What is the minimum value of TAU time?

Question

I send AT command: 
 AT+CPSMS=1,"","","10100010","00100001" Which means active PSM mode with TAU time = 2 minutes, RAT = 1 minutes. I receive: CEREG: 1,"61E6","090A8C15",9,,,"00011110","11100000" PSM parameter update: TAU: -1, Active time: 60 And recheck with AT%XMONITOR: XMONITOR: 1,"Viettel@","Viettel@","45204","61E6",9,3,"090A8C15",79,1769,39,26,"","00011110","11100000","00110100" 1.Seem that I only set TAU time >= 4 hours. Is it because of the local SIM provider? 2. Does "Keep alive time for MQTT" affect PSM time or RCC mode time between "Connected" and "Idle"? 3. In PSM mode, How to know when device in "active time" or idle? Does it relate to RCC mode? Development setup: Ubuntu, ncs v1.5.1, MQTT_Sample example, Thingy91.

Håkon Alseth · Accepted Answer

Hi, 
 
 1.Seem that I only set TAU time >= 4 hours. Is it because of the local SIM provider? 
 Most networks provides 60 minutes as the lowest in my area (Nordic countries), others have a minimum of 180 minutes. 
 This is different from network-to-network. 
 
 You can try experimenting with different timing, and see what is accepted or set as the lowest interval for your network, or you can contact the network and ask what their configuration is. 
 2. Does "Keep alive time for MQTT" affect PSM time or RCC mode time between "Connected" and "Idle"? 
 The keep alive sends a mqtt-ping, thus you go from idle -> connected (ie: you go out of PSM/eDRX). 
 You can set a PSM of 10 hours, but still do a mqtt-ping every 10 minutes. 
 3. In PSM mode, How to know when device in "active time" or idle? Does it relate to RCC mode? 
 Most networks have a set timed for RRC IDLE before entering PSM (or eDRX). This is a timing that you cannot change. In my network this is 60 seconds. 
 You can time this using the CSCON event. 
 
 Kind regards, 
 Håkon

What is the minimum value of TAU time?

Top Replies