[Tinyos-devel] DutyCycle vs SleepInterval

[Miklos Maroti]

Hi!

I vote for sleep interval (less portable, but much more predictable)

Miklos

On Sat, Jan 10, 2009 at 2:56 AM, Razvan Musaloiu-E. <razvanm at cs.jhu.edu> wrote:
> Hi!
>
> The current LowPowerListening [1] interface contains two sets of
> commands: one using intervals expressing sleep intervals and another one
> using percentages expressing duty-cycles. What I would like to bring into
> discussion is the duty-cycles.
>
> For reference here is the interface:
>
>        interface LowPowerListening {
>          command void setLocalSleepInterval(uint16_t sleepIntervalMs);
>          command uint16_t getLocalSleepInterval();
>          command void setRxSleepInterval(message_t *msg, uint16_t sleepIntervalMs);
>          command uint16_t getRxSleepInterval(message_t *msg);
>
>          command void setLocalDutyCycle(uint16_t dutyCycle);
>          command uint16_t getLocalDutyCycle();
>          command void setRxDutyCycle(message_t *msg, uint16_t dutyCycle);
>          command uint16_t getRxDutyCycle(message_t *msg);
>
>          command uint16_t dutyCycleToSleepInterval(uint16_t dutyCycle);
>          command uint16_t sleepIntervalToDutyCycle(uint16_t sleepInterval);
>        }
>
>
> So for intervals we have 64K possible values. The duty cycles are
> expressed in 1/100 increments so for them we have 10000 possible values.
> For CC2420 these 10000 values actually corresponds only to about 650
> unique sleep intervals.
>
> Another issue is the fact that the duty-cycle is not guarantee. The
> current LPL doesn't track the achieved duty-cycle and dynamically adjust
> the sleep intervals in order to meet a certain one. What happens is a
> fixed sleep interval is picked by translating the duty-cycle to a sleep
> interval using a fixed knowledge about how much the probing should take.
> So basically the semantics is that that duty-cycle will be achieved only
> if there is no traffic and no false wakeups. I find this definition
> cumbersome and not very attractive to work with.
>
> So my questions are: what do people think about this? Do you usually use
> intervals or duty-cycles in your LPL applications? How does sliming down
> the LowPowerInterface to only 4 calls sound? :-)
>
> [1] http://tinyos.cvs.sourceforge.net/*checkout*/tinyos/tinyos-2.x/doc/html/tep105.html
>
> All the best!
> Razvan ME
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