[Tinyos-devel] Re: [Tinyos Core WG] time sync interfaces

[Philip Levis]

On Dec 18, 2007, at 3:27 PM, Omprakash Gnawali wrote:

> In what cases is a few-millisecond time synchronization useful? An
> application that does occasional temperature and light sensing
> probably can just use the time of arrival at the base station as time.
> Phil, is this the class of application you were thinking of when you
> said 90% cases?

I'm thinking of low-rate sensing apps which store/queue readings,  
rather than always send them immediately. I'm thinking of apps which  
need synchronized, periodic samples. I'm thinking of logging software  
events in the network for management. I'm thinking of intruder  
detection (e.g., passive IR). Note that once you have low power  
listening going, especially with a long check interval, a packet can  
have reasonable delay.

Given that most TinyOS systems expect millisecond granularity timing  
(TimerMilliC), extending this to the default HIL timesync seems  
reasonable. Note that we can always have *more* HILs that have more  
precise time sync, if evidence indicates such is reasonable.

Phil