Marcos Augusto M. Vieira

Survey on wireless sensor network devices

Wireless sensor networks are networks of compact microsensors with wireless communication capability. These small devices are relatively cheap with the potential to be disseminated in large quantities. Emerging applications of data gathering range from the environmental to the military. As autonomous devices they can provide pervasive distributed and collaborative network of computer nodes. Architectural challenges are posed for designers such as computational power, energy consumption, energy sources, communication channels and sensing capabilities. Embedded Systems provide the computational platform for hardware and software components to interact with the environment and other nodes. This survey presents the current state-of-the-art for wireless sensor nodes, investigating and analyzing these challenges. We discuss the characteristics and requirements for a sensor node mainly processing, communications, power and sensing components. In this survey we present a comprehensive comparative study of sensor nodes platforms, energy management techniques, off-the-shelf microcontrollers, battery types and radio devices.

Scalable and practical pursuit-evasion with networked robots

In this paper, we consider the design and implementation of practical pursuit-evasion games with networked robots, where a communication network provides sensing-at-a-distance as well as a communication backbone that enables tighter coordination between pursuers. We first develop, using the theory of zero-sum games, an algorithm that computes the minimal completion time strategy for pursuit-evasion when pursuers and evaders have same speed, and when all players make optimal decisions based on complete knowledge. Then, we extend this algorithm to when evader are significantly faster than pursuers. Unfortunately, these algorithms do not scale beyond a small number of robots. To overcome this problem, we design and implement a partition algorithm where pursuers capture evaders by decomposing the game into multiple multi-pursuer single-evader games. We show that the partition algorithm terminates, has bounded capture time, is robust, and is scalable in the number of robots. We then describe the design of a real-world mobile robot-based pursuit evasion game. We validate our algorithms by experiments in a moderate-scale testbed in a challenging office environment. Overall, our work illustrates an innovative interplay between robotics and communication.

Programmable Networks—From Software-Defined Radio to Software-Defined Networking

Current implementations of Internet systems are very hard to be upgraded. The ossification of existing standards restricts the development of more advanced communication systems. New research initiatives, such as virtualization, software-defined radios, and software-defined networks, allow more flexibility for networks. However, until now, those initiatives have been developed individually. We advocate that the convergence of these overlying and complementary technologies can expand the amount of programmability on the network and support different innovative applications. Hence, this paper surveys the most recent research initiatives on programmable networks. We characterize programmable networks, where programmable devices execute specific code, and the network is separated into three planes: data, control, and management planes. We discuss the modern programmable network architectures, emphasizing their research issues, and, when possible, highlight their practical implementations. We survey the wireless and wired elements on the programmable data plane. Next, on the programmable control plane, we survey the divisor and controller elements. We conclude with final considerations, open issues and future challenges.

CodeDrip: Data Dissemination Protocol with Network Coding for Wireless Sensor Networks

In this paper, we present CodeDrip, a data dissemination protocol for Wireless Sensor Networks. Dissemination is typically used to query nodes, send commands, and reconfigure the network. CodeDrip utilizes Network Coding to improve energy efficiency, reliability, and speed of dissemination. Network coding allows recovery of lost packets by combining the received packets thereby making dissemination robust to packet losses. While previous work in combining network coding and dissemination focused on bulk data dissemination, we optimize the design of CodeDrip for dissemination of small values. We perform extensive evaluation of CodeDrip on simulations and a large-scale testbed and compare against the implementations of Drip, DIP and DHV protocols. Results show that CodeDrip is faster, smaller and sends fewer messages than Drip, DHV and DIP protocols.

NanoRouter: A Quantum-dot Cellular Automata Design

We present NanoRouter, a new router architecture implemented as a quantum-dot cellular automata (QCA). A router is a key component in the Internet core. It allows packets to be transferred in the Internet. QCA is a promising nanoscale technology where components have nano size, ultra-low power consumption and could have a clock rate on the terahertz range. In a bottom-up approach, we first describe the building blocks that compose NanoRouter such as crossbar, demux and parallel-to-serial converter and then describe the full architecture. We demonstrate the functionality, test and validate the proposed architecture and provided performance evaluations of NanoRouter. This new router architecture can increase the speed of the Internet core.

Mitigating multi-path fading in a mobile mesh network

By using robots as routers, a team of networked robots can provide a communication substrate to establish a wireless mesh network. The mobile mesh network can autonomously optimize its configuration, increasing performance. One of the main sources of radio signal fading in such a network is multi-path propagation, which can be mitigated by moving the senders or the receivers on the distance of the order of a wavelength. In this paper, we measure the performance gain when robots are allowed to make such small movements and find that it may be as much as 270%. Our main contribution is the design of a system that allows robots to cooperate and improve the real-world network throughput via a practical solution. We model the problem of which robots to move as a distributed constraint optimization problem (DCOP). Our study includes four local metrics to estimate global throughput.

Robust Serial Nanocommunication With QCA

We present a serial communication system implemented as quantum-dot cellular automata (QCA). QCA is a promising alternative to the current CMOS technology. It can be implemented at the nanoscale, reaching ultra-low power consumption and high clock rate. Communication systems are important in current computer systems and it is expected to be even more important in near future. Although QCA has been widely studied in the development of logic circuits, there are few studies applying this promising technology to the design of communication systems. In a bottom-up approach, we describe the parallel-to-serial and serial-to-parallel converters, which are essential to the serial communication. We also propose and present components for robust communication, such as QCA circuits for Hamming code and parity checker. We demonstrate the functionality, test and validate the proposed architectures using QCADesigner simulator. Due to the importance of communication systems, this study is central in consolidating QCA as a possible CMOS substitute.

Efficient power management in real-time embedded systems

Power consumption became a crucial problem in the development of mobile devices, especially those that are communication intensive. In these devices, it is imperative to reduce the power consumption devoted to maintaining a communication link during data transmission/reception. The application of dynamic power management methodologies has contributed to the reduction of power consumption in general purpose computer systems. However, to further reduce power consumption in communication intensive real-time embedded devices, we have to consider the state of the computation and external events in addition to power management policies. In this paper we propose a model of an Extended Power State Machine (EPSM), where we adapt a Power State Machine to include the state of an embedded program in the power state machine formulation. This EPSM model is used to adapt the Quality of Service (QoS) in communication intensive devices to ensure low power consumption. In such development, a middleware layer fits in the systems architecture, being responsible for intercepting the data communication and implementing the EPSM. Also, a software tool was developed, allowing the Middleware Code to be generated based on the State Machine. A case study demonstrates the application of the proposed model to a real situation.

Language emulator, a helpful toolkit in the learning process of computer theory

Language Emulator, written in Java, is a toolkit to help undergraduate students to understand the concepts of Automata Theory. The software allows the manipulation of regular expressions, regular grammars, deterministic finite automata, nondeterministic finite automata with and without lambda transitions, and Moore and Mealy machines. Language Emulator introduces error-detecting and internationalization functionalities into automata tools. It has been accepted by 95% of students in a recent survey, indicating that it is a helpful toolkit in learning Automata Theory.

eXtend collection tree protocol

In this work, we propose eXtend Collection Tree Protocol (XCTP), a routing protocol that is an extension of the Collection Tree Protocol (CTP). CTP is the de-facto standard collection routing protocol for Wireless Sensor Network (WSN). CTP creates a routing tree to transfer data from one or more sensors to a root (sink) node. But, CTP does not create the reverse path between the root node and sensor nodes. This reverse path is important, for example, for feedback commands or acknowledgment packets. XCTP enables communication in both ways: root to node and node to root. XCTP accomplishes this task by exploring the CTP control plane packets. XCTP requires low storage states and very low additional overhead in packets. With the reverse path, it is possible to implement reliable transport layer protocols for Wireless Sensor Network (WSN). Thus, we designed Transport Automatic Piggyback Protocol (TAP2), a transport protocol with Automatic Repeat-reQuest (ARQ) error-control on top of XCTP. We implemented these protocols on TinyOS and evaluated on TOSSIM. We compared XCTP with CTP, Routing Protocol for low-power and lossy networks (RPL), and Ad hoc On Demand Distance Vector (AODV) protocols. We conducted scalability and stress tests, evaluating them with different loads and number of nodes. Our results shows that XCTP is more reliable than CTP, delivering 100% of the packets. XCTP sends fewer control packets than RPL. XCTP is faster to recovery from network failures and also stores fewer states than AODV, thus being efficient and agile.