Introduction to the LabVIEW Wireless Sensor Network (WSN) Module

Publish Date: Sep 14, 2012 | 4 Ratings | 3.50 out of 5 |  PDF

Overview

The use of wireless communication technologies has become ubiquitous due to the freedom, distributed capabilities, and cost savings they offer. Wireless sensor networks (WSNs) have emerged as the next wave of wireless technology, enabling greatly distributed measurements across vast physical systems. With WSNs, you can more effectively analyze everything from rain forests and river deltas to the health and safety of buildings and bridges. A WSN consists of spatially distributed measurement devices that use sensors to monitor physical or environmental conditions. In addition to many wireless measurement nodes, a WSN system includes a gateway that collects data and provides connectivity back to a host application on a PC or embedded controller.

To effectively use this promising technology, you must overcome the challenges associated with configuring and managing data acquisition, efficiently analyzing the collected data, storing data for future analysis, and displaying data to the end user in a meaningful way. Engineers and scientists have been meeting these challenges for more than 20 years with NI LabVIEW, a graphical programming environment used to acquire, analyze, and present data. Over the years, LabVIEW has added the ability to program real-time systems, field-programmable gate arrays (FPGAs), ARM microcontrollers, and more. Now, with the LabVIEW Wireless Sensor Network (WSN) Module, you can use LabVIEW intuitive graphical programming to program NI WSN nodes. The resulting embedded software can help you extend node battery life, perform custom analysis, and reduce response times with embedded decision making.

Table of Contents

  1. Take Advantage of Rapid Development with Graphical Programming
  2. Extend Battery Life
  3. Perform Custom Analysis
  4. Reduce Response Time with Embedded Decision Making
  5. Reduce Costs and Increase Performance
  6. Related Resources

1. Take Advantage of Rapid Development with Graphical Programming

Programming wireless sensor nodes has traditionally required knowledge of embedded systems and an understanding of the specific text-based language selected by the vendor. With LabVIEW WSN, you can add intelligence to NI wireless sensor nodes using the same graphical programming approach that has become the industry standard for developing applications that acquire and process data. LabVIEW WSN also provides the flexibility to incorporate C code directly in line with the graphical code that runs on the node so you can reuse algorithms.

LabVIEW WSN greatly simplifies the process of creating embedded applications for NI WSN measurement nodes, as seen in these examples that blink an LED at a rate of 1 Hz.

 

LabVIEW WSN includes basic LabVIEW programming structures such as while loops, for loops, and case structures. It also features functions for floating-point math and analysis, eliminating the need for in-depth knowledge of integer and fixed-point data types. In addition, LabVIEW WSN provides hyperbolic, exponential, and trigonometric math functions along with functions for string manipulation to customize user messages that can be transmitted back to the host computer.

With just a few mouse clicks during development, you can compile and deploy your application over the air to the node through a wireless network for rapid development and testing. Additionally, for deployed systems, you no longer need to send a technician into the field to manually load new applications, which reduces your wireless system maintenance costs.

NI WSN measurement nodes are powered by a TI MSP430 microcontroller that is optimized for low-power, multiyear deployment instead of processor speed, memory, and computing power. Due to these power optimizations, NI WSN nodes have limited performance compared to other embedded LabVIEW targets. This limited performance is the reasoning behind calling LabVIEW WSN a module. For example, LabVIEW WSN does not include LabVIEW debugging features, such as highlight execution and stepping through the code at run time. However, you can send and receive string-based user messages to and from the node to debug your deployed application. Also, LabVIEW WSN is limited to serial execution, so parallel LabVIEW structures do not execute concurrently. Because the node has limited resources, only trigonometric, exponential, and hyperbolic analysis functions are supported; however, you can create your own functions using the floating-point math functions included with LabVIEW WSN.

 

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2. Extend Battery Life

By default, an unprogrammed node transmits every sample acquired back to the gateway at a fixed sample rate, so the battery life of a node is directly linked to its sample rate. With LabVIEW WSN, you can customize the node’s behavior to add intelligence that extends battery life by controlling the sample rate and determining when to transmit data.

The radio is a significant consumer of power in a node; therefore, in applications that do not require every sample to be sent to the gateway, you can greatly increase battery life by transmitting only required or meaningful data. Some common transmission criteria include a threshold value or a deadband percentage. In addition, you can reduce the number of samples transferred back to the host by performing averaging and data reduction on the node using the included floating-point math functions.

You also can extend battery life by creating logic that optimizes the node’s behavior for specific operating conditions or network requirements. For instance, if the battery voltage decreases to a critical level, you can program the node to respond by notifying the operator and decreasing its sample and transmission rate to conserve the remaining battery life.

In addition, you can use LabVIEW WSN to handle digital value change event detection on the node. When you configure a digital input for event detection, the node can sleep until an event occurs, providing significant power savings when compared to polling. 

 

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3. Perform Custom Analysis

LabVIEW WSN gives you the power to convert raw acquired data into meaningful information. For example, sensor measurements can be converted from raw voltage to engineering units directly on the node. This provides a level of abstraction so that the host application does not have to scale the data after reading from each measurement node. In addition, the flexibility to perform the conversion locally on the node allows for more intuitive and power-sensitive algorithms that enable conditional transmission of data based on threshold or deadband criteria.

Because an unprogrammed NI WSN measurement node transmits every sample acquired back to the gateway, the maximum sample rate of an unprogrammed node is limited by the time incurred transmitting each sample to the gateway. By programming a node with LabVIEW WSN, you can increase analog and digital acquisition performance by acquiring samples in batches without incurring the overhead of transmitting each sample. Using floating-point math and analysis, you can then process this data to extract and transmit required information to the gateway.

 

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4. Reduce Response Time with Embedded Decision Making

With LabVIEW WSN, you can embed decision making on NI WSN measurement nodes, which allows decisions to be made autonomously without transmitting the stimulus and response to and from a host computer or embedded controller. You can use the digital output lines on an NI WSN measurement node to actuate relays and perform simple on/off control. For example, the decision to turn on a fan when a temperature threshold is exceeded can be embedded on the node, reducing response time and increasing reliability by removing the need for host interaction.

  

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5. Reduce Costs and Increase Performance

LabVIEW WSN helps you reduce costs through rapid development while increasing performance and flexibility. Customize the behavior of your NI WSN measurement nodes to extend battery life, perform custom analysis, and reduce response time with embedded decision making.

To get started, check out the NI WSN Getting Started Kit and evaluate NI WSN and the LabVIEW WSN Module for 60 days. 

 

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6. Related Resources

LabVIEW Wireless Sensor Network Module Beta - Under the Hood

Programmable WSN Node Power and Performance Benchmarks

Purchase Programmable NI WSN Nodes

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