SIM7000G does not register in 850MHz but does in 1800MHz (GSM/GPRS)

#1

Hello, my name is Bruno Bellini and I’m the R&D Hardware Manager at BQN (Montevideo, Uruguay).
We design and develop POS systems since 2003 and we always used SIMCOM modules (first SIM340, after that SIM900 and now we are using SIM7000G).
We are now producing around 1000 pcs of our POS product and we found some issues when trying to use the GPRS 850 MHZ band.
We are always using the module in GSM only mode, and with two different operators, one in 1800 MHz band (works fine) and other in 850 MHz band. In the last one, we are having problems to register to network (CREG always answers 0,2) or bringing up a wireless connection (CIICR answers ERROR if CREG succeeded and APN was set with CSTT). Sometimes the module connects but most of the times it fails.

I tried setting the band (CBAND command) and I found that there are only 3 modes available (EGSM_MODE, DCS_MODE and ALL_MODE). Also checking to CNBP command (Band preference), I noticed that if I set DCS_MODE, CNBP says that GSM_DCS_1800 is enabled, while if I set EGSM_MODE CNBP command shows GSM_EGSM_900 and GSM_PGSM_900 enabled. But it both modes the connection in 850MHz fails. If I configure to ALL_MODE it sometimes succeed, but more of the times not.

Does anyone know any way to configure to 850MHz (as for example the GSM850_PCS_MODE in the SIM900 module)? If I try the same sequence in SIM900 with GSM850_PCS_MODE set, it always registers and connects to network without problems.

It’s weird that documentation says its a Quad-Band module but it can not be configured in all bands separately.
I’m probably missing something important.

Waiting for your soon and kind reply.

Best regards,

#2

The modules should always be left in default band settings as it is set for auto registration on right band.

Use EGSM_MODE,ALL_BANDS for CBAND values for SIM900 or SIM800.
Check a fresh SIM7000G module setting with AT+CBAND? and use it for others too. You shouldnt change it as it will search automatically.
In case if you want to set it for that particular band, you can change it.
For SIM7000 modules check AT+CNMP command. You have to set it needed network to register for 2G or NBIOT or LTE M1.
For 2G its AT+CNMP=13

#3

Hi Ravi, thank you for your answer.
As I´m having problems with the auto registration for 850 MHz band is that I decided to set up manually the band.
For the SIM7000G module I´m already configuring CNMP=13 (for 2G only mode), but still not work well.
What confuses me is that the bands available to configure are DCS_MODE (1800MHz), EGSM_MODE (900MHz) or ALL_MODE (I guess it configures for 850 MHz and 1900 MHz also). There is no explicit band name for 850 MHz as it is for the SIM900.

Any clue?
I´m also asking to technical support of SIMCom, but answer can arrive in a couple of years.

Waiting for your kind help.

Best regards