A base station comprising a transmitter configured to transmit a downlink frame. The downlink frame comprises a resource allocation region, and the resource allocation region comprises a set of resource allocation messages comprising at least one resource allocation message. All or a subset of the resource allocation messages each comprise one or more fields with an indicator, interpreted from a particular field or a combination of some or all of the one or more fields, to indicate a number of resource allocation messages intended for a particular subscriber station in the resource allocation region.