The question as below reach me. I will quote myself.
Q: Please let me know the tips , to ensure connectivity all the time. I am loosing connectivity after 2/3 days , I need to manually reconnect by ringing the modem again as on now.
A: There are several sources for disconnect.
Chapter: AT commands and logic loops for set up a communication channel
The client (what means your IoT M2M device) has to take care on a connection to the cellular network.
Read more at my IoT M2M Cookbook.
Chapter: Supply voltage
“Some power supply concepts including LT Spice modules for DC/DC regulators and load generator for the 2 Ampere peak currents are a part of the book too. Be aware, that the power down reset is still the main fault in designs with cellular modules.”
Read more at my IoT M2M Cookbook.
Chapter: Examples for mistakes and errors during M2M development – Power down reset
Read more at my IoT M2M Cookbook.
Chapter: Testing your M2M device
12.1 TX power peaks by cellular module test mode
12.2 Pseudo load of 2 Ampere peak load with self-made function generator
12.2.1 Schematic diagram of the self-made function generator
12.2.2 Pseudo load with 2 Ampere peak by standard function generator
12.3 TX power peaks by GSM tester
12.4 Testing of the sensitivity
12.5 Testing of the radiated TX power
12.6 Where to get a cheap cellular tester?
Read more at my IoT M2M Cookbook.
My recommendation is to read the IoT M2M Cookbook and compare the recommendations with your design.