Wireless embedded Internet aims at enabling IP functions in resource-limited
wireless embedded devices and connecting heterogenous wireless embedded ...
Networking Infrastructure of Wireless Embedded Internet [Extended Abstract] Song Han Yi-Hung Wei Aloysius K. Mok
Deji Chen Mark Nixon Eric Rotvold
Department of Computer Science University of Texas at Austin
Emerson Process Management
{deji.chen, mark.nixon, eric.rotvold}@emerson.com
{shan, yhwei, mok}@cs.utexas.edu 1. INTRODUCTION Wireless embedded Internet aims at enabling IP functions in resource-limited wireless embedded devices and connecting heterogenous wireless embedded networks to the Internet. The scale of wireless embedded Internet is estimated to be with trillions of devices and many interesting applications can be found in industrial and building automation, smart grid, and real-time environmental monitoring and forecasting. One of the promising features of wireless embedded Internet is that devices based on different wireless radio technologies, once they become IP-enabled and agree on the same application protocols, will be able to exchange information directly through the Internet. There are many design challenges to be addressed in building the wireless embedded Internet. These challenges include how to map IP datagrams to the services provided by resource-limited embedded networks; how to establish secured end-to-end communication between devices and how to simplify existing application protocols in the Internet to make them suitable for the wireless embedded Internet. In this work, taking WirelessHART as an example which is the first open wireless communication standard designed for process measurement and control applications, we describe our design and implementation of a prototype system which integrates WirelessHART networks into the Internet and support web-based monitoring and control services. We will also present some performance results of this system.
2. DESIGN AND IMPLEMENTATION Our infrastructure design involves enhancements on both the Gateway of the wireless embedded network and the devices. The Gateway functions as an edge router between the embedded devices and the Servers/Hosts in the Internet. To achieve this, we enhance the Gateway with two modules: a 6LoWPAN adaptation layer [2] and a 6to4 IP tunneling module. 1 The 6LoWPAN adaptation layer enables regular 1 We would like to acknowledge AwiaTech Corporation and Emerson Process Management for allowing us to use their 6LoWPAN and CoAP software.
IP messages be conveyed over bandwidth-limited wireless networks by header compression/decompression and fragmentation/reassembly; the 6to4 tunneling module helps set up an tunnel between the Gateway and the Internet Host to support IPv6 traffic in IPv4 networks. On the device side, taking WirelessHART stack as an example, with the existing transport layer and application layer unchanged, we built a slim IP stack on top of its network layer. The slim IP stack includes a 6LoWPAN adaptation layer and a Constrained Application Protocol (CoAP) [1] layer. IP packets will be compressed, fragmented and wrapped as the payload of normal WirelessHART packets and sent to the Gateway. These two upper layer stacks work together so that the enhanced stack can support both normal WirelessHART traffic and IP traffic simultaneously. In the design, since IP fragments are wrapped in the payload of WirelessHART packets, we keep the routing protocol employed in WirelessHART network unchanged. With this approach, intermediate devices on the route can be any preexisting devices thus it supports incremental deployment. On the other hand, we establish IPSec service between the edge routers and web servers. Inside each wireless embedded network, the original security mechanism is used for encryption and authentication with no changes.
3.
DEMONSTRATION
To prove the concept and validate our design on the wireless embedded Internet infrastructure, we built an experimental testbed. The prototype system includes a CoAP-HTTP server, an enhanced WirelessHART Gateway, and a WirelessHART network consisting of three regular devices and four IP-enabled devices which form a mesh topology. The CoAP-HTTP server and the Gateway are each assigned a static IP address and connected to the Internet. In the demo, we programmed all seven devices to publish WirelessHART messages to the Gateway every 4 seconds. In the meanwhile, all the IP-enabled devices are further configured to PUT their device information and sensor measurements through IP packets to the CoAP-HTTP server. Through web browser, authenticated users can not only access the device information and their measurements in a real-time manner but also can actively reconfigure the IP-enabled devices and define various rules for notifications and alerts.
4.
REFERENCES
[1] CoAP. datatracker.ietf.org/doc/draft-ietf-core-coap. [2] C. B. Zach Shelby. 6LoWPAN: The Wireless Embedded Internet. Wiley, 2010.
