How do I check whether my GSM Modem works in some other country?
It probably depends on a lot of factors other than mere frequency band compatibility only. If your wireless carrier allows roaming to that country. If your device is unlocked. If the carrier in Qatar allows you access to their networks. Not all networks share the same frequencies in any given band. They are usually allocated blocks of frequencies exclusively for their usage and another carrier allocated another block to avoid interference. They might also use different signaling protocols and so on. Different parts of the world use different band combinations... If that weren't confusing enough. You can contact your cell carrier or modem manufacturer to check device compatibility.