The Contiki Operating System - Contiki 2.4 Released

In September we announced that the Contiki team had developed a port for Crossbow's MICAz platform. We are excited to inform our users that the team is proud to announce the release of version 2.4 of the Contiki operating system! Contiki 2.4 brings a number of new improvements over previous versions, several bugfixes, and an overall improved stability of the system. The low-power wireless MAC protocols have gotten an overhaul, improving power-efficiency and improved collision and interference handling. The COOJA/MSPsim simulation environment has received a significant speedup. Many improvements and bugfixes has been made to the uIP code as well as the SICSlowpan implementaion of 6lowpan IPv6-over-802.15.4.

See the changelog for full details and go to the download section to download the 2.4 release!

The Buzz about BumbleBee

The Application Idea Contest

About a year and a half ago the Samraksh Company introduced a new mote-scale radar. The BumbleBee is a coherent, pulsed Doppler radar offering rich information at a strikingly low price (i.e., $100 each as compared to as much as $4,000 to $5,000 each for previous mote-scale radars). The BumbleBee measures radial velocity directly allowing users to determine the sign of the velocity and measure the time structure of relative motion very precisely, even for small motions!

Applications of the BumbleBee

While the typical mote-scale sensors might be as simple as a temperature or humidity sensor, and is rarely more complex than a PIR motion detector, the BumbleBee radar provides rich information about the details of motion of targets in its environment (or the details of the motion of the environment itself).The BumbleBee is capable of measuring movements to a relative accuracy of about 3 mm in its core operational zone which is from 1.5 m to 9.5 m, with a radial velocity of 2.6 cm/s to 2.6 m/s, and with components of motion below 100 Hz which are movements that are representative of human movements. Thus the BumbleBee, although a good motion detector, is uniquely suited for a variety of motion analyses, including items like:

1. Estimating the relative range profile, as a function of time, for a dominant target within the scene.
2. Separating the returns from multiple targets with different motion patterns within the same scene.
3. Recognizing specific motions patterns associated with unique events.
4. Characterizing the motion of various background environments at various times.

For example, the Samraksh Company demonstrated the ability to differentiate humans from dogs based on differences in the leg motion. The gap between simple motion detection and attempting to infer whether the target is two-legged or four-legged based on the way it moves, is quite large, and the highest value WSN applications may well be within this gap. This platform provides a large benefit at a small cost to somewhat more simple motion analysis.

Idea Contest

The Samraksh Company suspects that there will be high return from effort focused on conceiving applications for the BumbleBee rada as the difference between applications for the BumbleBee and traditional WSN applications is vast. To stimulate the development of applications that benefit from an understanding of the motion the company announced today that it is sponsoring an Application Idea Contest. Researchers and hobbyists who are willing to share their ideas for utilizing rich motion information, especially within the context of WSNs, with the larger community are encouraged to submit short descriptions of their ideas. Two outside judges will select winning ideas, and each winner will receive a free BumbleBee radar! In addition community members will be asked to provide feedback on winning ideas. It is hoped that this feedback will further facilitate creativity.

Company co-founder Kenneth Parker said, “We hope to create a little community around the process of creating new application ideas.” The company hopes that every graduate student considering a thesis or dissertation in a closely related area will first submit a couple of ideas to the community along with hobbyists working on slightly unorthodox ideas who would be willing to share their quirky insights!

When pressed on the question of whether this is a “real” contest, Parker insisted that not every idea will be deemed a winner, but hopes there will be many.The Samraksch company has set aside 100 radars for potential contest winners in 2010.

The idea contest website is currently somewhat minimalistic, but the infrastructure is in place for creating more community services as the community develops. Users are encouraged to send their comments or request to WebMaster@samraksh.com as well as visit the 'Application Ideas' section of the Samraksh site.

Implementing Application Ideas

Originally the BumbleBee was packaged for use with the TelosB Mote platform, although users can wire the BumbleBee to almost any mote platform. User experience has shown that in order to exploit the rich information about motion more complex signal processing is sometimes required. Because the hardware support for integer multiplication on the TelosB is constrained, as it is not supported by default in TinyOS, many of these applications are better implemented on the IRIS or Imote2, both of which can support quite sophisticated integer Digital Signal Processing (DSP) algorithms. To assist researchers in quickly developing applications that more fully exploit the potential of the BumbleBee the Samraksh Company has created interface boards so that BumbleBee’s can be connected out of the box to either the IRIS or Imote2. Winners may request interface boards for the platform of their choice.

For information on Crossbow's TelosB, Imote2 or IRIS Mote platforms, click here.
For information on the BumbleBee radar from the Samraksh Company, click here.

WSNs See Through Walls

Researchers at the University of Utah SPAN lab have found a way to see through walls to detect movement inside a building using wireless sensor networks!

The surveillance technique is called variance-based radio tomographic imaging and works by visualizing variations in radio waves as they travel to nodes in a wireless network. A person moving inside a building will cause the waves to vary in that location, the researchers found, allowing an observer to map their position.

The researchers, electrical engineering graduate student Joey Wilson and his faculty advisor Neil Patwari, have tested the technique with a 34-node wireless network using the IEEE 802.15.4 wireless protocol and TelosB hardware. By “interrogating” the space with signals and multiple receivers, the researchers found they were able to read the waves to detect the location of a moving object within a meter of accuracy.

In a mission-critical application, the researchers envisioned a building imaging scenario similar to the following: Emergency responders, military forces, or police arrive at a scene where entry into a building is potentially dangerous. They deploy radio sensors around (and potentially on top of) the building area, either by throwing or launching them, or dropping them while moving around the building. The nodes immediately form a network and self-localize, perhaps using information about the size and shape of the building from a database (e.g., Google maps) and some known-location coordinates (e.g., using GPS). Then, nodes begin to transmit, making signal strength measurements on links which cross the building or area of interest. The RSS measurements of each link are transmitted back to a base station and used to estimate the positions of moving people and objects within the building.

Locating interior movement from outside of a building is extremely valuable in emergency situations, enabling police, military forces, and rescue teams to safely locate people prior to entering. Variance-based radio tomography is a powerful new method for through-wall imaging that can be used to track the coordinates of moving objects. The cost of VRTI hardware is very low in comparison to existing through-wall imaging systems, and a single network is capable of tracking large areas. These features may enable many new applications that are otherwise impractical.

OceanSense: Realtime Ocean Environmental Sensing

How important are the oceans? Earth is the only planet in the Solar System that has a vast open ocean of liquid water, and it is the ocean that makes our planet uniquely life-bearing. Today, ocean life is regarded by many as more important in the total scheme of things than even plant life on land. There are microscopic plant cells in the top layer of the ocean that produce four times as much oxygen and food as plants on land produce. The bottom line is that there is no life without water and the global ocean is the defining characteristic of our planet. It is the original ecosystem.

Oceanography is of great importance for human beings. For hundreds of years, people have been recording ocean environmental data from scientific expeditions to coastal environmental research. However, even today the only real-time environmental data observation method is through Argo (Array for Real-time Geostrophic Oceanography), which does not come close to meeting the true requirements of oceanography research. Researchers at the Ocean University of China have developed a wireless sensor network for environmental monitoring at sea believing that with the recent progress of sensor networks - it is the tool for the future collection of data for oceanography research.  

Deployed off the seashore near the Moutain LAO of Qingdao, China, OceanSense is a system designed to obtain ocean environmental data in real-time. Using the TelosB Mote platform, the nodes are deployed on the surface of the sea collecting environmental data, such as temperature, light, tide velocity, sensor depth and RSSI from the testbed. The TelosB Motes were encapsulated in bottles and attached to lightweight supporting equipment to make them waterproof as well as raise them 1m above the ocean surface to enable optimal signal strength. To view the process used to create these ocean ready nodes, watch this video that shows the testing, creation and deployment of the OceanSense System.

The OceanSense system has been running for more than half a year, providing environmental monitoring data for further study. The motes communicate with the base station, which transmits collected data to a visualization system running on a database server. Users may then access the data using a browser-based web application that provides a scalar field mapping tool to depict temperature and light intensity as well as a vector field mapping tool to display the tide velocity.

The current system consists of 20 sensor nodes deployed in the field, reporting sensing data continuously to the base station. The complete system is designed to scale to hundreds of sensors covering the sea area off Taipingjiao, Tsingtao. For more information on the OceanSense solution visit the site here and click on the video below for a brief demo of the system and the deployment.

In a BLIP, pervasive IP has arrived.

by Martin Turon, Director of Wireless Software, Crossbow Technology, Inc.

IPv6 was invented in 1998, over ten years ago, yet less than 1% of devices use it.

Why is IPv6 important?

The first answer is "lots of addresses".

Think of your PC and the RAM memory inside. Until recently, 32-bit processors were pervasive, and you couldn't put more than 4GB (4 billion bytes) of memory in them because of the limits in 32-bit address spaces. Now most new computers are 64-bit, and they can address 18 quintillion bytes. The Internet will eventually be forced to "upgrade" its address space as well. Currently over 99% of devices use IPv4 which uses 32-bit IP addresses that are most commonly displayed as 4 bytes in decimal: 192.168.1.100. If you want to host a web server to the world, you typically claim a static IP and one of the 4 billion possibilities is yours forever. But the population of the world is 6.7 billion, so there aren't enough to go around! And what if everyone wants multiple devices that can be uniquely addressed to serve some critical information like a cluster of wireless sensor nodes?

IPv6 is clearly the answer. It provides a 128-bit address space allowing for over 240 undecillion uniquely addressable devices. To put that in perspective, the soon-to-be 6.8 billion people in the world will each be able to have over 300 million subnets with over 18 quintillion devices in each one. That is a total of over 50 octillion uniquely addressable devices per person!  Note: The unallocated address pools in IPv4 are anticipated to be exhausted in 2012.

Which leads to the second answer: "government mandates".

In May 2009, the Federal CIO Council of the US government issued an official roadmap for IPv6 adoption. The report provides a detailed overview of the technology, it's benefits, tips on the various services and how to transition. It also tasks other government agencies with developing concrete plans for how they will deploy IPv6 and requires quarterly review of their progress.

"We can't keep operating in an IPv4 world when we're talking about sensor networks, wireless communications and mobile networks. We need more IP addresses - globally unique IP addresses - and that's what IPv6 provides. We need a target network architecture that's scalable, secure and stable." - Pete Tseronis, Federal IPv6 Working Group Chair and Deputy Associate CIO of the Department of Energy

Since the release of this document, a flurry of articles regarding IPv6 adoption has been written up in the press.

---

How can big IPv6 addresses fit on tiny motes?

Almost in anticipation of the recent uptick in IPv6 adoption, back in March some researchers at UC Berkeley released an Open Source implementation of IPv6 running on TinyOS 2.x called BLIP (Berkeley Low-power Internet Protocol). The BLIP stack runs on mote-class hardware, specifically the TelosB and MicaZ. How did they manage to fit a protocol that uses 128-bit addresses onto a platform with only 4KB of RAM? Well, beyond the fact that Stephen Dawson-Haggerty and other contributors are really really smart, the IETF has had a number of efforts to define ways for IPv6 to run on lossy, low bandwidth links for a while. The IETF timeline follows:

RFC 1883,2460 - IPv6 Specification
RFC 1885,4443 - ICMPv6 Internet control message protocol
RFC 3142 - IPv6-to-IPv4 translation
RFC 3315,4580,4649,4704 - DHCPv6 Dynamic, automatic address assignment
RFC 4861 - Neighbor Discovery
RFC 4862 - Stateless Addr Autoconf
RFC 4944 - IPv6 over IEEE 802.15.4 (6LowPAN) 

Drafts: HYDRO routing (part of ROLL [routing over low-power, lossy links] effort)

Papers: IP is dead, long live IP,  Extended Internet Architecture PhD Thesis by Jonathan Hui

---

Why is it cool?

IPv6 running on motes is cool because it really leverages what IPv6 was designed for -- ubiquitous computing.  Imagine a day when all of your appliances and consumer electronics will be able to talk to each other and provide you real time data on their energy usage, health, etc.  The ZigBee alliance has recently signed up to define a specification for an IPv6 stack in addition to an RF4CE stack for remote controls and consumer electronics.  Similar to how WiFi is integrated into all sorts of products today and just works, ZigBee may make it so cheap, tiny devices of the future can provide direct IPv6 connectivity over low-power, low-bandwidth radios.

---

What is the status of BLIP?  When will it be released?

BLIP is a work in progress.  It is currently fully supported on the TelosB platform and works on MICAz when compiled in a memory-constrained mode.  It is being folded into the TinyOS 2.x core with a slated release date of late August 2009.  The version in contrib/berkeley/blip is the correct one to use, however, as that one will actually build without manually adding radio stack modifications that are still being negotiated.  IRIS support is in the works as well with the initial port being done by European researchers Miklos Maroti and Lars Schor.  An improved release candidate of BLIP is slated to be pushed into contrib as early as next week.

---

Where can the BLIP source code be found?  How do you use it?

1) Download Xubuntos 2.1 VMware image (Howto)
2) Start the VM, login as:
  username: xubuntos
  password: tinyos
3) Start a Terminal
4) Prepare your VM to run BLIP as follows:

- Install IPv6 tools:

    sudo apt-get install netcat6

- Update tinyos-2.x trees from CVS:

    cd /opt
    # hit return for anonymous password
    cvs -d:pserver:anonymous@tinyos.cvs.sourceforge.net:/cvsroot/tinyos login
    cvs -z3 -d:pserver:anonymous@tinyos.cvs.sourceforge.net:/cvsroot/tinyos co -P tinyos-2.x
    cvs -z3 -d:pserver:anonymous@tinyos.cvs.sourceforge.net:/cvsroot/tinyos co -P tinyos-2.x-contrib/berkeley

- Add a simple environment setup script

cd /opt/tinyos-2.x-contrib/berkeley/blip
cat <<-EOF > setenv
export TOSROOT=/opt/tinyos-2.x
export TOSDIR=/opt/tinyos-2.x/tos
export LOWPAN_ROOT=$PWD
export TOSMAKE_PATH="$LOWPAN_ROOT/support/make"
EOF

- Build the driver

    cd /opt/tinyos-2.x/support/sdk/c/sf
    ./bootstrap
    ./configure
    make
    cd /opt/tinyos-2.x-contrib/berkeley/blip/support/sdk/c/blip
    make

- Patch motelist to handle mib520 for micaz discovery

cd ~
cat <<-EOF > motelist-linux.mib520.patch
--- motelist-linux	2006-12-12 10:23:01.000000000 -0800
+++ /usr/bin/motelist	2009-05-19 11:28:26.000000000 -0700
@@ -61,7 +61,10 @@ sub scan_sysfs {
 
 # Scan /sys/bus/usb/drivers/usb for FTDI devices
 my @ftdidevs =
- grep { (\$_->{UsbVendor}||"") eq "0403" && (\$_->{UsbProduct}||"") eq "6001" }
+ grep { (\$_->{UsbVendor}||"") eq "0403" && 
+ (((\$_->{UsbProduct}||"") eq "6001") || 
+ ((\$_->{UsbProduct}||"") eq "6010")) 
+ }
 map { {
 SysPath => \$_,
 UsbVendor => snarf("\$_/idVendor",1),
EOF
cd /usr/bin
sudo patch -p0 < motelist-linux.mib520.patch

- Download Blip.micaz.patch

 - Patch the blip contrib sources to add automatic micaz support
and fix some build issues.

    cd /opt/tinyos-2.x-contrib/berkeley/blip
    patch -p0 < ~/blip.micaz.patch

5) Use your prepared VM to build and deploy BLIP:

- Enable the BLIP build environment:

    cd /opt/tinyos-2.x-contrib/berkeley/blip
    source setenv

- Build the UDPEcho app and base station for telosb and micaz:

    cd /opt/tinyos-2.x-contrib/berkeley/blip/apps/UDPEcho
    make telosb blip
    make micaz blip

    cd /opt/tinyos-2.x-contrib/berkeley/blip/apps/IPBaseStation
    make blip telosb
    make blip micaz

- Connect a TelosB via USB, and flash it with the base station code
(Install FTDI drivers if needed)
(Accept TelosB device when dialog appears)
(Right click USB device in lower right of VM and select connect)

    motelist # find ttyUSB port to use
    cd /opt/tinyos-2.x-contrib/berkeley/blip/apps/IPBaseStation
    make blip telosb install,64 bsl,/dev/ttyUSB0

- Connect a MicaZ via USB, and flash it with the remote node code
  (Install FTDI drivers if needed)
  (Accept MIB520 device when dialog appears)
  (Right click USB device in lower right of VM and select connect)

 	 
    motelist # find ttyUSB port to use
    cd /opt/tinyos-2.x-contrib/berkeley/blip/apps/UDPEcho
    make blip micaz install,1 mib520,/dev/ttyUSB0

6) Fire up Linux network driver to communicate with BLIP network:

- Start the ip-driver

    cd /opt/tinyos-2.x-contrib/berkeley/blip/support/sdk/c/blip
    sudo ./ip-driver /dev/ttyUSB0 telosb
    # password: tinyos	 
    # blip console commands:
    # blip:xubuntos-tinyos> help
    # blip:xubuntos-tinyos> log WARN
    # blip:xubuntos-tinyos> routes	

7) Use standard IPv6 tools to access the remote BLIP nodes:

    # Ping - base station and remote node
    ping6 2001:470:1f04:56d::64
    ping6 2001:470:1f04:56d::1

    # Access shell on remote node
    nc6 2001:470:1f04:56d::1

Note that BLIP ships with support for pinging a node with standard the ping6 tool, shelling into a node with netcat (the shell is a custom one, not ssh, type help to see available commands), and over-the-air reprogramming of nodes with a deluge-like interface.  BLIP is an exciting software development for the TinyOS community and users of TelosB, MICAz, and soon IRIS platforms.  We encourage you to try it and track its rapid development.

Martin Turon is Crossbow's Director of Wireless Software. Not only an expert in the field of wireless sensor networks, Martin has been instrumental in simplifying the WSN user experience with advancements in interface and server tools using his background in video game design, mobile phone software and operating systems. He is the current Chair of the ZigBee WSN group which is working to establish the standard for low-power routing while leading the Wireless software development team at Crossbow for future product enhancement. Martin obtained degrees from University of California, Berkeley in Electrical Engineering and Computer Science. He has also studied Artificial Intelligence at University of California, Los Angeles and received a certificate in Math for Financial Engineering from Haas Business School. Martin is an avid lover of indie rock and performs with various ad-hoc musical projects.

Extending Our Senses into the Physical World

The picture of a future with wireless sensor networks-webs of sensory devices that function without a central infrastructure--is quickly coming into sharper focus through the work of Los Alamos National Laboratory computer scientist Sami Ayyorgun. Using Crossbow's TelosB Motes in their research, proponents of this new technology see a world with deployments to improve a wide range of operations.

Engineers could wirelessly monitor miles of gas and oil pipelines stretching across arid land for ruptures, damage, and tampering. Rescue workers might detect signs of life under the rubble of a collapsed building after an earthquake, thanks to a network of sensors inside the structure. Armed forces could keep an eye on a combat zone or a vast international border via a sensor network that could promptly provide alerts of any intrusion or illicit trafficking.

"It's not easy to envision the impacts that sensor networks will make, both socially and economically," Ayyorgun said. "Like many other researchers, I think they are likely to rival the impact that the Internet has made on our lives."

Ayyrogun has developed a new communication scheme that brings the reality of these and other applications a step closer. He has shown for the first time that concurrent gains in many measures of performance are possible, including connectivity, energy, delay, throughput, system longevity, coverage, and security.

In recognition of the multifaceted improvements Ayyorgun's research makes on state-of-the-art technology in this field, his recent paper, "Towards a Self-organizing Stochastic-Communications Paradigm for Wireless Ad-hoc/Sensor Networks," has been nominated for the Best-Paper Award from a pool of more than 250 manuscripts at the International Conference on Mobile Ad-hoc and Sensor Systems (MASS) of the Institute of Electrical and Electronics Engineers (IEEE). Ayyorgun will present the paper at this prestigious meeting of the IEEE beginning September 29, in Atlanta, Georgia.

Like cell phones, wireless sensor networks depend on small, independently powered devices, often called motes, to communicate. But unlike cell phones, which always relay their signal through a base station such as a tower, multihop sensor motes use each other to relay signals, transmitting communiqués through a series of "hops" from one mote to the next. Without the need to build a mesh of base stations that must be wired or have a substantial supply of energy, creating information-bearing ad-hoc networks to suit each unique set of circumstances would significantly reduce costs.

"Wiring or 'beefing up' system resources is expensive and is often not feasible for many applications," Ayyorgun said, calling that a "major impetus" for wireless network research. But with nearly all motes dependent on a portable source of power like a battery, it is important that the devices be as energy efficient as possible. "Energy efficiency is a first-class design criterion," he said.

And energy utilization isn't the only consideration. Other performance aspects of concern include the system's connectivity; the delay, or time it takes for data to be transported; the throughput, which measures the amount of data the system can handle at once; and network security, to name a few. Many solutions aimed at advancing wireless sensor networks have managed to improve performance over at most a few metrics at the expense of others. Ayyorgun analogizes the conundrum to a Rubik's cube, the cube-shaped toy in which the aim is to match each of the six sides with one distinct color. Often, gains in one aspect of wireless sensor network performance such as energy efficiency have only been achieved with losses in another area, such as the end-to-end delay.

With Ayyorgun's scheme, however, "all of the colors have started to match," he said. The sensor network was more energy efficient with shorter delay times, and the other performance considerations mentioned earlier have all improved as well.  "The motes communicate randomly, but their random behavior-their genetic code, if you will-has collective intelligence by design," he said. That collective intelligence results in the concurrent performance gains over many aspects, he added.

"We have good colors on all sides, but it's not perfect yet," Ayyorgun said, emphasizing that wireless sensor networks are still in the development stage. Many issues remain to be addressed, just as we are beginning to realize the potential of these "networks of the future."

Ayyorgun acknowledges the support of the Laboratory Directed Research and Development Office at Los Alamos, the Los Alamos Engineering Institute, the Center for Nonlinear Studies, and colleagues, as well as his students.

Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, The Babcock & Wilcox Company, and Washington Group International for the Department of Energy's National Nuclear Security Administration.

Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health, and global security concerns.

The latest buzz...

If you are looking for ways to expand the capabilities of your Mote deployment, there's a new sensor you should look into - introducing the new BumbleBee Radar! The BumbleBee is a coherent, pulsed Doppler radar offering rich information at a strikingly low price. Introduced in mid-April by The Samraksh Company, the radar ships ready for use with Crossbow's TelosB Motes.

 

Being a pulsed Doppler radar, the BumbleBee measures radial velocity directly. Because it is coherent, you can determine the sign of the velocity and measure the time structure of relative motion very precisely, even for small motions! Range is not measured directly, but in some contexts you can infer range from motion information.

The BumbleBee produces phase information directly resulting in motion information with a resolution of a fraction of a wavelength (i.e. fractions of a centimeter of displacement) which is an order of magnitude finer than if the radar were non-coherent. This information can be received at a rate of ~300 complex (i.e. real and imaginary pairs) samples per second. This capability opens up opportunities for original research and development in diverse signal processing applications.

BumbleBee's sensitivity is optimized for the normal day-to-day movements of people which makes it a compelling choice for monitoring and classifying human activities in commercial and recreational settings. This device could be used to monitor the usage of urban playgrounds, public parks, employer provided recreational facilities, office conference rooms and waiting areas. Quantitative measurements of loitering, underuse, overuse and unauthorized use would provide an improved basis for setting policy, deciding layouts or evaluating security measures.

Other interesting applications include the classification of unique patterns of movement, such as dancing or fighting in nightclubs, exercising or falling in a retirement home, and even working or sitting around on a construction site. Automated detection of various activities would expedite response in abnormal situations and provide positive feedback in normal situations. Not all applications need to center on people of course! For example BumbleBee can be used to do non-contact wobble detection of rotating machinery in industrial settings, monitor livestock activity, even recognize rodents or snakes in remote parts of a building or an urban infrastructure!

The BumbleBee facilitates information rich applications without compromising on Mote-scale constraints. It uses less than 40 mW or total power, has a range of ~10m, and is form factor compatible with Motes. Most importantly, its technology facilitates a new cost paradigm that is more compatible at a system level with the use of large scale Mote networks. At $100 USD/each, price is its most innovative feature! For more information contact info@samraksh.com.

BumbleBee is patented, but a usage license is made available as part of the purchase price for research usage. The Samraksh Company also promises very reasonable terms for small and mid-scale industrial applications. The radar conforms to FCC regulations for operation within the ISM unlicensed band (at 5.8GHz). Non-research applications may need additional FCC certification.

Swarm Navigation with TelosB Motes

The concept introduced below provides a highly effective swarm navigation scheme that is of low complexity, robust, and highly scalable. Rather than using a few highly complex and expensive swarm agents to complete a mission, the group at Easysen believe in the advantages of large ultra-low complexity swarms that solve problems reliably through emergent behavior.

EasySen is a start-up company who in conjunction with the University of Notre Dame’s Mobile Sensing Systems (MOSES) Lab, has developed an autonomous sensor swarm that uses TelosB nodes for navigation of swarm agents. The principle is based on Zigbee radio beacon induced potential fields and provides an ultra low cost and complexity solution to mobile sensing for land, sea, and air vehicles. Stereo TelosB receivers and stereo sensor suites (EasySen SBT80 / SBT30-EDU) allow for rather elaborate task execution.

The group at EasySen proposed the use of radio frequency beacons to generate (switched) potential fields for navigation of large numbers of swarm agents. The idea is to use attractive beacons as waypoints and local attractors. Repelling beacons on each agent and waypoint are used to control the density of agents and avoid collisions.  If a certain sequence of waypoints defines a navigation path, then the attractive beacons need to be distinguishable and need to be visited in a certain sequence. (This is easily implemented in form of a finite state machine in each sensor swarm agent.) Repelling beacons are local and do not need to be distinguishable.  Individual sensor swarm agents are equipped with a side-looking stereo receiver with opposite directions of highest sensitivity. A simple difference between the left and the right Receive Signal Strength Intensity (RSSI) allows the agent to detect in which half space (relative to the center length axis of the vehicle) a beacon is located. One can then navigate towards a beacon by always moving towards the receiver side that has produced the stronger RSSI reading. For repelling beacons, one always moves towards the direction of the smaller RSSI signal.

The applications of this paradigm are many and range from environmental clean-up such as oil spill removal to surveillance and protection tasks. A ground vehicle swarm that performs a simple detection task is shown in the video below:

The company also produces readily usable plug-in surveillance sensor suites for the TelosB wireless 802.15.4 platform:

• The Wi-Eye, an ultra-sensitive sensor board that is capable of detecting the IR signature of moving vehicles from as far as hundreds of feet away.
• The SBT80 is an 8-modality sensing platform, ideal for sensor fusion applications.

Both sensor suites (the Wi-Eye and the SBT80) are prime candidates for perimeter security, traffic monitoring, tracking, and occupancy detection tasks, just to name a few. In addition, EasySen also offers SBT30-EDU, a low-price educational prototyping board that interfaces to external signal sources.  Click here for more information on the TelosB Mote platform.

ALARM-Net: Wireless Sensor Networks for Assisted Living and Residential Monitoring

Thanks to technology and advancements in medicine, people are living longer, and due to a change in the family unit many are living independently. This trend leads towards a growing elder population who have the desire to "age in place." With the high cost of nursing homes and related services, there is a significant need for more efficient and affordable home monitoring solutions. Today there are 35 million people over the age of 65, and by the year 2030 this number will grow to 70 million people based on data collected by the US Census Bureau. Only 4% currently reside somewhere other than their own home, with 90% of Americans, 60 years and older, wanting to remain in their own homes and communities as they age. Of this 90%, it has been determined that 75% of these adults have at least one chronic condition.

Researchers at the University of Virginia, Department of Computer Science have been developing a wireless sensor network for assisted-living and residential monitoring. ALARM-NET provides pervasive and adaptive health-care for continuous monitoring using environmental and wearable sensors. ALARM-NET is a wireless sensor network for smart healthcare. While preserving resident comfort and privacy, the network creates a continuous medical history. Unobtrusive area and environmental sensors combine with wearable interactive devices to evaluate the health of spaces and the people who inhabit them. Authorized care providers may monitor resident health and activity patterns, such as circadian rhythm changes, which may signify changes in healthcare needs. High costs of installation and retrofitting are avoided by using ad hoc, self-managing networks.

The AlarmNet architecture for smart healthcare possesses the essential elements of future medical applications such as integration with existing medical practices and technology, real-time, long-term monitoring, miniature, wearable sensors, and assistance to the elderly and chronic patients. It extends healthcare from the traditional clinic or hospital setting to assisted-living and retirement homes, enabling 'telecare' without the prohibitive costs of retrofitting existing structures. In AlarmNet, the WSN collects data according to a physician's specifications, removing some of the cognitive burden from the patient (who may suffer age-related memory decline) and providing a continuous record to assist diagnosis. Health-related tasks are also made easier for the patient, for example, medication reminders, object location, and emergency communication.The architecture is multi-tiered, with lightweight sensors, mobile components, and more powerful stationary devices. Sensors are heterogeneous, and all integrate into the network. Multiple patients and their resident family members are differentiated for sensing tasks and access privileges.

As researchers at UVA point out, wireless sensor networks are ideally suited as a foundation for smart healthcare in AlarmNet, due to these several inherent qualities:
Portability and unobtrusiveness. Small devices collect data and communicate wirelessly, operating with minimal patient input. They may be carried on the body or deeply embedded in the environment. Unobtrusiveness helps with patient acceptance and minimizes confounding measurement effects. Since monitoring is done in the living space, the patient travels less often, which is safer and more convenient.
Ease of deployment and scalability. Devices can be deployed in potentially large quantities with dramatically less complexity and cost compared to wired networks. Existing structures, particularly dilapidated ones, can be easily augmented with a WSN network whereas wired installations would be expensive and impractical. Devices are placed in the living space and turned on, self-organizing and calibrating automatically.
Real-time and always-on. Physiological and environmental data can be monitored continuously, allowing real-time response by emergency or healthcare workers. The data collected form a health journal, and are valuable for filling in gaps in the traditional patient history. Even though the network as a whole is always-on, individual sensors still must conserve energy through smart power management.
Reconfigurability and self-organization. Since there is no fixed installation, adding and removing sensors instantly reconfigures the network. Doctors may re-target the mission of the network as medical needs change. Sensors self-organize to form routing paths, collaborate on data processing, and establish hierarchies.

Researchers at UVA have adapted a low-cost sensor module that is capable of detecting motion and light intensity changes. The module also has a simple one-button and one-LED user interface for testing and diagnostics. The module is interfaced to a MicaZ wireless sensor node that processes the sensor data and forwards the information to the rest of the wireless network. The picture shows a MicaZ detached from its normal battery-pack and interfaced to the motion sensor (X-10 RF circuits were removed, making this a truly low-power sensor) via the 51-pin connector. A set of such modules (MotionMote) is used to track human presence and to monitor the lighting conditions in various locations of the living space. This activity data is used to maintain location context, and are fed to the back-end software.

AlarmNet has also implemented a wearable body network with MicaZ motes embedded in a jacket, which can record human activities and location using a 2-axis accelerometer and GPS. The components are shown (w/out jacket). The recorded activity data is uploaded subsequently through an access point for archival, from which past human activities and locations can be reconstructed. One mote is placed on the back so that the y-axis (either positive or negative) is always pointing downward. It may also possess GPS capability if the tracking aspect is to be used. The other two motes are placed one on each arm so that when the arm is in a vertical position pointing down, the y-axis (either positive or negative) also points down. A web-server interface has also been implemented to make some SQL requests of a DBMS through a localized user interface which is a user view for this sub-system. This module allows the user to query the data collected and identify various activities that the user performed in the past and his or her location information of the past.

SolarDust, a sensor board for Mica motes shown on the left was also designed to provide the mote's microprocessor with a UART interface to a bluetooth transceiver. This enables the body network to communicate with other commercially available sensor devices, as well as communicate with a resident's cell phone for emergency response! The backbone network connects traditional systems, such as PDAs, PCs, and databases, to the sensor network. It also connects discontiguous sensor nodes by a high-speed relay for efficient routing. The backbone may communicate wirelessly or may overlay onto an existing wired infrastructure. In a previous posting, we discussed the LCD interface board for the MicaZ that is suitable for wearable applications, called the SeeMote. It presents sensor readings, reminders and queries, and can accept rudimentary input from the wearer. It has a five-button interface and a Secure Digital flash memory expansion port.

A wireless sensor network solution like AlarmNet benefits both the healthcare providers and their patients. For the providers, an automatic monitoring system is valuable for many reasons as it frees humans from 24/7 physical monitoring, reducing labor costs and increasing efficiency. The wearable sensor devices can sense even small changes in vital signals that humans might overlook, such as heart rate and blood oxygen levels, boosting accuracy. The quick notification of these changes may save human lives, and the data collected from the wireless sensor network can be stored and integrated into a comprehensive health record of each patient, which helps physicians make more informed diagnoses. Eventually, the analyzing, diagnosis, treatment process may also be semi-automated, so a human physician can be assisted by an electronic physician.

Healthcare patients benefit from improved health as a result of faster diagnosis and treatment of diseases. Other quality-of-life issues, such as privacy, dignity, and convenience, are supported and enhanced by the ability to provide services in an environment more comfortable for the patient. Though 24/7 physical presence of caregivers is reduced, the patient is not isolated from contact with the outside world—an important component of mental health. Family members and the system itself become part of the healthcare team. Finally, memory aids and other patient-assistance services can restore some lost independence, while preserving safety.

This implementation of wireless sensor networks will enable us to create a world that can improve the quality of life for through continuous monitoring of those needing as 'Assisted Living and Residential Monitoring Network.'