For a packet, a communication device determines (12) a length of a packet length field based on one or more of the following: a size of a transmit region allocated for a remote unit, a size of a transmit region allocated for a remote unit and not to be used for at least one other packet, and/or whether the packet length of the packet is indicated by a history of packet lengths of previously transmitted packets. The communication device may also or alternatively determine (22) a length of a connection identifier field based on a number of connection identifiers previously established. The communication device then transmits (13, 23) the packet, which includes the field(s) of determined length. By determining the lengths of these fields in this manner, the fields may be made shorter and their use may potentially reduce signaling overhead as compared to using the present-day fixed-length fields.