Hello,
What the average data consumption for using A-GPS on the nRF9160 to download the Almanac and Ephemeris data? I would like to know how much data is billed through my carrier for performing this operation.
Regards,
Akash Patel
Hello,
What the average data consumption for using A-GPS on the nRF9160 to download the Almanac and Ephemeris data? I would like to know how much data is billed through my carrier for performing this operation.
Regards,
Akash Patel
Hi,
Exactly how much data is used depends on the protocol used, the data available, etc.
There was some numbers in the nRF91 Software roadmap from February:
(with SUPL, if I understood the powerpoint correctly):
- Cold start, All/most ephemeris/almanac data: 10s of kB
- Warm start, some ephemeris data: 1-10kB
- Hot start, no new data needed: 0B
Meanwhile, A-GPS through nRF Cloud was said to use ~4.5kB.
But you should be able to measure it yourself by using the %XCONNSTAT AT command.
Best regards,
Didrik
Hi,
Exactly how much data is used depends on the protocol used, the data available, etc.
There was some numbers in the nRF91 Software roadmap from February:
(with SUPL, if I understood the powerpoint correctly):
- Cold start, All/most ephemeris/almanac data: 10s of kB
- Warm start, some ephemeris data: 1-10kB
- Hot start, no new data needed: 0B
Meanwhile, A-GPS through nRF Cloud was said to use ~4.5kB.
But you should be able to measure it yourself by using the %XCONNSTAT AT command.
Best regards,
Didrik
Hi Didrik,
The nRF Cloud 4.5kB is for a cold start or warm start? What is it for the other?
Also, does that mean that nRF Cloud is not using SUPL? What is it using?
Regards,
Akash
Akash Patel said:Also, does that mean that nRF Cloud is not using SUPL? What is it using?
No, it is not using SUPL. According to the software roadmap, it is using a "packed binary format", which is sent over the MQTT connection that has already been established.
Akash Patel said:The nRF Cloud 4.5kB is for a cold start or warm start? What is it for the other?
I asked the application team if they had any more information. This is the answer I got:
Another developer on the apps team did some cold start tests with an nRF9160 Feather which is running the A-GPS sample and using a hologram.io SIM. Those tests showed 16.91kB data used:
Note that these numbers include all the data sent between the device and the cloud, including the TLS handshakes which uses ~10kB data.
Hi Didrik,
Looks like we are using this agps_write function to write the A-GPS data we have received to the modem before we switch to GPS mode. When we write the almanac/ephemeris data to the modem, is that get erased when we do a power cycle?
From my understanding the almanac data should be valid for a several weeks and the ephemeris data should be valid for up to 2 hours. So essentially, If I write this A-GPS data, use GPS for 5 minutes, power cycle, turn on GPS again, will I have to rewrite the A-GPS data or the GPS will be able to perform a hot start?
Regards,
Akash
Akash Patel said:If I write this A-GPS data, use GPS for 5 minutes, power cycle, turn on GPS again, will I have to rewrite the A-GPS data or the GPS will be able to perform a hot start?
Yes, I believe that is the case.
However, if you turn the modem off gracefully with AT+CFUN=0, it should store the data to non-volatile memory so that you would not have to fetch it all again after a power cycle.
Although there is still information that has to be fetched each time, such as time, approximate location, etc.