There are many occasions where you will not be able to find broadband internet connection. In these cases, you can use an internet modem with a 3G or 4G SIM and connect to the internet. There are different kinds of modems. Some modems need to be connected to the computer or laptop using USB. Once you connect the modem usually the software will prompt you to install the vendor provided software. You can also manually connect by opening the drive and install. Once installed the software will initialize and show the available SIM to connect. Click on Connect and get connected. You can also access the SMS and run USSD code. USSD codes are important to know the package and balance of the internet usage in the SIM.
You can also remove the SIM and insert into a phone to check the connectivity.
In Bangladesh, you can get a modem from GP. Some of the brands are Dlink, Huawei, ZTE etc.
GP modems are less expensive and provide the best results.
Click on the below link to get more info on 4G modem and 4G router from GP