Adam Dunkel's and the guys at SICS just committed the Chameleon code for Contiki's wireless sensor networking stack. Chameleon rides underneath Rime and is a header abstraction layer which can interface to different MAC/PHY protocols. For those of you that don't know Rime, its a refreshingly simple and small wireless sensor networking protocol stack . Anyone that's looked through the code can see that its thinly layered and easy to follow. The core of the stack does simple transmit and receive, but there are also source code modules for mesh routing, reliable transmission, broadcast, and more. The stack is part of the Contiki OS download along with the uIP stack.

According to Adam and his group at SICS , Rime and Chameleon can be used as an abstraction to make it easier to implement wireless sensor network protocols. The full abstraction consists of three parts:

1. The networking protocols that run on top of the Rime stack
2. The Rime stack: Rime implements a set of "communication primitives" which are basically communications building blocks (stubborn unicast, reliable unicast, multi-hop unicast, local broadcast, multi-hop broadcast).
3. Chameleon: A header abstraction layer which takes the Rime header and transforms it into a header format that is compatible with the mechanism that will be used to transport the data(802.15.4, UDP/IP, proprietary).

With the initial publishing of the Chameleon code, it looks like the initial version of the full suite is on its way.   

To understand how this would apply to something like, say Zigbee, I suspect it would be as follows. Please understand that the example is based on my poor initial understanding, so its best to read the paper , see the slides , and talk to Adam and friends to get the most accurate picture.

Ex: A Zigbee implementation based on Rime/Chameleon.

The Zigbee layers actually stay completely the same. The difference is that instead of making calls to the MAC layer data service to send frames, you would make the calls to the Rime stack and vice versa. The Rime stack would then send the frames to Chameleon which would transform the headers based on the MAC that will be used. If 802.15.4 is used, then you won't get much benefit since this abstraction would just pose as another layer of complexity. However if you also want to use UDP/IP for transport, then the modification would just be to the header description in Chameleon. Or if you wanted to use a proprietary protocol based on the radio of your choice, but wanted to keep the same mesh networking, reliable transport, and application profiles that Zigbee has already implemented, then this would also just be a small change in the header description to Chameleon. 

I hope I haven't bastardized this explanation of Rime/Chameleon too much and if anyone is out there that is more familiar with this, please feel free to add in your $0.02 in the comments section or drop me an email.

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