A broadcast system comprising: a plurality of base stations, each base station comprising: a receiver; a processor (2306, 2404); and a transmitter; wherein each base station is operable to: receive a content stream of service data units, SDUs; receive, from a MAC layer, information identifying a first transport stream convergence protocol, TSCP, PDU container size for the content stream; fragment and pack the SDUs to form TSCP protocol data units, PDUs, the TSCP PDUs being sized to fit the first TSCP PDU container size; encapsulate the TSCP PDUs to form MAC PDU data packets; receive a second content stream of second SDUs; receive, from the MAC layer, information identifying a second TSCP PDU container size for the second content stream, the first TSCP PDU container size and second TSCP PDU container size being different; fragment and pack the second SDUs to form second TSCP PDUs, the second TSCP PDUs being sized to fit the second TSCP PDU container size; encapsulate the second TSCP PDUs to form second MAC PDU data packets; and wherein each of the base stations transmits in a synchronized manner in a single frequency network an aggregate stream into which the MAC PDU data packets and the second MAC PDU data packets are interleaved. a plurality of base stations, each base station comprising: a receiver; a processor (2306, 2404); and a transmitter; a receiver; a processor (2306, 2404); and a transmitter; wherein each base station is operable to: receive a content stream of service data units, SDUs; receive, from a MAC layer, information identifying a first transport stream convergence protocol, TSCP, PDU container size for the content stream; fragment and pack the SDUs to form TSCP protocol data units, PDUs, the TSCP PDUs being sized to fit the first TSCP PDU container size; encapsulate the TSCP PDUs to form MAC PDU data packets; receive a second content stream of second SDUs; receive, from the MAC layer, information identifying a second TSCP PDU container size for the second content stream, the first TSCP PDU container size and second TSCP PDU container size being different; fragment and pack the second SDUs to form second TSCP PDUs, the second TSCP PDUs being sized to fit the second TSCP PDU container size; encapsulate the second TSCP PDUs to form second MAC PDU data packets; and receive a content stream of service data units, SDUs; receive, from a MAC layer, information identifying a first transport stream convergence protocol, TSCP, PDU container size for the content stream; fragment and pack the SDUs to form TSCP protocol data units, PDUs, the TSCP PDUs being sized to fit the first TSCP PDU container size; encapsulate the TSCP PDUs to form MAC PDU data packets; receive a second content stream of second SDUs; receive, from the MAC layer, information identifying a second TSCP PDU container size for the second content stream, the first TSCP PDU container size and second TSCP PDU container size being different; fragment and pack the second SDUs to form second TSCP PDUs, the second TSCP PDUs being sized to fit the second TSCP PDU container size; encapsulate the second TSCP PDUs to form second MAC PDU data packets; and wherein each of the base stations transmits in a synchronized manner in a single frequency network an aggregate stream into which the MAC PDU data packets and the second MAC PDU data packets are interleaved.