Connecting to 5G

[Reinhard Speyerer]

On Fri, Jun 04, 2021 at 11:25:25AM +0100, Paul Gildea wrote:

Hi Paul,

> Hi,
> 
> I am currently trying to connect some 5G modems to a 5G network, Telit
> F980m and Cinterion MV31-W with libqmi 1.28.4. They are failing to connect.
> Perhaps the 5G signal is not great as a phone with the same sim can connect
> sometimes and not others (pr [perhaps it is that it is idling in LTE), but
> I'd like to make sure the modems are looking ok. I notice some
> irregularities in the output of commands, for the former modem I get:
> 
> Mode preference: umts, lte
> > Acquisition order preference: umts, lte, 5gnr
> 
> 
> For the Cinterion I get the opposite:
> 
> Mode preference: umts, lte, 5gnr
> > Acquisition order preference: lte, umts
> 
> 
> In each case 5gnr is missing from one of the outputs, is this usual?
> Output for Cinterion bands:
> 
> qmicli -p -d /dev/cdc-wdm2 --dms-get-band-capabilities
> > [/dev/cdc-wdm2] Device band capabilities retrieved:
> >         Bands: 'wcdma-2100, wcdma-pcs-1900, wcdma-dcs-1800, wcdma-1700-us,
> > wcdma
> > -850-us, wcdma-800, wcdma-900, wcdma-1700-japan, wcdma-850-japan'
> >         LTE bands: '1, 2, 3, 4, 5, 7, 8, 12, 13, 14, 17, 18, 19, 20, 25,
> > 26, 28,
> >  29, 30, 32, 34, 38, 39, 40, 41, 42'
> >         LTE bands (extended): '1, 2, 3, 4, 5, 7, 8, 12, 13, 14, 17, 18,
> > 19, 20,
> > 25, 26, 28, 29, 30, 32, 34, 38, 39, 40, 41, 42, 46, 48, 66, 71'
> 

to check for NR bands you would have to use qmicli -v and check for the
presence of TLV 0x13. This TLV was present for early Quectel RG500Q samples
but somehow "got lost" with later engineering firmware versions. It is now
back with current Quectel firmwares and also for MV31-W firmware version
T99W175.T41.1.0.0.8.GC.004  1  [Jan 25 2021 14:00:00]:

DMSGetBandCapabilities 7000
+OK DMSGetBandCapabilities 020400000000000108000000c00f00000610100800df380fbbe2a300001108000000000000000000123e001e0001000200030004000500070008000c000d000e00110012001300140019001a001c001d001e002000220026002700280029002a002e0030004200470013280013000100020003000500070008000c00140019001c002600280029003000420047004d004e004f00

> 
> Are there any other debugging/commands that will be useful when I am
> attempting to connect?

For the MV31-W this probably would be AT^DEBUG? and AT^CA_INFO? and perhaps
AT#MONI for the FN980m (if implemented by current firmware versions).

> For instance a network scan should show 5g networks, not just LTE?
> 

For 5G SA networks AT+COPS=? will return <AcT> = 11. In theory AT+COPS=?
should return <AcT> = 13 for 5G NSA networks which have the corresponding
SIB2 information on the BCH according to my understanding of TS 27.007
but in practice I have only seen <Act> = 7 being returned here.

I have intentionally deleted UMTS and LTE from mode preferences for 5G SA tests
so NASGetSystemSelectionPref on the MV31-W currently returns

+OK NASGetSystemSelectionPref 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

Despite AcquisitionOrder being set to LTE and UMTS only it registers to a
5G SA network:

AT^DEBUG?
mcc:001,mnc:01
nr_cell_id:19088641
nr_tac:100
nr_band:n78
nr_band_width:15.0MHz
nr_channel:632544
nr_pci:500
nr_rsrp:-79.0dBm
nr_rsrq:-11.0dB
nr_snr:21.0dB
OK
AT^CA_INFO?
NR5G serving information :
PCC info: Band is NR5G_N78, Band_width is 20.0 MHz
OK

The NR bandwidth in AT^DEBUG? is wrong and AT+CSQ returns 99,99 but the rest
basically works as expected for me. QMI results for comparison:

+OK NASGetSystemInfo 02040000000000130300000000140300000000270400010000002f0400000000004a03000200004b1d00010201020100010000ffff0000000000000000013030313031ff0000004c040003000000500300000064510100005201000153010000540200f401560400000000005704000000000058010000590100005a080000000000000000005c0400000000005d0400010000005e080001452301000000005f07000c3030313031ff
+OK NASGetSignalInfo 02040000000000170400b1ffe100180200f5ff
+OK NASGetRFInfo 02040000000000010600010c0d01e0a6110800010c0d01e0a60900120600010c12000000
+OK NASGetCellLocationInfo 020400000000002e0400e0a609002f160000f1100000640145230100000000f40192ffeafcd200

Regards,
Reinhard