Re: [core] sleepy to sleepy communication I-Ds

[Jari Arkko <[e-mail]>]

Angelo,

> Indeed sensor networks support sleeping using radio duty cycling at
> lower layers, this turns out in having the sleeping functionality
> without any loss of communication at the upper layers.
>

We discussed this a couple of IETFs back. Since then I've been doing some talking to our researchers who measure and improve power usage in radios.

First, duty cycling is already pretty widely used for radio technology. All cellular systems, for instance, turn off the radio except in during the time they listen for possible incoming paging signals, system information necessary to stay in contact at all, or when they have been granted a time slot to send.

Secondly and more importantly, per their measurements, even after all the above techniques, periodic listening for possibly incoming messages is the biggest consumer of energy in applications where we'd like to have a long battery life, such as in sensors. That power usage dwarfs everything else, so it has to come down, somehow, to make an improvement.

So if we want to achieve significantly longer battery lifetimes (and I claim we need those) we need to change some things. Obviously a lot of the link layers can be tuned better, implementing simply longer paging frequencies, for instance. My hypothesis is that we'll have to go longer than what typical application protocol timeouts are today, so the change would be something that is visible to applications. We could change some of the timeouts, but it is not clear that network buffers and all underlying mechanisms deployed today support those without changes. And in general, I think it is better to fit the communication model to the problem at hand than vice versa. As a result, I personally believe that we need to build applications that natively communicate in ways that make sleep modes easy. Such as publish-subscribe instead of direct request-response from anyone who needs the information. But like I said, this is a hypothesis and I'd love to be proven wrong.

Jari