about cellular band selection: whole picture needed

RE: about cellular band selection: whole picture needed

Martin Lesund — Thu, 21 Mar 2019 11:11:41 GMT

Hi Kai,

Thank you for addressing this issue.

It has been handled internally and will be fixed in the next revision of the modem firmware.

(Released in the near future)

RE: about cellular band selection: whole picture needed

Martin Lesund — Tue, 19 Mar 2019 12:52:09 GMT

Hi Kai,
I've managed to reproduce the issue and we are investigating further the cause of this behavior.

Thank you for your patience

RE: about cellular band selection: whole picture needed

Kai — Sat, 16 Mar 2019 05:23:01 GMT

hi, Steven

The following is the corrected statement:

Permanent change can be made by command AT%XBANDLOCK=1,"0100" followed by AT+CFUN=0, then followed by a reboot.

After reboot:

AT%XCBAND
%XCBAND: 0
OK
AT%XCBAND=?
%XCBAND: (3)
OK

As expected, band-3 has been locked in, and the modem hasn't started.

AT+CFUN?
...
AT+CFUN?
...

Lots of stuff happens, meaning the modem has started. Then,

AT%XCBAND=?
%XCBAND: (3)
OK
AT%XCBAND
%XCBAND: 13
OK

Band-3 is still locked in, I expected the current band is 3, but it is 13.

Then:

I did similar experiment to lock in band-20 only. The result is: the current band is 13.

I did similar experiment to lock in band-4 only. The result is: the current band is 0.

Best,

Kai

RE: about cellular band selection: whole picture needed

stevenminnick — Fri, 15 Mar 2019 15:18:37 GMT

Kai,

I think you have it backwards when you said:

AT%XCBAND=?
%XCBAND: (3)
OK

As expected, band-3 has been locked out, and the modem hasn't been started.

I believe the response to

AT%XCBAND=?

Is the list of bands it can support. The AT command document says that XCBAND returns a list of supported bands. I thought I remember seeing that out of the box this chip supports bands 3, 4, 13, and 20 and on mine when I did that I get:

AT%XCBAND=?
%XCBAND: (3,4,13,20)
OK

Well the AT command document for %XBANDLOCK doesn't specifically say if a 0 or 1 locks out or locks in those bands. Assuming the XCBAND command is right and it appears it is, then 0's in the BANDLOCK command locks out and 1 means locks in (or is supported).

I'm confused too. The document isn't specific in it's language in the BANDLOCK section. But when you run it, and check with XCBAND it appears that way.

And based on my testing above, you can lock out or in any band and it uses whatever it wants anyway.

I've done:

AT%XBANDLOCK=2,"1000000000000"
OK
AT%XCBAND=?
%XCBAND: (13)
OK

AT+CFUN?

(then lots of stuff happens)

AT%XCBAND
%XCBAND: 13
OK

And then I did

AT%XBANDLOCK=2,"00000000000000001100"
OK
AT%XCBAND=?
%XCBAND: (3,4)
OK

(then lots of stuff happens)

AT%XCBAND
%XCBAND: 13
OK

So I'm confused too. Or I might have stumbled into a bug.

RE: about cellular band selection: whole picture needed

Kai — Thu, 14 Mar 2019 01:45:00 GMT

Hi Martin

Permanent change can be made by command AT%XBANDLOCK=1,"0100" followed by AT+CFUN=0, then followed by a reboot.

After reboot:

AT%XCBAND
%XCBAND: 0
OK
AT%XCBAND=?
%XCBAND: (3)
OK

As expected, band-3 has been locked out, and the modem hasn't been started.

AT+CFUN?
...
AT+CFUN?
...

Lots of stuff happens.

AT%XCBAND=?
%XCBAND: (3)
OK
AT%XCBAND
%XCBAND: 13
OK

Band-3 is still locked out, however band-13 is the current one.

I did similar experiment to lock out band-20 only. The result is: band-13 is the current one.

I did similar experiment to lock out band-4 only. The result is: the current band is 0.

Pretty confused..

Best,

Kai

RE: about cellular band selection: whole picture needed

stevenminnick — Wed, 13 Mar 2019 18:59:30 GMT

Had a follow up question. Every time I have connected I am on channel 13. Verizon, USA in my area.

Using the AT client code. Powered up the board. Link Monitor and did a board reset.

AT%XCBAND
%XCBAND: 0
OK

So that means it's not connected (or still powered off).

AT%XCBAND=?
%XCBAND: (3,4,13,20)
OK

This should be the list of bands it supports.

AT%XBANDLOCK=2,"10000001000000000000"
OK
AT%XCBAND=?
%XCBAND: (13,20)
OK
AT%XBANDLOCK=2,"00000000000000001100"
OK
AT%XCBAND=?
%XCBAND: (3,4)
OK

This all looks normal. (yes I know in the second XBANDLOCK I can leave off the leading 0's). But then if I power on the radio I think that means it will only use bands 3 and 4. Yes?

AT+CFUN=1
OK
AT%XCBAND=?
%XCBAND: (3,4)
OK

AT+CFUN?

(then lots of stuff happens)

Takes a long time to connect, longer than normal. I expected not to have a connection at all, but then it did connect and then:

AT%XCBAND
%XCBAND: 13
OK

I thought I locked out band 13.

AT%XCBAND=?
%XCBAND: (3,4)
OK

Does it try the bands we specify and then when it fails on that does it go against the lockout and try them all just to make sure it's connected?

RE: about cellular band selection: whole picture needed

Martin Lesund — Wed, 13 Mar 2019 08:33:47 GMT

Hi Kai,

Q1. These are defined in the modem firmware which is stored in the modem side of the SIP.

So when more bands are getting certified then you will be able to update your modem firmware to support the new bands.

Q2. The modem will try to search through the different bands and will use the first one that is available.

Q3. If you are using the Bandlock command you need to set this before activating the modem (AT+CFUN=1). And the permanent mask is written to (modem) flash if you power off the modem with AT+CFUN=0.

Best Regards,

Martin L.