R: R: Need info on AGPS

[Michele Manzato]

> One thing that we should look into is to have something like 
> an RSS Feed of that data, which can be downloaded everytime 
> we have a cheap (bluetooth, usbnet) IP connectivity. Then 
> cache all that data locally.

As far as I understand: GPS ephemeris cannot be really "cached" in the Neo
given their unpredictable nature. If they are valid for just 2 hours, then
the Neo MUST get the new ephemeris every 2 hours to keep AGPS alive.

So, either the Neo is in network range (USB cable or via the Bluetooth
bridge, until we have WiFi) or there is no other choice and download them
via GPRS.

Please correct me if I am wrong!

Bye
Michele

-----Messaggio originale-----
Da: Harald Welte [mailto:laforge at openmoko.org] 
Inviato: giovedì 25 gennaio 2007 17.51
A: Marcus Bauer
Cc: Michele Manzato; community at lists.openmoko.org
Oggetto: Re: R: Need info on AGPS

On Thu, Jan 25, 2007 at 05:12:09PM +0100, Marcus Bauer wrote:
> On Thu, 2007-01-25 at 16:24 +0100, Harald Welte wrote:
> 
> > > 3. A-GPS involves additional data traffic and thus (potential) 
> > > additional costs. Does it use a normal GSM/GPRS IP-based data 
> > > transfer? does it use some out-of-band GSM/GPRS control messages? 
> > > or does it get data from broadcasts in the local cell (e.g. GSM
cell-broadcast)?
> > 
> > AFAIK: GPRS.  so its up to you whether you want that extra traffic 
> > (and cost, unless you're flat) or not.
> 
> The Global Locate docs state TCP/IP as one possible way. So via 
> USB-network or BT should be possible too.

What do you think do we run on top of usbnet and bluetooth BNEP ? The answer
is: TCP/IP ;)

So anything that uses TCP/IP and can be attached to the phone will be able
to connect the AGPS server[s].

> You need it only once for the first fix. It is ~2KB for all satellites 
> and valid for 2-4 hours. Precomputed for a week maybe 1MB.

One thing that we should look into is to have something like an RSS Feed of
that data, which can be downloaded everytime we have a cheap (bluetooth,
usbnet) IP connectivity. Then cache all that data locally.

-- 
- Harald Welte <laforge at openmoko.org>          	        http://openmoko.org/
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