Showing papers by "Thiemo Voigt published in 2003"

Utilizing solar power in wireless sensor networks

Abstract: Sensor networks are designed especially for deployment in adverse and non-accessible areas without a fixed infrastructure. Therefore, energy conservation plays a crucial role for these networks. We propose to utilize solar power in wireless sensor networks, establishing a topology where, changing over time, some nodes can receive and transmit packets without consuming the limited battery resources. We propose and evaluate two protocols that perform solar-aware routing. The presented simulation results show that both protocols provide significant energy savings when utilizing solar power. The paper shows that incorporating the solar status of nodes in the routing decision is feasible and results in reduced overall battery consumption.

Solar-Aware Routing in Wireless Sensor Networks

Abstract: In wireless sensor networks energy is a valuable but not necessary scarce resource. While it is often assumed that nodes in sensor networks are powered by batteries, other energy sources such as solar power may provide unlimited energy resources to a changing subset of the nodes. Since these nodes can receive and transmit packets without consuming battery power, routing via these nodes is appealing. In this paper, we present solar-aware routing, a routing protocol for wireless sensor networks that preferably routes traffic via nodes powered by solar energy. Simulations show that solar-aware routing can provide significant energy savings in many scenarios.

Bounds on the Energy Consumption of Routings in Wireless Sensor Networks

Abstract: Energy is one of the most important resources in wireless sensor networks. We use an idealized mathematical model to study the impact of routing on energy consumption. Our results are very general and, within the assumptions listed in Section 2, apply to arbitrary topologies, routings and radio energy models. We find bounds on the minimal and maximal energy routings will consume, and use them to bound the lifetime of the network. The bounds are sharp, and can be achieved in many situations of interest. We illustrate the theory with some examples.

Performance impact of web services on Internet servers

Abstract: While traditional Internet servers mainly served static and later also dynamic content, the popularity of Web services is increasing rapidly. Web services incorporate additional overhead compared to traditional web interaction. This overhead increases the demand on Internet servers which is of particular importance when the request rate to the server is high. We conduct experiments that show that the imposed overhead of Web services is non-negligible during server overload. In our experiments the response time for Web services is more than 30% higher and the server throughput more than 25% lower compared to traditional web interaction using dynamically created HTML pages.

A highly flexible testbed for studies of ad-hoc network behaviour

Abstract: Studies of mobile ad-hoc networks are often based on simulation and their underlying, necessarily simplified assumptions of physical reality. In order to analyse the practical problems we built our own hardware and software. The hardware consists of a core Motorola controller and different wired and wireless interfaces like a Bluetooth and a 433/868 MHz RF module. It allows therefore analysing different scenarios: First, the deployment of a pure ad-hoc network using Bluetooth or 433/868 MHz RF modules. Scenarios going beyond this cover the connection of Bluetooth piconets using the complementary RF technology. This overcomes the proximity requirements of Bluetooth scatternets. Finally, hybrid scenarios with some nodes connected to the Internet and providing Web access over a multihop ad-hoc network can be studied. In this paper we present the testbed and solutions realized up to now. These include home automation scenarios as well as support for mobile ad-hoc games.

Experiences using a dual wireless technology infrastructure to support ad-hoc multiplayer games

Abstract: Multiplayer games for mobile wireless devices are becoming increasingly popular. Many modern devices such as PDAs or mobile telephones are equipped with Bluetooth interfaces. Bluetooth facilitates the formation of ad-hoc networks thus enabling users to set up multiplayer games spontaneously. On the other hand, Bluetooth has strong restrictions in terms of transmission range and the number of users per piconet. We deploy additional infrastructure in order to overcome these shortcomings. This infrastructure uses a second wireless technology that sets up and maintains a consistent view of a distributed game by exchanging information about the status and location of players. We set up an experimental testbed consisting of single-board communication devices developed in our lab and Bluetooth-equipped PDAs.Our experiments show that the proposed infrastructure is able to extend the range of games beyond the coverage of a Bluetooth piconet. Furthermore, we are able to track players. Smooth handovers between piconets are also possible. However, due to the current limitations of Bluetooth, handovers are not fast enough to enable highly interactive gaming across different piconets. We present a game that uses this and discuss future application scenarios.

Utilizing Renewable Energy in Cluster-based Sensor Networks

Abstract: Energy conservation plays a crucial in wireless sensor networks since such networks are designed to be placed in hostile and non-accessible areas. While battery-driven sensors will run out of battery sooner or later, the use of renewable energy sources such as solar power or gravitation may extend the lifetime of a sensor. We propose to utilize solar power in wireless sensor networks and extend LEACH a well-known cluster-based protocol for sensor networks to become solar-aware. The presented simulation results show that making LEACH solar-aware significantly extends the lifetime of sensor networks.