The Internet of Things requires interoperability and lowpower consumption,but interoperability and lowpower consumption have thus far been mutually exclusive.
This paper outlines the challenges in attaining low power operation for the IPv6-based Internet of Things, how this affects interoperability, and what must be done to combine the two.
Research and standardization has come a long way towards providing efficient protocols and specifications for IPv6 for the Internet of Things. The efforts of the IETF 6lowpan and ROLL working groups and the the IPSO Alliance have resulted in protocols and interoperability testing frameworks for those protocols.
One recent result is the IETF RPL IPv6 routing protocol for low-power, lossy networks which was recently moved towards a standard RFC document. The first step towards interoperability for the Internet of Things was interoperability at the IPv6 layer. The second step is interoperability at the routing layer. The RPL protocol provides a framework for interoperable routing. Third was providing interoperability between two different operating systems, which was not without challenges.
The next step for interoperability is low-power interoperability. Existing protocols such as RPL are designed for running over radio layers such as IEEE 802.15.4 which are simpler and have a lower output power than radios such as WiFi and Bluetooth.
To attain a lifetime of years of batteries, however, the radio must be efficientlyduty cycled so that it is kept off for most of the time. But radio duty cycling creates a new set of dynamics for which existing protocols have not been designed. Existing interoperability experiments have not taken power consumption into account, but have been performed with an always-on radio layer.
However, Contiki provides a set of radio duty cycling mechanisms such as ContikiMAC XMAC , and LPP. By running micro IPv6 and Contiki RPL over ContikiMAC, we have been able to attain as low power consumption with IPv6/RPL as with specialized sensor network protocols such as Contiki Collect.
Our results show that the radio can be kept off more than 99% of the time while attaining full IPv6 communication, providing years of lifetime on batteries. But these low-power results have been achieved in a Contiki-only environment. Achieving full low power interoperability has yet to be done.
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