compared with the existed works, which can provide an efficient method to manage channel resource and get better ubiquitous online access to preferred mobile services.     

Seamless integration of mobile WiMAX in 3GPP networks

As the wireless industry makes its way to the next generation of mobile systems, it is important to engineer solutions that enable seamless integration of emerging 4G access technologies within the currently deployed and/or evolved 2G/3G infrastructures. In this article we address a specific case of such a seamless integration, that of mobile WiMAX in evolved 3GPP networks. In this context we investigate the architecture and the key procedures that enable this integration, and we also introduce a novel handover mechanism that enables seamless mobility between mobile WiMAX and legacy 3GPP access, such as UTRAN or GERAN. The core characteristic of this novel handover mechanism is that mobile terminals do not need to support simultaneous transmission on both WiMAX and 3GPP accesses; therefore, it mitigates the RF coexistence issues that exist otherwise and improves handover performance. In addition, we provide a brief overview of mobile WiMAX and the evolved 3GPP network technologies, and we set the appropriate background material before presenting our proposed handover mechanism. Our main conclusion is that integrating mobile WiMAX in evolved 3GPP networks is a compelling approach for providing wireless broadband services, and mobility across WiMAX and 3GPP access can become seamless and efficient with no need for mobile terminals to support simultaneous transmission on both types of access.     

Modeling a Mobile Cellular Network Using a Discrete-Event Simulator

In this paper we introduce a discrete-event-based simulation technology suitable to model cellular mobile radio systems with respect to their dynamic behavior. The latter results in the need for simulation tools which support mutable system configurations. The problems encountered when modeling mutable system configurations using conventional discrete-event simulators are discussed. In order to show a possible solution to this problem we introduce configuration events and configuration objects into the theory of discrete-event simulations. We demonstrate how configuration objects can be implemented in a discrete-event simulator using a dynamic map-function, hereby extending a definition of higher order functions. We apply the configuration objects in a Multiple Layer Model for modeling an entire mobile cellular radio network in a discrete-event simulator as an application for the extended theory. In this model we use the configuration objects to change the network's configuration during runtime. We show that this solution—combined with an object-oriented software design and, possibly, a visual programming language—is a powerful tool for the simulation of the dynamic aspects of mobile cellular radio networks. The software technology presented will be applied by the German cellular network operator Mannesmann Mobilfunk to model dynamic features applicable to the radio resource management of mobile radio networks and to access their performance by simulation.     

基于多Agent的移动信息服务支持系统

随着我国移动通信的迅猛发展 ,用户对于移动增值业务的需求越来越高。如何建立一个高效的移动增值业务服务支持系统 ,并保证移动增值业务的服务品质 ,是一个急需研究和解决的重要课题。本文针对这一问题 ,从系统体系结构的角度提出了一种多 Agent移动信息服务支持系统。该系统提供了可以高效地配置与管理信息类移动增值业务的系统解决方案 ,尤其适用于主动式高级信息服务类增值业务。这一系统结构适应性强、易扩展、易维护 ,并能够更好地支持对用户的个性化服务。该系统具有广泛的应用前景 ,对于未来 3G的增值业务具有一定的参考价值     

Improving UDP and TCP performance in mobile ad hoc networks withINSIGNIA

There is a growing need to provide better service differentiation in mobile ad hoc networks; however, this is challenging. These networks are characterized as being multihop in nature where the wireless topology that interconnects mobile hosts/routers can change rapidly in unpredictable ways or remain relatively static over long periods of time. Power and bandwidth constrained, mobile ad hoc networks typically only support best effort communications where the transport protocol's “goodput” is often lower than the maximum radio transmission rate after encountering the effects of multiple access, fading, noise, and interference. We evaluate three routing protocols with INSIGNIA, an in-band signaling system that supports adaptive reservation-based services in mobile ad hoc networks. INSIGNIA represents a general-purpose approach to delivering quality of service in mobile ad hoc network supporting “operational transparency” between a number of IETF mobile ad hoc network routing protocols that include Ad Hoc On-Demand Distance Vector, Dynamic Source Routing, and the Temporally Ordered Routing Algorithm. We evaluate the performance gains delivered when using INSIGNIA with these MANET routing protocols in support of UDP and TCP traffic. The INSIGNIA ns-2 code used for the study reported in this article is available from the Web at comet.columbia.edu/insignia     

基于移动设备加密系统的设计与实现

为保障信息安全,政府部门和企业都建立了信息安全系统,对重要电子文档加密。然而,员工外出办公时,无法随时随地都携带着自己的电脑,有时必须使用他人或公共的电脑进行办公,在这种情况下无法保证机密文件的安全。文中提出了一种移动设备加密系统,将加解密功能固化到移动设备上,并由认证模式对本身的功能进行保护。密文文件可存储在移动设备上带出或通过互联网传输,而不用担心泄密风险。当到异地时,任何一台电脑都可以通过与移动设备的连接而进行对密文文件的使用,以此来保障信息的安全。     

Admission control in time-slotted multihop mobile networks

The emergence of nomadic applications have generated a lot of interest in next-generation wireless network infrastructures which provide differentiated service classes. So it is important to study how the quality of service (QoS), such as packet loss and bandwidth, should be guaranteed. To accomplish this, we develop am admission control scheme which can guarantee bandwidth for real-time applications in multihop mobile networks. In our scheme, a host need not discover and maintain any information of the network resources status on the routes to another host until a connection request is generated for the communication between the two hosts, unless the former host is offering its services as an intermediate forwarding station to maintain connectivity between two other hosts. This bandwidth guarantee feature is important for a mobile network to interconnect wired networks with QoS support. Our connection admission control scheme can also work in a stand-alone mobile ad hoc network for real-time applications. This control scheme contains end-to-end bandwidth calculation and bandwidth allocation. Under such a scheme, the source is informed of the bandwidth and QoS available to any destination in the mobile network. This knowledge enables the establishment of QoS connections within the mobile network and the efficient support of real time applications. In the case of ATM interconnection, the bandwidth information can be used to carry out an intelligent handoff between ATM gateways and/or to extend the ATM virtual circuit service to the mobile network with possible renegotiation of QoS parameters at the gateway. We examine via simulation the system performance in various QoS traffic flows and mobility environments     

An integrated communications framework for context aware continuous monitoring with body sensor networks

This paper deals with a wireless pervasive communication system to support advanced healthcare applications. The proposed system is based on an ad hoc interaction of mobile body sensor networks with independent wireless sensor networks already deployed within the environments in order to allow a continuous and context aware health monitoring for patients along their daily life scenarios with an unprecedented precision and flexibility of sensing. After an accurate protocol characterization, simulation results are provided, underlining remarkable performance with respect to existing solutions, for different mobility models and node density values.     

Architecture and experimental results for quality of service in mobile networks using RSVP and CBQ

Efforts are underway to enhance the Internet with Quality of Service (QoS) capabilities for transporting real‐time data. The issue of wireless networks and mobile hosts being able to support applications that require QoS has become very significant. The ReSerVation Protocol (RSVP) provides a signaling mechanism for end‐to‐end QoS negotiation. RSVP has been designed to work with wired networks. To make RSVP suitable for wireless networks, changes need to be made by: (i) changing the way control messages are sent, and (ii) introducing wireless/mobile specific QoS parameters that take into account the major features of wireless networks, namely, high losses, low bandwidth, power constraints and mobility. In this paper, an architecture with a modified RSVP protocol that helps to provide QoS support for mobile hosts is presented. The modified RSVP protocol has been implemented in an experimental wireless and mobile testbed to study the feasibility and performance of our approach. Class Based Queueing (CBQ) which is used as the underlying bandwidth enforcing mechanism is also modified to fit our approach. The experimental results show that the modified RSVP and CBQ help in satisfying resource requests for mobile hosts, after handoff occurs. The experiments also show how different power and loss profile mechanisms can be used with our framework. The system performance using the modified RSVP control mechanism is also studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cell hopping: a lightweight architecture for wireless communications

We propose a novel lightweight cellular wireless network architecture called cell hopping. Unlike traditional cellular networks, cell hopping has base stations interconnected by wireless inter-base station links, WIBLs. WIBLs support all routing and switching in cell hopping networks, obviating the need for costly core networks (or a costly switching infrastructure). Cell hopping utilizes an unlicensed frequency and presents a low-cost, rapidly deployable solution for mobile communications. We discuss various technical challenges that must be addressed before cell hopping can become a reality. In particular, we concentrate on location management. We propose an on-demand location management technique that completely eliminates the need for location databases and periodic updates by mobile stations. We provide a few variations of the location management scheme, and compare their performance through simulation.     

Design and Experimental Evaluation of a Route Optimization Solution for NEMO

An important requirement for Internet protocol (IP) networks to achieve the aim of ubiquitous connectivity is network mobility (NEMO). With NEMO support we can provide Internet access from mobile platforms, such as public transportation vehicles, to normal nodes that do not need to implement any special mobility protocol. The NEMO basic support protocol has been proposed in the IETF as a first solution to this problem, but this solution has severe performance limitations. This paper presents MIRON: Mobile IPv6 route optimization for NEMO, an approach to the problem of NEMO support that overcomes the limitations of the basic solution by combining two different modes of operation: a Proxy-MR and an address delegation with built-in routing mechanisms. This paper describes the design and rationale of the solution, with an experimental validation and performance evaluation based on an implementation.     

Hierarchical mobile network binding scheme for route optimization in NEMO

Recently, there has been a great deal of research on network mobility management that can support the movement of a mobile network consisting of several mobile nodes. The IETF NEMO working group proposed a basic support protocol, which defines methodology for supporting network mobility by using bi-directional tunneling between the home agent and the mobile router. This protocol, however, suffers from the ‘pinball routing problem,’ and most of the research attempts to solve this problem still have limitations in the efficiency of intra-domain communication. Moreover, these methods require additional binding procedures in case of the root mobile router handover. In this paper, we propose new route optimization methodology that can remedy these limitations by using asymmetric tunneling and a hierarchical local binding mechanism, which can provide faster signaling and data transmission. It can also be easily extended to support micro-mobility without the need for additional extensions. The performance is evaluated by simulation which can show the efficiency of the approach, compared with several previous route optimization methods.     

A mobile care system with alert mechanism.

Hypertension and arrhythmia are chronic diseases, which can be effectively prevented and controlled only if the physiological parameters of the patient are constantly monitored, along with the full support of the health education and professional medical care. In this paper, a role-based intelligent mobile care system with alert mechanism in chronic care environment is proposed and implemented. The roles in our system include patients, physicians, nurses, and healthcare providers. Each of the roles represents a person that uses a mobile device such as a mobile phone to communicate with the server setup in the care center such that he or she can go around without restrictions. For commercial mobile phones with Bluetooth communication capability attached to chronic patients, we have developed physiological signal recognition algorithms that were implemented and built-in in the mobile phone without affecting its original communication functions. It is thus possible to integrate several front-end mobile care devices with Bluetooth communication capability to extract patients' various physiological parameters [such as blood pressure, pulse, saturation of haemoglobin (SpO2), and electrocardiogram (ECG)], to monitor multiple physiological signals without space limit, and to upload important or abnormal physiological information to healthcare center for storage and analysis or transmit the information to physicians and healthcare providers for further processing. Thus, the physiological signal extraction devices only have to deal with signal extraction and wireless transmission. Since they do not have to do signal processing, their form factor can be further reduced to reach the goal of microminiaturization and power saving. An alert management mechanism has been included in back-end healthcare center to initiate various strategies for automatic emergency alerts after receiving emergency messages or after automatically recognizing emergency messages. Within the time intervals in system setting, according to the medical history of a specific patient, our prototype system can inform various healthcare providers in sequence to provide healthcare service with their reply to ensure the accuracy of alert information and the completeness of early warning notification to further improve the healthcare quality. In the end, with the testing results and performance evaluation of our implemented system prototype, we conclude that it is possible to set up a complete intelligent healt care chain with mobile monitoring and healthcare service via the assistance of our system.     

具有星际链路的LEO&MEO双层卫星网络路由策略研究

本文提出了一个具有星际链路的LEO&MEO(低轨和中轨 )双层卫星通信系统 ,详细介绍了系统结构、协议体系并重点研究了双层卫星系统的路由问题 .为了适应宽带多媒体通信的需要 ,系统采用了ATM快速分组交换技术 .提出了基于Dijkstra算法的双层卫星网络时延最短路由策略和时延抖动最小路由策略 ,并通过计算机仿真研究了它们的性能 ,得到了具有一定参考价值的结果 .