Abdalkarim Awad

Adaptive Distance Estimation and Localization in WSN using RSSI Measures

Localization is one of the most challenging and important issues in wireless sensor networks (WSNs), especially if cost-effective approaches are demanded. In this paper, we present intensively discuss and analyze approaches relying on the received signal strength indicator (RSSI). The advantage of employing the RSSI values is that no extra hardware (e.g. ultrasonic or infra-red) is needed for network-centric localization. We studied different factors that affect the measured RSSI values. Finally, we evaluate two methods to estimate the distance; the first approach is based on statistical methods. For the second one, we use an artificial neural network to estimate the distance.

Virtual Cord Protocol (VCP): A flexible DHT-like routing service for sensor networks

Efficient data management techniques are needed in wireless sensor networks (WSNs) to counteract issues related to limited resources, e.g. energy, memory, bandwidth, as well as limited connectivity. Self-organizing and cooperative algorithms are thought to be the optimal solution to overcome these limitations. On an abstract level, structured peer-to-peer protocols provide O(1) complexity for storing and retrieving data in the network. However, they rely on underlayer routing techniques. In this paper, we present the virtual cord protocol (VCP), a virtual relative position based efficient routing protocol that also provides means for data management, e.g. insert, get, and delete, as known from typical distributed hash table (DHT) services. The key contributions of this protocol are independence of real location information by relying on relative positions of neighboring nodes, short virtual paths because successors and predecessors are in their vicinity, and high scalability because only information about direct neighbors is needed for routing. Furthermore, VCP inherently prevents dead-ends and it is easy to be implemented.

Exploiting Virtual Coordinates for Improved Routing Performance in Sensor Networks

We present the Virtual Cord Protocol (VCP), which exploits virtual coordinates to provide efficient and failure tolerant routing and data management in sensor networks. VCP maintains a virtual cord interconnecting all the nodes in the network and which, operating similar to a Distributed Hash Table (DHT), provides means for inserting data fragments into sensor nodes and retrieving them. Furthermore, it supports service discovery using indirections. VCP uses two mechanisms for finding paths to nodes and associated data items: First, it relies on the virtual cord that always provides a path toward the destination. Second, locally available neighborhood information is exploited for greedy routing. Our simulation results show that VCP is able to find paths close to the shortest path (achieving a stretch ratio of less than 125 percent) with very low overhead. We also extended VCP with data replication mechanisms to improve failure handling. The routing performance of VCP, which clearly outperforms other ad hoc routing protocols such as Dynamic MANET On Demand (DYMO), is similar to other virtual addressing schemes, e.g., Virtual Ring Routing (VRR). However, we improved VCP to handle frequent node failures in an optimized way. The presented results outline the capabilities of VCP to handle such cases more efficiently compared to other protocols. We also compared the capabilities to reliably store and retrieve data in the network to Geographic Hash Tables (GHTs). VCP, in the worst case, performs similar to GHTs, but outperforms this protocol in most cases, especially when complex routing is involved.

On the Need for Passive Monitoring in Sensor Networks

Debugging and analyzing wireless sensor networks (WSNs) are important tasks for improving the quality and performance of the network. In this paper, Pimoto is to be presented, which is a distributed passive monitoring system implemented for debugging and analyzing WSNs. It is based on a hierarchical structure allowing to monitor different networks simultaneously and to analyze the obtained information at a dedicated PC. The system relies on three components. The first element is the monitoring node. It intercepts the radio packets in the vicinity and sends received packet information to a gateway using a second radio interface in order to prevent intrinsic interactions with the sensor network operation. The gateway has the ability to communicate directly with the monitoring node and to transfer all the collected monitoring data to the third component, a dedicated PC (server), in the hierarchy using standard TCP/IP communication. The packets are analyzed and visualized on the server using the standard network monitoring and analyzing tool Wireshark. The most important characteristic of this monitoring concept is the passive operation, i.e. the normal operation in the WSN is not influenced by the analyzer.

P2P-based routing and data management using the virtual cord protocol (VCP)

We present Virtual Cord Protocol (VCP), a virtual relative position based routing protocol for sensor networks that also provides methods for data management as known from standard DHT services. Self-organizing and cooperative algorithms are thought to be the optimal solution to overcome the inherent resource limitations in sensor networks. On an abstract level, DHT techniques offer O(1) complexity data lookup. Unfortunately, they usually rely on underlayer routing techniques. The key contributions of VCP are the independence of real location information by relying on relative positions of neighboring nodes, successors and predecessors in the cord are always in their vicinity, and the high scalability because only information about direct neighbors are needed for routing. Furthermore, VCP inherently prevents dead-ends and it is easy to be implemented.

Inter-Domain Routing and Data Replication in Virtual Coordinate Based Networks

In recent work it has been shown that the use of virtual coordinates or identifiers for efficient routing and data management has several advantages compared to the use of predefined addresses or geographical coordinates. However, these advantages only hold for single domain networks with limited mobility. In this paper, we discuss the challenges arising from using virtual coordinates for routing (to a particular sensor ID or to indexed data or resources) in ad hoc and sensor networks in multi-domain network scenarios. We show the feasibility of inter-domain routing by exploiting a concept that is central to most virtual coordinate approaches: the availability of data management operation using a DHT like mechanism. Based on the Virtual Cord Protocol (VCP), we show how inter-domain routing can be realized using appropriate indirections. Furthermore, we investigate the possibility of replicating data among different networks, or DHTs, to provide seamless data access in multi-domain environments. Our simulation results clearly show that both functions can be realized with only marginal overhead.

Advantages of virtual addressing for efficient and failure tolerant routing in sensor networks

We study the capabilities of virtual addressing schemes for efficient and failure tolerant routing in sensor networks. In particular, we present the Virtual Cord Protocol (VCP) that uses techniques known from peer-to-peer networks, i.e. Distributed Hash Tables (DHTs) are used to associate data items in sensor networks with particular node addresses. The addresses of nodes are dynamically maintained by the protocol to form a virtual cord. VCP uses two mechanisms for finding paths to nodes and associated data items: First, it relies on the virtual cord that always points towards the destination. Furthermore, locally available neighborhood information is exploited for greedy routing. Our simulation results show that VCP is able to find paths close to the possible shortest path with very low overhead. The routing performance of VCP, which clearly outperforms other ad hoc routing protocols such as Dynamic MANET On Demand (DYMO), is similar to other virtual addressing schemes, e.g. Virtual Ring Routing (VRR). However, we improved VCP to handle frequent node failures in an optimized way. The results presented in this paper outline the capabilities of VCP to handle such cases.

SGsim: A simulation framework for smart grid applications

Simulation tools are an essential component of any emerging technology. In this paper we present SGsim, a framework to simulate different applications in the context of smart grid. The framework supports real time simulation. Therefore it is possible to evaluate time-critical applications such as real time monitoring and control. The framework combines two main simulators (1) OMNeT++, a discrete event simulator that is used mainly to simulate data communication systems and (2) OpenDSS, a tool to calculate the power flow in power grids. Moreover, the framework supports smart grid related standards such as IEEE C37.118. This way it is possible to integrate standard smart grid tools such as openPDC. Furthermore, an optimization toolbox is integrated in the simulator in addition to the capability to communicate with other tools such as MATLAB and R. We performed a set of case studies to show the capabilities of the simulator.

Exploiting day-ahead electricity price for maximized profit of photovoltaic systems

This paper proposes a methodology for optimal power management in a house with photovoltaic cells and battery storage. The proposed method exploits the day-ahead electricity market to enhance the profit of a household. An hourly-discretized optimization algorithm is proposed to identify the optimum daily operational strategy to be followed by the photovoltaic system, provided that a forecast for solar-power and load is available. This model is suitable to be applied in the real time operation of a typical house. The proposed strategy maximizes the individual revenue without shifting power demand. We explored the proposed algorithm with and without feed-in tariff. The results show that a typical house can save about 300 e/year when applying optimized power management.

SGsim: Co-simulation Framework for ICT-Enabled Power Distribution Grids

Empowering power grids with ICT is fundamental for the future power grid. Simulation plays an essential role for evaluating emerging smart grid applications. The presented co-simulation framework SGsim is based on two main simulators, OMNeT++ and OpenDSS. With newly added components, smart grid applications in the electricity distribution network can now be investigated and evaluated. Conservation Voltage Reduction (CVR) is a mechanism to reduce the power demand which eventually will reduce the energy consumption. In a case study, the co-simulation framework is used to explore the potential energy saving by applying a closed-loop CVR inside a residential power grid.