I get the registration "parse_cereg: LTE mode not found, error code: -22" error,when try to connect to LTE network in china shenzhen.the hardware is custom use nrf9160 chip.can anyone help analysis the error?why Network registration status is 4,what does it mean.and what is "fallback network mode"?thanks.
[00:00:00.667,083] <inf> main: Connecting to LTE...
[00:00:00.687,683] <dbg> lte_lc: init_and_config: System mode (4) and preference (0) configured
[00:00:00.700,347] <inf> main: Requesting EDRX mode
[00:01:13.940,887] <dbg> lte_lc: at_handler_cereg: +CEREG notification: +CEREG: 4
[00:01:13.949,432] <dbg> lte_lc_helpers: parse_cereg: Network registration status: 4
[00:01:13.957,946] <dbg> lte_lc_helpers: parse_cereg: LTE mode not found, error code: -22
[00:01:13.966,949] <dbg> lte_lc_helpers: event_handler_list_dispatch: Dispatching events:
[00:01:13.975,860] <dbg> lte_lc_helpers: event_handler_list_dispatch: - handler=0x00017A0D
[00:01:13.985,015] <dbg> lte_lc_helpers: event_handler_list_dispatch: - handler=0x0000BC71
[00:01:13.994,140] <inf> main: ************************************* LTE event: 0
[00:01:14.002,380] <dbg> lte_lc_helpers: event_handler_list_dispatch: Done
[00:01:14.009,948] <dbg> lte_lc_helpers: event_handler_list_dispatch: Dispatching events:
[00:01:14.018,890] <dbg> lte_lc_helpers: event_handler_list_dispatch: - handler=0x00017A0D
[00:01:14.028,015] <dbg> lte_lc_helpers: event_handler_list_dispatch: - handler=0x0000BC71
[00:01:14.037,139] <inf> main: ************************************* LTE event: 4
[00:01:14.045,410] <dbg> lte_lc_helpers: event_handler_list_dispatch: Done
[00:10:00.757,781] <inf> lte_lc: Network connection attempt timed out
[00:10:00.772,735] <dbg> lte_lc: at_handler_cereg: +CEREG notification: +CEREG: 0
[00:10:00.781,311] <dbg> lte_lc_helpers: parse_cereg: Network registration status: 0
[00:10:00.789,825] <dbg> lte_lc_helpers: parse_cereg: LTE mode not found, error code: -22
[00:10:00.798,797] <dbg> lte_lc_helpers: event_handler_list_dispatch: Dispatching events:
[00:10:00.807,739] <dbg> lte_lc_helpers: event_handler_list_dispatch: - handler=0x00017A0D
[00:10:00.816,864] <dbg> lte_lc_helpers: event_handler_list_dispatch: - handler=0x0000BC71
[00:10:00.825,988] <inf> main: ************************************* LTE event: 0
[00:10:00.834,197] <dbg> lte_lc_helpers: event_handler_list_dispatch: Done
[00:10:00.841,888] <inf> lte_lc: Using fallback network mode
[00:11:21.896,820] <dbg> lte_lc: at_handler_cereg: +CEREG notification: +CEREG: 2,"7879","078D412A",9
[00:11:21.907,226] <dbg> lte_lc_helpers: parse_cereg: Network registration status: 2
[00:11:21.915,771] <dbg> lte_lc_helpers: parse_cereg: LTE mode: 9
[00:11:21.922,637] <dbg> lte_lc_helpers: event_handler_list_dispatch: Dispatching events:
[00:11:21.931,610] <dbg> lte_lc_helpers: event_handler_list_dispatch: - handler=0x00017A0D
[00:11:21.941,253] <dbg> lte_lc_helpers: event_handler_list_dispatch: - handler=0x0000BC71
[00:11:21.950,378] <inf> main: ************************************* LTE event: 0
[00:11:21.958,618] <dbg> lte_lc_helpers: event_handler_list_dispatch: Done
[00:11:21.966,217] <dbg> lte_lc_helpers: event_handler_list_dispatch: Dispatching events:
[00:11:21.975,158] <dbg> lte_lc_helpers: event_handler_list_dispatch: - handler=0x00017A0D
[00:11:21.984,313] <dbg> lte_lc_helpers: event_handler_list_dispatch: - handler=0x0000BC71
[00:11:21.993,438] <inf> main: ************************************* LTE event: 4
[00:11:22.001,678] <dbg> lte_lc_helpers: event_handler_list_dispatch: Done
[00:11:22.009,277] <dbg> lte_lc_helpers: event_handler_list_dispatch: Dispatching events:
[00:11:22.018,218] <dbg> lte_lc_helpers: event_handler_list_dispatch: - handler=0x00017A0D
[00:11:22.027,343] <dbg> lte_lc_helpers: event_handler_list_dispatch: - handler=0x0000BC71
[00:11:22.036,499] <inf> main: ************************************* LTE event: 5
[00:11:22.044,738] <dbg> lte_lc_helpers: event_handler_list_dispatch: Done
