Extract Huawei E3531 Firmware 21.318.15.00.143 on your computer
Install the Firmware update file for Huawei E3531 downloaded from Huaweiflashfiles.com
Follow the procedure for updating Firmware that is given in Package.

Huawei Flash File | Size: 15.59 MB
Version: 21.318.15.00.143
Operator:MTS Russia
Operating systems: Windows 7/8/10/XP/Vista
Huawei E3531 Firmware Download