Howto "AT^SXRAT" (Cinterion specific)

[Norbert van Bolhuis]

Hi Aleksander,

Thanks for your answer!

I'm not sure whether the COPS based logic works because we
want to set 3G/2G (or 4G/2G) Radio Access Technology.
This doesn't seem to be supported by the COPS command,
it does NOT allow RAT combinations.

SXRAT is the only way. I'm willing to do the Cinterion plugin
upgrade if you guide me a little. I do not know any nice way
of guaranteeing SXRAT is done after COPS, or to put it in
other words: how to make make sure the COPS command does NOT
overrule SXRAT?

I don't think a COPS=0 command overrules any previously COPS-selected
RAT (if I read the AT command manual correctly).

Btw. we're using ModemManager 1.14.0, do you think we seriously benefit
from a couple of recent Cinterion fixes, I'm talking about these ones:
35ecd45b66ff46e24ee99c199cbfc37702796cdd, cinterion: load initial EPS 
bearer cid only once
eb6ec1913f1403e7081f510d3e01e076fcfb9ddd, cinterion: fallback to RF on 
on error right away
e933fe14130b20785b6ddd2993a8fc982976c7af, cinterion: increase SWWAN 
connection attempt timeout

Thanks!

Regards,
Norbert


On 2/24/21 3:10 PM, Aleksander Morgado wrote:
> Hey Norbert,
> 
> Giacinto, added you in CC, in case you have some suggestion.
> 
>>
>> We're using a Cinterion ELS61-E R2 and seem to suffer from a lot of
>> "packet data disconnects" and cell/rat/MO switching.
>> We're advised to force the modem to use 3G/2G (or 4G/2G) Radio Access
>> Technology with the AT^SXRAT command.
>> We've been told the "AT+COPS=0" may reset SXRAT settings.
>>
>> I've tried to do this via:
>> mmcli -m 0 --set-allowed-modes='2g|4g' --set-preferred-mode='4g'
>>
>> but it doesn't work and even if it would, I'm not sure this means the
>> "AT^SXRAT" command alwaysf ollows "AT+COPS=0" nicely.
>>
>> I see no "AT^SXRAT" in the source code, so I guess "AT^SXRAT" is a
>> Cinterion specific command that isn't supported yet.
>>
>> I do like to use the "AT^SXRAT" command.
>>
>> So I'd like to do a "AT^SXRAT" after each "AT+COPS=0". This involves
>> changing modem_3gpp_register_in_network, is this the right thing to do?
>>
>> If not, how to best use the "AT^SXRAT" command?
>>
> 
> The Cinterion plugin currently uses AT+COPS also to configure access
> technology; e.g. if 4G-only is requested, we would run AT+COPS=,,,7
> 
> Does this COPS based logic to configure access tech not work in the
> ELS61? Is ^SXRAT the only way to do that in the ELS61? If ^SXRAT is
> the only way to do it, we could upgrade the Cinterion plugin to use
> it. But I'm not sure that sending the SXRAT after each COPS would make
> much sense; is there no other way to do that?
> 
> Also, if COPS=0 resets the desired access tech, I wonder if the same
> is currently happening with our already available COPS based access
> tech selection logic.
> 
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