A method and apparatus are provided for transmitting a communication frame by a base station which comprises broadcasted information intended for a plurality of subscriber stations (AMSs), wherein that information is broadcasted by using more than one Modulation and Coding Scheme (MCS). The method comprises the steps of: a) receiving bandwidth requests' indications from the plurality of AMSs; b) based on these indications, identifying more than one decoding capabilities, wherein each of the identified decoding capabilities is associated with at least one of the plurality of AMSs; c) preparing a Bandwidth Request Acknowledgement Media Access Protocol Information Element (BR-ACK MAP-IE) message in response to the bandwidth requests' indications received; and d) transmitting a communication frame which comprises at least two copies of the BR-ACK MAP-IE message, wherein the number of the copies corresponds to the number of different decoding capabilities identified, and wherein each of the copies is transmitted at an MCS that corresponds to a respective decoding capability that has been identified.