Deploying a Wireless Sensor Network on an Active Volcano

ABSTRACT

Augmenting heavy and power-hungry data collection equipment with lighter, smaller wireless sensor network nodes leads to faster, larger deployments. Arrays comprising dozens of wireless sensor nodes are now possible, allowing scientific studies that aren’t feasible with traditional instrumentation. Designing sensor networks to support volcanic studies requires addressing the high data rates and high data fidelity these studies demand. The authors’ sensor-network application for volcanic data collection relies on triggered event detection and reliable data retrieval to meet bandwidth and data-quality demands.

1. Introduction

1.Today’s typical volcanic data-collection station consists of a group of bulky, heavy, power-hungry components that are difficult to move and require car batteries for power. 2.Remote deployments often require vehicle or helicopter assistance for equipment installation and maintenance.3. Local storage is also a limiting factor — stations typically log data to a Compact Flash card or hard drive, which researchers must periodically retrieve, requiring them to regularly return to each station.

The geophysics community has wellestablished tools and techniques it uses to process signals extracted by volcanic data-collection networks. 4.These analytical methods require that our wireless sensor networks provide data of extremely high fidelity a single missed or corrupted sample can invalidate an entire record. 5.Small differences in sampling rates between two nodes can also frustrate analysis, so samples must be accurately time stamped to allow comparisons between nodes and between networks.

An important feature of volcanic signals is that much of the data analysis focuses on discrete events, such as eruptions, earthquakes, or tremor activity. Although volcanoes differ significantly in the nature of their activity, during the deployment, many interesting signals  spanned less than 60 seconds and occurred several dozen times per day. This let us design the network to capture time-limited events, rather than continuous signals.

6. However, wireless sensor nodes’ low radio bandwidth makes them inappropriate for such studies; thus, we focused on triggered event collection when designing our network. 7.Volcanic studies also require large internode separations to obtain widely separated views of seismic and infrasonic signals as they propagate. 8.Node failure poses a serious problem in sparse networks because a single failure can obscure a large portion of the network. In the upcoming sections we illustrate Sensor-Network Application Design(2),Design issues related to deploying a WSN on an Volcano(3), early results(4), and finally conclusion(5).

2. Sensor-Network Application Design

Given wireless sensor network nodes’ current capabilities, we set out to design a data-collection network that would meet the scientific requirements we outlined in the previous section. Before describing our design in detail, let’s take a highlevel view of our sensor node hardware and overview the network’s operation. Figure 1 shows our sensor network architecture.

Figure 1. The volcano monitoring sensor-network architecture. The network consists of 16 sensor nodes, each with a microphone and siesmometer, collecting seismic and acoustic data on volcanic activity. Nodes relay data via a multihop network to a gateway node connected to a long-distance FreeWave modem, providing radio connectivity with a laptop at the observatory. A GPS receiver is used along with a multihop time-synchronization protocol to establish a network-wide timebase.

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