A communications network includes optical network terminations (ONTs) and
an optical line termination (OLT) connected to a passive optical network
(PON). The OLT measures round trip transmission delay expressed in time
slot duration for each of the ONTs, and orders the ONTs in ascending order
of respective delay modulo time slot duration. A desired reception time at
the OLT is scheduled for each of the OLTs according to the ascending order
and each ONT is commanded to transmit at a command time that leads the
respective desired reception time by a respective delay integral time slot
duration. The scheduling includes leaving a reception interval spare after
the last ONT in ascending order. The ascending delay modulo slot protocol
becomes more efficient as the number of time slots per frame increases. If
the number of time slots per frame is N, then the efficiency of the
protocol is (N-1)/N. Unassigned time required per transmission frame is
thereby reduced.
