[Tinyos-users] Re: [Tinyos-help] Synchronized timing in TOSSIM

[Yogesh Iyer]

Hi Mads,

 

Thanks for the reply. I know the methods I am talking does not reflect real-life scenarios. But there are several algorithms for achieving time synchronization in sensor networks, so I am not really concerned how the network achieves it. The user can implement any algorithm for that purpose.

 

Moreover, I do not have the motes to actually implement my algorithm. So, I would only be simulating it on TinyViz. Hence, instead of implementing any algorithm for time sync in my simulations, I was wondering if I can achieve that in a simpler manner.

 

I would like to time-stamp my outgoing packets at the Transport layer and this is why I was figuring out ways to do that.

 

One more way to achieve that is to make the nodes get the system clock value. Is that what you meant by: "TOSSIM time (which I assume is easily accesible on the PC side)". I am not sure how do I get that value, so can you please guide me.

 

Thanks,

Yogesh.

Mads Bondo Dydensborg <[EMAIL PROTECTED]> wrote:

On Sat, 4 Dec 2004, Yogesh Iyer wrote:

> Hi,
> I am implementing an network layer algorithm using TOSSIM and
> synchronized timing is one of the essentials for this algorithm. I saw a
> link for "Timing Synchronization in Sensor Networks"
> (http://www.ee.ucla.edu/~saurabh/time_synchronization/). As per my
> understanding, this time sync algorithm uses the MAC layer to time-stamp
> the data. I want to keep my n/w layer as generic as possible and not
> depend on any lower layers.

If you want to timestamp you outgoing or incoming packets, _above_ the mac
layer, you kind-of need to know a lot about the mac layer then, e.g. how
long it takes your packet to get through it.

> Is there any other way of achieving synchronized timing in the network.
> I just want to run my simulations on TinyViz, so I was wondering if it
> would be possible to have 1 node (Base Station) have a specific clock
> and then all the other sensor nodes read this value from the Base
> station on bootup.

What would be the point of that, exactly?

> Or else have a separate data structure for the clock value and have it
> as a global value to all the nodes so that they have the same clock
> value.

In that case, you would be simulating a situation that does not really
reflect real-life, wouldn't you? Unless you are planning on putting a GPS
or similar on all your sensors, and get the time from them. If that is the
case, you can implement a Time component, that is the interface to your
hardware when compiling for your platform, and otherwise return the TOSSIM
time (which I assume is easily accesible on the PC side).


>
> Or is there any better way? It will be really helpful if you can post your opinions. Thanks.
If you require exact synchronization and do not have access to special
hardware, get the time from the radio/mac layers, I would think.

Mads

--
+----------------------------------------------------------------------+
| Mads Bondo Dydensborg. http://www.distlab.dk/madsdyd/ |
| +45 35 32 14 18 |
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