A transmitting unit for use in sending data in packets in timeslots within
time frames, each packet being sent in a timeslot, the unit comprising
means to reserve for uplink transmission in the next uplink time frame a
number of timeslots (X), the number of timeslots (X) being determined
dependent upon a value which is the number of timeslots (Y) used for
uplink transmission in the previous uplink time frame plus the number of
packets (Z) remaining for uplink transmission during the last time frame
minus the number of time slots (Q) to be used in the present uplink time
frame.