The Internet Engineering Task Force has kicked off a standards effort to provide one of the missing puzzle pieces for wireless sensor networks. Aiming to define a spec for Internet Protocol as early as next summer, the IETF's Routing over Low-power and Lossy Networks (Roll) group is pursuing a standard way for control and sensor nodes on Bluetooth, Wi-Fi and 802.15.4 nets to link to the broader Internet.
Today's sensor networks employ multiple technologies serving a variety of industries, some of which are battling to define the next phase of embedded Internet.
"There has been an explosion of proprietary protocols for sensor networks in the last five years," said Jean-Philippe Vasseur, a distinguished engineer in the corporate technology group at Cisco Systems who will co-chair the Roll effort. "When each one aims to become an ad hoc standard, you wind up with a model of many translation gateways, leading to a complex and expensive architecture that doesn't scale."
"Having Cisco place its focus behind Roll is interesting, as that company has the ability to influence a large number of IP-based applications," said George West, president and senior analyst at West Technology Research Solutions (Mountain View, Calif.). The effort could also let developers tap into the wealth of tools for IP nets, West said.
Thus far, about 250 people have signed up on the group's e-mail reflector to work on the standard. They include staffers from such companies as France Telecom, Intel, Sun Microsystems and home automation specialist Zensys. More than 100 turned out for the group's first meeting, held in late March.
The Roll effort will assess requirements in sensor nets for use in home and industrial automation as well as in urban settings. It is building on the work of the IETF 6LoWPAN group (RFC 4944), which has specified use of IPv6 over low-power wireless nets.
"There are thousands and thousands of sensor networks in place in cars and buildings today, but most do not use IP," said Vasseur. "What we are trying to do is create a way these sensors can talk to each other without needing a proprietary translation gateway."
The group could pick or extend an existing protocol before it wraps up its efforts in June 2009. If it does not find anything suitable, it could be rechartered to create a protocol--a process that could take an additional 18 months.
"Arch Rock has been shipping IP routing over 802.15.4 for a year now, so I would say we are the furthest along in this area," said David Culler, a sensor network pioneer who is co-founder and chief technology officer of startup Arch Rock and co-chairman of Roll.
A number of other researchers are working on IP-based routing protocols for sensor networks.
"Sun has done some work in this area, as have others in Korea, Finland and elsewhere in Europe," said Culler, who is also a professor of computer science at the University of California at Berkeley. "Not all of them are public yet. Some are academic, while others are commercial."
For its part, Cisco has no wireless sensor network products to date, but it is keen on making sure the sector adopts the same IP-based standards as are used in the business communications networks it serves, said Vasseur.
Roll also will look to set a security standard for its routing protocol. And it is taking into account scenarios that support "structured mobility," such as the need to move machines around on a factory floor.
"There's an assumption in our work that supported devices are not moving all the time," said Culler.
Brick in the wall
The routing effort is just one of many pending standards that could smooth the way for wireless sensor networks.
For example, at the application layer, new XML schemas for sensor nets may be helpful, Culler said. At the transport level, the 802.15.4 technology is key, but a 15.4e standard for multi-hop nets is still in progress.
More broadly, several industries are attempting to set their own standards for wireless sensor nets. The 30,000-member ISA trade group, focused on factory automation, hopes to set a sensor net standard for process control this year.
"There are a lot of protocols out there, so it becomes a question of who will win, and it's too early to tell," said Mareca Hatler, who follows sensor nets as director of research at market watcher ON World Inc. "Today it's being defined more by the automation and control sectors and less by the PC data side, but that could change."
"Having some broad standards that are applicable across a number of application areas is one of the keys to accelerating adoption," said analyst West. He noted that some ad hoc standards in industrial control, as well as new profiles for energy management and home control emerging from the ZigBee Alliance, are gaining traction.
While many wireless sensor nets are based on IEEE 802.15.4 networks, some see low-power versions of Wi-Fi having a play. "It's another wrinkle that says a lot about the attraction of Wi-Fi," said Hatler. "They are way behind 15.4, which is where all the standards efforts are focused right now, but they could find appeal in industrial apps that typically need more bandwidth or in homes that already use Wi-Fi data networks."
GainSpan Corp. (Los Gatos) is one of at least two startups pursuing Wi-Fi sensor nets. The company developed a Wi-Fi chip that can be directly attached to batteries drawing as little as 1 to 5 microamps in standby mode, depending on the voltage level of the battery (1.2 to 3.6 V). The chip jumps to active mode in just 6 milliseconds.
Vijay Parmar, chief executive of GainSpan, estimates there is a market for low-power Wi-Fi parts in sensor nets and other embedded uses that could hit 3 million nodes this year and as many as 10 million next year. The IEEE 802.11 group has yet to kick off any standards efforts for low-power Wi-Fi. But Parmar said he is talking to customers about an effort that could be hosted by the Wi-Fi Alliance.
Separately, 802.11s work on a mesh networking standard for Wi-Fi, seen as a possible enabler for sensor nets, has gotten bogged down. Only 60 percent of the working group members approved a version 2.0 spec--which ran to some 140 pages--in a vote that closed May 3. That tally fell short of the 75 percent approval required.
Slow-moving battery technology is another limiting factor for sensor nets. Battery size typically determines the lifetime and the size of a sensor node, Culler said.
"Process measurement applications need a long [multiyear] unattended operation and thus long battery life," said Harry Forbes, a senior analyst at the ARC Advisory Group (Dedham, Mass.), who follows trends in sensor networks.
High node counts
"The need for improved ease of use and extended power lifetimes is becoming more important now that we are seeing more deployments with 1,000 or more nodes," said ON World's Hatler.
Hurdles aside, market watchers see significant uptake for sensor nets across a broad range of markets.
"When we first started doing research in 2002, every sensor networking vendor focused on all the markets," said Hatler. "Today the markets are more distinct, with vendors starting to focus on specific ones."
ON World projects the market for sensor nets and associated services in industrial applications could grow to $4.6 billion by 2011. Total revenues for uses in commercial buildings could grow to $2.6 billion by that time, and the market for sensors as part of smart utility meters could rise to $1.6 billion, Hatler said.
Forbes of the ARC Advisory Group is much more conservative. He estimates that the market for sensor nets in process manufacturing uses across industries such as oil and gas, food, pharmaceuticals and chemicals will grow from the present range of $10 million to $50 million to hit the hundreds of millions by 2012.
West Technology, which specializes in market research in wireless technology, forecasts that sales of chip sets for 802.15.4 sensor nets will rise from 31 million units this year to 312 million in 2012, growing at a compound annual rate slightly above 100 percent.
"There's no question sensor nets are happening, but where it takes off is always clearest in hindsight," said Culler of Arch Rock. "I've been working in this area for more than a decade, and all the pieces are now lining up and starting to come together."