Skyline queries are well suited when retrieving data according to multiple criteria. While most previous work has assumed a centralized setting this paper considers skyline querying in a mobile and distributed setting, where each mobile device is capable of holding only a portion of the whole dataset; where devices communicate through mobile ad hoc networks; and where a query issued by a mobile user is interested only in the user’s local area, although a query generally involves data stored on many mobile devices due to the storage limitations. We present techniques that aim to reduce the costs of communication among mobile devices and reduce the execution time on each single mobile device. For the former, skyline query requests are forwarded among mobile devices in a deliberate way, such that the amount of data to be transferred is reduced. For the latter, specific optimization measures are proposed for resource-constrained mobile devices. We conduct extensive experiments to show that our proposal performs efficiently in real mobile devices and simulated wireless ad hoc networks. 1.

In order for precise evaluation of MANET applications, more realistic mobility models are needed in wireless network simulations. In this paper, we focus on the behavior of pedestrians in urban areas and propose a new method to generate a mobility scenario called Urban Pedestrian Flows (UPF). In the proposed method, we classify pedestrians in a simulation field into multiple groups by their similar behavior patterns (simply called flows hereafter, which indicate how they move around geographic points). Given the observed road density in the target field, we derive using linear programming techniques how many pedestrians per minute follow each flow. Using the derived flows, we generate a UPF scenario which can be used in network simulators. In particular, we have enhanced a network simulator called MobiREAL, which has been developed in our research group, so that we can generate and use the UPF scenario. MobiREAL simulator has three main facilities: the behavior simulator, network simulator and animator. The behavior simulator can generate/delete mobile nodes according to the UPF scenario. The network simulator can simulate MANET protocols and applications. The animator offers elegant visualization of simulation traces as well as graphical user interfaces for facilitating derivation of UPF scenarios. Through several case studies, we show similarity of the derived flows to the observed ones, as well as the metrics that characterize the mobility of the scenario.

Efficient integration of a multi-hop wireless network with the Internet is an important research problem, and benefits several applications, such as wireless neighborhood networks and sensor networks. In a wireless neighborhood network, a few Internet Transit Access Points (ITAPs), serving as gateways to the Internet, are deployed across the neighborhood; houses are equipped with low-cost antennas, and form a multi-hop wireless network among themselves to cooperatively route traffic to the Internet through the ITAPs. In a sensor network, sensors collect measurement data and send it through a multi-hop wireless network to the servers on the Internet via ITAPs. For both applications, placement of integration points between the wireless and wired network is a critical determinant of system performance and resource usage. However there has been little work on this subject. In this paper, we explore the placement problem under three wireless link models. For each link model, we develop algorithms to make informed placement decisions based on neighborhood layouts, user demands, and wireless link characteristics. We also extend our algorithms to provide fault tolerance and handle significant workload variation. We evaluate our placement algorithms using both analysis and simulation, and show that our algorithms yield close to optimal solutions over a wide range of scenarios we have considered. 1.

Abstract — Recovery of traffic in connectionless pure IP networks has traditionally been handled by a full re-convergence of the network state. This process operates in a time scale that is not compatible with new real time and highly dependable services. Recently, schemes for fast local and proactive recovery in connectionless IP networks have been proposed. All these schemes are designed to guarantee recovery of the failure of one component. As IP protocols are used to carry more highly dependable services and new wireless infrastructures are approaching, guaranteed failure coverage of more than one failure becomes necessary. In this paper we present and evaluate a scheme that guarantees to handle any two concurrent failures in a network. We are not aware of any other schemes that addresses such guarantees. We evaluate and compare it with other known recovery schemes, and we show how it gives substantially better recovery success rates

This paper is about energy efficient and robust implementation of random walks in mobile wireless networks. While random walk based algorithm are often proposed to solve many problems in wireless networks, their implementation is usually done at the application layer so that many characteristics of the wireless transmissions are not exploited. In this paper we show that we can greatly reduce the energy requirements to perform a walk by better exploiting the broadcast nature of the transmissions. We propose a robust, energy efficient distributed next hop selection algorithm. To evaluate the algorithm we present a simulation study performed with ns-2. We found that in the proposed algorithm energy is reduced to more than 4 times and the selection delay is reduced to more than 8 times as compared to a standard next hop selection implementation. 1

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Abstract—Wireless sensor networks are becoming increasingly popular for wireless monitoring and automation of buildings and industrial processes. Currently, many different protocols for sensor networks are proposed. However, there is very little research regarding a sensor network architecture in which to integrate them. To that end, we propose a universal, modular framework (UMF) for sensor networks. The proposed framework eases protocol integration, and has two key advantages over previous layered solutions. First, due to its modular composition, the proposed framework is highly optimized to support heterogeneous networks. Second, more advanced network functionality such as QoS is more easily supported. In this paper, we discuss several design constraints for building a modular network architecture for sensor networks and we explore several possibilities to take advantage of a modular architecture when designing network protocols. Index Terms—Sensor network, cross-layer, modular architecture, sensor network architecture. I.

The diffusion of pervasive, sensor-rich, network-interconnected devices embedded in the environment is

This paper aims to provide a detailed survey of existing graph models and algorithms for important problems that arise in di#erent areas of wireless telecommunication. In particular, applications of graph optimization problems such as minimum dominating set, minimum vertex coloring and maximum clique in multihop wireless networks are discussed.

Abstract. The low quality of wireless links leads to perpetual packet losses. While an acknowledgment mechanism is generally used to cope with these losses, multiple retransmissions nevertheless occur. Opportunistic routing limits these retransmissions by taking advantage of the broadcast nature of the wireless channel: sending packets to multiple receivers at once, and only then, based on the outcome, choosing the actual next hop [1]. In this paper, we first study the potentials of opportunistic routing in energy-constrained wireless sensor networks. In particular, the reduction of retransmissions due to the broadcast advantage is balanced with the arising need for coordination to avoid duplicate packets. We then propose Coordinated Anypath Routing, an opportunistic routing protocol designed for wireless sensor networks, in which the coordination between receivers is handled by an overhearing-based acknowledgment scheme. Our protocol may be used to minimize either retransmissions or power consumption, and our simulation results show that, with lossy links, energy savings go up to 7%, even for small networks of 20 nodes. 1