Communicative services are transported over a TDMA or TDM access network by packetising the services into minicells which minicells are transported within minislots created by subdivision of the TDM time slots. For low bit rate communicative services only, mini-slots are allocated periodically rather than in the blocks that are allocated to high bit rate services. The packetisation delay inherent within the transport layer can be significantly reduced for these low bit rate services.