Retrieving SNR/SINR values for 3G connections.

[Paul Gildea]

I want to query a modem (MC7455) and find out the SNR values periodically.
I've noticed that this information is only available while on LTE?

*3G: *

[root at trx-r2 /]# qmicli -p -d /dev/cdc-wdm0 --nas-get-signal-strength

[/dev/cdc-wdm0] Successfully got signal strength

Current:

        Network 'umts': '-80 dBm'

Other:

        Network 'cdma-1xevdo': '-125 dBm'

RSSI:

        Network 'umts': '-80 dBm'

        Network 'cdma-1xevdo': '-125 dBm'

ECIO:

        Network 'umts': '-7.0 dBm'

        Network 'cdma-1xevdo': '-2.5 dBm'

IO: '-106 dBm'

SINR (8): '9.0 dB'



*LTE:*

[/dev/cdc-wdm0] Successfully got signal strength
Current:
Network 'lte': '-71 dBm'
RSSI:
Network 'lte': '-71 dBm'
ECIO:
Network 'lte': '-2.5 dBm'
IO: '-106 dBm'
SINR (8): '9.0 dB'
RSRQ:
Network 'lte': '-14 dB'
*SNR:*
* Network 'lte': '1.4 dB'*
RSRP:
Network 'lte': '-102 dBm'
[root at trx-r6 /]#



To that end I noticed that both connections report SINR.  However the value
is always static (*SINR (8): '9.0 dB'*), is this a placeholder or does it
vary?

If I try AT commands it reports SINR and it varies as expected (but not
similar to the value reported with  libqmi) but again, only shown on an LTE
connection:


*LTE:*

at!gstatus?
!GSTATUS:
Current Time:  218 Temperature: 39
Reset Counter: 2 Mode:        ONLINE
System mode:   LTE         PS state:    Attached
LTE band:      B20     LTE bw:      10 MHz
LTE Rx chan:   6300 LTE Tx chan: 24300
LTE CA state:  INACTIVE     LTE Scell band:B3
LTE Scell bw:20 MHz   LTE Scell chan:1700
EMM state:     Registered     Normal Service
RRC state:     RRC Connected
IMS reg state: No Srv

PCC RxM RSSI:  -69 RSRP (dBm):  -101
PCC RxD RSSI:  -73 RSRP (dBm):  -105
SCC RxM RSSI:  -87 RSRP (dBm):  -112
SCC RxD RSSI:  -89 RSRP (dBm):  -112
Tx Power:      0 TAC:         0514 (1300)
RSRQ (dB):     -15.0 Cell ID:     00017A07 (96775)
*SINR (dB):     -2.6*

*3G:*

at!gstatus?

!GSTATUS:

Current Time:  2636             Temperature: 42

Bootup Time:   5                Mode:        ONLINE

System mode:   WCDMA            PS state:    Attached

WCDMA band:    WCDMA 2100

WCDMA channel: 10837

GMM (PS) state:Requesting srvc  NORMAL SERVICE

MM (CS) state: IDLE             NORMAL SERVICE



WCDMA L1 state:L1M_DCH          LAC:         8CA2 (36002)

RRC state:   CELL_DCH           Cell ID:     000BD119 (774425)

RxM RSSI C0:   -74              RxD RSSI C0: -94

RxM RSSI C1:   -106             RxD RSSI C1: -106





OK


Is it possible to get SNR/SINR for non-LTE connections? Are they not
valuable metrics for some reason? It doesn't seem to be possible, even from
reading the AT command set, but thought I would check.

Thanks,

--
Paul
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