[time-nuts] GSM/GPRS module timing accuracy

Tony tnuts at toneh.demon.co.uk
Tue Nov 11 17:34:54 EST 2014

On 11/11/2014 21:52, Tom Harris wrote:
> How are you getting time from the GSM network? If you are using the NITZ
> (look it up) service then you can use an unactivated SIM for free, but the
> accuracy is woeful, it can be seconds out.
I'm not at the moment; mobile phones do set their clocks from the 
network but I've no idea how accurately it can be done - which is why I 
was asking.
> Else you will have to have a live SIM and use NTP to a server. If you make
> any progress please post to the list. I have not heard of being able to
> access the clock in the tower over the network.
> The beauty of phone network is that it works in buildings, where GPS does
> not reach.
> Tom Harris <celephicus at gmail.com>

I would have a live SIM as the modem would be used periodically (but not 
necessarily frequently - perhaps every 24 hours or more) to send data. I 
would not want to use an NTP service as I would only have a 
micro-controller with limited memory.

Tony H

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