Meaning of AT%XMONITOR reported PSM values?

[tedhavelka]

Hello Devzone,

I am building firmware for an nRF9160 based device, starting with an ncs 1.6.1 sample app and LTE modem firmware v1.3.1.  I'm in North America, and when testing LTE-M celular connection I can typically find -- or the modem finds -- two or three local celular network providers.

When I issue the AT command AT+CPSMS=1,,,"10101010","00110000", I find the modem remembers the values of this or my latest PSM settings request.  This is expected.  When I issue the querying command AT%XMONITOR, I see a report like either the first or second example here:

%XMONITOR: 5,"","","310260","352C",7,12,"014D3C15",87,5035,39,35,"","11100000","11100000","01001001"

%XMONITOR: 5,"AT&T","AT&T","310410","900C",7,12,"050B8210",391,5110,29,21,"","00110000","11100000","00110000"

In the first case, not one of my requested PSM values appears to be granted.  Am I reading this report correctly?  Are the three "one bits" in third from last and second from last quoted values the bit 8, 7 and 6 which are documented at Nordic Infocenter, command CPSMS and its 'set' syntax?

In the second report from %XMONITOR it appears that my requested active time value is granted by the network provider.  But what does it mean for active time to be granted, but Period-TAU value not to be granted?  How severely does this impact possible low power use of the nRF9160 in, for example, battery based devices?

- Ted

[tedhavelka]

Hello again Hakon,

I wish to update and clarify my issue regarding PSM settings requests and the nRF9160 LTE modem.  My supervisor has done some research and found celular coverage maps for our greater Portland, Oregon area.  In our metropolitan area we have solid coverage in LTE-M and NB-IoT network provision modes.

Question (1) - when an area has good LTE-M or NB-IoT type network service, does this mean that PSM is supported, or are these network modes separate and unrelated to where PSM is supported?

Here is a capture of the AT commands I issue, first ones to assure LTE modem is turned on:

s1 > at+cfun?
- DEV 0218 - found possible AT command.
modem reply: +CFUN: 0


s1 > at+cfun=1
- DEV 0218 - found possible AT command.
modem reply: 

s1 > at_ 
s1 > at+cfun?
- DEV 0218 - found possible AT command.
modem reply: +CFUN: 1


s1 > at+cpsms=1,,,"00100010","00000101"
- DEV 0218 - found possible AT command.
modem reply: 

s1 > at+cpsms?
- DEV 0218 - found possible AT command.
modem reply: +CPSMS: 1,,,"00100010","00000101"


s1 > at+cereg=5
- DEV 0218 - found possible AT command.
modem reply: 

s1 > at+cereg?
- DEV 0218 - found possible AT command.
modem reply: +CEREG: 5,5,"3558","02BDF917",7,,,"11100000","11100000"


s1 > at+cgdcont?
- DEV 0218 - found possible AT command.
modem reply: +CGDCONT: 0,"IP","globaldata.iot","10.165.91.12",0,0


s1 > at%xmonitor
- DEV 0218 - found possible AT command.
modem reply: %XMONITOR: 5,"","","310260","3558",7,12,"02BDF917",397,5035,41,40,"","11100000","11100000","01001001"


s1 > at%xsystemmode?
- DEV 0218 - found possible AT command.
modem reply: %XSYSTEMMODE: 1,1,0,1

Question (2) - from the above capture of queries via AT command handler, does the syntax for AT+CPSMS= look correct?

Both ways to query the modem for PSM settings -- +CEREG? and %XMONITOR -- report back values "11100000" for both periodic-TAU and requested Active Time settings.  Nordic's AT command documentation states that "111" setting of TAU and active time timer bits means the timers are disabled, in other words, PSM not supported.

Question (3) - from above AT command capture are we correctly querying our LTE modem to find out if PSM values were granted?

- Ted

[Achim Kraus]

Hi Ted,

I stumbled over similar questions here in Germany.

AFAIK, the answer is a complex mix of value the modem request, the network provider determines and the SIM-card provider preselects. Together with "roaming", that  makes it "very flexible" (selling people)  or "hardly deterministic" (making people). Sometimes I ask myself, if the mobile provider really wants to make business.

Hakon 

Thanks for the hint about the different units for the last value in %MONITOR. I was already struggling with 1h compared to 100h ("01001010").

Choosing different unit values then in CPSMS and the other fields of %MONITOR is in my opinion a not that good idea. Anyway, I guess, it's too late to fix it.