Culler is a distinguished researcher in the field of wireless sensor networks. He said that if we can push the IP protocol into the sensor architecture, then most of the future Internet traffic growth may come from the sensor network. "We have been researching this problem for ten years, and we have walked about halfway." He has participated in the development of TInyOS, and the operating system is helpful for the creation of this field.
However, it is not easy to make the Internet protocol work at the sensor architecture level, because the battery budget of some sensor networks is about one hour in a year, Culler pointed out during the keynote speech at the IEEE Secon conference.
"Therefore, the sensor node almost has to be in sleep mode most of the time, but we assume that the IP network needs to work all the time." He said, "The sensor node is offline about 99.5% of the time, which means it must be in the remaining Work very, very well 0.5% of the time. "
Engineers need to abandon certain concepts of wired Internet design, such as letting each node remember complex routing tables and carefully confirm each transmission. "In a 1000-node network, if I let a node go online and say 'Hello', and each node confirms receipt, then we will all crash." He explained vividly.
Researchers have been experimenting with some architectures (such as TInyOS) for ten years. The original idea was to follow the concept of wired networking, such as the use of a layered software stack that assigns an address to each node, but this approach cannot meet wireless sensor networks with weak processing power and a small power budget.
"We went in the wrong direction." Culler said that he showed you a complete IPv6 stack suitable for existing sensor nodes. "The stack is feasible in terms of reliability and power."
Culler is one of the founders of Arch Rock, a startup that can already provide IP-based wireless sensor networks. He is also the co-chairman of the Internet Engineering Task Force (IETF), presiding over the definition of a software layer that uses the IEEE 802.15.4 radio frequency protocol to convert IPv6 routing mechanisms to sensor networks. The IETF's work is based on the 6LoWPAN network already established by the task force.
Although the research work on IP sensor networks continues to move forward, many people in the field still disagree about which network (802.15.4, Wi-Fi, or other networks) is the best way to achieve transmission. In addition, there are also differences in networking methods (routing networking and grid networking).
"The industry is still arguing about the way of networking." Culler said, saying that new routing protocols and grid protocols are still emerging, and no one knows the correct way of grid networking.
The Secon meeting conducted a one-day discussion around Wi-Fi mesh networking, during which three Wi-Fi mesh product manufacturers conducted product demonstrations, which involved a variety of applications ranging from public safety to low-cost Web access.
Although much work has been done and the completion of the standard has been delayed, the IEEE 802.11s standard for Wi-Fi mesh networking currently has much work to do.
Jorjeta Jetcheva, a system architect and .11s standard maker at FireTIde in California, said that there are many reasons for the delay of the standard, including some unresolved problems in wireless security, and it is difficult for a group to define the concept of routing , Because they cannot discuss the network layer according to the IEEE charter.
An Intel researcher pointed out that the Wi-Fi grid can open up new categories of applications. For example, Time Warner is working with router manufacturer FON Wireless to create a neighborhood network based on the Wi-Fi grid. The startups Mushroom Networks (San Diego) and WiBoost (Seattle) are also working on new peer-to-peer applications that use Wi-Fi mesh.
Most of Secon ’s themes focused on software issues. Culler mentioned major advances in flash memory, controllers, radio frequency and silicon-based sensors. But he said that for sensor networks, the changing software has further hindered the progress of basic chips to a certain extent.
For example, the firmware abstraction created by RF chip manufacturers to simplify programming actually restricts programmers from optimizing validation schemes. In addition, the popular TI Chipcon 2420 RF chip loses its configuration data after shutdown, which causes engineers to copy the channel information to the device when they restart.
"There are a lot of work that can be done at a lower level." Culler said, "Hardware designers still do not have a stable software layer as a design reference, and our software developers have not provided them with much help."
Figure 1: A latest version of the sensor network designed by the University of California, Berkeley, includes an 802.15.4 RF based on TI Chipcon 2420.
Author: Merina
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