Selective inclusion of a Length Indicator field in an ARQ PDU

At least one ARQ protocol data unit (PDU) is formed from an ARQ service data unit (SDU). The ARQ PDU comprises a header portion and a data portion. If the PDU contains the last bit of an ARQ SDU, a length indicator field (LI) is added to the header portion. This means that LIs are not unnecessarily added to PDUs; hence header overhead is reduced, and there is more space for the PDU payload. An additional embodiment has a plurality of PDUs from different SDUs formed into one HARQ PDU. In that case, if the last PDU is found not to be carrying the last bit of an SDU, then the last PDU will not have an LI added to it, rather LIs will be added to all other ARQ PDUs even though they are not carrying the last bit of an ARQ SDU.