SIM800L MQTT over TCP getting timeout?!

Hello guys, I need a little help about SIM800L and TCP connection with MQTT packets. My product have Over-The-Air updates (OTA) over WiFi and I need to do with GSM.

I create MQTT SUBSCRIBE packet and send to server and read all bytes received (binary of microcontroller), however, after ~180 seconds, connection is closed or something that I dont know.

I trying to download 890KB binary file over MQTT, but ever fail in ~180seg, I think about TCP timeout or broker timeout (Mosquitto), but I really dont know.

Any one can help me?! I already test with PPPoS and the same problem persist (180seg download are stopped)

With PPPoS, I changed MQTT timeout from client library and worked!