This paper analyzes an indoor positioning system that uses white lighting LEDs. Modulated signals transmitted by the LEDs are used as the basis of time-of-arrival-based distance estimation. The theoretical limits on the accuracy of estimation are calculated by deriving the Cramer-Rao bound for intensity modulated windowed sinusoidal signals. Calculations for a typical indoor scenario, assuming perfect synchronization between transmitter and receiver, but using realistic values for other parameters show that very accurate distance estimates are achievable, with typical errors being in the order of centimeters depending on the frequency and power of the sinusoidal signals, the distance from the LED and the properties of the LED and the photoreceiver.Index Terms-Cramer-Rao bound, indoor localization, intensity modulation and direct detection, ranging, time-of-arrival, visible light communication, windowed sinusoid.

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SUMMARYWe present a review of recent activities in swarm robotic research, and analyse existing literature in the field to determine how to get closer to a practical swarm robotic system for real world applications. We begin with a discussion of the importance of swarm robotics by illustrating the wide applicability of robot swarms in various tasks. Then a brief overview of various robotic devices that can be incorporated into swarm robotic systems is presented. We identify and describe the challenges that should be resolved when designing swarm robotic systems for real world applications. Finally, we provide a summary of a series of issues that should be addressed to overcome these challenges, and propose directions for future swarm robotic research based on our extensive analysis of the reviewed literature.

Wireless Sensor Networks (WSNs) are a new technology foreseen to be used increasingly in the near future due to their data acquisition and data processing abilities. Security for WSNs is an area that needs to be considered in order to protect the functionality of these networks, the data they convey and the location of their members. The security models and protocols used in wired and other networks are not suited to WSNs because of their severe resource constraints, especially concerning energy. In this article, we propose a centralized intrusion detection scheme based on Support Vector Machines (SVMs) and sliding windows. We find that our system can detect black hole attacks and selective forwarding attacks with high accuracy without depleting the nodes of their energy.

White lighting LEDs offer great potential for high speed communications, especially for indoor applications. However, for their widespread adoption, two important issues need to be addressed: the lack of diversity in multiple-input multiple output (MIMO) systems, and the small field of view of receivers. In this paper, we describe a design using a hemispherical lens in the receiver that solves these problems. By using classical optics, we derive exact expressions for the channel gain and the optical power density of the projected images. Simulation results of a typical indoor scenario show that the new system has a wide field of view, and provides adequate channel gain for angles of incidence as large as 70 degrees. We present the distribution of optical power on the imaging plane for various receiving positions and tilted receivers over a number of representative indoor scenarios. They show that the images of LEDs are clearly distinguishable. The results demonstrate the presence of low channel correlations between individual transmitters and receivers. Consequently, this confirms that the new technique is capable of providing significant diversity order for MIMO optical wireless applications.

Almost every routing protocol in mobile ad hoc networks (MANETs) depends on a broadcast scheme to disseminate routing information. For this reason, creating an efficient broadcast scheme is important and a large variety of approaches have been proposed. Among them, multipoint relay (MPR) is one of the distributed broadcast schemes which is efficient and simple. Based on the MPR concept, many broadcast schemes have been proposed, which generally focus on different performance issues. In this article we present a comprehensive survey of MPR-based broadcast schemes, classified into three categories based on their objectives. Different heuristics are described, and the evaluation of their performances is provided in light of their costs. Advantages and limitations of different broadcast schemes are also highlighted.