Roaming implications on power usage

[Thomas]

Hi,

We are doing an analysis of power usage using a roaming sim vs home sim since the roaming sim data charges tend to be cheaper. (You wouldn't have happened to have done a similar analysis already would you?)

We know that the nrf9160 must initially scan all bands for a home network before selecting a roaming network, and that from then onwards it caches that information and can register within seconds to the roaming network from then onwards.

My question is, how frequently does the nrf9160 do another full band scan in search of a home network, if ever? Does it only do another full band scan if the roaming network it was connecting to is lost?

Kind regards,

Thomas

[Håkon Alseth]

Hi,

 

My question is, how frequently does the nrf9160 do another full band scan in search of a home network, if ever? Does it only do another full band scan if the roaming network it was connecting to is lost?

The period of the higher priority PLMN search is read out from the SIM card. The minimum is 2 hours, as per 3gpp 23.122 chapter 4.4.3.3.1.

This is a search that can occur while you're connected to a roaming network, but only when the link is idle.

 

However, the same chapter also mentions:

periodic attempts may be postponed while the MS is in power saving mode (PSM) (see 3GPP TS 23.682 [27A]).

Meaning that you will not see such a search while in PSM.

 

My question is, how frequently does the nrf9160 do another full band scan in search of a home network, if ever?

This depends on what values are programmed into your SIM card. Min. 2 hours, but only if the link is idle (for instance in eDRX/RRC idle etc)

Does it only do another full band scan if the roaming network it was connecting to is lost?

It can do this if the lte link is in an idle mode (ie. not currently in PSM), but only in the intervals that are read out from the SIM.

This also depends on your power profile settings, for instance what's set in this AT command:

https://infocenter.nordicsemi.com/topic/ref_at_commands/REF/at_commands/mob_termination_ctrl_status/xdataprfl_set.html?cp=2_1_4_13_0

 

Kind regards,

Håkon

[Thomas]

Thanks Håkon, this was very helpful.