移动P2P网络中能量有效连续查询研究

在移动P2P网络中一个基本应用问题是访问分布式空间数据库中的数据对象,同时节省电量.文中提出了在移动P2P网络中能量有效连续查询处理（Energy Efficient Continuous Query Processing,EECQP）算法,包括范围查询和k个最近邻居节点查询（k-nearest-neighbor queries, k-NN）.EECQP算法能够提供移动用户找到一个有质量保证的连续查询结果.EECQP算法主要的想法是允许用户与节点合作,持续保存查询结果,而不是总是从头开始处理查询,从而减少通信开销.实验结果表明所提出的EECQP算法对于范围查询和k个最近邻居节点查询在通信开销和QoS保证是能量有效和可扩展的.     

Real-time processing of range-monitoring queries in heterogeneous mobile databases

Unlike conventional range queries, a range-monitoring query is a continuous query. It requires retrieving mobile objects inside a user-defined region and providing continuous updates as the objects move into and out of the region. In this paper, we present an efficient technique for real-time processing of such queries. In our approach, each mobile object is associated with a resident domain, and when an object moves, it monitors its spatial relationship with its resident domain and the monitoring areas inside it. An object reports its location to the server when it crosses over some query boundary or moves out of its resident domain. In the first case, the server updates the affected query results accordingly, while in the second case, the server determines a new resident domain for the object. This distributive approach achieves an accurate and real-time monitoring effect with minimal mobile communication and server processing costs. Our approach also allows a mobile object to negotiate a resident domain based on its computing capability. By having a larger resident domain, a more capable object has less of a chance of moving out of it and having to request a new one. As a result, both communication and server processing costs are reduced. Our comprehensive performance study shows that the proposed technique can be highly scalable in supporting location-based services in a wireless environment that consists of a large number of mobile devices.     

Trajectory identification based on spatio-temporal proximity patterns between mobile phones

Growing popularity of location-dependent mobile applications is continuously stimulating a demand for localization technology. However, in spite of significant research effort in the past decade, precise positioning in indoor environments is still an open problem. In this paper, we propose a novel type of indoor localization system that provides mobile phone users in a pedestrian crowd with their own position information of sub-meter accuracy by effectively utilizing a powerful pedestrian tracking capability of laser range scanners (i.e., laser-based distance measurement sensors). Although the laser-based tracking system can precisely detect presence of pedestrians at each location in its sensing region, the location information is not associated with any mobile phone users and thus it basically cannot provide the users’ own locations. To remove this limitation, we focus on spatio-temporal proximity patterns between mobile phones, which can be detected by peer-to-peer short-range wireless communication (e.g., Bluetooth). By examining consistency between the communication logs and proximity between anonymous trajectories detected by laser-based tracking, our system identifies a trajectory that corresponds to each mobile phone user to offer their own position information. Through extensive simulations and field experiments, we show that our system can achieve trajectory identification accuracy of up to 91 %.     

Moving Query Monitoring in Spatial Network Environments

Moving queries over mobile objects are an important type of query in moving object database systems. In recent years, there have been quite a few works in this area. Due to the high frequency in location updates and the expensive cost of continuous query processing, server computation capacity and wireless communication bandwidth are the two limiting factors for large-scale deployment of moving object database systems. Many techniques have been proposed to address the server bottleneck including one using distributed servers. To address both scalability factors, distributed query processing techniques have been considered. These schemes enable moving objects to participate in query processing to substantially reduce the demand on server computation, and wireless communications associated with location updates. Most of these techniques, however, assume an open-space environment. Since Euclidean distance is different from network distance, techniques designed specifically for an open space cannot be easily adapted for a spatial network. In this paper, we present a distributed framework which can answer moving query over moving objects in a spatial network. To illustrate the effectiveness of the proposed framework, we study two representative moving queries, namely, moving range queries and moving k-nearest-neighbor queries. Detailed algorithms and communication mechanisms are presented. The simulation studies indicate that the proposed technique can significantly reduce server workload and wireless communication cost.     

Spatial Queries in Wireless Broadcast Systems

Owing to the advent of wireless networking and personal digital devices, information systems in the era of mobile computing are expected to be able to handle a tremendous amount of traffic and service requests from the users. Wireless data broadcast, thanks to its high scalability, is particularly suitable for meeting such a challenge. Indexing techniques have been developed for wireless data broadcast systems in order to conserve the scarce power resources in mobile clients. However, most of the previous studies do not take into account the impact of location information of users. In this paper, we address the issues of supporting spatial queries (including window queries and kNN queries) of location-dependent information via wireless data broadcast. A linear index structure based on the Hilbert curve and corresponding search algorithms are proposed to answer spatial queries on air. Experiments are conducted to evaluate the performance of the proposed indexing technique. Results show that the proposed index and its enhancement outperform existing algorithms significantly.     

Novel service protocol for supporting remote and mobile users in wireless sensor networks with multiple static sinks

A wireless sensor network typically consists of users, a sink, and a number of sensor nodes. The users may be remotely connected to a wireless sensor network and via legacy networks such as Internet or Satellite the remote users obtain data collected by the sink that is statically located at a border of the wireless sensor network. However, in practical sensor network applications, there might be two types of users: the traditional remote users and mobile users such as firefighters and soldiers. The mobile users may move around sensor fields and they communicate with the static sink only via the wireless sensor networks in order to obtain data like location information of victims in disaster areas. For supporting the mobile users, existing studies consider temporary structures. However, the temporary structures are constructed per each mobile user or each source nodes so that it causes large energy consumption of sensor nodes. Moreover, since some of them establish the source-based structure, sinks in them cannot gather collective information like mean temperature and object detection. In this paper, to effectively support both the remote users and the mobile users, we propose a novel service protocol relying on the typical wireless sensor network. In the protocol, multiple static sinks connect with legacy networks and divide a sensor field into the number of the multiple sinks. Through sharing queries and data via the legacy networks, the multiple static sinks provide high throughput through distributed data gathering and low latency through short-hops data delivery. Multiple static sinks deliver the aggregated data to the remote users via the legacy networks. In case of the mobile users, when a mobile user moves around, it receives the aggregated data from the nearest static sink. Simulation results show that the proposed protocol is more efficient in terms of energy consumption, data delivery ratio, and delay than the existing protocols.     

Continuous Monitoring of Spatial Queries in Wireless Broadcast Environments

Wireless data broadcast is a promising technique for information dissemination that leverages the computational capabilities of the mobile devices in order to enhance the scalability of the system. Under this environment, the data are continuously broadcast by the server, interleaved with some indexing information for query processing. Clients may then tune in the broadcast channel and process their queries locally without contacting the server. Previous work on spatial query processing for wireless broadcast systems has only considered snapshot queries over static data. In this paper, we propose an air indexing framework that 1) outperforms the existing (i.e., snapshot) techniques in terms of energy consumption while achieving low access latency and 2) constitutes the first method supporting efficient processing of continuous spatial queries over moving objects.     

Building reusable mobile agents for network management

Mobile agents can migrate among nodes to perform a set of management tasks at each of the visited nodes. Existing mobile agent-based network management systems often assume that their mobile agents are designed to work in particular networks to raise the efficiency of agent migration among multiple nodes. Unfortunately, such mobile agents cannot be reused in different networks. This paper proposes a framework where a mobile agent for network management is composed of two kinds of software components, an itinerary part and a behavioral logic part. Both components are implemented as mobile agents. The former is a carrier designed for particular networks, and it can efficiently navigate other mobile agents among nodes in its target network. The latter defines management tasks performed at each node independently of any local network. This framework allows a mobile agent for network management to be reused in various networks without being modified. A prototype implementation of this framework and its application were built on a Java-based mobile agent system.     

Policy-driven personalized multimedia services for mobile users

This paper proposes an agent-based service provisioning system for mobile users. It describes a set of cooperative agents distributed over different sites that work together to provide personalized services for mobile users over the Internet. Users moving outside the office are able to maintain an off ice-like environment at home, or at temporary locations such as a meeting at another company, a business trip, or a hotel. Agents representing the end-users and the system agents engage in a negotiation process to facilitate access to personalized services at other sites. This access is obtained in accordance with the users' home policies as well as those at their current location. An Adaptive Service Presentation agent is used to adapt the service presentation to the capabilities of the users' workstations, laptops, phones, PDAs, or other devices. This work is conducted in Canada as part of the Mobile Agent Alliance project involving the University of Ottawa, the National Research Council, and the Mitel Corporation.     

Anonymous and expeditious mobile user authentication scheme for GLOMONET environments

The Global Mobility Network (GLOMONET) is rapidly becoming important as well as a popular feature in today's high‐performance network. The legal mobile users enjoy life using the ubiquitous services via GLOMONET. However, because of the broadcast nature of the wireless channel, providing user authentication along with the privacy and anonymity of the users in GLOMONET is indeed a challenging task. In this article, we come up with a secure and expeditious mobile communication environment using symmetric key cryptosystem to ensure mobile users' anonymity and privacy against eavesdroppers and backward/forward secrecy of the session key. Our scheme can also protect numerous security threats, like man‐in‐the‐middle attack, known session key attack, lost smartcard attack, and forgery attack. Furthermore, we put forward a new technique named as “friendly foreign agent policy,” where many foreign agents can make different groups among themselves and perform important responsibilities to authenticate a legitimate mobile user without interfering his or her home agent even though the mobile user moves to a new location, covered by a new foreign agent (belongs to the same group). Security and performance analyses show that the proposed scheme is secure and more efficient as compared with other competitive schemes for GLOMONET environments.     

HotTown, enabling context-aware and extensible mobile interactive spaces

This article introduces a novel, open, and scalable service architecture for context-aware personal communication. In contrast to the network-centric open service access in third-generation mobile networks, this architecture moves the point of integration for user services out to the mobile devices, where we can create support for context-aware computing and communication. Support for peer-to-peer service negotiation with minimal a priori shared knowledge, context representation, and reasoning about context enables the mobile agents (that represent users and other entities) to be aware of and react to any event and thus context. Hence, the delivery of context-aware applications to users intertwining digital and physical objects in mobile interactive spaces leverages events from sensors, mobility support, and digital entities. Finally, a presentation of our prototype and experiences from the HotTown project demonstrates the feasibility of the approach and provides some examples of the enabled user communication for large-scale mobile networks.     

Location-Based Spatial Query Processing with Data Sharing in Wireless Broadcast Environments

Location-based spatial queries (LBSQs) refer to spatial queries whose answers rely on the location of the inquirer. Efficient processing of LBSQs is of critical importance with the ever-increasing deployment and use of mobile technologies. We show that LBSQs have certain unique characteristics that traditional spatial query processing in centralized databases does not address. For example, a significant challenge is presented by wireless broadcasting environments, which have excellent scalability but often exhibit high-latency database access. In this paper, we present a novel query processing technique that, while maintaining high scalability and accuracy, manages to reduce the latency considerably in answering location-based spatial queries. Our approach is based on peer-topeer sharing, which enables us to process queries without delay at a mobile host by using query results cached in its neighboring mobile peers. We demonstrate the feasibility of our approach through a probabilistic analysis, and we illustrate the appeal of our technique through extensive simulation results.     

Protocol architecture for universal personal computing

This paper presents a new paradigm for network computing over the Internet called universal personal computing, where mobile users can access computing resources, network services, and personalized computing environments anywhere using any available terminals. The user and system requirements are defined, and an agent-based protocol architecture required to manage different mobile objects, i.e., users and terminals, in this computing environment is presented. Modifications of connection setup procedures between user application programs to enable addressing based on a global user identity are considered. The use of personal agents to facilitate interworking and management functions is proposed     

A mobile virtual-distributed system architecture for supporting wireless mobile computing and communications

This paper describes a novel mobile virtual-distrubuted system architecture for supporting global mobile computing and communications. the principal contribution of this paper is to innovatively apply virtual memory concepts to mobile systems by deploying mobile-floating agents to de-couple services and resources from the underlying network and allow them to move around following their mobile users. The mobile-floating agents maintain data structures associated with a mobile user. By combining the mobile-floating agent functions with a predictive mobility management algorithm and location-aware caching and prefetching, services and user data structure are pre-connected and pre-assigned at the locations to which the user is moving. Thus, the users can maintain their data structures or immediately receive service with virtually the same efficiency as at the previous location.     

X‐Region: A framework for location privacy preservation in mobile peer‐to‐peer networks

While enjoying various LBS (location‐based services), users also face the threats of location privacy disclosure. This is because even if the communications between users and LBS providers can be encrypted and anonymized, the sensitive information inside LBS queries may disclose the exact location or even the identity of a user. The existing research on location privacy preservation in mobile peer‐to‐peer (P2P) networks assumed that users trust each other and directly share location information with each other. Nonetheless, this assumption is not practical for most of the mobile P2P scenarios, for example, an adversary can pretend to be a normal user and collect the locations of other users. Aiming at this issue, this paper presents x‐region as a solution to preserve the location privacy in a mobile P2P environment where no trust relationships are assumed amongst mobile users. The main idea is to allow users to share a blurred region known as x‐region instead of their exact locations so that one cannot distinguish any user from others inside the region. We propose a theoretical metric for measuring the anonymity property of x‐region, together with three algorithms for generating an x‐region, namely, benchmark algorithm, weighted expanding algorithm, and aggressive weighted expanding algorithm. These algorithms achieve the anonymity and QoS requirements with different strategies. Our experiments verify the performance of the algorithms against three key metrics. Copyright © 2013 John Wiley & Sons, Ltd.     

Non-Line-of-Sight Localization in Multipath Environments

Location-based spatial queries (LBSQs) refer to spatial queries whose answers rely on the location of the inquirer. Efficient processing of LBSQs is of critical importance with the ever-increasing deployment and use of mobile technologies. We show that LBSQs have certain unique characteristics that the traditional spatial query processing in centralized databases does not address. For example, a significant challenge is presented by wireless broadcasting environments, which have excellent scalability but often exhibit high-latency database access. In this paper, we present a novel query processing technique that, though maintaining high scalability and accuracy, manages to reduce the latency considerably in answering LBSQs. Our approach is based on peer-to-peer sharing, which enables us to process queries without delay at a mobile host by using query results cached in its neighboring mobile peers. We demonstrate the feasibility of our approach through a probabilistic analysis, and we illustrate the appeal of our technique through extensive simulation results.     

Spatial query processing in road networks for wireless data broadcast

Recently, wireless broadcast environments have attracted significant attention due to its high scalability to broadcast information to a large number of mobile subscribers. It is especially a promising and desirable dissemination method for the heavily loaded environment where a great number of the same type of requests are sent from the users. There have been many studies on processing spatial queries via broadcast model recently. However, not much attention is paid to the spatial queries in road networks on wireless broadcast environments. In this paper, we focus on three common types of spatial queries, namely, k nearest neighbor (kNN) queries, range queries and reverse nearest neighbor (RNN) queries in spatial networks for wireless data broadcast. Specially, we propose a novel index for spatial queries in wireless broadcast environments (ISW). With the reasonable organization and the effectively pre-computed bounds, ISW provides a powerful framework for spatial queries. Furthermore, efficient algorithms are designed to cope with kNN, range and RNN queries separately based on ISW. The search space can be obviously reduced and subsequently the client can download as less as possible data for query processing, which can conserve the energy while not significantly influence the efficiency. The detailed theory analysis of cost model and the experimental results are presented for verifying the efficiency and effectiveness of ISW and our methods.     

Trajectory recommendation for task accomplishment in crowdsourcing – a model to favour different actors

Crowdsourcing systems (CS) are platforms that enable users, called requesters, to publish tasks that others, called workers, are expected to accomplish. Usually, these are systems where workers perform tasks using desktop computers. Recently, some CS have appeared with location-based tasks that require a worker to be at a given location within a given time window to be accomplished. In this paper, we study the problem of matching these location-based tasks and mobile workers under a novel perspective where three actors (workers, requesters and the system itself) of the CS may benefit differently from a configuration of tasks and workers. We introduce the Trajectory Recommendation Problem (TRP) where a CS finds a trajectory (sequence of tasks) for a single mobile worker that maximises the satisfaction of one or more of the actors. We show that TRP is NP-complete and then propose an exact algorithm for solving it. Our experiments have proved that our algorithm is a feasible solution when up to a few hundred tasks must be analysed to find an optimal solution. Finally, we propose an architecture for the deployment of the recommendation in a CS.