Catálogo de publicaciones - libros

Wireless communication is inherently vulnerable to errors from the dynamic wireless environment. Link layer packets discarded due to these errors impose a serious limitation on the maximum achievable throughput in the wireless channel. To enhance the overall throughput of wireless communication, it is necessary to deploy link layer transmission schemes that is robust to the errors intrinsic to the wireless channel. In this paper, we investigated the impact of three link layer enhancement techniques on the new Enhanced Data Rate (EDR) mode detailed in the new Bluetooth spec v2.0. We first studied the APT algorithm, and used it to obtain the optimal packet type for different bit error rates. We then evaluated FEC/IFEC coding schemes for the new EDR packet types, assessed their ability to alleviate the impact of burst errors, and discussed the tradeoffs. Using analysis and simulation, we show that the performance of the new Bluetooth EDR mode can be significantly improved when FEC and/or IFEC techniques are employed.

A key issue in wireless sensor networks (WSNs) is to select a set of sensors to join sensing task under some physical resource constraints while achieving a required information accuracy. This paper introduces a novel idea for information-accuracy-aware jointly sensing nodes selection based on a derived information accuracy model which formulates an explicit relationship between information accuracy and the number and position of jointly sensing nodes. We aim at eliminating the unnecessary transmission to minimize energy consumption while maximizing information accuracy, which is formulated as a joint optimization of information accuracy and energy consumption. In the proposed algorithm, a node is selected to join a sensing task based on its information accuracy gain and consumed energy. This allows a WSN to efficiently distribute sensing tasks given a limited energy supply. Simulation results have demonstrated that our algorithm improves the performance of joint optimization between information accuracy and energy consumption than a random node selection.

A sensor network application requires diverse kernel supports to function properly. With its resource limits the sensor node cannot provide all the functionalities needed by many kinds of applications at the same time. The kernel’s functionality therefore requires runtime reconfigurability, which can be achieved via modularizing the kernel. This paper presents a framework that dynamically reconfigures the kernel’s functionality according to the needs of the application. In particular, the proposed mechanism handles the address resolution problem of a MMU-less processor. This framework has been implemented on a sensor network operating system, RETOS, which supports multi-threaded programming environments. It efficiently manages the modularized kernel’s resources and works in an optimized condition. By providing modularized kernel programming, RETOS optimizes itself with functionalities that various kinds of sensor network applications require.

The wireless sensor networks are sensing, computing and communication infrastructures that allow us to monitor, instrument, observe, and respond to phenomena in the harsh environment. Sensor operating systems that run on tiny sensor nodes are the key to the performance of the distributed computing environment for the wireless sensor networks. Therefore, sensor operating systems should be able to operate efficiently in terms of energy consumption and resource management. In this paper, we present to improve the time and space efficiency of memory management for the sensor operating systems. was implemented on which is a multi-threading sensor operating system. Our experimental results show that the performs efficiently in both time and space compared with existing memory allocation mechanisms.

A major research challenge in the field of sensor networks is the distributed resource allocation problem, which concerns how the limited resources in a sensor network should be allocated or scheduled to minimize costs and maximize the network capability. In this paper, we propose the Adaptive Distributed Resource Allocation (ADRA) scheme, which specifies relatively simple local actions to be performed by individual sensor nodes in a sensor network for mode management. Each node adapts its operation over time in response to the status and feedback of its neighboring nodes. Desirable global behavior results from the local interactions between nodes.

We study the effectiveness of the ADRA scheme for a realistic application scenario; namely, the sensor mode management for an acoustic wireless sensor network to track vehicle movement. We evaluated the scheme via simulations, and also prototyped the acoustic wireless sensor network scenario using the Crossbow MICA2 motes. Our simulation and hardware implementation results indicate that the ADRA scheme provides a good tradeoff between performance objectives such as coverage area, power consumption, and network lifetime.

In this paper, we consider a sequential approach for decentralized detection problem in wireless sensor networks, and propose a new scheme for data fusion in the case of spatially and temporally identically and independently distributed observations. In addition, we investigate the performances of the proposed scheme in terms of average number of observations and total energy consumption, and further compare the results with those of a non-sequential scheme. As a result, we determined the region of individual node power where the proposed scheme outperforms the non-sequential scheme in terms of both average number of observations and total energy consumption.

Wireless Sensor Networks are deployed in demanding environments, where application requirements as well as network conditions may change dynamically. Thus the protocol stack in each node of the sensor network has to be able to adapt to these changing conditions. Historically, protocol stacks have been designed with strict layering and strong interface between the layers leading to a robust design. However, cross-layer information sharing could help the protocol modules to make informed decisions and adapt to changing environmental conditions. There have been ad hoc approaches to facilitating cross-layer cooperation for adaptability. However, there has been no concerted effort at providing a uniform framework for cross-layer adaptability that preserves the modularity of a conventional protocol stack. This paper presents a novel service, information exchange service (IES), as a framework for cross-module information exchange. IES is a centrally controlled bulletin-board where different modules can post available data, or request for useful information, and get notified when the information becomes available. IES is integrated into the proposed architecture that preserves the benefits of layering while facilitating adaptability. IES has been implemented in TinyOS and Linux, to show both the feasibility of the design as well as demonstrate the utility of cross-layering to increase application longevity.

A mobile ad hoc network is an autonomous wireless network which consists of mobile nodes without any base stations. When a source node communicates with a destination node outside the transmission range of the source node, communication between the source node and the destination node can be through some other nodes between them. Many schemes such as routings and applications have been proposed for mobile ad hoc networks. However, since these schemes tend to be evaluated only through simulation experiments, it is not known whether they work effectively in real environments or not. Therefore, in order to verify their practical use in mobile ad hoc networks, it is necessary to perform field experiments using actual mobile nodes. If the network size is large, it is difficult to perform field experiments due to problems on limited battery, difficulty of topology control and so on. Realization of rapid topology change of the ad hoc networks topology is especially difficult. In order to solve this problem, this paper proposes a testing environment for mobile ad hoc network software, which emulates the field experiments in wired networks. The existing emulators are scenario-driven. So information of locations and movements of nodes from start of the test to end is given in advance. Unlike the existing emulators, the proposed environment adopts scenario-independent mechanism. The proposed environment can control any network topology for routing in mobile ad hoc networks. The proposed environment consists of a positioning server and multiple testing nodes in wired networks. The positioning server virtually configures mobile ad hoc networks and distributes their information such as the node positions to the testing nodes. And testing nodes themselves deliver their position information to the others. By exchanging messages between the server and testing nodes, any network topology for mobile ad hoc networks can be configured and dynamically changed while testing. It is therefore expected to effectively develop and verify routing protocols and applications for mobile ad hoc networks.

This paper describes the creation of Microcosm, a low cost wireless sensor network test-bed within a controlled environment to facilitate WSN experiments in three dimensions, with an emphasis on executing sensing-related experiments. The design of the sensing hardware, software, support tools and the experimental environment itself are given. Issues related to the design of this configuration are discussed, with the potential pitfalls and eventual solutions alike given. Finally, current and future uses for the test-bed are listed.

Software development for Wireless Sensor Networks (WSNs) suffers from the adverse condition that WSN software systems can usually not be tested on a system-level in their final operations environment, as WSN deployment is an expensive and time-consuming process. Several authors therefore propose to interlock application software test tightly with simulation. In this paper, we introduce an XML-based description language that allows the WSN programmer to define a common Hardware Abstraction Layer (HAL) for seamless transfer of WSN application code between WSN node target platforms and simulator-provided platforms. We show how a common network simulator can be enhanced to fully support system-level testing of WSN application code, make some comments on the resulting changes in the software development process, and finally illustrate our approach by an example.