Beat Weiss

Dynamic Cell Planning for Wireless Infrared In-House Data Transmission

A simulation model for characterizing the geometry of infrared communication cells representing full connectivity has been developed. Measured spatial daylight distributions in a large open-plan office have been incorporated into the model. With a 1 Mbps transmission system based on 16-slot pulse-position modulation and a non-directed infrared source of 250 mW average optical power, cell sizes of up to 10 m and 20 m diameter can be achieved for peer-to-peer and client/server topologies, respectively. Daylight variations cause severe distortions and size reductions of the cells. A transmission system with adaptive data rate control (10 kbps to 10 Mbps) maintains full network connectivity within the cells at the expense of a graceful throughput degradation for terminals exposed to high levels of ambient light.

The IBM wireless sensor networking testbed

This paper describes the wireless sensor networking testbed built at the IBM Zurich Research Laboratory. The testbed has been used to address a wealth of exciting research challenges. Performance evaluations have been carried out with short-range wireless communication technologies, which are highly relevant for sensor networking such as IEEE 802.15.4/ZigBee networks, Bluetooth WPANs, and IEEE 802.11b WLANs. With the testbed, the merits of wireless mesh networking for range extension and reliability enhancement have been explored. New light-weight messaging protocols for communication between sensors and an application server have been tested which allow to bring messaging-oriented middleware down to very low-end sensors and actuators. In addition, the testbed has been used to develop sensor applications for remote metering and location-sensing

A power-efficient wireless sensor network for continuously monitoring seismic vibrations

We present a novel power-efficient wireless sensor network for continuously monitoring and analyzing seismic vibrations with sensor nodes and forwarding the retrieved information with low-cost relay nodes to backend applications. The applied vibration sensing algorithms are derived from the DIN 4150–3 standard. All nodes in the network are battery-powered and equipped with an IEEE 802.15.4 compatible radio transceiver. The nodes communicate with each other by executing a novel power-efficient protocol stack, which provides all network functions required by the vibration-sensing application and uses a publish/subscribe messaging protocol for communicating between the network nodes and the backend applications. Results obtained in certification and field tests show that the proposed vibration-sensing solution is standard-compliant, and that the wireless vibration sensor network (WVSN) exhibits excellent performance in terms of packet delivery rate, latency, and power efficiency.

A case for centrally controlled wireless sensor networks

In this article we present the Intelligent, Manageable, Power-Efficient and Reliable Internetworking Architecture (IMPERIA), a centrally managed architecture for large-scale wireless sensor networks (WSNs). We discuss the advantages of a centralized management over distributed approaches and derive our design by rigorously minimizing the amount of state information on individual sensor nodes and all sources of message collision during network operations. The result is a clustered multi-hop TDMA protocol that globally synchronizes the network and collects data at ultra-low power consumption. We present the end-to-end architecture and detail the algorithms we developed for (a) efficient network topology discovery and link quality estimation, (b) combined routing and clustering for pre-defined basestations, and (c) the scheduling of the medium access for multi-cluster and multi-channel data collection. IMPERIA has been implemented on TinyOS and IBMs Mote Runner and successfully deployed in applications for vibration sensing as well as datacenter energy management. This article summarizes the performance results from simulations, laboratory experiments, and deployment measurements that support our design decisions.

Wireless sensor network for continuous temperature monitoring in air-cooled data centers: applications and measurement results

Temperature monitoring in data centers is essential for reliably operating the data processing equipment and minimizing the required cooling energy. For this purpose, we track the temperatures at key locations in the data center with low-cost sensors and forward the captured information via the ZRL Data Center Wireless Sensor Network (DCWSN) to a monitoring client. Applications include continuous temperature monitoring, data collection for thermal modeling, and temperature sensing for real-time control of cold air flow and workload allocation. The DCWSN has been successfully deployed in production data centers.