Mac based authentication

Dear all, I'm a new network administrator in one school. I've just installed hotspot using mikrotik and freeradius as radius server. I want to make mac address (client) as username and password for authentication. In this case, i want filtering mac address (calling-station-id) as username and password, so that client can authenticate directly. Please help me to configure freeradius so that i can implement that i explain before. Thanks's all Sanhenra